RECIPROCATING IMPACT HAMMER

Abstract

An impact hammer for breaking a working surface, the hammer including a drive mechanism and a housing with an inner containment surface and a reciprocating hammer weight. A reciprocation cycle of the hammer weight includes an upstroke and a down-stroke, the hammer weight respectively moving upwards and downwards. On the down-stroke the hammer weight impacts a striker pin with a driven end and a working surface impact end. A vacuum chamber in the housing is formed by the containment surface, upper vacuum sealing coupled to the hammer weight and lower vacuum sealing. The hammer weight is driven toward the striker pin by the pressure differential between atmosphere and the vacuum chamber formed on the upstroke. A down-stroke vent permits fluid egress from the vacuum chamber on the down-stroke.

Claims

1. An impact hammer for breaking a working surface, the impact hammer comprising: a housing with at least one inner side wall forming at least part of a containment surface; a drive mechanism; a reciprocating hammer weight, at least partially located within the housing, with the reciprocating hammer weight capable of reciprocating along a reciprocation axis, wherein a reciprocation cycle of the reciprocating hammer weight, when the reciprocation axis is on an approximately vertical axis, comprises: a) an up-stroke, during which the drive mechanism moves the reciprocating hammer weight upwards along the reciprocation axis; and b) a down-stroke, during which the reciprocating hammer weight moves downwards along the reciprocation axis; a striker pin having a driven end and a working surface impact end, the striker pin located within the housing such that the working surface impact end protrudes from the housing; a shock-absorber coupled to the striker pin; and a variable volume vacuum chamber comprising: a) at least a portion of the containment surface; b) at least one upper vacuum sealing coupled to the reciprocating hammer weight; c) at least one lower vacuum sealing; and at least one down-stroke vent, operable to permit fluid egress from the variable volume vacuum chamber during at least part of the down-stroke; wherein the variable volume vacuum chamber is configured to have a sub-atmospheric pressure during at least part of the up-stroke such that the reciprocating hammer weight is driven toward the striker pin by a pressure differential between an atmosphere and the sub-atmospheric pressure during the down-stroke, and wherein said at least one upper vacuum sealing comprises one or more seals, said one or more seals comprising: an exterior first layer, formed with a first layer exterior surface configured and oriented to come into at least partial sliding contact with the containment surface during a reciprocating movement of the reciprocating hammer weight, and an interior second layer, located between the exterior first layer and the reciprocating hammer weight, the interior second layer at least partially formed from a shock-absorbing material.

2. The impact hammer of claim 1, further comprising a preload, biasing the exterior first layer into contact with the containment surface.

3. The impact hammer of claim 2, wherein the interior second layer forms said preload.

4. The impact hammer of claim 1, wherein said first layer and said second layer collectively form a composite cushioning slide, the composite cushioning slide fitted to an exterior surface of the reciprocating hammer weight.

5. The impact hammer of claim 1, wherein at least one upper vacuum sealing is coupled to said reciprocating hammer weight by at least partial retention in a recess in the hammer weight.

6. The impact hammer as claimed in claim 1, wherein the upper vacuum sealing forms at least one substantially uninterrupted sealing laterally encompassing the hammer weight.

7. The impact hammer of claim 1, wherein the at least one down-stroke vent is operable to at least restrict fluid ingress into the variable volume vacuum chamber during at least part of the up-stroke.

8. The impact hammer of claim 1, wherein the at least one down-stroke vent comprises at least one aperture in the containment surface.

9. The impact hammer of claim 1, wherein the at least one down-stroke vent is formed in the containment surface.

10. The impact hammer of claim 1, further comprising multiple down-stroke vents, comprising at least one formed down-stroke vent formed in at least two of: (a) the containment surface, (b) the at least one lower vacuum sealing; (c) the reciprocating hammer weight, and (d) the at least one upper vacuum sealing.

11. The impact hammer of claim 1, wherein the at least one down-stroke vent comprises a valve.

12. The impact hammer of claim 1, wherein the reciprocating hammer weight impacts directly on the driven end of the striker pin during at least a part of the down-stroke.

13. The impact hammer as claimed in claim 1, comprising a nose block formed from a portion of the housing and at least partially enclosing the striker pin and comprising nose block elements comprising: a cap plate; a upper shock absorbing assembly; a retainer; a lower shock absorbing assembly; a nose cone; positioned substantially about the striker pin between the striker pin driven end and the impact end in the preceding sequence with respect to the impact axis, and wherein the lower vacuum sealing comprises one or more seals located in the nose block.

14. The impact hammer of claim 13, wherein the one or more seals in the nose block are located between at least one of the: cap plate and the striker pin; upper shock absorbing assembly and the striker pin; retainer and the striker pin; retainer and a nose block inner side wall; lower shock absorbing assembly and the striker pin; nose cone and the striker pin.

15. The impact hammer of claim 13, wherein the at least one lower vacuum sealing comprises one or more seals formed as individual independent layers laterally encircling the striker pin.

16. The impact hammer of claim 14, wherein the lower vacuum sealing comprises seals located in at least one said shock absorbing assembly.

17. The impact hammer of claim 16, wherein the shock-absorbers are coupled to the striker pin by the retainer, the retainer being interposed between the shock-absorbing assemblies, wherein at least the lower shock-absorbing assembly is formed from a plurality of un-bonded layers including at least two elastic layers interleaved by an inelastic layer, wherein the lower vacuum sealing comprises one or more seals located in the lower shock absorbing assembly between a said elastic layer and the striker pin.

18. The impact hammer of claim 1, wherein the variable volume vacuum chamber forms an atmospheric up-stroke brake applying the pressure differential to a movement of the reciprocating hammer weight over an un-driven portion of the up-stroke to decelerate the reciprocating hammer weight up-stroke movement.

19. The impact hammer of claim 1, wherein the reciprocating hammer weight comprises: a lower impact face, at least a portion of the lower impact face forming a vacuum piston face, wherein the vacuum piston face is movable along a path parallel to, or co-axial to, the reciprocation path and the vacuum piston face comprises a hammer weight impact surface for impacting the driven end of the striker pin during at least a part of the down-stroke; an upper face; and at least one side face, wherein at least a portion of an upper face of the reciprocating hammer weight is open to the atmosphere.

20. A method of operating an impact hammer having a) a drive mechanism, b) a housing, c) a variable volume vacuum chamber, d) a reciprocating hammer weight, at least partially located within the housing and capable of reciprocating along a reciprocation axis, e) a striker pin having a striker pin longitudinal axis extending between a driven end of the striker pin and a working surface impact end of the striker pin, f) a nose block formed from a portion of the housing and positioned substantially about the striker pin between the driven end and the working surface impact end with respect to an impact axis that is coaxial or parallel to the reciprocation axis, wherein a said at least one upper vacuum sealing comprises: an exterior first layer, formed with a first layer exterior surface configured and oriented to come into at least partial sliding contact with the containment surface during a reciprocating movement of the reciprocating hammer weight, and an interior second layer, located between the exterior first layer and the reciprocating hammer weight, the interior second layer at least partially formed from a shock-absorbing material, a preload, biasing the exterior first layer into contact with the containment surface, and wherein the striker pin is located within the housing such that the working surface impact end protrudes from the housing and wherein the striker pin is positioned to move substantially along a linear impact axis that is coaxial or parallel to the striker pin longitudinal axis and coaxial or parallel to the reciprocation axis, the method comprising: a) contacting the working surface impact end of the striker pin to a working surface to be broken; b) operating the drive mechanism to begin lifting the reciprocating hammer weight such that a volume of the variable volume vacuum chamber increases and a pressure differential between an atmosphere and the variable volume vacuum chamber is created; c) causing an up-stroke stage, in which the reciprocating hammer weight is moved along the reciprocation axis for a distance equal to a hammer weight up-stroke length from a lower start initial position with a minimum hammer weight potential energy to an upper position at an upper distal end of the housing with a maximum hammer weight potential energy; d) causing an upper stroke transition, in which hammer weight movement halts before reversing direction along the reciprocation axis; e) releasing the reciprocating hammer weight, wherein the pressure differential acting on the reciprocating hammer weight drives the reciprocating hammer weight toward the driven end of the striker pin, and wherein the reciprocating hammer weight moves back along the reciprocation axis for a distance equal to a hammer weight down-stroke length from the upper position to the lower start initial position; f) transmitting an impact force from the striker pin to the working surface to be broken; and g) repeating steps a) through f).

Description

BRIEF DESCRIPTION OF DRAWINGS

[0551] Further aspects and advantages of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

[0552] FIG. 1 shows a preferred embodiment of the present invention of an apparatus in the form of an impact hammer attached to an excavator;

[0553] FIG. 2a shows an enlarged view of a side elevation section of the impact hammer shown in FIG. 1 with the hammer weight at the bottom of the down-stroke;

[0554] FIG. 2b shows a side elevation section of the impact hammer shown in FIG. 2a with the hammer weight at the top of the up-stroke;

[0555] FIG. 3 shows an enlarged side elevation view of a cross-section of the lower end of the impact hammer shown in FIG. 2;

[0556] FIG. 4a shows an enlarged view of a side elevation section of a seal and cushioning slides according to a preferred embodiment;

[0557] FIG. 4b shows an enlarged view of a side elevation section of a combined seal and cushioning slide according to a preferred embodiment;

[0558] FIG. 4c shows a side elevation section view of a weight, cushioning slides and seal;

[0559] FIG. 4d shows a plan view of section XX of the weight, cushioning slides and seal in FIG. 4c;

[0560] FIG. 4e shows a plan view of section YY of the weight, cushioning slides and seal in FIG. 4c;

[0561] FIG. 4f shows a plan section view of an alternative weight, cushioning slides and seal;

[0562] FIG. 4q shows a lower plan section view of the weight, cushioning slides and seal shown in FIG. 4f;

[0563] FIG. 4h shows a side elevation view of the striker pin and nose block with an intermediary element;

[0564] FIG. 4i shows an enlarged side elevation of the intermediary element shown in FIG. 4f;

[0565] FIG. 4j shows a side view of a further embodiment including a further intermediary element;

[0566] FIG. 4k shows an enlarged side elevation of the intermediary element shown in FIG. 4h;

[0567] FIG. 4L shows a side elevation section view of a weight and cushioning slides according to another embodiment;

[0568] FIG. 5a shows a side elevation section view of a vent and unidirectional flexible poppet valve;

[0569] FIG. 5b shows a side elevation section view of a vent and unidirectional rigid poppet valve;

[0570] FIG. 5c shows a side elevation section view of a vent and unidirectional side opening flap valve;

[0571] FIG. 6 shows a side elevation section view of a vent and vacuum pump;

[0572] FIG. 7 shows a side elevation section view of a vent, vacuum chamber and vacuum pump;

[0573] FIG. 8 shows an enlarged side elevation view of the striker pin and nose block with a lower vacuum sealing embodiment;

[0574] FIG. 9a shows a side elevation view of the striker pin and nose block with a further lower vacuum sealing embodiment;

[0575] FIG. 9b shows an enlarged side elevation view of lower vacuum sealing embodiment in FIG. 9a;

[0576] FIG. 10 shows an enlarged side elevation view of the striker pin and nose block with a further lower vacuum sealing embodiment;

[0577] FIG. 11 shows an enlarged side elevation view of the striker pin and nose block with a further lower vacuum sealing embodiment;

[0578] FIG. 12 shows an enlarged side elevation view of the striker pin and nose block with a further lower vacuum sealing embodiment;

[0579] FIG. 13 shows an enlarged side elevation view of the striker pin and nose block with a further lower vacuum sealing embodiment;

[0580] FIG. 14 shows a side elevation view of further embodiment of the present invention in the form of a robotic remote control impact hammer;

[0581] FIGS. 15a and 15b show respective side elevation section views of the impact hammer of FIG. 1, and of a prior art impact hammer;

[0582] FIG. 16 shows a side elevation section of a preferred embodiment of the present invention of an apparatus in the form of a small impact hammer attached to a small excavator;

[0583] FIG. 17 shows a side elevation section of further embodiment of the present invention of an apparatus in the form of a large impact hammer attached to a large excavator;

[0584] FIGS. 18a-d shows a perspective view of a hammer weight and cushioning slides according to the embodiment shown in FIG. 16;

[0585] FIG. 19 shows a perspective view of a weight and cushioning slides according to the embodiment shown in FIG. 17;

[0586] FIG. 20a shows an exploded enlarged plan section view of a weight and cushioning slides according to the embodiment shown in FIG. 17;

[0587] FIG. 20b shows an enlarged plan section view of a weight and cushioning slides shown in FIG. 20a;

[0588] FIG. 20c shows a plan section view of a weight and cushioning slides in FIG. 17;

[0589] FIG. 21 shows a perspective view of a weight according to the embodiment shown in FIG. 17 with a further embodiment of cushioning slides;

[0590] FIG. 22a shows a front elevation of the hammer weight and cushioning slides according to the embodiment shown in FIG. 16;

[0591] FIG. 22b shows a front elevation of an alternative hammer weight and cushioning slides to the embodiment shown in FIG. 22a;

[0592] FIG. 23a shows a front elevation of the hammer weight of the embodiment shown in FIG. 16 impacting a working surface;

[0593] FIG. 23b shows a side view of the embodiment shown in FIG. 23a;

[0594] FIG. 24 shows a front elevation of the hammer weight of the embodiment shown in FIG. 17;

[0595] FIG. 25a shows an isometric view of a cushioning slide for the hammer weight shown in FIG. 16;

[0596] FIG. 25b shows an isometric view of a cushioning slide for an apex of the weight shown in FIG. 17;

[0597] FIG. 25c shows an isometric view of a rectangular cushioning slide for the side wall of the weight shown in FIG. 17;

[0598] FIG. 25d shows an isometric view of a circular cushioning slide for the side wall of the weight shown in FIG. 17;

[0599] FIG. 26a shows a section view of the cushioning slide second layer along AA in FIG. 25a in uncompressed and compressed states;

[0600] FIG. 26b shows a section view of the cushioning slide second layer along BB in FIG. 25b in uncompressed and compressed states;

[0601] FIG. 26c shows a section view of the cushioning slide second layer along CC in FIG. 25c in uncompressed and compressed states;

[0602] FIG. 26d shows a section view of the cushioning slide second layer along DD in FIG. 25d in uncompressed and compressed states;

[0603] FIG. 27a shows an enlarged side section elevation of a peripheral portion of a cushioning slide with a first securing feature;

[0604] FIG. 27b shows an enlarged side section elevation of a peripheral portion of a cushioning slide with a second securing feature;

[0605] FIG. 27c shows an enlarged side section elevation of a peripheral portion of a cushioning slide with a third securing feature;

[0606] FIG. 27d shows an enlarged side section elevation of a peripheral portion of a cushioning slide with a fourth securing feature;

[0607] FIG. 27e shows an enlarged side section elevation of a peripheral portion of a cushioning slide with a fifth securing feature;

[0608] FIGS. 28a-f shows a partial plan section of the hammer weight of FIG. 16 with a sixth, seventh, eighth, ninth, tenth and eleventh securing features respectively;

[0609] FIG. 29a shows an enlarged exploded section view of a cushioning slide according to a further embodiment;

[0610] FIG. 29b shows an assembled view of the cushioning slide in FIG. 29a;

[0611] FIG. 30a shows an enlarged exploded plan section view of cushioning slides fitted to the weight of FIG. 17;

[0612] FIG. 30b shows an enlarged assembled view of the cushioning slides fitted to the weight of FIG. 30a;

[0613] FIG. 31 shows an isometric, part-exploded view of the weight of FIG. 17 with a further cushioning slide embodiment

[0614] FIG. 32 shows an enlarged exploded plan section view of cushioning slides incorporating pre-tensioning features fitted to the weight of FIG. 17;

[0615] FIG. 33a shows an enlarged plan section view of the weight and cushioning slides in FIG. 32 located inside the housing inner side walls, the cushioning slide having pre-tensioning features fitted;

[0616] FIG. 33b shows an enlarged plan section view of weight and cushioning slides in FIG. 33a, with a compressive force applied to the pre-tensioning features;

[0617] FIG. 34a shows an exploded diagram of a cushioning slide according to another embodiment of the present invention;

[0618] FIG. 34b shows an assembled diagram of the cushioning slide of FIG. 34a;

[0619] FIG. 35 shows a side elevation in section of a nose block assembly for a rock-breaking impact hammer in accordance with a preferred embodiment of the present invention;

[0620] FIG. 36 shows a plan section through the nose block assembly of FIG. 35;

[0621] FIG. 37 shows an exploded perspective view of the nose block assembly shown in FIGS. 35-36;

[0622] FIGS. 38A-B shows a schematic representation of the impact hammer before and after an effective strike;

[0623] FIG. 39A-B shows a schematic representation of the impact hammer before and after a mis-hit;

[0624] FIG. 40A-B shows a schematic representation of the impact hammer before and after an ineffective strike;

[0625] FIG. 41 shows a plan section through the nose block assembly of a rock-breaking impact hammer in accordance with a further preferred embodiment of the present invention;

[0626] FIG. 42 shows a plan section through the nose block assembly of FIG. 41;

[0627] FIG. 43 shows a side elevation in section of a nose assembly for a rock-breaking impact hammer in accordance with a further preferred embodiment of the present invention;

[0628] FIG. 44 shows a plan section through the nose block assembly of FIG. 43;

[0629] FIG. 45 shows a side elevation in section of a nose assembly for a rock-breaking impact hammer in accordance with a further preferred embodiment of the present invention;

[0630] FIG. 46 shows a plan section through the nose block assembly of FIG. 44;

[0631] FIG. 47 shows a side elevation in section of a nose assembly for a rock-breaking impact hammer in accordance with a further preferred embodiment of the present invention;

[0632] FIG. 48a shows a plan section through the nose block assembly of FIG. 47;

[0633] FIG. 48b shows an enlargement of section AA shown in the nose block assembly of FIG. 47 according to a further preferred embodiment of the present invention; and

[0634] FIG. 48c shows an enlargement of section AA shown in the nose block assembly of FIG. 47 according to a further preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0635] Reference numerals for the figures

TABLE-US-00001 (1)-Impact hammer (41)-annular membrane (2)-excavator (42)-void (3)-human operator (43)-down-stroke vent (4)-striker pin (44)-valve (5)-working surface (45)-vacuum pump (6)-housing (46)-vacuum tank (7)-excavator arm (47)-recess (striker pin) (8)-containment surface (48)-distal travel stop (9)-hammer weight (49)-proximal travel stop (10)-impact axis (50)-first (upper) shock absorbing assembly (11)-drive mechanism (51)-second (lower) shock absorbing assembly (12)-strop (52)-elastic layer (13)-upper face (hammer weight) (53)-inelastic layer (14)-sheave (54)-inner side wall (nose block) (15)-lower impact face (hammer weight) (55)-independent sealing layers (16)-side face (hammer weight) (56)-nose cone ring seals (17)-driven end (striker pin) (57)-annular recesses (nose cone) (18)-impact end (striker pin) (58)-integral elastic layer seal (19)-shock absorber (59)-distinct elastic layer seal (20)-nose block (60)-inelastic layer seal (21)-cap plate (61)-intimate fit seal (22)-vacuum chamber (62)-recoil plate ring seals (23)-vacuum piston face (63)-annular recesses (recoil plate) (24)-upper vacuum sealing (64)-flexible diaphragm (25)-lower vacuum sealing (65)-outer rim (26)-recoil plate (66)-static seal (27)-retaining pin (67)-maximum impact height (prior art) (28)-nose cone (68)-inclined drop height (prior art) (29)-attachment coupling (69)-maximum drop height (30)-cushioning slides seals (70)-inclined drop height (31)-in-weight seal (71)-tracked carrier (32)-V-shape protrusions (72)-azimuth cradle (33)-retention recess (73)-void-reduction foam (34)-biasing means (74)-intermediary layer peripheral rim portion (35)-fillets (75)-distinct elastic or inelastic layer seal (36)-pre-load (100)-prior art impact hammer (37)-vertex (200)-robotic tunnelling impact hammer (38)-intermediary element (1-101)-large impact hammer (39)-strap (1-102)-large excavator (40)-flexible seal (1-103)-weight (1-1)-impact hammer (1-104)-striker pin (1-2)-small excavator (1-109)-narrow side walls (1-3)-hammer weight (1-110)-upper distal face (1-4)-tool end (1-111)-lower distal face (1-5)-working surface (1-112)-linear impact axis (1-6)-housing (1-113)-cushioning slides (1-7)-housing inner side walls (1-114)-first layer (1-8)-wide side walls (1-115)-second layer (1-9)-narrow side walls (1-116)-exterior surface-first layer (1-10)-upper distal face (1-117)-outer surface-second layer (1-11)-lower distal face (1-118)-underside-first layer (1-12)-impact axis (1-119)-interior surface -second layer (1-13)-cushioning slides (1-120)-longitudinal apices (1-14)-first layer (1-121)-weight surface under second layer (1-15)-second layer (1-122)-displacement void (1-15a-d)-second layer (1-123)-securing feature (1-16)-exterior surface-first layer (1-124)-socket (1-17)-outer surface-second layer (1-125)-retention face (1-17a-d)-outer surface-second layer (1-126)-location projection (1-18)-underside-first layer (1-127)-locating recess (1-19)-interior surface -second layer (1-128)-aperture-second layer (1-19a-d)-interior surface -second layer (1-129)-aperture-first layer (1-20)-longitudinal apices (1-130)-locating portion (1-21)-weight surface under second layer (1-131)-tensioning features (1-22)-displacement void (1-213)-cushioning slide (1-22a-d)-displacement void (1-214)-first layer (1-23a-23e)-securing feature (1-215)-second layer (1-23f-23k)-securing feature (1-216)-first layer exterior surface (1-23m)-securing feature (1-217)-second layer outer surface (1-24)-socket (1-218)-first layer interior surface (1-25)-retention face (1-219)-second layer interior surface (1-26)-location projections (1-231)-upper sub-layer (1-27)-locating recesses (1-232)-intermediate sub-layer (1-28)-aperture-second layer (1-233)-lower sub-layer (1-29)-aperture-first layer (1-234)-lower sub-layer recess (1-30)-locating portion (1-235)-lower layer side walls (1-105)-working surface (2-20)-distal travel stops (1-106)-housing (2-21)-proximal travel stops (1-107)-housing inner side walls (2-22)-locating pins guide elements (1-108)-wide side walls (2-23)-outer periphery-elastic layer (2-1)-rock-breaking hammer (2-24)-inner periphery-elastic layer (2-2)-hammer weight (2-25)-null-point path/position (2-3)-housing (2-26)-tension band guide elements (2-4)-striker pin (2-27)-nose block side walls (2-5)-nose block (2-28)-indent-nose block walls (2-6)-attachment coupling ( (2-29)-anchor points (2-7a)-first shock absorbing assembly (2-30)-stabilizing features guide elements (2-7b)-second shock absorbing assembly (2-31)-tab portions (2-8)-retainer in the form of recoil plate (2-32)-lateral clearance (2-9)-upper cap plate (2-33)-restraining elements (2-10)-nose block bolts (2-34)-outer periphery-inelastic layer (2-11)-nose cone (2-35)-inner periphery-inelastic layer (2-12)-elastic layers/polyurethane (2-36)-outer periphery taper-inelastic layer (2-13)-inelastic layer-steel plate (2-37)-outer periphery taper-elastic layer (2-14)-retaining pins (2-100)-impact axis (2-15)-recess (2-16)-elongate slides guide elements (2-116)-elongate slides (2-17)-longitudinal projections (2-117)-longitudinal projection (2-18)-rock (2-19)-concave recess

[0636] FIGS. 1-15b show separate embodiments of the impact hammer provided as apparatus in the form of vacuum-assisted impact hammers (1). FIG. 1 shows an impact hammer (1) attached to a carrier in the form of an excavator (2), adjacent to a 1.8 m tall human operator (3) for scale purposes. The impact hammer (1) embodiment shown in FIG. 1 is configured with a striker pin (4) as the contact point with a working surface (5) for impacting and manipulation operations. The working surface (5) includes any surface, material or object subject to impacting, contact, manipulation and/or movement by the impact hammer (1), e.g. the working surface may be rock in a quarry. The striker pin (4) protrudes from a housing (6) which provides protection for vulnerable portions of the impact hammer (1), reduces debris ingress and provides attachment to the excavator (2) via the excavator's arm (7).

[0637] FIGS. 2a and 2b show an enlarged vertical section through the impact hammer (1) in FIG. 1. The housing (6) is configured as a substantially hollow elongate cylindrical column with an inner side wall in the form of a containment surface (8), enclosing a reciprocating component in the form of a hammer weight (9) movable along a reciprocation path, in the form of impact or reciprocation axis (10). A lifting and/or reciprocating mechanism in the form of drive mechanism (11, 12, 14) raises the hammer weight (9) along the impact axis (10) from a position of contact with the striker pin (4) (as shown in FIG. 2a) to the opposing maximum extent of the reciprocation path as shown in FIG. 2b. The drive mechanism is shown schematically and includes a linear drive provided in the form of a hydraulic ram (11) located to one side of the column (6). The ram (11) is connected to the hammer weight (9) via a flexible connector (12) that passes about a series of pulleys (14). The flexible connector (12) is a strop, belt or band attached to an upper face (13) of the hammer weight (9) after passing over a rotatable sheave (14a) located at the upper periphery (or adjacent the upper end) of the housing (6).

[0638] The pulley (14a) is formed as a sheave to limit lateral movement of the connector (12) along the rotation axis of the sheave (14a).

[0639] It will be appreciated that when the impact hammer (1) is orientated as shown in FIGS. 1 and 2 with its impact axis (10) vertically, the maximum extent of travel of the hammer weight (9) along the impact axis (10) (as shown in FIG. 2b) is also the maximum vertical height the weight (9) can reach.

[0640] To aid readability and clarity, the orientation of the impact hammer (1) and its constituents is referred to with respect to use of the impact hammer (1) operating with said hammer weight (9) moving along said impact axis (10) about a substantially vertical axis, and thereby denoting the descriptors ‘lower’ and ‘upper’ as comparatively referring to positions respectively closer and further vertically from the working surface (5). It will be appreciated however this orientation nomenclature is solely for explanatory purposes and does not in any way limit the apparatus to use in the vertical axis. The impact hammer (1) is able to operate in a wide range of orientations as discussed further subsequently.

[0641] In operation the drive mechanism (11) lifts the hammer weight (9) via the flexible strop (12). The hammer weight (9) is formed substantially cylindrically with a lower impact face (15) on the opposing side to said upper face (13), and a hammer weight side face (16).

[0642] The impact hammer (1) embodiment shown in FIGS. 1 and 2, is configured with the striker pin (4) having a driven end (17) and an impact end (18) with a longitudinal axis extending between the driven and impact ends (17, 18). The striker pin (4) is locatable in the housing (6) such that said impact end (18) protrudes from the housing (6).

[0643] The hammer weight (9) impacts on the driven end (17) of the striker pin (4) along the impact axis (10), substantially co-axial with the striker pin's (4) longitudinal axis.

[0644] A shock-absorber (19) is coupled to the striker pin (4) and both are retained in a lower portion of the housing (6), referred to herein as the “nose block” (20)

[0645] A variable volume vacuum chamber (22) is formed by: [0646] an upper vacuum sealing (24) located between the hammer weight (9) and the containment surface (8), the upper vacuum sealing encompassing/encircling the hammer weight (9); [0647] the lower impact face (15) of the hammer weight (9); [0648] the upper boundary (referred to herein as the “cap plate” (21)) of the nose block (20); [0649] the driven end (17) of the striker pin (4) protruding through the cap plate (21), and [0650] at least a portion of the containment surface (8), and

[0651] a lower vacuum sealing (25) more clearly discernible in FIGS. 8-13.

[0652] The vacuum chamber (22) includes an upper vacuum sealing (24) between the hammer weight and the containment surface and a lower vacuum sealing (25) (more clearly discernible in FIGS. 8-13.

[0653] FIG. 2a shows the vacuum chamber (22) at near its minimum volume, while FIG. 2b shows the maximum vacuum chamber (22) volume.

[0654] The vacuum chamber (22) is configured with at least one movable vacuum piston face (23) which in the embodiment of FIG. 2 is provided by the lower impact face (15) of the hammer weight (9). In alternative embodiments (not shown), the vacuum piston face (23) may be formed from an attachment to the hammer weight (9) rather than being integrally formed, e.g. like the lower impact face (15). Irrespective of its configuration, the vacuum piston face (23) is movable along a path parallel to, or co-axial to, the impact axis (10).

[0655] In addition to the shock absorber (19) and the striker pin (4), the nose block (20) also includes a retainer in the form of recoil plate (26), a retaining pin (27), a lower boundary in the form of a rigid nose plate (herein referred to as a nose cone (28)) and an attachment coupling (29) for attachment of the impact hammer (1) to the excavator (2). The interaction of the nose block (20) components is described in further detail elsewhere.

[0656] The operation of the impact hammer (1) and the movement of both the hammer weight (9) and the striker pin (4) in use require that the vacuum sealing (24, 25) is capable of accommodating relative and/or sliding movement therebetween. The vacuum sealing (24, 25) may be fixed to the hammer weight (9), within the nose block (20), containment surface (8) or a combination of same and these variations are subsequently considered in greater detail later.

[0657] In operation, a full reciprocation cycle of the impact hammer (1) comprises four basic stages (described more fully subsequently) consisting of; the up-stroke, upper stroke transition, down-stroke and lower stroke transition.

[0658] During these four stages (with reference to an impact hammer (1) orientated with a vertical impact axis (10)), the corresponding effects in the vacuum chamber (22) are: [0659] up-stroke: from the start position shown in FIG. 2a, the volume of the vacuum chamber (22) increases, as the hammer weight (9) is pulled upwards by the drive (11) via flexible connector (12), away from the cap plate (8) and striker pin (4). The vacuum chamber's (22) volume expansion causes a commensurate pressure drop in the vacuum chamber (22) relative to the air pressure outside the vacuum chamber (22), i.e. atmosphere, notwithstanding any sealing losses. The hammer weight (9) is raised with a commensurate pressure decrease in the vacuum chamber (22) until the hammer weight (9) reaches the up-stroke travel limit of its reciprocation path (shown in FIG. 2b); [0660] upper stroke transition: FIG. 2b shows the hammer weight (9) at its position of maximum potential energy before being released, and being driven towards the cap plate (8) and striker pin (4) under both the force of gravity and the atmospheric pressure acting on the vacuum chamber (22) via the hammer weight (9) volume; [0661] down-stroke: as the hammer weight (9) travels towards the driven end (17) of the striker pin (4), the volume of the vacuum chamber (22) is compressed and its internal pressure increases until it reaches the end of the down-stroke (shown in FIG. 2a); [0662] lower stroke transition: the volume of the vacuum chamber (22) is at its minimum) after energy transference from the hammer weight (9) to the working surface (5) via striker pin (4). At this point the hammer weight (9) is at the bottom of its reciprocation cycle.

[0663] The cycle is then repeated to break the working surface (5) by reciprocating the hammer (1).

[0664] In use, the striker pin (4) drops further than is shown in FIG. 2a as it is driven into the working surface (5) and thus the lowermost point possible of the striker pin (4) and hammer weight (9) is lower, as more clearly seen in FIGS. 38A-40B. The vacuum chamber (22) will thus also have a smaller volume than is shown in FIG. 2a. For the purposes of this description reference to a minimum volume or lowermost point will however refer to that shown in FIG. 2a as this is the point at the start of the reciprocation cycle.

[0665] During the above-described reciprocation cycle, the upper vacuum sealing (24) forms the dynamic sealing between the static containment surfaces (8) and the moving hammer weight (9). In the embodiment shown in FIGS. 2-4 and 8-13, the hammer weight (9) is provided with cushioning slides (1-13) about its side face (16). The cushioning slides (1-13) are formed with a: [0666] first layer (1-14) formed from a material of predetermined low friction properties (e.g. UHMWPE, Nylon, PEEK or steel), and [0667] second layer (1-15) formed from a material of predetermined shock absorbing properties such as an elastomer, e.g. polyurethane.

[0668] The functioning and roles of the cushioning slides (1-13) are more comprehensively expanded on below with reference to FIGS. 16-34b. The embodiment shown in FIGS. 1-3 incorporates two types of upper vacuum sealing (24), in the form of a pair of cushioning slides seals (30) and an in-weight seal (31). The cushioning slides (1-13) may be used for the coupling, mounting or retention of additional seals such as the configuration of the in-weight seal (31) to form the cushioning slide seals (30). It will be appreciated that the cushioning slides (1-13) may also directly form part or all of said upper (and/or lower) vacuum sealing (24, 25) and may thus also be designated as cushioning slide seals (30).

[0669] FIG. 4a shows both cushioning slides seals (30) and an in-weight seal (31) in greater detail.

[0670] FIGS. 4b-4k show further embodiments of upper vacuum sealing (24).

[0671] It will be appreciated that in alternative embodiments (not shown) the upper vacuum sealing (24) may alternatively be fixed to the containment surfaces (8) of the housing (6). However, there are several advantages in locating the upper vacuum sealing (24) on the hammer weight (9). Firstly, the distance travelled by the hammer weight (9) along the impact axis (10) greatly exceeds the length of the hammer weight (9) side face (16). Upper vacuum sealing (24) located on the containment surface (8) would need to extend over the full extent of the hammer weight (9) travel along the impact axis (10), while upper vacuum sealing (24) located on the hammer weight (9) is only essential at a single position about the impact axis (10). Secondly, upper vacuum sealing (24) located on the containment surface (8) adjacent the hammer weight's (9) path along the impact axis (10) is vulnerable to damage by any lateral movements of the hammer weight (9). Although this can be addressed by the incorporation of shock absorption and abrasion resistance capabilities, these must extend along the full extent of the containment surface (8) adjacent the hammer weight's (9) passage. In contrast, upper vacuum sealing (24) positioned on the hammer weight (9) may be configured to accommodate lateral weight movement without also being required to provide lateral shock absorbing or centering capacity.

[0672] It will also be appreciated that the hammer weight (9) may be formed in a variety of solid volumes, including a cube, cuboid, an elongate substantially rectangular/cuboid plate or blade configuration, prism, cylinder, parallelepiped, polyhedron and so forth. The embodiment shown in FIGS. 1-4 incorporate a cylindrical hammer weight (9), though this is illustrative only. An advantage of a cylindrical hammer weight (9) is the ability to utilize ring seals encircling the lateral periphery or side face (16) of the hammer weight (9), instead of separate seals for each side face (16) of a multi-sided hammer weight (9).

[0673] FIG. 4a shows an enlarged view of a down-stroke vent formed in the in-weight seal (31). The seal (31) is formed from a hard-wearing flexible material or other material providing abrasion resistance, flexibility, and heat resistance. The outer profile of the in-weight seal (31) is configured with a plurality of V-shaped protrusions (32) orientated with their apices angled upwards away from the vacuum chamber (22). These protrusions (32) form the down-stroke vent and permit air egress to the vacuum chamber (22) on the down-stroke while preventing or at least restricting air ingress on the up-stroke. Thus, during the up-stroke as the hammer weight (9) is raised, the vacuum chamber (22) pressure drops to a sub-atmospheric level, thereby generating an increasing pressure differential between the vacuum chamber (22) and the surrounding atmosphere. The v-shaped protrusions (32) are thus forced against the containment surface (8) occluding the vacuum chamber (22) from air ingress. At the bottom of the down-stroke, any air in the vacuum chamber, whether residual or having leaked past vacuum sealing (24, 25) is compressed to a super-atmospheric level (i.e. greater than atmosphere) and thus the pressure differential is reversed and the protrusions (32) are pushed open, thereby venting the air to atmosphere.

[0674] FIG. 4a shows an embodiment where the outermost surface of the first layer (1-14) of the cushioning slides (1-13) is able to act as a cushioning slide seal (30) in intimate sliding contact with the containment surface (8). It will be appreciated that whether a cushioning slide (1-13) also acts as a cushioning slide seal (30) or only as a cushioning slide (1-13) depends on the extent of its continuity about the hammer weight side face (16) to form a sealing barrier.

[0675] FIG. 4b shows another embodiment of a cushioning slide seal (30) formed as a circumferential seal in an insert in the first layer (1-14) of a cushioning slide (1-13). In a corresponding manner to the in-weight seal (31) of FIG. 4a, the outer profile of the cushioning slide seal (30) is also configured with a plurality of V-shape protrusions (32) orientated with their apices angled upwards away from the vacuum chamber (22). The cushioning slide (1-13) in FIG. 4b does show an additional feature in the form of a retention recess (33) which contains a ‘pre-load’ (36) formed from an elastomer ring that biases the cushioning slide seal (30) radially outward toward the containment surface (8). Such a preload (36) may also be used in other vacuum sealing (24, 25) embodiments. The cushioning slide seal (30) is able to be forced into the retention recess (33), compressing the pre-load (36) layer until the cushioning slide seal (30) is flush with the adjacent surface of the cushioning slide first layer (1-14) when the hammer weight (9) experiences any lateral movement during its reciprocation cycle due to for example, a non-vertical impact axis, hammer recoil bounce after impact with the striker pin (4), containment surface (8) imperfections or the like. This avoids the potentially significant lateral force of the hammer weight (9) being born solely by the small surface area of the relatively fragile cushioning slide seal (30).

[0676] The upper vacuum sealing (24) forms a substantially uninterrupted sealing laterally encompassing the hammer weight (9). The upper vacuum sealing (24) may be formed from a single continuous, uninterrupted seal or by multiple abutting, overlapping, conterminous, interlocking, mating, and/or proximal adjacent seal sections.

[0677] In the embodiment shown in FIG. 4c, the cushioning slide seal (30) is located in a retention recess (33) in the hammer weight side face (6). The cushioning slide seal (30) is formed directly by the outer surface of the cushioning slide first layer (1-14) and maintained in sealing contact with the containment surface (8) by virtue of a biasing means (spring (34)) located at a separation segment in the circular or part-circular cushioning slide first layer (1-14). The biasing means (34) is a further form of pre-load (36) and may take the form of a resilient material or a compression spring or the like, acting circumferentially to bias the cushioning slide seal (30) of first layer (1-14) radially outward into intimate contact with the containment surface (8). When the hammer weight (9) is deflected into contact with the containment surface (8) during operation, the cushioning slide seal (30) is able to retract into the retention recess (33) by compression of the cushioning slide second layer (1-15) thus avoiding any potentially damaging loads.

[0678] FIGS. 4c-4e show fillets (35) positioned between upper and lower biasing means (34) to prevent any circumvention of air about the biasing means (34) which could cause seal leakage. FIG. 4d is a plan view of section XX through the biasing means (34) in FIG. 4c, while FIG. 4e shows the plan view of section YY immediately above a fillet (35). Only one interruption is required in a circumferential seal (such as shown in FIGS. 4c-4e used with cylindrical hammer weights (9). In contrast, cubic, cuboid or other, multi-faceted hammer weights (9) may require the incorporation of multiple individual seals to maintain sealing about each vertex (37) of the hammer weight (9).

[0679] FIGS. 4f and 4g show an upper vacuum sealing (24) used in a square cross-section shaped weight (9). The sealing (24) is provided in the form of multiple cushioning slide seals (30) surrounding a vertex (37) of a cuboid hammer weight (6). The cushioning slide seals (30) in this embodiment are formed by the outer surface of the first layer (1-14) of cushioning slides (1-13). Biasing springs (34) ensure that the cushioning slide seals (30) are biased toward the containment surface (8) in a manner analogous to that shown in FIGS. 4c-4e. Fillets (35) are positioned between upper and lower biasing means (34) to prevent any circumvention of air about the biasing means (34) which could cause seal leakage.

[0680] In these embodiments, the vacuum sealing (24, 25) may include a seal with a radially acting pre-load (36) and a circumferentially acting biasing means (34). The preload may take several forms, including, but not limited to a compressible medium, a spring, an elastomer, buffers, or the like.

[0681] FIGS. 4h-4k show embodiments with intermediary elements (38) coupled to the hammer weight (9) below the impact face (10) and/or above the upper face (13) to provide a means of linking the upper vacuum sealing (24) to the movement of the hammer weight (9) along the impact axis (10), whilst allowing decoupled movement laterally to the impact axis (10). The intermediary elements (38) shown in FIGS. 4h-4k are configured to form the upper vacuum sealing (24) of the vacuum chamber (22), though it will be appreciated that the intermediary elements (38) may also be used in conjunction with other seal types described herein such as the cushioning slide seals (30), in-weight seals (31) and the like.

[0682] The intermediary elements (38) may be configured in a variety of forms, including plates, discs, annular rings and the like. FIGS. 4h and 4i show an intermediary element (38) coupled to the upper face (13) of the hammer weight (9) via flexible linkages in the form of straps (39).

[0683] Alternative embodiments for coupling the intermediary element (38) to the hammer weight (9) include non-flexible couplings which are laterally slideable with respect to the impact axis, while being substantially rigid parallel to the impact axis, as well as alternative flexible linkages, such as lines, wires, braids, chains, universal joints and so forth. Such coupling configurations allow the intermediate element (38) to maintain an effective sealing with the containment surface (8) without being affected by lateral movements of the hammer weight (9).

[0684] In the embodiment of FIG. 4h a single intermediary element (38) is formed as a substantially planar disc with a central aperture allowing the passage of the strop (12) for attachment to the hammer weight (9). A flexible seal (40) between the strop (12) and the intermediary element (38) prevents potential air ingress to the vacuum chamber (22). The substantially planar disc shaped intermediary element (38) includes an outer peripheral rim portion (74) which may form the upper vacuum sealing (24). Alternatively, or in addition, the upper vacuum sealing (24) may include a separate seal (75) coupled to the intermediary element (38) (as shown in FIGS. 4h-4k).

[0685] FIGS. 4j-4k show a further embodiment with a pair of intermediary elements (38a and 38b) positioned on either side of the hammer weight (9), coupled via flexible annular membranes (41a and 41b) to the upper face (13) and the lower impact face (15) respectively. However, in contrast to the preceding embodiment, the intermediary elements (38) in FIGS. 4j and 4k are configured as substantially annular rings, whereby the central aperture allows unhindered contact between the lower impact face (15) of the hammer weight (9) and the driven end (17) of the striker pin (4). The annular membranes (41) also provide part of the movable upper vacuum sealing (24).

[0686] During reciprocating operation of the impact hammer (1), the intermediary elements (38) (including straps (39) and annular membranes (41a, 41b)) are pulled or pushed along the reciprocation path by movement of the hammer weight (9) according to the direction of travel, and relative position of the intermediary element (38) relative to the hammer weight (9).

[0687] FIG. 4L shows another embodiment with five cushioning slides (1-13a to 1-13e) laterally encircling the hammer weight (9). The two intermediate cushioning slides (1-13b and 1-13d) have inner second layers (1-15b, 1-15d) that form biasing means (34) acting as preloads. The biasing means (34) may take the form of a resilient material, acting circumferentially to bias the cushioning slide seal (30) of first layer (1-14) radially outward into intimate contact with the containment surface (8). As is previously described, a pressure differential is formed between atmosphere and the vacuum chamber when the hammer weight (9) is raised on the up-stroke. The biasing means (34) in the embodiment of FIG. 4L are shaped such that air will be forced against the upper side of the biasing means (34) when a pressure differential is present, thereby further forcing the seal (30) against the containment surface (8) and improving its sealing effectiveness.

[0688] The other cushioning slides (1-13a, 1-13c, 1-13e) may also act as partial seals but primarily act as shock absorbing elements that also help to align the hammer (9) in the housing (6) as it reciprocates.

[0689] It can thus be seen that the seals forming the upper vacuum sealing (24) may be coupled to the hammer weight (9) by: [0690] a cushioning slide (1-13); [0691] mounting on, or retention or attachment to, an intermediary element (38); [0692] retention in a recess (33), void, space, aperture, groove or the like in the hammer weight (9), cushioning slide (1-13) and/or intermediary element (38); [0693] direct mounting on said side face (16); and/or [0694] any combination or permutation of the above.

[0695] As described previously, during impacting operation during which the vacuum chamber (22) expands during the up-stroke, air leakage into the vacuum chamber (22) may occur through any misaligned, ill-fitting, worn, inadequate or damaged seals or containment surfaces, interference from airborne residual debris, material or design characteristics or limitations and so forth. In all the embodiments shown in FIGS. 1-4, residual air may also be present in the vacuum chamber (22) before the start of the up-stroke in the void (42) formed between the lower impact face (15), the containment surfaces (8), the cap plate (21) and the striker pin driven end (17) protruding through the cap plate (21).

[0696] It is extremely difficult to achieve a completely impassable vacuum sealing (24, 25) in such a high speed, high energy reciprocation and thus during the up-stroke the upper (24) and/or lower (25) vacuum sealing may allow some air pass into the vacuum chamber (22), thereby increasing the pressure therein. The volume of such air leakage is dependent on a number of parameters, including the effectiveness of the sealing, area of sealing, pressure differential between vacuum chamber (22) and atmosphere and the exposure time the pressure differential is applied across the sealing.

[0697] The time the pressure differential is applied is relatively small as the cycle time of each reciprocation is 2-4 seconds. Reciprocating a heavy weight (9) (in the order of 1000's of Kilograms) over a 3-6 metre stroke length with a 2-4 cycle time is such a rapid rate that the heat that would be generated by the friction on a ‘soft’, e.g. rubber sealing (24, 25) would likely melt it after a few strokes.

[0698] Leakage can be minimised by using more seals and/or more flexible seals, however, this inherently increases friction and in such a high speed reciprocation, such seals can quickly become damaged or retard the hammer weight movement. Thus a balance is required between sealing effectiveness and friction. In preferred embodiments, the hammer weight (9) moves with such speed and force that highly effective seals such as rubber or other ‘soft’ seals are quickly damaged and become non-functional. Thus, it is preferable to use a less effective ‘hard’ seal that can withstand the high-friction loads, even though this may lead to more air leakage into the vacuum chamber.

[0699] Any residual air in the void (42) plus any leakage via the vacuum sealing (24, 25) and/or the housing (6) contributes to reduce the magnitude of the vacuum generated in the vacuum chamber (22). Moreover, on the down-stroke, any air inside the vacuum chamber (22) becomes increasingly compressed during the down-stroke applying a retarding force to the movement of the hammer weight (22).

[0700] As shown in FIGS. 2 and 3, the impact hammer addresses this serious issue by the incorporation of unidirectional down-stroke vents (43) formed in the side of the housing (6) in fluid communication with the vacuum chamber (22 to ensure air is vented during the down-stoke.

[0701] It will be appreciated however, that one or more vents (43) may alternatively, or additionally formed in the upper vacuum sealing (24) (as shown in FIGS. 2 and 4a-i).

[0702] Down-stroke vents may alternatively, or in addition be formed in the lower vacuum sealing (25), the nose block (20) and/or through the hammer weight (9) (not shown).

[0703] The vents (43) shown in FIGS. 2 and 3 are located in the containment surface (8) and pass through the housing (6) to atmosphere and includes a unidirectional valve (44). FIGS. 5a-c show three variants of a unidirectional, self-sealing valve (44), in the form of a flexible poppet (or mushroom) valve (FIG. 5a), a rigid poppet valve (FIG. 5b), and a side opening flap valve (FIG. 5c) respectively. The open vent position of the respective sealing valves (44) is denoted by reference numeral (44) in each of FIGS. 5a-c.

[0704] An additional or alternative mechanism of removing residual air in the vacuum chamber (22) is shown in FIG. 6 and provided by a down-stroke vent in the form of an external vacuum pump (45) connected to the vent (43).

[0705] FIG. 7 also shows an external vacuum pump (45), mounted to vent (43) via valve (44) to an intermediate vacuum tank (46). The vacuum pump (45) may be configured to operate continuously during the operating cycle, triggered according to threshold vacuum levels, or according to other sensing or input criteria. The vacuum tank (46) provides a degree of vacuum pressure at the vent (43) without the vacuum pump (45) necessarily operating.

[0706] In each embodiment, the down-stroke vents (43) are designed to open on the hammer down-stroke to permit air egress from the vacuum chamber (22) and closed on the up-stroke to prevent or at least restrict air ingress to the vacuum chamber (22). The down-stroke vents are biased closed with a bias sufficient to prevent undesired opening due to hammer vibration or impacts while opening when the pressure in the vacuum chamber reaches a threshold super-atmospheric level, e.g. 0.1 Bar.

[0707] Thus, compression of any air inside the vacuum chamber and the resultant heat is minimised as the air and heat is vented. A means for optionally reducing the potential for residual air in the void (42) is shown in FIG. 3 where the portion of the vacuum chamber (22) about the driven end (17) of the striker pin (4) is at least partially filled by one or more void-reduction objects. FIG. 3 shows a void reduction object in the form of foam (73) positioned in the void (42) to remain clear from contact from the hammer weight (9) during impact between lower impact face (15) and the striker pin driven end (17). Alternative void reduction objects include spheres, interlocking shapes, gels and the like.

[0708] A variety of alternative sealing configurations from said upper vacuum sealing (24) may be employed to form said lower vacuum sealing (25).

[0709] In contrast to the upper vacuum sealing (24), the lower vacuum sealing (25) is not subjected to the same magnitude of relative movement between adjacent sealing surfaces. While the upper vacuum sealing (24) is required to seal the movement of the hammer weight (9) along its travel along the reciprocation axis (at least several meters), the lower vacuum sealing (25) need only seal the movement of the striker pin (4) relative to the elements of the nose block (20).

[0710] FIGS. 8-13 show different embodiments of lower vacuum sealing (25) located in the impact hammer (1) nose block (20). A fuller description of the striker pin (4), shock absorber (19) and its housing in the nose block (20) is described below with reference to FIGS. 35-48c. In part however, and with respect to FIGS. 1-4, and 8-13, it can be seen that: [0711] the striker pin (4) is attached to the impact hammer (1) by a slideable coupling in the form of two retaining pins (27) passing laterally through the recoil plate (26) such that a portion of each pin (27) partially projects inwardly into a recess (47) formed in the striker pin (4). [0712] the recoil plate (26) connects the striker pin (4) via the slideable coupling at a retaining location defined by the length of the recess (47) between (with respect to the driven end of the striker pin (4)) a distal and proximal travel stops (48, 49). [0713] the shock absorber (19), in the form of first and second shock absorbing assemblies (50, 51) (also referred to as the upper and lower shock absorbing assemblies (50, 51)) laterally surround the striker pin (4) within the nose block (20) and are interposed by the recoil plate (26). [0714] in the embodiments shown specifically in FIGS. 2, 4f, 4h and 9, the second shock-absorbing assembly (51) is formed from a plurality of un-bonded layers including multiple elastic layers (52) interleaved by inelastic layers (53, 26, 28). This is best shown in FIG. 9b. [0715] the first shock-absorbing assembly (50) in FIGS. 8-13 and the second shock-absorbing assembly (51) in FIGS. 8 and 10-13 is shown as a buffer symbol and denotes either a unitary shock-absorbing layer or buffer such as a single elastic layer (52) or plurality of un-bonded layers including at least two elastic layers (52) interleaved by an inelastic layer (53).

[0716] The planar surfaces of the nose block (20) inner boundaries are formed at the upper end by the cap plate (21) and at the lower end by the nose cone (28).

[0717] It can thus be seen that these inner boundaries and the upper and lower planar surfaces of the recoil plate (26) provide four rigid, inelastic surfaces adjacent to the shock absorbing assemblies (50, 51). Thus, depending on the number of elastic (52) and inelastic layers (53) employed in an embodiment, an individual elastic layer (52) may be interposed by the rigid planar surfaces of either: [0718] the cap plate (21) and an inelastic layer (53); [0719] the nose cone (28) and an inelastic layer (53); [0720] two inelastic layers (53), or [0721] an inelastic layer (53) and the recoil plate (26).

[0722] In each of the above configurations, the elastic layer (52) is sandwiched between the parallel planar surfaces of the adjacent rigid surfaces orthogonal to the striker pin longitudinal axis, co-axial with the impact axis (10).

[0723] It can be thus seen that positioned about the striker pin (4) between the driven end (17) and the impact end (18) is the following sequence of nose block elements (20): [0724] cap plate (21); [0725] first (or upper) shock absorbing assembly (50); [0726] recoil plate (26); [0727] second (or lower) shock absorbing assembly (51), and [0728] nose cone (28).

[0729] The lower vacuum sealing (25) is required to prevent or at least restrict air ingress via the above-listed nose-block elements into the vacuum chamber (22) and may be formed from seals positioned at several alternative, or cumulative positions in the above sequence of nose block elements.

[0730] The lower vacuum sealing (25) may thus be provided by one or more seals positioned at one of more of the interfaces between adjacent elements of the nose block (20). The different potential positions of the seals are: [0731] between the nose cone (28) and the striker pin (4) (shown in FIG. 8): [0732] between the lower shock absorbing assembly (51) and the striker pin (4) (shown in FIGS. 9a and 9b); [0733] between the recoil plate (26) and the striker pin (4) (shown in FIG. 10) and/or between a nose block inner side wall (54) (shown in FIG. 10); [0734] between the upper shock absorbing assembly (50) and the striker pin (4) (not shown), and/or [0735] between the cap plate (21) and the striker pin (4) (not shown).

[0736] According to a further embodiment, the lower vacuum sealing (25) is provided by one or more seals formed as individual independent sealing layers (55) laterally encompassing the striker pin and located: [0737] between the nose cone (28) and the lower shock absorbing assembly (51) (shown in FIG. 11); [0738] between the upper shock absorbing assembly (50) and the cap plate (21) (shown in FIG. 12), and/or [0739] between the cap plate (21) and the lower travel extremity of the lower impact face (15) of the hammer weight (9) (shown in FIG. 13).

[0740] Considering the above referenced configurations individually in more detail, FIG. 8 shows a lower vacuum sealing (25) formed from a plurality of nose cone ring seals (56) located in corresponding annular recesses (57) in the nose cone (28). The nose cone ring seals (56) are engaged against the surface of the striker pin (4) to inhibit ingress of air, dust and detritus into the nose block (20) interior and subsequently to the vacuum chamber (22). The nose cone ring seals (56) may be venting (i.e. acting as additional down-stroke vents) or non-venting and formed from elastic or inelastic materials biased against the striker pin (4). It will be appreciated that any of the lower vacuum sealing (25) embodiments shown in FIGS. 9-13 may be formed as venting or non-venting seals, depending on the specific requirements of the impact hammer (1). It may not be essential for venting to be performed through the lower vacuum sealing (25) as venting may be performed via vents (43) in the housing (6) and/or the upper vacuum sealing (24). Furthermore, forming the lower vacuum sealing (25) without venting enables more robust, higher performance seals to be used which in turn enable a greater resistance to atmospheric ingress. Given the nose-block (20) is positioned in direct exposure to the debris and airborne contamination from impacting operations, it is typically more desirable to maximise nose block (20) atmospheric ingress prevention rather than supplement the vacuum chamber (22) venting.

[0741] FIG. 9a shows the lower vacuum sealing (25) formed between the striker pin (4) and either, or both of, the lower shock absorbing assembly (51) and the upper shock absorbing assembly (50).

[0742] FIG. 9b shows an enlarged view of the lower shock absorbing assembly (51) formed from a plurality of elastic layers (52) interleaved by inelastic layers (53). Seals may be formed from or in either, or both of, the elastic layers (52) and inelastic layers (53) and FIG. 9b illustrates several alternative configurations. The lower vacuum sealing (25) arrangement depiction in FIG. 9b is illustrative and does not imply such a combination of seals is required or that the invention is restricted to same.

[0743] FIG. 9b shows a lower vacuum sealing (25) in lower shock absorbing assembly (51) in the form of: [0744] an integral elastic layer seal (58) forming the inner peripheral edge (and optionally, the outer peripheral edge (not shown)) of the elastic layer (52) adjacent the striker pin (4). The seal (58) is shaped to let air pass if the pressure on the upper side is super-atmospheric, i.e. the seal (58) acts as a down-stroke vent as previously described; [0745] a distinct elastic layer seal (59), abutting the inner peripheral edge (and optionally, the outer peripheral edge (not shown)) of the elastic layer (52) adjacent the striker pin (4). This seal (59) also acts as a down-stroke vent as per seal (58); [0746] an inelastic layer seal (60) retained within or coupled to the inner peripheral edge (and optionally, the outer peripheral edge (not shown)) of the inelastic layer (53) and formed from elastic or inelastic material; [0747] an intimate fit seal (61) between a shock absorbing assembly inelastic layer (53) and the striker pin (4), and/or between the inelastic layer (53) and the nose block inner side wall (54) (not shown), [0748] a distinct elastic or inelastic layer seal (75), abutting the inner peripheral edge (and optionally, the outer peripheral edge (not shown)) of the inelastic layer (53) adjacent the striker pin (4), and/or [0749] any combination or permutation of the above.

[0750] FIG. 10 shows a pair of recoil plate ring seals (62) located in annular recesses (63) about the inner and outer periphery of the recoil plate (26) adjacent the striker pin (4) and nose block inner side wall (54) respectively. It should be understood that the outer recoil plate ring seal (62) engaging against the nose block inner side wall (54) is present as an additional safeguard seal to the inner recoil plate ring seal (62). The combined stack of nose block (20) elements (i.e. the upper and lower shock absorbing assemblies (50, 51) and recoil plate (26)) themselves effectively provide a composite seal to the ingress of air. It will thus be appreciated that corresponding seals (not shown) between the nose block inner side wall (54) and the upper and lower shock absorbing assemblies (50, 51) are also possible as additional safeguard seals.

[0751] FIGS. 11-13 show the use of individual independent sealing layers (55) to provide the lower vacuum sealing (25). Although the independent sealing layers (55) may be configured in a variety of forms, in the embodiments of FIGS. 11-13, each independent sealing layer (55) is formed with an inner flexible diaphragm (64) portion and a cylindrical, substantially rigid, outer rim (65) portion. The periphery of the flexible diaphragm (64) contacting the striker pin (4) is free to flex with the movement of the striker pin (4) along the impact axis (10), i.e. moving with the striker pin (4) from an upper position (64) when the striker pin (4) is an uppermost position to a lower position (64′) as the striker pin (4) moves down. The outer rim (65) also provides a sealing wall between adjacent nose block elements. An additional safeguard static seal (66) is located between the diaphragm rim portion (65) and the inner nose block walls (54).

[0752] FIG. 11 shows the independent sealing layer (55) positioned between the nose cone (28) and the lower shock absorbing assembly (51).

[0753] In FIG. 12, the independent sealing layer (55) is positioned between the upper shock absorbing assembly (50) and the cap plate (21).

[0754] In FIG. 13, the independent sealing layer (55) is positioned outside the nose block (2) in the void (42) between the cap plate (21) and the lower travel extremity of the lower impact face (15) of the hammer weight (9).

[0755] The lower vacuum sealing (25) may alternatively be formed from, or include; a flexible elastomer, an elastic or inelastic material, biased into contact with the striker pin and/or the nose block inner side walls by a preload or imitate fit, unidirectional vent and/or any combination or permutation of same.

[0756] As discussed above, preferred embodiments are able to operate effectively at any inclination of the impact axis (10), including upwards. This provides great versatility for general impacting operations, quarrying, mining, extraction, demolition work and so forth. It also enables the impact hammer to be applied to specialised applications such as a further embodiment in the form of a robotic tunnelling impact hammer (200) shown in FIG. 14. The inherent operator danger from overhead rock-fall in tunnelling operations naturally favours the use of remote-control impact hammers. The restricted confines often associated with tunnelling further suit compact impact hammers with a high impact energy/volume ratio. The need to operate at steep impact axis (10) inclinations further restricts the suitability of prior art gravity-only impact hammers. The robotic tunnelling impact hammer (200) shown in FIG. 14 includes a striker pin (4) configuration located in a housing (6) comparable to that shown in the preceding embodiments. The housing (6) is mounted on a tracked carrier (71) via an azimuth cradle (72) which enables the impact hammer (200) to vary the inclination angle (θ) of the impact axis (10). In FIG. 14, the impact hammer (200) is illustrated at three orientations X.sub.1, X.sub.2, X.sub.3 with a corresponding impact axis (10) inclination from vertical of θ=70°, 90° and 105° respectively. Clearly these orientations are exemplary and the invention is not limited to same. It will also be readily apparent that the robotic tunnelling impact hammer (200) is not necessarily restricted to tunnelling operations and may be used in other confined areas, close to steep rock-faces, trenching and the like.

[0757] FIGS. 15a and 15b show a comparison between a prior art gravity-only impact hammer (100) shown in FIG. 15b, and a vacuum-assisted impact hammer (1) according to one preferred embodiment in FIG. 15a. The above-documented capacity to use a lighter hammer weight (9) to achieve the same impact energy as a conventional prior art gravity-only impact hammer (100) (even with a shorter maximum drop height) provides yet further weight saving, manufacturing and associated economic benefits. During the operating cycle, at the end of the down-stroke, the hammer weight (9) impacts the driven end (17) of the striker pin (4) thereby transferring kinetic energy via the striker pin (4) to the working surface (5).

[0758] However, as explained in greater detail elsewhere, not all the kinetic energy of the hammer weight (4) is transferred to the working surface (5), as in the event of: [0759] a ‘mis-hit’ when the operator drops the hammer weight (4) on the striker pin (4) driven end (17) without the impact end (18) being in contact with the working surface (5), the impact of the hammer weight (9) forces the proximal travel stop (49) against the slideably coupled retaining pin (27) (components shown most clearly in FIG. 3). Appreciable shock load is thus transferred through, and absorbed by, the impact hammer (1). [0760] ‘Over-hitting’ whereby even though the working surface (5) does fracture successfully after a strike, the impact may only absorb a portion of the kinetic energy of the striker pin (4) and hammer weight (9). In such instances, the resultant effect on the impact hammer (1) is directly comparable to a ‘mis-hit’. In practice, the impacting operations are undertaken at a wide variety of inclinations, and are seldom performed with a perfectly vertical impact axis (10). [0761] the nature of the working surface (5) requiring multiple impacts before fracture occurs, and thus the striker pin (4) or hammer weight (9) may recoil away from the unbroken working surface (5). The direction of the recoiling striker pin/hammer weight (4, 9) will predominately include a component lateral to the impact axis (10), thereby bringing it into contact with the housing (6) containment surface (8).

[0762] Due to the relatively massive mass of the hammer weight (9) in comparison to the rest of the impact hammer (1), the contact area between the hammer weight (9) and the containment surface (8) is particularly vulnerable to damage. Consequently, the portion of the containment surface (8) and adjacent hammer housing (6) surrounding the hammer weight (9) at the point of impact with the striker pin (4) requires additional strengthening compared to the remainder of the housing (6). FIGS. 15a and 15b show the relative difference between: [0763] the vacuum-assisted impact hammer (1) of FIG. 15a; [0764] hammer weight height V.sub.W [0765] hammer stroke length V.sub.X [0766] overall housing column length V.sub.L [0767] strengthened housing portion V.sub.X
and
the gravity-only prior art impact hammer (100) of FIG. 15b; [0768] hammer weight height G.sub.W [0769] hammer stroke length G.sub.X [0770] overall housing column length G.sub.L [0771] strengthened housing (6) portion G.sub.X
wherein [0772] the overall housing column length V.sub.L, G.sub.L is the length of the containment surface (8) parallel with the impact axis (10) between the driven end (17) of the striker pin (4) and the upper distal end of the housing (6), and [0773] the hammer stroke length V.sub.X, G.sub.X is the distance travelled by the hammer weight (9) along the impact axis (10) inside the containment surface (8).

[0774] As described previously, the impact hammer (1) can achieve the same impact energy as a prior art gravity-only impact hammer (100) using a significantly lighter hammer weight (4). Assuming an equal diameter (to facilitate comparison), it follows that the hammer weight height V.sub.W of the vacuum-assisted impact hammer (1) is less than the hammer weight height G.sub.W of the prior art impact hammer (100). The reduced hammer weight height V.sub.W compared to the hammer weight height G.sub.W produces numerous advantages for the impact hammer (1), namely: [0775] despite the hammer stroke length V.sub.X being equal to the hammer stroke length G.sub.X, the overall column length V.sub.L is less than overall column length G.sub.L. The additional length of overall housing column length G.sub.L required by the prior art impact hammer (100) naturally increases the total weight of the impact hammer (100) and consequently adds six to seven times that value to the weight of the required excavator (2). As the extra weight on the prior art hammer (100) is located at the extremity of the housing (6), its polar moment of inertia also detrimentally increases the required strength (and thus weight) of the type of excavator (2) able to manoeuvre the impact hammer (100) effectively; [0776] the strengthened housing portion V.sub.X of the impact hammer (1) is shorter than the corresponding portion G.sub.X in direct proportion to the difference in the hammer weight heights G.sub.W-V.sub.W. This results in further weight savings for the vacuum-assisted impact hammer (1). [0777] As the hammer weight height V.sub.W of the vacuum-assisted impact hammer (1) is only a third of the hammer weight height G.sub.W of the prior art impact hammer (100), the behaviour of the respective hammer weights (9) during lateral impacts with the containment surface (8) differ. As the hammer weight (9) is deflected laterally towards the containment surface (8), it will seldom make simultaneous uniform contact with the containment surface (8) and the hammer weight side face (16) precisely parallel. Instead, the hammer weight (9) tends to rotate with respect to the containment surface (8) generating a couple. The resulting impact with the containment surface (8) is thus a point load rather than being dissipated uniformly along the length of the strengthened housing portion V.sub.X, G.sub.X. The vastly shortened hammer weight height V.sub.W of the vacuum-assisted impact hammer (1) significantly reduces the magnitude of such forces, thus further reducing the magnitude of the strengthening required over the strengthened housing portion V.sub.X relative to the prior art hammer (100).

[0778] FIGS. 16-17 show apparatus according to separate embodiments being in the form of impact hammers with weights fitted with cushioning slides.

[0779] FIG. 16 shows a further embodiment of an apparatus in the form of a small impact hammer (1-1) fitted to a small excavator (1-2).

[0780] The impact hammer (1-1) includes: [0781] a lifting and/or reciprocating mechanism (not shown), [0782] a reciprocating component in the form of a weight configured as a unitary hammer weight (1-3) with an integral tool end (1-4) for striking a working surface (1-5) and [0783] a housing (1-6) attached to the excavator (1-2) and partially enclosing the hammer weight (1-3) with a containment surface in the form of housing inner side walls (1-7).

[0784] FIG. 17 shows an alternative apparatus embodiment in the form of a large impact hammer (1-100) fitted to a large excavator (1-102).

[0785] The impact hammer (1-100) includes: [0786] a lifting mechanism (not shown) [0787] a reciprocating component in the form of a weight (1-103) [0788] a housing (1-106) attached to the excavator (1-102) and partially enclosing the hammer weight (1-103) with a ‘containment surface’ or ‘housing weight guide’ provided in the form of a housing inner side walls (1-107).

[0789] The lifting mechanism raises the weight (1-103) within the housing weight guide (1-107), before being dropped onto a striker pin (1-104), which in turn impacts the working surface (1-105).

[0790] Regarding the hammer (1-1) shown in FIGS. 16, 18a-d, and 22a-b, the hammer weight (1-3) is an elongate substantially rectangular/cuboid plate or blade configuration. The hammer weight (1-3) is of rectangular lateral cross section and composed of a pair of parallel longitudinal wide side walls (1-8), joined by a pair of parallel short side walls (1-9), with opposing upper and lower distal faces (1-10, 1-11) each provided with tool ends (1-4). The symmetrical shape of the hammer weight (1-3) enables the tool ends (1-4) to be exchanged when one is worn. The hammer weight (1-3) is removed from the housing (1-6) and re-inserted with the position of the tool ends (1-4) reversed. The hammer shown in FIG. 18a-d however only has one tool end (1-4).

[0791] In operation, the hammer weight (1-3) reciprocates about a linear impact axis (1-12) passing longitudinally through the geometric centre of the hammer weight (1-3). The hammer weight (1-3) is raised upwards along the impact axis (1-12) by the lifting mechanism to its maximum vertical height, prior to being released, or driven downwards back along the impact axis (1-12) until impacting with the working surface (1-5).

[0792] FIG. 18b shows the hammer weight (1-2) of FIG. 18a with the addition of a pair of centrally located cushioning slides (1-13). FIG. 18c is an exploded diagram showing the components of the cushioning slides (1-13), namely: [0793] a first layer (1-14) formed from a material of predetermined low friction properties such as UHMWPE, Nylon, PEEK or steel, and [0794] a second layer (1-15) formed from a material of predetermined shock absorbing properties such as an elastomer, e.g. polyurethane.

[0795] The first layer (1-14) is formed with an exterior surface (1-16) configured and orientated to be the first contact point between the side walls (1-8, 1-9) and the housing inner side walls (1-7). The second layer (1-15) is located between the first layer (1-14) and the weight side wall (1-8, 1-9) and formed with an outer surface (1-17) connected to the underside (1-18) of the first layer (1-14) and an interior surface (1-19) connected to the weight side walls (1-8, 1-9).

[0796] The first and second layers (1-14, 1-15) are substantially parallel to each other and to the outer surface of the sidewalls (1-8, 1-9). Although the cushioning slides (1-13) may be located in a variety of positions on the side walls (1-8, 9), the narrow width of the short side walls (1-9) in the embodiment shown in FIG. 18a-d allows a single cushioning slide (1-13) to be used that spans the full width of the narrow side wall (1-9) between adjacent longitudinal apices (1-20) and extending to part of the opposing wide side walls (1-8).

[0797] In the alternative embodiment shown in FIGS. 17 and 19, the weight (1-103) differs from the embodiment of FIGS. 16 and 18a-d in: [0798] size—a significantly larger mass/weight; [0799] shape—block shaped rather than blade, and [0800] upper and lower ends—planar, not fitted with tool ends (1-4).

[0801] The hammer (1-103) may also take the form of the vacuum assisted hammer (1) described with respect to FIGS. 1-16.

[0802] As the weight (1-103) is used to impact a striker pin (1-104), there is no need for a tool end or the ability to be reversed. The weight (1-103) is a substantially cuboid block of rectangular cross section with a pair of parallel longitudinal wide side walls (1-108), joined by a pair of parallel shorter side walls (1-109), with an opposing upper and lower distal faces (1-110, 1-111).

[0803] In operation, the hammer weight (1-103) reciprocates about a linear impact axis (1-112) passing longitudinally through the geometric centre of the hammer weight (1-103). The hammer weight (1-103) is raised upwards along the impact axis (1-112) by the lifting mechanism to its maximum vertical height, prior to being released, falling under gravity and/or with a vacuum assistance along the impact axis (1-112) until impact with the striker pin (1-104). The weight (1-103) is fitted with a plurality of cushioning slides (1-113) positioned about the side walls (1-108, 1-109).

[0804] FIGS. 19 and 20a show an exploded view of the components of the cushioning slides (1-113), namely: [0805] a first layer (1-114) formed from a material of predetermined low friction properties such as UHMWPE, PEEK, steel and [0806] a second layer (1-115) formed from a material of predetermined shock absorbing properties such as elastomer, e.g. polyurethane.

[0807] FIGS. 20b and 20c show the assembled cushioning slides (1-113) fitted to the weight (1-103) on both the planar side walls (1-108, 109) and on the four longitudinal apices (1-120) of the weight (1-103)

[0808] The first layer (1-114) is formed with an exterior surface (1-116) configured and orientated to be the first contact point between the side walls (1-108, 1-109) and the housing inner side walls (1-107). The second layer (1-115) is located between the first layer (1-114) and the weight side wall (1-108, 1-109) and formed with an outer surface (1-117) connected to the underside (1-118) of the first layer (1-114) and an interior surface (1-119) connected to the weight side walls (1-108, 1-109). The first and second layers (1-114, 1-115) are substantially parallel to each other and to the outer surface of the sidewalls (1-108, 1-109).

[0809] The cushioning slides (1-113) placed on the sidewalls (1-108, 1-109) in the embodiment of FIGS. 17, 19, and 20a-c are rectangular plates in outline, however alternative shapes may be utilized such as the circular cushioning slides (1-113) shown in FIG. 21.

[0810] FIGS. 22a and 22b show two further configurations of the hammer weight (1-3) shown in FIGS. 16 and 18a-d. FIG. 22a shows the bidirectional hammer weight (1-3) with twin identical tool ends (1-4), capable of being reversed when one tool end (1-4) becomes worn. The hammer weight (1-3) is also capable of being used for levering and raking rocks and the like, whereby the hammer weight (1-3) is locked from movement along the impact axis (1-12) with the side walls (1-8, 1-9) adjacent lower distal face (1-11) projecting outside beyond the housing (1-6) to perform the levering. Any cushioning slides (1-13) directly exposed to the effects of the levering and raking would be damaged. Thus, the cushioning slides (1-13) are longitudinally positioned away from both distal ends (1-10, 1-11) of the hammer weight (1-3).

[0811] FIG. 22b shows a unidirectional hammer weight (1-3), with only one tool end (1-4), which is also capable of levering and raking, though without being reversible. Consequently, the cushioning slides (1-13) are asymmetrically arranged longitudinally, with additional cushioning slides positioned near the upper distal surface (1-10).

[0812] Impact hammers (including the impact hammers (1, 1-1, 1-100) described above) are configured to raise and lower the weight with the minimum obstruction or resistance from the housing (6, 1-6, 1-106). The hammer weight (9, 1-3, 1-103) is only directly connected to the lifting mechanism (not shown) and not the housing inner side walls (8, 1-7, 1-107). Thus, as the weight (9, 1-3, 1-103) travels upwards or downwards, any deviation from a perfectly vertical impact axis (10, 1-12, 1-112) for the path of the weight (9, 1-3, 1-103) and/or the orientation of the housing inner side walls (8, 1-7, 1-107) can lead to mutual contact.

[0813] An initial point of impact is predominantly at one of the weight apices (1-20, 1-120) which applies a corresponding moment to the weight (1-3, 1-103), causing the weight (1-3, 1-103) to rotate until impact on the diametrically opposite apex (1-20, 1-120) unless the weight (1-3, 1-103) reaches the top or bottom of its reciprocation path first. The impact of the weight (1-3, 1-103) on the working surface (1-5, 1-105) may also generate lateral reaction forces if the working surface (1-5, 1-105) is not orthogonal to the impact axis (1-12, 1-112), and/or, if the working surface (1-5, 1-105) does not fracture on impact.

[0814] FIGS. 23a-b show the hammer weight (1-3) impacting an uneven working surface (1-5), which generates a commensurate lateral reaction force away from the working surface (1-5). The moment induced in the weight (1-3) by the lateral reaction force causes a rotation of the weight (1-3) away from the working surface (1-5). This rotation may be substantially parallel to the plane of the wide side walls (1-8) (as shown in FIG. 23a) or substantially parallel to the plane of the narrow side walls (1-9) (as shown in FIG. 23b) or any combination of same. The rotating effect of the contact causes diametrically opposite portions of the weight (1-3) to come into contact with the weight housing guide (1-7).

[0815] The hammer weight (1-3) shown in FIGS. 23a-b represents a reversible, bi-directional hammer weight (1-3) suitable for raking and levering. Consequently, the cushioning slides (1-13) are located centrally along the longitudinal side walls (1-8, 9) to avoid damage during levering/raking. However, the cushioning slide (1-13) is sufficiently dimensioned to ensure the outer surface (1-16) of the first layer (1-14) comes into contact with the surface of the housing weight guide (1-7) before the distal portion of the apices (1-20).

[0816] FIG. 24 shows a comparable situation with the weight (1-103) of the embodiment of FIGS. 17, 19, and 20a-c impacting the (housing inner side walls (1-107) during its downward travel. Again, the impact of the lower distal portion of the weight side wall (1-109) causes a moment-induced rotation in the weight (1-103) with a corresponding impact on the upper distal portion of the opposing side wall (1-109). The cushioning slides (1-113) on the weight (1-103) are thus positioned at these points of contact.

[0817] When the weight (1-3, 1-103) impacts the housing inner side walls (1-7, 1-107) and a compressive load is applied to the elastomer forming the second layer (1-15, 1-115), the shock is absorbed by displacement of volume of the elastomer (1-15, 1-115) away from the point of impact.

[0818] Any rigid boundaries surrounding the elastomer (1-15, 1-115) restrict the displacement of the elastomer (1-15, 1-115) to occur at any unrestrained boundaries. In the preceding embodiments where the elastomer (1-15, 1-115) is bounded by the rigid first layer underside (1-18, 1-118) and the rigid upper surface (1-21, 1-121) of the weight (1-3, 1-103) underneath the elastomer (1-15, 1-115), the elastomer (1-15, 1-115) is displaced laterally substantially parallel with the surface of the weight (1-3, 1-103) under compression.

[0819] The embodiment shown in FIGS. 16-19 provides the elastomer (1-15, 1-115) with displacement voids (1-22, 1-122) into which the displaced volume may enter under the effects of compression. As shown in FIG. 18c, the cushioning slide (1-13) incorporates a series of circular displacement voids (1-22) in the second layer (1-15), extending substantially uniformly along the second layer (1-15) on three sides such that the series of voids (1-22) extends over the weight surfaces (1-21) on each wide side wall (1-8) and the corresponding narrow side wall (1-9).

[0820] The embodiment in FIG. 19 also utilises a corresponding configuration of circular displacement voids (1-122) in the second layer (1-115) of the cushioning slide (1-113).

[0821] The elastomer cannot deflect laterally outwards under compression as the cushioning slides (1-13, 1-113) in both embodiments are surrounded on their exterior lateral periphery by rigid portions (1-21, 1-121) of the weight (1-3, 1-103). Therefore, under compression, the elastomer (1-15, 1-115) is only able to displace laterally inwards into the circular displacement voids (1-22, 1-122). In further embodiments (not shown), the displacement voids may be formed in the first layer underside (1-18, 1-118), and/or the rigid upper surface (1-21, 1-121) of the weight (1-3, 1-103) underneath the elastomer (1-15, 1-115).

[0822] However, a variety of alternative configurations of displacement void are possible and exemplary samples are illustrated in FIGS. 25a-d and 26a-d. FIGS. 25a-d show four alternative second layer (1-15a, 15b, 15c, 15d) embodiments incorporating four different displacement void configurations, shown in greater detail in section view in FIGS. 26a-d respectively. Although each second layer (1-15a-d) is shaped to fit the corresponding contours of the weight surface (1-21, 1-121) to which its fitted, the portion of each second layer (1-15a-d) adjacent a side wall (1-8, 1-9, 1-108, 1-109) is still substantially planar.

[0823] FIGS. 25a and 25b respectively show cushioning slides (1-13, 1-113) configured to be fitted to a longitudinal apex (1-20, 1-120). FIGS. 25c and 25d respectively show rectangular and circular cushioning slides (1-13, 1-113) for fitment to a side wall (1-8, 1-9, 1-108, 1-109).

[0824] FIGS. 26a-d, show enlargements of section views through the lines AA, BB, CC and DD in FIGS. 25a-d respectively before (LHS) and after (RHS) the application of a compressive force in the direction of the arrows.

[0825] FIG. 26a shows a second layer (1-15a) with a series of displacement voids (1-22a) in the form of apertures extending orthogonally through the second layer (1-15a) from the upper surface (1-17a) to the lower surface (1-19a). The right side illustration shows the elastomer material of the second layer (1-15a) bulging into the adjacent displacement voids (1-22a).

[0826] FIG. 26b shows a second layer (1-15b) with a series of displacement voids (1-22b) in the form of repeated corrugated indentations in the underside (1-19b) of the second layer (1-15b). The corrugations become shorter and wider under the effects of compression and deflect into the voids (1-22b).

[0827] FIG. 26c shows a second layer (1-15c) with a series of displacement voids (1-22c) in the form of repeated indentations formed between a plurality of circular cross-section projections on both the underside (1-19c) and upper surface (1-17c) of the second layer (1-15c). Under compression, the projections deflect laterally into the displacement voids (1-22c) thereby becoming shorter and wider.

[0828] FIG. 26d shows a second layer (1-15d) formed with a saw tooth shaped underside (1-19d) and upper surface (1-17d) creating a corresponding series of saw tooth shaped displacement voids (1-22d). The apex of the saw tooth profile is flattened under the effects of compression thus deflecting into voids (1-22d). It will be readily appreciated that numerous alternative displacement void configurations are possible and that the combinations of cushioning slides (1-15a-d) shown in FIGS. 25a-d and while the displacement void (1-22a-d) configurations in FIGS. 26a-d are optimised examples they should not be seen to be limiting.

[0829] The shock absorbing elastomer forming the above described second layers (1-15, 1-115, 1-15a-1-15d) all provide a configuration to absorb the impact shock by allowing the elastomer to be deflected into the displacement voids (1-22, 1-122, 1-22a-1-22d) thereby preventing damage to the elastomer polymer. The deflection is typically less than 30% as above 30% deflection there is an increasing likelihood of damage occurring to the cushioning slides.

[0830] The shock absorbing potential capacity of the cushioning slides (1-13, 1-113) is enhanced by keeping the adjacent contact surfaces of the first (1-14, 1-114) and second (1-15, 1-115) layers unbonded or un-adhered to each other. The contact surfaces being first layer upper surface (1-17, 1-117) and the second layer lower surface (1-18, 1-118). This enables the elastomer upper surface (1-17) to move laterally across the underside (1-18) of the first layer under compression. However, the first (1-14, 1-114) and second layers (1-15, 1-115) clearly require a means to maintain their mutual contact under the violent effects of the impacting operations.

[0831] FIG. 27a-e shows a selection of exemplary configurations of securing features (1-23) configured to keep the first (1-14, 1-114) and second layers (1-15, 1-115) in mutual contact.

[0832] FIG. 27a shows a securing feature (1-23a) in the form of mating screw thread portions located at the lateral periphery of the first layer (1-14, 1-114) and the inner surface of an outer lip portion of the second layer (1-15, 1-115) substantially orthogonal to the surface of the weight (1-3, 1-103).

[0833] FIGS. 27b-e show securing features (1-23b, 1-23c, 1-23d, and 1-23e) in the form of: [0834] a tapered recess and projecting lip portion; [0835] O-ring seal and complementary grooves; [0836] an elastic clip portion and mating recess; [0837] serrated, interlocking portions, also located at the lateral periphery of the first layer (1-14, 1-114) and the inner surface of an outer lip portion of the second layer (1-15, 1-115) substantially orthogonal to the surface of the weight (1-3, 1-103).

[0838] The second layer (1-15, 1-115) is sufficiently flexible such that it can be pressed over the first layer and corresponding securing features (1-23) to become locked in position. Alternatively, where the cushioning slides (1-13, 1-113) are circular the second layer (1-15, 1-115) may be screwed onto the first layer (1-14, 1-114) where a suitable mating thread is provided as per FIG. 27a.

[0839] Yet further variations of securing features (1-23f-1-23k) are shown in FIGS. 28a-f to secure a cushioning slide (1-13) to the narrow side wall (1-9) of a hammer weight (1-3) in a complimentary position to that showed for the embodiment shown in FIGS. 16 and 18a-d.

[0840] FIG. 28a shows an individual first layer (1-14a) and a second layer (1-15e) located at the longitudinal apices (1-20), without any direct physical connection across the narrow side wall (1-9) between adjacent cushioning slides (1-13). The first and second layers (1-14a, 1-15e) are not directly secured to each other and instead, the securing feature (1-230 relies on the physical proximity of the housing inner side walls (1-107) to retain the cushioning slide (1-13) in position.

[0841] FIG. 28b shows a first layer (1-14b) and a second layer (1-15f) located at both the longitudinal apices (1-20) and extending across the width of the narrow side wall (1-9) and part of the wide side walls (1-8). The first and second layers (1-14b, 1-150 are not directly secured to each other and instead, the securing feature (1-23g) relies on the physical proximity of the housing inner side walls (1-107) to retain the cushioning slide (1-13) in position.

[0842] FIG. 28c shows a comparable arrangement of the first layer (1-14b) and a second layer (1-15f) as shown in FIG. 28b). However, the securing feature (1-23h) is provided as protrusions in the second layer (1-15) shaped and positioned to mate with corresponding recesses in the first layer (1-14c) and hammer apices (1-20). The securing feature (1-23h) thus secures the cushioning slide (1-13) to the weight (1-3) by a tab and complementary recess located on the mating surfaces of the first and second layers (1-14c, 1-15g) respectively.

[0843] FIG. 28d also shows a comparable arrangement of the first layer (1-14b) and a second layer (1-15f) as shown in FIG. 28b. The securing feature (1-23i) comprises a screw, fitted through a countersunk aperture in the first layer (1-14d) and through an aperture in the second layer (1-15h) into a threaded hole in the narrow sidewall (1-9).

[0844] FIG. 28e shows a comparable arrangement of the first layer (1-14c) and a second layer (1-150) as shown in FIG. 28b. However, the securing feature (1-23j) instead comprises a cross pin, fitted through apertures in the first layer (1-14e) second layer (1-15i) and weight (1-3) from one wide side wall (1-8) to the opposing side wall (1-8).

[0845] FIG. 28f shows a comparable arrangement to that shown in FIG. 28c with a recess in the hammer weight (1-3) mating with a corresponding tab at the base of the second layer (1-15g, 1-15j). However, the securing feature (1-23k) secures the first layer (1-14j) to the second layer (1-140 in a reverse arrangement, i.e. recesses in the second layer (1-151) mating with corresponding protrusions in the first layer (1-140.

[0846] The above-described cushioning slides (1-13, 1-113) have a UHMWPE first layer (1-14, 1-14a-1-14f, 1-114) and a polyurethane elastomer second layer (1-15, 1-15a-1-15j, 1-115) to provide a relatively lightweight cushioning slide (1-13, 1-113) while providing sufficient shock-absorbing and low-friction capabilities. As discussed above, the high deceleration forces (up to one thousand G) create significant additional forces for any increase in weight of the cushioning slide (1-13, 1-113). Thus, while it is possible to use materials such as steel for the first layer (1-14, 1-114) this configuration would add greater mass by virtue of its higher density and thus have a higher inertia than a UHMEPE first layer (1-14, 1-114) during impacts.

[0847] FIGS. 29a-b show an embodiment of a cushioning slide (1-13) that uses a steel first layer (1-14). FIGS. 29a-b are an exploded and part assembled view of a steel first layer (1-14) and elastomer second layer (1-15). The steel first layer (1-14) has a conventional planar upper surface (1-16) and a lower surface (1-18) formed with one part of a securing feature (1-23m) in the form of a cellular configuration with a plurality of subdividing wall portions projecting orthogonally away from the lower surface (1-18). The second layer (1-15) includes an upper surface (1-17) formed with the complimentary mating part of the securing feature (1-23m) in a cellular configuration projecting orthogonally away from the upper surface (1-17). The first and second layers (1-14, 1-15) interlock with the cellular configurations of the securing feature (1-23m) thereby securing to each other. The plurality of interlocked portions of the steel first layer (1-14) and the elastomer second layer (1-15) creates a strong coupling, highly resistant to separation under the effects of impact forces parallel to the plane of the weight surface (1-21, 121). It will be noted the interlocking securing feature (1-23m) does not extend through the full thickness of the second layer (1-15) to the underside surface (1-19). Instead, a lower portion of the second layer (1-15) positioned between the lower surface (1-19) and the securing feature (1-23m) is used to incorporate a form of displacement void (1-22) for accommodating deflection of the second layer (1-15) material during compression.

[0848] It will be appreciated that any impact forces acting to separate the first layer (1-14, 1-114) from the second layer (1-15, 1-115) also act to separate the whole cushioning slide (1-13, 1-113) from the weight (1-3, 1-103). It also follows that the means of securing the whole cushioning slide (1-13, 1-113) to the weight (1-3, 1-103) against the adverse effects of high acceleration forces need to be even higher than those applied solely to the first layer (1-14, 1-114). Consequently, as shown in FIGS. 18a-22b, 29a-b, and 30a-b, the weight (1-3, 1-103) is provided with a robust means to secure the cushioning slides (1-13, 1-113) to the weight (1-3, 1-103), provided in the form of sockets (1-24, 1-124) on the side walls (1-8, 1-108 and 1-9, 1-109).

[0849] As shown in FIGS. 18a-22b, 29a-b, and 30a-b, the cushioning slides (1-13, 1-113) are located on the weight (1-3, 1-103) in a socket (1-24, 1-124) formed with a retention face (1-25, 1-125) positioned at a cushioning slide perimeter. The retention face (1-25, 1-125) at the cushioning slide perimeter may be located about: [0850] a lateral periphery of; [0851] an inner aperture through, and/or [0852] a recess in, the cushioning slide (1-13, 1-113).

[0853] Each retention face (1-25, 1-125) may be formed as a ridge, shoulder, projection, recess, lip, protrusion or other formation presenting a rigid retention face between one of the weight distal ends (1-10, 1-110, 1-11, 1-111) and at least a portion of the cushioning slide (1-13, 1-113) located in the socket (1-25, 1-125) on a side wall (1-8, 1-9, 1-108, 1-109) of the weight (1-3, 1-103).

[0854] The retention face (1-125) of the wide side wall socket (1-124) shown in FIG. 30a-b is formed as an inwardly tapered wall (1-125) of the socket (1-124) to secure the cushioning slide (1-13, 1-113) to the weight side wall (1-108) from the component of forces substantially orthogonal to the weight side walls (1-108). Other retention features (not shown) could include a reverse taper, upper lip, O-ring groove, threads, or other inter-locking-features with the slide (1-113).

[0855] In the aforementioned embodiments, each socket retention face (1-25, 1-125) may be formed as outwardly or inwardly extending walls extending substantially orthogonal to the corresponding side walls (1-8, 1-9, 1-108, and 1-109).

[0856] In the embodiment shown in FIG. 31 a retention face (1-25, 1-125) is located inside the perimeter of a socket (1-124) in the side wall (1-108) under the second layer (1-15, 1-115) and is formed as an outwardly extending wall thus forming corresponding location projections (1-126). Inwardly extending retention faces (1-125) on the narrow side walls (1-109) form location recesses (1-127) performing the same retention function as the location projections (1-126).

[0857] In the embodiment of FIG. 31, the location projection (1-126) passes through an aperture (1-128) in the second layer (1-115) and an aperture (1-129) in the first layer (1-114). Also shown in FIG. 31, the converse configuration is shown in a separate socket (1-124) where a locating portion (1-130) extends from the lower surface (1-118) of the first layer (1-114) to project though the aperture (1-128) in the second layer into locating recess (1-127).

[0858] The use of a location recess (1-127) or a location projection (1-126) enables a cushioning slide (1-13, 1-113) to be positioned directly adjacent the upper or lower distal face (1-110, 1-111) without a retention face (1-125) surrounding the entire outer periphery of the cushioning slide (1-13, 1-113) as in the embodiments shown in FIGS. 16-19 and FIGS. 21-24.

[0859] It should be appreciated that sockets (1-124) may not be necessary when using such location projections (1-126) or location recesses (1-127). Instead, the cushioning slides (1-113) may lie directly on the outer surfaces (1-108, 1-109) with only the location projections (1-126) or location recesses (1-127) respectively extending outwards or inwards from the corresponding surface (1-108, 1-109).

[0860] FIG. 18d shows a corresponding embodiment applied to the hammer weight (1-3) with a location projection (1-26) passing through an aperture (1-28) in the second layer (1-15) and an aperture (1-29) in the first layer (1-14).

[0861] As previously identified, the greater the separation between the weight (1-3, 1-103) and the housing inner side walls (1-7, 1-107), the greater distance available for the weight to increase lateral speed under the lateral component of force (e.g. gravity), thereby increasing the resultant impact force. The embodiment shown in FIGS. 32 and 33a-b show a pair of cushioning slides (1-113) fitted to an apex (1-120) and a side wall (1-108) of a hammer weight (1-103). The cushioning slides (1-13) incorporate multiple pre-tensioning surface features (1-131, not all labelled) located on: [0862] the first layer lower surface (1-118); [0863] the second layer upper surface (1-117); [0864] the second layer lower surface (1-119), and [0865] the weight side wall surface (1-121) adjacent the underside of the second layer (1-119).

[0866] It will be appreciated however that the pre-tensioning surface features (1-131) need only be formed on one of the above four surfaces to function successfully. In the embodiment shown in FIGS. 32 and 33a-b the pre-tensioning features are small spikes, though alternatives such as fins, buttons, or the like are possible.

[0867] The pre-tensioning features (1-131) are elastic and shaped so that they are more easily compressed than the main planar portion of the second layer (1-115), The pre-tensioning surface features (1-131) also create a spacing between the first (1-114) and second (1-115) layers and between the second layer (1-115) and the corresponding side wall (1-108 or 1-109).

[0868] The pre-tensioning surface features (1-131) are formed to bias the cushioning slide's exterior surfaces (1-116) into continuous contact with the housing inner side walls (1-107) during reciprocation of the weight (1-113). In use, the pre-tensioning features (1-131) are pre-tensioned when the weight (1-103) is laterally positioned equidistantly within the housing inner side walls (1-107), as shown in FIG. 33a.

[0869] The exterior surface (1-116) of first layer (1-114) is thus biased into light contact with the housing inner side walls (1-107) when the housing inner side walls (1-107) is in equilibrium, (as shown in FIG. 33a) e.g. orientated substantially vertical. During operations, any lateral component of a force acting on the weight (1-103) acts to compress the pre-tensioning features (1-131) as shown in FIG. 33b. Any continued compressive force from that point onwards causes the elastomer of the second layer (1-115) to deflect as discussed with respect to the aforementioned embodiments.

[0870] FIGS. 34a-b shows an alternative cushioning slide (1-213) with a first layer (1-214) formed from a disc of metal or plastic with an exterior surface (1-216) and an interior surface (1-218). The interior surface (1-218) is formed by machining out a volume of the disc thickness. The cushioning slide (1-213) could also be a rectilinear or other shape and the disc is just one example. The second layer (1-215) is formed from three sub-layers including an elastomer upper layer (1-231), an intermediate rigid steel or plastic layer (1-232) and a lower elastomer layer (1-233). The second layer (1-215) has an outer surface (1-217) abutting the first layer interior surface (1-218) and a second layer interior surface (1-219) abutting a socket (1-24) in the reciprocating weight (1-3).

[0871] As per the previous embodiments, the layers (1-231, 1-232, 1-233) may be formed with displacement voids to accommodate volume displacement of the elastomer layers (1-231, 1-233) under compression.

[0872] The intermediate rigid layer (1-232) provides a rigid boundary for the elastomer layers (1-231, 1-233) and thereby ensures the elastomer layers deflect laterally under compression. A single, thicker elastomer layer may provide good shock-absorbency but is vulnerable to overheating as the amount of compression and expansion is relatively large compared with multiple thinner layers.

[0873] The upper elastomer layer (1-231) is shaped to provide a pre-tensioning feature for biasing the first layer (1-214) against the housing inner side walls (1-7, 1-107). The pre-tensioning feature is achieved in this example by forming the elastomer layer (1-231) as a bowl with a convex exterior surface (1-217). Alternatively, as in the embodiments shown in FIGS. 32 and 33a-b, pre-tensioning surface features may be utilised such as ridges, fins or other protrusions that push against the first layer (1-214) but compress easier than the elastomer layer (1-231, 1-233).

[0874] The lower elastomer layer (1-233) is also formed with a similar pre-tensioning shape feature and further includes a recess (1-234) for accommodating the peripheral wall (1-235) of the first layer (1-214). The recess (1-234) is sufficiently deep such that when assembled in an uncompressed state (FIG. 33b) the first layer wall (1-235) is not touching the base of the recess (1-234) thereby permitting travel of the first layer (1-214) when the cushioning slide (1-213) is impacted.

[0875] The cushioning slide (1-213) components may be vulnerable to relative sliding between rigid layers (1-214, 1-232) and elastomer layers (1-231, 1-233) when subjected to high accelerations along the impact axis. Any relative sliding may allow the rigid layers (1-232) to move and damage the other layers (1-233, 1-231). Thus, in the embodiment shown in FIGS. 34a-b, the first (1-214) and second (1-215) layers are dimensioned to provide a close-fit when assembled to prevent such problems, such as damage to the contacting edges of the rigid layers (1-232) and (1-214), particularly those resulting from high accelerations along the impact axis.

[0876] The cushioning slide (1-213) is thus formed as a layered stack which offers improved shock-absorbing characteristics over a singular second layer (1-15), (1-115) as in the previous embodiments. The cushioning slide (1-213), while more complex and costly, may be useful in applications in extremely high impact forces where the cushioning slides (1-13), (1-113) are not sufficiently robust. Accordingly, the first layer (1-214) could be formed from steel or plastic with high wear resistance which, while increasing weight offers increased robustness for high shock loads.

[0877] One embodiment of an impact hammer is illustrated by FIGS. 35-37 in the form of a rock-breaking hammer (2-1) including a hammer weight (2-2) constrained to move linearly within a housing (2-3). A striker pin (2-4) is located in a nose cone portion of the housing (2-3) to partially protrude from the housing (2-3). The striker pin (2-4) is an elongate substantially cylindrical mass with two ends, i.e. a driven end (17) impacted by the hammer weight (2-2) and an impact end (18) protruding through the housing (2-3) to contact the rock surface being worked. The housing (2-3) is substantially elongate, with an attachment coupling (2-6) attached to a portion of the housing (2-3), referred to as the nose block (2-5), at one end of the housing (2-3). The attachment coupling (2-6) is used to attach the impact hammer (2-1) to a carrier (not shown) such as a tractor excavator or the like.

[0878] The impact hammer (2-1) also includes a shock absorber in the form of first and second shock absorbing assemblies (2-7a, 2-7b) laterally surrounding the striker pin (2-4) within the nose block (2-5) and interposed by a retainer in the form of recoil plate (2-8).

[0879] The shock-absorbing assemblies (2-7a, 2-7b) and recoil plate (2-8) are held together in the nose block (2-5) as a stack surrounding the striker pin (2-4) by an upper cap plate (2-9) fixed, via longitudinal bolts (2-10), to the nose cone (2-11) portion of the housing (2-3), located at the distal portion of the hammer (2-1), through which the striker pin (2-4) protrudes. The upper cap plate (2-9) is a rigid inelastic plate with a planar lower surface confronting the upper elastic layer (2-12) of the second shock absorbing assembly (2-7b). The nose cone (2-11) is also a rigid fitting with a planar upper surface confronting the lower elastic layer (2-12) of the first shock absorbing assembly (2-7a). The recoil plate (2-8) is formed with rigid parallel upper and lower planar surfaces confronting the lower and upper elastic layers (2-12) of the second (2-7b) and first (2-7a) shock absorbing assemblies respectively. The planar surfaces of the upper cap plate (2-9), recoil plate (2-8) and nose cone (2-11) are substantially parallel, each centrally apertured and aligned to accommodate passage of the striker pin (2-4).

[0880] As may be seen more clearly in FIG. 37, the individual shock-absorbing assemblies (2-7a, 2-7b) are composed of a plurality of individual layers. In the embodiment shown in FIGS. 35-48c, each shock-absorbing assembly (2-7a, 2-7b) is composed of two elastic layers in the form of polyurethane elastomer annular rings (2-12), separated by an inelastic layer in the form of apertured steel plate (2-13). The shock-absorbing assemblies (2-7a, 2-7b) are held between the cap plate (2-9) and nose cone (2-11), though are otherwise unrestrained from longitudinal movement parallel/coaxial to the longitudinal axis of the striker pin (2-4). The above described constituent elements in shock-absorbing assemblies (2-7a, 2-7b), cap plate (2-9) and nose cone (2-11) are not bonded, adhered, fixed, or in any other way connected together aside from being physically held in physical contact.

[0881] The striker pin (2-4) is attached to the impact hammer (2-1) by a slideable coupling in the form of two retaining pins (2-14) passing laterally through the recoil plate (2-8) such that a portion of each pin (2-14) partially projects inwardly into a recess (2-15) formed in the striker pin (2-4). The slideable coupling connects the striker pin (2-4) to the recoil plate (2-8) at a retaining location defined by the length of the recess (2-15) between (with respect to the driven end of the striker pin (2-4)) a distal and proximal travel stops (2-20, 2-21).

[0882] The polyurethane rings (2-12) in each shock-absorbing assembly (2-7a, 2-7b) are held in position perpendicular to the striker pin longitudinal axis by guide elements in the form of elongate slides (2-16), located on the interior walls of the nose block (2-5) and orientated substantially parallel with the striker pin longitudinal axis.

[0883] Each polyurethane ring (2-12) includes small rounded projections (2-17) extending radially outwards from the outer periphery (2-23) in the plane of the polyurethane ring (2-12). The elongate slides (2-16) are configured with an elongated groove shaped with a complementary profile to the projections (2-17) to enable the shock-absorbing assemblies (2-7a, 2-7b) to be held in lateral alignment. This allows the rings (2-12) to expand laterally whilst preventing the polyurethane rings (2-12) from impinging on the inner walls of the housing (2-3), i.e. maintaining the rings (2-12) centered co-axially to the striker pin (2-4), thus preventing any resultant abrasion/overheating damage to the polyurethane ring (2-12).

[0884] The elongate slides (2-16) are generally elongate rectangular panels formed from a similar elastic material to the elastic layer (2-12) e.g. polyurethane. However, preferably, the elongate slides (2-16) are formed from a much softer elastic material, i.e., with a lower modulus of elasticity. This provides two key benefits: [0885] 1. The elongate slides (2-16) wear more readily than the polyurethane annular rings (2-12). Consequently, maintenance costs are reduced as the elongate slides (2-16) may be easily replaced when worn and do not require the removal and dismantling of the shock absorbing assemblies (2-7a, 2-7b) in order to replace the annular rings (2-12) [0886] 2. The elongate slides (2-16) offer virtually no resistance to the lateral deflection of the annular rings (2-12) under load, thus avoiding the projections (2-17) becoming locally incompressible which may lead to failure thereof.

[0887] During a shock absorbing process, as the elastomer ring (2-12) deflects laterally, the projections (2-17) are forced outwards into increasing contact with the elongate slides (2-16) until the pressure reaches a point where the elongate slides (2-16) start to move parallel to the striker pin longitudinal axis in conjunction with the polyurethane ring (2-12).

[0888] As shown most clearly in FIG. 35, each projection (2-17) includes a substantially concave recess (2-19) at the projection apex. Each recess (2-19) is a part-cylindrical section orientated with a geometric axis of revolution in the plane of the elastic layer (2-12). Under compressive load, the vertical centre of the elastic layer (2-12) is displaced laterally outwards by the greatest extent. The recess (2-19) thereby enables the elastic layer (2-12) to expand outwards without causing the centre of the projection (2-17) to bulge beyond the perimeter of the projection (2-17).

[0889] FIGS. 38A-B, 39A-B, and 40A-B respectively show an impact hammer in the form of rock-breaking hammer (2-1) performing an effective strike, a mis-hit and an ineffective strike, both before (FIGS. 38A, 39A, and 40A) and after (FIGS. 38B, 39B, and 40B) the hammer weight (2-2) impacts the striker pin (2-4).

[0890] In typical use (as shown in FIG. 38A-B), the lower tip of the striker pin (2-4) is placed on a rock (2-18) and the hammer (2-1) lowered until the retaining pins (2-14) impinge on the distal travel stop (2-20) of the recess (2-15). This is termed the ‘primed’ position. The hammer weight (2-2) is then allowed to fall onto the upper end of the striker pin (2-4) inside the housing (2-3) and the resultant force transferred through the striker pin (2-4) to the rock (2-18). When the impact results in a successful fracture of the rock (2-18), as shown in FIG. 38B, virtually all of the impact energy from the hammer weight (2-2) may be dissipated and little, if any, force is required to be absorbed by either of the shock-absorbing assemblies (2-7a, 2-7b).

[0891] FIGS. 39A-B show the effects of a ‘mis-hit’ or ‘dry hit’, in which the hammer weight (2-2) impacts the striker pin (2-4) without being arrested by impacting a rock (2-18) or similar. Consequently, all, or a substantial portion of the impact energy of the hammer weight (2-2) is transmitted to the hammer (2-1). The downward force of the hammer weight (2-2) impacting the striker pin (2-4) forces the proximal travel stop (2-21) at the upper end of the recess (2-15) into contact with the retaining pins (2-14). Consequentially, the recoil plate (2-8) is forced downward, thus compressing the lower shock absorbing assembly (2-7a) between the recoil plate (2-8) and the nose cone (2-11). In the process of absorbing the impact shock, the compressive force laterally displaces the polyurethane rings (2-12), orthogonally to the striker pin longitudinal axis. The steel plates (2-13) prevent the polyurethane rings from mutual contact, thereby avoiding wear and also maximizing the combined shock-absorbing capacity of all the elastic polyurethane rings (2-12) in the shock absorbing assembly (2-7a) in comparison to use of a single unitary elastic member.

[0892] A significant degree of heat is generated in a ‘dry hit.’ However, it has been found that even several such strikes successively may avoid permanent damage to the polyurethane rings (2-12) provided a cooling period is allowed by the operator before continuing impact operations. Ideally, deformation of the polyurethane rings (2-12) is less than approximately 30% change in thickness in the direction of the applied force, though this may increase to 50% in a dry hit.

[0893] FIG. 40A-B show the effects of an ineffective hit whereby the impact force of the hammer weight (2-2) on the striker pin (2-4) is insufficient to break the rock causing the striker pin (2-4) to recoil into the housing (2-3) on a reciprocal path. This forces the retaining pins (2-14) into contact with the lowermost ends of the striker pin recesses (2-15). Consequently, the upwards force is transferred via the recoil plate (2-8) to the upper shock absorbing assembly (2-7b) causing the elastic polyurethane rings (2-12) to deflect laterally during absorption of the applied force. Thus, the shock absorbing assembly (2-7b) mitigates the detrimental effects of the recoil force on the hammer (2-1) and/or carrier (not shown).

[0894] FIGS. 41-48c show alternative embodiments, utilizing alternative guide element configurations to that shown in FIGS. 35-37.

[0895] The embodiment as shown in FIGS. 35-37 shows the elongate slide (2-16) guide elements formed with a longitudinal recess and complimentary projections (2-17) formed on the elastic layer. The converse configuration is employed in the embodiment shown in FIGS. 41 and 42, whereby the elongate slides (2-116) are formed with a longitudinal projection (2-1 17) and a portion of a peripheral edge (2-23) of the elastic layer (2-12) is formed as a corresponding recess matching the profile of the projection (2-117) on the elongate slide (2-116). The elongate slides (2-16, 116) in both the first and second embodiments function identically in centring the elastic layers (2-12), as described previously.

[0896] In an alternative embodiment (not shown), the guide elements in the form of elongate slides (2-16, 2-116) may be arranged on the exterior of the striker pin (2-4). It will also be appreciated that the slidable engagement between the elastic layer inner periphery (2-24) and the striker pin (2-4) may be formed by a recess on the elongate slide guide element and a protrusion on the elastic layer periphery (2-24) or vice versa

[0897] FIGS. 43 and 44 show (in side and plan section view respectively) a further preferred embodiment incorporating guide elements in the form of locating pins (2-22). Four equidistantly spaced locating pins (2-22) are located on a planar surface of the inelastic layer (2-13) between an outer (2-23) and inner (2-24) lateral periphery of the elastic layers, orientated substantially parallel with the striker pin longitudinal axis to pass through an elastic layer (2-12).

[0898] The individual pins (2-22) may be formed in a variety of configurations including two locating pins on located on opposing sides of the inelastic layer (2-13) or as a substantially single continuous pin, fixed through the inelastic steel plate (2-13) and passing through the elastic layers (2-12) on both sides. FIG. 43 shows a configuration whereby the locating pins (2-22) are formed as two separate elements, co-axially aligned on opposing sides of the inelastic plate (2-13). It will be appreciated however, that the locating pins (2-22) on either side of the inelastic layer (2-13) do not necessarily need to be aligned, or the same in number.

[0899] The elastic layer (2-12) defects both laterally outwards towards the side walls (2-27) of the nose block (2-5) and inwards towards the striker pin (2-4) under compression. The locating pins (2-22) are positioned at a point on a null-point path (2-25) between the outer (2-23) and inner (2-24) lateral periphery. As this null point (2-25) is laterally stationary during shock absorbing, there is no relative movement between the elastomer layers (2-12) and locating pin guide element (2-22) and therefore no tension, nor compression therebetween. It will be readily appreciated by one skilled in the art that alternative configurations including two or more pins (2-22) may be employed to ensure the centring of the elastic layers (2-12). The null-point path (2-25), including the positions of locating pins (2-22) (as shown in FIG. 43) are located on a generally annular null-point path (2-25) located between the outer and inner periphery (2-23, 2-24).

[0900] FIGS. 45 and 46 show a further embodiment incorporating guide elements in the form of tension bands (2-26) circumscribing each elastic layer (2-12) and four anchor points (2-29) in the form of nose block longitudinal bolts (2-10) located centrally adjacent each of the four nose block side walls (2-27). A separate tension band (2-26) is provided for each elastic layer (2-12) and applies a restorative reaction force caused by displacement of the elastic layer (2-12) from its centred position about the striker pin (2-4). It will be appreciated however that the tension bands (2-26) may be configured to pass around a differing number of anchor points (2-29) and/or other portions of, or attachments to the nose block side walls (2-27) as well as the corresponding elastic layers (2-12).

[0901] The tension band (2-26) may also be formed of an elastic material such as an elastomer. The portion of the tension band (2-26) passing behind each anchor point (2-29) passes through a shallow indent (2-28) in the adjacent nose block side wall (2-27), thereby preventing the band (2-26) from sliding or rolling up or down the nose bolts (2-10) during use.

[0902] The centering force applied by the tension bands (2-26) onto the elastic layer (2-12) is proportional to the degree the band (2-26) is displaced from the direct path between adjacent anchor points (2-29) by the outer periphery (2-23) of the elastic layer (2-23). The symmetrical arrangement of the anchor points (2-29) and the elastic layer (2-23) about the striker pin longitudinal axis produces a centering force about same.

[0903] FIGS. 47 and 48a show a yet further embodiment incorporating guide elements in the form of supported stabilizing features (2-30) projecting directly from the elastic layer outer periphery (2-23) to contact the nose block side walls (2-27). The planar surfaces of the inelastic layer (2-13) are formed with a substantially square centre section and four tab portions (2-31) located at the four apices of the centre squares outer periphery (2-23). The tab portions (2-31) located at each apex of the inelastic layer (2-13) pass between adjacent nose bolts (2-10) to within close proximity of the nose block side wall (2-27). The stabilizing features (2-30) projecting from the outer periphery (2-23) roughly mirror the shape of the inelastic layer outer periphery (2-34) with a border to allow for lateral deflection during impacting use. Where the tab portions (2-31) are within the closest proximity to the nose block side wall (2-27), the stabilizing features (2-30) are sufficiently close to contact the sidewalls during impacting use, to provide a centering and stabilizing effect. As the remainder of the elastic layer (2-12), including the stabilizing features (2-30), are supported by the inelastic layer (2-13), the potential for damaging wear on the elastic layer (2-12) is mitigated.

[0904] FIGS. 48b and 48c illustrate a fifth and sixth embodiments incorporating variants of the embodiment shown in FIG. 48a and showing an enlargement of the side elevation taken along section line AA of the supported stabilizing feature (2-30) adjacent the nose block side wall (2-27).

[0905] FIG. 48b shows a pair of elastic layers (2-12) interleaved by an inelastic layer (2-13) with an outer periphery tapered portion (2-36) extending to the peripheral edge (2-34) on the upper and lower surface of the inelastic layer (2-13).

[0906] FIG. 48c shows an inelastic layer (2-13) interleaved between a pair of elastic layers (2-12), each with outer peripheries having tapered portions (2-37) extending to the peripheral edge (2-23) on the surfaces of the elastic layers (2-12) adjacent the inelastic layer (2-13).

[0907] The embodiment of FIG. 48b produces a reduce pressure during compression reduction at the outer periphery tapered portions (2-37) by reducing the volume of the rigid inelastic layer (2-13) compressing the adjacent elastic layers (2-12).

[0908] The reduction in the volume of elastic layers (2-12) material caused by the tapered portions (2-37) with respect to the embodiments cause shown in FIG. 48c is directly comparable to the effect to that of the part-cylindrical section recess (2-19) described with respect to FIG. 35.

[0909] Over continued use, the sides of the striker pin (2-4) wear the cap plate (2-9) and nose plate (2-11) where it passes through the nose block (2-5). Consequently, the striker pin's longitudinal axis becomes misaligned from the impact axis (2-100), bringing the shock absorbing assemblies (2-7a, 2-7b) closer to the nose block walls (2-27). To prevent a detrimental contact between the shock absorbing assemblies (2-7a, 2-7b) and the nose block walls (2-27), a degree of lateral clearance (2-32) is incorporated between either the striker pin (2-4) and the inner inelastic layer periphery (2-35) or the nose block side walls (2-27) and the outer inelastic layer periphery (2-34) (as shown in FIG. 42). The impact hammer (2-1) may thus accommodate a degree of wear before maintenance is required for the cap plate (2-9) and nose plate (2-11).

[0910] Although the inelastic layer (2-13) is thus centred by its proximity to the circumference of the striker pin (2-4), the inelastic layer (2-13) may rotate about the striker pin (2-4) during use due to its uniform inner circular cross section. Thus, to prevent any detrimental interference between the inelastic layer (2-13) and the nose block side walls (2-27) and/or nose bolts (2-10), the inner nose block walls (2-27) are provided with a pair of substantially elongated cuboid restraining elements (2-33), placed between a pair of nose bolts (2-10) and extending laterally inwards toward the striker pin (2-4). The restraining elements (2-33) are positioned and dimensioned to be sufficiently close to the inelastic layer (2-13) to obstruct any rotation, whilst permitting movement parallel to the longitudinal impact axis (2-100). It should be noted that although the striker pin longitudinal axis and the impact axis (2-100) may diverge slightly due to wear, all the figures show the situation with no wear and thus the two axes are co-axial.

[0911] In an alternative embodiment (not shown), the inelastic layer (2-12) is configured with its outer periphery (2-34) positioned immediately adjacent at least a portion of the nose block walls (2-27) and/or nose bolts (2-10), with a clearance spacing between the inner inelastic layer periphery (2-24) and the striker pin (2-4).

[0912] Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

[0913] It should be appreciated that the disclosure herein encompasses embodiments where any one or more of the features, components, methods or aspects, either individually, partially or collectively of any one embodiment or aspect may be combined in any way with any other feature of any other embodiment or aspect and the disclosure herein does not exclude any possible combination unless explicitly stated otherwise.

Appendix a

[0914] Tables 1-14.

TABLE-US-00002 TABLE 1 Minimum Minimum attachment weight weight reduction Max reduction to required as attachment move into percentage weight lighter of lightest Excavator (6.5x excavator attachment in weight class multiplier) class excavator (tonnes) (tonnes) (tonnes) class 20-25 3.1-3.8 30-36 4.6-5.5 0.8 17% 40-55 6.2-8.5 0.7 11% 65-80   10-12.3 1.5 15% 100-120 15.4-18.5 3.1 20%

TABLE-US-00003 TABLE 2 Gravity Gravity Gravity Gravity Prior-Art gravity-only impact hammers: hammer 1 hammer 2 hammer 3 hammer 4 fixed drop height & hammer weight mass DX900 SS80 DX1800 SS150 Overall hammer weight (including bracket), kg 5500 9000 10500 13000 Carrier weight, kg 36,000 60,000 65,000 80,000 Carrier cost, $ 225,000 375,000 400,000 500,000 Impact energy vertical, joules 90,000 100,000 180,000 180,000 Impact energy at 45º, joules 52,376 58,196 104,753 104,753 Energy/kg of carrier weight, joules per kilo 2.5 1.7 2.8 2.3 Work done per blow vertical (=Energy.sup.1.3) 2,757 3,162 6,790 6,790 Work done per blow at 45º (=Energy.sup.1.3) 1,364 1,564 3,359 3,359 Cycles per minute 12 12 12 12 Equivalent production tonnes per hour vertical 65 75 161 161 Equivalent production tonnes per hour at 45º 32 37 80 80 Carrier cost per tonne per hour of production, vertical 3440 5000 2484 3105 Carrier cost per tonne per hour of production, at 45º 6954 10107 5021 6276

TABLE-US-00004 TABLE 3 Vacuum Vacuum Vacuum Vacuum Assisted Impact Hammers: hammer 1 hammer 2 hammer 3 fixed drop height & hammer weight mass XT1000 XT2000 XT4000 Overall hammer weight (including bracket), kg 3600 6000 11000 Carrier weight, kg 22,500 40,000 68,000 Carrier cost, $ 150,000 250,000 440,000 Impact energy vertical, joules 100,000 210,000 440,000 Impact energy at 45º, joules 95,317 200,165 419,394 Energy/kg of carrier weight, joules per kilo 4.4 5.3 6.5 Work done per blow vertical (=Energy.sup.1.3) 3,162 8,296 21,701 Work done per blow at 45º (=Energy.sup.1.3) 2,971 7,795 20,390 Cycles per minute 16 16 15 Equivalent production tonnes per hour vertical 100 262 643 Equivalent production tonnes per hour at 45º 94 246 604 Carrier cost per tonne per hour of production, vertical 1500 953 684 Carrier cost per tonne per hour of production, at 45º 1597 1014 728

TABLE-US-00005 TABLE 4 Gravity Gravity Gravity Gravity Comparison: fixed impact hammer hammer 1 Vacuum hammer 2 Vacuum hammer 3, Vacuum hammer 4 Vacuum weight, vertical. DX90C hammer 1 SS80 hammer 2, DX1800 hammer 3, SS150 hammer 4, Overall hammer weight incl bracket, kg 5500 5500 9000 9000 10500 10500 13000 13000 Carrier weight, kg 36,000 36,000 60,000 60,000 65,000 65,000 80,000 80,000 Carrier cost, $ 225,000 225,000 450,000 450,000 450,000 450,000 600,000 600,000 Impact energy vertical, joules 90,000 185,000 100,000 360,000 180,000 410,000 180,000 550,000 Impact energy at 45º, joules 52,376 176,336 58,196 343,141 104,753 390,799 104,753 524,243 Energy/kg of carrier weight, joules per kilo 2.5 5.1 1.7 6.0 2.8 6.3 2.3 6.9 Work done per blow vertical (Energy.sup.1.3) 2,757 7,036 3,162 16,718 6,790 19,798 6,790 29,005 Work done per blow at 45º (Energy.sup.1.3) 1,364 6,611 1,564 15,708 3,359 18,601 3,359 27,252 Cycles per minute 12 20 12 18 12 18 17 Equivalent production tonnes per hour 63 268 72 573 155 678 155 939 vertical Equivalent production tonnes per hour at 31 252 36 538 77 637 77 882 45º Carrier cost per tonne per hour of 3571 840 6229 785 2901 663 3868 639 production, vertical Carrier cost per tonne per hour of 7219 894 12590 836 5864 706 7818 680 production, at 45º

TABLE-US-00006 TABLE 5 Gravity Gravity Gravity Gravity Comparison: fixed impact hammer hammer 1 Vacuum hammer 2 Vacuum hammer 3, Vacuum hammer 4 Vacuum energy per blow, vertical. DX90C hammer 5, SS80 hammer 6, DX1800 hammer 7, SS150 hammer 8, Overall hammer weight incl bracket, kg 5500 3200 9000 3600 10500 5500 13000 5500 Carrier weight, kg 36,000 21,000 60,000 22,500 65,000 36,000 80,000 36,000 Carrier cost, $ 225,000 130,000 450,000 140,000 450,000 235,000 600,000 235,000 Impact energy vertical, joules 90,000 90,000 100,000 100,000 180,000 180,000 180,000 180,000 Impact energy at 45º, joules 52,376 85,785 58,196 95,317 104,753 171,570 104,753 171,570 Energy/kg of carrier weight, joules per kilo 2.5 4.3 1.7 4.4 2.8 5.0 2.3 5.0 Work done per blow vertical (energy.sup.1.3) 2,757 2,757 3,162 3,162 6,790 6,790 6,790 6,790 Work done per blow at 45º (energy.sup.1.3) 1,364 2,591 1,564 2,971 3,359 6,379 3,359 6,379 Cycles per minute 12 20 12 20 12 20 12 20 Equivalent production tonnes per hour 63 105 72 120 155 259 155 259 vertical Equivalent production tonnes per hour at 31 99 36 113 77 243 77 243 45º Carrier cost per tonne per hour of 3571 1238 6229 1163 2901 909 3868 909 production, vertical Carrier cost per tonne per hour of 7219 1318 12590 1237 5864 967 7818 967 production, at 45º

TABLE-US-00007 TABLE 6 Gravity Gravity Gravity Gravity hammer 1 Vacuum hammer 2 Vacuum hammer 3, Vacuum hammer 4 Vacuum Comparison: fixed productivity, vertical DX90C hammer 9, SS80 hammer 10, DX1800 hammer 11, SS150 hammer 12, Overall hammer weight (inc. bracket), kg 5500 2300 9000 2500 10500 3900 13000 3900 Carrier weight, kg 36,000 15,000 60,000 16,000 65,000 25,500 80,000 25,500 Carrier cost, $ 225,000 90,000 450,000 100,000 450,000 160,000 600,000 160,000 Impact energy vertical, joules 90,000 61,000 100,000 67,000 180,000 121,500 180,000 121,500 Impact energy at 45º, joules 52,376 58,143 58,196 63,862 104,753 115,810 104,753 115,810 Energy/kg of carrier weight, joules per kilo 2.5 4.1 1.7 4.2 2.8 4.8 2.3 4.8 Work done per blow vertical (energy1.3) 2,757 1,663 3,162 1,879 6,790 4,073 6,790 4,073 Work done per blow at 45º (Energy1.3) 1,364 1,563 1,564 1,765 3,359 3,827 3,359 3,827 Cycles per minute 12 20 12 20 12 20 12 20 Equivalent production tonnes per hour 63 63 72 72 155 155 155 155 vertical Equivalent production tonnes per hour at 31 60 36 67 77 146 77 146 45º Carrier cost per tonne per hour of 3571 1421 6229 1398 2901 1032 3868 1032 production, vertical Carrier cost per tonne per hour of 7219 1513 12590 1488 5864 1098 7818 1098 production, at 45º

TABLE-US-00008 TABLE 7 Excavator weight class Impact Energy (Joules) Vertical impact axis (tonnes) 90,000 100,000 180,000 210,000 400,000 20-25 XT 1000 (22.5T) 30-36 DX900 (36T) 40-55 XT2000 (40T) 65-80 (SS80 60T) DX1800 XT 4000 (65T) (80T) SS150 (80T) 100-120

TABLE-US-00009 TABLE 8 Gravity- vacuum- only assisted impact impact % hammer hammer difference vertical impact axis: Hammer weight, kg 1,000 330 drop height, m 3 3 Energy from weight, Joules; 30,000 10,000 kg × drop × 10 Vacuum assistance, kg ~ 670 Vacuum stroke length ~ 3 Energy from vacuum, Joules; ~ 20,000 kg × stroke × 10 Theoretical energy total, Joules 30,000 30,000 Friction losses 3,000 1,000 Air displacement losses 1,500 600 Total losses Joules 4,500 1,600 Net energy after losses, Joules 25,500 28,400 111% Work done, = net energy.sup.1.3 535,183 615,622 115% 45º impact axis Hammer weight, kg 1,000 330 drop height, m 2.12 2.12 Energy from weight, Joules; 21,200 7,070 kg × drop × 10 Vacuum assistance, kg ~ 670 Vacuum stroke length ~ 3 Energy from vacuum, Joules; ~ 20,000 kg × stroke × 10 Theoretical energy total, Joules 21,200 27,070 Friction losses 5,300 1,750 Air displacement losses 1,060 600 Total losses Joules 6,360 2,350 Net energy after losses, Joules 14,840 24,720 167% Work done, = net energy.sup.1.3 264,767 514,000 194%

TABLE-US-00010 TABLE 9 Impact Gravity- Vacuum- Hammer type only Assisted Stopping Distance(mm) from 1 ms.sup.−1 50 0.02 from 2 ms.sup.−1 190 0.07 from 3 ms.sup.−1 420 0.15 from 4 ms.sup.−1 740 0.27 from 5 m/sec 0.42 Stopping time(s) from 1 ms.sup.−1 0.09 0.034 from 2 ms.sup.−1 0.19 0.068 from 3 ms.sup.−1 0.28 0.102 from 4 ms.sup.−1 0.37 0.136 from 5 m/sec 0.170 Lift time for 5 m 1.53 stroke at 3 ms.sup.−1(s) Lift time for 5 m 0.92 stroke at 5 ms.sup.−1(s) Drop time for 5 m stroke(s) 1.06 0.59 Dwell and acceleration 0.4 0.4 at bottom(s) Minimum practical 3.44 1.91 cycle time(s)

TABLE-US-00011 TABLE 10 Attachment weight weight Max reduction to reduction as attachment move into percentage weight lighter of heaviest Excavator (6.5x excavator in prior weight class multiplier) class excavator (tonnes) (tonnes) (tonnes) class 20-25 3.07-3.84 30-36 4.62-5.54 2.47 44.6% 40-55 6.15-8.46 3.84 45.4% 65-80   10-12.31 6.16 50.0% 100-120 15.38-18.46 8.46 45.8%

TABLE-US-00012 TABLE 11 Vacuum Gravity Gravity Comparison: Similar productivity, hammer hammer hammer tonnes per hour. XT1200 DX1800 SS150 Overall impact hammer weight including bracket 3900 10500 13000 Carrier weight 25,500 65,000 80,000 Carrier cost 160,000 450,000 600,000 Impact energy vertical joules 120,000 180,000 180,000 Impact energy at 45ºjoules 114,380 104,753 104,753 Energy/kg of carrier weight 4.7 2.8 2.3 Work done per blow vertical (Energy.sup.1.3) 4,008 6,790 6,790 Work done per blow at 45º 3,766 3,359 3,359 Cycles per minute 20 12 12 Equivalent production tonnes per hour vertical 152 155 155 Equivalent production tonnes per hour at 45º 143 77 77

TABLE-US-00013 TABLE 12 Vacuum Vacuum Gravity Gravity hammer hammer hammer hammer 3 m 4.24 m 2 m 2.82 m Comparison: Fixed head-height available for stroke stroke stroke, stroke, working, and fixed weight of impact hammer. vertical 45º vertical 45º Overall impact hammer weight including bracket 6000 6000 6000 6000 Carrier weight 40,000 40,000 40,000 40,000 Drop height of weight 3.0 4.24 2.0 2.82 Mass of drop weight 1,000 1,000 2,000 2,000 Effect of vacuum (tonnes force) 3,000 3,000 0 0 Effect of angle (on drop weight only, not vacuum) 0 0.71 0 0.71 Effect of friction and air bypass 0.9 0.9 0.85 0.82 Impact energy joules 105,948 138,509 33,354 32,212 Work done per blow (Energy.sup.1.3) 3,409 4,830 759 725 Cycles per minute 20 16 15 12 Equivalent production tonnes per hour 129 147 22 17

TABLE-US-00014 TABLE 13 Vacuum Gravity Comparison: Similar impact hammer hammer hammer weight and carrier weight. XT2000 DX900 Overall impact hammer weight 6000 5500 Carrier weight 40,000 36,000 Carrier cost 250,000 225,000 Impact energy vertical joules 210,000 90,000 Impact energy at 45º joules 200,165 52,376 Energy/kg of carrier weight 5.3 2.5 Work done per blow vertical (Energy.sup.1.3) 8,296 2,757 Work done per blow at 45º 7,795 1,364 Cycles per minute 20 12 Equivalent production tonnes per hour vertical 315 63 Equivalent production tonnes per hour at 45º 296 31

TABLE-US-00015 TABLE 14 Accumulator performance variables System Requirements Accumulator configuration comment Very low pressure gain of Large volume of accumulator provides most constant accumulator working gas in relative to working volume power output first fluid chamber (3-8) High pressure systems Area of third piston face (3-13) Volume of first fluid is smaller than area of first chamber (3-8) needs to piston face (3-9) be large Low pressure systems Are of third piston face (3-13) is similar to area of first piston face (3-9) Long period to charge Large working gas volume in Typical reciprocating accumulator with unutilised first fluid chamber (3-8) can be cylinder application capacity (i.e. long scavenge at low pressure or excess can where return speeds period) be dumped need to be constrained- produces maximum power gain short period to charge small working gas volume in Typical regeneration accumulator with unutilised first fluid chamber (3-8) at high circuit for an excavator capacity (i.e. short scavenge pressure or the like period) Large difference between Large working volume, can be Maximum power gain scavenge pressure and pump at low pressure or excess can pressure be dumped Small additional power Second piston face (3-12) can Accumulator is small requirement be small relative to third piston and economical face (3-13) with a short stroke Large additional power Third fluid chamber (3-11) must Large power gain-high requirement be large, scavenge time must benefit from accumulator be long with low pressure requirement, area of second piston face (3-12) small relative to area of third piston face (3-13) Power delivered mainly as A large third fluid chamber Needs long scavenge extra hydraulic fluid flow (3-11) and a small second piston time face (3-12) area relative to area of third piston face (3-13) Power delivered mainly as Area of second and third piston extra pressure face as large as possible