CENTRIFUGAL BRAKE MECHANISM

Abstract

A centrifugal brake mechanism for a controlled descent device, and a drum device employing it, are described. The mechanism comprises a circular wheel configured and operable to rotate about an axis of rotation thereof, an axle extending along and rotatable about the axis inside a central cavity of the wheel and having two or more parallel shaft rods extending inside the cavity substantially perpendicular to the axis of rotation, a gear system for transferring rotations of the wheel into counter-rotations of the axle, one or more brake elements each having pass-through bores for slidably mounting over the two or more parallel shaft rods, springs mounted over the parallel shaft rods between the brake element and the axle, and a friction enhancement mechanism for increasing friction forces between the brake elements and the inner wall the wheel responsive to increase in angular velocity of the wheel.

Claims

1-17. (canceled)

18. A centrifugal brake mechanism for a controlled descent device, the centrifugal brake mechanism being configured to be attached to a harness wearable by a descending user, the centrifugal brake mechanism comprising: a support structure configured for attachment to the harness; a circular wheel located inside said support structure and configured and operable to rotate about an axis of rotation thereof, said circular wheel comprising a circular central cavity and an inner wall encircling the cavity; an axle mounted inside said central cavity, the axle extending along and rotatable about said axis of rotation inside said central cavity; two or more parallel shaft rods attached to the axle and extending substantially perpendicular to the axis of rotation inside the cavity; a gear system configured and operable to transfer rotations of said wheel into counter-rotations of said axle; one or more brake elements mounted on said two or more parallel shaft rods, each of the one or more brake elements having two or more pass-through bores for slidably moving along said two or more parallel shaft rods inside said central cavity, and two or more springs mounted over at least one of said shaft rods between the brake element and the axle, said one or more brake elements being configured and operable to radially slide over the two or more parallel shaft rods towards the inner wall of the wheel encircling said cavity in response to the counter-rotations of said axle; and a friction enhancement mechanism for increasing friction forces responsive to increase in angular velocity of the wheel, said friction enhancement mechanism being configured for providing additional engagement between the circular wheel and the brake element and comprising one or more circular rails and corresponding one or more curved grooves engageable with said one or more rails, to thereby progressively increase friction between said one or more brake elements and the inner wall of the wheel responsive to increase in angular velocity of the wheel.

19. The centrifugal brake mechanism of claim 18 wherein the one or more curved grooves form shoulder structures in the outer faces of the one or more brake elements, and each of the one or more circular rails is formed by two circular grooves formed in the inner wall, each of the two circular grooves being configured and operable to receive one of said shoulder structures of the one or more brake elements when said brake element contacts the inner wall, to thereby increase the applied friction forces.

20. The centrifugal brake mechanism of claim 18 wherein geometrical shapes of at least one of the curved grooves and of a respective one of the one or more circular rails configured to be received in it, are adapted to progressively increase the friction forces responsive to increase in angular velocity of the wheel.

21. The centrifugal brake mechanism of claim 20 wherein at least one of the one or more curved grooves comprises a tapering groove section in which opposing sides of the tapering groove taper towards the axis of rotation, and at least one of the one or more circular rails comprises a corresponding tapering rail section configured to be received inside said tapering groove section.

22. The centrifugal brake mechanism of claim 18 wherein the gear system includes a planetary gear system configured and operable to rotate the axle during rotation of the wheel in an angular velocity whose magnitude is greater than the magnitude of the angular velocity of the wheel.

23. The centrifugal brake mechanism of claim 22 wherein a speed ratio of the planetary gear system is about 1 to 5.3.

24. A drum device for controlled release of a cable spooled therein and anchored to an external support by a free end of said cable, said drum device is configured and operable to be harnessed to a descending user for guaranteeing continuous descent of the user while preventing suspension trauma, the drum device comprising the brake mechanism according to claim 18, and the support structure of the drum device has a cable release opening for passage of released cable portions therethrough.

25. The drum device of claim 24, further comprising a cable-release system configured and operable to receive released cable portions from the circular wheel and direct the released cable portions in an outward direction towards the cable release opening of the drum device, and prevent backward movement of the released cable into the housing.

26. The drum device of claim 25 wherein the cable-release system comprises a first cable-release unit mounted above the circular wheel and having a slender opening defined between two rotatable roller shafts thereof for passage of the released cable portions therethrough.

27. The drum device of claim 26 wherein diameters of the two rotatable roller shafts of the first cable-release unit are substantially different, and wherein the diameter of one of said rotatable roller shafts is set according to a predetermined bend radius of the cable.

28. The drum device of claim 26 wherein the cable-release system comprises at least one additional cable-release unit having a slender opening defined between two rotatable roller shafts for passage of the released cable portions therethrough, said at least one additional cable-release unit being mounted above and substantially in parallel to the first cable-release unit.

29. The drum device of claim 28 wherein the orientation of the two rotatable roller shafts of the first cable-release unit is substantially perpendicular to orientation of the two rotatable roller shafts of the at least one additional cable-release unit.

30. A controlled descent device, comprising: a wearable harness; a support structure attached to the harness and having a cable release opening for passage of portions of a spooled cable therethrough; and a drum device comprising the spooled cable and a brake mechanism configured to regulate the speed release of the cable from the drum device, said brake mechanism comprises: a circular wheel configured to rotate about an axis of rotation thereof and comprising a circular central cavity; an axle extending along and rotatable about said axis of rotation inside said central cavity; two or more parallel shaft rods attached to the axle and extending substantially perpendicular to the axis of rotation inside the cavity; a gear system configured to transfer rotations of said wheel into counter-rotations of said axle; and one or more brake elements mounted on said two or more parallel shaft rods, each of the one or more brake elements having two or more pass-through bores for slidably moving along said two or more parallel shaft rods inside said central cavity, and two or more springs mounted over at least one of said two or more parallel shaft rods between the brake element and the axle, said one or more brake elements being configured and operable to radially slide over the parallel shaft rods towards the inner wall of the wheel encircling said cavity in response to the counter-rotations of said axle.

31. The controlled descent device of claim 30, further comprising a friction enhancement mechanism for increasing friction forces responsive to increase in angular velocity of the wheel, said friction enhancement mechanism being configured for providing additional engagement between the circular wheel and the brake element and comprising one or more circular rails and corresponding one or more curved grooves engageable with said one or more rails, to thereby progressively increase friction between said brake elements and the inner wall of the wheel responsive to increase in angular velocity of the wheel and prevent suspension trauma.

32. The controlled descent device of claim 30, further comprising a cable-release system configured to receive released cable portions from the circular wheel and direct the released cable portions in an outward direction towards the cable release opening of the drum device, and prevent backward movement of the released cable into the housing.

33. The controlled descent device of claim 32 wherein the cable-release system comprises first and second cable-release units mounted in parallel above the circular wheel, each of the first and second cable-release units having a slender opening defined between two rotatable roller shafts thereof for passage of the released cable portions therethrough.

34. The controlled descent device of claim 33 wherein the orientation of the rotatable roller shafts of the first cable-release unit is substantially perpendicular to orientation of the rotatable roller shafts of the second cable-release unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings. Features shown in the drawings are meant to be illustrative of only some embodiments of the invention, unless otherwise implicitly indicated. In the drawings like reference numerals are used to indicate corresponding parts, and in which:

[0030] FIG. 1 exemplifies use of a CDD by a rescuee descending from a multi-storied building according to some possible embodiments;

[0031] FIG. 2 shows a perspective view of a drum device of the CDD according to some possible embodiments;

[0032] FIG. 3 shows a perspective view of the drum device without one of its covering plates;

[0033] FIG. 4 shows a sectional view of the drum device without its covering plate;

[0034] FIGS. 5A and 5B are exploded views showing internal components of the drum device from two different sides thereof;

[0035] FIG. 6 shows an elevated perspective view of a cable reel of the drum device and internal components thereof mounted thereinside;

[0036] FIG. 7 shows a top perspective view of the drum device without one of its side cover plates and the cable reel;

[0037] FIG. 8 shows a sectional side view of the inner wall of the cable reel and of a brake shoe according to some possible embodiments;

[0038] FIG. 9 shows a perspective view of a possible arrangement of the drum device according to some possible embodiments; and

[0039] FIGS. 10A and 10B show another possible embodiment of the drum device, wherein FIG. 10A is a perspective view of the drum device accommodated inside housing and FIG. 10B shows an exploded perspective view of the drum device without the housing.

DETAILED DESCRIPTION OF EMBODIMENTS

[0040] The various embodiments of the present invention are described below with reference to the drawings, which are to be considered in all aspects as illustrative only and not restrictive in any manner Elements illustrated in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. This invention may be provided in other specific forms and embodiments without departing from the essential characteristics described herein.

[0041] FIG. 1 exemplifies use of a CDD 9 according to some possible embodiments. In this non-limiting example, a rescuee 7 escaping a high structure 3 (e.g., building) safely descends from the structure by controlled release of a cable 4 spooled in the CDD 9. The CDD 9 comprises a harness 6 (e.g., type of adjustable quick fit harness) worn by the rescuee 7, and a drum device 5 attached to the backside (back piece) of the harness 6, at the upper back area of the rescuee 7 (e.g., between the shoulder blades of the rescuee 7). The drum device 5 includes a spooled cable 4, a cable drum (also referred to herein as cable reel) 47 on which the cable 4 is spooled, and a centrifugal brake mechanism 5m configured to regulate the rate of cable release from the drum device 5 and thereby guarantee safe descent of the rescuee 7 to the ground 2. The spooled cable 4 is attached at one end to the cable reel 47 and includes an anchor fastener 4h (e.g., a snap hook) attached to its free end.

[0042] As shown in FIG. 1, in order to escape the structure 3 (e.g., in an emergency situation, such as spreading fire) the rescuee 7 wears the harness 6, secures the anchor fastener 4h to an anchor member 3r, preferably an anchor fixture fixedly attached to the structure 3 (e.g., anchor ring), and exits the structure 3 e.g., through an opening 3w such as a window, exit/escape door, or the like. After exiting the structure 3 the rescuee 7 is pulled downwardly by gravity (shown by arrow 1) towards the ground 2 and the spooled cable 4 is progressively released from the drum device 5 as the rescuee 7 descends downwardly towards the ground 2. In this non-limiting example the harness 6 and drum device 5 arrangement guarantees that orientation of the body of the rescuee 7 during the fall is substantially vertical relative to the ground 2. The brake mechanism 5m provided in the drum device 5 is configured to controllably release the spooled cable 4 within predefined release speed rates and thereby maintain a substantially controlled descent speed (e.g., of about 0.7 to 2 m/sec for a rescuee weight between 30 to 135 Kg) of the rescuee 7, until safely reaching the ground 2.

[0043] The CDD 9 shown in FIG. 1 exemplifies a possible embodiment wherein the drum device 5 is mounted substantially perpendicular to a back piece of the harness 6, such that the plane of rotation of the cable reel 47 substantially resides in (or parallel to) a median plane of the rescuee 7. It is however noted that other arrangements of the harness 6 and the drum device 5 are also possible, without departing from the scope and spirit of the present invention. For example, and without being limiting, in some possible embodiments the drum device 5 may be mounted substantially parallel to the back piece (i.e., such that the plane of rotation of the cable reel 47 is substantially parallel to a frontal plane of the rescuee 7) and/or over a lower back area of the harness (e.g., below the shoulder blades of the user). Alternatively, in some possible embodiments the drum device 5 is mounted over a frontal piece of the harness such that the rotation plane of the cable reel 47 is substantially parallel (or perpendicular) to a frontal plane of the rescuee 7.

[0044] FIG. 2 shows a perspective view of the drum device 5 according to some possible embodiments. In this non-limiting example the drum device 5 comprises a cable reel 47 mechanically coupled to an axle (shaft) 60 passing along the axis of rotation 47a of the cable reel 47. The axle 60 is operably mounted for rotation inside a support structure 45 of the drum device 5. The support structure 45 comprises two tear-shaped side cover plates, 45f and 45r, and upper and lower support elements (e.g., rods), 45b and 45a, respectively, fixedly attached at their ends to the cover plates, 45f and 45r. The length of the support elements, 45b and 45a, is configured to define a gap g between the two side cover plates, 45f and 45r, sufficiently wide to accommodate the cable reel 47 and permit free undisturbed rotations thereof inside the support structure 45. The extremities of the axle 60 are attached to the side cover plates 45f and 45r by bearings 45x allowing it to freely rotate inside the support structure 45 in a plane of rotations being substantially parallel to the side cover plates.

[0045] The upper portion of the tear-like shaped support structure 45 includes a cable release mechanism for directing the release of the cable 4 from the drum device 5 and preventing backward movement of the cable 4 into the support structure. In this non-limiting example the cable release mechanism comprises two cable release units, 48 and 49, accommodated one on top of the other between the upper portions of the cover plates, 45f and 45r. The cable release units 48 and/or 49 are configured and operable to direct the cable release in an outward direction towards a cable release opening Pc of the drum device 5, and prevent backward movement of the released cable 4 into the drum device 5. In this specific and non-limiting example the cable release opening Pc is defined by an opening of the upper cable release unit 48.

[0046] As best seen in FIG. 3, the bottom cable release mechanism 49 comprises two roller shafts rotatably mounted one parallel to the other between, and perpendicular, to the cover plates 45f and 45r. As demonstrated in FIG. 3, in possible embodiments the two rollers shafts of the bottom cable release mechanism 49 are of different diameters and are configured to provide a desired bend radius. For example, and without being limiting, for a cable 4 having a diameter of about 3 mm and a bend diameter of about 32 mm, a first roller shaft 49u of the bottom cable release mechanism 49 may be of a smaller diameter (e.g., about 16 mm) relative to a second roller shaft 49v thereof having a greater diameter (e.g., about 32 mm). The parallel roller shafts 49u and 49v are mounted slightly spaced-apart above the cable reel 47, leaving a slender gap between them sufficient for passage of the cable 4 therethrough, while contacting the roller shafts and rotating them in predetermined directions due to friction forces evolving therebetween.

[0047] The parallel roller shafts, 49u and 49v, may be configured to prevent movement of the cable (4) towards the cable reel 47 (i.e., to prevent the cable from returning back into the support structure 45), for example and without being limiting, by using a ratchet mechanism (not shown) configured to prevent rotation of the shaft rollers in a counter direction. Additionally or alternatively, backward movement of the cable 4 into the support structure may be prevented by properly setting the elasticity of the cable 4 to a desired suitable level for allowing cable deformations to occur when passing through the slender gap between the roller shafts and quick restoration of its shape upon leaving the roller shafts, and/or by applying adhesive material(s) between the cable 4 and the roller shafts of the cable release mechanism 49, and/or by setting friction of the surface of the rollers contacting the cable 4 to a desired suitable level.

[0048] The upper cable release mechanism 48 comprises two roller shafts 48s and 48t rotatably mounted one parallel to the other inside a flat frame 48f. In this specific and non-limiting example the roller shafts 48s and 48t of the upper cable release mechanism 48 have substantially the same diameter (e.g., about 16 mm). The frame 48f of the upper cable release mechanism 48 is mounted above the bottom cable release mechanism 49, between and perpendicular to the cover plates, 45f and 45r. The frame 48f is mounted inside the support structure 45 in a plane being substantially parallel to a plane in which the shaft rollers 49u and 49v, of the bottom cable release mechanism 49, reside.

[0049] As seen in FIG. 3, in this non-limiting example the axes of rotations of roller shafts 48s and 48t of the upper cable release mechanism 48 are substantially perpendicular to the axes of rotations of the shaft rollers 49u and 49v of the bottom cable release mechanism 49. The roller shafts 48s and 48t are mounted spaced-apart inside the frame 48f leaving a slender gap between them sufficient for passage of the cable (4) therethrough, while contacting the roller shafts and rotating them in predetermined directions due to friction forces evolving therebetween. The roller shafts, 48s and 48t, may be configured to prevent movement of the cable (4) towards the cable reel 47 (i.e., to prevent the cable from moving into the support structure 45), using one or more of the techniques described hereinabove with reference to the bottom cable release mechanism 49 (e.g., using a ratchet mechanism configured to prevent rotation of the shaft rollers in a counter direction).

[0050] In some embodiments a fastening element 5s (e.g., shackle), attached to the support structure 45, is used to fixedly attach the drum device 5 to the harness (6). The fastening element 5s may be attached to the support structure 45 by a fastening member 5r (e.g., metal ring or holed piece) suitable for attaching the fastening element 5s to the lower support element 45a, while permitting some rotary movement of the fastening element 5s thereabout.

[0051] FIG. 3 shows the drum device 5 without its side cover plate 45f, thereby exposing the arrangement of cable reel 47, and its reel flanges 47f, inside the support structure 45. FIG. 4 is a sectional view of the drum device, without the covering plate 45f and the reel flange 47f located beside it, thereby showing elements mounted inside the cable reel 47.

[0052] As best seen in FIGS. 5A and 5B, the axle 60 comprises a sun-gear 64 fixedly attached to it, the cover plate 45r comprises a planetary gear system 65 (e.g., comprising three planet-gear wheels) rotatably attached to it, and a ring-gear 67 is formed on a portion of the inner wall 47w of the cable reel 47 adjacent to the cover plate 45r. Each planet-gear 65, attached over the cover plate 45r free to rotate about its central axis, is mechanically coupled to the sun-gear 64 fixedly mounted on the axle 60, and to the ring-gear 67 formed on the inner wall 47w of the cable reel 47.

[0053] Optionally, and in some embodiments preferably, the planetary gear system 65 is designed to transfer the rotations of the cable reel 47 to the axle 60 during the cable release and cause counter rotations (i.e., in opposite direction) of the axle 60 in an angular velocity (V.sub.x in FIG. 6) that is greater than the angular velocity (V.sub.r) of the cable reel 47. For example, in use, as the cable 4 is released from the drum device 5, the cable reel 47 rotates about the rotation axis 47a and the ring-gear 67 formed over the inner wall 47w of the cable reel 47 rotates the planet-gears 65 mechanically coupled to it in the same direction of rotations. In effect, the planet-gears 65 coupled to the sun-gear 64 rotate the axle 60 in a direction opposite to the direction of rotation of the cable reel 47.

[0054] Optionally, and in some embodiments preferably, the planetary gear system 65 may be configured and operable to rotate the axle 60 during the cable release and cause counter rotations (i.e., in opposite direction) of the axle 60 in an angular velocity (V.sub.x in FIG. 6) whose magnitude is greater than (or equal to) the magnitude of the angular velocity (V.sub.r) of the cable reel 47. For example, and without being limiting, the planetary gear system 65 may be configured to provide a gear ratio of about 1 to 5.3.

[0055] In possible embodiments the diameter of the ring-gear 67 may be about 140 to 150 mm, the diameter of the planet-gears 65 may be about 50 to 70 mm, and the diameter of the sun-gear 64 may be about 25 to 35 mm The axle 60, rod arms 67r, gear elements and cable reel 47, and other parts of the CDD 9, may be manufactured from any suitable metallic or plastic type of material capable of withstanding the forces evolving in the device during descent. For example, and without being limiting, in possible embodiments the brake shoes 62 may be manufactured from Iron, Aluminum, Brass, Stainless Steel, or combinations thereof, the cable reel 47 may be manufactured from Aluminum, plastic, fiberglass reinforced Nylon, or combinations thereof, and the cogwheels of the gear system may be manufactured from any suitable metal or plastic material. The cable 4 may be made from a fireproof material, such as a metal, for example, from steel. Alternately, the cable 4 may be made of engineering plastics, such as Kevlar®, carbon fiber, or other high strength cable material. The length of the cable may be about 50-500 meters (m), and its diameter may be about 1 to 4 millimeters.

[0056] For example, and without being limiting, in some possible embodiments: the weight of a drum device, and about 50 m of cable reeled therein, may be about 5 kilograms; the weight of a drum device, and about 100 m of cable reeled therein, may be about 7.5 kilograms; and the weight of a drum device, and about 200 m of cable reeled therein, may be about 12 kilograms The drum device having these weight ranges may be of suitable weight for a user to lift and put on his or her back using a CDD according to embodiments of the invention.

[0057] FIG. 6 is an elevated view of the cable reel 47 without the reel flange 47f showing components of the brake mechanism 5m operably mounted thereinside. It is seen that the axle 60 passing along the rotation axis 47a of the cable reel 47 comprises one or more pass-through bores 60b, and one or more rods 67 passing through the pass-through bores 60b fixedly attached to the axle 60. Each rod 67 attached to the axle 60 radially extends from the axle 60 and forms two rod arms (67r in FIGS. 7 and 8) extending outwardly from the axle 60 in opposite directions towards the inner wall 47w of the cable reel 47. One or more brake shoes 62 slidably mounted over the rod arms 67r are mechanically coupled to the axle 60 by return springs 63 and are configured to slide outwardly over the rod arms 60r, toward the inner wall 47w of the cable reel 47, due to centrifugal forces applied on them as the axle is rotated by the planetary-gear system 65. Accordingly, in this non-limiting example the brake system implements a “normally disengaged” mechanism, as the return springs retract the brake shoes 62 radially towards the axle 60 when centrifugal forces are not being applied.

[0058] In this specific and non-limiting example, two parallel rods 67 are attached to the axle 60 to form two pairs of rod arms 67r extending in opposite directions from the axle 60 towards the inner walls 47w of the cable reel 47. A brake shoe 62 is mounted over each pair of rod arms 67r and is configured to slide radially thereover towards the inner walls 47w of the cable reel 47 against pulling forces applied on the brake shoe by two return springs 63 mounted over the rod arms 67r. Optionally, and in some embodiments preferably, the springs 63 are placed over rod arms 67r without being attached to the brake shoes 62 or to the axle 60. In this way, the springs 63 are used as partitioning elements for preventing contact between the brake shoes 62 and the axle 60, and do not apply forces on the brake shoes 62 when they radially slide towards the inner walls 47w of the cable reel 47.

[0059] FIG. 7 shows the centrifugal brake mechanism 5m in a rest state without the cable reel 47, wherein the brake shoes 62 and the return springs 63 are in a retracted position adjacent to the axle 60. When the spooled cable 4 is released from the drum device, the rotations of the cable reel 47 transferred to the planetary-gears 65 cause counter-rotations of the axle 60 and the rod arms 67r attached to it about the rotation axis 47a. The counter-rotations of the rod arms 67r apply centrifugal forces on the brake shoes 62 causing radial movement of the brake shoes 62 e.g., against return forces of the return springs 63, towards the inner wall 47w of the cable drum 47, until the brake shoes 62 contact the inner walls 47w of the cable reel 47.

[0060] As seen, the external faces (also referred to herein as front faces) 62e (i.e., facing the inner wall 47w) of the brake shoes 62 have a curved surface matching (i.e., being complementary to) the curvature of the inner walls of the cable reel 47, to thereby maximize the surface contact between them when the brake shoes 62 are pressed by the centrifugal forces against the inner walls 47w, and thereby maximize the friction forces between these surfaces. In this way, as the descent speed of the user 7 of the CDD 9 is increased during the fall, the counter-rotations of the rod arms 67r inside the cable reel 47 are also increased, thus increasing the centrifugal forces pressing the brake shoes 62 against the inner walls 47w of the cable reel 47. Consequently, the friction forces evolving between the external surfaces 62e of the brake shoes 62 and the inner walls 47w of the cable reel 47 are respectively increased, which in effect decreases the angular velocity of the cable reel 47. Correspondingly, decrease in the angular velocity of the cable reel 47 slows down the speed of cable release from the drum device, which in turn slows down the descent speed of the rescuee. Accordingly, properly setting the gear ratio of the planetary gear system 65 can be used to guarantee that the angular velocity of the cable reel 47 does not exceed a predefined limit (e.g., about 150 rpm), and thereby guarantee that the descent speed remains within a predetermined range (e.g., about 1 to 2 m/s).

[0061] In some possible embodiments the external surfaces 62e of the brake shoes 62 are covered by one or more friction enhancing layers (pads) configured to increase the friction coefficient of the brake shoes 62 and thereby increase the friction forces evolving between the brake shoes 62 and the inner walls 47w of the cable reel 47, so as to further slow down the speed of rotation of the cable reel 47 during descent. In other possible embodiments, the brake shoes 62 are configured to directly contact the inner wall 47w of the cable reel 47 i.e., without any friction enhancing layers.

[0062] Additionally, or alternatively, the brake mechanism 5m may comprise a friction enhancement (speed damping) mechanism configured to significantly increase the friction forces evolving between the brake shoes 62 and the inner wall 47w of the cable reel 47. For example, in some embodiments each brake shoe 62 comprises one or more curved (e.g., arc-shaped) grooves 68 (only one curved groove is shown in the figures) formed along its external face 62e i.e., facing the inner wall 47w of the cable reel 47, and being substantially parallel to the plane of rotation of the cable reel 47. The one or more curved grooves 68 are designed to receive and mate with one or more circular rails 66 inwardly protruding from the inner wall 47w of the cable reel 47 towards the axis of rotation 47a, and being substantially parallel to the plane of rotation of the cable reel 47. In this way, the contact surface areas of the brake shoes 62 and of the inner wall 47w of the cable reel 47 are substantially increased during engagement of the circular rails 66 in the curved grooves 68. Accordingly, as the brake shoes 62 are pushed outwardly against the inner wall 47w of the cable reel 47 by the centrifugal forces, greater friction forces evolve as the circular rails 66 progressively become engaged in the curved grooves 68, in addition to the friction forces obtained between the contacting surfaces of the front faces 62e of the brake shoes 62 and the inner wall 47w of the cable drum 47. In effect, a stronger rotation speed damping effect is achieved, which in turn effectively damps the descent speed of the CDD.

[0063] It is noted that the curved grooves 68 and their respective circular rails 66 further serve as guiding means that prevent movements of the brake shoes 62 in undesired directions during engagement of the rails 66 inside the grooves 68, and which translate rolling/tilting moments, which may be applied over the brake shoes during operation of the device, into an increase in the damping friction forces.

[0064] In some embodiments the damping friction forces are further increased by adding one or more inclined facets to the one or more curved grooves 68 and the one or more circular rails 66. For example, and without being limiting, at least one curved groove 68 may include a tapering section wherein the sides of the curved groove gradually taper towards the axis of rotation 47a, and a corresponding at least one circular rail 66 includes a corresponding tapering section configured to mate with the tapering section of the at least one curved groove 68.

[0065] In some embodiments (not shown) one or more circular rails are formed on the front faces 62e of the brake shoes 62, and one or more corresponding curved grooves are formed in the inner wall of the drum 47. Alternatively, in some possible embodiments, each brake element comprises one or more rails and one or more grooves, and the inner wall of the cable drum 47 comprises corresponding one or more grooves and one or more rails, configured to mate with therewith.

[0066] FIG. 8 shows a sectional side view of the wall of the cable reel 47 and of a brake shoe 62 according to some possible embodiments. In this non-limiting example the brake shoe 62 comprises two spaced apart and parallel pass-through bores 62r configured to receive two respective parallel rod arms 67r for slidable motion of the brake shoe 62 thereover. The return springs 63 mounted over the rod arms 67r are configured to retract the brake shoe 62 radially towards the axis of rotation 47a whenever the centrifugal forces acting on the brake shoe 62 are smaller than some predetermined level. The groove 68 may comprise a tapering portion 68s followed by a slit 68e, and the circular rail 66 protruding from the surface of the inner wall 47w may comprise a corresponding tapering structure 66s configured to be received inside the tapering portion 68s of the groove 68. The tapering portion 68s of the groove 68 and the tapering structure 66s of the circular rail 66 may have the same taper-angle a (e.g., about 30° to 90°). It is however noted that in possible embodiments the different (or slightly different) taper-angles may be used for the tapering portion 68s of the groove 68 and for the tapering structure 66s of the circular rail 66.

[0067] The slit portion 68e of the groove 68 may be configured to allow further advancement of the tapered rail 66 thereinto in response to increase in the centrifugal forces applied over the brake shoe 62. For example and without being limiting, layers of the external faces 62e of the brake shoe 62, and/or of the inner wall 47w of the cable reel 47, may be grinded during the descent, and in this event the apex of the tapered rail 66 may be further advanced into the slit portion 68e of the groove 68, thereby compensating for the grind layers by allowing expansion of the groove 68 and in effect increasing the friction between the brake shoe 62 and the inner wall 47a.

[0068] As also seen in FIG. 8, the circular rail 66 protruding from the inner wall 47w of the cable reel 47 forms two circular grooves, 7a and 7b, configured to receive respective shoulder structures, 62a and 62b, of the brake shoe 62. In this specific and non-limiting example the shoulder structures 62a and 62b are relatively symmetric and have a right-trapezoidal sectional shape.

[0069] FIG. 9 shows a perspective view of a possible arrangement of a drum device 5″ according to some possible embodiments. In this non-limiting example an additional cable release unit 80 is separately mounted above cable release opening Pc of the drum device 5″. Particularly, the additional cable release unit 80 is mounted on a support member 81 and placed spaced-apart above the top cable release unit 48 of the drum device 5″. As seen, the additional cable release unit 80 is substantially parallel to, and aligned with, the top cable release unit 48, and the orientation of its two rollers shafts, 80s and 80t, is substantially parallel to the orientation of the two rollers shafts 48s and 48t of the top cable release unit 48, to thereby guide the released cable 4 vertically/upwardly and prevent it from contacting the harness 6 and/or the rescuee 7. This arrangement of the roller shafts 48s and 48t being parallel to the back piece, also substantially prevents movement of the released cable towards the body of the rescuee.

[0070] For example, and without being limiting, the drum device arrangement shown in FIG. 9 may be used in a harness arrangement of a CDD. The drum device 5″ may be secured to a back-piece of the harness (e.g., between the shoulder blades of the user), and the support member 81 may be mounted on the back-piece above the drum device 5″ (e.g., above shoulder blades). In this configuration the additional cable release unit 80 is mounted on the separate support member 81, and it thus can move relative to drum device 5″ and thereby facilitates in absorbing shocks and in distributing fall energy.

[0071] FIG. 10A shows a possible embodiment of a drum device 5′ mounted inside a housing 96. The housing 96 is configured to accommodate the drum device with the spooled cable 4, as exemplified in any one of the figures described hereinabove or hereinbelow. The housing 96 comprises a cable release opening Pc for passage of released cable portions therethrough and several fastening holes 98f provided at boundaries of a support plate 98 attached to the drum device 5′.

[0072] FIG. 10B shows an exploded perspective view of the drum device 5′ without the housing 96 and with the cover plate 45r slightly elevated. As seen, in this non-limiting example one cable release unit 49 is used in the drum device 5′, where the roller shafts of the cable release unit 49 are attached to the cover plates 45f and 45r, beneath the cable release opening Pc and substantially perpendicular to the cover plates. In this possible embodiment the cable reel 47 is mounted within a gap g defined between two three-apex star-shaped plates 93a and 93b, which are attached to each other by support elements (e.g., rods) 45b connecting between respective apex regions thereof, and the axle 60 is attached to the star-shaped plates 93a and 93b by bearings 45x for allowing it to rotate inside the drum cable reel about its axis of rotations.

[0073] The drum device 5′ comprises a gear system (not shown) and brake elements (not shown) configured to regulate the cable release during the fall, as exemplified and described hereinabove. In this embodiment, however, each planet cogwheel is attached for rotation over a respective pivot 92 provided on one of the arms of the three-apex star-shaped plate 93b.

[0074] As described hereinabove and shown in the associated Figs., the present invention provides a centrifugal brake mechanism for a CDD. While particular embodiments of the invention have been described, it will be understood, however, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. As will be appreciated by the skilled person, the invention can be carried out in a great variety of ways, employing more than one technique from those described above, all without exceeding the scope of the invention.