Abstract
A modular rotary claw drill bit having a head is mountable at a body, the head mounting a plurality of front and gauge cutting picks. A cutting tip of each front pick is located at a different radial position at the head to optimise the flushing of cut material and to minimise pick wear during use.
Claims
1. A rotary claw drill bit comprising: a central axis; a body having a rearward region for attachment of the bit to a drill string; a bore extending axially through the body; a head provided at a forward end of the body and having an axially extending bore arranged to align with the bore of the body, wherein the bore of the head exits the head as a single opening positioned at the axis of the bit, the head including an axially rearward annular attachment face mating with an axially forward annular attachment face of the body such that the head and body are non-integrally formed along the respective attachment faces; and a plurality of picks mounted at the head, each pick having a cutting tip, the picks including radially inner front picks and radially outermost gauge picks, wherein a radial separation distance of the cutting tips of each of the front picks from the axis is different and an axial position of the tips of each of the plurality of front picks is different from an axial position of the tips of other picks of the plurality of front picks at the head, and wherein the picks are arranged into groups, and the head includes a plurality of shoulders extending radially outward and axially rearward from a forward end of the head, each shoulder mounting one of the groups of the picks such that each of the groups are mounted on a separate shoulder.
2. The bit as claimed in claim 1, wherein the front picks are positioned at the head asymmetrically.
3. The bit as claimed in claim 1, wherein the head includes a plurality of pick holders formed integrally or non-integrally with the head and the picks are detachably mounted at the head via the pick holders.
4. The bit as claimed in claim 1, wherein the picks are arranged into groups according to an angular alignment of each pick at the head relative to the central axis of the bit, wherein within a same group picks, the picks includes include an alignment that is the same or similar to one another relative to the alignment of the picks of another group.
5. The bit as claimed in claim 4, wherein the tips of the picks within at least some of the groups are positioned along an axially rearward and radially outward extending path that is curved or bent in the radial direction.
6. The bit as claimed in claim 5, wherein the path of respective groups includes a helical profile being curved or bent radially outward and extending axially rearward.
7. The bit as claimed in claim 1, wherein a size and a shape of each of the picks is the same.
8. The bit as claimed in claim 1, wherein at least the tips of each of the front and gauge picks are located at different radial and/or axial positions at the head.
9. The bit as claimed in claim 1, wherein the head includes a mounting flange provided at a rearward end and the body includes a mounting flange at a forward end arranged to mate with the flange of the head.
10. The bit as claimed in claim 9, wherein the flange of the head is a male projection and the flange of the body is a recess to receive the projection.
11. The bit as claimed in claim 1, wherein the body and the head are fixed together by a weld material.
12. A kit of parts for a rotary claw drill bit, the kit comprising: at least one body having a rearward region for attachment of the drill bit to a drill string, a bore extending axially through the at least one body; at least one head connectable to a forward end of the at least one body and having an axially extending bore arranged to align with the bore of the at least one body, wherein the bore of the head extends axially from the head as a single opening positioned at the axis of the bit, the head including an axially rearward annular attachment face mating with an axially forward annular attachment face of the body such that the head and body are non-integrally formed along the respective attachment faces; and a plurality of picks attachably mountable at the at least one head, each pick having a cutting tip, the picks including radially inner front picks and radially outermost gauge picks, a radial separation distance of the cutting tips of each of the front picks from an axis of the drill bit being different, wherein the body, the head and the picks are separate pieces attachable together, and an axial position of the tips of each of the plurality of front picks is different from an axial position of the tips of other picks of the plurality of front picks at the head, and wherein the picks are arranged into groups, and the head includes a plurality of shoulders extending radially outward and axially rearward from a forward end of the head, each shoulder mounting one of the groups of the picks such that each of the groups are mounted on a separate shoulder.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:
(2) FIG. 1 is a perspective view of a rotary claw drill bit comprising a body and a head mounting a plurality of picks arranged into cutting groups according to a specific implementation of the present invention;
(3) FIG. 2 is a side view of the bit of FIG. 1;
(4) FIG. 3 is an upper perspective view of the bit head of FIG. 2;
(5) FIG. 4 is a partial exploded perspective view of the bit of FIG. 2;
(6) FIG. 5 is a plan view of the bit of FIG. 2;
(7) FIG. 6 is a magnified side view of the bit head of FIG. 3;
(8) FIG. 7 is a longitudinal cross sectional perspective view of the bit of FIG. 2;
(9) FIG. 8 is a further perspective view of the bit head of FIG. 3 with selected cutting picks removed from the head;
(10) FIG. 9 is a perspective view of a rotary claw drill bit according to a further specific implementation of the present invention;
(11) FIG. 10 is a plan view of the cutting head of the bit of FIG. 9.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
(12) Referring to FIGS. 1 to 3, bit 100 comprises a head indicated generally by reference 101 rigidly attached to a body indicated generally by reference 102. Head 101 comprises a plurality of cutting picks 103 having cutting tips 204 that project generally axially forward at head 101 so as to represent the cutting end of bit 100. Body 102 comprises an axially rearward portion comprising threads 104 to mount bit 100 to a drill string (not shown). Head 101 comprises three radially and axially extending shoulders indicated generally by reference 200 with three picks 103 mounted at each respective shoulder 200. Each shoulder 200 comprises a mount surface indicated generally by reference 203 into which is mounted each of the cutting picks 103. Mount surface 203 along each shoulder 200 is divided into three tiered regions that form stepped sections with the mount surface 203 of each section separated by a step surface 205 that is aligned transverse and in particular perpendicular to the mount surface 203 of each section. The mount surface 203 at each shoulder section is aligned at different compound angles so as to be tilted relative to a longitudinal axis 106 of bit 100 and to lean or slope rearwardly relative to the rotational direction R of the bit 100.
(13) According to the specific implementation, picks 103 comprise a generally conical shape configuration having a respective central axis 209 that is orientated perpendicular to the mount surface 203 at each stepped section. Additionally, each of the pick axes 209 is aligned at a compound angle being transverse to bit central axis 106 and to lean into the bit rotational direction R such that the tip 204 of each bit represents the leading part. At least some of the picks are orientated to tilt towards the axis 106 (such that tip 205 is radially closer to axis 106 than a base of the pick) whilst some picks are tilted such that their tips 204 are inclined to be pointing away from the axis 106. Each shoulder 200 comprises a corresponding rearward surface 206 positioned behind mount surface 203.
(14) Referring to FIGS. 2 and 8 each pick 103 comprises a frusto-conical pick body 800 that mounts a cutting tip piece 801. Body 800 is provided at one end of an elongate pick shaft (not shown) that extends through shoulder 200 and in particular a pick bore 803 extending from shoulder mount surface 203 to shoulder rearward surface 206. Optionally, a pick washer 802 positionally supports pick body 800 at mount surface 203 with each pick shaft extending through each bore 803 and is secured in position via a retainer indicated generally be reference 207. As shown in FIG. 8, each of the three shoulders 200 comprises a series of tiered sections including a first shoulder section 804a a second shoulder section 804b and a third shoulder section 804c. Each section 804a, 804b, 804c is positioned to extend radially outward from axis 106 and to extend generally axially rearward in the general direction of bit head 101 towards bit body 102.
(15) Referring to FIGS. 2 and 4, head 101 comprises an axially rearward annular attachment face 201 configured to mate in touching contact with an axially forward annular attachment face 202 of bit body 102. An annular attachment neck or flange 402 projects axially rearward from head attachment face 201. A corresponding annular collar 400 projects axially forward from body attachment face 202 and is configured to receive neck 402 within a cavity region 401 defined by collar 400. Via the appropriate mating of neck 402 within collar 400, bit head 101 may be appropriately aligned and mounted onto body 102. A weld material is applied between and at the junction of the attachment faces 201, 202 so as to secure head 101 to body 102. A bore 306 extends centrally through head 101 and is aligned radially with a corresponding bore 403 extending within body 102 such that the two bores 306, 403 define a single bore that extends axially from a rearwardmost annular edge 704 at body 102 to a single bore opening 307 at head 101 referring to FIGS. 3 and 7.
(16) As illustrated in FIGS. 3 and 5, the three shoulders 200 project radially outward around bore opening 307 to form three radially extending wings mounting each of the picks 103 at their respective tiered sections. In particular, a first shoulder 303 provides a mount for a first group of picks 300a, 300b, 300c; a second shoulder 304 provides a mount for a second group of picks 301a, 301b, 301c; and a third shoulder 305 provides a mount for a third group of picks 302a, 302b, 302c. As illustrated with reference to FIG. 8, each of the three shoulders 303, 304, 305 comprises a corresponding mount surface 203 that is divided into stepped sections 804a, 804b, 804c such that each pick of each of the groups is positioned at a respective step S04a, 804b, 804c at each of the respective shoulders 303, 304, 305. The mount surface 203 of each shoulder 303, 304, 305 is positioned to sit on a generally helical path that extends radially outward and axially rearward around axis 106 from the region of bore opening 307 that is centred on axis 106. As illustrated in FIG. 3, within each group of picks, each pick comprises an angular alignment that is generally similar and that is different to the angular alignment of the picks of the remaining groups. As the picks within all groups are positioned on a path having a generally helical profile that extends around axis 106, the alignment of each pick 300a, 300b, 300c within each group is not identical but is generally similar so as to define a collective set of picks that are configured to cut the rock in a coordinated manner and to create concentric grooves in the rock that act to stabilise axially forward drilling and bit steering. In particular, the axis 300d of the first group of picks 300a, 300b, 300c is transverse to the axis 301d of the second group of picks 301a, 301b, 301c that is in turn aligned transverse to the axis 302d of the third group of picks 302a, 302b, 302c.
(17) Referring to FIGS. 5 and 6, an apex cutting tip 600a, 600b, 600c (illustrated with reference to the first group of picks 300a, 300b, 300c) are aligned on helical path 500 that projects radially outward and axially rearward relative to axis 106. The cutting tips of the picks of the second and third groups 301, 302 are similarly aligned on respective helical paths 501, 502 that extend radially outward and axially rearward at head 101. The axial and radial position and alignment of each respective mount section 804a, 804b, 804c at each shoulder 303, 304, 305 is different so as to provide a different axial and radial position and alignment of each of the respective picks 103 of each of the groups of picks such that a radial and axial position of each cutting tip (for example 600a to 600c and 601a to 601c) is different for all picks 103 at head 101.
(18) Referring to FIGS. 3 and 5, one pick 300a, 301a, 302a is positioned radially innermost; a corresponding second pick of each group 300c, 301c, 302c is positioned radially outmost relative to axis 106 and a third pick of each respective group 300b, 301b and 302b is positioned radially intermediate the respective first and second picks to create three cutting wings that are bent in the radially outward direction from axis 106. Accordingly, the first and third picks 300a, 301a, 302a, 300b, 301b and 302b may be termed front picks and the second picks 300c, 301c, 302c may be termed gauge picks. Each of the radially innermost front picks 300a, 301a, 302a are positioned radially inside and axially forward of all the intermediate front picks 300b, 301b, 302b. Additionally, the intermediate front picks 300b, 301b, 302b are positioned radially inside and axially forward of all of the gauge picks 300c, 301c, 302c. The cutting tips 204 of the gauge picks 300c, 301c, 302c represent a radially outermost part of bit 100 and determine the diameter of the borehole during drilling.
(19) According to the specific implementation, a radial separation distance of the tip 204 of each of the radially innermost set of front picks 300a, 301a, 302a is different and a corresponding radial separation distance from axis 106 of the intermediate front picks 300b, 301b, 302b is also different within these two sets of front picks. Also, as can be seen from FIG. 6, the axial position of each tip 204 of the front picks 300a, 300b, 301a, 301b, 302a, 302b relative to, for example, the axially rearward attachment surface 201 is different. This individual radial and axial positioning of each tip 204 of the inner front picks is advantageous to contact different radial and axial positions of the rock face to optimise rock fracture during rotation of bit 100. Such a configuration also facilitates uniform wear across the different picks to maximise the period between which the picks are required to be interchanged when worn.
(20) According to the specific implementation, the radial separation distance of the tip 204 of each of the gauge picks 300c, 301c, 302c and the axial position relative to the rearward attachment surface 201 is approximately equal. Such a configuration is advantageous to stabilise forward drilling and facilitate steering/guidance of the bit in use. However, according to further specific implementations, the radial and axial position of the respective tips 204 of the gauge picks 300c, 301c, 302c may be different within this set of picks so as to enhance the rock breaking characteristics of the bit and hence the drilling rate.
(21) FIGS. 9 and 10 illustrate a further embodiment of the present invention in which pick head 700 comprises three corresponding shoulders 701, 702, 703. Three picks 103 are provided at the first and second shoulders 701, 702 whilst two picks 103 are provided at third shoulder 703. As with the embodiment of FIGS. 1 to 8 each of the shoulders 701, 702, 703 extend generally along a radially outward and axially rearward extending path relative to axis 106 and comprise the corresponding tiered sections and mount surfaces 804a, 804b, 804c.
