BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The foregoing summary, as well as the detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, which are diagrammatic, embodiments that are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
FIG. 1 is an axial cross-sectional view of a down-hole drill including a bit assembly in accordance with the present invention;
FIG. 2 is an enlarged, partly broken-away view of a lower end of the drill of FIG. 1;
FIG. 3 is another view of the drill lower end of FIG. 2, shown with a casing being displaced from a bit at the beginning of drill extraction operation;
FIG. 4 is partly broken-away, perspective view of a lower portion of the drill and bit assembly, shown with a chuck of the bit assembly in axial cross-section and a bit and retainer of the bit assembly in perspective;
FIG. 5 is an enlarged, partly away, broken-away perspective view of the drill lower end, shown with the chuck and bit in axial cross-section and the retainer in perspective;
FIG. 6 is a perspective view of the bit assembly;
FIG. 7 is another perspective view of the bit assembly, shown with the bit separate from the chuck and retainer;
FIG. 8 is a top plan view of the retainer;
FIG. 9 is an axial cross-sectional view of the retainer through line 9-9 of FIG. 8;
FIG. 10 is an axial cross-section of the chuck;
FIG. 11 is a bottom plan view of the chuck;
FIG. 12 is an axial cross-sectional view of the bit;
FIG. 13 is a top plan view of the bit;
FIG. 14 is an axial cross-sectional view of the bit assembly, shown aligning the bit for connection with the chuck;
FIG. 15 is an axial cross-sectional view of the bit being connected with the chuck, showing an upward force applied to the bit to cause the bit lug shoulders forcing the retainer to an inner radial position;
FIG. 16 is an axial cross-sectional view of the bit assembly, showing the bit lugs shoulders displacing axially upwardly against the retainer;
FIG. 17 is an enlarged view of the retainer and bit lug shoulders of FIG. 16;
FIG. 18 is an axial cross-sectional view of the bit assembly, showing the bit lugs engaged with the retainer to releasably couple the bit with the chuck;
FIG. 19 is a radial cross-section view of the bit assembly though line 19-19 of FIG. 18;
FIG. 20 is an enlarged view of the retainer and bit lug shoulders of FIG. 18;
FIGS. 21A-21C, collectively FIG. 21, are each an axial cross-sectional view of the bit assembly, showing the coupled bit at respectively a lower limit axial position, an intermediate axial position, an upper limit axial position; and
FIG. 22 is an axial cross-sectional view of the lower end of the drill, showing a pusher tool displacing a hammer of the drill to enable removal of the bit.
DETAILED DESCRIPTION OF THE INVENTION
Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, left”, “lower”, “upper”, “upward”, “down” and “downward” designate directions in the drawings to which reference is made. The words “inner”, “inwardly” and “outer”, “outwardly” refer to directions toward and away from, respectively, a designated centerline or a geometric center of an element being described, the particular meaning being readily apparent from the context of the description. Further, as used herein, the word “connected” is intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import. Furthermore, the term “position” is used herein to indicate a position, location, configuration, orientation, etc., of one or more components of the bit assembly and each is depicted in the drawings with reference to a randomly selected point on the item being described. Such points in the drawing figures are randomly selected for convenience only and have no particular relevance to the present invention.
Referring now to the drawings in detail, wherein like numbers are used to indicate like elements throughout, there is shown in FIGS. 1-22 a bit assembly 10 for a down-hole, percussive drill 1 including a casing 2 and a hammer 3. The casing 2 has opposing ends 2a, 2b, an interior chamber 2c, and an axis 2d extending centrally between the ends 2a, 2b. The hammer 3 is movably disposed at least partially within the casing chamber 2c so as to reciprocally displace linearly along the axis 2d, and has a working or “strike” end 3a. The bit assembly 10 basically comprises a chuck 12 connected (or connectable) with the casing 2, a bit 14 having a cutting surface 15 and a cavity CB configured to receive the hammer end 3a, and a retainer 16 disposable within the bit cavity CB and configured to movably and releasably couple the bit 14 with the chuck 12. Preferably, the bit assembly 10 also includes a skirt 13 connected with the casing 2 and configured to enclose at least portions of the chuck 12 and the bit 14, as described below.
The chuck 12 is configured to movably connect the bit 14 with the casing 2; that is, the retainer 16 is connected with the chuck 12 and is engageable with the bit 14 to movably couple or retain the bit 14 with/to the chuck 12, and thus also with the casing 2. Preferably, the chuck 12 has a cavity CC and the retainer 16 is simultaneously disposable within the chuck cavity CC and the bit cavity CB, the two cavities CC, CB being at least partially overlapping or coincident when the two components 12, 14 are movably coupled. Further, the bit 14 also has an interior contact or “impact” surface 17 bounding an inner axial end of the bit cavity CB and is axially displaceable with respect to the chuck 12 and the casing 2. Specifically, the bit 14 is movable between a first, upper limit position A1 (FIGS. 2, 5, 21C) and a second, lower limit position A2 (FIG. 3, 18, 21A), whether such movement is due to displacement of the bit 14 or of the chuck 12 (i.e., and casing 2). The hammer strike end 3a is slidably disposable within the retainer 16 and within both the chuck and bit cavities CC, CB so as to impact or strikingly engage the bit impact surface 17, displacing the bit 14 toward the lower limit position A2 and/or driving the cutting surface 15 into a work surface SW (FIG. 2) as discussed in further detail below.
Preferably, the chuck 12 includes at least one and preferably a plurality of clearance openings 20 and the bit 14 includes at least one and preferably a plurality of axial lugs 22 each disposable within a separate one of the chuck clearance openings 20. As the bit 14 moves relative to the chuck 12, the bit lugs 22 linearly displace (i.e., axially) through the chuck openings 20. As such, the chuck 12 and bit 14 are essentially “telescoping” but without radial overlapping of the two components 12, 14, i.e., the engaged portions of the chuck 12 and bit 14 have at least generally the same outside diameter ODC, ODB, as discussed below. Further, when the retainer 16 is disposed within coincident sections of the bit cavity CB and the chuck cavity CC, the retainer 16 is simultaneously connected with the chuck 12 and engageable with or by one or more bit lugs 22 to releasably (and movably) connect the bit 14 and the chuck 12, as discussed in greater detail below.
Further, the retainer 16 preferably includes a generally radial catch surface 19 facing generally axially upwardly toward the casing 2, which is contactable by a generally axially downwardly facing stop surface 23 of each bit lug 22 when the bit 14 is located at the lower limit position A2. As such, contact between the retainer catch surface 23 and bit stop surface 23 prevent axial displacement of the bit 14 beyond the bit lower limit position A2 (FIGS. 3, 18, 21) (i.e., in a first, downward axial direction d1), thus preventing inadvertent removal of the bit 14 from the chuck 12. Further, the lugs 22 also contact the chuck 12 at the upper limit position A1, so as to thereby prevent further displacement in a second direction d2 toward the casing 2. As such, the upper end of each bit lug 22 is thereby movably retained between the retainer 16 and the upper, closed ends of the chuck clearance openings 20, as discussed in greater detail below.
Referring now to FIGS. 3, 8, 9, and 16-19, the retainer 16 preferably includes a generally annular body 24 having a central bore opening or bore 26 configured to receive the hammer end 3a, such that the hammer 3 is slidably displaceable through the retainer body 24. When the hammer end 3a is disposed within the retainer bore 26, the hammer 3 prevents disengagement of the retainer 16 from the bit 14. Specifically, the retainer 16 is preferably configured to be at least partially radially displaceable between an outer radial position RO (see, e.g., FIGS. 20 and 21) and an inner radial position RI (FIGS. 16 and 17) and most preferably collapsible or radially deflectable between the two positions RO, RI, as discussed below. At the outer position RO, at least a portion of the retainer 16 is releasably engaged with the bit 14 so as to thereby connect the bit 14 with the casing 2 (see, e.g., FIG. 20). As best shown in FIG. 17, at the inner radial position RI, the retainer 16 is generally disengaged from, or nonengageable with, the bit 14 such that the bit 14 is disconnectable from the casing 2. More specifically, the retainer body 24 has an outer diameter that varies between maximum value ODmax (FIG. 20) at the outer position RO, at which the retainer 16 is engageable with/by the bit 14 (i.e., contactable by the stop surface 23) and a minimum value ODmin (FIG. 17), at which the bit 14 is axially displaceable about the retainer 16, as described in greater detail below.
Referring to FIGS. 2, 3, 17 and 20, with such a retainer structure, the hammer 3 prevents displacement of the retainer 16 to the inner position RO when the hammer end 3a is disposed within the retainer bore 26, thereby retaining the bit 14 connected with the chuck 12, as discussed in further detail below. More specifically, the retainer bore 26 has an inner diameter that varies between maximum and minimum values IDmax (FIG. 20) and IDmin (FIG. 17), respectively, as the retainer body 24 radially displaces or deflects between the inner and outer positions RO, RI. The hammer 3 has an outer diameter ODP (FIG. 3) with a constant value that is greater than the retainer inner diameter minimum value IDmin (but at least slightly lesser than the maximum value IDmax), such that retainer 16 cannot displace to the inner position RI when the hammer 3 is disposed within the bore 26, as best shown in FIG. 3.
Referring particularly to FIGS. 8 and 9, the retainer body 24 is preferably formed as a generally circular ring 25 with ends 25a, 25b spaced by an axial gap 27, generally similar to a “snap ring”. As such, the retainer 16 generally radially displaces or deflects between the inner and outer positions RI, RO by moving the ends 25a, 25b to generally open and close the gap 27. That is, as the ring gap 27 is closed, the retainer ring 25 collapses or deflects inwardly toward the body inner position RI, and vice-versa. Further, the ring 25 preferably has generally “frustatriangular” axial cross-sections CSR (FIG. 9), such that the body 24 has first and second angled, outer circumferential surfaces sections 29A, 29B, and a central outer circumferential surface 29C extending axially between the two angled surfaces 29A, 29B. The first angled surface 29A provides at least a portion of the retainer catch surface 19, as discussed above, and each angled surface 29A, 29B also functions as a driven surface engageable by the bit lugs 22 to displace the retainer between the outer and inner positions RO, RI, as described below.
Although a one-piece annular ring 25 is presently preferred, the retainer body 24 may alternatively be formed in any other appropriate manner that enables the retainer 16 to function generally as described herein. For example, the retainer body 24 may include two or more arcuate segments (not shown) defining a bore for receiving the hammer 3, being separately (but generally simultaneously) displaceable radially between inner and outer positions, and configured to retain the bit 14 coupled with the chuck 12 when located at the outer positions. The scope of the present invention encompasses these structures described or suggested herein, and all other appropriate structures that enable the bit assembly 10 to function generally as described herein.
Referring to FIGS. 6, 7, 10, 11, and 14-20, the chuck 12 preferably includes a generally tubular body 28 with first and second ends 28a, 28b and a central axis 30 extending between the two ends 28A, 28b. The body first end 28a is connectable with the casing 2, and preferably has exterior threads 32 engageable with corresponding interior threads (not indicated) of the casing 2, thus releasably connecting the chuck 12 therewith. When the chuck body 28 is connected with the casing 2, the chuck axis 30 extends generally collinearly with the casing axis 2d and the body second end 28b is spaced axially from the casing lower end 2b. The chuck body 28 has a central bore 31 providing the chuck cavity CC and being sized to receive the hammer 3 such that the hammer 3 is slidably displaceable therethrough. Preferably, the chuck bore 31 includes a guide surface section 33 having a inner diameter IDGS (FIG. 10) that is slightly greater than the hammer outside diameter ODH, which acts to center the hammer 3 on the casing axis 2d as the hammer reciprocates during a drilling operation. The guide surface 31 also functions to assist in the timing of the exhaust flow through the hammer 3, as hammer exhaust ports 3b (see FIG. 4) are sealed when disposed within the cylinder guide surface 31. Thus, the chuck surface 31 alternatively opens and closes the exhaust ports 3b depending on the position of the hammer 3 with respect to the chuck 12.
Further, the chuck body 28 has at least one and preferably a plurality of circumferentially spaced, elongated slotted through holes 34 extending generally axially and inwardly from the body second end 28b toward the body first end 28a, each slotted hole 34 providing one chuck clearance opening 20, as described above. Most preferably, the chuck slotted through holes 34 are sized and spaced so as to define a plurality of chuck lugs 36, i.e., between adjacent pairs of holes 34, which are disposable within corresponding bit openings 48, as discussed below. Specifically, each chuck lug 36 extends axially from a generally enclosed sidewall portion 38 of the tubular body 28 (i.e., the remainder of the body 28 not “cut through” by the holes 34) to the body second end 28b. Further, each clearance hole 34 has a radial open end 34a and is partially bounded by a generally arcuate, axial surface providing one of the above-described stop surfaces 35. Specifically, each stop surface 35 is engageable/contactable with one of the chuck lugs 22 to generally prevent axial movement of the bit 14 in the second direction d2 beyond the bit upper position A1, as described above and in additional detail below.
Preferably, each chuck lug 36 includes a generally rectangular, cantilever-like body 37 having a first end 37a connected, and preferably integrally formed with, the chuck enclosed sidewall portion 38, and a second, free end 37b spaced axially from the first end 37a. Each lug body 37 has inner and outer, generally circumferential surfaces 37c, 37d, the outer surfaces 37d of all the chuck lugs 36 collectively defining the chuck outside diameter ODC, as discussed above and in further detail below. Also, each lug body 37 further has opposing radial contact surfaces 41 extending axially between the body first and second ends 37a, 37b and slidable against corresponding surfaces of the bit lugs 20, as described in below. Preferably, each lug body 37 further includes an inner circumferential groove 39 extending radially outwardly from the lug inner surface 37d, each groove 39 being configured to receive a portion of the retainer annular body 24.
Specifically, each lug groove 39 has generally triangular axial cross-sections, a width wg (FIG. 10) that is generally equal to the axial thickness ta (FIG. 9) of the retainer annular body 24, and a depth dg such that the plurality of grooves 39 collectively define an inside diameter (not indicated) that is at least slightly lesser than the maximum outside diameter ODMAX of the retainer annular body 26. As such, the retainer body 24 is simultaneously disposable within all of the chuck lug grooves 39 so that the retainer 16 is frictionally connected with the chuck 12. That is, the preferred ring body 25 is inwardly collapsed or deflected so as to fit inside the chuck cavity CB and is then positioned axially adjacent to the chuck grooves 39. Thereafter, the ring 25 is allowed to deflect outwardly until separate portions of the ring 25 become disposed within each groove 39, so as to be retained therein by friction, which is preferably increased by sizing the grooves 39 such that the installed body diameter (i.e., ODMAX) is less than the “free” or un-deflected diameter ODF (FIG. 8).
Although the chuck body 28 is preferably constructed as described above, the chuck 12 may be formed in any other appropriate manner. For example, the chuck body 28 may be provided with two or three narrower clearance holes or slots 20 separated by arcuate wall sections of substantially greater circumferential length, the bit 12 being appropriately formed with two or three lugs separated by substantial circumferential clearance. The scope of the present invention encompasses these and all other appropriate structures of the chuck 12 that enable the bit assembly 10 to function at least generally as described herein.
Referring to FIGS. 6, 7 and 12-20, the bit 14 preferably includes a “stepped” body 40 with first and second ends 40a, 40b and a central axis 42 extending between the two ends 40a, 40b. The body first or upper end 40a is movably coupleable with the chuck 12, specifically by the interaction of the bit lugs 22 with the retainer 16, such that the bit axis 42 is generally collinear with both the chuck and drill/casing axis 2c. The body second or lower end 42b includes the cutting or working surface 15. Preferably, the body 40 preferably includes a lower, generally cylindrical portion 42 and an upper, generally tubular portion 44 spaced axially from the cylindrical portion 42. The body cylindrical portion 42 has an outer axial end 42a providing the cutting surface 15 and an inner axial end 42b providing the impact surface 17. More specifically, the cylindrical portion outer axial end 42a has a plurality of generally circular pockets 46 each containing a hardened cutting insert 48. The body portion inner axial end 42b has a generally circular surface 50 providing the impact surface 17 and is strikeable by the hammer end 3a, as discussed above and in further detail below. Further, the bit cylindrical portion 42 also preferably has at least one or more exhaust holes or ports 52 (two depicted), five holes/ports 52 being presently preferred (structure not shown), each extending between the first and second axial ends 42a, 42b. The exhaust holes 52 provide passages for discharging percussive fluid from the drill casing 2 and are also preferably sized to receive a pusher tool T for displacing the hammer end 3a from the bit cavity CB, as shown in FIG. 22 and discussed in greater detail below.
Furthermore, the bit tubular portion 44 has an inner axial end 44b connected, preferably integrally formed with, the cylindrical portion inner axial end 42b, and an opposing outer axial end 44a, which is engaged/engageable with the chuck body 28. The bit tubular portion 44 provides the bit cavity CB and the least one bit lug 22, preferably four or more lugs 22 spaced circumferentially about the body axis 42 so as to form a “slotted tube” structure. Specifically, each bit lug 22 includes a generally rectangular, cantilever-like body 52 having a first end 52a connected, and preferably integrally formed with, an enclosed sidewall portion 54, and a second, free end 52b spaced axially from the first end 52a. Each lug body 52 has inner and outer, generally circumferential surfaces 52c, 52d, the outer surfaces 52d of all the bit lugs 36 being located at the bit outside diameter ODB, as discussed above and in further detail below. Further, each lug free end 52b has a radial end surface 53 contactable with the chuck stop surface 35 bounding the clearance hole 34 in which the lug 20 is disposed, so as to thereby prevent axial displacement beyond the bit upper position A2 (as described above), preferably in conjunction with the interaction between chuck radial end surfaces 43 and bit slot end surfaces 57. Furthermore, each bit lug body 52 preferably further has two opposing radial contact surfaces 55 each extending axially between the body first and second ends 52a, 52b. Each bit lug contact surface 55 is axially slidable against a chuck lug contact surface 41 as the bit 14 moves relative to the chuck 14, such that the chuck lugs 36 guide the displacement of the bit 14 and torque generated by the hammer 3 on the bit 14 is transferred to the chuck 12 at the interface of each contact surface pair 41/55 (see, e.g., FIG. 6). As the bit assembly 10 has eight contact surface pairs 41/55 which potentially extend along the entire length of the mating lugs 22, 36, the contact pressure between the bit 14 and the chuck 12 is substantially reduced in comparison with previously known bit designs, even though generally only half the surface pairs 41/55 are used depending on the angular direction of applied torque.
Still referring to FIGS. 6, 7 and 12-20, the bit 14 also includes a plurality of elongated, slotted clearance holes 56 each cut or defined between adjacent pair of lug bodies 52. Each bit clearance hole 56 has a radial open end 56a and sized to receive a separate one of the chuck lugs 36, as discussed below. Preferably, the lug bodies 52 and clearance holes 56 extend only partially axially through the body tubular portion 44, such that the tubular portion 44 also includes an enclosed circumferential sidewall section 54, as mentioned above. The enclosed sidewall section 54 is disposed axially between the body cylindrical portion 42 and the plurality of lugs 20, and has an inner circumferential surface 54a. The wall inner surface 54a surrounds the hammer end 3a with clearance when the hammer 3 strikes the bit impact surface 17, so as to generally constrain or “nest” the hammer end 3a to prevent lateral movement thereof and to overlap the clearance holes 56 to prevent the opening thereof when the bit 14 drops. However, the sidewall section 54 is not required for proper operation of the bit assembly 10 of the present invention.
Referring particularly to FIGS. 11 and 12, each bit lug 22 preferably includes an arcuate shoulder 58 disposed generally proximal to the lug body free end 52b and engageable or contactable with the retainer 16 to retain the bit 14 movably coupled with the chuck 12. Specifically, each lug shoulder 58 extends generally circumferentially and axially-inwardly from the bar inner surface 52c, and includes upper and lower angled or tapered surfaces 60A, 60B and an inner circumferential slide surface 61 extending axially between the tapered surfaces 60A, 60B. The lower tapered surface 60B provides the stop surface 23 of each bit lug 20, and is contactable with the retainer catch surface 17 to prevent further downward axial displacement of the bit 14. Further, the shoulder slide surface 61 is slidable against the retainer central outer surface 29C when the retainer 16 is disposed at the inner radial position RI, the shoulder slide surfaces 61 collectively defining a lug shoulder inner diameter IDLS within which the retainer 16 must be deflected to enable installation and removal of the bit 14.
Further, the lug shoulder tapered surfaces 60A, 60B are also each configured to slide against the lower and upper retainer angled surfaces 29B, 29A, respectively, so as to force the retainer body 24 to deflect radially inwardly. Specifically, when the hammer 3 is spaced from the retainer 16, the lug upper surfaces 60A are each disposed against the lower retainer surface 29B, and an upward force FU of a sufficient magnitude is applied to the bit 14, the lug tapered surfaces 60A all push against the retainer angled surface 39B to force the retainer body 24 to move or deflect toward the inner position RI, enabling the shoulder slide surfaces 61 to slide along and past the retainer central outer circumferential surface 29C, as shown in FIGS. 15-17. Similarly, when the hammer 3 is located externally of the retainer 16, the lug lower surface 60B is disposed against the upper retainer surface 29A, and a sufficiently large downward force FD is applied to the bit 14, the lug tapered surface 60B wedges against the retainer angled surface 29A so as to push the retainer body 14 generally inwardly toward the inner position RI to permit further downward axial movement of the bit 14.
Although the bit 14 preferably has a body 40 as constructed as described above, the bit 14 may alternatively be formed in any other appropriate manner. For example, the bit 14 may include only two or three “narrow” lugs 22 that engage with appropriately sized chuck clearance slots 20 and separated from each other by a substantial clearance space, as discussed above with the bit 14. Further for example, the bit lugs 22 may be integrally formed directly with the body cylindrical portion 42, such that body tubular portion 44 includes only the lugs 22 (i.e., without the enclosed sidewall portion 54). Also, the bit lug bodies 52 (and clearance openings 56) may extend both axially and radially between the first and second ends 52a, 52b so as to be generally spiral-shaped, and interact with corresponding shaped bit clearance openings 20 and lugs 36. With such a structure, the bit 14 will turn or angularly displace as the bit moves axially between the upper and lower limit positions, which may be advantageous during a drilling operation. The scope of the present invention encompasses these and all other alternative structures of the bit 14 that enable the bit assembly 10 to function generally as described herein.
Referring to FIGS. 1-5, the skirt 13 preferably includes a generally tubular body 70 having upper end lower radial ends 70a, 70b and a central bore 73 sized to receive the chuck 12 and the bit 14. The skirt body upper end 70a is connectable with the casing 2, preferably by sandwiching an inner circumferential shoulder 71 of the skirt between the chuck body upper end 28a and the casing second end 2b, and the second end 70b is spaced axially from the casing second end 2b. The skirt body 70 has an axial length (not indicated) sufficient to enclose all of chuck clearance openings 20 and the bit clearance holes 56, as best shown in FIG. 7. As such, the skirt 13 both prevents the premature exhaust (or reintroduction) of percussive fluid within the drill 1 and prevents debris (e.g., rock cuttings, etc.) from entering into the bit assembly 10.
Referring now to FIGS. 14-22, with the above-described bit assembly 10, the bit 14 is movably coupled with the chuck 12, and alternately decoupled or removed from the chuck 12, in generally the following manner. To couple or install the bit 14 when separate from the chuck 12, and thus from the drill 1, the hammer lower end 3a must be displaced axially upwardly so as to be located externally of, or spaced from, the retainer 16, preferably by means of a pusher tool T as shown in FIG. 22. Then, the bit 14 and chuck 12 are coaxially and angularly aligned such that each bit lug free end 52b is located adjacent to a separate chuck clearance hole open end 34a and each chuck lug free end 37b is located adjacent to a separate bit clearance hole open end 56a, as shown in FIG. 14. Thereafter, the bit 14 is axially displaced toward the chuck upper end 28a (or the chuck 12 toward the bit lower end 40b) such that the bit lugs 22 become increasingly disposed within the chuck openings 20 and the chuck lugs 36 move deeper into the bit holes 56, until the shoulder upper surfaces 60A of the bit lugs 22 become disposed against the lower tapered surface 29B of the retainer 16, as depicted in FIG. 15. At this point, an upward force FU of a sufficient magnitude is applied to the bit 14 until the retainer 16 is forced to displace inwardly, as described above, until the bit shoulders 58 displace axially upwardly past the retainer 16, as shown in FIGS. 16 and 17. Then, the retainer body 26 is free to deflect radially toward the retainer outer position RO, such that the bit lugs 22 are then constrained to displace axially within the chuck slotted openings 20, thereby movably coupling or retaining the bit 14 with the chuck 12 by contact between the retainer catch surface 19 and the bit lug stop surfaces 23, as shown in FIGS. 18-21.
Referring to FIGS. 2 and 3, in use, the hammer 3 is accelerated by appropriately directed or channeled percussive fluid (e.g., compressed air) to move downwardly toward the bit 14, such that the hammer end 3a slidably displaces through the chuck 12, enters and moves axially within the bit cavity CB until striking the bit impact surface 17. Such a hammer impact pushes the bit 14 to displace generally axially downwardly relative to the chuck 12, such that the bit lugs 22 move partially outwardly from the chuck clearance openings 20, forcing the bit cutting surface 15 into the work surface SW to fracture material therefrom. The hammer 3 is then displaced axially upwardly by appropriate channeling of the percussive fluid, and is thereafter repeatedly reciprocated into striking contact with the bit 14 for the duration of a drilling operation.
When it is desired to remove the bit 14 from the chuck 12, and thus the drill 1, the hammer lower end 3a is displaced axially out of the retainer 16 by the pusher tool T, and then bit 14 is axially displaced downwardly toward the chuck lower end 28b (or the chuck 12 toward the bit upper end 40a) such that the bit lugs 22 become increasingly withdrawn from the chuck openings 20 and the chuck lugs 36 move outwardly from the bit holes 56. When the shoulder lower surfaces 60B of the bit lugs 22 become disposed against the upper tapered surface 29A of the retainer 16, a downward force FD (FIG. 16) of a sufficient magnitude is applied to the bit 14 to force the retainer 16 to displace radially inwardly, as described above, until the bit shoulders 58 move axially downwardly past the retainer 16. At this point, the bit 14 is decoupled from the chuck 12, permitting the bit lugs 22 to displace completely out of the chuck holes 22, simultaneously withdrawing the chuck lugs 36 out of the bit clearance holes 56, until the bit 14 is separate from the chuck 12.
The bit assembly 12 of the present invention is clearly advantageous in comparison with previously known bit assemblies. First, the bit 14 is installed by relatively simple procedure of pushing the hammer 3 out of the assembly, and then applying an axial force sufficient to cause the bit lugs 22 to collapse the preferred snap ring retainer 16. Such a procedure is much simpler than rotating an entire bit assembly, including the chuck, to threadably disengage the chuck from the casing. In fact, the present bit assembly 10 enables removal of the bit 14 without disassembly of the chuck 12. Also, by having a retainer 16 that moves or deflects inwardly to release the bit 14, as opposed to outwardly with the prior art split rings, and which has an inner surface disposable against the hammer 3, the chance of an axial load causing an inadvertent release of the bit 14 is substantially reduced. Further, by having the chuck 12 and bit 14 engaged by intermeshing axial lugs 22, 36 and axial clearance openings 20, 56, as well as a hammer impact surface 17 spaced relatively axially close to the cutting surface 15, the bit assembly 10 is much less massive, and requires less material, than prior art bit assemblies. Specifically, previously known bit assemblies had a bit with an outer circumferential surface that engaged with a chuck inner circumferential surface, and had a hammer impact surface at an inner end of the bit body, which thus requires a bit of substantially greater axial length in comparison with the bit 14 of the present invention.
Also, the bit cavity CB provides a “gallery” for exhausting percussive fluid such that the fluid is distributed to the bit cutting surface 15 in a particular, desired manner. For example, the bit 14 may include a relatively small central hole fluidly coupled with the cavity CB from which two or three (or more) exhaust ports extend to the cutting surface 15 (structure not shown). The bit assembly 10 of the present invention may include any number of exhaust ports 52 that evenly disperse fluid across the bit surface 15 so as to provide improved chip removal and minimize wear or erosion. Finally, by having a bit 14 that engages the chuck 12 up to the outer diameter ODC, ODB of the bodies 28, 40 of both the chuck 12 and bit 14, torque generated in the bit 14 by hammer impact is transmitted to the chuck 12 at a relatively greater diameter in comparison with previously known bit designs. As such, contact pressures for a given torque are minimized in the present bit assembly 10, so as to reduce the likelihood of developing fatigue crack initiation sites from frictional burning.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims.
Patent Application
20080078584
