Patent Application
20100263932
The present invention relates to down-hole drills and, more particularly, a bit retainer assembly for such a drill.
Down-hole drills, also known as down-hole hammers, down-the-hole (DTH) drills, and earth-boring drills, are typically fluid-operated and generally include a casing, a piston movably disposed within the casing, and a cutting bit with a cutting surface movably coupled with the casing. The piston is linearly reciprocated within the casing to repeatedly impact the bit so as the drive the cutting surface into a work surface of a hole being drilled. Typically, such drills further include a chuck threaded to the casing and for guiding the movement of the bit and/or the piston. The bit may be movably disposed within a central bore of the chuck, and the bit and chuck have complementary grooves and splines that slidably interact during movement of the bit. Further, the bit is generally secured to the chuck by means of a set of split rings that engage with the outer surface of the bit, such as with a bit groove or shoulder, so as to connect the bit with the chuck.
When a bit breaks during drilling operations, an operator must remove the broken pieces of the bit before drilling can continue. This process can be time consuming and expensive and, if unsuccessful, can result in abandonment of the hole being drilled.
It is important to provide structure to retain the broken portion of the bit with the rest of the drilling assembly so that the broken portion can be retrieved from the hole without undue delay and expense. The structure should also be reliable.
In one embodiment, the invention may provide a retainer device for a drill bit for an earth-boring drill assembly, the drill assembly including a casing having a central axis, the bit having a generally cylindrical head. The retainer device generally includes an annular sleeve connectable to the casing and a retainer assembly provided between the sleeve and the bit. The retainer assembly may include an axial slot defined by one of the sleeve and the bit, the slot having an axially-extending side wall defining an opening and an axial end wall, and a lug supported on the other of the sleeve and the bit, the lug being positionable in the slot through the opening in the side wall, the lug being engageable with the end wall to restrict axial movement of the bit from the sleeve and away from the casing.
In some constructions, the head of the bit has an outer circumferential surface, the slot is defined on the outer circumferential surface of the head of the bit, and the lug is supported by the sleeve. The lug may be integrally formed with the other of the sleeve and the bit.
In some constructions, the retainer assembly may include a first axial slot defined by one of the sleeve and the bit, the first slot having an axially-extending first side wall defining an opening, an opposite second side wall, and an end wall between the first side wall and the second side wall, a first lug supported on the other of the sleeve and the bit, the first lug being positionable in the first slot through the opening in the first side wall of the first slot, the first lug being engageable with the end wall of the first slot to restrict axial movement of the bit from the sleeve and away from the casing, a second axial slot defined by one of the sleeve and the bit, the second slot having an axially-extending first side wall defining an opening, an opposite second side wall, and an end wall between the first side wall and the second side wall, and a second lug supported on the other of the sleeve and the bit, the second lug being positionable in the second slot through the opening in the first side wall of the second slot, the second lug being engageable with the end wall of the second slot to restrict axial movement of the bit from the sleeve and away from the casing. In such constructions, the head of the bit has an outer circumferential surface, the first slot and the second slot are defined on the outer circumferential surface of the head of the bit, and the first lug and the second lug are supported by the sleeve.
In some constructions, the retainer assembly includes a plurality of axial slots defined by one of the sleeve and the bit, each of the slots having an axially-extending first side wall defining an opening, an opposite second side wall, and an end wall between the first side wall and the second side wall, the plurality of slots being circumferentially spaced about the one of the sleeve and the bit, a corresponding plurality of lugs supported on the other of the sleeve and the bit, each of the lugs being positionable in a corresponding one of the slots through the opening in the first side wall of the corresponding one of the slots, each of the lugs being engageable with the end wall of the corresponding one of the slots to restrict axial movement of the bit from the sleeve and away from the casing. The retainer assembly may include four slots and four lugs.
The retainer assembly may further include a transverse slot extending at least partially circumferentially about the one of the sleeve and the bit, the transverse slot communicating with the axial slot through the opening in the side wall of the axial slot, the lug being movable into and through the transverse slot into the axial slot. The retainer assembly may also further include an axial entry slot having an open axial end, the lug being axially engageable in the entry slot through the open axial end, and wherein the transverse slot communicates between the entry slot and the axial slot. The entry slot may have a closed axial end opposite the open axial end, and the transverse slot may communicate with the entry slot proximate the closed axial end.
The axial slot has an axial second end wall opposite the first-mentioned end wall, the opening in the side wall being between the first-mentioned end wall and the second end wall. The lug has an axial height, and the opening in the first-mentioned side wall is sized to closely fit the axial height of the lug.
In another embodiment, the invention may provide an earth-boring drill assembly generally including a casing having a central axis, a bit having a generally cylindrical head and a shank connected to the head, a chuck connected to the casing, the chuck being connected to the shank of the bit, and a retainer device. The retainer device may include an annular sleeve connectable to the chuck, and a retainer assembly provided between the sleeve and the bit. The retainer assembly generally includes an axial slot defined by one of the sleeve and the bit, the slot having an axially-extending side wall defining an opening and an axial end wall, and a lug supported on the other of the sleeve and the bit, the lug being positionable in the slot through the opening in the side wall, the lug being engageable with the end wall to restrict axial movement of the bit from the sleeve and away from the casing. In some constructions, the chuck and the sleeve include inter-engaging surfaces to axially retain the sleeve on the chuck.
During operation of the drill assembly, the bit moves an axial distance between a first operating position and a second operating position, the lug has an axial height, and the slot has an axial length greater than the total of the axial distance and the axial height of the lug. During operation of the drill assembly, the bit moves a circumferential distance between a first operating position and a second operating position, the lug has a circumferential width, and the slot has a circumferential width greater than the total of the circumferential distance and the circumferential width of the lug.
During operation of the drill assembly, the bit moves axially between a first operating position and a second operating position, and the slot and the lug are dimensioned such that the lug is engageable with the end wall of the slot in an axial position of the bit axially beyond the first operating position and the second operating position. During operation of the drill assembly, the bit moves circumferentially between a first operating position and a second operating position, the slot has a second side wall opposite the first-mentioned side wall, and the slot and the lug are dimensioned such that the lug is engageable with first-mentioned side wall of the slot in a circumferential position of the bit circumferentially beyond the first operating position and with the second side wall of the slot in a circumferential position of the bit circumferentially beyond the second operating position.
In a further embodiment, the invention may provide a method of retaining a drill bit for an earth-boring drill assembly, the drill assembly including a casing having a central axis, the bit having a generally cylindrical head. The method generally includes connecting an annular sleeve to the casing; and engaging a retainer assembly provided between the sleeve and the bit, the retainer assembly including an axial slot defined by one of the sleeve and the bit, the slot having an axially-extending first side wall defining an opening, an opposite second side wall, and an end wall between the first side wall and the second side wall, and a lug supported on the other of the sleeve and the bit. The act of engaging includes positioning the lug in the slot through the opening in the first side wall, and engaging the lug with the end wall to restrict axial movement of the bit from the sleeve and away from the casing.
In yet another embodiment, the invention may provide a method of operating a down hole drill, the method generally including the steps of providing a bit having first and second opposite ends and defining a longitudinal axis extending between the first and second ends; the bit including a working surface at the first end, an enlarged diameter head at the second end, external splines, a shank portion between the enlarged diameter head and the external splines and having an outer diameter smaller than the outer diameter of the enlarged diameter head, and a retention portion between the working surface and the external splines, an external surface of the retention portion defining a first retaining surface, providing a drill assembly that includes a casing, a chuck having internal splines, a split ring having an inner diameter larger than the outer diameter of the shank portion of the bit but smaller than the outer diameter of the enlarged diameter head of the bit, and a retention sleeve interconnected to the casing, an internal surface of the retention sleeve defining a second retaining surface, providing in one of the first and second retaining surfaces an axially-extending entry slot having at least one open end, an axially-extending retaining slot having at least one closed end, and a circumferentially-extending transverse slot communicating between the entry slot and transverse slot, and providing on the other of the first and second retaining surfaces a lug.
The method also includes coupling the bit and drilling assembly with the split ring surrounding a portion of the shank portion to resist axial removal of the bit from the drilling assembly due to abutment of the split ring and the enlarged diameter head, the chuck surrounding a portion of the external splines such that the external splines mesh with the internal splines to transfer torque from the drilling assembly to the bit, and with the lug received in the entry slot through axial movement of the lug through the open end, and moving the lug from the entry slot to the retaining slot by axially aligning the lug with the transverse slot and causing relative rotation between the bit and retention sleeve, operating the down hole drill in a hole with the lug in the retaining slot such that substantially no axial loading and substantially no torque loading is transferred between the lug and retaining slot.
In addition, the method includes, during operation of the down hole drill in the hole, breaking the bit at the shank portion such that the split ring does not resist axial movement of the first end of the bit out of the drilling assembly, raising the drilling assembly out of the hole, and, while raising the drilling assembly, bringing the lug and closed end of the retaining slot into abutment to raise the first end of the bit out of the hole with the drilling assembly.
One or more independent aspects of the invention will become apparent by consideration of the detailed description, claims and accompanying drawings.
Before any independent embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other independent embodiments and of being practiced or of being carried out in various ways.
Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
A down-hole drill assembly 10 is partially illustrated in the drawings. For the sake of simplicity and consistency, the term “axial” means in a direction along or parallel to a central axis 14 of the drill assembly 10 illustrated in the drawings. The elements of the drill assembly 10 discussed below are generally ring-shaped or cylindrical and therefore all have inner and outer surfaces. The term “inner surface” means the surface facing toward the central axis 14 or generally toward the inside of the drill assembly 10, and the term “outer surface” means the surface facing away from the central axis 14 or generally away from the inside of the drill assembly 10. All elements also have first and second ends which, using the convention of the illustrated construction, will be referred to as “top” and “bottom” ends with respect to the typical operating orientation of the drill assembly 10, which orientation is illustrated in
The drill assembly 10 may have both rotary and impact aspects to the drilling operation or may be embodied in a pure down-the-hole (“DTH”) drill arrangement in which there is no rotary component. The drill assembly 10 may use substantially any type of drill bit, including a standard bit, drag bit, rotary bit, or another cutting surface suitable for or adaptable to impact loading.
In the illustrated construction, the drill assembly 10 generally includes a casing 18 (shown in
The casing 18 has a bottom end surface 38, and internal threads 42 are defined proximate the bottom end. As shown in
The chuck 22 defines (see
The bit 26 generally includes a shank 78 providing an anvil, an intermediate portion with external splines 82, and a head 86 having an exterior working surface to bear against rock or other material to be drilled. The bit shank 78 defines an annular groove 90 providing oppositely-facing stopping surfaces 94. When the bit 26 is assembled into the chuck 22, a split ring 98 (see
In the illustrated construction, the bit 26 is integrally formed to include the shank 78, intermediate portion and the head 86. In other constructions (not shown), the bit 26 could be formed as a bit retainer having suitable connecting apparatus for receiving a rotary drill bit (e.g., a tricone) or other suitable work piece for rock drilling.
As shown in FIGS. 2 and 4-8, the retainer assembly 30 generally includes a retainer sleeve 106 and an arrangement of inter-engaging lug(s) 110 and slot(s) 114. The sleeve 106 has an inner wall 118 defining a central bore 122. At the upper end surface 126, a key recess 130 is provided and is alignable with the key recess 62. The sleeve 106 also has an inner shoulder 138.
In the illustrated construction, the inner wall 118 of the sleeve 106 is machined to be formed with four (4) lugs 110, and the outer surface of the bit head 86 is formed with four (4) corresponding slots 114. As described below in more detail, each lug 110 is engageable in a corresponding slot 114. In the illustrated construction, the lugs 110 and slots 114 are equally spaced about the circumference of the sleeve 106 and the bit head 86, respectively.
It should be understood that fewer or more than four (4) lugs 110 and slots 114 may be provided. Also, in other constructions (not shown), the lug(s) 110 may be provided on the bit head 86, and the slot(s) 114 may be provided on the sleeve 106. In addition, corresponding numbers of lug(s) 110 and slot(s) 114 could be formed on each of the bit head 86 and the other structure (e.g., the sleeve 106). Further, in other constructions (not shown), a sleeve 106 may not be provided, and the lug(s) 110 and/or the slot(s) 114 may be provided on another structure (e.g., on a portion of the chuck 22).
It should be understood that the lug(s) 110 may be separate from and connectable (e.g., by welding) to the supporting structure (e.g., to the sleeve 106 or to the bit head 86). Also, in other constructions (not shown), the lug(s) 110 and the slot(s) 114 may be un-equally spaced about the circumference of and/or staggered along the axis of the sleeve 106 and the bit head 86, respectively, such that the lug(s) 110 and slot(s) 114 are only engageable in a limited number (e.g., one) of rotational positions of the bit head 86 relative to the sleeve 106.
In the illustrated construction, each slot 114 includes several slot portions including an axial retainer slot 142, a transverse slot 146 and an entry slot 150. The retainer slot 142 has at least one closed end to prevent movement of the lug 110 from at least that end of the retainer slot 142. As shown in
The transverse slot 146 communicates with the retainer slot 142 through the opening 170 in the side wall 154. The entry slot 150 has at least one open end to allow movement of the lug 110 into/out of at least that end of the entry slot 150. The entry slot 150 has an entry port or open axial end 174 providing the at least one open end. The entry slot 150 communicates with the transverse slot 146 proximate its closed axial end 178. In the illustrated construction, each slot 114 generally has the shape of a reversed “4”.
In other constructions (not shown), each slot 114 may include fewer or more slot portions. For example, each slot 114 may include only a retainer slot 142 with an opening 170 for passage of the lug 110 into the retainer slot 142. In other constructions (not shown), each slot 114 may have a “J” shape.
To assemble, the bit shank 78 is inserted into the chuck bore 50, and the splines 54 and 82 are engaged or mesh such that torque may be transmitted from the chuck 22 to the bit 26. The split ring 98 is positioned in the annular groove 90 to connect the bit 26 to the chuck 22. For normal operations, axial movement is provided between the bit 26 and the chuck 22 while the splines 54 and 82 remain in torque-transmitting engagement. Engagement of the split ring 98 with the opposite stopping surfaces 94 limits this axial movement.
After (or before) connection of the bit 26 and the chuck 22, the sleeve 106 is lowered axially onto upper end 58 the chuck 22. Each lug 110 passes axially through an associated slot 70 in the outer surface of the chuck 22. Engagement of the inner shoulder 138 on the sleeve 106 with the outer shoulder 66 on the chuck 22 prevents further downward axial movement.
To engage the retainer assembly 30, each lug 110 enters the open axial end 174 of the entry slot 150 of its associated slot 114 and moves toward the closed axial end 178 as the bit 26 and sleeve 106 are moved axially relative to one another (as shown in
Once the lug 110 is fully in the retainer slot 142, the bit 26 may move axially relative to the sleeve 106 and relative to the chuck 22 (as shown in
With the chuck 22, the bit 26 and the retainer assembly 30 assembled, the unit is connected to the casing 18 by threading the chuck threads 46 into the casing threads 42 (as shown in
Operation of the drill assembly 10 is explained with partial reference to
With reference to
In operation, the drill assembly 10 has a rotary component (at least to change the engagement of teeth on the bit 26 with the bottom of the hole) and a percussive component. The impact of a piston (not shown) of the piston mechanism on the bit 26 is transmitted to the rock or other material being drilled, and the bit 26 moves axially in the chuck 22.
If the bit 26 fails during drilling operations, failure typically occurs in the shank 78 at the split ring 98, in the splines 82 or at the interface between the intermediate portion and the bit head 86. With such a failure, (see
As shown in
As shown in
In other constructions (not shown), the opening 170 may have a smaller axial height than the transverse slot 146. The transverse slot 146 may taper in height from the entry slot 150 toward the retainer slot 142.
The lug 110 and the retainer slot 142 are dimensioned and/or positioned on the supporting components (e.g., on the sleeve 106 and the bit 26) such that the lug 110 and the retainer slot 142 do not support and/or drive the bit 26 during operations. This arrangement ensures proper driving and/or support of the bit 26 while preventing wear and/or damage to the lug 110, the slot 114 and/or the supporting structure (the bit head 86 and the sleeve 106).
The retainer slot 142 has an axial height HR which is greater than the total of the height of the lug HL and the total axial movement of the bit 26 during drilling operations (as defined by the stopping surfaces 94 and the split ring 98). As shown in
Each lug 110 has a circumferential width WL. In the illustrated construction, the retainer slot 142 has a larger circumferential width WR such that the lug 110 will not engage the side walls 154 and 158 during normal operation of the drill assembly 10 (e.g., due to backlash in the splines 54 and 82). The width WR is at least larger than the total of the width WL of the lug 110 and the maximum circumferential movement in each direction of the bit head 86 relative to the sleeve 106. The circumferential width of the entry slot 146 may also be larger than the width WL of the lug 110 (as shown) to allow easy assembly or may fit more closely to the circumferential width WL of the lug 110.
One independent advantage of the present drill assembly 10 and retainer assembly 30 may be to provide structure to retain and retrieve a broken portion 182 of a bit 26. Such structure may be simple and/or inexpensive to manufacture, assemble and/or operate. Such structure may have improved operational reliability.
Thus, the invention provides, among other things, a retainer device for a drill bit for an earth-boring drill assembly. The invention also provides an earth-boring drill assembly. In addition, the invention provides a method of retaining a drill bit for an earth-boring drill assembly. Further, the invention provides a method of operating a down hole drill. Various independent features and independent advantages of the invention are set forth in the following claims.
