HAMMER BIT LOCKING MECHANISM

Abstract

A hammer bit retainer system includes a hammer bit locking mechanism arranged and designed to prevent decoupling of a driver sub from a hammer casing. The hammer bit locking mechanism includes an expandable split ring which is disposed in the coupling between the driver sub and hammer casing. The hammer bit locking mechanism prevents axial movement of the driver sub relative to the hammer casing in at least one direction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of related U.S. Provisional Application Ser. No. 61/654,498 filed Jun. 1, 2012, titled “Hammer Bit Locking Mechanism,” to Bhatia et al. and U.S. Provisional Application Ser. No. 61/747,691 filed Dec. 31, 2012, titled “Hammer Bit Locking Mechanism,” to Bhatia et al., the disclosures of which are incorporated by reference herein in their entirety.

BACKGROUND

Percussion bit assemblies are often used in drilling or boring through the Earth's surface. In a percussion bit assembly, a percussion hammer is used to drive a percussion bit into the ground. The percussion hammer uses the reciprocating action of a piston to energize the bit.

FIG. 1 illustrates a conventional percussion bit assembly 100. The percussion bit assembly 100 includes a hammer case 122 that connects to a lower end of a drill string (not shown) through a threaded pin connection 102. The lower end of the hammer case 122 is threadably engaged 144 with a driver sub 140. A plurality of splines (not shown) disposed on the driver sub 140 engage a plurality of splines 116 disposed on a shank 114 of a hammer bit 110, and rotate to drive the bit 110. A retainer 160, e.g., a conventional split ring, is disposed around an upper end of the shank 114 of the hammer bit 110 and abuts the driver sub 140. The retainer 160 retains the hammer bit 110 in the percussion bit assembly 100. The retainer 160 may be held in place, initially, by an elastic ring 106, or o-ring, to facilitate assembly of the bit 110 and driver sub 140 with the hammer case 122. The retainer 160 is confined by the inner wall of the hammer case 122 to maintain ring-to-bit engagement. The upper end of the hammer bit 110 includes a piston strike surface 108 and a foot valve 104, or blow tube. The lower end of the hammer bit 110 includes a head 112.

During certain operations performed with the percussion bit assembly 100, the drill pipe may reverse its rotation, thereby causing the driver sub 140 to back off, or unthread, from the hammer case 122. Occasionally, the driver sub 140 will unintentionally back off downhole due to torsional oscillations, known as “stick-slip” of the drill string. If the driver sub 140 backs off, the bit 110 and the driver sub 140 remain at the bottom of the borehole.

The drill string components, which may include a drill pipe, a bottomhole assembly, a driver sub, etc., may be coupled by various thread forms known as connections, or tool joints, any of which may unthread or back off. When a drill string becomes stuck downhole, the driver sub may unintentionally back off downhole, or the drill string may be backed off from the driver sub to recover as much of the drill string as possible. The back off may be intentionally accomplished by applying reverse torque and detonating an explosive charge inside a selected threaded connection. The back off may be also be accomplished by applying tension to the drill string and detonating an explosive charge, thereby allowing the threads to slide by each other without turning.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

A hammer bit locking mechanism is disclosed. The hammer bit locking mechanism includes a driver sub, a hammer casing and a locking device disposed therebetween. The driver sub is adapted to receive and movably couple to the shank of a bit, e.g., percussion bit. The driver sub also includes a portion having an outer surface with one or more grooves therein. The hammer casing has a central bore and receives at least a portion of the driver sub in its central bore. A locking device, e.g., an expandable split ring, is disposed between the hammer casing and a portion of the driver sub. The locking device includes an inner surface with one or more grooves therein configured to engage the one or more grooves in the outer surface of the portion of the driver sub. The locking device is further arranged and designed to prevent axial movement of the driver sub relative to the hammer casing in at least one direction.

A method of preventing the decoupling of coupled components of a percussion hammer bit is also disclosed. The method includes inserting a locking device, e.g., an expandable split ring, in a circumferential cavity positioned in a hammer casing and expanding the locking device. The method also includes inserting at least a portion of a driver sub into a central bore of the hammer casing and through the expanded locking device. The method further includes coupling the driver sub and the hammer casing such that one or more inner surface grooves of the locking device engage one or more outer surface grooves of the driver sub, thereby preventing axial movement between the driver sub and the hammer casing in at least one direction.

A locking mechanism of a downhole tool is also disclosed. The downhole tool includes a first body adapted to receive and movably couple to the shank of a bit, e.g., a percussion bit. The downhole tool also includes a second body having a central bore, which receives a portion of the first body in the central bore. A first split ring is disposed between the second body and a portion of the first body. The first split ring includes an inner surface with one or more grooves formed therein and an outer surface with one or more grooves formed thereon. The first split ring is arranged and designed to prevent axial movement of the first body relative to the second body in at least one direction. A second split ring is disposed radially within the first split ring. The second split ring includes an outer surface with one or more grooves formed thereon, which are configured to engage the one or more grooves in the inner surface of the first split ring.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts a cross-sectional view of a conventional hammer bit assembly.

FIG. 2 depicts a perspective view of an illustrative hammer bit locking mechanism in a hammer bit assembly, according to one or more embodiments disclosed

FIG. 3 depicts a cross-sectional view of the hammer bit locking mechanism of the hammer bit assembly of FIG. 2.

FIG. 4 depicts a perspective view of an illustrative hammer case of the hammer bit assembly, according to one or more embodiments disclosed.

FIG. 5 depicts a perspective view of an illustrative driver sub, according to one or more embodiments disclosed.

FIG. 6 depicts a perspective view of an illustrative expandable split ring, according to one or more embodiments disclosed.

FIG. 7 depicts the installation of an illustrative hammer bit locking mechanism in a hammer bit assembly, according to one or more embodiments disclosed.

FIG. 8 depicts the installation of the hammer bit locking mechanism of FIG. 7 during steady state operation.

FIG. 9 depicts the engagement of the hammer bit locking mechanism of FIG. 7 to prevent disassembly of the hammer bit assembly.

FIG. 10 depicts the removal of the hammer bit locking mechanism of FIG. 7 when disassembly of the hammer bit assembly is desired.

FIG. 11 depicts a perspective view of an illustrative lug disposed in conjunction with a hammer bit locking mechanism in a hammer assembly, according to one or more embodiments disclosed.

FIG. 12 depicts a perspective view of the lug of FIG. 11.

FIG. 13 depicts a perspective view of an illustrative hammer bit locking mechanism, according to one or more embodiments disclosed.

FIG. 14 depicts a perspective view of the hammer casing of FIG. 13.

FIG. 15 depicts a perspective view of the expandable split ring of FIG. 13.

FIG. 16 depicts a cross-section view of an illustrative hammer bit locking mechanism, according to one or more embodiments disclosed.

FIG. 17 depicts a perspective view of the expandable split ring of FIG. 16.

FIG. 18 depicts a perspective view of a driver sub of FIG. 16.

FIG. 19 depicts a cross-sectional view of an illustrative hammer bit assembly having first and second split rings, where inner surface grooves of the first split ring cover about 100% of an axial length of the first split ring and outer surface grooves of the second split ring cover about 100% of an axial length of the second split ring, according to one or more embodiments disclosed.

FIG. 20 depicts a cross-sectional view of the illustrative hammer bit assembly, where the inner surface grooves of the first split ring cover about 75% of the axial length of the first split ring and the outer surface grooves of the second split ring cover about 75% of the axial length of the second split ring, according to one or more embodiments disclosed.

FIG. 21 depicts a cross-sectional view of the illustrative hammer bit assembly, where the inner surface grooves of the first split ring cover about 50% of the axial length of the first split ring and the outer surface grooves of the second split ring cover about 50% of the axial length of the second split ring, according to one or more embodiments disclosed.

FIG. 22 depicts a cross-sectional view of the illustrative hammer bit assembly, where the inner surface grooves of the first split ring cover about 25% of the axial length of the first split ring and the outer surface grooves of the second split ring cover about 25% of the axial length of the second split ring, according to one or more embodiments disclosed.

FIG. 23 depicts a cross-sectional view of the illustrative hammer casing, where the second split ring has been omitted and the outer surface grooves in the first split ring have been omitted, according to one or more embodiments disclosed.

FIG. 24 depicts a cross-sectional view of the illustrative hammer casing, where the outer surface grooves in the first split ring have been omitted, according to one or more embodiments disclosed.

DETAILED DESCRIPTION

The following is directed to various illustrative embodiments of the disclosure. The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, those having ordinary skill in the art will appreciate that the following description has broad application, and the discussion of any embodiment is meant only to be illustrative of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims refer to particular features or components. As those having ordinary skill in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion and, thus, should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first component is coupled to a second component, that connection may be through a direct connection, or through an indirect connection via other components, devices, and connections. Further, the terms “axial” and “axially” generally mean along or parallel to a central or longitudinal axis, while the terms “radial” and “radially” generally mean perpendicular to a central longitudinal axis.

Additionally, directional terms, such as “above,” “below,” “upper,” “lower,” etc., are used for convenience in referring to the accompanying drawings. In general, “above,” “upper,” “upward,” and similar terms refer to a direction toward the Earth's surface from below the surface along a borehole, and “below,” “lower,” “downward,” and similar terms refer to a direction away from the surface along the borehole, i.e., into the borehole, but is meant for illustrative purposes, and the terms are not meant to limit the disclosure.

Referring generally to FIG. 2, a hammer bit locking mechanism 220 is disclosed. The hammer bit locking mechanism 220 may include a driver sub 240 adapted to receive and movably couple to the shank 114 of a bit 110 (not shown but see, e.g., FIG. 1). The driver sub 240 may include a portion having an outer surface with one or more grooves 246 therein. A hammer casing 222 may have a central bore 230 and receive the portion of the driver sub 240 in the central bore 230 (FIG. 3). An expandable split ring 260 may be disposed between the hammer casing 222 and the portion of the driver sub 240. The expandable split ring 260 may include an inner surface with one or more grooves 264 (FIG. 6) therein configured to engage the one or more grooves 246 in the outer surface of the portion of the driver sub 240. The expandable split ring 260 may be arranged and designed to prevent axial movement of the driver sub 240 relative to the hammer casing 222 in at least one direction.

One or more embodiments disclosed herein relate to a hammer bit locking mechanism 220 in a hammer assembly 200. Such hammer bit locking mechanism 220 acts to prevent vibration-initiated back offs (i.e., loosening and separation) of the hammer bit threaded connection. As used herein, the term “back off” refers to the unscrewing of drill string components downhole. Referring generally to FIGS. 2-6, an illustrative hammer bit locking mechanism 220 and components thereof in accordance with one or more embodiments of the present disclosure are shown. As shown in FIGS. 2 and 3, and as will be disclosed in greater detail hereinafter, a first body 240 is threadably coupled to an end portion (e.g., lower end portion) 236 of a second body 222. The first body 240 may be a generally cylindrical driver sub, and the second body 222 may be a hammer casing 222, and the first and second bodies 240, 222 are referred to as such in the following description.

As best shown in FIGS. 3 and 4, the hammer assembly 200 has a generally cylindrical casing 222 with a central bore 230 therethrough and internal threads 228 on an inner surface thereof. In FIG. 3, a circumferential cavity 238 is defined within the central bore 230 between the inner surface of the hammer casing 222 and the outer wall of the driver sub 240. The inner surface of the hammer casing 222, defining the circumferential cavity 238, may have one or more female grooves 226 formed therein. The female grooves 226 may be configured having groove profiles such as square, trapezoidal, triangular, round or elliptical, and other profiles known to those skilled in the art. The groove profiles may be configured having chamfers on the root or crest interfaces or both. In one or more embodiments, the groove profiles may be symmetrical, while in other embodiments, the groove profiles may be asymmetrical. Further still, the groove profiles may be configured in a hooked configuration.

Returning to FIG. 2, the hammer casing 222 of the hammer assembly 200 further includes an access window 224 disposed in an outer wall thereof for access to the central bore 230, e.g., when the driver sub 240 is not present, and the circumferential cavity 238, e.g., when the driver sub 240 is present. The access window 224 is positioned to be substantially centered within an axial length of the circumferential cavity 238 formed when driver sub 240 is coupled to the lower end portion 236 of the hammer casing 222. The access window 224 may be any number of various shapes and configurations, for example, square, circular, etc. Further, to prevent ingress of foreign particles into the hammer casing 222, the access window 224 may be sealed with a resin or other sealing component, which may be removed from the access window 224 to provide access to the circumferential cavity 238.

As briefly disclosed above and best shown in FIGS. 2-3, the hammer assembly 200 includes a generally cylindrical driver sub 240 having external threads 248 on an outer surface 258 of an upper end portion 252 thereof (see, e.g., upper end portion 252 of driver sub 240 shown in FIG. 5). As shown in FIGS. 3 and 4, the external threads 248 are configured to engage internal threads 228 on an inner surface of the hammer casing 222. The driver sub 240 is configured to be stabbed (i.e., inserted) into the hammer casing 222, and the external threads 248 are configured to be threadably engaged with the corresponding internal threads 228 of the hammer casing 222. As best shown in FIG. 5, the driver sub 240 further includes a series of external circumferential grooves 246 on an outer surface 258 thereof. In one or more embodiments, the external circumferential grooves 246 are located proximate the external threads 248 in a substantially central region 254 of the driver sub 240 along an axial length thereof. The circumferential external grooves 246 of the driver sub 240 may be configured having symmetrical or asymmetrical groove profiles. Thus, in one embodiment, the driver sub external grooves 246 may have a “saw tooth” groove profile. In another embodiment, the external grooves 246 may be configured having a “hooked” configuration.

In one or more embodiments, the driver sub 240 may be tapered along an axial length thereof from its upper end portion 252 towards its lower end portion 256. In other words, the upper end portion 252 of the driver sub 240 may have an initial diameter that gradually increases axially toward the lower end portion 256. Thus, the driver sub 240 may have a somewhat conical axial profile. In tapered driver sub embodiments, such taper may have an angle of between 0 degrees and 30 degrees, between 0 degrees and 10 degrees, or between 0 degrees and 5 degrees. The taper of the driver sub 240 may be used to expand a locking device 260 (not shown), during assembly, as will be described in further detail below. For example, and returning to FIG. 3, the tapered profile of the driver sub 240 may expand a locking device 260 positioned circumferentially about the driver sub 240 during assembly of the hammer casing 222 and the driver sub 240. In another embodiment, the driver sub 240 may be tapered along its axial or longitudinal length on one axial or longitudinal side (i.e., in one hemisphere), while the other side (i.e., opposite hemisphere) is substantially perpendicular between upper and lower end faces thereof.

The hammer bit locking mechanism 220 further includes a locking device 260 (shown in FIG. 6) disposed in the circumferential cavity 238 of the hammer casing 222. In one or more embodiments, the locking device 260 is an expandable split ring, as further disclosed below. Within the circumferential cavity 238, the locking device 260 is arranged and designed to engage an outer surface 258 of the driver sub 240 at external circumferential grooves 246 and an inner surface of the hammer casing 222 at female grooves 226. As will be discussed in greater detail hereinafter, this engagement of the locking device 260 with external circumferential grooves 246 and female grooves 226 acts to prevent the threaded connection (i.e., corresponding external threads 248 and internal threads 228) between the hammer casing 222 and the driver sub 240 from backing off (i.e., rotating and separating).

As illustrated in FIG. 6, an expandable split ring embodiment of locking device 260 includes grooves 262 on an outer surface thereof (i.e., outer surface grooves 262) and grooves 264 on an inner surface thereof (i.e., inner surface grooves 264). The outer surface grooves 262 of the split ring 260 are configured to engage corresponding internal grooves 226 of the hammer casing 222. In one or more embodiments, the outer surface grooves 262 of the split ring 260 may have coarser grooves with a larger pitch (i.e., fewer grooves per axial distance) than the inner surface grooves 264 of the split ring 260. In another embodiment, the inner surface grooves 264 of the split ring 260 may have coarser grooves having a larger pitch than the outer surface grooves 262 of the split ring 260. In still further embodiments, the outer surface grooves 262 and the inner surface grooves 264 of the split ring 260 may have grooves of substantially equal pitch. The outer surface grooves 262 of the split ring 260 may be configured having groove profiles which are square, trapezoidal, triangular, round or elliptical, and of other profiles known to those skilled in the art. Further, these groove profiles may be symmetrical or asymmetrical. In one or more embodiments, the outer surface grooves 262 are arranged and designed with chamfers at either or both root and crest interfaces.

The inner surface grooves 264 of the split ring 260 are arranged and designed to engage corresponding external grooves 246 on the outer surface 258 of the driver sub 240. In one or more embodiments, the inner surface grooves 264 are fine-pitched with respect to the outer surface groove 262 and, thus, configured to engage similarly fine-pitched external grooves 246. The inner surface grooves 264 may have a symmetrical or asymmetrical groove profile. In one such asymmetrical embodiment, the inner surface grooves 264 may have a “hooked” groove configuration. In another such asymmetrical embodiment, the inner surface grooves 108 have a “saw tooth” groove profile but with a tapered surface that peaks at a substantially radially vertical surface, and which corresponds with a groove profile of circumferential grooves 246. Engagement of the asymmetrical groove profile of the inner surface grooves 264 of the split ring 260 with corresponding outer surface grooves 246 of the driver sub 240 permits axial movement of the driver sub 240 in one direction (i.e., threading), thus preventing axial movement of the driver sub 240 in the opposite direction (i.e., unthreading), as will be disclosed in greater detail hereinafter.

Turning now to FIG. 7, the assembly of the locking device 260 within the circumferential cavity 238 between the lower end portion 236 of the hammer casing 222 and the upper end portion 252 of driver sub 240 is illustrated in a cross-sectional view. When the driver sub 240 is installed/stabbed into the hammer casing 222, the driver sub 240 will move relative to the hammer casing 222 in the direction of arrow 266. The driver sub 240 engages the split ring 260, such that the split ring 260 is expanded over the outside surface of driver sub 240. As disclosed previously, the driver sub 240 may be tapered to facilitate this expansion. The external circumferential grooves 246 permit relative motion between driver sub 240 and the split ring 260 to occur in one direction. The orientation of ramp 276 on the external circumferential grooves 246 with the corresponding ramp 286 on the inner surface grooves 264 of the split ring 260 permits the diameter of the split ring 260 to enlarge as the ramps 276, 286 slide past each other. The contact interface of the ramps 276, 286, being in a non-perpendicular orientation relative to axial movement (as indicated by arrow 266), permits the relative motion between the split ring 260 and the driver sub 240 to in turn provide sufficient radial force on the split ring 260 to expand the diameter of the split ring 260, thereby facilitating the driver sub 240 movement in the direction of arrow 266 relative to the split ring 260.

On the opposite side of the split ring 260, the outer surface grooves 262 of the split ring 260 engage the female grooves 226 of the hammer casing 222. The outer surface grooves 262 and female grooves 226 have a corresponding set of flats, i.e., 288, 298 on the outer surface grooves 262 and female grooves 226, respectively, which are perpendicular to the movement of the driver sub 240, as shown by arrow 266. The outer surface grooves 262 also have ramps, e.g., 294 on the female grooves 226, which correspond to the ramps, e.g., 284 on the outer surface grooves 262. When the driver sub 240 is moving in the direction of arrow 266, the flats 288, 298 on the outer surface grooves 262 and female grooves 226, respectively, are engaged such that the axial movement of the split ring 260 relative to the driver sub 240 in the direction of arrow 266 is arrested. However, when the driver sub 240 is moving in the direction of arrow 266, the flats 288, 298 are engaged such that perpendicular movement relative to arrow 266 is permitted, and the ramps 246, 264 may climb past each other during assembly/stabbing of the driver sub 240 in the hammer casing 222.

The hammer bit locking mechanism 220 is assembled such that the driver sub 240 is inserted/stabbed into the hammer casing 222 with the locking device 260 disposed in the circumferential cavity 238 between an inner surface of the hammer casing 222 and an outer surface of the driver sub 240, as best shown in FIG. 8. In this steady state illustration, the ramp 286 and the flat 282 of the split ring 260 constrict around and settle into mating contact with the ramp 276 and the flat 272 of the driver sub 240. In this steady state position, the ramp 294 and the flat 298 on the female grooves 226 of the hammer casing 222 may not be in engaging contact with corresponding/mating ramp 284 and flat 288 on the outer surface grooves of the locking device 260. In one or more embodiments, a slight amount of clearance may exist between these aforementioned corresponding surfaces. The steady state position, as illustrated in FIG. 8, is the service position when the assembly 200 is in operational use and the anti-back feature of the locking mechanism 220 is not engaged.

When the assembly 200 is in operation, severe vibration and/or improper operational practices may create an undesirable condition in which the driver sub 240 begins to move in the direction of arrow 268, as illustrated in FIG. 9. This motion, in the direction of arrow 268, is created when the driver sub 240 begins to rotate and unthread itself from the hammer casing 222 at corresponding engaged threads 228, 248 (see, e.g., FIG. 3). If left unabated, the driver sub 240 will free itself from the hammer casing 222 and become separated from the hammer casing 222. However, when the locking mechanism 220 of one or more embodiments of the present disclosure is employed, the unabated movement of the driver sub 240 in the direction of arrow 268 is prevented, as further disclosed hereinafter.

Continuing with FIG. 9, if the driver sub 240 begins to loosen from the hammer casing 222, the driver sub 240 moves axially in the direction of arrow 268 relative to the hammer casing 222. However, in this movement direction 268, the split ring 260 is mechanically locked by the contact of the flats 272 of the external circumferential grooves 246 of the driver sub 240 and the flats 282 of the inner surface grooves 264 of the split ring 260, such that both the driver sub 240 and the split ring 260 move together as a single unit. Such unified axial movement will continue freely until arresting contact is made between the ramps 294 on the female grooves 226 of the hammer casing 222 and the ramps 284 on the outer surface grooves 262 of the split ring 260. If additional force is applied to the driver sub 240 in the direction of arrow 268, the ramps 294, 284 engage further forcing the split ring 260 to apply a hoop stress around the driver sub 240, such that the mating contacting force of the flats 272, 282 is increased. Due to the hoop stress created by the ramps 294, 284 acting on the flats 272, 282, a mechanical lock is generated between the driver sub 240, the split ring 260 and the hammer casing 222, thereby halting any further axial movement of the driver sub 240 in the direction of arrow 268 relative to the hammer casing 222.

The split ring 260 may be expandable (i.e., a diameter of the split ring 260 may be enlarged from an initial collapsed diameter) and may be configured having two end portions with a gap therebetween to allow the split ring 260 to radially expand. The split ring 260 may be configured to radially expand to up to about 10%, up to about 20% or up to about 30% of its original unexpanded diameter in one or more embodiments. The split ring 260 may be a circular band configured having a rectangular cross-section with substantially concentric inner and outer surfaces (i.e., concentric diameters). In one or more other embodiments, the split ring 260 may be configured having non-concentric inner and outer surfaces (i.e., non-concentric diameters). For example, a cross-sectional thickness of the split ring 260 may be tapered along a width of the split ring 260 cross-section. In one or more other embodiments, the locking device 260 may be a two-piece split ring which is installed separately to form a single locking device 260 in the circumferential cavity 238. In still other embodiments, the split ring 260 may have a wedge-shaped cross-section.

As illustrated in FIG. 10, to remove the driver sub 240 from the hammer casing 222 when the split ring 260 is in place (e.g., to service the assembly 200) the split ring 260 is expanded such that the ramps 276, 286 as well as the flats 272, 282 are separated with a sufficient clearance to permit the driver sub 240 to move in the direction of arrow 268 without contacting the split ring 260. Such separation is accomplished using a spreading tool inserted into access window 224 (not shown in FIG. 9; see, e.g., FIG. 2) and in between the split 270 of the split ring 260 (FIG. 6). A separation force is applied to spread the two end portions of the split ring 260, thereby increasing the diameter of the split ring 260. At a maximum separation of the end portions of the split ring 260, the ramps 294, 284 as well as the flats 288, 298 will be in mating contact. This expanded diameter of the split ring 260 provides the maximum clearance between the split ring 260 and the driver sub 240 and provides more than adequate clearance between the split ring 260 and the driver sub 240 to unthread driver sub 240 from the split ring 260 at corresponding engaged threads 228, 248 (see, e.g., FIG. 3).

In certain embodiments, the split ring 260 may be manufactured from alloy steel. For example, steel may be alloyed with a variety of elements in total amounts of between 1.0% and 50% by weight to improve its mechanical properties (e.g., strength, toughness, hardness, wear resistance, hardenability). In certain embodiments, the split ring 260 may be heat treated. Common alloys that may be used include, but are not limited to, manganese, nickel, chromium, molybdenum, vanadium, silicon and boron. Other alloys that may be used include, but are not limited to, aluminum, cobalt, copper, cerium, niobium, titanium, tungsten, tin and zirconium. In other embodiments, the split ring 260 may be manufactured from a non-alloy steel. In still other embodiments, the split ring 260 may be manufactured from other metallic materials. In further embodiments, the split ring 260 may be manufactured from non-metallic materials.

Now turning to FIGS. 11 and 12, a lug 290 or other device may be disposed along with the split ring 260 to prevent the split ring 260 from rotating after disposing the split ring 260 within the circumferential cavity 238 (i.e., the end portions of the split ring 260 remain in position at the access window 224 in the hammer casing 222). As illustrated in FIG. 11, the lug 290 may be disposed in the access window 224 of the hammer casing 222. The lug 290 may be press fit into the access window 224 from inside the hammer casing 222 before the driver sub 240 is inserted into the hammer casing 222. The split ring 260 is disposed in the circumferential cavity 238 such that the end portions of the split ring 260 may abut a middle section 292 of the lug 290. In one or more embodiments, the lug 290 is arranged and designed to fill the void of the split 270 of the split ring 260 such that the middle section 292 and the extended flats 291 of the lug 290 are disposed between the end portions of the split ring 260. With the middle section 292 of the lug 290 captured in the access window 224, the split ring 260 is thus prevented from rotating in either direction while installed in the circumferential cavity 238 of the hammer casing 222. The middle section 292 of the lug 290 may also have an aperture 293 through which an expander device (described in more detail hereinafter) may be inserted for expanding the split ring 260. In one or more embodiments, the aperture 293 may be internally threaded.

The lug 290 may be an alloy steel material in one or more embodiments. In another embodiment, the lug 290 may be made from other materials or a composite of materials. As disclosed above, the lug 290 may have extended flats 291 on both sides of its middle section 292. In one or more other embodiments (not shown), the lug 290 may not have any extended flats 291, or in still one or more other embodiments (not shown), the lug 290 may have one extended flat 291 on one side of its middle section 292. In such embodiments, the middle section 292 may be arranged and designed to more fully fill the void left by space 270 of split ring 260. In other embodiments, the lug 290 may have external coarse grooves (not shown) configured to mate with female grooves 226 of the hammer casing 222.

Referring back to FIGS. 7-9, and as previously disclosed, the locking mechanism 220 may be configured to allow relative axial and rotational movement between the hammer casing 222 and the driver sub 240 in one direction (i.e., the driver sub 240 may be allowed to move axially inward into the hammer casing 222), while preventing axial movement in an opposite direction (i.e., the driver sub 240 is prevent from moving axially outward away from the hammer casing 222). Stated otherwise, the split ring 260, inserted into the circumferential cavity 238, allows the driver sub 240 to be stabbed and threaded into the hammer casing 222, but keeps the driver sub 240 from backing out of the hammer casing 222 in the event the threaded connection (i.e., hammer casing threads 228 and driver sub threads 248) becomes loose during operation due to the ratchet engagement between the inner surface grooves 264 of the split ring 260 (FIG. 6) and outer surface threads 246 of the driver sub 240.

FIGS. 13-15 depict an illustrative locking mechanism 320, according to one or more embodiments. The driver sub 340 is stabbed and threaded into a hammer casing 322 (threaded connection not shown), and a split ring 360 is installed therebetween to prevent the driver sub 340 from backing off. As shown in FIG. 15, the split ring 360 includes extensions 361 which may be accessed through a slot 325 (FIG. 13) of the hammer casing 322 when the split ring 360 is disposed between the driver sub 340 and the hammer casing 322. The extensions 361 may include one or more small holes/apertures 363 or other features to allow a hand tool or expander device (e.g., pliers) to engage the extensions 361 and expand (or contract) the split ring 360. In one or more embodiments, the extensions 361 may be integrally formed with the split ring 360. In another embodiment, the extensions 361 may be separately formed and coupled to the split ring 360, for example, by welds, adhesives, brazing or other known methods. Still further, the extensions 361 may be configured in any number of shapes, including square (as shown), circular or other polygonal shapes. The extensions 361 may be rounded (by grinding or machining) to provide any type of shape or configuration to fit within the hammer casing 322 without interfering with other components but while also being easily accessible for expanding. The holes/apertures 363 through the extensions 361 may be sized and/or shaped to accommodate any type of tool configuration that may be used to expand (or contract) the split ring 360.

FIGS. 16-18 depict an illustrative locking mechanism 420, according to one or more embodiments. The split ring 460 shown in FIG. 17 has outer surface grooves 462; however, the split ring 460 has no grooves on the inner surface. Rather, the split ring 460 has a smooth inner surface 465. Outer surface grooves 462 of the split ring 460 may engage female grooves 426 in the circumferential cavity 438 of the hammer casing 422, while the smooth inner surface 465 of the split ring 460 is configured to engage a smooth mating groove 445 (shown in FIG. 16) machined on the outer diameter of the driver sub 440. The mating groove 445 may be configured to correspond with an inner surface of the split ring 460.

As will be described below in FIGS. 19-24, a multi-piece split ring may include two cooperating split rings that are engaged by ramps and grooves. A ratio of a length of the ramps and grooves of a first split ring to a length of the ramps and grooves of a second split ring may be pre-set to provide a predetermined break-out torque. For example, in one or more embodiments, a shear force used to shear grooves formed between the first split ring and the second split ring may be predetermined by a ratio between a length of outer surface grooves formed on the first split ring that are engaged with the hammer casing and the length of the grooves formed between the first split ring and the second split ring. As such, the hammer casing may be torqued in excess of the predetermined break-out torque threshold relative to the driver sub such that the grooves formed between the first split ring and the second split ring are sheared, and the hammer casing may be disengaged from the driver sub. Those having ordinary skill in the art will appreciate that embodiments show in FIGS. 19-24 can be combined with earlier embodiments discussed herein, such as the embodiments shown in FIGS. 1-18.

FIGS. 19-22 show cross-sectional views of one or more embodiments of an illustrative hammer assembly 200 having a hammer bit retainer system disposed within a circumferential cavity between a lower end portion 236 of the hammer casing 222 and an upper end portion of the driver sub 240, similar to the circumferential cavity 238 shown in FIGS. 3 and 4. In one or more embodiments, the hammer bit retainer system may be a multi-piece ring and may include a first split ring 260 and a second split ring 250 radially within the first split ring 260. The first split ring 260 may be configured to engage with the second split ring 250 within the circumferential cavity between the hammer casing 222 and the driver sub 240, e.g., the circumferential cavity 238 shown in FIGS. 3 and 4. In one or more embodiments, the circumferential cavity between the hammer casing 222 and the driver sub 240 may be a recess formed in the driver sub 240 that may be configured to receive the second split ring 250, as shown in FIGS. 19-22. In one or more embodiments, the first split ring 260 and the second split ring 250 disposed within the circumferential cavity between the hammer casing 222 and the driver sub 240 may prevent inadvertent back-off, unthreading, or any other type of inadvertent disengagement between the driver sub 240 and the hammer casing 222.

As shown in FIGS. 19-22, the first split ring 260 includes outer surface grooves 262 configured to engage with corresponding female grooves 226 of the hammer casing 222. The outer surface grooves 262 of the first split ring 260 and the female grooves 226 of the hammer casing 222 may have a corresponding set of flats on outer surface grooves 262 and female grooves 226, respectively. The outer surface grooves 262 of the first split ring 260 may also have ramps which correspond to ramps of the female grooves 226 of the hammer casing 222, similar to the ramps 294 of the hammer casing 222 and the ramps 284 of the first split ring 260 shown in FIG. 7. Those having ordinary skill in the art will appreciate that the first split ring 260 is not limited to including outer surface grooves 262 and, correspondingly, the hammer casing 222 is not limited to including corresponding female grooves 226, as will be discussed below with respect to FIGS. 23 and 24.

Further, as shown in FIGS. 19-22, the first split ring 260 includes inner surface grooves 264 formed on the opposite side (i.e., the inner side) of the first split ring 260 from the outer surface grooves 262. Furthermore, as shown in FIGS. 19-22, the second split ring 250 includes outer surface grooves 246 formed along at least a portion of a length of the second split ring 250. In one or more embodiments, the outer surface grooves 246 of the second split ring 250 may be configured to engage with the inner surface grooves 264 of the first split ring 260. The inner surface grooves 264 of the first split ring 260 may permit axial movement of the second split ring 250 relative to the first split ring 260 to occur in one direction, i.e., in the direction of the arrow 266. Further, the inner surface grooves 264 of the first split ring 260 may prevent axial movement of the second split ring 250 relative to the first split ring 260 in the direction of the arrow 268. The orientation of the ramp on the outer surface grooves 246 of the second split ring 250 with the corresponding ramps on the inner surface grooves 264 of the first split ring 260 may permit the diameter of the first split ring 260 to enlarge as one or more ramps of the inner surface grooves 264 of the first split ring 260 and one or more ramps of the outer surface grooves 246 of the second split ring 250 slide past each other. The contact interface of the above-described ramps, being in a non-perpendicular orientation relative to axial movement, may permit the relative motion between the first split ring 260 and the second split ring 250 to, in turn, provide sufficient radial force on the first split ring 260 to expand the diameter of the first split ring 260, thereby facilitating the movement of the second split ring 250 and the driver sub 240 in one direction relative to the first split ring 260.

When the second split ring 250 and/or the driver sub 240 is moving in the direction of arrow 268, i.e., axially downward, the flats 288, 298 of the outer surface grooves 262 of the first split ring 260 and the corresponding female grooves 226 of the hammer casing 222, respectively, are engaged such that the axial movement of the first split ring 260 relative to the driver sub 240 in the direction of arrow 266 is arrested. However, when the second split ring 250 and/or the driver sub 240 is moving in the direction of arrow 266, i.e., axially upward, the flats 288, 298 are engaged such that perpendicular movement relative to arrow 266 is permitted and ramps 246, 264 of the second split ring 250 and the first split ring 260, respectively, may climb past each other during assembly/stabbing of the driver sub 240 in the hammer casing 222.

Still referring to FIGS. 19-22, the hammer bit retainer system may be assembled such that the driver sub 240 is inserted/stabbed into the hammer casing 222 with both the first split ring 260 and the second split ring 250 disposed in the circumferential cavity, e.g., the circumferential cavity 238 shown in FIGS. 3 and 4, between an inner surface of the hammer casing 222 and an outer surface of the driver sub 240. In this steady state illustration, the ramp and the flat of the first split ring 260, e.g., the ramp 286 and the flat 282 of the split ring 260 shown in FIG. 7, constrict around and settle into mating contact with the ramp 276 and the flat 272 of the second split ring 250, similar to the ramp and the flat of the driver sub 240 shown in FIG. 7. In this steady state position shown in FIG. 7, the flat 298 and the ramp 294 on the female grooves 226 of hammer casing 222 may not be in engaging contact with corresponding/mating ramp 284 and flat 288 on outer surface grooves of the first split ring 260. In one or more embodiments, a slight amount of clearance may exist between these aforementioned corresponding surfaces. This steady state position is the service position when the hammer assembly 200 is in operational use and the anti-backoff feature of the hammer bit retainer system is not engaged.

As discussed above, when the assembly 200 is in operation, severe vibration and/or improper operational practices may create an undesirable condition in which the driver sub 240 begins to move in the direction of arrow 268, as shown in FIG. 19. This motion, in the direction of arrow 268, may be created when driver sub 240 begins to rotate and unthread itself from the hammer casing 222 at corresponding engaged threads (e.g., engaged threads 228, 248 shown in FIG. 3). If left unabated, the driver sub 240 may become separated from the hammer casing 222. However, when the hammer bit retainer system of the present disclosure is employed, the unabated movement of the driver sub 240 in the direction of arrow 268 may be prevented. As discussed above, in one or more embodiments, the hammer bit retainer system may include a multi-piece ring including the first split ring 260 and the second split ring 250.

Further, as discussed above, if the driver sub 240 begins to loosen from the hammer casing 222, the driver sub 240 moves axially in the direction of arrow 268 relative to the hammer casing 222. However, in this movement direction 268, the first split ring 260 is mechanically locked by the contact of the flats of the external circumferential grooves 246 of the second split ring 250 and the flats of the inner surface grooves 264 of the first split ring 260, such that both the second split ring 250 and the first split ring 260 move together as a single unit.

In one or more embodiments, each of the first split ring 260, the second split ring 250 and the driver sub 240 may move together as a single unit because the second split ring 250 may be disposed in a recess in the driver sub 240. Further, each of the first split ring 260, the second split ring 250 and the driver sub 240 may also move as a single unit because the grooves 246, 264 may prevent movement of the first split ring 260 with respect to the second split ring 250.

In one or more embodiments, if additional force is applied to the driver sub 240 and, in turn, the second split ring 250, in the direction of arrow 268, the ramps of the outer surface grooves 262 of the first split ring 260 and the ramps of the female grooves 226 of the hammer casing 222 engage further and may force the first split ring 260 to apply a hoop stress around the second split ring 250 and the driver sub 240. This may cause the mating contacting force of the flats of the inner surface grooves 264 of the first split ring 260 and the outer surface grooves 246 of the second split ring 250 to be increased. Due to the hoop stress created by the ramps of the outer surface grooves 262 of the first split ring 260 and the ramps of the female grooves 226 of the hammer casing 222 acting on the flats of the inner surface grooves 264 of the first split ring 260 and the outer surface grooves 246 of the second split ring 250, a mechanical lock may be generated between the driver sub 240, the second split ring 250, the first split ring 260, and the hammer casing 222, thereby halting any further axial movement of the driver sub 240 in the direction of arrow 268 relative to the hammer casing 222.

As discussed above with regard to FIG. 10, to remove the driver sub 240 from the hammer casing 222 (e.g., to service the hammer assembly 200), a spreading tool may be inserted into an access window, e.g., the access window 224 shown in FIG. 2, to expand the split ring 260 such that the flats 272, 282 are separated with a sufficient clearance to permit the driver sub 240 to move in the direction of arrow 268 without contacting the split ring 260.

In another embodiment, to remove the driver sub 240 from the hammer casing 222, torque may be applied to the driver sub 240, e.g., in a counter-clockwise direction, which may force the inner surface grooves 264 of the first split ring 260 to engage with the outer surface grooves 264 of the second split ring 250 and may force the first split ring 260 to tighten around the driver sub 240. Torque may be continually applied to the driver sub 240 until the inner surface grooves 264 of the first split ring 260 and the outer surface grooves 264 of the second split ring 250 fail in shear, which may allow the driver sub 240 to be extracted. Removing the driver sub 240 from the hammer casing 222 by torquing the driver sub 240 until the inner surface grooves 264 of the first split ring 260 and the outer surface grooves 264 of the second split ring 250 fail in shear may render a spreading tool and an access window superfluous. As such, those having ordinary skill in the art will appreciate that the hammer assembly 200, as described herein, is not limited to having an access window formed thereon (e.g., the access window 224 shown in FIG. 2). The lack of an access window formed on the hammer assembly 200 may allow the use of the multi-piece ring (i.e., the first split ring 260 and the second split ring 250) to be used as an anti-backoff mechanism between the driver sub 240 and the hammer casing 222 on a tool using mud circulation without concern of mud or other fluid leaking through the access window. Thus, fluid pressure inside the casing may also be maintained.

In one or more embodiments, the force used to shear the inner surface grooves 264 of the first split ring 260 and the outer surface grooves 264 of the second split ring 250 can be calculated/predetermined and may depend on the axial length of the grooves. The shear force may be related to the torque applied and/or the thread pitch on the female threads 226 of the hammer casing 222 and the outer surface grooves 246 of the second split ring 250. By varying the length of the inner surface grooves 264 of the first split ring 260 and the outer surface grooves 264 of the second split ring 250, the shear force and resulting torque can be predicted and designed to a specific value.

FIGS. 19-22 show the inner surface grooves 264 of the first split ring 260 covering about 100%, 75%, 50%, and 25%, respectively, of an axial length of the first split ring 260 (and/or an axial length of the outer surface grooves 262 of the first split ring 260). Similarly, FIGS. 19-22 show the outer surface grooves 246 of the second split ring 250 covering about 100%, 75%, 50%, and 25%, respectively, of an axial length of the second split ring 250.

As shown in FIG. 19, the length of the first split ring 260 covered by the outer surface grooves 262 is greater than about 90% (e.g., about 100%) of the length of the first split ring 260. Further, the length of the first split ring 260 covered by the inner surface grooves 264 is greater than about 90% (e.g., about 100%) of the length of the first split ring 260. As such, the length of the first split ring 260 covered by the inner surface grooves 264 is greater than about 90% (e.g., about 100%) of the length of the first split ring 260 covered by the outer surface grooves 262. In addition, the length of the second split ring 250 covered by the outer surface grooves 246 is greater than about 90% (e.g., about 100%) of the length of the second split ring 250.

As shown in FIG. 20, the length of the first split ring 260 covered by the outer surface grooves 262 is greater than about 90% (e.g., about 100%) of the length of the first split ring 260. Further, the length of the first split ring 260 covered by the inner surface grooves 264 is from about 60% to about 90% (e.g., about 75%) of the length of the first split ring 260. As such, the length of the first split ring 260 covered by the inner surface grooves 264 is from about 60% to about 90% (e.g., about 75%) of the length of the first split ring 260 covered by the outer surface grooves 262. In addition, the length of the second split ring 250 covered by the outer surface grooves 246 is from about 60% to about 90% (e.g., about 75%) of the length of the second split ring 250. The force used to shear the grooves 264 of the first split ring 260 and/or the grooves 246 of the second split ring 250, as shown in FIG. 20, may be less than the force used to shear the grooves 264 and/or the grooves 246, as shown in FIG. 19.

As shown in FIG. 21, the length of the first split ring 260 covered by the outer surface grooves 262 is greater than about 90% (e.g., about 100%) of the length of the first split ring 260. Further, the length of the first split ring 260 covered by the inner surface grooves 264 is from about 35% to about 65% (e.g., about 50%) of the length of the first split ring 260. As such, the length of the first split ring 260 covered by the inner surface grooves 264 is from about 35% to about 65% (e.g., about 50%) of the length of the first split ring 260 covered by the outer surface grooves 262. In addition, the length of the second split ring 250 covered by the outer surface grooves 246 is from about 35% to about 65% (e.g., about 50%) of the length of the second split ring 250. The force used to shear the grooves 264 of the first split ring 260 and/or the grooves 246 of the second split ring 250, as shown in FIG. 21, may be less than the force used to shear the grooves 264 and/or the grooves 246, as shown in FIGS. 19 and 20.

As shown in FIG. 22, the length of the first split ring 260 covered by the outer surface grooves 262 is greater than about 90% (e.g., about 100%) of the length of the first split ring 260. Further, the length of the first split ring 260 covered by the inner surface grooves 264 is from about 10% to about 40% (e.g., about 25%) of the length of the first split ring 260. As such, the length of the first split ring 260 covered by the inner surface grooves 264 is from about 10% to about 40% (e.g., about 25%) of the length of the first split ring 260 covered by the outer surface grooves 262. In addition, the length of the second split ring 250 covered by the outer surface grooves 246 is from about 10% to about 40% (e.g., about 25%) of the length of the second split ring 250. The force used to shear the grooves 264 of the first split ring 260 and/or the grooves 246 of the second split ring 250, as shown in FIG. 22, may be less than the force used to shear the grooves 264 and/or the grooves 246, as shown in FIGS. 19-21.

As may be appreciated, the axial length of the first split ring 260 covered by the inner surface grooves 264 may be between about 1% and about 25%, between about 25% and about 50%, between about 50% and about 75%, or between about 75% and about 100% of the axial length of the first split ring 260. As such, the length of the first split ring 260 covered by the inner surface grooves 264 may be between about 1% and about 25%, between about 25% and about 50%, between about 50% and about 75%, or between about 75% and about 100% of the length of the first split ring 260 covered by the outer surface grooves 262. In at least one embodiment, the axial length of the second split ring 250 covered by the outer surface grooves 246 may be between about 1% and about 25%, between about 25% and about 50%, between about 50% and about 75%, or between about 75% and about 100% of the axial length of the second split ring 250. In at least one embodiment, the axial length of the second split ring 250 covered by the outer surface grooves 246 may be between about 1% and about 25%, between about 25% and about 50%, between about 50% and about 75%, or between about 75% and about 100% of the length of the first split ring 260 covered by the outer surface grooves 262.

Those having ordinary skill will appreciate that embodiments disclosed herein are not limited to the outer surface grooves 262 of the first split ring 260 forming the entire length of the first split ring 260. For example, although not shown, in one or more embodiments, the outer surface grooves 262 of the first split ring 260 may extend about 50% of the length of the first split ring 260. Further, in one or more embodiments, the length of the first split ring 260 covered by the inner surface grooves 264 may be about 25% of the entire length of the first split ring 260. Although, in this embodiment, the length of the first split ring 260 covered by the inner surface grooves 264 may be about 25% of the entire length of the first split ring 260, it may be appreciated that the length of the first split ring 260 covered by the inner surface grooves 264 is about 50% of the length of the first split ring 260 covered by the outer surface grooves 262 because the length of the first split ring 260 covered by the outer surface grooves 262 is about 50% of the length of the first split ring 260.

Those having ordinary skill in the art will appreciate that, according to embodiments disclosed herein, the ratio of the length of the first split ring 260 covered by the inner surface grooves 264 to the length of the first split ring 260 covered by the outer surface grooves 262 may vary. For example, according to one or more embodiments, a ratio of the length of the first split ring 260 covered by the inner surface grooves 264 to the length of the first split ring 260 covered by the outer surface grooves 262 may be between about 0.01:1 and about 0.25:1, between about 0.25:1 and about 0.5:1, between about 0.5:1 and about 0.75:1, or between about 0.75:1 and about 1:1.

By controlling the length of the first split ring 260 covered by the inner surface grooves 264 relative to the length of the first split ring 260 covered by the outer surface grooves 262, the shear force used to shear the grooves 264, 246 of the first split ring 260 and the second split ring 250, respectively, may be predicted and designed to a specific value because the thread pitch on the hammer casing 222 and the second split ring 250 may be related to the torque applied. In other words, if a designer desires a break-out torque that is 150% greater than the makeup torque, the designer may calculate the axial length of the engaged grooves 264, 246 of the first split ring 260 and the second split ring 250, respectively, to supply the desired torque. As such, both the first split ring 260 and the second split ring 250 may be expendable components that may be replaced after each disassembly of the driver sub 240 from the hammer casing 222.

Further, in one or more embodiments, the force used to shear the grooves 264, 246 may be predicted and designed by varying the pitch and the height of each of the grooves 264, 246 of the first split ring 260 and the second split ring 250, respectively, as opposed to varying the length of the first split ring 260 covered by the inner surface grooves 264 relative to the length of the first split ring 260 covered by the outer surface grooves 262.

As shown in FIG. 23, in other embodiments, the hammer bit assembly 200 includes a hammer bit retainer system including the first split ring 260 and may not be limited to being a multi-piece ring (e.g., may not be limited to including the second split ring 250). As shown, the first split ring 260 has inner surface grooves 264 formed thereon, and the driver sub 240 has outer surface grooves 246 formed thereon. The outer surface grooves 246 of the driver sub 240 are configured to engage the inner surface grooves 264 of the first split ring 260. Further, as shown, the first split ring 260 is not limited to having outer surface grooves formed thereon (e.g., the outer surface grooves 262 discussed above in FIGS. 19-22), and the hammer casing 222 is not limited to having corresponding female grooves (e.g., the female grooves 226 shown in FIGS. 19-22).

Furthermore, as shown in FIG. 23, the inner surface grooves 264 of the first split ring 260 are formed along an entire length of the first split ring 260. As such, although the first split ring 260 shown in FIG. 23 does not include outer surface grooves, the length of the first split ring 260 covered by the inner surface grooves 264 may be varied, such as to cover 100% of the length of the first split ring 260.

Referring to FIG. 24, the hammer bit assembly 200 includes an illustrative hammer bit retainer system having the first split ring 260 and the second split ring 250, according to embodiments disclosed herein. As shown, the first split ring 260 has inner surface grooves 264 formed thereon, and the second split ring 250 has outer surface grooves 246 formed thereon, in which the outer surface grooves 246 of the second split ring 250 are configured to engage the inner surface grooves 264 of the first split ring 260. Further, as shown, the first split ring 260 is not limited to having outer surface grooves formed thereon (e.g., the outer surface grooves 262 discussed above in FIGS. 19-22), and the hammer casing 222 is not limited to having corresponding female grooves (e.g., the female grooves 226 shown in FIGS. 19-22).

Further, as shown in FIG. 24, the inner surface grooves 264 of the first split ring 260 are formed along an entire length of the first split ring 260. As such, although the first split ring 260 shown in FIG. 23 does not include outer surface grooves, the length of the first split ring 260 covered by the inner surface grooves 264 may be varied, such as to cover 100% of the length of the first split ring 260.

Although the first split ring 260 shown in FIGS. 23 and 24 does not include outer surface grooves formed thereon (e.g., the outer surface grooves 262 discussed above in FIGS. 19-22), and the hammer casing 222 does not include corresponding female grooves (e.g., the female grooves 226 shown in FIGS. 19-22), the torque used to shear the grooves 246, 264 may still be predicted and designed, as described above, by considering the axial length of the grooves 246, 264, as well as the pitch and length of the grooves 246, 264. In one or more embodiments, the material used to form the first split ring 260 and/or the second split ring 250 may be considered in determining the shear force desired for the hammer bit retainer system.

In one or more embodiments, the first split ring 260 and/or the second split ring 250 may be manufactured from alloy steel. For example, steel may be alloyed with a variety of elements in total amounts of between 1.0% and 50% by weight to improve the mechanical properties (e.g., strength, toughness, hardness, wear resistance, hardenability) of the first split ring 260 and/or the second split ring 250. In one or more embodiments, the first split ring 260 and/or the second split ring 250 may be heat treated. Common alloys that may be used include, but are not limited to, manganese, nickel, chromium, molybdenum, vanadium, silicon and boron. Other alloys that may be used include, but are not limited to, aluminum, cobalt, copper, cerium, niobium, titanium, tungsten, tin and zirconium. In another embodiment, the split ring 260 may be manufactured from a non-alloy steel. In still other embodiments, the split ring 260 may be manufactured from other metallic materials. In one or more embodiments, the first split ring 260 and/or the second split ring 250 may be manufactured from non-metallic materials.

Methods of hammer bit assembly/disassembly that include the hammer bit retention system in accordance with one or more embodiments of the present disclosure are generally disclosed with reference to the embodiment shown in FIGS. 2-6; however, it should be understood that the method of hammer bit assembly/disassembly disclosed herein may also apply to other embodiments disclosed herein. The method includes installing or inserting the split ring 260 in the circumferential cavity 238 of the hammer casing 222. The split ring 260 may be circumferentially compressed slightly to reduce the circumference of the split ring 260 for insertion through the lower end portion 236 of the hammer casing 222 and into the circumferential cavity 238.

The split ring 260 is then expanded radially outward inside the circumferential cavity 238 as the driver sub 240 is stabbed into the end of the hammer casing 222. Such expansion permits a sufficient clearance between an outer diameter of the driver sub 240 and an inner diameter of the split ring 260. The external threads 248 of the driver sub 240 are threadably engaged with the internal threads 228 of the hammer casing 222 and tightened to a specified torque, as will be known to one of ordinary skill in the art. The split ring 260 is then collapsed to a non-expanded diameter such that the split ring 260 engages the outer surface 258 of the driver sub 240.

The split ring 260 may be radially expanded in a number of ways in accordance with one or more embodiments of the present disclosure. In certain embodiments, as previously disclosed, the driver sub 240 may be configured having a tapered outer profile. As the driver sub 240 is inserted into the hammer casing 222 and through the split ring 260 installed in the circumferential cavity 238, the tapered profile of the driver sub 240 radially expands the split ring 260 by forcing the split ring 260 to climb on the tapered profile as the driver sub 240 penetrates the hammer casing 222. The split ring 260 may continue to climb the tapered profile of the driver sub 240 until the split ring 260 is axially located at the proper location on the driver sub (i.e., below or past the external threaded portion 248).

In one or more other embodiments, commercially available tools (e.g., needle-tip pliers) may be used to manually radially expand the split ring 260 by applying opposing forces on the end portions of the split ring 260 as the driver sub 240 is stabbed into the hammer casing 222. For example, the end portions of the split ring 260 may be accessed through the access window 224 (FIG. 4) disposed in the hammer casing 222. The pliers may be used to engage the end portions of the split ring 260 (having a gap or split 270 therebetween), or in other embodiments, extensions 361 of the split ring 360 (FIG. 15), to radially expand the split ring 260 such that the diameter/circumference of the split ring 260 is sufficiently large to allow the driver sub 240 to pass therethrough.

Once installed, the split ring 260 may remain stationary (i.e., the split ring 260 is substantially prevented from rotating) when the downhole tool is in operation so that the end portions of the split ring 260 remain aligned with the access window 224, thus allowing for disassembly. To prevent the split ring 260 from rotating, a lug 290 may be disposed in the split 270 of the split ring 260 as a stopper to prevent rotation of the split ring 260. The lug 290 may be installed after the split ring 260 is installed in the hammer casing 222. The lug 290 is disposed in the split 270 such that the middle section 292 of the lug 290 is aligned with the access window 224 of the hammer casing 222. The lug 290 may also be press fitted in the access window 224. In one or more embodiments, the access window 224, after the lug 290 is installed, may be sealed using a silica gel or sealing material to prevent particles from entering the central bore 230 of the hammer casing 222 through the access window 224. The sealing material may be removed from the access window 224 prior to disassembly of the driver sub 240 from the hammer casing 222.

To disassemble the driver sub 240 from the hammer casing 222, the split ring 260 is again expanded to disengage the inner surface grooves 264 of the split ring 260 from the external circumferential grooves 246 on the outer surface 258 of driver sub 240. The split ring 260 may be radially expanded by engaging end portions of split ring 260 (or extensions 361 of the split ring 360). The split ring 260 may be expanded via the access window 224 from the outside of the hammer casing 222 by expanding the split ring 260 using pliers or other tools. Once the split ring 260 is radially expanded inside the circumferential cavity 238 of the hammer casing 222, the driver sub 240 may be freely rotated and unthreaded from the hammer casing 222, and subsequently removed from the hammer casing 222.

While embodiments described herein relate to a hammer bit locking mechanism used to prevent a driver sub from backing off a hammer casing, it will be appreciated that the locking mechanism disclosed in one or more embodiments herein may have utility in any number of other tool assemblies and applications which prevent or mitigate a first component from axially separating from a second component.

One or more embodiments of the present disclosure provide a locking mechanism for threaded connections of downhole percussion hammer bits that may be used in any conventional or state-of-the-art downhole tool. Particularly, embodiments disclosed herein prevent threaded members from backing off (e.g., while the tool is downhole) through the use of a locking mechanism disposed between the threaded members. Thus, the locking mechanism may have broad application and result in cost savings as well as reduced drilling time.

For example, a split ring is assembled at the threaded connection between the hammer casing and driver sub for preventing back-off due to vibrations. Locking the threaded connection with the split ring provides high thrust load capacity, which may translate into cost savings and improved mechanical properties of the threaded connection and components. The split ring further allows for movement in one direction, while preventing the downhole components from separating if the threaded connection becomes loose. The split ring may be applied and removed multiple times without damaging any parts. Finally, the split ring may be adaptable to most downhole tools using threaded component end portions.

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from “Hammer Bit Locking Mechanism.” Accordingly, all such modifications are intended to be included within the scope of this disclosure. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.

Claims

1. A hammer bit locking mechanism, comprising:

a driver sub adapted to receive and movably couple to a shank of a bit, the driver sub including a portion thereof having an outer surface with one or more grooves therein;

a hammer casing having a central bore and receiving the portion of the driver sub in the central bore; and

a locking device disposed between the hammer casing and the portion of the driver sub, the locking device including an inner surface with one or more grooves therein configured to engage the one or more grooves in the outer surface of the portion of the driver sub, the locking device arranged and designed to prevent axial movement of the driver sub relative to the hammer casing in at least one direction.

2. The hammer bit locking mechanism of claim 1, wherein the locking device is disposed in a circumferential cavity defining the central bore of the hammer casing.

3. The hammer bit locking mechanism of claim 2, wherein the locking device includes an outer surface thereof with one or more grooves therein configured to engage one or more corresponding grooves on an inner surface of the hammer casing.

4. The hammer bit locking mechanism of claim 1, wherein engagement between the one or more grooves of the inner surface of the locking device and the one or more grooves of the outer surface of the driver sub prevent the driver sub from moving axially in one direction.

5. The hammer bit locking mechanism of claim 1, wherein the hammer casing has an access window arranged and designed to permit access to the locking device.

6. The hammer bit locking mechanism of claim 5, further comprising a lug disposed in the access window and positioned between end portions of the locking device.

7. The hammer bit locking mechanism of claim 1, wherein the driver sub has a tapered outer profile along an axial length thereof, and wherein the tapered outer profile has an angle of between 5 degrees and 30 degrees relative to a central axis of the driver sub.

8. A method of preventing decoupling of coupled components of a percussion hammer bit, the method comprising:

inserting a locking device in a circumferential cavity positioned in a hammer casing;

expanding the locking device;

inserting at least a portion of a driver sub into a central bore of the hammer casing and through the expanded locking device; and

coupling the driver sub and the hammer casing such that one or more inner surface grooves of the locking device engage one or more outer surface grooves of the driver sub, thereby preventing axial movement between the driver sub and the hammer casing in at least one direction.

9. The method of claim 8, wherein the locking device has one or more outer surface grooves configured to engage one or more corresponding inner surface grooves on the hammer casing.

10. The method of claim 8, further comprising accessing the locking device through an access window in the hammer casing.

11. The method of claim 10, further comprising installing a lug in the access window of the hammer casing, the lug arranged and designed to prevent the locking device from rotating.

12. The method of claim 8, wherein expanding the locking device is facilitated by a tapered outer surface of the portion of the driver sub being inserted into the central bore of hammer casing and through the expanded locking device.

13. A locking mechanism of a downhole tool, comprising:

a first body adapted to receive and movably couple to a shank of a bit;

a second body having a central bore and receiving a portion of the first body in the central bore; and

a first split ring disposed between the second body and the portion of the first body, the first split ring including an inner surface with one or more grooves formed therein and an outer surface with one or more grooves formed thereon, the first split ring arranged and designed to prevent axial movement of the first body relative to the second body in at least one direction; and

a second split ring disposed radially within the first split ring, the second split ring including an outer surface with one or more grooves formed thereon, the one or more grooves of the second split ring configured to engage the one or more grooves in the inner surface of the first split ring.

14. The locking mechanism of claim 13, wherein an axial length of the first split ring covered by the grooves formed on the inner surface thereof is between about 75% and about 100% of the axial length of the first split ring, or wherein an axial length of the second split ring covered by the grooves formed on the outer surface thereof is between about 75% and about 100% of the axial length of the second split ring.

15. The locking mechanism of claim 13, wherein an axial length of the first split ring covered by the grooves formed on the inner surface thereof is between about 50% and about 75% of the axial length of the first split ring, or wherein an axial length of the second split ring covered by the grooves formed on the outer surface thereof is between about 50% and about 75% of the axial length of the second split ring.

16. The locking mechanism of claim 13, wherein an axial length of the first split ring covered by the grooves formed on the inner surface thereof is between about 25% and about 50% of the axial length of the first split ring, or wherein an axial length of the second split ring covered by the grooves formed on the outer surface thereof is between about 25% and about 50% of the axial length of the second split ring.

17. The locking mechanism of claim 13, wherein an axial length of the first split ring covered by the grooves formed on the inner surface thereof is between about 1% and about 25% of the axial length of the first split ring, or wherein an axial length of the second split ring covered by the grooves formed on the outer surface thereof is between about 1% and about 25% of the axial length of the second split ring.

18. The locking mechanism of claim 13, wherein the downhole tool comprises a hammer bit.

19. The locking mechanism of claim 13, wherein the first body comprises a driver sub.

20. The locking mechanism of claim 13, wherein the second body comprises a hammer casing.