EP2129860B1

EP2129860B1 - Method of forming pockets for receiving drill bit cutting elements

Info

Publication number: EP2129860B1
Application number: EP08726771A
Authority: EP
Inventors: James L. Duggan; John H. Stevens; Redd H. Smith
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 2007-03-13
Filing date: 2008-03-12
Publication date: 2011-10-26
Anticipated expiration: 2028-03-12
Also published as: CA2679749A1; US20080223622A1; CN101631928A; EP2129860A1; WO2008112262A1; WO2008112262B1; ATE530732T1; PL2129860T3; RU2009137615A

Abstract

Methods of forming cutting element pockets in earth-boring tools include machining at least one recess to define at least one surface of a cutting element pocket using a cutter oriented at an angle to a longitudinal axis of the cutting element pocket. Methods of forming earth-boring tools include forming a bit body and forming at least one cutting element pocket therein using a rotating cutter oriented at an angle relative to a longitudinal axis of the cutting element pocket being formed. Earth-boring tools have a bit body comprising a first surface defining a lateral sidewall of a cutting element pocket, a second surface defining an end wall of the cutting element pocket, and another surface defining a groove located between the first and second surfaces that extends into the body to enable a cutting element to abut against an area of the lateral sidewall and end wall of the pocket.

Description

TECHNICAL FIELD

The present invention relates generally to earth-boring tools and methods of forming earth-boring tools. More particularly, the present invention relates to methods of securing cutting elements to earth-boring tools and to tools formed using such methods.

BACKGROUND

Rotary drill bits are commonly used for drilling bore holes or wells in earth formations. One type of rotary drill bit is the fixed-cutter bit (often referred to as a "drag" bit), which typically includes a plurality of cutting elements secured to a face region of a bit body. Generally, the cutting elements of a fixed-cutter type drill bit have either a disk shape or, in some instances, a more elongated, substantially cylindrical shape. A cutting surface comprising a hard, super-abrasive material, such as mutually bound particles of polycrystalline diamond forming a so-called "diamond table," may be provided on a substantially circular end surface of a substrate of each cutting element. Such cutting elements are often referred to as "polycrystalline diamond compact" (PDC) cutting elements or cutters. Typically, the PDC cutting elements are fabricated separately from the bit body and secured within pockets formed in the outer surface of the bit body. A bonding material such as an adhesive or, more typically, a braze alloy may be used to secured the cutting elements to the bit body.
The bit body of a rotary drill bit typically is secured to a hardened steel shank having an American Petroleum Institute (API) thread connection for attaching the drill bit to a drill string. The drill string includes tubular pipe and equipment segments coupled end to end between the drill bit and other drilling equipment at the surface. Equipment such as a rotary table or top drive may be used for rotating the drill string and the drill bit within the bore hole. Alternatively, the shank of the drill bit may be coupled directly to the drive shaft of a down-hole motor, which then may be used to rotate the drill bit.
Referring to FIG. 1, a conventional fixed-cutter earth-boring rotary drill bit 10 includes a bit body 12 that has generally radially-projecting and longitudinally-extending wings or blades 14, which are separated by junk slots 16 extending from channels on the face 20 of the bit body 12. A plurality of PDC cutting elements 18 are provided on the blades 14 extending over face 20 of the bit body 12. The face 20 of the bit body 12 includes the surfaces of the blades 14 that are configured to engage the formation being drilled, as well as the exterior surfaces of the bit body 12 within the channels and junk slots 16. The plurality of PDC cutting elements 18 may be provided along each of the blades 14 within cutting element pockets 22 formed in rotationally leading edges thereof, and the PDC cutting elements 18 may be supported from behind by buttresses 24, which may be integrally formed with the bit body 12.
The drill bit 10 may further include an API threaded connection portion 30 for attaching the drill bit 10 to a drill string (not shown). Furthermore, a longitudinal bore (not shown) extends longitudinally through at least a portion of the bit body 12, and internal fluid passageways (not shown) provide fluid communication between the longitudinal bore and nozzles 32 provided at the face 20 of the bit body 12 and opening onto the channels leading to junk slots 16.
During drilling operations, the drill bit 10 is positioned at the bottom of a well bore hole and rotated while drilling fluid is pumped through the longitudinal bore, the internal fluid passageways, and the nozzles 32 to the face 20 of the bit body 12. As the drill bit 10 is rotated, the PDC cutting elements 18 scrape across and shear away the underlying earth formation. The formation cuttings mix with and are suspended within the drilling fluid and pass through the junk slots 16 and up through an annular space between the wall of the bore hole and the outer surface of the drill string to the surface of the earth formation.
The bit body 12 of a fixed-cutter rotary drill bit 10 may be formed from steel. Such steel bit bodies are typically fabricated by machining a steel blank (using conventional machining processes including, for example, turning, milling, and drilling) to form the blades 14, junk slots 16, pockets 22, buttresses 24, internal longitudinal bore and fluid passageways (not shown), and other features of the drill bit 10.
The cutting elements 18 of an earth-boring rotary drill bit often have a generally cylindrical shape. Therefore, to form a pocket 22 for receiving such a cutting element 18 therein, it may be necessary or desirable to form a recess into the body of a drill bit that having the shape of a flat-ended, right cylinder. Such a recess may be machined into the body of a drill bit by, for example, using a drilling or milling machine to plunge a rotating flat-bottomed endmill cutter into the body of a drill bit along the axis of rotation of the cutter. Such a machining operation may yield a cutting element pocket 22 having a substantially cylindrical surface and a substantially planar end surface for disposing and brazing a generally cylindrical cutting element 18 therein.
In some situations, however, difficulties may arise in machining such generally cylindrical cutting element pockets 22. For instance, there may be physical interference between the machining equipment used, such as a multiple-axis milling machine, and the blades of the drill bit adjacent to the blade on which it is desired to machine a cutting element pocket 22. More specifically, the interference may inhibit a desired machining path of a machining tool that is aligned generally along the axis of rotation thereof because at least one of the machining tool and the collet or chuck that retains the machining tool may contact an adjacent blade. As a result, in order to form the desired cutting element pocket 22 by way of a flat-bottomed machining tool, such as an endmill, the machining tool may be required to remove a portion of, for example, a rotationally leading adjacent blade. As a further complication, drill bits often have a radially central "cone" region on the face thereof. In such a cone region, the profile of the face of the drill bit tapers longitudinally away from the direction of drilling precession as the profile approaches the center of the face of the drill bit. Thus, near the center of the bit, use of a flat-bottomed machining tool to form recesses for generally cylindrical cutting elements may be extremely difficult.
As a result of such tool path interference problems, it may be necessary to orient one or more cutting element pockets 22 on the face of an earth-boring rotary drill bit at an angle that causes the cutting element 18 secured therein to exhibit a backrake angle that is greater than a desired backrake angle.
Methods for overcoming such tool path interference problems have been presented in the art. For example, United States Patent No. 7,070,011 to Sherwood, Jr., et al . discloses steel body rotary drill bits having primary cutting elements that are disposed in cutter pocket recesses that are partially defined by cutter support elements. The support elements are affixed to the steel body during fabrication of the drill bits. At least a portion of the body of each cutting element is secured to a surface of the steel bit body, and at least another portion of the body of each cutting element matingly engages a surface of one of the support elements.
US 5 333 699 A is considered the closest prior art and discloses several methods of forming a cutting element pocket. In one of these methods a first slot is milled into and parallel to the top surface having a length which is slightly shorter than the length of the cutting structure and having a width slightly smaller than the diameter of the cylindrical portion of the cutting structure. After the slot is milled into the surface, a reduced shank diameter ball nosed end mill is used to mill a pocket into the leading face. The shank is reduced in diameter and is sized such as to pass through the slot in milling the pocket. The end result is a pocket which conforms to the shape of the cutting structure.
In the method of US 5 333 699 A the surfaces of the pocket, including the lateral sidewall surface and the back end surface are formed entirely by the second machining step using the ball nosed end mill. The first machining process, in which the slot is formed, does not form or define any of the final surfaces of the pocket (the surfaces that will be abutted by the cutting structure). In other words, all surfaces of the pocket are defined when the pocket is machined using the reduced shank diameter ball nosed end mill.
US 5 333 699 A further discloses several cutting element pockets that may be included within bit bodies of earth-boring tools. One cutting element pocket has a generally cylindrical surface centered about the longitudinal axis of the pocket and a hemi-spherical or semi-spherical back end. Furthermore, the generally cylindrical surface of the pocket directly meets and is continuous with the semi-spherical back end surface of the pocket.
It is the object of the invention to provide a method for forming at least one cutting element pocket in an earth-boring tool that avoids tool path interference problems and does not require use of additional support elements.
This object is achieved by a method comprising the features of claim 1. Preferred ways to carry out the method of the present invention are claimed in claims 2 to 7. A corresponding earth boring tool is claimed in claim 8. Preferred embodiments of the earth-boring tool of the present invention are claimed in claims 9 to 15.
In some embodiments, the present invention includes methods of forming one or more cutting element pockets in a surface of an earth-boring tool such as, for example, a fixed cutter rotary drill bit, a roller cone rotary drill bit, a core bit, an eccentric bit, a bicenter bit, a reamer, or a mill. The methods include using a rotating cutter to machine at least a portion of a cutting element pocket in such a way as to avoid mechanical tool interference problems and forming the pocket so as to sufficiently support a cutting element therein. For example, methods of the present invention may include machining at least a portion of a cutting element pocket using a rotating cutter oriented at an angle to a longitudinal axis of the cutting element pocket to be formed. In some embodiments, a first recess may be machined in a bit body of an earth-boring tool to define a lateral sidewall surface of a cutting element pocket using a rotating cutter oriented at an angle relative to the longitudinal axis of the cutting element pocket being formed. An additional recess may be machined in the bit body to define at least a portion of an end surface of the cutting element pocket. As cutting elements are often generally cylindrical in shape, the lateral sidewall surface and the end surface of the cutting element pocket may be formed so as to enable a generally cylindrical cutting element to simultaneously abut against each of the lateral sidewall surface and the end surface of the cutting element pocket.
In additional embodiments, the methods may include forming a first surface in a bit body that defines a lateral sidewall surface of a cutting element pocket. At least a portion of the first surface may be caused to have a generally cylindrical shape centered about a longitudinal axis of the cutting element pocket. A substantially planar second surface may be formed that defines a back end surface of the cutting element pocket. Further, at least one additional surface may be formed that defines a groove located between the first surface and the second surface. The at least one additional surface may be caused to extend into the bit body in a generally radially outward direction from the longitudinal axis of the cutting element pocket radially beyond the at least a portion of the first surface.
In additional embodiments, the present invention includes methods of forming an earth-boring tool such as, for example, any of those mentioned above. The methods include forming a bit body and using a rotating cutter to machine at least a portion of a cutting element pocket in the bit body in a manner that avoids mechanical tool interference problems and allows the pocket to be formed so as to sufficiently support a cutting element therein, as previously mentioned and described in further detail below.
In yet additional embodiments, the present invention includes earth-boring tools having a bit body comprising a first surface defining a lateral sidewall surface of a cutting element pocket, a second surface defining an end surface of the cutting element pocket, and at least one additional surface defining a groove located between the first and second surfaces that extends into the bit body in such a way as to enable a cutting element to abut against an area of each of the lateral sidewall surface and the end surface of the cutting element pocket. In some embodiments, the cutting element pockets may be configured to receive a generally cylindrical cutting element therein. For example, in some embodiments, at least a portion of the first surface that defines a lateral sidewall surface of the cutting element pocket may be generally cylindrical in shape and may be centered about a longitudinal axis of the cutting element pocket. In such embodiments, the at least one additional surface may define a groove that extends into the bit body in a generally radially outward direction from the longitudinal axis of the cutting element pocket radially beyond the generally cylindrical portion of the first surface.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, various features and advantages of this invention may be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an earth-boring rotary drill bit;
FIG. 2A is a partial cross-sectional view of a bit body of an earth-boring rotary drill bit like that shown in FIG. 1 and illustrates a portion of a cutting element pocket being formed in the bit body in accordance with one embodiment of the present invention; and
FIG. 2B is a partial cross-sectional view taken transversely through the partially formed cutting element pocket shown in FIG. 2A along section line 2B-2B shown therein;
FIG. 3 is a partial cross-sectional view like that of FIG. 2A illustrating a cutting element disposed within the partially formed cutting element pocket;
FIG. 4A is a partial cross-sectional view similar to that of FIG. 2A and illustrates another portion of the cutting element pocket being formed in the bit body shown therein;
FIG. 4B is a partial cross-sectional view taken transversely through the cutting element pocket shown in FIG. 4A along section line 4B-4B shown therein;
FIG. 5 is a partial cross-sectional view similar to that of FIG. 4A illustrating a cutting element disposed within the cutting element pocket and abutting against an area of both a lateral side wall and an end wall of the cutting element pocket;
FIG. 6 is a partial cross-sectional view of a bit body and illustrates a portion of a cutting element pocket being formed in a bit body in accordance with another embodiment of the present invention;
FIG. 7 is a partial cross-sectional view of a bit body and illustrates a portion of a cutting element pocket being formed in a bit body in accordance with yet another embodiment of the present invention;
FIG. 8 is a partial cross-sectional view like that of FIG. 7 and illustrates another portion of the cutting element pocket being formed in the bit body shown therein;
FIG. 9A is a partial longitudinal cross-sectional view like that of FIG. 5 further illustrating filler material disposed within the cutting element pocket around the cutting element therein;
FIG. 9B is a partial cross-sectional view taken transversely through the structure shown in FIG. 9A along section line 9B-9B shown therein and illustrates additional filler material disposed within the cutting element pocket over the cutting element therein;
FIG. 10 is another partial transverse cross-sectional view similar to that of FIG. 9B illustrating filler material disposed substantially entirely over a portion of a cutting element within a cutting element pocket;
FIG. 11 is a side view of an embodiment of a cutting element;
FIG. 12 is a side view of an embodiment of a cutting element of the present invention;
FIG. 13A is a plan view of a face of an embodiment of an earth-boring rotary drill bit of the present invention having a plurality of cutting element pockets similar to that shown in FIGS. 4A and 4B;
FIG. 13B is an enlarged perspective view of two primary cutting elements of the drill bit shown in FIG. 13A each disposed within a cutting element pocket similar to that shown in FIGS. 4A and 4B; and
FIG. 13C is an enlarged perspective view of two backup cutting elements of the drill bit shown in FIG. 13A each disposed within a cutting element pocket similar to that shown in FIGS. 4A and 4B.

MODE(S) FOR CARRYING OUT THE INVENTION

The illustrations presented herein are, in some instances, not actual views of any particular cutting element insert, cutting element, or drill bit, but are merely idealized representations which are employed to describe the present invention. Additionally, elements common between figures may retain the same numerical designation.
In some embodiments, the present invention includes methods of forming cutting element pockets that avoid or overcome at least some of the interference problems associated with previously known methods of forming such pockets, as well as the resulting cutting element pockets that are formed using such methods.
FIG. 2A is a partial cross-sectional view of a bit body 50 and illustrates a first recess 52 being formed in a formation-engaging surface or face 54 of the bit body 50 to define at least one surface 55 of the bit body 50 within a cutting element pocket. The recess 52 may be formed in the bit body 50 using a machining process. By way of example and not limitation, the recess 52 may be formed using a rotating cutter 56 of a multi-axis milling machine (not shown). In some embodiments, the cutter 56 of the milling machine may comprise a so-called "endmill" cutter, and optionally, a so-called "ballnose" endmill cutter, which are often used when milling three dimensional surfaces. As used herein, the term "ballnose" endmill cutter means an endmill cutter having a curved or rounded (e.g., hemispherical) cutting profile on the end thereof. In some methods, the cutter 56 may have a radius that is significantly smaller than the smallest radius of curvature of the surface 55 to be formed therewith.
In some embodiments, the cutting element that is desired to be secured to the face 54 of the bit body 50 in the cutting element pocket may have a generally cylindrical body comprising a generally cylindrical lateral sidewall surface extending between two substantially planar end surfaces. Such configurations are commonly used for polycrystalline diamond compact (PDC) cutters. As a result, the cutting element pocket to be formed also may have a generally cylindrical shape that is complementary to the cutting element to be secured therein.
FIG. 2B is a cross-sectional view of the bit body 50 shown in FIG. 2A taken through the recess 52 along section line 2B-2B shown therein. As can be seen with combined reference to FIGS. 2A and 2B, the surface 55 of the bit body 50 within the recess 52 may comprise a lateral sidewall surface of the cutting element pocket to be formed, and at least a portion 58 (FIG. 2B) of the lateral sidewall surface 55 may have a generally cylindrical shape. The generally cylindrical portion 58 of the surface 55 may be centered about a longitudinal axis 60 (FIG. 2A) of the cutting element pocket. The longitudinal axis 60 of the cutting element pocket may be defined as an axis extending through the cutting element pocket that would be coincident with the longitudinal axis of a cutting element properly secured within the cutting element pocket.
As shown in FIG. 2B, the surface 55 has a three-dimensional contour or shape and may be machined by moving the cutter 56 in the directions indicated by the directional arrows shown in FIGS. 2A and 2B while the cutter 56 is oriented at a right angle (i.e., ninety degrees (90°)) or an acute angle (i.e., between zero degrees (0°) and ninety degrees (90°)) relative to the longitudinal axis 60 (FIG. 2A). The angle between the cutter 56 and the longitudinal axis 60 may be varied as necessary or desired while machining the recess 52 in the bit body 50. As the surface 55 of the bit body 50 may be machined using a cutter 56 oriented at a right angle (i.e., ninety degrees (90°)) or an acute angle (i.e., between zero degrees (0°) and ninety degrees (90°)) relative to the longitudinal axis 60 (FIG. 2A) (as opposed to being aligned with the longitudinal axis 60), the previously described mechanical interference problems associated with machining a recess in a bit body to form a cutting element pocket may be reduced or eliminated.
Referring again to FIG. 2A, as the surface 55 of the bit body 50 within the recess 52 is machined, a substantially planar front (rotationally forward) end surface 64 and a substantially planar back (rotationally trailing) end surface 66 of the bit body 50 also may be formed. A curved or so-called "radiused" surface 68 may extend between the lateral sidewall surface 55 and each of the end surfaces 64, 66, as also shown in FIG. 2A.
FIG. 3 is a longitudinal cross-sectional view like that of FIG. 2A and illustrates a cutting element 18 disposed within the recess 52. As can be appreciated with reference to FIG. 3, the curved or radiused surface 68 disposed between the lateral sidewall surface 55 and the substantially planar back end surface 66 prevents the generally cylindrical cutting element 18 from simultaneously abutting against any significant area of both the lateral sidewall surface 55 and the substantially planar back end surface 66 of the bit body 50. It may be desired to enable the cutting element 18 to simultaneously abut against an area of each of the lateral sidewall surface 55 and the substantially planar back end surface 66 to provide increased or maximum support and reinforcement to the cutting element 18 during drilling operations.
Referring to FIG. 4A, to enable the cutting element 18 to abut against an area (as opposed to merely a point or along a line of contact) of each of the lateral sidewall surface 55 and the substantially planar back end surface 66 of the bit body 50 within the cutting element pocket, an additional recess or groove 70 may be formed in the bit body 50 at or near the intersection between the substantially planar back end surface 66 and the lateral sidewall surface 55 within the recess 52 to remove the curved or radiused surface 68 therebetween and form an embodiment of a cutting element pocket 80 of the present invention. This process of removing or displacing the curved or radiused surface 68 between the substantially planar back end surface 66 and the lateral sidewall surface 55 within the recess 52 may be referred to as "undercutting" an end of the recess 52, and the additional recess or groove 70 may provide a so-called "undercut" or "relief" for a cutting element to be secured within the cutting element pocket 80.
FIG. 4B is a cross-sectional view of the bit body 50 shown in FIG. 4A taken through the additional recess or groove 70 along section line 4B-4B shown in FIG. 4A. As can be seen with combined reference to FIGS. 4A and 4B, the additional recess or groove 70 may be defined by one or more surfaces 72 of the bit body 50 that extend in a generally radially outward direction from the longitudinal axis 60 (FIG. 4A) of the cutting element pocket 80 radially beyond at least the generally cylindrical portion 58 of the lateral sidewall surface 55. In some embodiments, at least a portion of the additional recess or groove 70 may have a generally annular shape and may extend about the longitudinal axis 60 of the cutting element pocket 80 at or near the intersection between the substantially planar back end surface 66 and the lateral sidewall surface 55 within the recess 52.
The additional recess or groove 70 may be formed in the bit body 50 using a machining process substantially similar to that previously described with reference to the recess 52 shown in FIGS. 2A and 2B, and may be machined using a rotating cutter 56 oriented at an angle (i.e., a right angle or an acute angle) relative to the longitudinal axis 60 of the cutting element pocket 80. In some embodiments, the additional recess or groove 70 may be formed in the bit body 50 using the same rotating cutter 56 used to form the recess 52, and the groove 70 may be formed during the same machining process or sequence as the recess 52. For example, in some embodiments, the recess 52 and the groove 70 may be formed sequentially in a single machining process or sequence carried out by a milling machine. As another example, in some embodiments, the recess 52 and the groove 70 may be formed together generally simultaneously in a single machining process or sequence carried out by a milling machine. In yet other embodiments, the recess 52 and the groove 70 may be formed sequentially in different machining processes or sequences.
Referring to FIG. 5, by forming the additional recess or groove 70 to undercut the recess 52, the substantially planar back end surface 66 of the cutting element pocket 80 may be sized and configured to allow a lateral sidewall surface 26 and a substantially planar back end surface 28 of a cutting element 18 to simultaneously abut against each of the lateral sidewall surface 55 and the substantially planar back end surface 66 of the bit body 50, respectively, within the cutting element pocket 80. In other words, the contact areas of the substantially planar back end surface 66 of the cutting element pocket 80 may be increased by forming the additional recess or groove 70 to undercut the recess 52 such that the area of the back end surface 66 encompassed by a boundary defined by the projection of at least the portion 58 of the lateral sidewall surface 55 onto the back end surface 66 is substantially planar. In this configuration, a cutting element 50 can simultaneously abut against each of the lateral sidewall surface 55 and the substantially planar back end surface 66 within the cutting element pocket 80, as shown in FIG. 5.
As previously mentioned, the additional recess or groove 70 may be machined in the bit body 50 using a rotating cutter 56 oriented at a right angle relative to the longitudinal axis 60 of the cutting element pocket 80, as shown in FIG. 4A. In additional embodiments of the present invention, the additional recess or groove 70 may be machined in the bit body 50 using a rotating cutter 56 oriented at an acute angle of less than ninety degrees (90°) relative to the longitudinal axis 60 of the cutting element pocket 80, as shown in FIG. 6. As a non-limiting example, the cutter 56 may be oriented at an acute angle of between about ninety degrees (90°) and about thirty degrees (30°) relative to the longitudinal axis 60 of the cutting element pocket 80 when forming the additional recess or groove 70. In some such methods, both the lateral sidewall surface 55 and the substantially planar back end surface 66 within the cutting element pocket 80 may be undercut by the additional recess or groove 70, as also shown in FIG. 6.
As previously described, in some embodiments of the present invention, the recess 52 may be formed prior to the recess or groove 70, and the recess or groove 70 may be formed in or cause to intersect one or more surfaces of the bit body 50 that are exposed within the recess 52. In additional embodiments, the recess or groove 70 may be formed prior to forming the recess 52, and the recess 52 may be formed in or caused to intersect one or more surface of the bit body 50 that are exposed within the recess or groove 70.
Referring to FIG. 7, for example, a recess or groove 70' may be formed in the bit body 50 to form a substantially planar surface 66 of the bit body. In some embodiments, for example, the recess or groove 70' may be generally planar or disc-shaped, and may be oriented substantially transverse to the longitudinal axis 60. Such a generally planar recess or groove 70' may be partially defined by the substantially planar surface 66 of the bit body 50 exposed within the recess or groove 70', a second, opposing substantially planar surface 67 of the bit body 50 exposed within the recess or groove 70', and one or more surfaces 72 that extend between the first and second planar surfaces 66, 67 of the bit body 50 and are exposed within the recess or groove 70'. The recess or groove 70' may be machined in the bit body 50 in a manner substantially similar to that previously described in relation to the groove 70 and FIGS. 4A and 4B.
As shown in FIG. 8, a recess 52' then may be formed in the bit body 50 to define the lateral side wall surface 55 of the cutting element pocket 80. The recess 52' may be caused to intersect the second substantially planar surface 67' (FIG. 7) of the bit body 50 exposed within the recess or groove 70'. The recess 52' may be machined in the bit body 50 in a manner substantially similar to that previously described in relation to the recess 52 and FIGS. 2A and 2B.
After forming the recess or groove 70' and the recess 52', the first substantially planar surface 66 may define a substantially planar back end surface of the cutting element pocket 80, and the lateral side wall surface 55 may define a lateral side wall surface of the cutting element pocket 80.
Although the cutting element pocket 80 illustrated in FIGS. 4A, 4B, and 5 is configured to receive a generally cylindrical cutting element 18 therein, in additional embodiments, the cutting element pocket 80, including the recess 52 and the additional recess or groove 70, may be configured to receive cutting elements 18 having other shapes and configurations.
The present invention has utility in relation to earth-boring rotary drill bits having bit bodies substantially comprised of a metal or metal alloy such as steel. Recently, new methods of forming rotary drill bits having bit bodies comprising particle-matrix composite materials have been developed in an effort to improve the performance and durability of earth-boring rotary drill bits. Such methods are disclosed in pending United States Patent Application Serial No. 11/271,153, filed November 10, 2005 and pending United States Patent Application Serial No. 11/272,439, also filed November 10, 2005 .
In contrast to conventional infiltration methods (in which hard particles (e.g., tungsten carbide) are infiltrated by a molten liquid metal matrix material (e.g., a copper based alloy) within a refractory mold), these new methods generally involve pressing a powder mixture to form a green powder compact, and sintering the green powder compact to form a bit body. The green powder compact may be machined as necessary or desired prior to sintering using conventional machining techniques like those used to form steel bit bodies. Furthermore, additional machining processes may be performed after sintering the green powder compact to a partially sintered brown state, or after sintering the green powder compact to a desired final density. For example, it may be desired to machine cutting element pockets on one or more blades 14 (FIG. 1) of a bit body formed by such a process while the bit body is in the green, brown, or fully sintered state. However, as with steel-bodied drill bits, interference problems may prevent the formation of the desired cutting element pockets. To overcome such interference problems, methods of the present invention, such as those previously described herein, may be used to form one or more cutting element pockets 80 in one or more blades (such as the blades 14 shown in FIG. 1) of a bit body 50 formed by such a process while the bit body 50 is in the green, brown, or fully sintered state. Therefore, the present invention also has utility in relation to earth-boring tools having bit bodies substantially comprised of a particle-matrix composite material.
After forming one or more cutting element pockets 80 in a bit body 50 of an earth-boring rotary drill bit as previously described, a cutting element 18 may be positioned within each cutting element pocket 80 and secured to the bit body 50. By way of example and not limitation, each cutting element 18 may be secured within a cutting element pocket 80 using a brazing alloy, a soldering alloy, or an adhesive material.
As shown in FIG. 5, after securing each cutting element 18 within a cutting element pocket 80, one or more spaces or voids may be disposed within the cutting element pocket 80 around at least a portion of the cutting element 18. For example, the recess or groove 70 may comprise or define a space or void around the cutting element 18 within the cutting element pocket 80. Additionally, the portion of the recess 52 located in front of (rotationally forward relative to) the cutting element 18 may comprise or define another space or void around the cutting element 18 within the cutting element pocket 80. Such spaces or voids may facilitate wear of the surrounding elements or portions of the drill bit during a drilling operation, which could potentially result in separation of the cutting element 18 from the bit body 50 while drilling. The spaces or voids within the cutting element pocket 80 around the cutting element 18 may be filled with a filler material, as discussed in further detail below, to prevent wear during drilling operations.
Referring to FIG. 9A, the spaces or voids defined by the recess or groove 70 and the portion of the recess 52 located in front of the cutting element 18 may be filled with a filler material 84. FIG. 9B is a partial transverse cross-sectional view of the structure shown in FIG. 9A taken along section line 9B-9B shown therein. As shown in FIG. 9B, additional filler material 84 also may be disposed within the cutting element pocket 80 over at least a portion of the cutting element 18 to reduce or eliminate any recesses or voids extending into the cutting element pocket 80 below the face 54 of the bit body 50.
FIG. 10 is a partial transverse cross-sectional view taken through a cutting element pocket 80 and cutting element 18 positioned therein, similar to that of FIG. 9B. As shown in FIG. 10, in some situations, at least a portion of the cutting element 18 may be substantially entirely recessed within the cutting element pocket 80 below the face 54 of the bit body 50. In such cases, filler material 84 may be provided entirely over at least a portion of the cutting element 18 within the cutting element pocket 80.
By way of example and not limitation, the filler material 84 shown in FIGS. 9A, 9B, and 10 may comprise a welding alloy, a solder alloy, or a brazing alloy, and may be applied using a corresponding welding, soldering, or brazing process.
In additional embodiments, the filler material 84 may comprise a hardfacing material (e.g., a particle-matrix composite material) and may be applied using a welding process (e.g., arc welding processes, gas welding processes, resistance welding processes, etc.) or a flamespray process. By way of example and not limitation, any of the hardfacing materials described in pending United States Patent Application Serial No. 11/513,677, filed August 30, 2006 , may be used as the filler material 84, and may be applied to the bit body 50 as described therein. Furthermore, in some embodiments, the filler material 84 may comprise at least one of a welding alloy, a solder alloy, or a brazing alloy, and hardfacing material may be applied over the exposed surfaces thereof to minimize or prevent wear during drilling operations. Such layered combinations of materials may be selected to form a composite or graded structure between the cutting element 18 and the surrounding bit body 50 that is selected to tailor at least one of the strength, toughness, wear performance, and erosion performance of the region immediately surrounding the cutting element 18 for the particular design of the drilling tool, location of the cutting element 18 on the drilling tool, or the application in which the drilling tool is to be used.
In yet other embodiments, at least a portion of the filler material 84 may be or comprise a preformed solid structure that is constructed and formed to have a shape corresponding to that of at least a portion of a recess or void within the cutting element pocket 80 around the cutting element 18. As a non-limiting example, the filler material 84 shown in FIG. 10 over the cutting element 18 may comprise a preformed solid cap structure that may be positioned over the cutting element 18 within the cutting element pocket 80 and secured to the bit body 50.
Such a preformed solid structure may be separately fabricated, positioned at a location within the cutting element pocket 80 selected to fill a space or void, and secured to one or more surrounding surfaces of the bit body 50. The preformed solid structure may be secured to one or more surrounding surfaces of the bit body 50 using, for example, an adhesive, a brazing process, a flamespray process, or a welding process. In some embodiments, a preformed solid structure may be positioned within the cutting element pocket 80 and secured to the bit body 50 after securing a cutting element 18 in the cutting element pocket 80. In additional embodiments, such a preformed solid structure may be positioned within the cutting element pocket 80 and secured to the bit body 50 prior to securing a cutting element 18 in the cutting element pocket 80. In yet other embodiments, one or more such preformed solid structures may be secured to a cutting element 18 prior to securing the cutting element 18 within the cutting element pocket 80.
In some embodiments, such a preformed solid structure may comprise a relatively abrasive and wear-resistant material such as a particle-matrix composite material comprising a plurality of hard particles (e.g., tungsten carbide) dispersed throughout a metal or metal alloy matrix material (e.g., a nickel or cobalt based metal alloy), so as to further prevent wear of the material surrounding the cutting element 18 during drilling operations.
FIG. 11 is a side view of a cutting element 18. As shown in FIG. 11, in some embodiments, the cutting element 18 may comprise a diamond table 85 formed on or otherwise secured to a surface of a first substrate 86. An opposing surface of the first substrate 86 may be secured to a surface of a second, relatively larger substrate 87. The first substrate 86 may, in some embodiments, have a disc shape, and the relatively larger substrate 87 may have an elongated shape. For example, it may be desired to have a substrate having a shape similar to the composite shape formed by the first substrate 86 and the second substrate 87. It may be difficult, however, to form a diamond table 85 on a surface of such a substrate. As a result, it may be necessary or desired to form a diamond table on a relatively smaller substrate, such as the first substrate 86, and then secure the relatively smaller substrate to a relatively larger substrate, such as the second substrate 87 to provide a composite substrate having the desired shape.
FIG. 12 illustrates an embodiment of a cutting element 18A of the present invention. As shown in FIG. 12, the cutting element 18A comprises a relatively smaller first substrate 86A and a relatively larger substrate 87A. The cutting element 18A may have one or more features 88 integrally formed therewith that are sized, shaped, and otherwise configured to fill at least a portion of a recess or void within the cutting element pocket 80 around the cutting element 18. For example, one or more such features 88 may be integrally formed with at least one of the first substrate 86A and the second substrate 87A. By way of example and not limitation, cutting element 18A may have a feature 88 integrally formed with the second substrate 87A that has a size and shape configured to fill a recess 70 (such as that previously described with reference to FIG. 4A-4B), as shown in FIG. 12. In additional embodiments, the cutting element 18A may comprise one or more additional features 88 sized and configured to fill at least a portion of a recess or void located over the cutting element 18A within the cutting element pocket 80, such as those previously described with reference to FIGS. 9B and 10.
FIG. 13A is a plan view of the face of an embodiment of an earth-boring rotary drill bit 90 of the present invention. The earth-boring rotary drill bit 90 includes a bit body 92 having a plurality of generally radially-projecting and longitudinally-extending wings or blades 94, which are separated by junk slots 96 extending from channels on the face of the bit body 92. A plurality of primary PDC cutting elements 18 are provided on each of the blades 94 within cutting element pockets 80 (FIGS. 4A-4B). A plurality of secondary PDC cutting elements 18' are also provided within cutting element pockets 80 on each of the blades 94 rotationally behind the primary cutting elements 18.
FIG. 13B is an enlarged perspective view illustrating two primary cutting elements 18 that have been secured within cutting element pockets 80 formed using methods of the present invention, as previously described herein. Similarly, FIG. 13C is an enlarged perspective view illustrating two secondary cutting elements 18' that have also been secured within cutting element pockets 80 formed using methods of the present invention, as previously described herein.
While the present invention has been described herein in relation to embodiments of earth-boring rotary drill bits that include fixed cutters, other types of earth-boring tools such as, for example, core bits, eccentric bits, bicenter bits, reamers, mills, roller cone bits, and other such structures known in the art may embody teachings of the present invention and may be formed by methods that embody teachings of the present invention, and, as used herein, the term "bit body" encompasses bodies of earth-boring rotary drill bits, as well as bodies of other earth-boring tools including, but not limited to, core bits, eccentric bits, bicenter bits, reamers, mills, roller cone bits, as well as other drilling and downhole tools.
By using embodiments of cutting element pockets 80 of the present invention, cutters (primary cutters and backup cutters) may be secured to the face of a bit body at practically any location thereon, and the cutting element pockets 80 may be configured to provide any selected backrake angle to a cutting element secured therein, without encountering mechanical tool interference problems. As a result, earth-boring drilling tools, such as the earth-boring rotary drill bit 90 shown in FIG. 13A may be provided that are capable of drilling at increased rates of penetration relative to previously known drilling tools having machined cutter pockets, and similar to rates of penetration achieved using drilling tools having cutter pockets formed in a casting process (e.g., infiltration).
Furthermore, while the present invention has been described herein with respect to certain preferred embodiments, those of ordinary skill in the art will recognize and appreciate that it is not so limited. Rather, many additions, deletions and modifications to the preferred embodiments may be made without departing from the scope of the invention as hereinafter claimed. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the invention as contemplated by the inventors. Further, the invention has utility with different and various bit profiles as well as cutter types and configurations.

Claims

A method comprising forming at least one cutting element pocket (80) in an earth-boring tool (10, 90), the method comprising machining a first recess (52, 52') in an earth-boring tool (10, 90) and defining a lateral sidewall surface (55) of at least one cutting element pocket (80) using a rotating cutter (56) oriented at an angle relative to a longitudinal axis (60) of the at least one cutting element pocket (80), the method characterized by further comprising:
- machining a second recess (70, 70') in the earth-boring tool (10, 90) and defining at least a portion of a substantially planar back end surface (66) of the at least one cutting element pocket (80); and

- forming the lateral sidewall surface (55) and the back end surface (66) of the at least one cutting element pocket (80) to enable a generally cylindrical cutting element having a substantially planar back end surface (66) to simultaneously abut against an area of each of the lateral sidewall surface (55) and the back end surface (66) of the at least one cutting element pocket (80).
The method of claim 1, further comprising:
- forming a bit body (50); and

- forming the at least one cutting element pocket (80) in the bit body (50, 92).
The method of claim 2, wherein forming a bit body (50, 92) comprises:
- providing a powder mixture; and

- pressing the powder mixture to form a green bit body.
The method of claim 2, wherein forming a bit body comprises forming a bit body predominantly comprised of a metal or metal alloy.
The method of claim 2, wherein machining a second recess (70, 70') in the bit body comprises machining a groove (70, 70') in a surface of the bit body exposed within the first recess (52, 52').
The method of claim 1 or 2, further comprising:
- securing a cutting element (18, 18', 18A) within the at least one cutting element pocket (80); and

- filling at least a portion of a void within at least one of the first recess (52, 52') and the second recess (70, 70') around the cutting element (18, 18', 18A) with a filler material (84).
The method of claim 1 or 2, wherein forming the lateral sidewall surface (55) and the back end surface (66) of the at least one cutting element pocket (80) to enable a generally cylindrical cutting element to simultaneously abut against each of the lateral sidewall surface (55) and the back end surface (66) of the at least one cutting element pocket (80) comprises causing at least a portion of the second recess (70, 70') to extend in a generally radially outward direction from the longitudinal axis (60) of the at least one cutting element pocket (80) beyond at least a portion of the lateral sidewall surface (55) of the at least one cutting element pocket (80).
An earth-boring tool (10, 90) having a bit body (50, 92) comprising:
- a first surface (55) defining a lateral sidewall surface (55) of at least one cutting element pocket (80), at least a portion of the first surface (55) having a generally cylindrical shape centered about a longitudinal axis (60) of the at least one cutting element pocket (80); and

- a substantially planar second surface (66) defining a back end surface (66) of the at least one cutting element pocket (80);
the earth-boring tool (10, 90) characterized in that the bit body (50, 92) further comprises:
- at least one additional surface (72) defining a groove (70, 70') located between the first surface (55) and the second surface (66) and extending into the bit body in a generally radially outward direction from the longitudinal axis (60) of the at least one cutting element pocket (80) beyond the at least a portion of the first surface (55).
The earth-boring tool of claim 8, wherein the bit body is predominantly comprised of one of steel and a particle-matrix composite material.
The earth-boring tool of claim 8 or claim 9, further comprising a cutting element secured (18, 18', 18A) within the at least one cutting element pocket (80).
The earth-boring tool of claim 10, further comprising a filler material (84) disposed within at least a portion of the at least one cutting element pocket (80) around the cutting element (18, 18', 18A).
The earth-boring tool of claim 11, wherein the filler material (84) comprises at least one of a brazing alloy, a soldering alloy, a welding alloy, and a hardfacing material.
The earth-boring tool of claim 11, wherein the filler material (84) comprises a preformed solid structure.
The earth-boring tool of claim 13, wherein the preformed solid structure is at least one of brazed, welded, and flamesprayed to the bit body.
The earth-boring tool of claim 13 or claim 14, wherein the preformed solid structure comprises a particle-matrix composite material.