U.S. patent application number 11/717905 was filed with the patent office on 2008-09-18 for earth-boring tools having pockets for receiving cutting elements therein and methods of forming such pockets and earth-boring tools.
Invention is credited to James L. Duggan, Redd H. Smith, John H. Stevens.
Application Number | 20080223622 11/717905 |
Document ID | / |
Family ID | 39580041 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080223622 |
Kind Code |
A1 |
Duggan; James L. ; et
al. |
September 18, 2008 |
Earth-boring tools having pockets for receiving cutting elements
therein and methods of forming such pockets and earth-boring
tools
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.
Inventors: |
Duggan; James L.;
(Friendswood, TX) ; Stevens; John H.; (Spring,
TX) ; Smith; Redd H.; (The Woodlands, TX) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
39580041 |
Appl. No.: |
11/717905 |
Filed: |
March 13, 2007 |
Current U.S.
Class: |
175/432 |
Current CPC
Class: |
E21B 10/573 20130101;
E21B 10/55 20130101 |
Class at
Publication: |
175/432 |
International
Class: |
E21B 10/36 20060101
E21B010/36 |
Claims
1. A method of forming a cutting element pocket in an earth-boring
tool, the method comprising: machining a first recess in an
earth-boring tool and defining a lateral sidewall surface of a
cutting element pocket using a rotating cutter oriented at an angle
relative to a longitudinal axis of the cutting element pocket;
machining a second recess in the earth-boring tool and defining at
least a portion of an end surface of the cutting element pocket;
and forming the lateral sidewall surface and the end surface of the
cutting element pocket to enable a generally cylindrical cutting
element to simultaneously abut against an area of each of the
lateral sidewall surface and the end surface of the cutting element
pocket.
2. The method of claim 1, wherein using a rotating cutter comprises
using an endmill cutter.
3. The method of claim 2, wherein using an endmill cutter comprises
using a ballnose endmill cutter.
4. The method of claim 1, wherein machining a second recess further
comprises machining the second recess after machining the first
recess.
5. The method of claim 1, wherein machining a second recess further
comprises machining the second recess prior to machining the first
recess.
6. The method of claim 1, wherein machining a second recess further
comprises using the same rotating cutter used to machine the first
recess to machine the second recess.
7. The method of claim 6, wherein using the same rotating cutter
used to machine the first recess to machine the second recess
further comprises orienting the rotating cutter at an angle
relative to the longitudinal axis of the cutting element pocket
while machining the second recess.
8. The method of claim 1, wherein machining a second recess in the
drill bit comprises machining a groove in a surface of the drill
bit exposed within the first recess.
9. The method of claim 8, wherein machining a groove comprises
machining a groove, at least a portion of the groove having a
generally annular shape.
10. The method of claim 1, wherein machining a second recess in the
drill bit comprises machining a generally planar recess in the
drill bit oriented substantially transverse to the longitudinal
axis of the cutting element pocket.
11. The method of claim 10, wherein machining the first recess
further comprises causing the first recess to intersect the
generally planar recess.
12. The method of claim 1, wherein forming the lateral sidewall
surface and the end surface of the cutting element pocket 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 comprises causing at least a portion of
the second recess to extend in a generally radially outward
direction from the longitudinal axis of the cutting element pocket
beyond at least a portion of the lateral sidewall surface of the
cutting element pocket.
13. A method of forming an earth-boring tool, the method
comprising: forming a bit body; and forming at least one cutting
element pocket in the bit body, comprising: machining a first
recess in a surface of the bit body and defining a lateral sidewall
surface of a cutting element pocket using a rotating cutter
oriented at an angle relative to a longitudinal axis of the cutting
element pocket; machining a second recess in the bit body and
defining at least a portion of an end surface of the cutting
element pocket; and forming the lateral sidewall surface and the
end surface of the cutting element pocket to enable a generally
cylindrical cutting element to simultaneously abut against an area
of each of the lateral sidewall surface and the end surface of the
cutting element pocket.
14. The method of claim 13, wherein forming a bit body comprises:
providing a powder mixture; and pressing the powder mixture to form
a green bit body.
15. The method of claim 14, wherein at least one of machining a
first recess and machining a second recess comprises machining the
green bit body.
16. The method of claim 14, wherein forming a bit body further
comprises partially sintering the green bit body to form a brown
bit body.
17. The method of claim 16, wherein at least one of machining a
first recess and machining a second recess comprises machining the
brown bit body.
18. The method of claim 17, wherein forming a bit body further
comprising sintering the brown bit body to a desired final
density.
19. The method of claim 14, wherein forming a bit body further
comprises sintering the green bit body to a desired final
density.
20. The method of claim 19, wherein at least one of machining a
first recess and machining a second recess comprises machining the
bit body after sintering the green bit body to a desired final
density.
21. The method of claim 14, wherein forming a bit body comprises
forming a bit body comprising a particle-matrix composite
material.
22. The method of claim 13, wherein forming a bit body comprises
forming a bit body predominantly comprised of a metal or metal
alloy.
23. The method of claim 22, wherein forming a bit body comprises
forming a steel bit body.
24. The method of claim 13, wherein using a rotating cutter
comprises using an endmill cutter.
25. The method of claim 24, wherein using an endmill cutter
comprises using a ballnose endmill cutter.
26. The method of claim 13, wherein machining a second recess
further comprises machining the second recess after machining the
first recess.
27. The method of claim 13, wherein machining a second recess
further comprises machining the second recess prior to machining
the first recess.
28. The method of claim 13, wherein machining a second recess
further comprises using the same rotating cutter used to machine
the first recess to machine the second recess.
29. The method of claim 28, wherein using the same rotating cutter
used to machine the first recess to machine the second recess
further comprises orienting the rotating cutter at an angle
relative to the longitudinal axis of the cutting element pocket
while machining the second recess.
30. The method of claim 13, wherein machining a second recess in
the bit body comprises machining a groove in a surface of the bit
body exposed within the first recess.
31. The method of claim 30, wherein machining a groove comprises
machining a groove, at least a portion of the groove having a
generally annular shape.
32. The method of claim 13, wherein machining a second recess in
the bit body comprises machining a generally planar recess in the
bit body oriented substantially transverse to the longitudinal axis
of the cutting element pocket.
33. The method of claim 32, wherein machining the first recess
further comprises causing the first recess to intersect the
generally planar recess.
34. The method of claim 13, further comprising: securing a cutting
element within the at least one cutting element pocket; and filling
at least a portion of a void within at least one of the first
recess and the second recess around the cutting element with a
filler material.
35. The method of claim 34, wherein filling at least a portion of a
void within at least one of the first recess and the second recess
around the cutting element with a filler material comprises filling
the at least a portion of the void with at least one of a brazing
alloy, a soldering alloy, a welding alloy, and a hardfacing
material.
36. The method of claim 34, wherein filling at least a portion of a
void within at least one of the first recess and the second recess
around the cutting element with a filler material comprises filling
the at least a portion of the void with a preformed solid
structure.
37. The method of claim 36, wherein filling the at least a portion
of the void with a preformed solid structure comprises at least one
of brazing, welding, and flamespraying the preformed solid
structure to the bit body.
38. The method of claim 36, wherein filling the at least a portion
of the void with a preformed solid structure further comprises
forming the preformed solid structure to comprise a particle-matrix
composite material.
39. An earth-boring tool having a bit body comprising: a first
surface defining a lateral sidewall surface of a cutting element
pocket, at least a portion of the first surface having a generally
cylindrical shape centered about a longitudinal axis of the cutting
element pocket; a substantially planar second surface defining a
back end surface of the cutting element pocket; and at least one
additional surface defining a groove located between the first
surface and the second surface and extending into the bit body in a
generally radially outward direction from the longitudinal axis of
the cutting element pocket beyond the at least a portion of the
first surface.
40. The earth-boring tool of claim 39, wherein the bit body is
predominantly comprised of steel.
41. The earth-boring tool of claim 39, wherein the bit body is
predominantly comprised of a particle-matrix composite
material.
42. The earth-boring tool of claim 39, further comprising a cutting
element secured within the at least one cutting element pocket.
43. The earth-boring tool of claim 42, further comprising a filler
material disposed within at least a portion of the at least one
cutting element pocket around the cutting element.
44. The earth-boring tool of claim 43, wherein the filler material
comprises at least one of a brazing alloy, a soldering alloy, a
welding alloy, and a hardfacing material.
45. The earth-boring tool of claim 43, wherein the filler material
comprises a preformed solid structure.
46. The earth-boring tool of claim 45, wherein the preformed solid
structure is at least one of brazed, welded, and flamesprayed to
the bit body.
47. The earth-boring tool of claim 45, wherein the preformed solid
structure comprises a particle-matrix composite material.
48. A method of forming an earth-boring tool, the method
comprising: forming a bit body; and forming at least one cutting
element pocket in the bit body, comprising: forming a first surface
in the bit body defining a lateral sidewall surface of the at least
one cutting element pocket and causing at least a portion of the
first surface to have a generally cylindrical shape centered about
a longitudinal axis of the cutting element pocket; forming a
substantially planar second surface defining a back end surface of
the cutting element pocket; and forming at least one additional
surface defining a groove located between the first surface and the
second surface and causing the at least one additional surface to
extend into the bit body in a generally radially outward direction
from the longitudinal axis of the cutting element pocket beyond the
at least a portion of the first surface.
49. The method of claim 48, wherein at least one of forming a first
surface, forming a substantially planar second surface, and forming
at least one additional surface comprises machining a recess in the
bit body using a rotating cutter oriented at an angle relative to
the longitudinal axis of the at least one cutting element
pocket.
50. The method of claim 49, wherein forming a first surface
comprises machining a recess in the bit body using the rotating
cutter oriented at an angle relative to the longitudinal axis of
the at least one cutting element pocket.
51. The method of claim 49, wherein using a rotating cutter
comprises using an endmill cutter.
52. The method of claim 51, wherein using an endmill cutter
comprises using a ballnose endmill cutter.
53. The method of claim 48, wherein forming a substantially planar
second surface further comprises forming the substantially planar
second surface after forming the first surface in the bit body.
Description
FIELD OF THE INVENTION
[0001] 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 OF THE INVENTION
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] As a result of such tool path interference problems, it
maybe 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.
[0011] Methods for overcoming such tool path interference problems
have been presented in the art. For example, U.S. Pat. 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.
[0012] However, there is a continuing need in the art for methods
of forming cutting element pockets on earth-boring rotary drill
bits that avoid the tool path interference problems discussed above
and that do not require use of additional support elements.
BRIEF SUMMARY OF THE INVENTION
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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 SEVERAL VIEWS OF THE DRAWINGS
[0017] 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:
[0018] FIG. 1 is a perspective view of an earth-boring rotary drill
bit;
[0019] 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
[0020] 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;
[0021] 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;
[0022] 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;
[0023] 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;
[0024] 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;
[0025] 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;
[0026] 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;
[0027] 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;
[0028] 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;
[0029] 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;
[0030] 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;
[0031] FIG. 11 is a side view of an embodiment of a cutting
element;
[0032] FIG. 12 is a side view of an embodiment of a cutting element
of the present invention;
[0033] 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;
[0034] 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
[0035] 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.
DETAILED DESCRIPTION OF THE INVENTION
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.degree.)) or an acute angle (i.e., between zero
degrees (0.degree.)) and ninety degrees (90.degree.)) 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.degree.))) or an acute angle
(i.e., between zero degrees (0.degree.)) and ninety degrees
(90.degree.)) 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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 maybe 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 maybe 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.
[0047] 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 maybe 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.
[0048] As previously mentioned, the additional recess or groove 70
maybe 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.degree.) 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.degree.)) and about thirty degrees (30.degree.))
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.
[0049] As previously described, in some embodiments of the present
invention, the recess 52 maybe formed prior to the recess or groove
70, and the recess or groove 70 maybe 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.
[0050] 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.
[0051] As shown in FIG.8, a recess 52' then maybe 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.
[0052] 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.
[0053] 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.
[0054] 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 U.S.
patent application Ser. No. 11/271,153, filed Nov. 10, 2005 and
pending U.S. patent application Ser. No. 11/272,439, also filed
Nov. 10, 2005, the disclosure of each of which application is
incorporated herein in its entirety by this reference.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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
U.S. patent application Ser. No. 11/513,677, filed Aug. 30, 2006,
the disclosure of which is incorporated herein in its entirety by
this reference, 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.
[0062] 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.
[0063] Such a preformed solid structure maybe 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 maybe 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 maybe secured to a cutting element 18 prior to
securing the cutting element 18 within the cutting element pocket
80.
[0064] 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.
[0065] 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 maybe 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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).
[0071] 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.
* * * * *