Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF FORMING POCKETS FOR RECEIVING
DRILL BIT CUTTING ELEMENTS
PRIORITY CLAIM
This application claims the benefit of the filing date of United States Patent
Application Serial No. 11/717,905, filed March 13, 2007, for "EARTH-BORING
TOOLS HAVING POCKETS FOR RECEIVING CUTTING ELEMENTS THEREIN
AND METHODS OF FORMING SUCH POCKETS ANp EARTH-BORING
TOOLS."
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," maybe
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.
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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)
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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.,
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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.
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.
DISCLOSURE OF THE INVENTION
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.
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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;
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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;
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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 1NVENTION
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
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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 maybe
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.
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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
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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
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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
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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
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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 521ocated 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,
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additional filler materia184 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 materia184 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 materia184 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 materia184, and may be
applied to the bit
body 50 as described therein. Furthermore, in some embodiments, the filler
materia184
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
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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.
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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
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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.
