U.S. patent application number 12/425766 was filed with the patent office on 2009-10-22 for anti-tracking feature for rock bits.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Robert J. Buske, James L. Overstreet, Rudolf Carl Pessier.
Application Number | 20090260890 12/425766 |
Document ID | / |
Family ID | 41200182 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090260890 |
Kind Code |
A1 |
Buske; Robert J. ; et
al. |
October 22, 2009 |
ANTI-TRACKING FEATURE FOR ROCK BITS
Abstract
The harmful effects of tracking are reduced for a drill bit
having roller cones with at least one of the outermost rows of
active teeth containing one or more teeth having a height that does
not extend to the height of at least one of the outermost rows on
another roller cone on the bit. The crest on this tooth may have a
length in a circumferential direction that is wider than an overall
width of the tooth in the outer to inner direction. The invention
may be used on any cutter row, not just the outermost row. The
design may be used on a different roller cone or row, or more than
one cutter row. The anti-tracking feature may be located between
the leading and trailing edges of the tooth on one or more roller
cones.
Inventors: |
Buske; Robert J.; (The
Woodlands, TX) ; Overstreet; James L.; (Tomball,
TX) ; Pessier; Rudolf Carl; (Galveston, TX) |
Correspondence
Address: |
Bracewell & Giuliani LLP
P.O. Box 61389
Houston
TX
77208-1389
US
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
41200182 |
Appl. No.: |
12/425766 |
Filed: |
April 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61046508 |
Apr 21, 2008 |
|
|
|
Current U.S.
Class: |
175/374 ;
175/376 |
Current CPC
Class: |
E21B 10/16 20130101 |
Class at
Publication: |
175/374 ;
175/376 |
International
Class: |
E21B 10/16 20060101
E21B010/16; E21B 10/00 20060101 E21B010/00; E21B 10/08 20060101
E21B010/08; E21B 10/52 20060101 E21B010/52 |
Claims
1. A drill bit for reducing harmful effects of tracking,
comprising: a bit body having bit legs with bearing pins; a roller
cone mounted to each of the bearing pins to define a plurality of
roller cones, each roller cone having an axis and rows of active
teeth, each of the active teeth having a radial height, an outer
end and an inner end that define a length, a pair of flanks that
define a width and a crest at which the ends and flanks converge;
spaces between the active teeth that define a depth of cut for the
roller cones; and an anti-tracking element on at least one of the
rows of active teeth and having a second radial height that is less
than the radial height of the active teeth and extending into a
range of the depth of cut, such that the anti-tracking element
engages and removes formation that remains as a result of uncut
formation left behind by the active teeth.
2. A drill bit according to claim 1, wherein the anti-tracking
element is in an outermost row of one of the roller cones.
3. A drill bit according to claim 1, wherein the anti-tracking
element has a crest with a width extending in a circumferential
direction that is wider than the width of the active teeth.
4. A drill bit according to claim 3, wherein the crest has a length
in an axial direction that is less than an axial length of one of
the active teeth.
5. A drill bit according to claim 4, wherein the width of the crest
of the anti-tracking element in the circumferential direction is
greater than the length of the crest of the anti-tracking
element.
6. A drill bit according to claim 1, wherein the anti-tracking
element comprises a plurality of anti-tracking elements located on
more than one row of the plurality of roller cones.
7. A drill bit according to claim 1, wherein the anti-tracking
element comprises a heel row of a plurality of anti-tracking teeth
having a higher count than any other row on the plurality of roller
cones.
8. A drill bit according to claim 7, wherein the plurality of
anti-tracking teeth comprise tungsten carbide inserts.
9. A drill bit according to claim 7, wherein the heel row comprises
an integrally-formed anti-tracking element in a shape of disk
having a plurality of slots formed therein to define the plurality
of anti-tracking teeth, and the slots extend radially in a
symmetrical configuration.
10. A drill bit according to claim 7, wherein the plurality of
anti-tracking teeth have wear pads on outer surfaces thereof
opposite a next row of active teeth.
11. A drill bit according to claim 1, wherein the anti-tracking
element comprises a scallop extending between two adjacent active
teeth.
12. A drill bit according to claim 11, wherein the scallop tapers
radially with respect to the axis of the roller cone, and tapers in
width in a circumferential direction.
13. A drill bit according to claim 11, wherein the anti-tracking
element has a greater circumferential width than the active teeth,
and crests of the anti-tracking element maintain an active tooth
pitch on the row with other ones of the active teeth.
14. A drill bit according to claim 1, wherein the anti-tracking
element forms an integral portion of one of the active teeth and is
curved on a leading or trailing edge of said one of the active
teeth.
15. A drill bit according to claim 14, wherein the anti-tracking
element tapers radially with respect to the axis of the roller
cone, tapers in width in a circumferential direction, such that the
anti-tracking element has a greater circumferential width than the
active teeth, and the tapers converge in a crest that is formed at
multiple radii or non-uniform radii.
16. A drill bit for reducing harmful effects of tracking,
comprising: a bit body having bit legs with bearing pins; a roller
cone mounted to each of the bearing pins to define a plurality of
roller cones, each roller cone having an axis and rows of active
teeth, each of the active teeth having a radial height, an outer
end and an inner end that define a length, a pair of flanks that
define a width and a crest at which the ends and flanks converge;
spaces between the active teeth that define a depth of cut for the
roller cones; and a plurality of anti-tracking elements located on
more than one row of the plurality of roller cones, with at least
one of the anti-tracking elements located on an outermost row of
active teeth and having a second radial height that is less than
the radial height of the active teeth and extending into a range of
the depth of cut, such that the anti-tracking element engages and
removes formation that remains as a result of uncut formation left
behind by the active teeth.
17. A drill bit according to claim 16, wherein the anti-tracking
elements have crests with a width extending in a circumferential
direction that is wider than the width of the active teeth.
18. A drill bit according to claim 17, wherein the crest has a
length in an axial direction that is less than the length of the
active teeth, and the width of the crest of the anti-tracking
element in the circumferential direction is greater than the length
of the crest of the anti-tracking element.
19. A drill bit according to claim 16, wherein the anti-tracking
element comprises a heel row of a plurality of anti-tracking teeth
having a higher count than any other row on the plurality of roller
cones.
20. A drill bit according to claim 19, wherein the plurality of
anti-tracking teeth comprise tungsten carbide inserts.
21. A drill bit according to claim 19, wherein the heel row
comprises an integrally-formed anti-tracking element in a shape of
a disk having a plurality of slots formed therein to define the
plurality of anti-tracking teeth, the slots extend radially in a
symmetrical configuration, and the anti-tracking teeth have wear
pads on outer surfaces thereof opposite a next row of active
teeth.
22. A drill bit according to claim 16, wherein the anti-tracking
element comprises a scallop extending between two adjacent active
teeth.
23. A drill bit according to claim 22, wherein the scallop tapers
radially with respect to the axis of the roller cone, and tapers in
width in a circumferential direction.
24. A drill bit according to claim 23, wherein the anti-tracking
elements have greater circumferential widths than the active teeth,
and crests of the anti-tracking elements maintain an active tooth
pitch on the row with other ones of the active teeth.
25. A drill bit according to claim 16, wherein the anti-tracking
element forms an integral portion of one of the active teeth and is
curved on a leading or trailing edge of said one of the active
teeth, the anti-tracking element tapers radially with respect to
the axis of the roller cone, tapers in width in a circumferential
direction, such that the anti-tracking element has a greater
circumferential width than the active teeth, and the tapers
converge in a crest that is formed at multiple radii or non-uniform
radii.
Description
[0001] This application claims priority to U.S. Provisional Pat.
App. No. 61/046,508, filed on Apr. 21, 2008, and i s incorporated
herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates in general to drill bits and,
in particular, to an improved system, method, and apparatus for
reducing the harmful effects of tracking with drill bits.
[0004] 2. Description of the Related Art
[0005] A roller cone earth-boring drill bit has a number of cones,
typically three, each of which is rotatably mounted to a bearing
pin. Each cone rotates about its axis when the bit body rotates
around the bit axis. The cones have cutting elements, often in
rows, which may be teeth integrally formed in the cone metal, or
tungsten carbide inserts pressed into mating holes in the cone
metal.
[0006] Each cone has an outermost or heel row near a gage surface
of the cone and one or more inner rows. One or more of the cones
have cutting elements located near or on the nose of the cone. In
some cases the cutting elements in the adjacent row closest to the
heel row will be staggered or alternate with the cutting elements
in the heel row.
[0007] The inner rows of each cone are arranged at different
distances from the bit axis for cutting different portions of the
borehole bottom. Normally at least two of the cones have heel rows
that are located at substantially the same distance from the bit
axis. When all three cones are rotated into a single section plane,
the heel row cutting elements superimpose or overlap (at least
partially) on one another. The inner rows are normally spaced at
different distances from the bit axis and thus provide single row
coverage on the remaining portions of the borehole bottom. When the
cones are rotated about their axes, the rows of teeth make
indentations on the borehole bottom. When the teeth fall into the
same indentations on consecutive rotations, a detrimental process
commonly referred to as "tracking" results.
[0008] With tracking, one or more rows of the cutting elements on
one or more cones tend to fall into the same holes in the borehole
bottom, thereby building up ridges on the bottom. These ridges are
detrimental because they grow in height until they contact the
supporting metal of the cone. This lowers the unit load on the
cutting elements and causes undesirable erosion and wear.
[0009] In the prior art, attempts to reduce tracking typically
consist of methods to vary pitch (i.e., the distance between center
lines of the cutting elements) on overlapping heel rows on
different cones, and/or within a single row on one cone. For
example, a common approach uses a combination of a closely-spaced
heel row on one cone and a wider pitch (e.g., 1.5 times the close
pitch) on an overlapping heel row on another cone. A wider pitch
tends to break up the ridges that form between the impressions made
by the more closely-spaced heel row cutting elements. While
workable, a wider pitch means fewer cutting elements and less
durability. On the other hand, the more closely-spaced row is more
likely to ball in softer, sticky formation. Thus, an improved
solution for overcoming tracking without sacrificing bit life or
penetration rate would be desirable.
SUMMARY OF THE INVENTION
[0010] Embodiments of a system, method, and apparatus for reducing
the harmful effects of tracking with drill bits are disclosed. A
roller cone has a plurality of active teeth arranged generally in
circumferential rows. At least one of the outermost rows contains
one or more teeth having a projection that does not extend to the
height of at least one of the outermost rows on another roller cone
on the bit. This row is designed to engage and remove the formation
that remains as a result of the uncut formation from the space
between adjacent active teeth of the other roller cone. The crest
on this tooth may have a length in a circumferential direction that
is wider than an overall length of the tooth in the outer to inner
direction.
[0011] The cutter design removes the peak of the uncut bottom left
by the other roller cones, significantly removing the depth of the
pocket and allowing the other roller cones to continue to cut with
their crests rather than with the sides of their active teeth or
with their cones. Tracking is reduced regardless of the tooth count
in the other rows or weight on bit. The invention may be used on
any cutter row that shares a common bit diameter and not just the
outermost row. Moreover, the invention may be used on a different
roller cone or row, or more than one cutter row that shares a
common bit diameter.
[0012] The teeth on each cutter may be a combination of full
projection cutting elements dispersed with any of the anti-tracking
or tracking limiter elements described herein. The anti-tracking
feature may be located between the leading and trailing edges of
the tooth on one or more roller cones. The anti-tracking feature
may also be formed more than once and in different locations on any
tooth or combination of teeth. Furthermore, the invention may be
used with gage cutting features, such as a "bar trimmer" aligned
with the cone centerline and also at an angular position.
[0013] Alternatively, a heel row may have a high count of teeth on
a roller cone with teeth configured at a depth that is shorter than
a formation contact depth for active teeth on the other roller
cones. The heel row also may be milled with narrow slots to define
teeth having properties and features as described herein.
[0014] The foregoing and other objects and advantages of the
present invention will be apparent to those skilled in the art, in
view of the following detailed description of the present
invention, taken in conjunction with the appended claims and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] So that the manner in which the features and advantages of
the present invention, which will become apparent, are attained and
can be understood in more detail, more particular description of
the invention briefly summarized above may be had by reference to
the embodiments thereof that are illustrated in the appended
drawings which form a part of this specification. It is to be
noted, however, that the drawings illustrate only some embodiments
of the invention and therefore are not to be considered limiting of
its scope as the invention may admit to other equally effective
embodiments.
[0016] FIG. 1 is a sectional view illustrating a portion of an
earth boring bit constructed in accordance with the invention;
[0017] FIG. 2 is an enlarged isometric view of one embodiment of a
heel portion of a roller cone for the bit of FIG. 1 and is
constructed in accordance with the present invention;
[0018] FIG. 3 is an enlarged isometric view of another embodiment
of a roller cone constructed in accordance with the present
invention;
[0019] FIG. 4 is another isometric view of the roller cone of FIG.
3 on a bit and is constructed in accordance with the present
invention;
[0020] FIG. 5 is an enlarged isometric view of still another
embodiment of a roller cone constructed in accordance with the
present invention;
[0021] FIG. 6 is another isometric view of the roller cone of FIG.
5 on a bit and is constructed in accordance with the present
invention;
[0022] FIG. 7 is an enlarged isometric view of yet another
embodiment of a roller cone constructed in accordance with the
present invention;
[0023] FIG. 8 is a rear view of the roller cone of FIG. 7 and is
constructed in accordance with the present invention;
[0024] FIG. 9 is an isometric view of another embodiment of a
roller cone on a bit and is constructed in accordance with the
present invention;
[0025] FIG. 10 is another isometric view of the roller cone of FIG.
9 and is constructed in accordance with the present invention;
[0026] FIG. 11 is an enlarged sectional view of one embodiment of a
bit illustrating a cutting profile thereof relative to a
borehole;
[0027] FIG. 12 is a schematic side view illustrating effective
depth of cut in accordance with the invention;
[0028] FIG. 13 illustrates top views of various embodiments of
tooth geometries in accordance with the invention; and
[0029] FIGS. 14 and 15 depict rear and isometric views of
embodiments of a cone with anti-tracking features in accordance
with the invention, and is shown with the active teeth of other
cones projected onto the cone.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Referring to FIGS. 1-15, embodiments of an improved system,
method, and apparatus for reducing the harmful effects of tracking
with drill bits are disclosed. One embodiment of a bit 11 (FIG. 1)
has a body 13 with a threaded shank 15 on its upper end for
connection to a drill string (not shown). Body 13 typically has
three bit legs 17 (only one shown), and each leg 17 has a depending
bearing pin 19. Each bearing pin 19 inclines downward and inward
toward an axis 20 of rotation of body 13. Each bearing pin 19 has a
cylindrical surface 21 that is concentric with a bearing pin axis
23. A roller cone 29 is mounted to each pin 19 and has an axial
cavity with a cylindrical portion 31 that fits around bearing
surface 21 of pin 19. Roller cone 29 rotates on pin 19 about its
roller cone axis, which coincides with bearing pin axis 23.
[0031] Each roller cone 29 has a plurality of cutting elements 36
(FIG. 1) on its exterior. Cutting elements 35 may be formed as
steel teeth milled into the exterior surface of the body of cone 29
with or without hardfacing. Alternatively, cutting elements 36 may
comprise tungsten carbide inserts press-fitted into holes in the
body of cone 29, as integral protrusions extending from cone 29, or
other configurations known to those skilled in the art. Cone 29 is
retained conventionally on bearing pin 19, which in this example is
by a plurality of balls 37. Balls 37 engage mating grooves formed
in cone 29 and on bearing pin 19. Lubricant passages 39 supply
lubricant or grease to the spaces between cylindrical surfaces 21,
31 and between thrust faces. A pressure compensator 41 reduces the
pressure differential between the lubricant within passages 39 and
drilling fluid pressure on the exterior of bit 11.
[0032] Referring now to FIGS. 2, 14 and 15, some embodiments of
roller cone 29 have a plurality of "passive" elements (e.g., teeth)
35 that reduce the harmful effects of tracking. Teeth 35 may be
formed integrally on cone 29 and arranged generally in
circumferential rows 51, 53. Each of the teeth 35 includes an outer
end 55 and an inner end 57 that define a length 58, a pair of
flanks 59, 61 (i.e., leading edge and trailing edge, respectively)
and a crest 63 at which the ends 55, 57 and flanks 59, 61 converge.
The outermost row 51 contains one or more teeth 35 having a height
65 that does not extend to the height 67 (shown superimposed) of
the active teeth 36 (FIGS. 14 and 15) on at least one of the
outermost rows the roller cones. Row 51 is designed to engage and
remove the formation that remains as a result of the uncut
formation left behind between tooth impressions of the other roller
cone or cones. The crest 63 on this tooth 35 has a width 69 in a
circumferential direction that is wider than an axial length 58 of
the tooth 35 in the axial direction.
[0033] The embodiments of FIGS. 2, 14 and 15 are shown on the row
that is used to remove the outermost portions of the borehole where
at least two other roller cones on the bit have rows of teeth that
are used to remove the same outer portion of the formation. As
described above, one cutter (i.e., roller cone 29) has a row 51 of
teeth 35 that are shorter (compare height 65 to height 67) than the
same row of active teeth 36 on the other roller cones. The
circumferential width 69 (i.e., in a generally angular direction
with respect to the axis of the cone) of each tooth 35 on row 51 is
shown longer than the crest width 73 (shown superimposed) of active
teeth 36 on the outermost rows on the other roller cones. The
inner-to-outer end length 58 on row 51 is shown shorter than that
of the respective length 75 of active teeth on other rows 53. This
improved cutter design removes the peak of the uncut bottom left by
the active teeth of the other roller cones, significantly reducing
the depth of the valleys and allowing the other roller cones to
continue to cut with their crests and less contact on the sides of
their active teeth or cone shell.
[0034] Although heel tracking can be reduced by increasing the
tooth count, such a configuration results in an increased tendency
to ball, with less effective projection and lower rate of
penetration. Furthermore, it is still subject to tracking although
at a smaller distance between impressions. With the present
invention, the detrimental effect of tracking is reduced even with
low tooth counts in the other rows. The invention may be used on
any cutter row that shares a common distance from the center of the
bit and not just the outermost row as shown. Moreover, the
invention may be used on multiple cutter rows, or within a single
cutter row that has the same distance from the center of the
bit.
[0035] In addition, the teeth on each cutter may be a combination
of full-length cutting elements dispersed with any of the
anti-tracking (or, tracking limiter) elements described herein. For
example, as shown in FIGS. 3 and 4, a tooth 101 on each cutter 129
may comprise a combination of a full-height, active cutting element
integrally morphing into an anti-tracking element 103 (e.g., having
a shorter radial height). For simplicity of illustration, some of
the drawings are shown without an innermost row of teeth. The
morphed portion 103 may be curved and located on the leading edge
of the tooth, or on the trailing edge of the tooth. FIG. 13A
depicts a top view of tooth 101. Morphed portion 103 tapers not
only radially with respect to the axis of cone 129 (FIGS. 3 and 4),
but the crest also tapers in width in the circumferential direction
as shown in FIG. 13A. This design provides tooth 101 with an
overall greater circumferential width than the active teeth on cone
129 or the other cones. Moreover, the tapers may converge in a
crest that is formed at multiple radii or non-uniform radii.
[0036] As shown in FIGS. 5 and 6, the anti-tracking feature 203
(e.g., a scallop) may extend between the two adjacent active teeth
(i.e., the leading and trailing edges of the tooth 201) on one or
more roller cones 229. The anti-tracking feature may also be formed
more than once and in different locations on any tooth or
combination of teeth. FIG. 13B depicts a top view of tooth 201.
Anti-tracking feature 203 tapers not only radially from the crests
or outer portions 205 with respect to the axis of cutter 129 (FIGS.
5 and 6), but also tapers toward the crest at 203 in the
circumferential direction as shown in FIG. 13B. In some
embodiments, this design also provides tooth 201 with an overall
greater circumferential width than the other teeth on cone 229 or
other cones. In other embodiments, however, the crests or outer
portions 205 are configured to maintain the active tooth pitch on
the row, essentially joining two adjacent active teeth with scallop
203.
[0037] Referring now to FIGS. 7 and 8, another embodiment of the
invention comprises a heel row 301 having a higher count of
anti-tracking teeth 303 (or, e.g., tungsten carbide inserts) on a
roller cone 329 than other rows. The teeth 303 are configured at a
projection 305 (i.e., in a radial direction relative to the axis of
the cone) that is shorter than a projection 307 (shown
superimposed) for teeth on the other roller cones. Although the
radial height 305 of teeth 303 is relatively shorter than the
active teeth, it is sufficiently long to break down formation build
up left by other heel rows. As best shown in FIG. 7, the teeth 303
also may be provided with wear pads or weld pads 309 on their backs
or outer surfaces (opposite the next row of teeth). For example,
pads 309 may be provided at thicknesses such as 1/16.sup.th to
1/8.sup.th of an inch.
[0038] The proper difference in projection of teeth 303 from the
active teeth may be varied according to the application. In
addition, teeth 303 may be in any combination of 100% hardfacing
material, hardfaced milled teeth, tungsten carbide inserts,
etc.
[0039] Another embodiment of the invention for a drill bit 401 is
depicted in FIGS. 9 and 10. In this version, an integrally-formed
heel row 403 on a roller cone 405 comprises an anti-tracking
element in the shape of a disk having a plurality of narrow slots
407 formed therein to define the plurality of anti-tracking teeth.
In the embodiment shown, the slots 407 extend radially in a
symmetrical configuration to define elongated teeth having
properties and features as described above for the embodiments of
FIGS. 2, 7, 8, etc.
[0040] One embodiment of an overall cutting profile for a bit
constructed in accordance with the invention is shown in the
superimposed view of FIG. 11. The cutting profile for each row of
teeth is offset from the others. The lower block line 1101 is the
profile or depth of cut of the active drilling elements 1103 (which
are shown in solid lines). The upper block line 1105 is the profile
of the anti-tracking (or, tracking limiter) features or teeth 1107
(which are shown in phantom lines), which extends into a range 1109
of the depth of cut 1101 of the active teeth. FIGS. 13C and D
depict top views of some embodiments of anti-tracking teeth 1107,
which may be aligned or offset with respect to the axis of the
roller cone. In any row, the tracking limiter features can be added
between active cutting elements. The bit, cone or an individual row
may contain any combination of tracking limiter features. Moreover,
the tracking limiter features need not be at the same height on
each side as they transition to the active cutting elements.
[0041] As described above, FIGS. 11 and 12 show the relationship
between the effective depth of cut of active cutting elements 1103
to the projection of the various embodiments of anti-tracking
teeth. The radial height (see, e.g., line 1105) of the
anti-tracking teeth 1107 projects or extends into the range 1109 of
the effective depth of cut of the active teeth. The effective depth
of cut is the distance "normal" teeth 1103 can penetrate the
formation before adjacent teeth contact the formation.
[0042] If any cones share a common row position where the formation
is generally removed by two cones, at least one cone could be
populated with only the tracking limiter features. The shape of the
active and/or tracking limiter features are not limited to
traditional hardfaced radial teeth. The shapes of other either type
could be any combination of pyramid, disk, non-hardened, hybrid,
tungsten carbide inserts, etc.
[0043] This written description uses examples to disclose the
invention, including the best mode, and also to enable those of
ordinary skill in the art to make and use the invention. The
patentable scope of the invention is defined by the claims, and may
include other examples that occur to those skilled in the art. Such
other examples are intended to be within the scope of the claims if
they have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages
of the claims. While the invention has been shown or described in
only some of its forms, it should be apparent to those skilled in
the art that it is not so limited, but is susceptible to various
changes without departing from the scope of the invention.
* * * * *