U.S. patent application number 12/565914 was filed with the patent office on 2010-03-25 for system, method and apparatus for composite seal gland insert in roller cone rock bit.
This patent application is currently assigned to Baker Hughes Incorporated. Invention is credited to David A. Curry, Stuart Hall, Terry J. Koltermann, Chih C. Lin.
Application Number | 20100071960 12/565914 |
Document ID | / |
Family ID | 42036474 |
Filed Date | 2010-03-25 |
United States Patent
Application |
20100071960 |
Kind Code |
A1 |
Curry; David A. ; et
al. |
March 25, 2010 |
System, Method and Apparatus for Composite Seal Gland Insert in
Roller Cone Rock Bit
Abstract
A composite seal gland insert for a roller cone rock bit is a
polymer composite sleeve containing one or more constituents that
function to significantly lower the wear of the elastomeric seal
ring. A fluid lubricant film also may be used between the elastomer
seal and the gland. The outer surface of the insert is profiled to
provide a sealing surface against which the elastomer seal runs.
The insert is installed over the bearing pin and has a surface that
engages the last machined surface of the leg. A static seal, which
may comprise an additional elastomeric seal, may be used beneath
the gland insert to provide a pressure seal between the insert and
the pin. An adhesive also may be used as the pressure seal and also
to retain the gland insert in the desired position. In addition, a
mechanical anti-rotation device may be used to prevent rotation of
the gland insert.
Inventors: |
Curry; David A.; (The
Woodlands, TX) ; Koltermann; Terry J.; (The
Woodlands, TX) ; Lin; Chih C.; (Spring, TX) ;
Hall; Stuart; (Sale, GB) |
Correspondence
Address: |
Bracewell & Giuliani LLP
P.O. Box 61389
Houston
TX
77208-1389
US
|
Assignee: |
Baker Hughes Incorporated
Houston
TX
|
Family ID: |
42036474 |
Appl. No.: |
12/565914 |
Filed: |
September 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61099657 |
Sep 24, 2008 |
|
|
|
Current U.S.
Class: |
175/371 |
Current CPC
Class: |
E21B 10/25 20130101 |
Class at
Publication: |
175/371 |
International
Class: |
E21B 10/25 20060101
E21B010/25 |
Claims
1. A rock bit, comprising: a body having a bit leg extending
therefrom; a bearing pin extending from the bit leg and having a
bearing pin axis, a last machined surface adjacent the bit leg; a
roller cone rotatably mounted to the bearing pin; a gland defined
between the bearing pin and the roller cone adjacent the last
machined surface; an elastomer seal located in the gland; and a
gland insert located in the gland between the elastomer seal and
one of the bearing pin and the roller cone, the gland insert being
formed from a polymer material.
2. The rock bit according to claim 1, wherein the polymer material
comprises a polymer composite material having a reinforcing
material dispersed within.
3. The rock bit according to claim 2, wherein the reinforcing
material comprises fibers within the polymer material.
4. The rock bit according to claim 3, wherein the fiber comprises
carbon fiber.
5. The rock bit according to claim 1, wherein the polymer material
comprises one of polyetheretherketone (PEEK) and a polyimide.
6. The rock bit according to claim 1, wherein the polymer material
has a low friction material dispersed within at least a part
thereof.
7. The rock bit according to claim 1, wherein a surface of the
gland insert that engages the elastomer seal has a grooved
profile.
8. The rock bit according to claim 1, wherein the gland insert is
installed on the bearing pin, and a surface of the gland insert
engages the last machined surface.
9. The rock bit according to claim 1, further comprising a static
seal between the gland insert and said one of the bearing pin and
the roller cone.
10. The rock bit according to claim 1, further comprising a
mechanical anti-rotation device extending between the gland insert
and the last machined surface to prevent rotation of the gland
insert relative to the bearing pin.
11. A rock bit, comprising: a body having a bit leg extending
therefrom; a bearing pin extending from the bit leg and having a
bearing pin axis, a last machined surface adjacent the bit leg; a
roller cone rotatably mounted to the bearing pin; a gland defined
between the bearing pin and the roller cone adjacent the last
machined surface; an elastomer seal located in the gland and
engaging the roller cone; and a gland insert located in the gland
between the elastomer seal and the bearing pin, the elastomer seal
slidingly engaging an outer diameter of the gland insert, the gland
insert comprising a sleeve formed of a polymer composite material
containing a reinforcing material therein.
12. The rock bit according to claim 11, wherein the polymer
composite material comprises one of polyetheretherketone (PEEK) and
a polyimide.
13. The rock bit according to claim 11, wherein the outer diameter
of the gland insert contains a grooved profile.
14. A rock bit, comprising: a body having a bit leg extending
therefrom; a bearing pin extending from the bit leg and having a
bearing pin axis, a last machined surface adjacent the bit leg; a
roller cone rotatably mounted to the bearing pin; a gland defined
between the bearing pin and the roller cone adjacent the last
machined surface; an elastomer seal located in the gland and
engaging the roller cone for rotation with the roller cone; a gland
insert located in the gland between the elastomer seal and the
bearing pin, the gland insert being a sleeve mounted on the bearing
pin with an anti-rotation device to prevent any rotational movement
of the gland insert relative to the bearing pin, the elastomer seal
being in sliding engagement with an outer diameter of the gland
insert; a static seal of elastomeric material between an inner
diameter of the gland insert and the bearing pin; and the gland
insert being formed of a polymer containing reinforcing fibers and
having a low friction material therein.
15. The rock bit according to claim 14, further comprising a
mechanical anti-rotation device extending between the gland insert
and the bit leg.
16. The rock bit according to claim 14, wherein the reinforcing
fibers are formed of carbon.
17. The rock bit according to claim 14, wherein the polymer
comprises a selected one of polyetheretherketone (PEEK) and a
polyimide.
18. The rock bit according to claim 14, wherein the gland insert
has a greater tensile strength than a tensile strength of the
elastomer seal.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates in general to roller cone rock
bits and, in particular, to an improved system, method and
apparatus for a composite seal gland insert for enhancing the seal
between the bearing pins and the roller cones on a roller cone rock
bit.
[0003] 2. Description of the Related Art
[0004] In roller cone rock bits, wear of the elastomer rotary
bearing seals between the bearing pins and the roller cones is a
primary cause of seal failure. Elastomer seals in current roller
cone bits typically run in glands made up by opposing recesses that
are formed on the bearing pin and on the inner surface of the cone.
Wear occurs on both the elastomer seal itself and on the steel
gland counter face surfaces that are in sliding contact with the
elastomer seal. However, the majority of the wear typically occurs
on the elastomer seal surface. The loss of seal radial
cross-section as well as the loss of the seal contacting surface
design geometry reduces sealing efficiency as there is a reduction
in overall sealing pressure and a change in the distribution of the
sealing pressure on the contacting surfaces. Consequently, there is
an increased probability of drilling fluid ingress into the
bearing, which leads to rapid bearing failure. An improved solution
that overcomes the limitations and problems of prior art designs
would be desirable.
SUMMARY OF THE INVENTION
[0005] Embodiments of a system, method, and apparatus for a
composite seal gland insert in a roller cone rock bit are
disclosed. Wear of the elastomer seal is reduced by reducing the
friction between the seal and mating gland surface. In one
embodiment, the steel seal gland surface is supplemented with the
seal gland insert. The insert comprises a polymer composite sleeve
containing one or more constituents that function to significantly
lower the friction compared to direct engagement with the steel
seal gland. The seal gland insert may comprise a thermoplastic
polymer such as polyetheretherketone (PEEK) or a polyimide.
Preferably, the polymer material contains a reinforcing material
such as carbon fiber. Also, preferably the polymer contains a low
friction additive such as polytetrafluorethylene (PTFE), which is
impregnated into the composite material.
[0006] In one embodiment, a fluid lubricant film is provided
between the elastomeric seal and the composite gland for initial
operation. Subsequently, during operation, the grease or lubricant
of the bit will enter the spaces between the elastomeric seal and
the composite gland. In one embodiment, the outer surface of the
composite gland insert is profiled with a grooved pattern against
which the elastomer seal runs. The insert is installed over the pin
and one surface is located against the last machined surface of the
leg. A static seal, which may comprise an additional elastomeric
o-ring seal, may be used beneath the gland insert to provide a
pressure seal between the insert and the pin. Alternatively, a
suitable adhesive may be used to retain the gland insert in the
desired position. The adhesive may provide the pressure seal
between the insert and the pin. If desired, a mechanical
anti-rotation device also may be used to inhibit rotation of the
gland insert.
[0007] 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
[0008] So that the manner in which the features and advantages of
the present invention are attained and can be understood in more
detail, a 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. However, 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.
[0009] FIG. 1 is an isometric view of one embodiment of a roller
cone rock bit constructed in accordance with the invention;
[0010] FIG. 2 is a sectional view of one embodiment of a leg of a
roller cone rock bit constructed in accordance with the
invention;
[0011] FIG. 3 is an enlarged sectional view of one embodiment of a
lower portion of a seal assembly on a leg of a roller cone rock bit
constructed in accordance with the invention; and
[0012] FIG. 4 is an enlarged sectional view of the insert employed
in the seal assembly of FIG. 3.
[0013] FIG. 5 is an enlarged view of a portion of the outer
diameter of the insert of FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring to FIGS. 1-5, embodiments of a system, method and
apparatus for a composite seal gland insert for enhancing the seal
between the bearing pins and the roller cones on a roller cone rock
bit are disclosed. FIGS. 1 and 2 illustrate a rock bit 11 having a
body 13 with a threaded upper end for attachment to the lower end
of a drill string. Body 13 has at least one bit leg 15 (typically
three) that extend downward from it. Each bit leg 15 has a bearing
pin 17 (FIG. 2) that extends downward and inward along an axis 16.
Bearing pin 17 has an outer end, referred to as the last machined
surface 19, where it joins bit leg 15.
[0015] In one embodiment, bearing pin 17 has a main journal surface
18 and a nose 21 having a smaller diameter than surface 18 that is
formed on its inner end. Nose 21 also has a pilot pin radial
bearing surface 22 that is parallel to surface 18 relative to axis
16. In another embodiment (e.g., for larger diameter bits), roller
bearings may be used instead of journal bearings. The invention is
well suited for both types of applications.
[0016] A roller cone 23 is rotatably mounted to bearing pin 17.
Cone 23 has a plurality of protruding cutting elements 25. Cone 23
has a cavity 27 that is slightly larger than the outer diameters of
bearing pin 17. Cone 23 may be retained in more than one manner. In
the embodiment shown, cone 23 is retained on bearing pin 17 by a
plurality of balls 33 that engage a mating annular recess formed in
cone cavity 27 and on bearing pin 17. Balls 33 lock the roller cone
23 to bearing pin 17 and are inserted through a ball passage 35
during assembly after cone 23 is placed on bearing pin 17. Ball
passage 35 extends to the exterior of bit leg 15 and may be plugged
as shown after balls 33 are installed.
[0017] In the embodiment shown, a portion of cavity 27 slidingly
engages journal surfaces 18 and 22. In one embodiment, the outer
end of journal surface 18 is considered to be at a junction with
the gland area engaged by a seal assembly 31, and the inner end of
journal surface 18 is considered to be at the junction with the
groove or race for balls 33. Journal surfaces 18 and 22 serve as a
journal bearing for loads imposed along the axis of bit 11. Again,
other types of drill bits may utilize roller bearings instead of
journal bearing surfaces and are readily configured for the
invention.
[0018] In a sealed lubricated bearings embodiment, a lubricant port
37 is located on an exterior portion of journal surface 18 of
bearing pin 17. The port 37 is connected to a passage 39 via ball
passage 35. Passage 39 leads to a lubricant reservoir 41 that
contains a lubricant. Lubricant reservoir 41 may be of a variety of
types. In one embodiment, an elastomeric diaphragm 43 separates
lubricant in lubricant reservoir 41 from a communication port 45
that leads to the exterior of bit body 13. Communication port 45
communicates the hydrostatic pressure on the exterior of bit 11
with pressure compensator 43 to reduce and preferably equalize the
pressure differential between the lubricant and the hydrostatic
pressure on the exterior.
[0019] Cone 23 also has a back face 29 that is located adjacent,
but not touching, last machined surface 19. A seal assembly 31 is
located in a seal cavity adjacent to the back face 29. As shown in
the embodiment of FIG. 3, the seal assembly 31 is located in a
gland 51 formed between the bearing pin 17 and cone 23 adjacent to
the last machined surface 19. In one embodiment, the seal assembly
31 comprises an elastomeric or dynamic seal 53 that is located in
gland 51 in roller cone 23 for rotation with cone 23. In this
version, the dynamic seal 53 is axially spaced apart and free of
contact with the last machined surface 19. In this embodiment,
gland 51 comprises a groove formed in cone cavity 37, having flat
sidewalls on opposite sides of dynamic seal 53. In an alternate
embodiment, gland 51 has only a single, outward facing sidewall.
Dynamic seal 53 may be a conventional seal used in rolling cone
bits. In this embodiment, it has a greater radial thickness from
its inner radius to its outer radius than its axial width.
[0020] The seal assembly 31 also comprises a gland insert 55 that
is a ring located in the gland 51 between the dynamic seal 53 and
the bearing pin 17. In other embodiments, however, the positions
may be reversed such that the gland insert 55 engages only the cone
23 and the dynamic seal 53 engages the bearing pin 17. In some
embodiments, the gland insert 55 engages the last machined surface
19, and no portion of the gland insert 55 engages the roller cone
23. Dynamic seal 53 engages gland 51 in sliding or dynamic
engagement in all of the embodiments. Gland insert 55 is generally
rectangular in cross-section in this embodiment and has a beveled
corner on its outer edge that engages the rounded intersection of
last machined surface 19 and bearing pin 17.
[0021] The gland insert may comprise a polymer composite sleeve
that reduces wear of the elastomer seal by reducing the friction
between it and the mating gland surface. The gland insert may
contain one or more constituents that function to significantly
lower the friction compared to direct engagement with the steel
seal gland. The term "composite" is used herein to mean a polymer
material containing a reinforcing material that is dispersed
through at least a part thereof and structurally joined with the
polymeric material. For example, composite gland insert 55 may
comprise a thermoplastic polymer such as polyetheretherketone
(PEEK) or a polyimide as the matrix material. The reinforcing
material 56 (FIG. 4) may be carbon fiber or glass fiber. The
composite gland insert may also contain a low friction additive
such as polytetrafluorethylene (PTFE). The low friction material is
dispersed within the polymer matrix in a known manner. The
dispersed low friction material extends at least 0.050 inch from
the outer diameter inward into gland insert 55 or may be throughout
gland insert 55.
[0022] Composite gland insert 55 must be capable of withstanding
the elevated temperatures that occur during drilling. Typically,
dynamic seal 53 is of a rubber-based material that may withstand
about 375 degrees F. without significant degradation. Preferably
composite gland insert 55 is capable of withstanding about 400-500
degrees F. without significant degradation. Gland insert 55 is much
harder and less resilient than composite dynamic seal 53. For
example, the tensile strength in teems of pounds per square inch of
gland insert 55 may be ten times or more greater than the tensile
strength of dynamic seal 53. The inner diameter of gland insert 55
is preferably only slightly greater than the outer diameter of
journal 18, for example about 0.002 to 0.005 inch. Consequently,
gland insert 55 may be considered to be rigidly mounted on journal
18 so that it is not axially movable relative to journal 18.
[0023] In still other embodiments, the surface of gland insert 55
that engages dynamic seal 53, which is the outer diameter of insert
55 in this example, is profiled to enhance lubrication. As
illustrated in FIG. 5, the profile may comprise wavy or sinusoidal
grooves 60. Alternately, grooves 60 could be helical,
chevron-shaped or other patterns. In addition, as shown in FIG. 3,
seal assembly 31 may further comprise a static seal 61 located
between the inner diameter of gland insert 55 and the bearing pin
17. Static seal 61 provides a pressure seal to prevent lubricant
leakage and/or drilling fluid ingress beneath seal gland insert 55.
Static seal 61 may be a ring of a rubber-based material seated
within a recess 63 within the inner diameter of gland insert 55.
Static seal 61 has a cross-sectional dimension that is much smaller
than the cross-sectional dimension of dynamic seal 53. For example,
it may have a circular cross-section with a diameter less than
0.020 inch. Additionally, a static seal arrangement may retain
gland insert 55 so as to keep it from rotating around journal 18.
For example, the static seal arrangement may comprise an adhesive
rather than an elastomeric ring.
[0024] Adhesive, if employed, may serve also to prevent gland
insert 55 from rotating around journal 18. Alternately, a
mechanical anti-rotation device 65 (e.g., a pin, as shown in FIG.
3) extends from last machined surface 19 and engages a notch in
gland insert 55 to prevent rotation of the gland insert 55 relative
to the bearing pin 17.
[0025] 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.
* * * * *