Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ROCK-BIT SEALS WITH ASYMMETRIC CONTACT PROFILES
BACKGROUND
The present invention relates generally to sealed bearing earth boring drill
bits, such as
rotary cone rock bits. More particularly, the present invention relates to
seal rings for use in rotary
cone rock bits. Still more particularly, the present invention relates to
journal bearing seal rings
used to isolate a lubricated bearing area from abrasive wellbore fluids.
Rock bits are employed for drilling wells in subterranean formations for oil,
gas,
geothermal steam, minerals, and the like. Such drill bits commonly have a body
connected to a
drill string and three cutter cones mounted on the body. The cutter cones are
rotatably mounted on
steel journals or pins integral with the bit body at its lower end. A
lubricated bearing is often used
to support rotation of the cutter cone about the journal pins. Journal bearing
seal rings are used to
isolate the lubricated bearing from abrasive fluids moving through the well.
Journal bearing seal rings are often constructed from an elastomer or rubber
material and have a
symmetric axial cross-sectional geometry. The particular geometric
configuration of the seal
surfaces produces a given amount of seal deflection that defines the degree of
contact pressure or
"squeeze" applied by the dynamic and static seal surfaces against respective
journal bearing and
cone surfaces.
The contact pressure generated by the journal bearing seal ring is the force
that protects the
journal bearing from wellbore fluids. Failure of the journal bearing seal ring
can allow wellbore
fluids to contaminate the journal bearing and can lead to failure of the
bearing. Once the bearing
fails, or becomes severely worn, the cutter cone may no longer operate
properly and the drill bit
will have to be replaced. Replacement of a drill bit can be a time consuming
process, because it
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requires a cessation of drilling operations and removal of the entire drill
string from the wellbore.
Therefore, any improvement that maximizes the life of a drill bit is
beneficial.
Conventional journal bearing seals perform best within a narrow range of
contact pressures
and fluid conditions. Because the seal bears against a rotating surface
between the seal and the leg,
lubricant is often used to decrease the friction forces in this sealing area.
If the contact pressure is
too high, lubricant will not be able to reach the sealing interfaces and the
heat generated by sliding
contact of the seal and the leg will increase. If the contact pressure is too
low, abrasive particles can
enter the sealing interfaces and increase wear of both the seal and the leg.
In either condition, the
life of the seal will be greatly reduced over a seal operating with proper
lubrication and without
abrasive particles.
Thus, there remains a need to develop journal bearing seal rings that overcome
some of
the foregoing difficulties while providing more advantageous overall results.
SUMMARY OF THE PREFERRED EMBODIMENTS
The embodiments of the present invention are directed toward sealing
arrangements for a
rotary cone rock-bit comprising a leg extending from a bit body and a cone
rotatably mounted to
the leg. A seal is disposed radially between the cone and the leg. A footprint
defines an area of
contact between the seal and the leg. Compression of the seal generates a
contact pressure between
the seal and the leg. An axial centerline evenly bisects the footprint into a
mud side and a grease
side. A contact pressure profile defines the contact pressure over the
footprint, wherein the contact
pressure on the mud side of the footprint is greater than the contact pressure
on the grease side of
the footprint.
In certain embodiments, a bit for drilling a borehole into earthen formations
comprises a a
journal shaft extending from a bit body and a rolling cone cutter mounted on
the journal shaft and
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being adapted to rotate about a cone axis. A seal gland is formed by the shaft
and the cone and
comprises a first seal engaging surface on the shaft and a second seal
engaging surface on the cone.
An annular seal is disposed in the gland. The annular seal comprises a
radially inner surface
sealingly engaging the first seal engaging surface and a radially outer seal
surface sealingly
engaging the second seal engaging surface. A seal footprint on one of the seal
engaging surfaces is
defined by the portion of the seal contacting the one seal engaging surface.
The footprint has a
footprint length measured axially relative to the cone axis and being bisected
by a footprint
centerline that is perpendicular to the cone axis. The seal creates a pressure
profile on one of the
seal engaging surface axially along the footprint, the pressure profile being
asymmetric relative to
the centerline.
Thus, the present invention comprises a combination of features and advantages
that
enable it to overcome various problems of prior devices. The various
characteristics described
above, as well as other features, will be readily apparent to those skilled in
the art upon reading
the following detailed description of the preferred embodiments of the
invention, and by
referring to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more detailed description of the preferred embodiment of the present
invention,
reference will now be made to the accompanying drawings, wherein:
Figure 1 is a perspective view of a prior art rock bit;
Figure 2 is a partial cross-sectional view of the rock bit of Figure 1;
Figure 3A is a partial cross-sectional view of a prior art seal;
Figure 3B illustrates the seal of Figure 3A disposed in a seal gland;
Figure 3C illustrates the contact pressure profile of the seal of Figure 3A;
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Figure 4A is a partial cross-sectional view of a seal constructed in
accordance with
embodiments of the invention;
Figure 4B illustrates the seal of Figure 4A disposed in a seal gland;
Figure 4C illustrates the contact pressure profile of the seal of Figure 4A;
Figures SA-B through 9A-B are partial cross-sectional views of and contact
pressure
profiles generated by radial seals that have asymmetric external features;
Figures l0A-B through 12A-B are partial cross-sectional views of and contact
pressure
profiles generated by radial seals that have asymmetric internal features;
Figures 13A-B through 22A-B are partial cross-sectional views of and contact
pressure
profiles generated by radial seals that have a combination of internal and
external asymmetrical
features;
Figures 23A-B through 26A-B are partial cross-sectional views of and contact
pressure
profiles generated by radial seals having multiple material interfaces;
Figures 27A-B through 31 A-B are partial cross-sectional views of and contact
pressure
profiles generated by symmetrical radial seals disposed within asymmetrical
seal glands.
Figure 32A is a partial cross-sectional view of a seal constructed in
accordance with
embodiments of the invention;
Figure 32B illustrates the seal of Figure 32A disposed in a seal gland;
Figure 32C illustrates the contact pressure profile of the seal of Figure 32A;
Figures 33A-33F are cross-sectional views of o-ring seals constructed in
accordance with
embodiments of the invention;
Figures 34A-34D are cross-sectional views of composite o-ring seals
constructed in
accordance with embodiments of the invention;
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Figure 35 is a cross-sectional view of a dual seal assembly constructed in
accordance
with embodiments of the invention; and
Figure 36 is a cross-sectional view of a dual seal assembly constructed in
accordance
with embodiments of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 1, a rock bit comprises body 10 having three cutter
cones 11
mounted on its lower end. A threaded pin 12 is at the upper end of body 10 for
assembly of the
rock bit onto a drill string. A plurality of hardened inserts 13 are pressed
into holes in the surfaces
of cutter cones 11 for bearing on the rock formation being drilled. Nozzles 15
in body 10
introduce drilling fluid into the space around cutter cones 11 for cooling and
carrying away
formation chips drilled by the bit.
Figure 2 is a partial longitudinal cross-section of the rock bit, extending
radially from the
rotational axis 14 of the rock bit through one of the three legs on which the
cutter cones 11 are
mounted. Each leg includes a journal pin 16 extending downwardly and radially,
inwardly on the
rock bit body 10. Journal pin 16 includes a cylindrical bearing surface 17
including lubrication gap
18.
Cuter cone 11 comprises an inner cavity with a cylindrical bearing surface 21.
Bearing
surface 21 interfaces with bearing surface 17 to form the journal bearing that
supports rotation of
cutter cone 11. The bit may also comprise ball bearings 24 that carry thrust
loads tending to
remove cone 11 from the journal pin 16 and thereby retain the cone on the
journal pin.
Grease, or another appropriate lubricant, lubricates the bearing surfaces
between the journal
pin 16 and the cone 11. A supply of grease is provided by a grease reservoir
in cavity 29. Grease
is supplied to the bearing surfaces through lubricant passages 31 and 32.
Grease is retained in the
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bearings by a radial seal 33 between cone 11 and journal pin 16. A pressure
compensation
subassembly, including bellows 37, is included in the grease reservoir in
cavity 29, and acts to
maintain the pressure of the grease within a desired pressure range.
Referring now to Figure 3A, one example of a radial seal 40 comprises a
rectangular body
42 and symmetrical, curved end surfaces 44 and 46. Radial seal 40 is formed
from a resilient
material and may have end portions 48 formed of a second resilient material
having different
properties that the material forming body 42. End portions 48 are molded to
body 42 along
straight, symmetrical interfaces 49.
Figure 3B shows radial seal 40 disposed within a seal gland 50 formed by a
seal groove 52
and a cylindrical sealing surface 54. Radial seal 40 is compressed within seal
gland 50 and forms a
contact footprint 56 on cylindrical sealing surface 54. Footprint 56 is
bisected by axial centerline
58 such that linear dimensions 60 and 62 are equal. For purposes of this
discussion, axial
centerline 58 divides the seal into an abrasive side 64 and a lubricant side
66. Axial centerline 58
may or may not mark the physical interface between the abrasive fluid on one
side of the seal and
the lubricating fluid on the other side of the seal.
Refernng now to Figure 3C, the contact pressure profile exerted by radial seal
40 on
sealing surface 54 is represented by curve 70. Curve 70 is divided by
centerline 58 into a abrasive-
side area 72 and a lubricant-side area 74, which are symmetrical about
centerline 58. The abrasive-
side peak contact pressure 76 and the lubricant-side peak contact pressure 78
both occur at point
80, which is located on centerline 58.
Radial seal 40 thus provides a distribution of sealing contact pressure along
sealing surface
54 that is symmetric about centerline 58. Seals that generate a symmetrical
contact pressure
distribution, such as seal 40, perform best within a narrow range of contact
pressures. If the
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contact pressure is too high, lubricant will not be able to reach the sealing
interfaces and the heat
generated by sliding contact of the seal and the cone will increase.
Similarly, if the contact
pressure is too low, abrasive particles can enter the sealing interfaces and
increase wear of both the
seal and the cone. In either condition, the life of the seal will be greatly
reduced over a seal
operating with proper lubrication and without abrasive particles.
Referring now to Figure 4A, a radial seal 80 comprises a rectangular body 82
and an
asymmetrical, curved end surface 84 having a protruding portion 86. Radial
seal 80 is formed
from a first resilient material and end portion 88 is formed of a second
resilient material having
different properties that the material forming body 82. End portion 88 is
molded to body 82 along
an asymmetrical interface 89 such that the region of end portion 88 adjacent
to protruding portion
86 has a greater thickness of the second resilient material.
Figure 4B shows radial seal 80 disposed within a seal gland 90 formed by a
seal groove 92
and a cylindrical sealing surface 94. Radial seal 80 is compressed within seal
gland 90 and forms a
contact footprint 96 on cylindrical sealing surface 94. Footprint 96 is
bisected by axial centerline
98 such that linear dimensions 100 and 102 are equal. For purposes of this
discussion, axial
centerline 98 divides the seal into an abrasive side 104 and a lubricant side
106. Axial centerline
98 may or may not mark the physical interface between the abrasive fluid on
one side of the seal
and the lubricating fluid on the other side of the seal.
Referring now to Figure 4C, the contact pressure profile exerted by radial
seal 80 on
sealing surface 94 is represented by curve 110, which illustrates that the
contact pressure profile is
asymmetric about centerline 98. Asymmetric end portion 88 of seal 80 helps to
generate the
asymmetric contact pressure profile by having an increased volume of seal
material on one side of
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the seal. Contact pressure profile curve 110 is divided by centerline 98 into
an abrasive-side 112
and a lubricant-side 114
The area under contact pressure profile curve 110 represents the total contact
pressure
applied to the seal. The asymmetric contact pressure profile created by seal
80 results in a the area
under curve 110 on abrasive-side 112 being greater than the area under curve
110 on the lubricant-
side 114. In some embodiments, the area under curve 110 on the lubricant-side
is 95% of the area
under curve 110 on abrasive-side 114. In some embodiments, the area under
curve 110 on the
lubricant-side is 75% of the area under curve 110 on abrasive-side 114. The
asymmetrical contact
pressure profile curve 110 translates into less contact pressure on lubricant-
side 114 and more
contact pressure on abrasive-side 112. The asymmetrical distribution
encourages increased
lubrication and reduced interaction with abrasive particles.
The peak contact pressure 116 on abrasive-side 112 is also higher than the
peak contact
pressure 118 on lubricant-side 114. The highest peak contact pressure may
indicate the interface
between the abrasive fluids and the lubricating fluids. By shifting the
highest peak contact
pressure toward abrasive-side 112, less of footprint 96 is exposed to abrasive
fluids.
Thus, the asymmetrical contact pressure profile 110 has a peak contact
pressure point 116
that is shifted toward abrasive side 104, causing a sharp increase in contact
pressure on the abrasive
side and a more gradual increase in contact pressure on lubricant side 106.
The high contact
pressure on abrasive side 104 acts to prevent abrasive particles from entering
the sealing interface.
The lower contact pressure profile on lubricant side 106 allows lubricants to
more easily enter the
sealing interface.
Some of the performance advantages of seal 80 can be seen by comparing the
contact
pressure distribution shown in Figure 3C with that of Figure 4C. By shifting
the peak contact
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pressure 116 more toward the abrasive side of the seal, as opposed to the
centered location of peak
contact pressure 76, the surface area of the seal that is exposed to the
abrasive fluid is reduced.
Providing a lower magnitude, gradually increasing contact pressure profile on
lubricant side 114,
as opposed to lubricant side 74, a greater surface area of seal 80 will be
exposed to lubricant. both
of these conditions allow for reduced friction between seal 80 and sealing
surface 94. With
reduced friction comes longer sealing life and more reliable performance.
Generation of a desirable contact pressure distribution profile is not limited
to seals similar
to seal 80, but may be achieved a variety of seal configurations. As
illustrated by seal 80, the
external geometry of the seal and/or the geometry of the internal material
interface may be
asymmetric. Non-composite and single material seals may also be used. The
sealing surfaces on
either, or both, the cone and the leg may also be shaped so as to generate an
asymmetric contact
pressure distribution. Further, the asymmetric contact pressure distribution
is not limited to that
shown in Figure 4C and may be any distribution that provides desirable
performance.
Figures SA-B through 31A-B illustrate a variety of sealing arrangements that
provide
asymmetrical contact pressure distributions. Figures SA-B through 9A-B
illustrate radial seals that
have asymmetric external features. Figures l0A-B through 12A-B illustrate
radial seals that have
asymmetric internal features. Figures 13A-B through 22A-B illustrate radial
seals that have a
combination of internal and external asymmetrical features. Figures 23A-B
through 26A-B
illustrate radial seals having multiple asymmetrical material interfaces.
Figures 27A-B through
31A-B illustrate symmetrical radial seals disposed within asymmetrical seal
glands.
Refernng now to Figures SA-B through 9A-B, Figures SA-9A illustrate a radial
seal that
has asymmetrical external features and Figures SB-9B illustrate exemplary
asymmetrical contact
pressure distributions that are generated by each respective seal. In Figures
SA-8A, although only
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one end of each seal is shown, it is understood that the opposing end of each
seal may have a
different construction or the same construction as the illustrated end of the
seal. Figure 9A
illustrates a full cross-section of a radial seal. In each illustration, lower
edge of the seal is the
grease (lubricant) side and the upper edge of the seal is the mud (abrasive
drilling fluid) side.
Referring now to Figures SA and SB, radial seal 100 comprises end portion 102
that has a
ridge 104 of increased thickness on the mud side of the seal so as to generate
contact pressure
profile 106 that is asymmetrical about centerline 108 of the seal contact
footprint.
In Figures 6A and 6B, radial seal 110 comprises end portion 112 that has two
ridges 114 of
increased thickness, with the ridge on the mud side of the seal having a
greater thickness than the
one on the grease side. Seal 110 generates contact pressure profile 116 that
is asymmetrical about
centerline 118 of the seal contact footprint.
In Figures 7A and 7B, radial seal 120 comprises end portion 122 that has
multiple ridges
124 of increased thickness. Seal 120 generates contact pressure profile 126
that is asymmetrical
about centerline 128 of the seal contact footprint.
In Figures 8A and 8B, radial seal 130 comprises a radial groove 132 on body
134 that
reduces the volume of seal material on the grease side of the seal. Seal 130
generates contact
pressure profile 136 that is asymmetrical about centerline 138 of the seal
contact footprint.
In Figures 9A and 9B, radial seal 140 has a tapered cross-section such that
end portion 142
is larger than end portion 144. End portion 144 is offset toward the mud side
of the seal so as to
increase sealing force on the mud side. Seal 140 generates contact pressure
profile 146 that is
asymmetrical about centerline 148 of the seal contact footprint.
Figures l0A-B through 12A-B illustrate radial seals that have asymmetric
internal features.
Referring now to Figures l0A-B through 12A-B, Figures l0A-12A illustrate one
end of a radial
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seal that has asymmetrical internal features found on the interface between
two materials used to
form the seal. Figures lOB-12B illustrate exemplary asymmetrical contact
pressure distributions
that are generated by each respective seal. Although only one end of each seal
is shown, it is
understood that the opposing end of each seal may have a different
construction or the same
construction as the illustrated end of the seal. In each illustration, lower
edge of the seal is the
grease (lubricant) side and the upper edge of the seal is the mud (abrasive
drilling fluid) side.
In Figures l0A and lOB, radial seal 150 comprises end portion 152 that has
asymmetrical
material boundary 154 shaped so as to provide a thicker region of the end
portion material on the
mud side of the seal. Seal 150 generates contact pressure profile 156 that is
asymmetrical about
centerline 158 of the seal contact footprint.
In Figures 11A and 11B, radial seal 160 comprises end portion 162 that has
asymmetrical
material boundary 164 having two regions of increased thickness, with the
thicker of the two
regions on the mud side of the seal. Seal 160 generates contact pressure
profile 166 that is
asymmetrical about centerline 168 of the seal contact footprint.
In Figures 12A and 12B, radial seal 170 comprises end portion 172 that has
asymmetrical
material boundary 174 that has multiple regions of increased thickness. Seal
170 generates contact
pressure profile 176 that is asymmetrical about centerline 178 of the seal
contact footprint.
Figures 13A-B through 22A-B illustrate radial seals that have a combination of
internal and
external asymmetrical features. Figures 13A-22A illustrate one end of a radial
seal that has
asymmetrical internal and external features and Figures 13B-22B illustrate
exemplary
asymmetrical contact pressure distributions that are generated by each
respective seal. In Figures
13A-16A and 18A-21A, although only one end of each seal is shown, it is
understood that the
opposing end of each seal may have a different construction or the same
construction as the
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illustrated end of the seal. In each illustration, lower edge of the seal is
the grease (lubricant) side
and the upper edge of the seal is the mud (abrasive drilling fluid) side.
In Figures 13A and 13B, radial seal 180 comprises an asymmetrical, curved end
portion
182 that also has asymmetrical, v-shaped material boundary 184. End portion
182 and boundary
184 are shaped so as to provide a thicker region of the end portion material
on the mud side of the
seal so as to generate contact pressure profile 186 that is asymmetrical about
centerline 188 of the
seal contact footprint.
In Figures 14A and 14B, radial seal 190 comprises an asymmetrical, curved end
portion
192 with two ridged protrusions, wherein the protrusion that is closer to the
mud side of the seal is
larger. Seal 190 also comprises an asymmetrical, v-shaped material boundary
194, wherein the
deepest part of the v-shape is toward the mud side of the seal. Seal 190 is
shaped so as to provide a
thicker region of the end portion material on the mud side of the seal so as
to generate contact
pressure profile 196 that is asymmetrical about centerline 198 of the seal
contact footprint.
In Figures 15A and 15B, radial seal 200 comprises an asymmetrical, curved end
portion
202 with multiple ridged protrusions, wherein the protrusion that is closer to
the mud side of the
seal is the largest. Seal 200 also comprises an asymmetrical, v-shaped
material boundary 204,
wherein the deepest part of the v-shape is toward the mud side of the seal.
Seal 200 is shaped so as
to provide a thicker region of the end portion material on the mud side of the
seal so as to generate
contact pressure profile 206 that is asymmetrical about centerline 208 of the
seal contact footprint.
In Figures 16A and 16B, radial seal 210 comprises an asymmetrical, curved end
portion
212 and a groove 213 on the lubricant side of the seal body. Seal 210 also
comprises an
asymmetrical, v-shaped material boundary 214, wherein the deepest part of the
v-shape is toward
the mud side of the seal. Seal 210 is shaped so as to provide a thicker region
of the end portion
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material on the mud side of the seal so as to generate contact pressure
profile 216 that is
asymmetrical about centerline 218 of the seal contact footprint.
In Figures 17A and 17B, radial seal 220 comprises an asymmetrical, curved end
portion
222 that is larger than opposite end portion 223. End portion 223 is offset
toward the mud side of
the seal so as to increase sealing force on the mud side. Seal 220 also
comprises an asymmetrical,
v-shaped material boundary 224, wherein the deepest part of the v-shape is
toward the mud side of
the seal. Seal 220 generates contact pressure profile 226 that is asymmetrical
about centerline 228
of the seal contact footprint.
In Figures 18A and 18B, radial seal 230 comprises an asymmetrical, curved end
portion
232 that also has an asymmetrical, curved material boundary 234. End portion
232 and boundary
234 are shaped so as to provide a thicker region of the end portion material
on the mud side of the
seal so as to generate contact pressure profile 236 that is asymmetrical about
centerline 238 of the
seal contact footprint.
In Figures 19A and 19B, radial seal 240 comprises an asymmetrical, curved end
portion
242 with two ridged protrusions, wherein the protrusion that is closer to the
mud side of the seal is
larger. Seal 240 also comprises an asymmetrical, curved material boundary 244,
wherein the
deepest part of the end portion is toward the mud side of the seal. Seal 240
is shaped so as to
provide a thicker region of the end portion material on the mud side of the
seal so as to generate
contact pressure profile 246 that is asymmetrical about centerline 198 of the
seal contact footprint.
In Figures 20A and 20B, radial seal 250 comprises an asymmetrical, curved end
portion
252 with multiple ridged protrusions, wherein the protrusion that is closer to
the mud side of the
seal is the largest. Seal 250 also comprises an asymmetrical, curved material
boundary 254,
wherein the deepest part of the end portion is toward the mud side of the
seal. Seal 250 is shaped
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so as to provide a thicker region of the end portion material on the mud side
of the seal so as to
generate contact pressure profile 256 that is asymmetrical about centerline
258 of the seal contact
footprint.
In Figures 21A and 21B, radial seal 260 comprises an asymmetrical, curved end
portion
262 and a groove 263 on the lubricant side of the seal body. Seal 260 also
comprises an
asymmetrical, curved material boundary 264, wherein the deepest part of the
end portion is toward
the mud side of the seal. Seal 260 is shaped so as to provide a thicker region
of the end portion
material on the mud side of the seal so as to generate contact pressure
profile 266 that is
asymmetrical about centerline 268 of the seal contact footprint.
In Figures 22A and 22B, radial seal 270 comprises an asymmetrical, curved end
portion
272 that is larger than opposite end portion 273. End portion 273 is offset
toward the mud side of
the seal so as to increase sealing force on the mud side. Seal 270 generates
contact pressure profile
276 that is asymmetrical about centerline 278 of the seal contact footprint.
Figures 23A-B through 26A-B illustrate radial seals having multiple
asymmetrical material
interfaces formed between a plurality of component material layers. Figures
23A-26A illustrate
one end of a composite radial seal and Figures 23B-26B illustrate exemplary
asymmetrical contact
pressure distributions that are generated by each respective seal. Although
only one end of each
seal is shown, it is understood that the opposing end of each seal may have a
different construction
or the same construction as the illustrated end of the seal. In each
illustration, lower edge of the
seal is the grease (lubricant) side and the upper edge of the seal is the mud
(abrasive drilling fluid)
side.
In Figures 23A and 23B, radial seal 280 comprises an end portion 282 formed
from two
layers seal material having different properties such that the mud-side layer
283 provides a higher
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contact pressure than lubricant-side layer 284. Seal 280 generates contact
pressure profile 286 that
is asymmetrical about centerline 288 of the seal contact footprint.
In Figures 24A and 24B, radial seal 290 comprises an end portion 292 formed
from two
layers seal material having different properties such that the mud-side layer
293 provides a higher
contact pressure than lubricant-side layer 294. The boundary 295 between end
portion 292 layers
293 and 294 the seal body is also asymmetrical so that seal 290 generates
contact pressure profile
296 that is asymmetrical about centerline 298 of the seal contact footprint.
In Figures 25A and 25B, radial seal 300 comprises an end portion 302 formed
from two
different seal materials having different properties such that the embedded
region 303 has a higher
elastic modulus and/or hardness than the surrounding region 304. Seal 300
generates contact
pressure profile 306 that is asymmetrical about centerline 308 of the seal
contact footprint.
In Figures 26A and 26B, radial seal 310 comprises a plurality of layers 312 of
seal material
having different properties arranged such that the mud-side layer 313 provides
a higher contact
pressure than lubricant-side layer 314. Seal 310 generates contact pressure
profile 316 that is
asymmetrical about centerline 318 of the seal contact footprint.
Figures 27A-B through 31A-B illustrate radial seals disposed within
asymmetrical seal
glands. The radial seals are shown as being symmetrical seals but could also
be asymmetrical
seals, such as those described above. Figures 27A-31 A illustrate the radial
seal disposed in a seal
gland and Figures 27B-31B illustrate exemplary asymmetrical contact pressure
distributions that
are generated by each respective seal arrangement. In each illustration, lower
edge of the seal is the
grease (lubricant) side and the upper edge of the seal is the mud (abrasive
drilling fluid) side.
In Figures 27A and 27B, radial seal 320 is disposed within seal gland 322
comprising seal
groove 324 and engages seal surface 325. Seal surface 325 is angled, or
curved, across a portion of
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the face of seal 320 such that the mud side of the seal is compressed more
than the lubricant side of
the seal. Seal 320 generates contact pressure profile 326 that is asymmetrical
about centerline 328
of the seal contact footprint.
In Figures 28A and 28B, radial seal 330 is disposed within seal gland 332
comprising seal
groove 334 and engages seal surface 335. The bottom of seal groove 334 is
angled, or curved,
such that the mud side of seal 330 is compressed more than the lubricant side
of the seal. Seal 330
generates contact pressure profile 336 that is asymmetrical about centerline
338 of the seal contact
footprint.
In Figures 29A and 29B, radial seal 340 is disposed within seal gland 342
comprising seal
groove 344 and engages seal surface 345. Seal surface 345 and the bottom of
seal groove 344 are
angled, or curved, such that the mud side of seal 340 is compressed more than
the lubricant side of
the seal. Seal 340 generates contact pressure profile 346 that is asymmetrical
about centerline 348
of the seal contact footprint.
In Figures 30A and 30B, radial seal 350 is disposed within seal gland 352
comprising seal
groove 354 and engages seal surface 355. Seal surface 355 is angled, or
curved, across the entire
face of seal 350 such that the mud side of the seal is compressed more than
the lubricant side of the
seal. Seal 350 generates contact pressure profile 356 that is asymmetrical
about centerline 358 of
the seal contact footprint.
In Figures 31A and 31B, radial seal 360 is disposed within seal gland 362
comprising seal
groove 364 and engages seal surface 365. Seal surface 365 and the bottom of
seal groove 364 are
angled, or curved, such that the mud side of seal 360 is compressed more than
the lubricant side of
the seal. Seal 360 generates contact pressure profile 366 that is asymmetrical
about centerline 368
of the seal contact footprint.
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An asymmetrical contact pressure profile may also be generated by an o-ring
type seal.
Referring now to Figure 32A, an radial o-ring seal 370 has a generally
circular cross-section with a
flattened face 372 on one side of the seal. Figure 32B shows seal 370 disposed
within a seal gland
374 formed by a seal groove 376 and a cylindrical sealing surface 378. Face
372 of seal 370 is
disposed on the mud-side of the seal gland and toward sealing surface 378.
Seal 370 is
compressed within seal gland 374 and forms a contact footprint 380 on
cylindrical sealing surface
378. Footprint 380 is bisected by axial centerline 382 such that linear
dimensions 384 and 386 are
equal. For purposes of this discussion, axial centerline 382 divides the seal
into an mud side 388
and a grease side 390. Axial centerline 382 may or may not mark the physical
interface between
the mud on one side of the seal and the grease on the other side of the seal.
Referring now to Figure 32C, the contact pressure profile exerted by radial
seal 370 on
sealing surface 378 is represented by curve 392, which illustrates that the
contact pressure profile is
asymmetric about centerline 382. The abrupt contour change at face 372
generates a peak contact
pressure 394 on the mud side 388 of centerline 382. Contact pressure profile
392 is divided by
centerline 382 into a mud-side area 394 and a grease-side area 396. Although
centerline 382 runs
through the middle of footprint 380, it divides the area under curve 392 into
a mud-side area 396
that is larger and provides a higher gradient of contact pressure than a
grease-side area 398.
Figures 33A-33F illustrate a number of alternate embodiments of o-ring type
seals having
asymmetric cross-sections. Figure 33A shows seal 460 having a flat region 462,
where, when
installed, the flat region is oriented on the mud-side of the dynamic sealing
interface. Figure 33B
shows seal 464 having flat sides 466 for fitting into the rectangular sides of
a groove and a flat
region 468 that is oriented on the mud-side of the dynamic sealing interface.
Figure 33C shows
seal 470 having flat face 472, and curved face 474, which has an increased
diameter. Figure 33D
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CA 02519745 2005-09-13
shows seal 476 having flat face 478, and multiple curved faces 486, each with
a different radius of
curvature. Figure 33E shows seal 488 having curved groove 490. Figure 33F
shows seal 492
having multiple flat faces 494.
In each of these seal designs, the portion of the seal that has material
removed is oriented
toward the mud-side of the dynamic sealing surface. The removed material
creates a stress
concentration that generates a peak in the contact force on the dynamic
sealing surface toward the
mud-side of the seal. Although the features of Figure 33A-F are only shown on
side end of each
seal, it is understood that in some applications the asymmetric features may
be on more than one
side of the seal. The embodiments shown are not inclusive and many other
configurations and
variations of asymmetric profile seals may also be created.
Figures 34A-34D illustrate a number of alternate embodiments of composite o-
ring type
seals having asymmetric cross-sections or asymmetric boundaries between the
two component
materials. Figure 34A illustrates seal 496 comprising a first material 498 and
a second material
500 with an asymmetric material boundary 502. Boundary 502 is formed such that
the depth of
second material 500 is greater on one side so as to create a peak in the
contact force on the mud-
side of the dynamic sealing surface. Figure 34B shows seal 504 having first
material 506 and
second material 508 joined at an asymmetric boundary 510. Figure 34C shows
seal 512 having
first material 514 and second material 516 joined at an asymmetric boundary
518.
Figure 34D shows seal 520 having first material 522 and second material 524
joined at
boundary 526. Second material 524 also has flat surface 528. Although the
features of Figure
34A-D are only shown on side end of each seal, it is understood that in some
applications the
asymmetric features may be on more than one side of the seal. The embodiments
shown are not
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inclusive and many other configurations and variations of asymmetric profile
seals may also be
created.
Figure 35 shows a dual seal assembly 600 comprising a symmetric seal 602 and
asymmetric seal 604. Seal assembly 600 creates a seal between cone 606 and leg
608 forming a
barner between a mud side 610 and a lubricant side 612. Symmetric seal 602
forms a contact
pressure profile 614 along leg 608 that is symmetrical about a centerline
bisecting the profile.
Asymmetric seal 604 forms a contact pressure profile 616 along leg 608 that is
asymmetrical about
a centerline bisecting the profile.
Figure 36 shows a dual seal assembly 620 comprising a first asymmetric seal
622 and
second asymmetric seal 624. Seal assembly 620 creates a seal between cone 626
and leg 628
forming a barrier between a mud side 630 and a lubricant side 632. The first
asymmetric seal 622
forms a contact pressure profile 634 along leg 628 that is asymmetrical about
a centerline bisecting
the profile. The second asymmetric seal 624 forms a contact pressure profile
626 along leg 628
that is asymmetrical about a centerline bisecting the profile.
While preferred embodiments of this invention have been shown and described,
modifications thereof can be made by one skilled in the art without departing
from the scope or
teaching of this invention. The embodiments described herein are exemplary
only and are not
limiting by size, shape and/or directionality of the rotating body against the
stationary body.
Many variations and modifications of the system and apparatus are possible and
are within the
scope of the invention. For example, the relative dimensions of various parts,
the materials from
which the various parts are made, and other parameters can be varied, so long
as the apparatus
retain the advantages discussed herein. Accordingly, the scope of protection
is not limited to the
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CA 02519745 2005-09-13
embodiments described herein, but is only limited by the claims that follow,
the scope of which
shall include all equivalents of the subject matter of the claims.
