Patent Application
20160281434
The present invention relates to a seal assembly for sealing between a shaft and rotatable member disposed on the shaft. In a second aspect, the invention relates to a roller cone drill bit comprising such a seal assembly.
Roller cone drill bits are drilling tools used in the oilfield and gas industry for drilling wells in earth formations. Roller cone drill bits are attached to a drillstring or a bottom hole assembly. The bit is constructed of at least one leg, generally three legs welded together. A journal or shaft extends on the leg and a roller cone is rotatably mounted on the journal. The roller cone is supported on the journal pin by journal or roller bearings. The roller cone comprises cutting inserts, generally made of tungsten carbide and designed for gouging and crushing the formation being drilled. The bit body comprises nozzles generally directed towards the cutting surfaces of the roller cone or the hole bottom for projecting a drilling fluid providing cleaning and cooling of the surfaces of the roller cone and providing evacuation of the cuttings from the borehole. When drilling a wellbore, the drillstring is rotated, the roller cones roll along the bottom of the hole in a circle and the cutting inserts or teeth in contact with the bottom of the hole crush and gouge the rock that is evacuated by the circular motion of the roller cone and by the drilling fluid.
Generally, sealed roller cone drill bits comprise a grease passage system and a grease system pressure compensation mechanism as disclosed for example in U.S. Pat. No. 6,170,830, for lubricating the bearings. Lubrication of bearings extends the lifetime of the roller cone drill bit. Sealing means are provided at the interface between the journal and the roller cone for retaining lubricant within the journal bearing surface area and for preventing for example drilling fluid, hydrocarbons, and/or drilling debris from impinging upon the interior of the journal/roller cone interface and thereby damaging radial and thrust bearings.
Due to the drilling environment, the sealing means must endure a large range of temperatures and pressures conditions to maintain the lubricant in the space formed between the journal and the roller cone and to prevent contaminants from entering into that space. Despite seals formed as one single ring of rubber or other elastomeric configuration that display excellent sealing properties of elasticity and conformity to mating surfaces, they often have poor tribological properties, high coefficient of friction and low resistance to abrasion, pressure and to high temperatures.
Some attempts to improve the lifetime of O-rings have been done and are discussed in document US2012/0312602. In that document, a reinforcing layer is embedded under the sealing surface of the O-ring, increasing the sealing performance. However, high speed rotation of the roller cone and friction between the surface of the sealing surface of the O-ring and the surface of the journal pin heats the O-ring, which may lead to deformation and reduced lifetime of the O-ring. Also, the roughness and rigidity of the O-ring provided by reinforcement layer and possible wobbling, caused by the drilling forces of the cutting structure, of the roller cone under high speed rotation of the roller cone may still lead to leakage of grease and contamination of the space between the journal and the roller cone by drilled debris. The drilling fluid mixed with debris of cuttings becomes an abrasive fluid that may penetrate within the space between the roller cone and the journal pin and may damage the journal bearings and bushings.
A sealing means for a roller bit is disclosed in document U.S. Pat. No. 5,005,989 and represented in
A first problem of this roller bit is the time consuming fixation of the hard first insert and the second hard insert respectively on the pin and on the cone. Another problem is that the O-ring 118 is an elastomer seal compressed in two points between the first outer surface 101 of the first L shaped ring member 117 and the second inner surface 102 of the second L shaped ring member 123. The O-ring is submitted under high constraints and temperatures which can deform and wear the O-ring. Once the O-ring is deformed or wears out, the sealing effect is affected and the first insert and second insert may enter in contact with each other and provide more friction and more heating.
Another sealing means is disclosed in the document U.S. Pat. No. 4,699,387 and represented in
The second ring member 212 is arranged between the first ring member 210 and the third ring member 211. The second ring member 212 urges the first ring member 210 at a first point 220 of the first portion 224 and at a second point 222 of the second portion 222, and urges the third ring member 211 at a first point 221 of the first portion 225 and at a second point 223 of the second portion 227. The second ring member 212 further provides a sealing contact with a first surface 228 of a first cylinder 201 and with a second surface 229 of a second cylinder 202. Prior its use, the second ring member 212 is toroid and while arranged for sealing the cylindrical outer wall 201 against the cylindrical inner wall 202, the two opposite sides 203, 204 forming the sealing contact between the two cylinder's surfaces gets flattened. Such a sealing assembly provides too much friction and would get worn too quickly to be used in a roller cone bit.
Another sealing means for a roller cone bit is disclosed in document US2010/0089657. The roller cone bit comprises a leg 313 provided with a pin 315 having a longitudinal axis 316, the pin 315 on which is mounted a roller cone 317. The cone 317 comprises a groove 331 perpendicular to the axis 316 of the bearing pin 315, the groove 331 in which a sealing means is arranged. The groove comprises a base 334 parallel to the axis 316 of the pin 315. An O-ring 339 engages the groove base 334 and the bearing pin 317. A first companion ring 341 and a second companion ring 383 are arranged in the groove 331 of the cone 317 on both sides of the O-ring 339. The first and second companion rings 341, 383 may engage the groove base 334 and the bearing pin 317. Preferably, the first and second companion rings 341, 383 don't engage the groove base 334 and the pin 315. The O-ring 339 is an elastomer seal and companion rings 383 and 341 are not seals but just seal protectors. The O-ring 339 is compressed in two points 335 and 337 between the groove base 334 and the pin 315. Continuous compression of the O-ring between two parts rotating relative to each other can deform the O-ring, produce friction that accelerates wearing of the O-ring and affect the sealing.
Another sealing means for a roller cone bit is disclosed in document U.S. Pat. No. 4,466,621 and represented in
There is still a need to improve the tribological properties of journal bearing seals, to improve their wear resistance, to reduce their coefficient of friction, and improve their temperature endurance and stability.
There is a need to improve roller cone drill bits for preventing contamination of the space between the journal pin and the roller cone and thus preventing damages on the journal bearings and bushings.
According to a first aspect, the present invention relates to a seal assembly for sealing between fixed member and a rotatable member adapted for rotating around an axis in relation e.g. by linking or attachment to said fixed member, the seal assembly comprising:
Preferably, the third ring member is made of a material having a Young modulus higher than the Young modulus of the material of said first ring member in the vicinity of the first surface and/or of the material of the second ring member in the vicinity of the second surface.
Preferably, the third ring member is made of a material having a young modulus higher than 100 GPa.
Preferably, the first surface and said third ring member have a curvature such that said third ring member is contacting said first surface at two points.
Preferably, the second surface and said third ring member have a curvature such that said third ring member is contacting said inner surface at two points.
Alternatively, the first outer surface and said third ring member have a curvature such that said third ring member is contacting said first outer surface at one point.
Alternatively, the second inner surface and said third ring member have a curvature such that said third ring member is contacting said second inner surface at one point.
Preferably, the material of said first ring member in the vicinity of the first surface and/or the material of the second ring member in the vicinity of the second surface comprise an elastomer.
Preferably, the third ring member is coated with a friction-reducing material.
Preferably, the first ring member is adapted for fitting on or in said fixed member in a non-rotatable way.
Preferably, the second ring member is adapted for fitting on or in said rotatable member in a non-rotatable way.
In a first embodiment of the invention, the fixed member comprises a shaft and said rotatable member comprises a cavity, said shaft and said cavity being adapted for rotation of said rotatable member around said axis.
In a first variation of the first embodiment, the first ring member is adapted for being fitted around said shaft, said first surface being oriented radially outwards; said second ring member is adapted for being fitted inside said cavity of said rotatable member, said second inner surface being oriented radially inwards and facing said first surface, said length extending in a direction parallel to said shaft.
In a second variation of the first embodiment, the first ring member is adapted for being fitted on a surface of fixed member perpendicular to said shaft, said first surface being oriented axially in the direction of said shaft; said second ring member is adapted for being fitted on said rotatable member, said second surface being oriented axially in the direction of said shaft and facing said first surface, said length extending in a direction radial to said shaft.
In a third variation of the first embodiment, the first ring member is adapted for being fitted on a surface of said fixed member oriented in a direction intermediate between a radially outwards direction and an axial direction in the direction of said shaft; said second ring member is adapted for being fitted inside said rotatable member, said second inner surface being oriented in a direction facing said first outer surface, said length extending in a direction perpendicular to said intermediate direction.
In a second embodiment of the invention, the fixed member comprises a cavity and said rotatable member comprises a shaft, said shaft and said cavity being adapted for rotation of said rotatable member around said axis.
In a first variation of the second embodiment, the first ring member is adapted for being fitted inside said cavity of said fixed member, said first surface being oriented radially inwards; said second ring member is adapted for being fitted around said shaft of said rotatable member, said second surface being oriented radially outwards and facing said first surface, said length extending in a direction parallel to said shaft.
In a second variation of the second embodiment, the first ring member is adapted for being fitted on a surface of fixed member perpendicular to said cavity, said first surface being oriented axially in the direction of said shaft; said second ring member is adapted for being fitted on said rotatable member, said second surface being oriented axially in the direction of said shaft and facing said first surface, said length extending in a direction radial to said shaft.
In a third variation of the second embodiment, the first ring member is adapted for being fitted on a surface of said fixed member oriented in a direction intermediate between a radially inwards direction and an axial direction in the direction of said shaft; said second ring member is adapted for being fitted around said rotatable member said second inner surface being oriented in a direction facing said first outer surface, said length extending in a direction perpendicular to said intermediate direction.
According to a second aspect, the present invention relates to a roller cone drill bit comprising
Preferably, the roller cone comprises a groove for insertion of said second ring member.
Preferably, the bit leg comprises a first substantially flat surface, said roller cone comprises a second groove aligned with each other, centered on the central axis of the shaft, and in which is substantially flat surface facing said first substantially flat surface, both surfaces having a circularly disposed a fourth ring member.
Preferably, the fourth ring member comprises a cavity at its periphery.
Preferably, the cavity of said fourth ring member extends along the entire perimeter of the said fourth ring member.
Preferably, the fourth ring member is made of a material having a Young's modulus superior to 100 GPa.
Preferably, the fourth ring member is coated with a friction-reducing material.
a seal assembly (1) for sealing a first member (10) and a second member (3), arranged coaxially to rotate relative to each other, the seal assembly (1) comprising:
Preferably, the seal assembly (1) is characterized in that said first concave surface (34) and said second concave surface (36) provide multiple sealing surfaces (9a, 9b, 9c, 9d) contacting said third ring member (7) thus allowing the said third ring member (7) to rotate freely between the said first concave surface (34) and the second concave surface (36) and in self-alignment relative to the movement of the rotatable member (3).
Preferably, the seal assembly (1) is characterized in that said third ring member (7) is made of a material having a Young modulus higher than the Young modulus of the material of said first ring member (4) in the vicinity of the first surface (34) and of the material of the second ring member (6) in the vicinity of the second surface (36).
Preferably, the seal assembly (1) is characterized in that the said third ring member (7) is made of a material having a young modulus higher than 100 GPa.
Preferably, the seal assembly (1) is characterized in that the said first concave surface (34) comprises a first deeper area (40) out of contact with the said third ring member (7) and two areas (9a, 9b) on both sides of the said first deeper area (40) providing a sealing surface in contact with the third ring member (7), and the said second concave surface (36) comprises a second deeper area (41) out of contact with the said third ring member (7) and two areas (9c, 9d) on both sides of the second deeper area (41) providing a sealing surface in contact with the said third ring member (7).
Preferably, the seal assembly (1) is characterized in that the material of said first ring member (4) in the vicinity of the first surface (34) and/or the material of the second ring member in the vicinity of the second surface (36) comprise an elastomer.
Preferably, the seal assembly (1) is characterized in that said third ring member (7) is coated with a friction-reducing material.
In a second aspect, the present invention relates to a roller cone drill bit (100) comprising
Preferably, the roller cone drill bit (100) is characterized in that the roller cone (3) comprises a groove (11) for insertion of said second ring member (6).
Preferably, the roller cone drill bit (100) is characterized in that the bit leg (10) comprises a first substantially flat surface (12), said roller cone (3) comprises a second substantially flat surface (13) facing said first substantially flat surface (12), both surfaces (12, 13) having a circular groove (14, 14′) aligned with each other, centered on the central axis (15) of the shaft (2), and in which is disposed a fourth ring member (16).
Preferably, the roller cone drill bit (100) is characterized in that said fourth ring member (16) comprises a cavity (17) at its periphery.
Preferably, the roller cone drill bit (100) is characterized in that said cavity (17) of said fourth ring member (16) extends along the entire perimeter of the said fourth ring member (16).
Preferably, the roller cone drill bit (10) is characterized in that said fourth ring member (16) is made of a material having a Young's modulus superior to 100 GPa.
Preferably, the roller cone drill bit (10) is characterized in that said fourth ring member (16) is coated with a friction-reducing material.
Referring to
The seal assembly 1 comprises:
The first ring member 4 comprises a first outer surface 34 along the outer periphery of the first ring member 4. The second ring member comprises a second inner surface 36 along the inner periphery of the second ring member 6. The two surfaces 34 and 36 are facing each other along a length.
The vicinity of the first outer surface 34 of the first ring member 4 and the vicinity of the second inner surface 36 of the second ring member are made of substantially deformable materials, whereas the third ring member 7 is made of a stiffer material than both vicinity of first outer surface 34 and second inner surface 36. It is also important that each of the first outer surface 34 and the second inner surface 36 are in contact with said third ring member 7 so as to provide an efficient sealing between the rotatable member 3 and the shaft 2. Preferably, both first outer surface 34 and second inner surface 36 are not in contact with each other for minimizing friction forces between the rotatable member 3 and the shaft 2 while the rotatable member 3 rotates relative to the shaft 2.
The material of the first ring member, at least in the vicinity of the first outer surface 34, and of the second ring member, at least in the vicinity of the second inner surface 36, may comprise rubber or an elastomeric material selected from the group including but non-limited to acrylonitrile polymers including acrylonitrile-butadiene rubber (NBR) hydrogenated nitrile butadiene rubber (HNBR), carboxylated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, ethylene propylene, ethylene propylene diene, fluoroelastomers, tetrafluoroethylene-propylene copolymers, fluorocarbons, perfluoroelastomers and the like, and mixtures thereof.
Advantageously, at least one of the said first ring member 4 and the second ring member 6 are made of one of the said elastomeric or rubber materials cited above and comprise one or more lubricant additives to provide enhanced properties of wear and friction reduction such as but non-limited to polytetrafluoroethylene, molybdenum disulfide, graphite flake, hexagonal boron nitride and the like, and mixture thereof.
In an embodiment of the present invention, at least one of the whole first ring member 4 and the whole second ring member 6 are made of rubber or elastomeric material as disclosed herein above, preferably including one or more lubricant additives as disclosed herein above.
In another embodiment of the present invention, at least one of the first ring member 4 and second ring member 6 comprise a reinforcing material 4b, 6b, located below 5 the first outer surface 34 or second inner surface 36, for example embedded in the ring member as presented on
The said second ring member 6 comprises a contacting surface 6a in contact with the said rotatable member 3. It is preferred that the assembly is such that no rotation or slip occurs between the second ring member 6 and the rotatable member 3. This occurs when the friction force between the contacting surface 6a and the rotatable member is higher than the friction force between the second cavity surface 36 and the third ring member 7. In an embodiment of the invention as presented on
Preferably, said third ring member 7 is made of a material having a Young's module larger than 100 GPa. Preferred materials for said third ring member are selected from alloys or ceramics. More preferred materials must have good properties of stiffness, good chemical inertia, resistance to wear and to high temperatures. Advantageously, the third ring member should have a low cost of production. Those preferred materials include brass, bronze copper, beryllium bronze, 18-10 stainless steel, steel, and zirconium dioxide. These materials are not limitative to the present invention.
Preferably, the third ring member 7 is coated with a material minimizing friction between said third ring member 7 and both of said first ring member 4 and said second ring member 6.
Advantageously, the coating material must provide a low friction coefficient on the first contacting surface 34 and the second contacting surface 36. Such a coating material must also have a good adhesion on the substrate, a good resistance to wear and to high temperatures. Preferred coating materials for the third ring member 7 includes PTFE (Polytetrafluoroethylene), PTFE/Molybdenum disulfide, PTFE/graphite, graphite and Molybdenum disulfide, Titanium carbide, chromide carbide and diamond like carbon. These materials are not limitative to the present invention.
Preferably, the third ring member 7 is toroidal. The first ring member 4 provides 2 surfaces of sealing 9a, 9c contacting the third ring member 7, and the second ring member 6 provide 2 surfaces of sealing 9b, 9d contacting the third ring member 7.
According to a second aspect, the present invention relates to a roller cone drill bit 100. An example of a perspective three dimensional view of a roller cone drill bit is represented in the
The roller cone 3 comprises hard material cutting inserts 3a, preferably made of tungsten carbide. Preferably, the roller cone 3 comprises a base 13 facing a substantially flat surface 12 of the bit leg 10. The base 13 of the roller cone 3 comprises a cavity designed for inserting a shaft or journal pin 2 rising from the substantially flat surface 12 of the bit leg 10 and for the bearing members and cone retention ball bearings 5. Both journal pin 2 and cavity of the roller cone 3 comprises complementary bearing races for cone retention ball bearings 5, radial bearings 22 and thrust bearing 24. The journal pin 2 further comprises a first channel 19 for introducing balls 5. The first channel 19 is closed by a ball retainer 23 fixed, typically by welding, inside the channel once the balls 5 are in place. More preferably, the journal pin 2 further comprises a second channel 20 connected to the first channel 19 and to a reservoir 18 containing a lubricant for lubrication of the bearing system 5, 22 and 24. The channel for the lubricant to enter the bearing is through the ball race. It is from that point that the lubricant is distributed throughout the bearing system. When lubricated, the space between the journal pin 2 and the cavity of the roller cone 3 is completely filled with lubricant. A third channel 21 may be provided in connection with one of the first or second channel and one of the radial bearings 22 or thrust bearings 24 for allowing the circulation of the lubricant.
The seal assembly is arranged in the roller cone drill bit such that said first ring member 4 and said second ring member 6 provide multiple sealing surfaces 9a, 9b, 9c, 9d contacting said third ring member 7 thus allowing the said third ring member 7 to rotate freely between the said first outer surface 34 and the second inner surface 36 and in self-alignment relative to the movement of the rotatable member 3.
Preferably, the journal pin 2 comprises a bottom section adjacent to the bit leg, the bottom section having a bigger diameter for making a press fit between that bottom section and the first ring member 4.
The said cavity of the roller cone comprises a recess or preferably a groove 11 having for example a rectangular cross section machined parallel to the base 13 of the roller cone for inserting said seal assembly.
The method of mounting the roller cone drill bit includes the steps of:
In another embodiment of the invention, as presented on
Preferably, the fourth ring member 16 comprises a cavity 17 at its periphery. More preferably, the cavity 17 of the fourth ring member 16 extends along the entire perimeter of the said fourth ring member 16. Larger particles of debris are trapped by this cavity and fluid flowing through this cavity tends to remove these particles out of the cavity and out of the space between the base of the roller cone and the flat surface of the body facing the base of the roller cone.
More preferably, fourth ring member 16 is made of a material having a Young's modulus larger than 100 GPa such as the possible materials disclosed hereinabove for the said third ring member.
Preferably, said fourth ring member 16 is coated with an abrasive resistant coating such as Titanium nitride, or aromatic polyamine (Kevlar). Said fourth ring member can also be carburized or boronized.
Preferably, the roller cone bearing surfaces are hardened, and journal surfaces are hardened typically by carburizing or boronizing the steel surfaces.
The seal assembly as disclosed herein above and its use for sealing a space formed by a journal and a cavity of a roller cone provides the advantages of an improved sealing and an increased lifetime of the sealing relative to prior art sealing means, in particular in the field of roller cone drill bits.
While drilling with a roller cone drill bit comprising the seal assembly as disclosed hereinabove, the relative speed of the sealing ring 7 that floats freely in the cavities formed by 34 and 36 will be typically less than the rotational speed of the cone, thus limiting the heat generation of the seal due to frictional forces. This improvement of this seal was not possible with other typical sealing system configurations.
Alternatively, the present invention can be described as herein below.
Referring to
In the context of the present invention, we define the orientation of a surface of a member as a vector normal to said surface and pointing to the outside of said member. When the surface have a curvature, we will consider the orientation of the surface as being the mean of the vectors normal to the surface.
In that embodiment, the first concave surface 34 of the first ring member 4 and the second concave surface 36 of the second ring member 6 are both oriented perpendicularly to the axis 15 of the shaft 2, the first surface 34 radially outwards, and the second surface radially inwards. The first ring member 4 comprises a first outer surface 34 along the outer periphery of the first ring member 4. The second ring member comprises a second inner surface 36 along the inner periphery of the second ring member 6. The two surfaces 34 and 36 are facing each other along a length.
In a second variation of said first embodiment, presented in the
In third variation of the first embodiment, presented in the
In a second embodiment of the invention, not represented, the fixed member comprises a cavity and the rotatable member comprises a shaft rotatably mounted in said cavity. Corresponding first, second and third variation of the arrangement of the seal assembly with respect to radial, axial or intermediate orientation of the first and second surfaces exist.
The vicinity of the first concave surface 34 of the first ring member 4 and the vicinity of the second concave surface 36 of the second ring member are made of substantially deformable materials, whereas the third ring member 7 is made of a stiffer material than both vicinity of first concave surface 34 and second concave surface 36. It is also important that each of the first concave surface 34 and the second concave surface 36 are in contact with said third ring member 7 so as to provide an efficient sealing between the rotatable member 3 and the shaft 2. Preferably, both first concave surface 34 and second concave surface 36 are not in contact with each other for minimizing friction forces between the rotatable member 3 and the shaft 2 while the rotatable member 3 rotates relative to the shaft 2.
In the example of
In the advantageous embodiments of
Combinations with one contact point on one side and two on the other one may also be made. These contact points may also extend and form contact surfaces. The advantage of having two areas providing two contact surfaces on both sides of a deeper area out of contact with the third ring member and separated from each other on both side of the third ring member 7 is that the contact forces between the third ring member 7 and both concave surfaces are distributed on two points on each concave surface 34, 36 of the first and second ring member 4, 6, reducing therefore the load and the resulting fatigue on the deformable surfaces 34, 36 of the first and second ring members 4, 6. The lifetime of the seal assembly is therefore prolonged. The other advantage of having two areas providing two contact surfaces separated from each other by a deeper area out of contact with the third ring member, on both side of the third ring member 7 is that the friction between the first ring member 4 and the third ring member 7 and the friction between the second ring member 6 and the third ring member 7 are kept at a low level relative to a embodiment wherein the whole concave surface 34 of the first ring member 4 and the whole second concave surface 36 of the second ring member would be in contact with the third ring member 7. In the example of
The material of the first ring member, at least in the vicinity of the first concave surface 34, and of the second ring member, at least in the vicinity of the second concave surface 36, may comprise rubber or an elastomeric material selected from the group including but non-limited to acrylonitrile polymers including acrylonitrile-butadiene rubber (NBR) hydrogenated nitrile butadiene rubber (HNBR), carboxylated acrylonitrile butadiene, carboxylated hydrogenated acrylonitrile butadiene, ethylene propylene, ethylene propylene diene, fluoroelastomers, tetrafluoroethylene-propylene copolymers, fluorocarbons, perfluoroelastomers and the like, and mixtures thereof.
Advantageously, at least one of the said first ring member 4 and the second ring member 6 are made of one of the said elastomeric or rubber materials cited above and comprise one or more lubricant additives to provide enhanced properties of wear and friction reduction such as but non-limited to polytetrafluoroethylene, molybdenum disulfide, graphite flake, hexagonal boron nitride and the like, and mixture thereof.
In an embodiment of the present invention, at least one of the whole first ring member 4 and the whole second ring member 6 are made of rubber or elastomeric material as disclosed herein above, preferably including one or more lubricant additives as disclosed herein above.
In another embodiment of the present invention, at least one of the first ring member 4 and second ring member 6 comprise a reinforcing material 4b, 6b, located below the first concave surface 34 or second concave surface 36, for example embedded in the ring member as presented on
The said second ring member 6 comprises a contacting surface 6a in contact with the said rotatable member 3. It is preferred that the assembly is such that no rotation or slip occurs between the second ring member 6 and the rotatable member 3. This occurs when the friction force between the contacting surface 6a and the rotatable member is higher than the friction force between the second cavity surface 36 and the third ring member 7. In an embodiment of the invention as presented on
Preferably, said third ring member 7 is made of a material having a Young's module larger than 100 GPa. Preferred materials for said third ring member are selected from alloys or ceramics. More preferred materials must have good properties of stiffness, good chemical inertia, resistance to wear and to high temperatures. Advantageously, the third ring member should have a low cost of production. Those preferred materials include brass, bronze copper, beryllium bronze, 18-10 stainless steel, steel, and zirconium dioxide. These materials are not limitative to the present invention.
Preferably, the third ring member 7 is coated with a material minimizing friction between said third ring member 7 and both of said first ring member 4 and said second ring member 6. Advantageously, the coating material must provide a low friction coefficient on the first contacting surface 34 and the second contacting surface 36. Such a coating material must also have a good adhesion on the substrate, a good resistance to wear and to high temperatures. Preferred coating materials for the third ring member 7 includes PTFE (Polytetrafluoroethylene), PTFE/Molybdenum disulfide, PTFE/graphite, graphite and Molybdenum disulfide, Titanium carbide, chromide carbide and diamond like carbon. These materials are not limitative to the present invention.
Preferably, the third ring member 7 is toroidal. The first ring member 4 provides 2 surfaces of sealing 9a, 9c contacting the third ring member 7, and the second ring member 6 provide 2 surfaces of sealing 9b, 9d contacting the third ring member 7.
According to a second aspect, the present invention relates to a roller cone drill bit 100. An example of a perspective three dimensional view of a roller cone drill bit is represented in the
Each of the first concave surface 34 and second concave surface 36 have an orientation.
The seal assembly 1 of the roller cone drill bit 100 may comprises any other features as disclosed in the description of the seal assembly 1 herein above.
The roller cone 3 comprises hard material cutting inserts 3a, preferably made of tungsten carbide. Preferably, the roller cone 3 comprises a base 13 facing a substantially flat surface 12 of the bit leg 10. The base 13 of the roller cone 3 comprises a cavity designed for inserting a shaft or journal pin 2 rising from the substantially flat surface 12 of the bit leg 10 and for the bearing members and cone retention ball bearings 5. Both journal pin 2 and cavity of the roller cone 3 comprises complementary bearing races for cone retention ball bearings 5, radial bearings 22 and thrust bearing 24. The journal pin 2 further comprises a first channel 19 for introducing balls 5. The first channel 19 is closed by a ball retainer 23 fixed, typically by welding, inside the channel once the balls 5 are in place. More preferably, the journal pin 2 further comprises a second channel 20 connected to the first channel 19 and to a reservoir 18 containing a lubricant for lubrication of the bearing system 5, 22 and 24. The channel for the lubricant to enter the bearing is through the ball race. It is from that point that the lubricant is distributed throughout the bearing system. When lubricated, the space between the journal pin 2 and the cavity of the roller cone 3 is completely filled with lubricant. A third channel 21 may be provided in connection with one of the first or second channel and one of the radial bearings 22 or thrust bearings 24 for allowing the circulation of the lubricant.
The seal assembly is arranged in the roller cone drill bit such that said first ring member 4 and said second ring member 6 provide multiple sealing surfaces 9a, 9b, 9c, 9d contacting said third ring member 7 thus allowing the said third ring member 7 to rotate freely between the said first concave surface 34 and the second concave surface 36 and in self-alignment relative to the movement of the rotatable member 3.
Preferably, the journal pin 2 comprises a bottom section adjacent to the bit leg, the bottom section having a bigger diameter for making a press fit between that bottom section and the first ring member 4.
The said cavity of the roller cone comprises a recess or preferably a groove 11 having for example a rectangular cross section machined parallel to the base 13 of the roller cone for inserting said seal assembly.
The method of mounting the roller cone drill bit includes the steps of:
In another embodiment of the invention, as presented on
Preferably, the fourth ring member 16 comprises a cavity 17 at its periphery. More preferably, the cavity 17 of the fourth ring member 16 extends along the entire perimeter of the said fourth ring member 16. Larger particles of debris are trapped by this cavity and fluid flowing through this cavity tends to remove these particles out of the cavity and out of the space between the base of the roller cone and the flat surface of the body facing the base of the roller cone.
More preferably, fourth ring member 16 is made of a material having a Young's modulus larger than 100 GPa such as the possible materials disclosed hereinabove for the said third ring member.
Preferably, said fourth ring member 16 is coated with an abrasive resistant coating such as Titanium nitride, or aromatic polyamine (Kevlar). Said fourth ring member can also be carburized or boronized.
Preferably, the roller cone bearing surfaces are hardened, and journal surfaces are hardened typically by carburizing or boronizing the steel surfaces.
The seal assembly as disclosed herein above and its use for sealing a space formed by a journal and a cavity of a roller cone provides the advantages of an improved sealing and an increased lifetime of the sealing relative to prior art sealing means, in particular in the field of roller cone drill bits.
While drilling with a roller cone drill bit comprising the seal assembly as disclosed hereinabove, the relative speed of the sealing ring 7 that floats freely in the cavities formed by 34 and 36 will be typically less than the rotational speed of the cone, thus limiting the heat generation of the seal due to frictional forces. This improvement of this seal was not possible with other typical sealing system configurations.
The invention may also be described as follows:
The seal assembly 1 for sealing between a shaft 2 and a rotatable member 3 adapted for rotating around said shaft comprises:
| Number | Date | Country | Kind |
|---|---|---|---|
| 13194481.1 | Nov 2013 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2014/002575 | 11/26/2014 | WO | 00 |
