WO1999040291A1

WO1999040291A1 - Roller cone drill bit with improved thrust bearing assembly

Info

Publication number: WO1999040291A1
Application number: PCT/US1999/002103
Authority: WO
Inventors: Dennis D. Fuller
Original assignee: Dresser Industries, Inc.
Priority date: 1998-02-06
Filing date: 1999-02-02
Publication date: 1999-08-12
Also published as: AU2571699A

Abstract

A roller cone drill bit with an improved thrust bearing assembly is provided. The roller cone drill bit may have an air cooled bearing system or a sealed lubricant bearing system depending upon anticipated downhole drilling applications. The bearing assembly includes a first thrust bearing member located on a spindle extending from at least one support arm of the drill bit. The first thrust bearing member preferably has a removed sector or cutout portion located in alignment with a fluid passageway in the respective support arm and spindle. A second thrust bearing member is preferably located in opposition to the first thrust bearing member to carry axial, thrust loads imposed on the drill bit during downhole drilling operations. One or more slots, grooves or openings may be formed in a surface of one thrust bearing member disposed adjacent to the other thrust bearing member. The slots, grooves or openings may be configured to receive and hold lubricant and/or cooling fluid flowing from the fluid passageway through the removed sector.

Description

ROLLER CONE DRILL BIT WITH IMPROVED THRUST BEARING ASSEMBLY

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to roller cone drill bits and more particularly, a drill bit having an improved thrust bearing assembly.

BACKGROUND OF THE INVENTION

Various types of rotary drill bits may be used to form a borehole in the earth. Examples of such drill bits include roller cone drill bits or rotary cone drill bits used in drilling oil and gas wells and rock bits used in mining operations. A typical roller cone drill bit includes a bit body having an upper portion adapted for connection to a drill string. A plurality of support arms, typically two or three, depend from a lower portion of the bit body with each support arm having a spindle or journal protruding radially inward and downward with respect to a projected axis of rotation of the bit body.

A respective cutter cone assembly is generally rotatably mounted on each spindle or journal. Each cutter cone assembly typically has a cavity formed therein and sized to receive the respective spindle. Various types of bearings and/or bearing surfaces may be disposed or formed between the exterior of the spindle and the interior of the cavity. A typical bearing system used to rotatably mount a cutter cone assembly on a spindle will include one or more radial bearings and one or more thrust bearings. The radial bearings will generally be located between the outside diameter of the spindle and interior surfaces of the cavity disposed adjacently thereto. Thrust bearings and/or thrust bearing surfaces will generally be located between the end of each spindle opposite from the respective support arm and adjacent portions of the cavity formed in the respective cutter cone assembly. Various types of thrust bearings have been used to accommodate large axial, thrust loads imposed on cutter cone assemblies associated with roller cone drill bits. Components of such thrust bearings are often manufactured from steel alloys and/or tungsten carbide alloys associated with the manufacturer of rotary drill bits. For some roller cone drill bits, particularly rock bits used in mining operations, pressurized air may be directed through a drill string attached to the associated bit body and one or more fluid passageways formed in the bit body and support arms to cool the bearings associated with each spindle and cutter cone assembly. Air cooled drill bits may also be used in drilling oil and gas wells in addition to mining operations.

Some roller cone drill bits have a sealed lubricant system to cool and protect associated bearings and/or bearing surfaces. A lubricant reservoir is often provided to compensate for any partial loss of lubricant and to balance internal lubricant pressure with external hydrostatic pressure during downhole drilling operation. A typical lubricant may comprise, for example, a calcium complex grease. Additionally, solids, such as molybdenum disulfide, may be added to the lubricant to increase the load carrying capacity of the bearings and/or bearing surfaces. Bearings and bearing surfaces in a typical roller cone drill bit are heavily loaded during downhole drilling operations. During such drilling operations, the drill bit is rotated in a borehole which causes associate cutter cone assemblies to rotate on respective spindles. Such drill bits typically operate at relatively low speeds with heavy weight applied to each cutter cone assembly which produces a high load on the associated bearings. Roller cone drill bits with sealed lubrication systems typically include one or more elastomeric seals which may be damaged from exposure to high temperatures created by excessive friction due to such heavy loads. U.S. Patent 4,056,153 entitled Rotary Rock Bi t wi th Mul tiple Row Coverage for Very Hard Formations, and U.S. Patent 4,280,571 entitled Rock Bit, show examples of conventional rotary cone bits with cutter cone assemblies mounted on a spindle projecting from a support arm.

Hardfacing of metal surfaces and substrates is a well- known technique to minimize or prevent abrasion, erosion and wear of the metal surfaces or substrates. Hardfacing can be generally defined as applying a layer of hard, abrasion resistant material to a less resistant surface or substrate by plating, welding, spraying or other well known metal deposition techniques. Hardfacing is frequently used to extend the service life of drill bits and other downhole tools used in the oil and gas industry. Tungsten carbide and alloys are some of the more widely used hardfacing materials to protect drill bits and other downhole tools associated with drilling and producing oil and gas wells. U.S. Patent 2,339,161 issued on January 11, 1944 illustrates a roller cone drill bit having a thrust bearing which is backed up by a granular material so that the bearing can float when loads are imposed thereon. U.S. Patent 3,476,446 issued on November 4, 1969 illustrates a thrust button located in the cone for engaging the end of the cone support arm to accommodate thrust loads. U.S. Patent 4,194,794 issued on March 25, 1980 illustrates a two-part thrust bearing. One part is pressed into a recess formed in the end of the cone support arm and the second part is pressed into a recess in the cone adjacent to the first part. The two bearing parts are formed of dissimilar materials and one part is provided with a radially extending recessed area to permit cooling flow into the bearing and for providing a space to trap materials worn from the bearing.

U.S. Patent 5,642,942 issued on July 1, 1997 illustrates a roller cone drill bit having a two-part thrust bearing for accommodating axial thrust loads. This patent describes a two-part thrust bearing having each part constructed from a material of different hardness.

SUMMARY OF THE INVENTION

In accordance with teachings of the present invention, a roller cone drill bit having support arms with a spindle or journal extending from each support arm and a respective cutter cone assembly rotatably mounted on each journal is provided with an improved thrust bearing assembly.

Technical benefits of the present invention include providing a roller cone drill bit with a thrust bearing system having increased load carrying capability. A thrust bearing system incorporating teachings of the present invention may be used with existing support arm and cutter cone assemblies without substantially changing or modifying the overall configuration and dimension of the support arm and cutter cone assemblies. The present invention will often prolong downhole life of an associated roller cone drill bit by increasing the flow of lubricant and/or cooling fluid to components of the associated thrust bearing system. The downhole life of an associated roller cone drill bit may also be increased by forming one or more components of the thrust bearing system from various alloys of tungsten carbide and similar types of hard, abrasion resistant materials

For some applications, one or more components of a thrust bearing system may be coated with a layer of superhard materials such as coated diamond particles or coated cubic nitride particles to minimize or eliminate any abrasion, erosion and/or wear of the respective component. Also, one or more components of the thrust bearing system may be formed from a series of thin layers formed from hard, wear resistant materials, steel alloys, and/or non- ferrous alloys which have been laminated with each other.

One aspect of the present invention includes providing a roller cone drill bit with at least one thrust bearing assembly having a first component and a second component with the first component located on one end of a spindle which rotatably supports an associated cutter cone assembly. The second component of the thrust bearing assembly may be located in a cavity within the cutter cone assembly in opposition to the first component. The first component preferably includes a sector which has been entirely removed from a location adjacent to a fluid passageway formed in the associated support arm and spindle. The removed sector permits fluid flow around and between components of the thrust bearing assembly to provide relatively large amounts of fluid flow through the thrust bearing assembly for maximum cooling and/or lubrication. Further, the removed sector provides a relatively large space for accumulation and flushing of wear products from the thrust bearing assembly. For some applications, a first thrust bearing component having a removed sector formed in accordance with teachings of the present invention may have more total bearing surface area than previous thrust bearing components with approximately the same overall dimensions. Examples of such prior thrust bearing components include, but are not limited to, thrust members or thrust buttons with a fluid communication hole extending through the center thereof and relatively deep slots formed in the associated bearing surface extending from the hole to the periphery of the thrust member. Other prior thrust bearing components often include center fluid communication holes in combination with slots and/or flats formed on the periphery thereof. Another aspect of the present invention includes providing a roller cone drill bit with at least one thrust bearing assembly having a first component and a second component disposed between one end of a spindle and a cavity formed within a cutter cone assembly rotatably mounted on the spindle. Grooves and/or openings having either symmetrical or nonsymmetrical patterns may be formed in one or more surfaces of the first component and/or the second component. The grooves and/or openings are provided to accumulate lubricant and/or to accumulate wear products from the associated thrust bearing assembly.

Technical advantages of the present invention include maximizing the quantity of coolant, air or liquid, flowing through a drill bit and past associated bearing surfaces. High coolant flow generally promotes cooling, dispersion and consequently, longer bearing life. For some applications, forming a thrust bearing member with a removed sector in accordance with teachings of the present invention may more than double the air flow rate through portions of an associated air cooled drill bit. BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and advantages thereof, reference is now made to the following brief description, taken in conjunction with the accompanying drawings and detailed description, wherein like reference numerals represent like parts, in which:

FIGURE 1 is a schematic drawing in section and in elevation with portions broken away showing a segment of an air cooled roller cone drill bit having at least one support arm and a thrust bearing assembly incorporating teachings of the present invention;

FIGURE 2 is an enlarged schematic drawing in section and in elevation with portions broken away showing the thrust bearing assembly of FIGURE 1; FIGURE 3 is an enlarged schematic drawing in section and in elevation with portions broken away of the area generally defined by lines 3-3 of FIGURE 2;

FIGURE 4 is an enlarged schematic drawing in section and in elevation with portions broken away of the area generally defined by lines 4-4 of FIGURE 2;

FIGURE 5 is a schematic drawing in section showing an alternative embodiment of a first thrust bearing component satisfactory for use with the thrust bearing assembly of FIGURE 2; FIGURE 6 is a schematic drawing in section showing an alternative embodiment of a second thrust bearing component satisfactory for use with the thrust bearing assembly of FIGURE 2;

FIGURE 7 is a schematic drawing in section and in elevation with portions broken away showing a segment of a roller cone drill bit having at least one support arm with a sealed lubrication system and a thrust bearing assembly incorporating teachings of the present invention; FIGURE 8 is a schematic drawing in section and in elevation with portions broken away showing an alternative embodiment of a bearing component which may be satisfactorily used as part of a thrust bearing system incorporating teachings of the present invention; and

FIGURES 9A-9D are schematic drawings showing plan views of further embodiments of bearing components which may be satisfactorily used as part of a thrust bearing system incorporating teachings of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention and its advantages are best understood by referring in more detail to FIGURES 1-9D of the drawings. Roller cone drill bits 20 and 120 which will be discussed later in more detail represent only a few examples of the many types of drill bits which may have a thrust bearing assembly incorporating teachings of the present invention. Thrust bearing systems and assemblies incorporating teachings of the present invention may be used with a wide variety of roller cone drill bits, rotary cone drill bits and rotary rock bits. Such thrust bearing systems and assemblies may be satisfactorily used with air cooled drill bits, drill bits having a sealed lubrication system and drill bits which do not have a lubrication system or cooling system.

Conventional roller cone drill bits are typically constructed from two or more segments. The segments may be positioned together longitudinally with a welding groove between each segment. The segments may then be welded with each other using conventional techniques to form a bit body. Each segment generally includes an associated support arm extending from the bit body. An enlarged cavity or passageway is typically formed in the bit body to receive drilling fluids from a drill string attached to the bit body. U.S. Patent 4,054,772 entitled Posi tioning System for Rock Bit Welding shows a method and apparatus for constructing a three-cone rotary rock bit from three individual segments.

Drill bits 20 and 120 will be generally described as conventional roller cone drill bits formed from two or more individual segments. However, the present invention may also be satisfactorily used with a drill bit having a one piece or unitary bit body (not expressly shown) . Examples of such drill bits and their associated bit bodies, support arms and cutter cone assemblies are shown in U.S. Patent 5,439,067 entitled Rock Bi t Wi th Enhanced Fluid Return Area, and U.S. Patent 5,439,068 entitled Modular Rotary Drill Bi t . These patents provide additional information concerning the manufacture and assembly of unitary bit bodies, support arms and cutter cone assemblies which may incorporate teachings of the present invention.

FIGURE 1 illustrates various aspects of a roller cone drill bit indicated generally at 20 incorporating various teachings of the present invention. Drill bit 20 may be described as an air cooled drill bit used to form a borehole in the earth. Drill bit 20 may also be referred to as a roller cone drill bit, a rotary cone drill bit or a rotary rock bit.

Drill bit 20 will typically include either two or three segments which may be welded with each other to form bit body 22 with enlarged cavity 24 disposed therein. Each segment typically includes a respective support arm 40 which extends from bit body 22. A respective spindle 42 is generally formed on each support arm 40 extending inwardly therefrom.

A respective roller cone or cutter cone assembly 80 is rotatably mounted on each spindle 42. Cutter cone assembly 10

80 may also be referred to as a "rotary cone cutter, " or a "roller cone cutter." Many rotary cone drill bits have two or three support arms and respective cutter cone assemblies . Bit body 22 includes upper portion 26 having threaded connection or pin 28 for use in securing drill bit 20 with the lower end of a drill string (not expressly shown) . Drill bit 20 may be attached to a drill string and disposed within a borehole (not expressly shown) . An annulus (not expressly shown) is formed between the exterior of the drill string and the inside diameter or sidewall of the borehole. In addition to rotating drill bit 20, the drill string may also be used as a conduit to communicate drilling fluids and other fluids from the well surface (not expressly shown) to drill bit 20 at the bottom of a borehole.

Drill bit 20 includes a cutting structure defined in part by cutter cone assemblies 80 and protruding inserts 82 which may scrape, gouge or crash against the sides and bottom of a borehole in response to weight and rotation applied to drill bit 20 from a drill string. The position of inserts 82 within each cutter cone assembly 80 may be varied to provide the desired down hole drilling or cutting action. Other types of cutter cone assemblies and cutting structures may be satisfactorily used with the present invention including, but not limited to, cutter cone assemblies having milled teeth (not expressly shown) instead of inserts 82. Each support arm 40 and associated cutter cone assembly 80 are substantially identical. Therefore, only one support arm 40 and cutter cone assembly 80 will be described in detail.

Cutter cone assembly 80 as shown in FIGURES 1 and 2 is rotatably mounted on spindle 42 of support arm 40 by ball bearings 44, roller bearings 46, and thrust bearing 11

assembly 60. Each cutter cone assembly 80 generally includes an opening with a cavity extending therefrom and sized to receive the associated spindle 42. Opening 48 is typically formed in exterior surface 38 of each support arm 40 with ball retainer passageway 36 extending therefrom. Ball bearings 44 may be inserted through ball retainer passageway 36 to secure each cutter cone assembly 80 on its respective spindle 42. Ball retainer plug 34 may then be inserted into respective ball retainer passageway 36. Ball plug weld 32 may then be formed in opening 48 to secure ball retainer plug 34 within respective ball retainer passageway 36.

Bit body 22 preferably includes a number of first fluid passageways 30 extending respectively from enlarge cavity 24 through each support arm 40 to an associated ball retainer passageway 36. Second fluid passageway 52 is preferably formed in each journal 42 extending from the associated ball retainer passageway 36 to a position immediately adjacently to thrust bearing assembly 60. For the embodiment of the present invention as shown in FIGURES 1 and 2, relatively high pressure air may be supplied from the well surface through a drill string attached to bit body 22 to enlarged fluid cavity 24. From enlarged fluid cavity 24, the high pressure air may flow through first fluid passageway 30, ball retainer passageway 36 and second fluid passageway 52 to cool thrust bearing assembly 60.

One or more vent slots (not expressly shown) may be formed in cutter cone assembly 80 to allow fluid flow therethrough. Various types of fluids in addition to air may be supplied to thrust bearing assembly 60 depending upon specific downhole drilling conditions. Also, one or more fluid passageways (not expressly shown) may be formed in spindle 42 to directly communicate fluids from first 12

fluid passageway 30 to a location adjacent to thrust bearing assembly 60. Such multiple fluid passageways may be particularly advantageous for supplying air to cool rotary cone rock bits used in mining operations. For the embodiment of the present invention as shown in FIGURES 1 through 4, thrust bearing assembly 60 preferably includes first thrust bearing member 61 and second thrust bearing member 62. First thrust bearing member 61 and second thrust bearing member 62 may sometimes be referred to as "thrust buttons." First thrust bearing member 61 is preferably disposed within end 50 of journal 42 opposite from support arm 40. Second thrust bearing member 62 is preferably disposed within cutter cone assembly 80 opposite from first thrust bearing member 61. First thrust bearing member 61 and second thrust bearing member 62 have generally circular, disk shaped configurations as best shown in FIGURES 3 and 4. Generally, circular opening 54 having dimensions corresponding approximately with the exterior of first thrust bearing member 61 is preferably formed in end 50 of journal 42. A corresponding generally circular opening 84 is preferably formed within cutter cone assembly 80 with dimensions corresponding approximately with the exterior of second thrust bearing member 62. First thrust bearing member 61 is preferably pressed into recess or opening 54 formed in end 50 of journal 42. Second thrust bearing member 62 is preferably pressed into recess or opening 84 formed within cutter cone assembly 80. When cutter cone assembly 80 is rotatably mounted on journal 42, bearing surface 63 of first thrust bearing member 61 will preferably be disposed immediately adjacently to and in close contact with bearing surface 64 of second thrust bearing member 62. First thrust bearing member 61 and second thrust bearing member 62 are located 13

in opposition to each other to absorb axial, thrust loads between cutter cone assembly 80 and end 50 of spindle 42.

For some applications, the outer periphery of first thrust bearing member 61 preferably includes a plurality of splines or knurls 65. Second thrust bearing member 62 may also include a plurality of splines or knurls 66 formed on the outer periphery thereof. Various types of serrations, knurls, upsets and/or grooves may be formed on the periphery of bearing members 61 and 62. The present invention is not limited to only splines 65 and 66.

The dimensions and configuration of splines 65 and 66 are preferably selected to assist in locking first bearing member 61 in recess or opening 54 and second bearing member 62 in recess or opening 84. Splines or knurls 65 and 66 increase the area of contact to prevent undesired rotation of first bearing member 61 relative to spindle 42 and rotation of second bearing member 62 relative to cutter cone assembly 80. Rotation of first bearing member 61 could possibly result in obstruction or closing of associated second fluid passageway 52.

For some applications, the periphery of first thrust bearing member 61 and second thrust bearing member 62 and respective recesses 54 and 84 may have generally polygon configurations (not expressly shown) rather than circular configurations. Forming thrust bearing members 61 and 62 and respective recesses 54 and 84 with generally matching polygon configurations may be used to prevent undesired rotation of first thrust bearing members 61 relative to and 50 of spindle 42 and second thrust bearing member 62 relative to cutter cone assembly 80.

First bearing member 61 has a rather generous sector 68 removed to expose second fluid passageway 52. Sector 68 extends through the entire thickness of first bearing member 61 as shown in FIGURES 2 and 3. 14

Angle "A" between the sides of removed sector 68 may vary between fifteen degrees (15°) and one hundred and eighty degrees (180°) depending upon the type of fluid and desired fluid flow rate for satisfactory cooling and/or lubrication of the associated thrust bearing assembly 60. For some air cooled rotary rock bits, angle "A" may be approximately one hundred and twenty degrees (120°) .

For the embodiment of the present invention as shown in FIGURES 1 and 2, second thrust bearing member 62 preferably has a generally circular disk shaped configuration corresponding approximately with first thrust bearing member 61 except the thickness of first thrust bearing member 61 is substantially larger than the thickness of second thrust bearing member 62. However, for some applications, first thrust bearing member 61 and second thrust bearing member 62 may have approximately the same thickness or second thrust bearing member 62 may have a thickness greater than first thrust bearing member 61.

For the embodiment of the present invention as shown in FIGURES 2, 3 and 4, bearing surface 63 of first bearing member 61 and bearing surface 64 of second thrust bearing member 62 are relatively smooth with no holes and/or grooves formed therein. The present invention allows selecting the dimensions associated with removed sector 68 including angle "A" to optimize the total area of contact between first thrust bearing member 61 and second thrust bearing member 62 while at the same time allowing the desired fluid flow rate through second fluid passageway 52. The cross sectional strength of first thrust bearing member 61 and second thrust bearing member 62 may be increased by eliminating any holes and/or grooves in respective bearing surfaces 63 and 64.

Second fluid passageway 52 is preferably formed in a portion of spindle 42 to maximize the distance between 15

second fluid passageway 52 and the bottom of a borehole formed by drill bit 20. As a result, removed sector 68 will also be disposed at a location which is subject to less axial or thrust loading from second thrust bearing member 62. The relationship between second fluid passageway 52, first thrust bearing member 61, and second thrust bearing member 62 and cutter cone assembly 80 as shown in FIGURES 1 and 2 minimizes any reduction in strength of first thrust bearing member 61 resulting from the removal of sector 68. This configuration also allows relatively unrestricted fluid flow from second fluid passageway 52 through removed sector 68 and to directly contact adjacent portions of bearing surface 64 of second thrust bearing member 62. Removed sector 68 also allows fluid exiting from second fluid passageway 52 to clean any wear material and/or other debris which may be disposed between bearing surfaces 63 and 64.

First thrust bearing member 61 and second thrust bearing member 62 of thrust bearing assembly 60 may often be formed from different materials. For some applications, first thrust bearing member 61 is preferably formed from harder material than second thrust bearing member 62. For example, first thrust bearing member 61 may be formed from sintered tungsten carbide while second thrust bearing member 62 may be formed from mild steel alloys typically associated with rotary cone drill bits. For some applications, first thrust bearing member 61 may have a hardness of approximately eighty (80) to ninety-five (95) on the Rockwell "A" scale. For purposes of the present application the term tungsten carbide includes monotungsten carbide (WC) , ditungsten carbide (W₂C) ; macrocrystalline tungsten carbide and cemented or sintered tungsten carbide. Sintered tungsten carbide is typically formed from a mixture of 1 6

tungsten carbide and cobalt powders by pressing the powder mixture to form a green compact. Various cobalt alloy powders may also be included. The green compact is typically sintered at temperatures near the melting point of cobalt to form dense sintered tungsten carbide.

For other applications, first thrust bearing member 61 and second thrust bearing member 62 may both be formed from various types of hard, wear resistant materials such as alloys of tungsten carbide and/or cobalt. First thrust bearing member 61 and second thrust bearing member 62 may also be formed from various steel alloys and non ferrous alloys satisfactory for use with drill bit 20 and 100. Examples of such steel alloys include, but are not limited to, M2 tool steel, S2 tool steel, high carbon steel, Hadfield manganese steel, stainless steel and silver infiltrated steel powder metallurgy. Examples of nonferrous alloys satisfactory for use in forming first thrust bearing member 61 and/or second thrust bearing member 62 include, but are not limited to, sintered tungsten carbide, silver infiltrated steel powder metallurgy, beryllium copper and tungsten carbide composite. A wide variety of cermets, both ferrous and non-ferrous, may be used to form thrust bearing members 61 and 62. FIGURE 5 is a schematic drawing showing first thrust bearing member 61a incorporating an alternative embodiment of the present invention. FIGURE 6 is a schematic drawing showing second thrust bearing member 62a incorporating an alternative embodiment of the present invention. For some applications, first thrust bearing member 61a and second thrust bearing member 62a may have dimensions and configurations as previously described for first thrust bearing member 61 and second thrust member 62. However, first thrust bearing member 61a may also be formed as a 17

generally solid disk without including removed sector 68. This configuration for first thrust bearing member 61a may be appropriate for drill bits which do not include cooling fluid and/or lubricating fluid for the associated thrust bearing assembly.

First thrust bearing member 61a and second thrust bearing member 62a preferably include respective substrates 71 and 72 with layer 74 of hardfacing material disposed on each substrate 71 and 72. Since machining hard, wear resistant material is both difficult and expensive, it is common practice to form a metal part such as substrates 71 and 72 with desired dimensions and configurations and subsequently treat selected surfaces by directly hardening the metal part (carborizing and nitrating) or by applying a layer of hardfacing material to selected surfaces depending upon the amount of wear-resistance desired. For those applications in which resistance to extreme wear of adjacent bearing surfaces is required, layer 74 of hard, wear-resistant material may be formed in accordance with teachings of the present invention on respective substrates 71 and/or 72.

Substrates 71 and 72 may be formed from a wide variety of metal alloys having desirable metallurgical characteristics such as machinability, toughness, heat treatability and corrosion resistance. For example, substrates 71 and 72 may be formed from various steel alloys and non ferrous alloys associated with the manufacture of drill bits 20 and 120.

Metallic matrix deposit or hardfacing layer 74 may include a wide variety of hard, abrasion and wear resistant materials and particles. Examples of such hard particles include coated particles or pellets, cubic boron nitride particles and/or tungsten carbide particles. The hard materials and/or hard particles used to form layer 74 provide abrasion and wear resistance. Layer 74 may include a plurality of hard particles embedded or encapsulated in various materials including cobalt, copper, nickel, iron ancf alloys thereof. For purposes of the present application, the term

"metallic matrix deposit" is used to refer to a layer of hardfacing which has been applied to substrates 71 and 72 to protect substrates 71 and 72 from abrasion, erosion and/or wear. Various binders such as cobalt, nickel, copper, iron and alloys thereof may be used to form the matrix portion or binder matrix of the deposit. Various metal alloys and cermets such as metal borides, metal carbides, metal oxides and metal nitrides may be included as part of the metallic matrix deposit in accordance with teachings of the present invention. Some of the more beneficial metal alloys and cermets will be discussed later in more detail. Metallic matrix deposit or layer 74 may be formed from sinterable materials including various metal alloys and cermets such as metal borides, metal carbides, metal oxides and metal nitrides.

Layer 74 may include tungsten carbide particles, coated diamond particles, coated cubic boron nitride particles, cobalt, nickle, copper, tungsten, tungsten carbide and alloys of these materials. For some applications, tungsten nitride, tungsten oxides, carbon borides, carbides, nitrides, suicides, niobium, vanadium, molybdenum, silicon, titanium, tantalum, yttrium, zirconium, chromium, boron, carbon nitrides and mixtures of these materials may be used to form layers 74. Additional information concerning various types of hardfacing materials and metal alloys satisfactory for forming first thrust bearing member 61a and second thrust bearing member 62a may be found in U.S. Patent 5,755,299 entitled Hardfacing Wi th Coded Diamond Particles . 19

FIGURE 7 shows various aspects of a roller cone drill bit indicated generally at 120 incorporating various teachings of the present invention. Drill bit 120 includes a sealed lubrication system which will be discussed later in more detail. Drill bit 120 is representative of drill bits associated with drilling oil and gas wells.

Drill bit 120 will typically include either two or three segments which have been welded with each other to form bit body 122 with enlarged cavity 24 disposed therein. Each segment typically includes a respective support arm 140 which extends from bit body 122. A respective spindle 42 is generally formed on each support arm 140 extending inwardly therefrom. A respective cutter cone assembly 80 may be rotatably mounted on each spindle 42 as previously described with respect to drill bit 20. Bit body 122 also includes upper portion 26 and threaded connection 28 for use in securing drill bit 120 with the lower end of a drill string (not expressly shown) .

During the manufacture and assembly of drill bit 120, respective first thrust bearing members 61 are preferably pressed into openings or recesses 54 formed in end 50 of each spindle 42. As previously described with respect to drill bit 20, respective second thrust bearing members 62 are preferably pressed into opening or recess 84 in each cutter cone assembly 80. Corresponding splines may be formed on the periphery of first thrust bearing member 61 and second thrust bearing member 62 to engage corresponding splines formed in respective openings or recesses 54 and 84. For some applications, respective knurled surfaces may be formed on the periphery of first thrust bearing member 61 and second thrust bearing member 62 to prevent rotation within respective recesses 54 and 84.

For the embodiment of the present invention as shown in FIGURE 7, each support arm 140 preferably includes 20

lubricant chamber 124. Lubricant passageway 126 is formed in each support arm 140 extending between lubricant chamber 124 and the associated ball retainer passageway 36. Lubricant reservoir and diaphragm assembly 128 is preferably disposed within lubricant chamber 124 to compensate for any differences in fluid pressure between the exterior of drill bit 120 and the associated lubrication system.

Elastomeric seal 130 is preferably disposed within each cutter cone assembly 80 adjacent to respective spindle 42 to retain lubricant within the cavity formed in cutter assembly 80. The lubricant is used to protect ball bearings 44, bushing 146 and thrust bearing assembly 60. Elastomeric seal 130 also prevents debris and other deleterious materials from entering into cutter cone assembly 80 and causing premature failure of one or more of the associated bearing components.

Lubricant chamber 124 and lubricant reservoir 128 are preferably filled with grease or other suitable fluid depending upon anticipated downhole drilling conditions to lubricate associated ball bearings 44, bushing 146 and thrust bearing assembly 60. First thrust bearing member 61 is preferably disposed within end 50 of spindle 42 with removed sector 68 aligned with second fluid passageway 52. Removed sector 68 provides a relatively large space to permit lubricant and/or cooling fluid flow to thrust bearing assembly 60 and to accumulate any wear products or wear material from thrust bearing assembly 60. Lubricant and/or cooling fluid preferably flows directly from second fluid passageway 52 through removed sector 68 and onto adjacent portions of bearing surface 64 of second thrust bearing member 62.

Second thrust bearing member 162 incorporating an alternative embodiment of the present invention is shown in 21

FIGURE 8. Second thrust bearing member 162 may be satisfactorily used with previously described first thrust bearing member 61 to form thrust bearing assembly 60. Second thrust bearing member 162 preferably includes slot 166 which extends diametrically across bearing surface 164 of second thrust bearing member 162. As a result, slot 166 will be disposed adjacent to bearing surface 63 of first thrust bearing member 61. The depth of slot 166 may be varied depending upon the type of lubricant and/or cooling fluid supplied to thrust bearing assembly 60 and the intended downhole application for the associated drill bit. Slot 166 provides a source of lubricant for bearing surface 63 and bearing surface 164 as first thrust bearing member 61 and second thrust bearing member 162 rotate relative to each other. Slot 166 may also be used to accumulate erosion and/or wear products from bearing surfaces 63 and 164.

Second thrust bearing members 162a, 162b, 162c and 162d incorporating further embodiments of the present invention are shown in FIGURES 9A, 9B, 9C and 9D. Second thrust bearing members 162a, 162b, 162c and 162d may be satisfactorily used with previously described first thrust bearing member 61 to form thrust bearing assembly 60.

For the embodiment of the present invention as shown in FIGURE 9A, second thrust bearing member 162a includes a pair of slots 166a which have been formed in bearing surface 164a. Slots 166a extend generally parallel with each other and radially offset from the center of bearing surface 164a. For the embodiment of the present invention as shown in FIGURE 9B, second thrust bearing member 162b includes a plurality of slots 166b formed in bearing surface 164b. Slots 166b extend radially from the approximate- center of second thrust bearing member 162b. The number and depth of 22

slots 166b may be varied depending upon the type of lubricant and/or cooling fluid supplied to thrust bearing assembly 60 and the intended downhole drilling application for associated drill bit. Second thrust bearing member 162c as shown in FIGURE

9C preferably includes a plurality of openings 166c formed in bearing surface 164c. The number and the depth of openings 166c may be varied depending upon the type of lubricant and/or cooling fluid supplied to the associated thrust bearing assembly and the anticipated downhole drilling application for the associated drill bit. Openings 166c may be formed in a generally symmetrical pattern as shown in FIGURE 9C or openings 166c may have an asymmetrical pattern (not expressly shown) as desired for the associated thrust bearing assembly and drill bit.

Second thrust bearing member 162d as shown in FIGURE 9D includes slot 166d which extends from approximately the center of bearing surface 164d to the periphery of second thrust bearing member 162d. Various configurations of slots and/or openings may be formed in respective bearing surfaces of either a first thrust bearing member or a second thrust bearing member to provide desired lubricant and/or cooling fluid for the associated thrust bearing system. The present invention is not limited to the configuration of slots and/or openings as shown in FIGURES 8 and 9A through 9D.

For some applications, additional thrust bearing components and/or thrust bearing surfaces may be disposed between shoulder 76 on the exterior of spindle 42 and shoulder 86 formed on the interior of cutter cone assembly 80. See FIGURE 2 and FIGURE 7. A thrust bearing system incorporating teachings of the present invention is not limited to only thrust bearing assembly 60. 23

From the foregoing, it will be appreciated that a thrust bearing system incorporating teachings of the present invention provides many advantages over prior thrust bearing systems. Drill bits incorporating teachings of the present invention will carry thrust loads more efficiently and effectively and increase bit life compared to prior thrust bearing assemblies and systems.

Although the present invention has been described with several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompasses such changes and modifications as fall within the scope of the present appended claims.

Claims

24WHAT IS CLAIMED IS:

1. A roller cone drill bit comprising: a bit body having at least one support arm extending therefrom; a cutter cone assembly rotatably mounted on each support arm; at least one fluid passageway formed in and extending through each support arm to a location adjacent to the associated cutter cone assembly; a first thrust bearing member disposed within a portion of each support arm adjacent to the fluid passageway; each first thrust bearing member having a removed sector aligned with the associated fluid passageway; and a second thrust bearing member disposed within each cutter cone assembly adjacent to and aligned with the respective first thrust bearing member to receive fluid flowing through the associated fluid passageway and the removed sector of the respective first thrust bearing member.

2. The drill bit of Claim 1 further comprising each first thrust bearing member having a periphery with a plurality of splines formed thereon for engagement with portions of the support arm to maintain alignment between the removed sector and the associated fluid passageway.

3. The drill bit of Claim 1 further comprising each first thrust bearing member having a periphery with means formed thereon for engagement with portions of the support arm to maintain alignment between the removed sector and the associated fluid passageway-. 25

4. The drill bit of Claim 1 further comprising each first thrust bearing member formed from material harder than the material used to form the second thrust bearing member.

5. The drill bit of Claim 1 further comprising each second thrust bearing member having a periphery with a plurality of splines formed thereon for engagement with portions of the cutter cone.

6. The drill bit of Claim 1 further comprising each second thrust bearing member having a periphery with means formed thereon for engagement with portions of the cutter cone .

7. The drill bit of Claim 1 further comprising the first thrust bearing member and associated second thrust bearing member cooperating with each other to extend the downhole drilling life of the drill bit.

8. The drill bit of Claim 1 further comprising: the first thrust bearing member having a generally circular, disk-shaped configuration; and the second thrust bearing member having a generally circular, disk-shaped configuration corresponding with the first thrust bearing member.

9. The drill bit of Claim 1 wherein the removed sector of each first thrust bearing member allows removal of wear products resulting from contact between the first thrust bearing member and the associated second thrust bearing member. 26

10. The drill bit of Claim 1 further comprising: each first thrust bearing member having a periphery with a plurality of serrations formed therein; each second thrust bearing member having a periphery with a plurality of serrations formed therein; and the respective serrations preventing rotation of the first thrust bearing member relative to the respective support arm each second thrust bearing member relative to the respective cutter cone assembly.

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11. A thrust bearing assembly for use in a drill bit comprising: a first thrust bearing member having a thickness and generally circular configuration; the first thrust bearing member disposed adjacent to a fluid passageway; a sector extending through the thickness of the first thrust bearing member and removed therefrom; and the second thrust bearing member having a generally circular configuration disposed adjacent to the first thrust bearing member.

12. The thrust bearing assembly of Claim 11 wherein the second thrust bearing member further comprises: a surface disposed adjacent to the first thrust bearing member; and at least one slot formed in the surface of the second thrust bearing member to receive fluid from the sector in the first thrust bearing member.

13. The thrust bearing assembly of Claim 12 wherein the second thrust bearing member further comprises the slot extending substantially along a diameter of the second thrust bearing member.

14. The thrust bearing assembly of Claim 12 further comprising the slot extending partially along a diameter of the second thrust bearing member.

15. The thrust bearing assembly of Claim 12 wherein the second thrust bearing member further comprises a plurality of slots formed in the surface of the second thrust bearing member disposed adjacent to the first thrust bearing member. 28

16. The thrust bearing assembly of Claim 11 wherein the second thrust bearing member further comprises: a surface disposed adjacent to the first thrust bearing member; and at least one opening formed in the surface of the second thrust bearing member to receive fluid from the sector in the first thrust bearing member.

17. The thrust bearing assembly of Claim 16 wherein the second thrust bearing member further comprises a plurality of openings formed in the surface disposed adjacent to the first thrust bearing member.

18. The thrust bearing assembly of Claim 11 further comprising the openings arranged in a generally symmetrical pattern on the surface of the second thrust bearing member disposed adjacent to the first thrust bearing member.

19. The thrust bearing assembly of Claim 17 wherein the openings are disposed in a nonsymmetrical pattern on the surface of the second thrust bearing member disposed adjacent to the first thrust bearing member.

20. The thrust bearing assembly of Claim 11 wherein the first thrust bearing member comprises tungsten carbide.

21. The thrust bearing assembly of Claim 11 wherein at least one of the thrust bearing members further comprises a substrate and a layer of hardfacing material formed on one side of the substrate adjacent to another bearing member.

22. The thrust bearing assembly of Claim 21 wherein the substrate comprises a ferrous material. 29

23. The thrust bearing assembly of Claim 21 wherein the substrate comprises a non ferrous material.

24. The thrust bearing assembly of Claim 11 wherein the first thrust bearing member further comprises resistant material having a hardness between approximately eighty

(80) and ninety (90) on the Rockwell "A" scale.

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25. A rotary cone drill bit for forming a borehole in the earth comprising: a bit body having an upper portion adapted for connection to a drill string from rotation of the drill bit; a number of support arms extending from the bit body; a spindle disposed on each support arm and extending inwardly therefrom; a number of cutter cone assemblies equal to the number of support arms with each cutter cone assembly rotatably mounted on one of the spindles; at least one fluid passageway formed in and extending through each support arm and respective spindle to a location adjacent to the associated cutter cone assembly; a first thrust bearing member disposed within one end of each spindle adjacent to the fluid passageway; each first thrust bearing member having a removed sector aligned with the associated fluid passageway; and a second thrust bearing member disposed within the associated cutter cone assembly adjacent to and aligned with the respective first thrust bearing member to receive fluid flowing through the associated fluid passageway and the removed sector of the respective first thrust bearing member .

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26. The drill bit of claim 25 further comprising: each support arm having a lubricant reservoir disposed therein; the associated fluid passageway extending from the lubricant reservoir to the one end of the respective spindle; the removed sector in the respective first thrust bearing assembly aligned with the fluid passageway to allow communication of lubricant between the lubricant reservoir and the associated second thrust bearing member.

27. The drill bit of Claim 25 further comprising: the bit body having an enlarged cavity formed therein to receive fluid from the drill sting; each fluid passageway extending from the enlarged cavity in the bit body through the respective support arm to the one end of the respective spindle; the removed sector of the respective first thrust bearing member aligned with the fluid passageway to allow cooling fluid to flow from the enlarged cavity through the fluid passageway to the associated second thrust bearing member.

28. The drill bit of Claim 25 wherein the cooling fluid comprises air.