Earth boring bit lubricant chamber barrier member with dispersed fibers

Abstract

An earth boring bit has a body with a depending bearing pin. A cone mounts rotatably on the bearing pin, the cone having cutting elements on its exterior. A lubricant chamber supplies lubricant to the bearing surfaces between the bearing pin and the cone. A barrier in the lubricant chamber has one side exposed to the exterior of the bit for contact by drilling fluid. The barrier member is elastomeric and contains chopped organic polymer fibers. The barrier member may be a seal ring between the cone and bearing pin, or it may be a lubricant compensator.

Description

FIELD OF THE INVENTION

This invention relates in general to earth boring bits, having rotating cones, and in particular to barrier members such as seals for the lubricant system.

BACKGROUND OF THE INVENTION

An earth boring bit of the type concerned herein has a body with at least one bearing pin depending from it. Typically, there are three bearing pins, and a cone mounts rotatably to each of the bearing pins. The cones have cutting elements on the exterior that engage the earth formation as the bit body rotates. Drilling fluid pumped from the surface discharges out nozzles of the bit body and returns up the exterior of the drill string along with cuttings.

A lubricant system supplies lubricant to the clearances between the bearing pin and the cone. The lubricant system includes a cavity in the bit body that connects by passages to the clearances between the bearing pin and the cone cavity. Barrier members prevent entry of debris and cuttings into the lubricant.

One of the barrier members comprises a seal located between the bearing pin and cone cavity. The seal may be of a variety of types, including an O-ring seal or a metal face seal assembly. In the case of metal face seals, elastomeric energizing rings are employed to urge the metal face seals into contact with each other. In one type, the metal face seal assembly includes an elastomeric excluder ring that blocks drilling fluid from contact with the energizing ring.

Another barrier member comprises a pressure compensator diaphragm. The diaphragm is an elastomeric member located in the lubricant cavity. One side of the diaphragm is exposed to the exterior of the drill bit and the other side is in contact with the lubricant. The diaphragm reduces pressure differential between the exterior of the bit and the lubricant in the lubricant chamber.

The barrier members, being elastomeric and exposed to drilling fluid, are subject to being cut or torn by drilling cuttings. In the case of an O-ring seal serving as the barrier member, one side is in dynamic sliding contact, thus is subject to wear. If worn excessively, drilling fluid can enter. Tears or cuts on the barrier member can cause drilling fluid to enter. If the drilling fluid enters the lubricant chamber, the cuttings will damage the bearing surfaces, lubricant will leak out, and the life of the bit will soon be over.

One prior art approach to reducing wear on elastomeric seal surfaces of earth boring bits is to place a fabric of woven fibers on the side of the seal that is in dynamic sliding engagement. In applications other than earth boring bits, chopped fiber material has been dispersed in the rubber material of brake bands, clutch plates, and sheet gaskets. Also, chopped fiber material has been dispersed in adhesives and sealants to vary the viscosity of the material.

SUMMARY OF THE INVENTION

The bit of this invention is a rotating cone type having a lubricant chamber for supplying lubricant to bearing surfaces between the cone and a bearing pin. The lubricant chamber has at least one barrier with one side exposed to the exterior of the bit for contact by drilling fluid in the well bore. This barrier prevents entry of drilling fluid into the lubricant chamber. The barrier comprises an elastomeric compound containing non-woven, non-cellulose, fibers dispersed therein.

The barrier may comprise an O-ring seal deformed between an inner diameter portion of the cone and an outer diameter portion of the bearing pin. The barrier may comprise a pressure compensator diaphragm that flexes to reduce pressure differential between the drilling fluid in the well bore and the lubricant in the lubricant chamber. The barrier could also be an excluder ring or a metal seal assembly.

The chopped fibers are preferably formed from a polymer in the group consisting essentially of aromatic polyamide, non-aromatic polyamide, polyimide, polyurethane and polyester. The fibers are randomly oriented and uniformly dispersed throughout the material of the barrier. Preferably the volume of the fibers is less than 5% that of the elastomeric material of the barrier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a quarter sectional view of an earth boring bit constructed in accordance with this invention.

FIG. 2 is an enlarged sectional view of the bearing seal assembly of the bit of FIG. 1.

FIG. 3 is an enlarged sectional view of an alternate embodiment of a bearing seal assembly for an earth boring bit constructed in accordance with this invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, bit 11 has a body 13 with at least one bearing pin 15 that inclines outward and inward from body 13. Typically there are three bearing pins 15, and a cone 17 is rotatably mounted to each bearing pin 15. Each cone 17 has a plurality of cutting elements on its exterior, which may comprise tungsten carbide compacts 19 or steel teeth milled into the exterior of the cone.

Body 13 has a separate lubricant chamber for each of the bearing pins 15. Each lubricant chamber supplies lubricant to bearing surfaces of bearing pin 15 and cone 17. Each lubricant chamber includes a lubricant cavity 21 in body 13 and a plurality of passages 23 extending from cavity 21 to the exterior of bearing pin 15. Two elastomeric barriers prevent entry of drilling fluid on the exterior of bit 11 into the lubricant chamber. One of the barriers comprises a seal assembly 27 located at the base of bearing pin 15. The other barrier comprises a pressure compensator diaphragm 29 located in lubricant cavity 21.

Compensator diaphragm 29 has one side exposed to drilling fluid through a port 31 formed in body 13. The inner side of compensator diaphragm 29 is in contact with lubricant in lubricant cavity 21. Compensator diaphragm 29 flexes on the axis of lubricant cavity 21 to reduce pressure differential between the exterior drilling fluid pressure and the pressure of the lubricant in lubricant cavity 21. In this example, a rigid shell 33 in lubricant cavity 21 provides a stop against deformation of compensator diaphragm 29 when the lubricant is depleted. A cap 35 secures the opposite side of lubricant cavity 21. Compensator diaphragm 29 is formed of an elastomeric or rubber material, such as nitrile butadiene, or hydrogenated nitrile butadiene.

A variety of seal assemblies 27 exist for sealing between cone 17 and bearing pin 15. In the embodiment of FIG. 2, a rigid rotatable ring 37 is secured in cone cavity 25 for rotation with cone 17 and having an end face that comprises an annular seal surface. Rotating ring 37 is preferably a metal member, such as steel, and may have a harder metal coating such as diamond or the like on its end face. A non-rotating ring 39 is stationarily mounted around bearing pin 15. Non-rotating ring 39 is also a rigid member formed preferably of steel and having an end face that engages the seal surface on the end face of rotating ring 37. The end face of non-rotating ring 39 may also be coated with a harder material.

Seal assembly 27 includes an elastomeric or rubber energizer ring 41 deformed between a groove or seal gland 43 on the exterior of bearing pin 15 and an outer diameter portion 45 of non-rotating ring 39. The outer diameter 45 of non-rotating ring 39 is inclined so that a spring force caused by energizer ring 41 urges non-rotating ring 39 into sealing engagement with rotating ring 37. Seal assembly 27 may also include an elastomeric excluder ring 47, which is an elastomeric or rubber member, such as nitrile butadiene or hydrogenated nitrile butadiene, located between the outer end of non-rotating ring 39 and part of seal gland 43. Excluder 47 serves to prevent drilling fluid from contacting energizing ring 41.

Excluder 47 is formed of a rubber or elastomeric compound that contains a uniform disbursement of fibers 48. Fibers 48 are short randomly oriented non-cellulose members. Rather than a cellulose material, such as cotton, fibers 48 are formed of a material that is preferably a polymer from a group consisting essentially of aromatic polyamide, polyimide, non-aromatic polyamide, polyurethane and polyester. One preferred type of fiber 48 is an organic polymer fiber manufactured by DuPont with the trademark Kevlar. These fibers are formed from Kevlar yarn that is cut and refined to produce a short fibrillated fiber. DuPont offers product, referred to as Kevlar Engineer Elastomer, that comprises a Kevlar fiber pulp suitable for dispersion in rubber products. The amount of fibers 48 dispersed into the elastomeric compound of excluder 47 is small, preferably less than five percent by volume. The hardness of excluder 47 is preferably in the range from 40-50 Shore A.

Energizer ring 41 is not exposed to drilling fluid, thus in the preferred embodiment, it is of conventional elastomeric material and contains no chopped fibers 48. Compensator diaphragm 29, however, is exposed to drilling fluid, thus fibers 48 may be dispersed throughout the elastomeric material of diaphragm 29 of the same type and in the same proportion to those in excluder 47. Compensator diaphragm 29 may be formed of the same type of rubber material as excluder 47, but would typically have a hardness of about 75 Shore A.

The embodiment of FIG. 3 shows a different barrier member from that of FIGS. 1 and 2. In FIG. 3, bit body 49 has a plurality of bearing pins 51, each supporting a rotatable cone 53. Cone 53 has a cone cavity 55 and rotates on bearing pin 51. An O-ring seal 57 seals cone cavity 55 and has an exterior side in contact with the drilling fluid. O-ring seal 57 is squeezed between an exterior portion of bearing pin 51 and cone 53, thus one side of seal 57 is in sliding dynamic contact. O-ring seal 57 is a rubber or elastomeric compound having fibers 59 of the same type and in the same proportion as fibers 48. Preferably, the compound is a nitrile butadiene or hydrogenated nitrile butadiene material. The hardness is generally 70-90 Shore A.

The invention has significant advantages. The chopped dispersed fibers increase the wear resistance of the barrier members of earth boring bits that are engaged in dynamic contact. The fibers increase the resistance of the barrier members to tearing and cutting from drilling cuttings as well.

While the invention has been shown in only a few of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.

Claims

1. An earth boring bit, comprising:

a bit body having a threaded upper end for connection to a drill string and at least one depending bearing pin;

a cone mounted on the bearing pin for rolling engagement with a bottom of a well bore as the body rotates;

a lubricant chamber in the body and the bearing pin for containing a lubricant; and

a barrier in the lubricant chamber having one side exposed to the exterior of the bit for contact by drilling fluid in the well bore for preventing entry of drilling fluid into the lubricant chamber, the barrier comprising an elastomeric material containing non-woven, non-cellulose fibers dispersed therein.

2. The bit according to claim 1, wherein the barrier comprises a seal ring deformed between an inner diameter portion of the cone and an outer diameter portion of the bearing pin.

3. The bit according to claim 1, wherein the barrier comprises a pressure compensator diaphragm that flexes to reduce pressure differential between the drilling fluid in the well bore and the lubricant in the lubricant chamber.

4. The bit according to claim 1, wherein the bit has a seal assembly between the bearing pin and the cone comprising:

a rigid ring that engages an annular seal surface in dynamic sliding contact;

an elastomeric energizer ring that is deformed between an outer diameter portion of the bearing pin and the rigid ring to urge the rigid ring into contact with the annular seal surface, and wherein the barrier comprises:

an excluder ring deformed between a portion of the bearing pin and the rigid ring.

5. The bit according to claim 1, wherein the fibers are formed of a material from the group consisting essentially of aromatic polyamide, polyimide, non-aromatic polyamide, polyurethane and polyester.

6. The bit according to claim 1, wherein the fibers comprise less than five percent of the elastomeric material, by volume, of the barrier.

7. The bit according to claim 1, wherein the fibers are dispersed uniformly throughout the barrier.

8. The bit according to claim 1, wherein the fibers are randomly oriented in the barrier.

9. In an earth boring bit having at least one cone rotatably mounted to a bearing pin and a seal assembly located between the bearing pin and the cone, the seal assembly comprising:

a barrier ring formed of a rubber compound and having randomly oriented, uniformly dispersed chopped fibers therein, the fibers being formed of a material from the group consisting essentially of aromatic polyamide, polyimide, non-aromatic polyamide, polyurethane and polyester.

10. The bit according to claim 9, wherein the barrier ring comprises a seal ring having a surface in dynamic sliding contact as the cone rotates on the bearing pin.

11. The bit according to claim 9, wherein the seal assembly comprises:

a metal ring that has an end face in dynamic engagement with an annular seal surface;

an elastomeric energizer ring that urges the metal ring into engagement with the annular seal surface; and wherein the barrier ring comprises:

an excluder ring deformed against the metal ring and having one side exposed to the exterior of the bit.

12. The bit according to claim 9, wherein the barrier ring has a hardness in the range from 40-90 Shore A.

13. The bit according to claim 9, wherein the fibers comprises less than five percent of the volume of the barrier ring.

14. The bit according to claim 9, wherein the fibers are randomly oriented.

15. An earth boring bit, comprising:

a bit body having at least one bearing pin depending thereform;

a cone rotatably mounted on the bearing pin;

a lubricant chamber containing a lubricant and defined by a cavity in the bit body, clearances between the cone and the bearing pin, and a passage between the cavity and the clearances; and

a barrier that blocks drilling fluid surrounding the bit body from entry into the lubricant chamber, the barrier being a rubber compound containing chopped polymeric fibers randomly dispersed throughout the barrier.

16. The bit according to claim 15, wherein the polymeric fibers are formed from a material selected from the group consisting essentially of aromatic polyamide, polyimide, non-aromatic polyamide, polyurethane and polyester.

17. The bit according to claim 15, wherein the barrier comprises a seal ring deformed between an inner diameter portion of the cone and an outer diameter portion of the bearing pin.

18. The bit according to claim 15, wherein the barrier comprises a pressure compensator diaphragm that flexes to reduce pressure differential between the drilling fluid in the well and the lubricant in the lubricant chamber.

19. The bit according to claim 15, wherein the bit has a seal assembly between the bearing pin and the cone comprising:

a rigid ring that engages an annular seal surface;

an energizer ring that is deformed between an outer diameter portion of the bearing pin and the rigid ring to urge the rigid ring into contact with the annular seal surface, and wherein the barrier comprises:

an excluder ring deformed between a portion of the bearing pin and the rigid ring.