Title:
Rotary rock bit with wiper pad lubrication system
United States Patent 3890018


Abstract:
A system is provided for circulating lubricant into the loaded contact area between the bearing pin and the rotating cutter of an earth boring bit. The cutter is mounted to rotate about the bearing pin. The cutter includes a cutter interior surface. At least one wiper pad cavity is located in the aforementioned interior surface of the cutter. A wiper pad is positioned in the wiper pad cavity and a resilient member is positioned beneath the wiper pad. As the cutter rotates, the wiper pad forces lubricant into the load area between the bearing pin and the interior surface of the cutter.



Inventors:
CLAMON ROBERT DALE
Application Number:
05/489857
Publication Date:
06/17/1975
Filing Date:
07/19/1974
Assignee:
DRESSER INDUSTRIES, INC.
Primary Class:
Other Classes:
384/137
International Classes:
E21B10/24; F16C33/10; (IPC1-7): F16C33/66
Field of Search:
308/8.2,78,101,240 175
View Patent Images:



Primary Examiner:
Wood Jr., Henson M.
Assistant Examiner:
Church, Gene A.
Attorney, Agent or Firm:
Scott, Eddie E.
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows

1. A rotary rock bit comprising:

2. The rotary rock bit of claim 1 including resilient means positioned within said wiper pad cavity for providing a force tending to push said wiper pad out of said wiper pad cavity.

3. The rotary rock bit of claim 2 including seal means between said bit body and said rotatable cutter for providing a seal between said rotatable cutter and said bit body.

4. A rotary rock bit comprising:

5. The rotary rock bit of claim 4 including resilient means positioned in said groove for urging said wiper pad out of said groove.

6. A rotary rock bit comprising:

Description:
BACKGROUND OF THE INVENTION

The present invention relates to the art of earth boring and more particularly to a system for lubricating the bearings between the rotatable cutter and the bearing shaft of a rotary rock bit.

A rotary rock bit in general consists of a main bit body adapted to be connected to a rotary drill string. The bit includes at least one rotatable cutter mounted upon a bearing shaft extending from the main bit body with bearing systems between the cutter and the bearing shaft for promoting rotation of the cutter. Inserts or steel teeth on the surface of the cutter disintegrate the formations as the bit and cutter rotate and a seal between the cutter and the bearing shaft retains lubricant in the bearing area and prevents borehole fluids and debris from entering the bearing area.

The rotary rock bit must operate under very severe environmental conditions and the geometry of the bit is restricted by the operating characteristics. At the same time, the economies of petroleum production demand a longer lifetime and improved performance from the bit. In attempting to provide an improved bit, new and improved materials have been developed for the cutting structure of the cutter, thereby providing a longer useful lifetime for the cutter. This has resulted in the bearing systems being the first to fail during the drilling operation. Consequently, a need clearly exists for a system that will extend the useful lifetime of the bit.

DESCRIPTION OF PRIOR ART

In U.S. Pat. No. 3,244,415 to J. E. Ortloff, patented Apr. 5, 1966, a lubricating system for extending the life of the bearings of a roller cone type bit is shown. Sealing means are provided to effectively separate or close off the clearance between the journal of the leg and the bearings of the roller cone from the exterior of the bit. A special pump means is provided to circulate the lubricating fluid under high pressure to this sealed-off clearance space. The pump means is actuated by the rotation of the roller cone element on the shaft.

In U.S. Pat. No. 3,251,634 to D. W. Dareing, patented May 17, 1966, a lubricating system for extending the life of the bearings of a roller cone type bit is shown. Sealing means are provided to effectively separate or close off the clearance or space between the journal of the leg and bearings of the roller cone from the exterior of the bit. An electrical pump means is provided to supply a lubricating fluid under high pressure to this sealed-off clearance space.

In U.S. Pat. No. 3,746,405 to Russell L. Welton, patented July 17, 1973, a well drilling bit lubrication system and seal is shown. A journal bearing lubrication means and a seal cooperatively combined therewith to maintain lubrication throughout the useful life of the roller cutter of a well drilling bit, to the exclusion of foreign materials entering therein from the drilling fluids and surrounding earth formations. A journal bearing of right cylinder form is provided, characterized by the formation of a strategically placed recess, or recesses therein, and all without subtracting from the load carrying capabilities of the bit; the assembly being retained in working condition by a single element combined with the lubrication means and assuring proper axial placement of the roller cutter.

U.S. Pat. No. 3,235,316 to J. R. Whanger, patented Feb. 15, 1966, shows a friction bearing of large load capacity between a pair of relatively rotatable members in which at least one of said members has a quantity of indentations extending from the bearing surface thereof. Said quantity of indentations is filled with a soft metal having anti-galling characteristics, and the balance of said bearing surface is a hard metal of high wear resistance, the hardness and wear resistance of said hard metal being comparable to those of a carburized and hardened steel.

SUMMARY OF THE INVENTION

In order to extend the useful lifetime of the bearings of a rotary rock bit, the present invention provides a system for circulating lubricant into the loaded contact area between the bearing pin and the rotating bearing element within the cutter. The bit includes a bit body with at least one bearing pin extending from said bit body. A rotatable cutter is mounted upon the bearing pin and the rotatable cutter has a cutter interior surface. Seal means are provided between the bit body and the rotatable cutter to provide a seal and prevent lubricant from escaping into the borehole and borehole fluids from entering the bearing area. Bearing means between the bearing pin and the rotatable cutter promote rotation of the cutter. At least one wiper cavity is located in the interior surface of the rotatable cutter. A wiper pad is positioned in the wiper cavity and a resilient member is positioned beneath the wiper pad. As the cutter rotates, the wiper pad forces lubricant into the load area between the bearing pin and the interior surface of the cutter. The above and other features of the present invention will become apparent from a consideration of the following detailed description of the invention when taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one arm of a three cone rotary rock bit constructed in accordance with the present invention.

FIG. 2 shows a bearing element of the bit shown in FIG. 1.

FIG. 3 is a sectional view of a bearing pin and bearing element of another embodiment of the present invention.

FIG. 4 is a sectional view of a bearing pin and bearing element of another embodiment of the present invention.

FIG. 5 illustrates other embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and to FIG. 1 in particular, one arm of a three cone rotary rock bit is shown. The bit is generally designated by the reference number 10. The bit 10 includes a bit body 11 adapted to be connected to the lower end of a rotary drill string (not shown). One arm 12 of the bit's three arms is shown depending from the bit body 11. A cone cutter 13 is mounted upon a bearing pin 14 extending from the arm 12. The cutter 13 includes cutting structure 15 on its outer surface. Cutting structure 15 is shown in the form of tungsten carbide inserts; however, it is to be understood that other cutting structures, such as steel teeth, may be used as the cutting structure on the cone cutter 13.

The cutter 13 is rotatably positioned on the bearing pin 14 and adapted to disintegrate the earth formations as the bit is rotated. The cutting structure 15 on the outer surface of cutter 13 contacts and disintegrates formations in a manner that is well known in the art. A plurality of bearing systems are located in the bearing area between the cutter 13 and the bearing pin 14. The bearing systems in the bearing area include an outer friction bearing 16, a series of ball bearings 17, an inner friction bearing 18, and a thrust button 19. An O-ring seal 20 is positioned between the cutter 13 and the bearing pin 14. This seal retains lubricant in the bearing area around the bearing systems and prevents any materials in the well bore from entering the bearing area. The O-ring seal 20 prevents fluid flow in either direction.

Referring now to FIG. 2, the outer friction bearing element 16 is shown in greater detail. The inner surface 21 of the outer friction bearing element 16 includes a multiplicity of wiper cavities 22. A corresponding multiplicity of wiper pads 23 are positioned in the wiper cavities 22. As shown in FIG. 1, spring elements 24 are positioned beneath the wiper pads 23 in the wiper pad cavities 22. The spring elements 24 force the wiper pads 23 toward the bearing pin 14. The spring elements 24 may be flat springs as shown or other resilient elements such as belville type springs or pads of resilient material.

The structural details of a bit constructed in accordance with the present invention having been described, the operation of the bit will now be considered with reference to FIGS. 1 and 2. In use, the bit 10 is connected as the lower member of a rotary drill string (not shown) and lowered into a well bore until the cone cutters engage the bottom of the well bore. Upon engagement with the bottom of the well bore, the drill string is rotated, rotating bit 10 therewith. The cutters rotate upon the respective bearing pins. During the rotation of the cutter 13, the wipers 23 push lubricant into the load zone. As the wiper moves into the load zone, it is pressed into the wiper cavity 22 compressing spring 24 until the wipers 23 are flush with the interior surface 21 of the outer friction bearing 16. When the wiper pad 23 passes the load area, the spring 24 moves the wiper pad 23 outward allowing the wiper pad 23 to project from the interior surface 21 of the outer friction bearing 16 and push lubricant ahead of it. Lubricant generally accumulates in the area between bearing pin 14 and the outer friction bearing 16 on the unloaded side of the bearing pin 14. Lubricant is pulled from this area and pushed into the load zone to maintain a film of lubricant in the critical area.

Referring now to FIG. 3, another embodiment of the present invention is illustrated. A sectional view of a bearing pin 26 is shown with a bearing element 25 mounted upon the bearing pin 26. The bearing element 25 is adapted to fit within a cone cutter in the manner shown in FIG. 1. A section 30 of the top of bearing pin 26 is relieved thereby providing a lubricant storage area. The top of the bearing pin is the unloaded portion of the bearing pin 26 wherein lubricant normally accumulates. A multiplicity of wiper cavities 27 are machined in bearing element 25. A corresponding multiplicity of wiper pads 28 are positioned in the wiper pad cavities 27. A spring 29 is positioned in each wiper pad cavity 27 to force the wiper pad 28 toward the bearing pin 26. As the cone cutter (not shown) and bearing element 25 rotate, the wiper pad 28 passes the relieved section 30 pushing stored lubricant ahead of the wiper pad 28. The wiper pad 28 continues pushing the lubricant into the loaded side of the bearing pin 26. The wiper pads 28 are forced into the cavities 27 against the force of spring 29 until the wiper pads are flush with the surface of bearing element 25 as they pass the loaded side of the bearing pin 26.

Referring now to FIG. 4, another embodiment of the present invention is illustrated. A bearing pin 30A is shown in cross section with a bearing element 31 mounted to rotate thereon. A multiplicity of cavities are formed in the interior surface of the bearing element 31. Wiper pads 33 are positioned in the cavities 32. The wiper pads 33 serve to force lubricant into the loaded side of the bearing pin 30A. Lubricant is channeled from a lubricant reservoir in the body of the bit through a passage 34 to the unloaded side of bearing pin 30A. The wiper pads 33 pick up the lubricant and carry it to the loaded side of bearing pin 30A. The bearing element 31 rotates clockwise on the bearing pin 30A shown in FIG. 4. A portion 35 of the passage 34 is relieved. This enables the wiper pads 33 to provide a pumping action as they traverse the unloaded side of the bearing pin 30A.

Referring now to FIG. 5, various forms of wiper pad cavities are illustrated. The different forms of wiper pad cavities are shown in a bearing element 36. The wiper pad cavities may be horizontal slots such as slots 37. In this form the wiper pads 38 push the lubricant directly around the bearing pin. The slots may be inclined in one direction as shown by the slots 39 or in a different direction as shown by the slots 40. By biasing the cavities in either direction, the wiper pads in the cavities will direct or pump the lubricant to other critical areas of the bit spaced from the bearing element 36. In addition, the wiper pads may be made of a porous material for absorbing lubricant in the unloaded area and contributing a boundary film as it passes under the loaded side. The pads may also incorporate small pockets or include a corrugated configuration on the lead section of the wiper for the purpose of trapping greater amounts of fluid and forcing it into the loaded area.