US3251634A

US3251634A - Drill bit bearing lubricator

Info

Publication number: US3251634A
Application number: US292020A
Authority: US
Inventors: Donald W Dareing
Original assignee: Exxon Production Research Co
Current assignee: ExxonMobil Upstream Research Co
Priority date: 1963-07-01
Filing date: 1963-07-01
Publication date: 1966-05-17
Anticipated expiration: 1983-05-17

Description

y 7, 1966 D. w. DAREING 3,251,634

2 Sheets-Sheet 2 Filed July 1, 1963 Donald W. Doreing INVENTOR. 5204 4i M ATTORNEY United States Patent Oil 3,Zl,fi34 Patented May 17, 1966 3,251,634 DRILL BIT BEARING LUBRICATOR Donald W. Dareing, Tulsa, Okla, assiguor, by mesne assignments, to Esso Production Research Company, Houston, Tex., a corporation of Delaware Filed July 1, 1963, Ser. No. 292,020

7 Claims. (Cl. 308-82) This invention relates to the drilling of boreholes in the earth. It relates particularly to roller cone type bits for use in the drilling of boreholes. It relates especially to a system for providing lubrication to such roller cone bits.

In the art of drilling Wells for the production of oil and gas the most commonly used method is the so-called rotary drilling method. In the rotary drilling method, a drill string is suspended at the lower end of a string of drill pipe which is supported from the surface of the earth. The drill string is conveniently formed of many joints of drill pipe, each joint usually being about 30 feet long. As the hole is deepened, additional joints of drill pipe as needed are connected into the string. A drilling fluid under high pressure is forced down through the drill string, through the drill bit, and back up to the surface through the annulus between the drill pipe and the wall of the borehole. While the drilling fluid serves primarily to carry the rock cuttings from the drill bit to the surface, it also serves to cool the drilling bit. The drill bit obtains its rotary motion from the drillpipe which is rotated from the surface. It is known that .the rate of penetration of a drill bit can be increased by increasing'the force of the drill bit on the bottom of the borehole. The penetration of. the drill bit is also influenced by the rate at which the drilling fluid is forced through the drill pipe and by the rate of rotation of the bit.

One of the most widely-used types of bit at the lower end of a string of drill pipe is these-called rock bit or roller cone bit. A rock bit is normally composed of a shank member which threadedly connects into the lower end of a string of drill pipe. Usually three leg members extend downwardly from the shank. The lower end of each leg member is sometimes called a shaft which extends inwardly and downwardly toward the axis of the bit. The exterior of the shaft contains inner bearing races. Roller and ball bearings support the bit cones, which contain cutting elements, and also transmit the cone force to the shaft. The interior of the roller cone element contains the outer bearing races. As the drill pipe is rotated, the bit is likewise rotated. As the bit is rotated, each individual cone rotates about the shaft of the leg member from which it is supported. The cone, which is in contact with the bottom of the borehole, also rotates about the axis of the bit. Normally only the roller cutting surface of the cone is exposed to the bottom of the hole. The action of the rolling cutting surface on the bottom of the hole is a twisting, tearing or gouging action for softer formations and an approximate chipping, crushing action on the harder formations. To perform ideally, a rock bit should be so designed that the teeth, that is the roller cutting portions of the cone, and the bearings which support the roller cone from s particles of the rock or earth formation that has been drilled into the bearings. These two factors cause a rapid deterioration or wearing away of the bearings and failure of the bit.

Accordingly, it is an object of this invention to provide a lubricating system for extending the life of the bearings of a roller cone type bit. Sealing means are provided to effectively separate or close off the clearance or space between the journal of the leg and the bearing of the roller cone from the exterior of the bit. Means are provided to supply a lubricating fluid under high pressure to this sealed off clearance space. This system provides high lubricating characteristics. It provides for (a) hydrostatic bearing by the pumping of lubricating fluid between the journal and the bearing; (b) a hydrostatic squeeze film is available as lubricating fluid is always present between the two surfac'es; and (c) a third component of the film pressure is developed by the relative rotation of the bearing components and can be called hydrodynamic effect.

Other objects and a complete understanding of the invention can be had from the following description taken in conjunction with the drawing in which:

FIG. 1 illustrates one embodiment of a roller bit incorporating the lubricating system of the invention;

FIG. 2 illustrates a specific pump for developing the pressure of the lubricating fluid between the journal and the bearing while the bit is being rotated at the bottom of the borehole.

Attention is first directed to FIG. 1. Shown thereon is a shank 10 from which extends leg member 12. In most cases there will be three such leg members; however, for the purposes of illustrating this invention only one leg will be shown. Leg member 12 has an integral shaft- 14 forming a journal 16. The shaft 14 extendsinwardly and downwardly toward the axis of the bit. Shank 10 has an internal chamber 18 through which drilling fluid is conducted downwardly to passageways 20 and about the cutters. A roller cutter element 22 having cutting elements 24 is rotatably supported about shaft 14. The internal surface of roller cone element 22 forms a bearing 26 which mates with journal 16. It is preferred that bearing 26 and journal 16 be elliptical in shape. A clearance 28 is provided between the journal 16 and bearing 26. Clearance 28 is normally in the range of from about .0005 inch to about .002 inch.

Roller cone 22 is rotatably supported from shaft 14 of the bit leg 12 by ball bearings 30. The inner race for ball bearings 30 is provided at 32 in shaft 14. Onehalf of the outer race is provided at 34 in the inner portion of roller cone 22. The other half of the outer race is provided at 36 in annular bearing retainer 38. Suffi-. cient clearance is provided between face 37 of shirt tail 40 of leg 12 and retainer 38 to permit placing ball bearings30 in their races after the retainer has been placed over shaft 14 and adjacent face 37.

Seal means are provided between the bearing retainer 38 and shirt tail 40 of bit leg 12. Shaft 14 has an annular groove or cell 50 which is positioned just above the inner race 32. Seal means includes a seal member 42 partially in annular groove 50 and which can, for example be rubber bonded to internal shoulder 44 of retaining ring 38. Integral with seal 42 is annular ring 46 which fits into annular groove 48 of leg 12. A second seal element 52, which can be phenolic rosin, impregnated high carbon or bronze for example, is held against face 54 of annular groove 50 by a conical disc spring 56. One end of conical disc spring 56 is secured to bearing retainer 38.

As shown above, roller cone element 22 is rotatably supported from shaft 14 of leg 12 by ball bearing means a 30 and its associated races. A sealing contact is made between the roller cone and the leg. Thus clearance 28 is effectively sealed and isolated from the exterior of roller cone 22.

Attention is next directed toward that part of the system for circulating lubricating fluid under high pressure through the clearance between the journal 16 and hearing 26. This includes pump means 58 having inlet 60 and outlet 62. A plug 59 holds pump means 58 in place. The pump means can be of various kinds, for example it can be a pump driven by an electric motor 58A having wires or conductors 64 extending to the surface. The pump should be capable of putting out relatively high pressure, the pressure depending largely upon the load applied to the bit, the size of clearance 28 and the depth drilled. As clearance 28 has a relatively small volume, the volume of the output of the pump means is normally rather small. Another suitable pump is shown in FIG. 2 and described in detail hereinafter.

Outlet 62 of pump 58 is connected to clearance 28. In drilling, the greatest force between journal 16 and bearing 26 is at the bottom. Thus outlet 62 is directed downwardly through conduit 63 to this point or area of greatest force. By pumping the lubricating fluid between the bearing and the journal, a hydrostatic bearing effect is obtained. By having a fluid between the bearing and the journal, a hydrostatic squeeze film is effected. By having a fluid contained in clearance 28, a hydrodynamic effect is developed when relative motion between the bearing coinponents are achieved as in drilling. Inlet 60 to pump 58 is connected to annular cell 50. This annular cell 50 is in communication with clearance 28. Thus a circulating path fluid is obtained through the inlet 60 of pump 58, through pump 58 to outlet 62, through clearance 28, through annular cavity 50, conduit 61 and back to the inlet 60 of pump 58.

It is very important to prevent drilling fluid from entering clearance 28.

Seals

42 and 52 prevent this as long as they are working properly. To aid in their proper working, the pressure in annular cavity 50 is maintained slightly above that of the pressure of the mud in the borehole surrounding the bit. If the seal should develop a slight leak, lubricating fluid would escape due to the pressure being in excess of that of the drilling fluid. Means are provided so that when this occurs, make-up lubricating fluid is supplied to pump 58. A lubricating fluid reservoir 68 is provided in bit leg 12 and is in communication through conduit 66 with inlet 60 of pump 58. Fluid reservoir 68 is preferably cylindrical in shape and having a diameter d Axially aligned with fluid reservoir 68 is a second reservoir 70 having a diameter d which is larger than 11 Cylinder 70 extends or opens into the exterior of leg 12. Mounted in cylinder 70 is a piston member having an upper portion or element 72 of diameter d which is essentially the diameter of cylinder 70. A retaining ring 91 holds piston 72 within the cylinder. Sealing rings 74 are provided to give it a sliding and sealing contact with the inner wall of cylinder 70. Extending downwardly from element 72 is a piston extension 76 having seal ring 77 which has a diameter d substantially the same as the diameter of fluid reservoir 68. An automatic lubricating fitting 78, such as a Zerk, is provided in piston element 72 in communication with a passage 80. Fitting 78 can be a valve which can be opened when it is desired to pump fluid downwardly through passage 80 and can be closed at other times. A conduit 81 extends from annular space 84 beneath piston element 72 to the exterior'of the bit. A valve means or plug 82 is provided at the outer end of conduit 81. When it is desired to load fluid reservoir 68, valve 82 is opened and piston 72 is pushed to its lowermost position. This exhausts all the air or other fluid which is below piston element 72. Valve 82 is then closed; thereafter, a lubricating fluid is injected through fitting 78 and passageway into the fluid reservoir. As fluid is injected, it forces piston element 72 into an upwardly movement. As the piston goes up, a vacuum occurs or exists in annular space 84.

It is believed that the operation of the tool in FIG. 1 is apparent. Prior to attaching the bit onto the lower end-of a string of drill pipe, the fluid reservoir 68 is filled as indicated in the immediate paragraph above. When drilling operations are commenced, roller cutting elements 22 rotate about the axis of shaft 14 of leg 12. When drilling starts, pump 58 is also commenced and forces fluid under high pressure into clearance 28. This causes a hydrostatic bearing and maintains the journal 16 from contact with bearing 26. The fluid then flows through clearance 28, through annular cell 50, back to the inlet 60 of pump 58. The fluid in reservoir 68 is maintained under relatively high pressure by the piston

differential arrangement

72 and 76. The pressure of the drilling fluid in the well bore acts on the upper surface of piston element 72, which is of a greater area than the area of the lower end of piston element 76. Thus the pressure of the make-up fluid in the fluid reservoir 68 is in excess of that of the drilling fluid exterior of the bit. Pump 58 is selected to have an output pressure substantially greater than that developed in reservoir 68. As the clearance is very small between journal 16 and hearing 26, there is normally a very high pressure drop from the pump outlet 62 to the fluid in annular cell 50. For example, for a 9 inch diameter bit having a clearance 28 of about .001 inch, this pressure drop is, for example, in the range of from about 15,000 to about 20,000 p.s.i. An additional pressure component in the film of lubricating fluid in clearance 28 is built up as a result of the squeezing motion between bearing 26 and journal 16. As the bearing rotates with respect to the journal, hydrodynamic pressure is developed in the clearance 28 and also contributes to the total load carrying capacity of this bearing. In addition to these improved results, the lubricating fluid under pressure prevents any possibility of drilling mud particles entering clearance 28 and causing damage to the hearing or journal surfaces.

Attention is now directed to FIG. 2 which shows a specific form of pump 58 suitable for practice of this invention. Portions of FIG. 2 which are substantially the same as that shown in FIG. 1 are given the same reference numbers and their description is not repeated. In FIG. 2 the pump means comprises a chamber which is cylindrical and axially aligned with the axis of the shaft 14. A piston 102 is mounted in cylinder'100 and seals 104 provide the sealing contact between piston 102 and the cylinder 100. External splines 106 of piston 102 engage internal splines 108 of the cylinder, thus piston 102 has longitudinal movement within cylinder 100 but does not have rotational movement therein. Mounted between the upper end of cylinder 100 and piston 102 is a spring 110 which urges piston 102 outwardly in the direction of the splines. The outermost end of piston 102 is cut to form a diagonal face 112. A second diagonal face 114 is provided on roller cone 22. It is then seen that as roller cone 22 rotates about shaft 14 of leg 12 during drilling operations, that piston 102 reciprocates within cylinder 100. The upper end of cylinder 100 is connected through conduit 116 through check valve 118 to clearance 28 between the journal and the bearing. Shaft 14 has a flat surface 120 to aid in getting fluid into the clearance 28. Check valve 118 permits the flow of fluid only toward such flat surface from the pump. An intake check valve 122 is provided at the inlet to cylinder 100 from

conduits

68 and 117.

To briefly recapitulate, the bearing means presented herein includes the journal defined by the lower part of leg 12, the bearing 26 defined by the inner part of roller cutter element 22 and the lubricating fluid film in clearance 28 between the journal and the bearing. The fluid film between the journal and the bearing is developed primarily as a result of (a) the hydrostatic film principle which depends on a positive pump, and (b) the squeeze film principle which depends on the squeezing motion between the journal and the bearing. A third component of the total pressure of the film is a result of the hydrodynamic pressure buildup and is usually quite small in comparison with theother two components. The film thickness in the hydrodynamically lubricated bearing depends upon the ratio nN/P where ,u. is viscosity of the lubricant, N is angular velocity of bearing and P is load on the bearing. If the contribution from the hydrodynamic component is to carry alarge part of the total load, the viscosity of the lubricating fluid should be about 5,000 centipoises or higher as measured at atmospheric pressure and 100 F.

While there are above disclosed but a limited number of embodiments of the system of the invention herein presented, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed. It is therefore desired that only such limitations be imposed on the appended claims as are stated therein.

What is claimed is:

1. A bit which comprises:

a shank means; I

a leg member extending from said shank means, the lower portion of said leg member forming a journal;

a roller cone member, a portion of said roller cone member shaped to define a bearing means mating with the journal of said leg member; said journal of said leg member and said bearing means of said roller cone member having a clearance therebetween;

a pump means having an inlet and an outlet and carried within said leg member;

first means connecting the output of said pump means with a first portion of the clearance between the journal of said leg member and the bearing means of said roller cone member;

means connecting the input to said pump means with a second portion of the clearance between the leg member journal and the bearing means of the roller cone member;

means for preventing the escape of such lubricating fluid from between said journal and said bearing means; and

a lubricating fluid reservoir means for supplying fluid under pressure to the input of said pump means.

2. An apparatus as defined in claim 1 in which the journal and the bearing means are each ellipsoidal.

3. A bit for drilling boreholes in the earth which comprises:

a shank means;

a bit leg extending from said shank means, the lower portion of the bit leg shaped to define an ellipsoidal journal;

a roller cone member, a portion of said roller cone shaped to define a bearing means mating with the journal of said bit leg; said journal of said bit leg and said bearing means of said roller cone member having a clearance therebetween;

pump means carried within said bit leg and having an input and an output;

means connecting the output of said pump means with a first portion of the clearance between said journal and said bearing means; I

second means connecting a second portion of the clearance between said journal and said bearing means with the input to said pump means;

means preventing the escape of lubricating fluid from between said journal and said bearing means to the exterior of said roller cone member;

a first cylinder within said bit leg of one diameter;

a second cylinder axially aligned with said first cylinder and of a lesser diameter and being adapted to contain a lubricating fluid;

a piston' means in said first cylinder and adapted to sealingly engage the walls thereof;

an extension member from said piston means extending to and of the same diameter as said second cylinder; and

means connecting the second cylinder with the input to said pump means.

4. A bit for drilling boreholes in the earth which compries:

a shank means;

a bit leg extending from said shank means, the lower portion of said bit leg defining a shaft member;

a roller cone member;

means to rotatably support said roller cone member about the shaft member of said bit leg; said roller cone member and said shaft member having a space therebetween;

pump means carried within said bit leg and having an input and an output;

means connecting the output of said pump means with a first portion of the space between said roller cone member and said shaft member;

second means connecting a second portion of the space between said roller cone member and said shaft member;

means preventing the escape of lubricating fluid from said space;

a first cylinder within said bit leg of one diameter;

a second cylinder axially aligned with said first cyl-' inder and of a lesser diameter and being adapted to contain a lubricating fluid;

a piston means in said first cylinder and of a character to sealingly engage the walls thereof;

an extension member from said piston means extending to and of the same diameter as said second cylinder, said extension member sealingly engaging the walls of said second cylinder; and

means connecting the second cylinder with the input to said pump means.

5. An apparatus as defined in claim 4 including conduit means connecting said second cylinder with the exterior of said leg and means within such conduit means for opening and closing such conduit means.

6. An apparatus as defined in claim 5 including conduit means establishing fluid communication from within said first cylinder below said first piston means and the exterior of said leg and valve means in such conduit.

7. An apparatus as defined in claim 6 in which the space between said roller cone member and said shaft member has a clearance in the range from about .0005 inch to about .002 inch.

References Cited by the Examiner UNITED STATES PATENTS 1,635,592 7/1927 Wadsworth 229 1,838,067 12/1931 Wadsworth 175229 1,909,128 5/1933 Scott et al 175228 X 2,065,742 12/1936 Reed 3088.2 2,513,634 7/1950 Francis 308-82. 3,047,344 7/1962 Gros 3088.2

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, Examiner.

W. J. MALONEY, E. R. PURSER, Assistant Examiners.

Claims

1. A BIT WHICH COMPRISES: A SHANK MEANS; A LEG MEMBER EXTENDING FROM SAID SHANK MEANS, THE LOWER PORTION OF SAID LEG MEMBER FORMING A JOURNAL; A ROLLER CONE MEMBER, A PORTION OF SAID ROLLER CONE MEMBER SHAPED TO DEFINE A BEARING MEANS MATING WITH THE JOURNAL OF SAID LEG MEMBER; SAID JOURNAL OF SAID LEG MEMBER AND SAID BEARING MEANS OF SAID ROLLER CONE MEMBER HAVING A CLEARANCE THEREBETWEEN; A PUMP MEANS HAVING AN INLET AND AN OUTLET AND CARRIED WITHIN SAID LEG MEMBER; FIRST MEANS CONNECTING THE OUTPUT OF SAID PUMP MEANS WITH A FIRST PORTION OF THE CLEARANCE BETWEEN THE JOURNAL OF SAID LEG MEMBER AND THE BEARING MEANS OF SAID ROLLER CONE MEMBER; MEANS CONNECTING THE INPUT TO SAID PUMP MEANS WITH A SECOND PORTION OF THE CLEARANCE BETWEEN THE LEG MEMBER JOURNAL AND THE BEARING MEANS OF THE ROLLER CONE MEMBER; MEANS FOR PREVENTING THE ESCAPE OF SUCH LUBRICATING FLUID FROM BETWEEN SAID JOURNAL AND SAID BEARING MEANS; AND A LUBRICATING FLUID RESERVOIR MEANS FOR SUPPLYING FLUID UNDER PRESSURE TO THE INPUT OF SAID PUMP MEANS.