US2880970A - Water lubricated bit - Google Patents

Description

April 1959 K. H. SWART 2,880,970

I WATER LUBRICATED BIT I Filed June 10, 1957 KEN/V574 A. 51/427 4 v INVENTOR.

S tates. Pa

WATER LUBRICATED nrr Kenneth H. Swart, Compton, Califl, assignor to H. C. Smith Oil Tool Co., Compton, Cali, a corporation of California Application June 10, 1957, Serial No. 664,572

1 Claim. (Cl. 255-303) This invention relates to improvements in well drilling bits having roller cutters.

Explanatory of the present invention, bits of this character are subjected to extremely heavy loads 7 and antifriction bearings have been interposed between the roller cutters and the journals on which the cutters rotate. In order to prolong the useful life of the bit it is necessary that the bearings between the cutters and the journals be adequately lubricated and kept reasonably cool. It has heretofore been proposed to conduit fluid either in the form of a gas or a liquid from'the interior of the body of the bit through the arms of the bit and through the journals so as to be discharged at or adjacent the bearings. If a gas is employed for this purpose, it has little, if any, lubricating qualities and can function merely to cool the bearings and to blow out foreign matter that may tend to enter the bearings. If a liquid is used for this purpose such as the circulation fluid that is pumped down the drill string of a rota ry well drilling apparatus, this circulation fluid c ontains'and carrieswith it small abrasive particles. Whilethe larger of these particles can be filtered. or strained out, very small particles contained in the circulation fluid are capable of passing through any ordinary filter "suitable for this purpose. Thesesmall particles, while they may pass through the bearings without detrimental effect if not under high velocity, become I highly abrasive and erosive if the fluid that is discharged at or near the bearings is under high velocity.

A primary object of the present invention is to provide an improved well drilling bit having roller cutters wherein a passage is provided from the interior of the body of the bit through the arms and journals of the bit to discharge adjacent the bearings, which passage has not only a filtering means therein but a velocity-reducing means. Consequently, a portion of the circulation fluid supplied to the interior of the bit by the drill string can be filtered to remove large solid particles and its velocity reduced materially so that the fluid will be discharged through the bearings at a relatively low rate of flow. In this manner, although there may be a large number of microscopically small solid particles in the filtered liquid, these particles will not have the objectionable cutting or abrasive action that would be occasioned if the filtered fluid were dis charged at a high rate.

Another object of the invention is to provide a well drilling bit having the above-mentioned characteristics wherein by means of a relatively simple construction fluid can be conducted to the nose bearings formed between the cutters and the journals on which they rotate so that these bearings may be lubricated and cooled by the fluid as well as the anti-friction bearings which are designed to carry the principal portion of the load.

With the foregoing and other objects in view, which will be made manifest in the following detailed description and specifically pointed out in the appended claim, reference is had to the accompanying drawings for an illustrative embodiment of the invention, wherein:

Figure 1 is a partial view of a well drilling bit largely ICC shown in vertical section and illustrating the essential portions of the present invention; and

Fig. 2 is a partial view in section taken substantially upon the line 22 upon Fig. l in the direction indicated.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, the construction of the body of the bit may conform to any conventional or preferred design. I have illustrated the body of the bit at 10 having a threaded pin 11 at its top by which the bit may be connected to drill collars which may be at the bottom of a conventional rotary well drilling string. 1

The body 10 has arms extending downwardly therefrom, one of which is indicated at 12, terminating in downwardly and inwardly directed journals one of which is indicated at 13.on which cutters 14 are rotatable. .The nature of the teeth or cutting edges on the exterior of the cutters 14 is immaterial insofar. as the present invention is concerned. Adjacent the base of each cutter there is a roller radial bearing, the rollers of which are indicated at 15 and inwardly of this radial bearing there may be a ball thrust bearing the balls of which are indicated at 16. Races are formed on the interior of the cutter 14 and on the exterior of the journal13 complementary to the rollers 15 and balls 16, respectively. The balls are fed into a. position between the races therefor by passing them consecutively through an aperture 17 formed in the arm 12 and journal 13. When the ball bearing is completed the balls are retained in position by positioningin the aperture 17 a plug 18 which iswelded in place such as by the weld 19.

Coaxially with the journal 13 there is arranged a pilot pin 20 which may be'pressed or shrunk into the journal, and this pilot pin may have recessed therein a friction thrust button 21 formed of hard metal or formed of a metal on which a hard chrome facing is applied. A corresponding and cooperating thrust button; 22 is recessed in the cutter so as to oppose the-thrust button 21. On the exterior of the pilot-pin which protrudes from the journal 13 there maybe formed an-annular groove which is filled with a hard wear-resisting metal such as hard facing, indicated at 23, and on the interior of the cutter 14 there may be recessed a bushing 24 formed either of hard metal or equipped with a hard surface such as hard chrome. This bushing is intended to cooperate with the hard facing 23 to form a friction radial bearing at the nose of the journal and the thrust buttons 21 and 22 are intended to cooperate to form a friction thrust bearing adjacent the nose of the journal.

The object of the present invention is to lubricate and to cool the friction bearings and also the anti-friction bearings at 15 and 16. To this end, a passage 25 is formed in each arm which communicates at its upper end with the interior 26 on the body of the bit. The upper end of this passage is enlarged to receive a filter 27. The exact nature of this filter may vary but a filter that is suitable for the purpose consists of porous bronze wherein small bronze spheres or bronze powder are sintered together in disc or plate form with the interstices between the bronze particles forming small passages through which fluid may pass. This filter may be tack-welded in the enlargement at the upper end of the passage 25 such as by tack-welds 28 and the filter is preferably arranged in an inclined position with relation to the axis of the bit so that circulation fluid passing downwardly through the bit will tend to continually scour it and prevent the building up of a filter cake on its upper surface which would de tract from the flow of liquid through the filter.

Between the filter 27 and the plug 18 the passage 25 is filled with small round objects 29. These objects may be graded or sized gravel but preferably I employ copper coated steel balls. These balls cooperatively form a velocity-reducing means in that the spaces between the balls form tortuous passages through which the filtered liquid must flow from the filter 27 to the aperture 17. The balls may be regarded as collectively forming an impediment to fluid flow through the passage 25. The plug 18 is externally reduced as indicated at 30 adjacent the lower end of the passage 25 so as to provide a passage extending circumferentially about the plug 18. The reduction in size of the plug 18 to form this circumferentially extending passage is not so great, however, that the balls or objects 29 can pass out of the passage 25 and into the cireumferentially extending passage that extends around the plug. Axially of the journal 13 there is formed a passage 31 that communicates with the circumferential passage around the plug 18. This, in turn, communicates with a passage 32 formed in the pilot pin 20. The lower end of this passage may communicate with a small bore 33 formed in the thrust button 21 or it may communicate witha radial passage 34 formed in the pilot pin or both as illustrated. The outer end of the passage 34 communicates with a groove 35 that is milled or otherwise formed in the exterior of the pilot pin.

In the normal operation of the bit, circulation fluid is constantly being pumped down the drill string and into the interior of the body at 26. Most of this circulation fluid is discharged through circulation ports 36 formed in the body. Usually this circulation fluid that issues from these ports is directed against the teeth on the cutters 14 but not necessarily so. A portion of the circulation fluid passes through the filter 27 which will strain out large solid particles that may be carried by the circulation fluid. The filter fluid passes down through the tortuous passages between the balls 29 and although the filtered fluid may still contain microscopic solid particles the reduction in velocity occassioned by the filtered fluid flowing around and between the balls 29 materially reduces the cutting action of these microscopic particles. The filtered fluid then enters the circumferential passage at 30 around the plug 18 and passes through the passages 31 and 32 where it is discharged near the nose bearings at 3'3 and through the groove 35. The fluid thus released tends to lubricate and cool the friction thrust bearing between the buttons 21 and 22, the friction radial hearing between the bushing 24 and the hard facing 23, and

. 4' then flows outwardly between the cutter and the journal and between the balls 16 and the rollers 15. The fluid finally finds egress between the base of the cutter and the arm 12.

In a typical situation the diameters of the balls 29 are from 30/1000" to /1000 and a pressure drop is created between the interior 26 of the body of the bit and the outlet between the base of the cutter 14 and the arm 12 of from 200 to 600 lbs. per square inch. The rate of flow is consequently materially reduced. Thus, if the bit is discharging circulation fluid at a rate of between 400 to 700 gallons per minute, the rate of flow through the bearings is reduced to from 5 to 20 gallons per minute. In this manner, I supply the bearings with relatively clean liquid possessing some lubricating qualities, and I discharge the liquid through the bearings at a relatively low velocity so that although the liquid may still contain microscopically small solid particles, the rate of flow is so small that these particles no longer cut and destroy metallic surfaces which they encounter.

Various changes may be made in the details of construction without departing from the spirit and scope of the invention as defined by the appended claim.

I claim:

A well drilling bit having a downwardly extending arm, a journal on the arm, a roller cutter rotatably mounted on the journal, one or more bearings between the journal and the cutter, a passage in the arm and journal for conducting fiuid from the interior of the body of the bit to the bearings, a filtering means adjacent the upper end of the passage, and velocity reducing means in the passage beneath the filtering means whereby relatively clean fluid will be delivered to the bearings at relatively low velocity, said velocity reducing means being in the form of a multiplicity of generally spherical bodies filling a substantial length of the passage.

References Cited in the file of this patent UNITED STATES PATENTS 1,816,203 Behnke July 28, 1931 1,947,586 Fletcher Feb. 20, 1934 2,147,926 Scott Feb. 21, 1939 2,661,932 Woods Dec. 8, 1953

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