US3299973A

US3299973A - Lubrication and sealing of well drilling bit

Info

Publication number: US3299973A
Application number: US387268A
Authority: US
Inventors: Kenneth H Swart; William P Robinson
Original assignee: Smith Industries International Inc
Current assignee: Smith Industries International Inc
Priority date: 1964-07-27
Filing date: 1964-07-27
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24

Description

Jan. 24, 1967 K. H. swART ETAL 3,299,973

I LUBRICATION AND SEALING OF WELL DRILLING BIT Filed July 27. 1964 2 Sheets-Sheet 1 FIG. l.

ATTORNEYS Jan. 24, 1967 K. H. SWART ETAL 3,299,973

LUBRICATION AND SEALING 0F WELL DRILLING BIT 2 Sheets-Sheet 2 FZUEMUIQ EWE 332 INVENTORS KENNETH H. SWART BY WILLIAM P ROBINSON ATTORNEYS United States Patent 3,299,973 LUBRICATION AND SEALING 0F WELL DRILLING BIT Kenneth H. Swart and William P. Robinson, Compton,

Califi, assignors to Smith Industries International, Inc.,

Compton, Califl, a corporation of California Filed July 27, 1964, Ser. No. 387,268 8 Claims. (Cl. 175-371) This invention relates to improvements in well drilling bits, and particularly to that type of well drilling bit which employs roller cutters.

It has been proposed heretofore to supply the roller cutters of a well drilling bit with a lubricant which will lubricate the bearings between the cutter and the journal on which the cutter rotates and to provide a seal between the cutter and the body of the bit that will tend to confine the lubricant within the cutter and prevent ingress of destructive materials to the bearings.

A primary object of the present invention is to provide an improved seal which is of extremely simple and durable construction which will prevent ingress of destructive materials and which will be effective regardless of whether the cutter may be angularly displaced, radially displaced, or axially displaced with respect to the journal.

Another object of the invention is to provide a seal which has the above-mentioned characteristics and which can be used in a manner to facilitate the assembly of the bit in the course of its construction.

Still another object of the invention is to provide a well drilling bit of the roller cutter type wherein a differential in hydrostatic pressure is caused to exist across the seal so that there will be a net effective pressure on the exterior of the seal which constantly urges it into sealing engagement, thus assuring that ingress of destructive materials to the hearing or bearings will be effectively prevented.

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 claims, reference is had to the accompanying drawings for an illustrative embodiment of the invention, wherein:

FIGURE 1 is a partial view in vertical section through a portion of a well drilling bit embodying the present invention;

FIG. 2 is a partial view in vertical section illustrating the manner in which the bit embodying the present invention can be advantageously assembled; and

FIGS. 3, 4, 5, and 6 are partial views in section illustrating the manner in which the seal is effective in the event that the cutter is angularly displaced, radially displaced, or axially displaced with respect to the journal on which it is rotatable.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, the improved well drilling bit consists of a body 10, the upper portion of which is shaped to provide a threaded pin 11 providing for its engagement to the lower end of a drill string. On this body there is formed a journal 12 on which a roller type cutter 13 is rotatably mounted. 14 indicates a circulation hole through which well drilling circulation fluid may be discharged from the drill string in the vicinity of the cutter 13.

In conformity with conventional practice, there is a roller anti-friction bearing 15 between the cutter and the journal near the point of connection between the journal and the body 10. Inwardly of this roller bearing there is a ball bearing 16, the balls of which are fed into their races formed on the journal and on the interior of the cutter 13 through a ball passage 17 that is subsequently closed by a ball plug 18 welded in place as at 19. Friction-type bearings, both radial and thrust, indicated at Patented Jan. 24, 1967 20 and 21 respectively, may be provided between the inner end of the cutter and the inner end of the journal and appropriate passages may be formed for conducting lubricant to the

various bearings

15, 16, 20 and 21.

The above-described construction is more or less conventional in roller cutter-type well drilling bits but may be departed from insofar as the present invention is concerned.

An important part of the present invention relates to the establishment of a seal between the outer side of the cutter 13 and the body 10 around the base of the journal 12. To this end, a frusto-conical or inwardly tapering surface 22 is formed on the body 10 around the base of the journal 12. This frusto-conical or tapering sur face tapers in a direction axially of the journal and toward the inner end of the journal. Against this surface there is positioned in stretched condition an elastic, endless ring 23. This ring may conform in its construction to a conventional rubber O-ring being circular in plan and circular in cross-section. As this endless elastic ring rest against the surface 22 in a stressed or stretched condition it will continually tend to contract against this tapered surface and will consequently be constantly urged by its own self-exerted force against the counterbore surface 24 formed on the outer face of the cutter 13.

In order to lubricate the bearings between the cutter and the journal a lubricant reservoir 25 is formed in the body 10 adjacent each journal. This lubricant reservoir has a lubricant confined therein by means of a piston 26 that may be sealed such as by an O-ring 27. The upper surface of this piston is exposed to the hydrostatic pressure in the well that is accessible thereto through the opening 28 formed in the cap 29 that confines the piston in the lubricant reservoir. This cap may be welded in place, such as by welds 30.

A compression spring 31 is disposed in the lubricant reservoir and is compressed between the piston 26 and the plug 18. Lubricant in the lubricant reservoir can be expelled therefrom into the passages between the cutter 13 and the journal to lubricate the various bearings. The pressure within the cutter, however, is equal to the hydrostatic pressure existing on the exterior of the bit minus the elfective pressure exerted by the compressed coil spring 31. Consequently, the pressure of the lubricant in the lubricant reservoir and in the passages leading to the bearings will always be somewhat less than the hydrostatic pressure existing on the exterior of the bit. In this manner, a differential pressure is caused to exist on opposite sides of the sealing ring 23. On the outer side of the sealing ring 23 the pressure exerted is that of the hydrostatic pressure that is present on the exterior of the bit, which frequently is quite high, often several thousand pounds per square inch. On the inner side of the sealing ring 23 the pressure exerted by the lubricant is slightly less due to the force exerted by the spring 31 on the underside of the piston 26. This net effective pressure on the sealing ring 23 urging the sealing ring toward the interior of the cutter cooperates with the self exerted contractile force of the stretched sealing ring on the tapered surface 22 to urge the sealing ring into sealing engagement with the rotary cutter 13.

The improved seal lends itself toward facilitating as sembly of the bit. Thus, as illustrated in FIG. 2, in the course of assembling the elements of the bit the rollers of the roller bearing 15 may be assembled around the journal 12. The sealing ring 23 can'then be stretched and applied around the rollers and allowed to contract thereon and assume a position as illustrated in FIG. 2. Thereafter, the cutter 13 may be axially slipped onto the journal with the race on the cutter for the rollers 15 serving to slip the sealing ring 23 axially off of the rollers. Thesealing ring will consequently hold the rollers in assembled position while the cutter 13 is being applied. When the cutter shifts the sealing ring 23 off of the rollers and onto the tapered surface 22 the ring may contract further but even in its contractedpositi-on it is still stretched or stressed.

As illustrated in FIG. 3, if the cutter becomes angularly displaced with relation to the journal for any one of a number of different reasons, such as for example wear in the course of use the stretched sealing ring that is continually contraction on the tapered surface and which is subjected to the differential in pressures merely accommodates or adjusts itself to these conditions. Thus, in FIG. 3, a slight angular displacement is shown wherein the left-hand side of the cutter is spaced from the wall of the body surrounding the tapered surface 22 to a considerable extent but the right-hand side is not. The sealing ring merely adjusts itself to these conditions.

In FIG. 4, the cutter is illustrated as having been radially displaced with respect to the journal and under these conditions the sealing ring merely adjusts or accommodates itself to these conditions remaining in sealing engagement with the cutter.

In FIGS. 5 and 6, two forms of axial displacement of the cutter wit-h relation to the journal are illustrated. In FIG. 5, the cutter is shown as having been displaced toward the inner end of the journal and in FIG. 6, the cutter is shown as having been displaced toward the outer end of the journal. Under both sets of conditions the sealing ring merely conforms itself to the circumstances in which it finds itself and due to its self-exerted contractile effort on the tapered surface 22 coupled with the differential in pressure existing thereon sealing engagement is constantly maintained.

It will be appreciated that it is not necessary in all instances to create a differential in pressure across the sealing ring, such as by means of the spring-actuated piston 26. Without a spring-actuated piston the piston merely acts as a pressure equalizer to prevent full hydrostatic pressure being applied across the seal. Without such a differential in pressure the sealing ring may continue to function satisfactorily due to its stressed condition. The use of the differential pressures on opposite sides of the sealing ring is preferred however, and the use of such pressures on other forms of seals can be used to advantage. The simplicity of construction of the O-ring type seal causes that type of seal to be preferred, particularly on account of its ability to accommodate itself or adjust itself to the various conditions that it may encounter as illustrated in FIGS. 3 to 6, inclusive.

It will be appreciated from the above-described construction that the improved seal is very simple and is capable of being very economically employed. Furthermore, the seal when applied facilitates greatly the holding of the roller bearing 15 in place while the cutter is being applied.

We claim:

1. In a roller cutter well drilling bit wherein a roller cutter is mounted for rotation on a journal on a bit body, sealing means between the roller cutter and the bit body, and means for causing a differential in hydrostatic pressure to exist between the exterior of the bit and the interior of the cutter surrounding the journal when the bit is in operation and surrounded by drilling fluid with the lesser pressure in the interior of the cutter so that a net effective pressure will be applied to the sealing means by the drilling fluid urging the sealing means toward the interior of the cutter.

2. In a roller cutter well dsrilling bit, a body part having a journal and a cutter part rotatably mounted thereon, one of said parts having an annular tapered surface tapering towrd the other and disposed adjacent a face on the other, and an annular elastic sealing ring stretched onto said surface on said part which by reason of its contraction will crowd itself toward the other to form sealing engagement therewith, and means for causing a differential in hydrostatic pressure to exist between the exterior of the bit and the interior of the cutter part with the greater pressure on the exterior of the bit and the lesser pressure on the interior of the cutter when the bit is in operation and surrounded by drilling fluid, which differential in pressure is effective on the exterior of the sealing ring to urge the sealing ring against the mentioned face.

3. In a roller cutter well drilling bit, a body having a journal on which a roller cutter is rotatably mounted, said body presenting an annular surface tapering toward the cutter and disposed adjacent a face thereon, an endless elastic sealing ring disposed in stretched condition on said surface and crowded toward the mentioned face on the cutter by its effort to contract, means for causing a differential in hydrostatic pressure to exist between the exterior of the bit and the interior of the cutter, and means including a spring-urged piston whose spring is arranged to oppose pressure existing on the exterior of the bit for transmitting some of the hydrostatic pressure existing on the exterior of the bit to the interior of the cutter so that the net effective pressure on the ring will cooperate with its self-crowding to urge the ring into sealing engagement with the mentioned face on the cutter.

4. In a roller cutter Well drilling bit, a body part having a journal on which a roller cutter part is rotatably mounted, an annular surface on one of said parts which is tapered in a direction axially of the journal and toward an adjacent face on the other of said parts, an endless sealing ring on said surface in circumferentially stressed condition and consequently self-crowded toward the mentioned'face on the other part to sealingly engage therewith, and means causing a hydrostatic pressure differential to exist on opposite sides of the sealing ring when the bit is in operation and surrounded by drilling fluid to urge the sealing ring towards the said mentioned face on the other part.

5. In a roller cutter well drilling bit wherein there is a body having a journal on which a cutter is rotatably mounted, an endless sealing ring between the body and the cutter, and means for causing a differential in hydrostatic pressures on opposite sides of the sealing ring with the greater pressure on the exterior of the bit and the lesser pressure on the interior of the cutter effective to urge the sealing ring toward the cutter.

6. In a roller cut-ter well drilling bit for operation in a drilling fluid under pressure, a body having a journal on which a roller cutter is rotatably mounted, said body presenting an annular tapered surface tapering toward an adjacent face on the cutter, an endless elastic sealing ring disposed in stretched condition on said tapered surface and crowded toward the mentioned face on the cutter by its effort to contract, and means for producing fluid pressure in the cutter inwardly of the sealing ring less than that of the drilling fluid on the exterior of the cutter and which is effective on the exterior of the sealing ring.

7. In a roller cutter well drilling bit for operation in a drilling fluid under pressure, a body having a journal on which a roller cutter is rotatably mounted, said body presenting an annular tapered surface tapering toward an adjacent face on the cutter, an endless elastic sealing ring disposed in stretched condition on said tapered surface and crowded toward the mentioned face on the cutter by its effort to contract, means providing a passage in the body between the exterior of the body and the interior of the cutter inwardly of the sealing ring, a spring-urged piston in said passage, the spring of the piston being arranged to oppose the transmission of drilling fluid pressure from the exterior of the body through said passage to the interior of the cutter, and said passage, between said piston and said sealing ring, being adapted to hold fluid lubricant.

8. In a roller well drilling bit for operation in a drilling fluid under pressure, a body having a journal on which a roller cutter is rotatably mounted, an endless sealing ring on the body engageable with a face on the cutter to seal therewith under the influence of greater pressure on the exterior of the bit than in the interior of the cutter, there being a fluid lubricant passage in the body leading from the exterior thereof to the interior of the cutter inwardly of the sealing ring, and spring-actuated means in said passage for partially transmitting fluid pressure from the exterior of the bit to the interior of the cutter, the spring being arranged to oppose the transmission of fluid pressure whereby the pressure maintained in the interior of the cutter will be less than that on the exterior of the bit and the net effective pressure on the sealing ring will 'be effective to urge it into sealing engagement with the face on the cutter.

References Cited by the Examiner UNITED STATES PATENTS Scott 175228 Green 3088.2 Derman 277-95 X Skupas 27795 X

Claims

2. IN A ROLLER CUTTER WELL DRILLING BIT, A BODY PART HAVING A JOURNAL AND A CUTTER PART ROTATABLY MOUNTED THEREON, ONE OF SAID PARTS HAVING AN ANNULAR TAPERED SURFACE TAPERING TOWARD THE OTHER AND DISPOSED ADJACENT A FACE ON THE OTHER, AND AN ANNULAR ELASTIC SEALING RING STRETCHED ONTO SAID SURFACE ON SAID PART WHICH BY REASON OF ITS CONTRACTION WILL CROWD ITSELF TOWARD THE OTHER TO FORM SEALING ENGAGEMENT THEREWITH, AND MEANS FOR CAUSING A DIFFERENTIAL IN HYDROSTATIC PRESSURE TO EXIST BETWEEN THE EXTERIOR OF THE BIT AND THE INTERIOR OF THE CUTTER PART WITH THE GREATER PRESSURE ON THE EXTERIOR OF THE BIT AND THE LESSER PRESSURE