GB2380500A

GB2380500A - Rotary cone bit with thrust bearing

Info

Publication number: GB2380500A
Application number: GB0215327A
Authority: GB
Inventors: Sr Daniel W Varel
Original assignee: Varel International Inc
Current assignee: Varel International Inc
Priority date: 2001-10-05
Filing date: 2002-07-03
Publication date: 2003-04-09
Also published as: JP2003176683A; CA2394212A1; GB0215327D0; ITRM20020487A0

Abstract

A rotary cone bit comprises a drill bit body having two or more leg portions 14 extending from one end of the drill bit body. Formed integrally with each of the leg portions is a bearing pin that extends inwardly toward the longitudinal axis of the drill bit body and includes a circumferential shelf 140 formed proximal to the distal end of the pin. On each of the bearing pins there is rotatably mounted a cutter cone that includes an internal shelf 150 formed to mate with the circumferential shelf 140 of a respective bearing pin 40. Positioned between the circumferential shelf 140 of the bearing pin and the internal shelf 150 of the cutter cone is a thrust bearing 100 having a plurality of cylindrical rollers 120 positioned in a retainer ring 110. The thrust bearing 100 transfer forces generated on the cutter cone by conventional drilling action to the distal end of the bearing pin.

Description

ROTARY CONE BIT WITH IMPROVED THRUST BEARING TECHNICAL FIELD OF THE INVENTION The present invention relates to rotary cone bits and, in particular, to a rotary cone bit having an improved thrust bearing.

BACKGROUND OF THE INVENTION Rotary cone bits are well known in the art of drilling. The most common design of a rolling cone bit consists of three generally conical shaped cutters each rotatably mounted on a downwardly extending bearing pin.

Each of the bearing pins is spaced approximately 120 degrees apart with the three pins mounted to a bit body. The entire structure is rotated at the end of a drill string. Boring is accomplished by applying weight to the drill bit and rotating it, thereby causing the cutters to roll and crush the rock formation beneath the bit. The load on each cutter is supported by the bearing the cutter is mounted on.

Two bearing types are most commonly employed in rolling cutter rock bits.

These are the friction, or journal type and the anti-friction, or roller type bearing. Designs utilizing friction bearings include a seal to contain lubricant required for proper operation of the bearing and exclude drilling fluid and other products of the environment outside the bearing. Antifriction bearings may or may not have a seal similar to friction type bearings.

Anti-friction bearings as commonly employed in drill bits have rolling elements designed to support the loads arising from drilling weight applied on the bit. These rolling elements support the component of the load which is normal to the axis of rotation of the cutter. The remaining component of the load, that is, the component directed along the axis of rotation of the cutter, is not supported by the rolling elements. This axial component is

supported by various friction elements. These frictional elements wear more rapidly and generate more heat than the anti-friction elements supporting the radial, or normal load. The useful life of these frictional elements is therefore shorter than that for the anti-friction rolling elements.

This imbalance in life for the various bearing elements gives rise to an opportunity for improvement in anti-friction bearing design.

A need exists for increasing the thrust, or axial bearing life in relatively large diameter three cone rotary bits. Both cylindrical and tapered rollers have been unsuccessfully tested as thrust bearings. Cylindrical rollers, when employed as thrust elements, are forced to roll in a circle, causing sliding along the length of the roller which results in rapid and excessive wear. Tapered rollers are difficult to align with mating parts making production difficult and costly. A need exists for the improved thrust bearing of the present invention.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an improved rotary cone bit including a drill bit body having two or more leg portions extending from one end of the drill bit body. Formed integrally with each of the leg portions is a bearing pin that extends inwardly toward the longitudinal axis of the drill bit body. On each of the journal pins there is rotatably mounted a cutter cone having rows of cutting teeth as a part thereof.

Further, the improved rotary cone bit of the present invention includes on each of the bearing pins a circumferential shelf formed proximal to the distal end of the pin. In addition, each of the cutter cones includes an internal shelf formed to mate with the circumferential shelf of a respective bearing pin. Positioned between the circumferential shelf of the bearing pin and the internal shelf of the cutter cone is a thrust bearing having a plurality of cylindrical rollers positioned in a retainer ring. The thrust

bearing transfers forces generated on the cutter cone by conventional drilling action to the distal end of the bearing pin.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of a rotary cone bit with an improved thrust bearing of the present invention may be had by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: Figure 1 is a perspective view of a rotary cone bit with an improved thrust bearing; Figure 2 is a section view illustrating the thrust bearing assembly of the present invention as employed in a friction bearing rotary cone bit; Figure 3 is a perspective view of the thrust bearing of the present invention; and Figures 4A and 4B are partial section views, taken along the lines 4A-4A and 4B-4B, respectively, of FIGURE 3, illustrating the thrust bearing assembly of the present invention as employed in a roller- bearing rotary cone bit.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention there is provided a rotary cone bit having an improved thrust bearing. The rotary cone bit of the present invention includes a bit body having a central vertical axis and a shank for connection to a drill string. The shank is formed on one end of the bit body and includes a central vertical axis co-axial with the central vertical axis of the bit body.

Three legs extend from a second end of the bit body. A bearing pin is attached to each of the three respective legs and extends inwardly and downwardly approximately toward the central vertical axis of the bit body. Each bearing pin includes a circumferential shelf disposed on the pin proximal to the distal end.

A rolling cutter is rotatably mounted on each respective bearing pin and includes an internal shelf for mating with the circumferential shelf of the respective bearing pin.

In accordance with the present invention, thrust bearings are positioned between, and in rotating contact with, the circumferential shelf of each respective bearing pin and the internal shelf of each respective rotating cutter. Each thrust bearing includes a disk shaped retainer ring having a central opening, and a plurality of apertures disposed circumferentially about the retainer ring. The thrust bearing further includes a plurality of cylindrical rollers positioned in the apertures of the retainer ring. The cylindrical rollers are assembled in sliding contact with the adjacent rollers and typically have an L/D ratio of less than" 1". A retaining ring holds the cylindrical rollers in the apertures of the retainer ring. The central opening of each thrust bearing receives the distal end of each respective bearing pin.

Reference is now made to the drawings wherein like reference characters denote like or similar parts throughout the four Figures. Referring now to FIGURE 1, there is shown a rotary cone bit including a bit body 10 having at one end a threaded shank 12 for attachment to a drill string member (not shown). The shank portion 12 is adapted to be threadedly engaged with a drill string in accordance with conventional drill bit construction.

Extending from the bit body 10 are three leg portions 14 providing support for rotatable roller cutter cones 16. Both the bit body 10 and the shank 12 have an axially extending hollow passage to permit drilling fluid to flush the bore hole of debris during the drilling operation. The passage

terminates at nozzles 20 positioned between each of the three cones in accordance with conventional drill bit construction.

As illustrated in Figure 1, the roller cutter cones 16 have substantially the same base diameter to permit the cutting teeth on each cone to project between the cutting teeth of the other cutter cones. The cutting teeth 22 on each of the cutter cones 16 are arranged in rows and in the embodiment shown comprise tungsten carbide inserts pressfit into the cone surface and projecting therefrom. Each of the cutter cones 16 is also provided with gage row teeth 24 such as carbide inserts press fit into the cone surface and projecting therefrom.

The cutter cones 16 are journaled on respective leg portions 14 for rotation about a rotational axis of a bearing pin. This axis of rotation is inclined with respect to the vertical axis of the bit in accordance with conventional roller cone cutter techniques.

The bearing structure and seal assembly for each of the cutter cones 16 is of a conventional design.

Referring to Figure 2, there is shown a sectional view of a rotary cone bit of the present invention. Included as part of the leg portion 14 supporting the cutter cone 16 is a lubrication system including a passage 34 terminating in a lubrication reservoir. The passage 34 communicates with a passage 38 having an opening into the cavity formed between the journal pin 40 and the inside surface of the cutter cone 16. A sleeve bearing 46 rotatably supports the cutter cone 16 on the bearing pin 40. In an annular groove formed by assembly of the cutter cone 16 onto the bearing pin 40 there is provided seals 48 and 49 to restrict the inflow of abrasive particles to the bearing surface between the bearing 46 and the bearing pin 40. Also assembled onto the bearing pin 40 is a wear ring 50. Each bearing pin 40 includes a journal bearing race 53 extending circumferentially around the

pin 40. A similar bearing race 55 is formed within a cylindrical aperture in the cutter cone 16. The cutter cone 16 is positioned so that the bearing races are aligned when the cutter cone 16 is assembled on the bearing pin 40. Ball bearings 54 are assembled into the cavity created by alignment of the bearing race 53 with the bearing race 55 to rotatably secure the cutter cone 16 on the journal pin 40. The ball bearings 54 are placed in the cavity through an aperture not shown) in the bit body. Upon filing the passage 38 with ball bearings 54 a plug is welded in the aperture to secure the ball bearings in the cavity.

Extending from the surface of the cutter cone 16 are a plurality of cutting teeth 22 that as explained previously project between the cutting teeth of the adjacent cutter cone 16. Positioned along the gage row of the cutter cone 16 are gage teeth 24 that also project from the surface of the body of the cone. As illustrated, the general configuration of the cutter cone 16 is hemispherical and has a base diameter measured at the gage row.

A thrust bearing 100 is positioned between and in rotating contact with a circumferential shelf 140 of the bearing pin 40 and an internal shelf 150 of the cutter cone 16. Additionally, circumferential shelf 140 and internal shelf 150 may be hardened for wear resistance.

Referring now to Figure 3, there is illustrated a perspective view of the thrust bearing 100 of the present invention. Each thrust bearing includes a disk shaped retainer 110 having a central opening 115, and a plurality of apertures 117 disposed circumferentially around the retainer. The thrust bearing 100 further includes a plurality of adjacent cylindrical rollers 120 positioned in each of the apertures 117 of the retainer 110. In a preferred embodiment of the invention the L/D ratio (length-to-diameter) of the rollers in equal to or less than one. A retaining ring 122 encircles the retainer 110 to hold the cylindrical rollers 120 in the apertures 117.

Referring to Figure 4A and 4B, there is illustrated two section views

of the thrust bearing 100 as illustrated in Figure 3. The adjacent cylindrical rollers 120 in each of the apertures 117 is not actually supported. That is, the cylindrical rollers 120 rotate in the apertures 117 without actual support, thereby allowing a measure of lateral movement as a cutter cone 16 rotates about a respective leg portion 14.

As best illustrated in Figure 4B, the apertures 117 have curved sides 124 having a radius of curvature corresponding with the radius of curvature of the cylindrical rollers 120. The curved surfaces 124 retain the cylindrical rollers 120 in the respective aperture 117 to float without axial support.

This improved the effect of the thrust bearing 100 as the cutter cones 16 rotate on a respective leg portion 14.

During drill bit operation, the thrust bearing 100 carries the axial and thrust loads placed on the bit. The plurality of cylindrical rollers 120 rotate independently of each other. By rotating independently, cylindrical rollers 120 minimise sliding wear on the circumferential shelf 140 and the internal shelf 150.

Although several embodiments of the invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed but is capable of numerous modifications without departing from the scope of the invention as claimed.

Claims

CLAIMS 1. An improved rotary cone bit comprising: a drill bit body having two or more leg portions extending from an end of the bit body, and a plurality of bearing pins, one each attached to a respective leg portion of the bit body, each bearing pin extending inwardly; a plurality of cutter cones, one each of said cones journaled to rotate on a respective bearing pin; a circumferential shelf formed on each of the bearing pins proximal to the distal end; an internal shelf formed in each cuter cone for mating with the circumferential shelf of said bearing pin; and a plurality of thrust bearings each including a disk shaped retainer having a plurality of cylindrical rollers positioned in the retainer, each of said thrust bearings positioned between the circumferential shelf of a respective bearing pin and the internal shelf of a respective cutter cone.
2. The rotary cone bit of claim 1 wherein each of the plurality of thrust bearings includes a plurality of adjacent cylindrical rollers positioned in the retainer circumferentially about the retainer.
3. The rotary cone bit of claim I or claim 2 further including a face hardened bearing surface on the circumferential shelf of each bearing pin.
4. The rotary cone bit of any one of claims 1 to 3 further including a face hardened bearing surface on the internal shelf of each cutter cone.
5. An improved rotary cone bit, wherein the rotary cone bit includes: a bit body having: a central vertical axis, three leg portions extending from an end of the bit body, each of said leg portions spaced around the bit body, each leg

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portion having an outside disposed away from the central vertical axis of the bit body and inside disposed toward the central vertical axis of the bit body, and three bearing pins, one each attached at a first end to the inside of each respective leg portion of the bit body and extending inwardly toward the central vertical axis of the bit body, each bearing pin having a rotational axis extending in a direction of the central vertical axis of the bit body, and each bearing pin further including a circumferential shelf formed on each of the bearing pins proximal to the distal end of the bearing pin; three cutter cones, one each of said cones journaled to rotate on a respective bearing pin, each of said cutter cones including an internal shelf formed in each cutter cone for mating with the circumferential shelf of said bearing pin; and three thrust bearings each including: a disk shaped retainer having a plurality of adjacent cylindrical rollers positioned in the retainer and disposed circumferentially about the retainer, each of said thrust bearings positioned between, and in rotating contact with, the circumferential shelf of each respective bearing pin and the internal shelf of a respective cutter cone.
6. The improved rotary cone bit of any preceding claim wherein the disk shaped retainer further includes: a plurality of apertures disposed circumferentially in a row with the plurality of cylindrical rollers adjacently positioned in the apertures, and a retaining ring encircling the retainer to hold the plurality of cylindrical rollers in the respective aperture.

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7. A rotary cone bit, comprising: a bit body having: a central vertical axis, a shank for connection to a drill string, said shank formed on a first end of the bit body and including a central vertical axis co-axial with to the central vertical axis of the bit body, three leg portions extending from a second end of the bit body and spaced around the bit body, each leg portion having an outside disposed away from the central vertical axis of the bit body and inside disposed toward the central vertical axis of the bit body, and three bearing pins, one each attached at a first end to the inside of a respective leg portion of the bit body and extending inwardly toward the central vertical axis of the bit body, each bearing pin having a circumferential shelf formed proximal to the distal end of the bearing pin; three cutter cones, one each of said cones journaled to rotate on a respective bearing pin and including cutting teeth extending from the surface thereof, each of said cutter cones having an internal shelf formed in each cutter cone for mating with the circumferential shelf of said bearing pin; and three thrust bearings each including : a disk shaped retainer having a central opening, a plurality of apertures disposed circumferentially in a row about the retainer, a plurality of adjacent cylindrical rollers positioned in the apertures of the retainer ring, each of said thrust bearings positioned between, and in rotating contact with, the circumferential shelf of a respective bearing pin and the internal shelf of a respective cutter cone and the central opening of each thrust bearing receives the distal end of a respective bearing pin.
8. A rotary cone bit substantially as described with reference to the accompanying drawings.