GB2034786A - Earth boring bit - Google Patents

Abstract

A three cone rock bit includes a thrust bearing system in which the inner journal surface 47 of each cone cutter is formed with an eccentric groove 49 filled with a soft metal anti- galling agent 48. The cooperating journal surface 46 of the bearing pin may be formed with a groove 50 co- axial with the bearing pin and filled with a wear resistant hardmetal. The eccentricity of the groove 49 causes the anti-galling metal to wipe the bearing surface 46 as the cone cutter rotates. <IMAGE>

Description

SPECIFICATION Earth boring bit The present invention relates in general to the art of earth boring and more particularly to a rotary rock bit having a thrust flange bearing surface with an eccentrically formed groove filled with an antigalling material.

A rotary rock bit consists of a main bit body adapted to be connected to a rotary drill string.

The bit includes individual rotatable cone cutters mounted on individual bearing pins extending from the main bit body. Bearing systems are provided between the cone cutters and the bearing pins to promote rotation of the cutters and means are provided on the outer surface of the cone cutters for disintegrating the earth formations as the bit and the cutters rotate. In order to obtain high penetration rates with a rotary rock bit in some formations, it is necessary to apply heavy loads on the bit and to operate the bit at a moderate speed. With other formations only moderate loads are required, but the bit must be operated at relatively high speeds. The rotary rock bit operates under a highly corrosive environment and is subjected to temperature extremes. The drilling operation is often conducted thousands of feet underground wherein elevated temperatures are encountered.The bit is continually flushed by circulating drilling fluid to cool the bit and carry away the drill cuttings. This fluid is generally water with chemicals added to control water loss or to control viscosity and/or PH. These chemicals may produce a corrosive drilling fluid. The drill cuttings, the materials encountered in the earth formations, barites added for fluid weight control, and the chemical composition of the drilling fluid combine to create a corrosive and abrasive drilling environment. In view of the previously explained circumstances, it can be appreciated that a bearing system for a rotary rock bit must be constructed so that it will include exceptional performance characteristics within a limited geometrical configuration.Since the entire drill string must be withdrawn to replace a bit should it fail, it is highly desirable to have the bearing system of the bit operate for an extended period of time.

The development of journal bearing rotary rock bits has included the use of matched radial surfaces as thrust bearing surfaces. One of these radial surfaces is the innermost surface of the bearing configuration known as the journal inner flange and usually contains a circular groove surrounding the appendage known as the pilot pin.

Said circular groove is usually filled with a hardmetal which has a demonstrated ability to withstand wear. The matching radial surface in the cone cutter surrounds the pilot pin recess or pilot bushing recess and may be carburized or noncarburized steel or may contain various indentations such as slots or drilled recesses containing a relatively soft alloy metal such as berylium copper or aluminum bronze to form a bearing pair with hardmetal against soft metal.

In U.S. Patent No. 3,235,316 to J. R. Whanger, patented February 1 5, 1 966, a journal bearing for a rock bit is shown with alternating surface areas of wear-resistant and anti-galling materials. The bearing system disclosed in this patent includes grooves in one of the rotatable members with a soft metal having anti-galling characteristics positioned in the groove.

According to the present invention there is provided an earth boring bit, comprising: an earth boring bit body; a bearing pin extending from said bit body; a rolling cutter mounted on said bearing pin; cooperating thrust bearing surfaces on said bearing pin and rolling cutter; an eccentric groove in one of said thrust bearing surfaces; and an antigalling material in said groove.

The invention will be better understood from the following description of preferred embodiments thereof, given by way of example only, reference being had to the accompanying drawings, wherein: FIGURE 1 is a sectional view of one arm of an embodiment of earth boring bit constructed in accordance with the present invention; FIGURE 2 is a view of the thrust flange of the cone cutter of the bit shown in Figure 1; and FIGURE 3 illustrates another embodiment of the present invention.

Referring now to Figure 1, a sectional view of one arm 13 of a three cone rotary rqck bit 10 is shown, It is to be understood that the structures of the other two arms are substantially identical to the arm 13. A cutter 1 4 is rotatably positioned on the journal position or bearing pin 18 of the arm 1 3 and adapted to disintegrate the earth formations as the bit 10 is rotated. The cutting structure 1 5 on the surface of cutter 14 contacts and disintegrates the formations in a manner that is well known in the art. The cutting structure 1 5 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 1 4.

The body of the bit 10 includes an upper threaded portion that allows the bit 10 to be connected to the lower end of a rotary drill string (not shown). The bit 10 also includes a central passageway extending along the central axis of the bit to allow drilling fluid to enter from the upper section of the drill string (not shown) immediately above and pass downward to the bottom of the well bore to flush cuttings and drilling debris from the well bore.

A plurality of bearing systems are located in the bearing area between the cutter 14 and the bearing pin 1 8. The bearing systems in the bearing area include an outer friction bearing 19, a series of ball bearings 20, an inner friction bearing 21, and a thrust button 22. An O-ring seal 23 is positioned between the cutter 14 and the bearing pin 18. 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. A passageway 24 allows the balls that make up the ball bearing system 20 to be inserted into position after the cone cutter 1 4 is placed on the bearing pin 18. The series of ball bearings 20 serves to lock the cone cutter 1 4 on bearing pin 18.After the balls are in place, a plug 25 is inserted into the passageway 24 and welded therein by weld 26. Plug 25 has a reduced diameter throughout the major portion of its length to allow lubricant to flow through the passageway 24.

A cylindrical reservoir chamber 26 is located in the bit body 11. A lubricant reservoir 27 containing a suitable lubricant is positioned in the lubricant reservoir chamber 26. The lubricant reservoir 27 consists of a lubricant reservoir canister 28 with a flexible diaphragm 29 attached.

A vent passage 30 allows the pressure of the fluid in the borehole to be transmitted to the outside of the flexible diaphragm 29. A passage 35 extends from the lubricant reservoir 27 to the bearing area between the cutter 14 and the bearing pin 18.

Lubricant in the lubricant reservoir 27 can flow through the passage 35 to the bearing area.

Development of journal bearing rock bits has included the use of matched radial surfaces as thrust bearing surfaces. One of these radial surfaces is the innermost surface of the bearing configuration known as the journal inner flange and usually contains a circular groove surrounding the appendage known as the pilot pin. Said circular groove is most usually filled with a hardmetal which has a demonstrated ability to withstand wear. The matching radial surface in the cone surrounds the pilot pin recess or pilot bushing recess and may be carburized or noncarburized steel; or may contain various indentations such as slots, or drilled recesses containing a relatively soft alloy metal, such as berylium copper or aluminum bronze to form a bearing pair with hardmetal against soft metal.As shown in Figure 1, a thrust flange surface 32 on bearing pin 18 engages a thrust flange surface 33 on the inside of cone cutter 14.

Referring now to Figure 2, an end view of the rolling cone cutter 14 is illustrated. The present invention prevents or reduces wear and/or galling between cone cutter 14 and the bearing pin 18 thrust surfaces 32 and 33. An eccentrically formed groove 37 in the cone bearing thrust surface is filled with an anti-galling material to produce an anti-galling dry lubricant medium. The circular groove in the cone thrust surface formed eccentrically around the cone centerline provides a wiping action and deposits the anti-galling material across the face of the arm thrust surface as an anti-galling medium or dry lubricant.

Referring now to Figure 3, a sectional view of a bearing pin 38 and cutter 39 of a three cone rotary rock bit 40 incorporating another embodiment of the present invention is shown. The cutter 39 is rotatably positioned on the journal portion or bearing pin 38 and adapted to disintegrate the earth formations as the bit 10 is rotated. A plurality of bearing systems are located in the bearing area between the cutter 39 and the bearing pin 38. The bearing systems in the bearing area include an outer friction bearing 41, a ball bearing system 42, an inner friction bearing 43, and a thrust button 44. An O-ring seal 45 is positioned between the cutter 39 and the bearing pin 38. 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.

A thrust flange surface 46 on bearing pin 38 engages a thrust flange surface 47 on the inside of cone cutter 39. The present invention prevents or reduces wear and/or galling between cone cutter 39 and the bearing pin 38 thrust surfaces 46 and 47. A circular groove 49 in the cone cutter radial surface 47 is provided of sufficient depth to contain an anti-galling material. The groove 49 is approximately one-half the width of the matching hardmetal filled groove 50 contained in the inner flange 46 of the journal 38. The centerline of the circular anti-galling material filled groove 49 in the cone radial surface 47 is offset from the centerline of the bearing pin 38 approximately one-half the width of the matching, hardmetal filled groove 50 in the inner flange 46 of the journal 38 to provide an eccentric, wiping action, and concurrent support by the cone cutter parent steel. The anti-galling material 48 contained in the eccentric groove 49 of the cone radial surface 47 will serve continuously as a dissimilar bearing pair during normal lubrication with petroleum type lubricants contained within the bearing envelope and will serve as a dry lubricant during periods in which extreme thrust pressure has eliminated petroleum type lubricant from between the two radial thrust surfaces 46 and 47. The anti-galling material may be of a soft metal such as aluminum bronze or berylium copper.

Claims (9)

1. An earth boring bit, comprising: an earth boring bit body; a bearing pin extending from said bit body; a rolling cutter mounted on said bearing pin; cooperating thrust bearing surfaces on said bearing pin and rolling cutter; an eccentric groove in one of said thrust bearing surfaces; and an antigalling material in said groove.

2. An earth boring bit according to claim 1 wherein said thrust bearing surfaces are radial surfaces.

3. An earth boring bit according to claim 1 or claim 2 wherein said thrust bearing surface on the bearing pin is the journal inner flange of the bearing pin.

4. An earth boring bit according to any preceding claim wherein the other of the thrust bearing surfaces has a groove co-axial with the bearing pin, the groove being filled with a wear resistant hardmetal.

5. An earth boring bit according to any preceding claim wherein the anti-galling material is a soft metal.

6. An earth boring bit according to claim 5 wherein the soft metal is aluminum bronze or berylium copper.

7. An earth boring bit according to any preceding claim wherein the said one of said bearing surfaces is the bearing surface of the rolling cutter.

8. An earth boring bit according to any preceding claim wherein the or each groove is circular.

9. An earth boring bit, substantially as hereinbefore described with reference to and as shown in the accompanying drawing.