Drag Bits

Abstract

An earth drilling bit of the drag type is provided having a body with a plurality of radial slots at one end, each having a portion extending across said one end from the axis, a plurality of L-shaped wings removably fitted in said slots and held in place by resilient means extending through passages in the body and wings.

Description

This invention relates to drag bits and more particularly to a drag bit having replaceable wings for use in all forms of earth boring operations including drilling through the earth for oil, gas and the like as well as for drilling in mining and quarrying operations.

Earth boring bits are required to operate under greatly varied conditions.

These variables include the rock formations in which they are used, the types of rigs used to operate them, the rotational speeds, the vertical applied loads, the nature of the drill "string" and the drilling fluid used. The combined effects of all of these variables ultimately determines the drill life, the rate of penetration and the ability of the bit to drill through any given formation.

Drag bits are generally made with a body having radial wings extending from the body radially and axially. These wings are welded to the body or formed with the body to form a single unit. Generally the wings have a cylindrical surface on their outer edges that subtends a substantial circumferential arc. A typical construction of such a drag bit is shown in U.S. Pat. No. 3,140,748.

Drag bits of this prior art type are used until the effective diameter is reduced by wear after which they are discarded. There is a very substantial loss of money in the discarded body and unused wing area both in metal and lost machining. This discarded body cannot be used except as scrap.

In order to overcome this very significant loss, it has been proposed to provide an axial body portion to which are attached removable and replaceable wings. Typical of these bits are those illustrated in U.S. Pat. Nos. 2,978,049, 3,003,570 and 3,182,736. These drag bits with replaceable wings have not met with complete acceptance in the trade for a variety of reasons. First, they are too complex and thus costly to machine. Second, they are difficult to maintain because of their complex fastening systems. And third, they do not provide a sufficiently rigid base for the wing particularly against vertical loading.

I have invented a drag bit which eliminates the loss of discarded bodies and yet is very simple and inexpensive to make and maintain. I provide a main body and interchangeable wings which can be quickly removed and replaced with new wings using the same main body.

Preferably, I provide a drag bit adapted for rotation about its longitudinal axis comprising a main body, a plurality of radial slots at one end, extending across said one end from the axis and vertically upwardly along a portion of the sides of said body, a plurality of generally L-shaped wings removably fitted in said slots, a passage through each of said wings intermediate their ends, a like plurality of passages in said main body intersecting each of said slots at a point slightly axially offset from the passage in said wings when said wings are inserted in said slots and a resilient member extends through said passages to bias said wings into tight engagement with the slot and body, each wing extending radially beyond the body to provide a hole gauging portion and axially ahead of the said one end of the body to provide an end drilling face. Preferably, each wing has a forward face of generally planar form having a layer of hard alloy material secured to each forward face to provide hard cutting edges limiting wear on said forward faces. The resilient means extending through the passages in the body and wings are sprung steel roll pins.

In the foregoing general description, I have set out certain objects, purposes and advantages of my invention. Other objects, purposes and advantages of this invention will be apparent from a consideration of the following description and the accompanying drawings in which:

FIG. 1 is an end view of a drag bit body according to my invention;

FIG. 2 is a side elevation of the body of FIG. 1;

FIG. 3 is a section on the line III--III of FIG. 1;

FIG. 4 is a section on the like IV--IV of FIG. 1;

FIG. 5 is a side elevation of wing according to my invention;

FIG. 6 is an end elevation viewed from the right of FIG. 5;

FIG. 7 is an edge elevation of the view of FIG. 5;

FIG. 8 is an end view of a drag bit according to my invention;

FIG. 9 is a fragmental section on the line IX--IX of FIG. 10; and

FIG. 10 is a side elevation of a drag bit according to my invention.

Referring to the drawings, I have illustrated an elongated body 10 having a shank 11 which may be threaded internally or externally, provided with slots and steps or any other conventional means by means of which it can be attached to a drill string and rotated about its axis. The body end opposite the shank 11 is provided with a plurality of spaced apart grooves 12 which form between them spaced apart lands 13. Each land 13 is provided with a radial slot having a portion 14 extending along the length of the land and a portion 14a extending transversely across the end of the body opposite the shank to a central axial air passage 15. A hole 16 is drilled through each land 13 and through the slot 14. Angular air passages 17 are provided from the axial passage 15 to the grooves 12. The radial slot 14 and 14a is thus L-shaped with the two portions lying at approximately right angles.

A plurality of wings 20, one for each radial slot 14 and 14a are inserted in said slots and held in position by a spring steel roll pin 21 which passes through a hole 22 in the wing and hole 16 in the body. The hole 22 in each wing is slightly off center from the hole 16 in the body so that the roll pin biases the wing into tight engagement with the bottom portions of slot portions 14 and 14a. Each wing is provided with a multi-stepped portion 23 which extends axially ahead of the body portion to provide an end drilling face and with a radially outwardly extending portion 24 to provide a hole gauging face. The stepped portion 23 is preferably provided with cylinders 25 and 25a of cemented carbide one, 25, extending axially of the wing and bit, the other 25a extending diagonally. The face of the wing 20 which is the forward or cutting face is preferably provided with a longitudinal slot 26 and a transverse slot 27 into which are brazed small pieces of cemented carbide 29 and 30 respectively, or which is filled with some hard facing or cutting alloy to reduce the wear by abrasion during drilling.

It will be seen from the drawings that the wings in the bit of my invention are fully supported against vertical axial thrust by the groove 14a against which the edge 28 of the wing 20 abuts while edge 28a of wing 20 is engaged in slot 14. The roll pin 21 constantly biases the wing into tight engagement with the grooves 14 and 14a.

I have illustrated and described a presently preferred embodiment of my invention. However, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

Claims

I claim:

1. An earth drilling bit of the drag type adapted for rotation about its longitudinal axis comprising a body, a plurality of radial slots at one end having a portion extending across said one end from the axis, a plurality of L-shaped wings removably fitted in said slots, a passage through each said wings intermediate their ends, a like plurality of passages in said body intersecting each of said slots at a point axially offset from the passage in said wings when said wings are inserted in said slots and a resilient member extending through each of said passages biasing each of said wings in both a direction parallel to the longitudinal axis of the body and a direction transverse to the longitudinal axis of the body into tight engagement with the slot and body, each said wing extending radially beyond the body to provide a hole gauging portion and axially ahead of the said one end of the body to provide an end drilling face.

2. An earth drilling bit of the drag type as claimed in claim 1 wherein the resilient means is a spring steel roll pin.

3. An earth drilling bit of the drag type as claimed in claim 1 wherein the radial slot extends across said one end from the axis and vertically up the side of the body to form an L-shaped slot.

4. An earth drilling bit of the drag type as claimed in claim 1 wherein each wing has a forward face of generally planar form having a layer of hard abrasive resistant material secured to and over-laying said forward face to provide hard cutting edges.

5. An earth drilling bit of the drag type as claimed in claim 1 wherein the wings, in the portion extending ahead of the body, are in the form of stepped segments, the steps increasing in length ahead of the body from the axis outwardly.

6. An earth drilling bit of the drag type as claimed in claim 1 wherein each wing is a flat generally planar member having an L-shaped body engaging recess at one end and a plurality of stepped extensions at the other end forming a cutting edge extending ahead of said body.