Excavating tool

Abstract

An excavating tool, especially for forming holes in earth formations for receiving pipes, and in which the excavating tool includes, at the working end, a tiltable member so that, after a pipe receiving hole is formed, a pipe can be introduced into the hole and through the opening provided by the tiltable portion on the bit thereby permitting the bit to be retrieved.

Description

The present invention relates to excavating tools and is particularly concerned with a bit arrangement especially adapted for use in connection with an excavating tool for forming holes in earth formations and the like for receiving pipes.

The forming of holes in earth formations for receiving pipes is a well known work procedure that is generally carried out by utilizing a tubular drill string having a bit on the outer end. The bit and drill string are rotated and advanced into the formation and a hole is thereby formed in the formation.

Usually, the bit is not retrievable but is, instead, disengaged from the drill string by rotating the drill string in the reverse direction. The bit in such a case is left in the hole and the pipe is inserted, usually, through the drill string before the drill string is retracted from the hole.

The act of leaving a bit in the hole each time represents considerable expense, and it is proposed by the present invention to construct a bit for the aforesaid purpose which will permit a pipe to be introduced directly through the bit into the hole whereby retraction of the drill string from the hole will also recover the bit so that the bit can be used again.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, a bit structure is provided adapted for being threaded on the end of a drill string, or for being welded or otherwise affixed to the end of a drill string or to a short piece of drill pipe. The bit is provided with cutters mounted thereon which determine the size of the hole to be formed. The cutters protrude radially outwardly slightly from the envelope of the drill pipe and, thus, permit the drill pipe to follow readily into the hole being formed as the bits reduce the formation.

The residue taken by the bit can be flushed rearwardly along the outside of the drill string so that the bit and drill string can proceed into the formation. According to the present invention, the bit comprises a central hole through which flushing liquid, water, for example, can pass to the bit and through which a pipe to be introduced into the formed hole can be fed after the hole is completely formed.

The bit includes a bar portion extending transversely across the central opening or hole in the bit structure and which bar portion is pivotally connected to the outer part of the bit structure at one end of the bar portion. The bar portion includes at least a centrally disposed pilot cutter and may include other cutters radially outwardly from the pilot cutter.

Due to the tiltable bar overlying the central opening in the bit, the pipe to be placed into the hole that is formed by the bit and drill string can be introduced through the drill string and the central opening in the bit structure by outward tilting of the aforementioned bar and whereupon the drill string, together with the bit, is withdrawn from the hole thereby recovering the bit for further use.

The exact nature of the present invention will become more apparent upon reference to the following specification taken in connection with the accompanying drawings in which:

FIG. 1 is a side view of one form which the invention can take.

FIG. 2 is a plan view of the FIG. 1 modification with the circumferential cutters shown on the bit structure.

FIG. 3 is a plan view similar to FIG. 2 but shows a bit structure for forming a relatively large hole.

FIG. 4 is a side view of the modification of FIG. 3 and partly broken away to show the construction thereof.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings somewhat more in detail, the bit device shown in FIG. 1 comprises an annular bit body 10 having a central opening or hole 12 extending therethrough and which advantageously tapers outwardly as at 14 in a direction toward the rear of the bit body.

The bit body is advantageously formed from the rear so that it can be seated on a pipe 16 and welded thereto as by welding 18. Pipe 16 may be furnished with the bit, or it may comprise a length of drill pipe and is threaded at the end opposite bit body 10 by threads 20 for connection thereof to another length of drill pipe.

Bit body 10, as will best be seen in FIG. 2, has a plurality of support blocks 22 distributed thereabout, and in each block, there is rotatably mounted a pick type cutter 24. The cutters 24 are of a known type as are the blocks 22 and are inclined on the bit body at various angles so as to reduce a substantial radial portion of a formation to which the bit is rotatably presented and including that part of the formation lying radially outside the envelope of the bit body and the drill string. The bits and blocks have not been shown in FIG. 1 for the sake of clarity but the location and angular disposition thereof will be clear from FIG. 2.

A particular feature of the bit according to the present invention resides in the bar 26 extending diametrally across central opening 12 of the bit body and tiltably connected to the bit body at one end as by pin 28. Bar 26 in the center thereof includes a pilot cutter element 30 and which may consist, for example, of a transversely extending blade formed of a hard wear resistant material such as cemented tungsten carbide.

When the bit is presented to a formation and rotated and advanced into the formation, the rotatable cutter bits 24 and the central pilot cutter 30 reduce the formation and the resulting debris can be removed from the hole by forcing flushing fluid such as water through the drill string and bit and withdrawing the debris along the outside of the drill string.

When a hole is formed to the desired extent by rotating the bit and drill string while advancing the bit and drill string into the formation, a pipe 32 which it is desired to place in the hole can be introduced axially through the drill string and, at that time, the central transverse bar 26 will tilt upwardly, as shown in dotted outline in FIG. 1, and permit the pipe to pass through the bit while, more importantly, permitting the bit, together with the drill string, to be withdrawn from the hole leaving pipe 32 in the hole.

It will be understood that, where the bit is resting on the bottom of a hole that has been drilled, it will be necessary to retract it slightly from its fully advanced position to permit bar 26 to tilt upwardly. However, this still permits the pipe 32 to be introduced substantially to the bottom of the hole formed while permitting the drill string and bit to be retracted as a unit from the hole, leaving pipe 32 therein.

The bit arrangement shown in FIGS. 3 and 4 comprises an annular member 40 forming the bit body and distributed about annular member 40 is a plurality of blocks 42 each having rotatably mounted therein a pick type cutter element 44. The blocks and cutters are shown in particular in developed form in FIG. 4 and illustrate that the radial range of the cutters is such as to reduce the formation into which the bit is moved to permit clear passage for the bit body and, therefore, for the drill string to which the bit body is connected.

In the case of the modification of FIGS. 3 and 4, the transverse bar extending across the central opening 46 of the bit, said bar being indicated at 48, carries not only a central cutter 50, but also has pick type cutters 52 mounted thereon on each side of the central cutter. In this manner, the material through which the bit is being moved is reduced completely across the diameter of the bit body and the removed material can readily be withdrawn along the outside of the drill string.

Central bar 48, similar to bar 26 of FIGS. 1 and 2, is pivotally connected by a pin 54 to the bit body so that the bar 48 can tilt upwardly from its working position and thereby permit a pipe to be introduced directly through the bit before the bit and drill string are withdrawn from the hole.

Thus, in the case of the modifications of FIGS. 3 and 4, a bit can readily be recovered from the hole which it forms while, at the same time, permitting the pipe to be introduced into the hole before the drill string is withdrawn therefrom.

In the case of either of the modifications illustrated, the savings in bit costs are substantial, while no loss in drilling efficiency and no loss of time is encountered in forming a hole and placing a pipe therein.

The bit body of FIGS. 1 and 2 has the axially extending diametrally opposed notches 60 and 62 to receive the ends of bar 26 while the bit body of FIGS. 3 and 4 has the notches 64 and 66 for the same purpose. The notches are effective for transmitting torque from the bit body to the respective bar while the notch at the free end of the bar also provides an abutment region to bolt the bar in the proper diametral position during a hole forming operation.

The pick type cutters have been shown mounted in support blocks and held therein as by snap rings but it will be evident that the bit bodies could be formed with holes to receive the cutters and the cutters held therein as by captive keepers. U.S. Pat. No. 3,752,515 shows a captive keeper arrangement of the nature referred to while U.S. Pat. No. 3,650,565 shows the use of a snap ring as a keeper. Each of the patents shows cutters of the type illustrated herein.

Modifications may be made within the scope of the appended claims.

Claims

What is claimed is:

1. In an excavating tool; an annular bit body having a central opening therethrough, an end portion extending from one end of said body smaller in diameter than the bit body and adapted for coaxial extension inside a tubular member to be fixedly held there for rotation on a central axis, the central opening in said end portion flaring out toward the free end thereof, cutters mounted on and protruding axially from one axial end of said body for reducing a formation into which the tool is advanced while rotating, a bar element extending transversely on said one end of said body, pivot means pivotally connecting one end of said bar element to said body and cooperating elements of abutment means on the other end of said bar element and said body, said abutment means supporting said bar element during excavating operations and said pivot means permitting outward pivotal movement of the bar element to expose said central opening, and cutter means on said bar element for reducing the formation radially inwardly from said cutters on said one end of said body.

2. An excavating tool according to claim 1 in which said cutters on said body comprise pick type cutters rotatable on the respective axes thereof and all tilted on the bit body in the same circumferential direction.

3. An excavating tool according to claim 1 in which said cutter means on said bar element includes a spade-type cutter on the center of the bar element.

4. An excavating tool according to claim 1 which includes means on the other side of said bit body for threaded connection thereof to a tubular drill string.

5. An excavating tool according to claim 1 in which the central opening on said bit body tapers outwardly in the direction toward the other side of said body.

6. An excavating tool according to claim 1 which includes a tubular member telescopically fitted over said extending end portion and coaxial therewith, said tubular member abutting the bit body at the base of said extending end portion.

7. An excavating tool according to claim 1 in which said bit body includes diametrally opposed axially extending radial notches in which the opposite ends of said bar element are disposed and operable for transmitting torque from the bit body to said bar element.

8. An excavating tool according to claim 1 in which said cutter means on said bar element includes cutter elements mounted on the bar element radially inwardly from the inner limits of said annular body and all thereof tilted on the bar element in the same circumferential direction.

9. An excavating tool according to claim 8 in which said bar element has a centrally located spade-type cutter thereon and the said cutter elements thereon being disposed on opposite sides of said spade-type cutter.