US3920089A

US3920089A - Removable stem for raise bit

Info

Publication number: US3920089A
Application number: US449179A
Authority: US
Inventors: Howard Earl Mitchell
Original assignee: Dresser Industries Inc
Current assignee: Tamrock Canada Inc
Priority date: 1974-03-07
Filing date: 1974-03-07
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18
Also published as: CA1010846A; ZA75618B; ZM1475A1; AU7821675A

Abstract

A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole includes a removable drive stem. The removability of the drive stem allows the raise bit to be transported through small drifts and extends the useful lifetime of the raise bit. The raise bit body includes a multiplicity of rolling cutters for contacting and disintegrating the earth formations surrounding the pilot hole. A central opening extends through said raise bit body. One end of the drive stem extends into the central opening. A pair of flats is located near the end of the drive stem. A retaining element is positioned in the flats and is bolted to the raise bit body.

Description

United States Patent [19] Mitchell NOV. 18, 1975 REMOVABLE STEM FOR RAISE BIT [75] Inventor: Howard Earl Mitchell, Duncanville,

Tex,

[73] Assignee: Dresser Industries, lnc., Dallas, Tex.

[22] Filed: Mar. 7, 1974 [21 Appl. No.: 449,179

Justman 175/53 Primary Examiner-Frank L. Abbott Assistant E.\'aminer'Richard E. Favreau Attorney, Agent, or Firm-Eddie E. Scott ABSTRACT A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole includes a removable drive stem. The removability of the drive stem allows the raise bit to be transported through small drifts and extends the useful lifetime of the raise bit. The raise bit body includes a multiplicity of rolling cutters for contacting and disintegrating the earth formations surrounding the pilot hole. A central opening extends through said raise bit body. One end of the drive stem extends into the central opening. A pair of flats is located near the end of the drive stem. A retaining element is positioned in the flats and is bolted to the raise bit body.

5 Claims, 2 Drawing Figures U.S. Patent Nov. 18, 1975 3,920,089

REMOVABLE STEM FOR RAISE BIT BACKGROUND OF THE INVENTION This invention relates to the art of earth boring and more particularly to a raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole.

A relatively large diameter hole may be provided between a first location and a second location by an operation commonly referred to as raise drilling. The raise drilling operation begins by drilling a small diameter pilot hole through the earth from a first location to an opening at a second location using a small diameter pilot bit. After the pilothole is completed, the pilot bit is removed from the drill column and a larger diameter raise bit attached. The raise bit is rotated and drawn along the pilot hole thereby enlarging the pilot hole to the desired size. I

On many occasions, the small diameter pilot hole extends to an area accessible only through a small drift or passage. The removable drive stem of the present invention provides the raise bit with a low profile thereby allowing the raise bit to be transported through low drifts or passages. For example, a 72-inch diameter raise bit may be transported through a drift having a 30-inch height whereas a 72-inch diameter raise bit without the removable stern requires a drift with at least a 52-inch height.

During the raise drilling operation, a tremendous amount of wear and stress is imposed upon the raise bit. Generally, the pilot hole tends to wander which results in a series of curves over the length of the pilot hole. As the raise bit is drawn along the pilot hole, the drilling geometry changes. This results in a tremendous amount of stress being transmitted to the raise bit when it is being drawn through the curves. The outside radius of the raise bit may be many times greater than the radius of the pilot hole; therefore, the moment developed is great. When resistance is encountered by cutters located on the outer radius of the raise bit as when drilling along a curve, it causes increased stress on the raise bit. It can be appreciated that changes in formations encountered during the raise drilling operation complicates the above-mentioned conditions and adds to the drilling difficulties.

The tremendous stress and wear encountered during the raise drilling operation causes some elements of the raise bit to wear out much earlier than others, notably the cutters and the drive stem. The bit of the present invention allows the elements that have a relatively short lifetime to be replaced thereby extending the lifetime of the bit and reducing cost. The drive stem is removable and, therefore, replaceable as are the individual cutters. This allows the elements that receive the greatest stress and wear to be readily replaced. The relatively short lifetime of the individual cutters results from their nearly constant contact with the formations and the consequent exposure to wear and abuse. The drive stem also contacts the formations and receives a great deal of wear and abuse. The drive stem absorbs a large amount of stress since it is the single link between the drill column and the body of the bit. All energy from the rotary equipment is transmitted to the bit through the drive stem.

The drive stem is often subject to failure prior to failure of the body of the raise bit. It is, therefore, desirable to be able to easily and quickly remove the stem from the raise bit and replace it with a new stem. The stem is generally constructed of a high-strength heat-treated material and would be weakened by welding. It is, therefore, desirable to be able to attach and remove the stem from the raise bit body without welding. From the foregoing, it will be appreciated that the stem must be constructedof material that will stand up under the harsh conditions encountered. Such material is expensive and any reduction in the amount of this material used is cost savings. The bit of the present invention allows the stem to be manufactured from high-strength material, whereas the body may include lower strength and, therefore, less expensive materials.

The stem or a stabilizer section on the stem should be nearly the size of the pilot hole to insure a smooth raise drilling operation. In order to use the same bit body in pilot holes of different sizes, it is desirable to be able to remove the stem from the raise bit body and replace it with an appropriately sized stem. The stem should be easy to remove and replace using simple hand tools. This allows the stem to be replaced in the field under adverse conditions.

DESCRIPTION OF PRIOR ART A general description of a raised drilling operation is presented in US. Pat. No. 3,220,494 to R. E. Cannon et al, patented Nov. 30, 1965. In the system disclosed in this patent, a pilot hole is enlarged to the desired raise hole size by rotating and drawing a large diameter raise bit upward along the pilot hole.

In US. Pat. No. 3,659,659 to Carl L. Lichte, patented May 2, 1972, a large diameter raise bit with a replaceable stem is shown. The body of the bit includes a multiplicity of cutting stages around a central axis. The raise bit is attached to the drill column by a replaceable stem connected to the main body of the bit and the body of the bit includes a series of plates separated by a series of hollow support elements.

Raise bits manufactured by The Robbins Company,

650 South Orcas Street, Seattle, Wash. 98108 include a SUMMARY OF THE INVENTION The present invention provides a raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole. The body of the raise bit includes a multiplicity of rolling cutters for contacting and disintegrating the earth formations surrounding the pilot hole. A central opening extends through the raise bit body. One end of a drive stern extends into the central opening. At least one recess is located near the end of the drive stem. A retaining element is positioned in the recess and the retaining element is bolted to the raise bit body.

The drive stem of the raise bit of the present invention may be removed and a new drive stem inserted in its place. The retaining element is disconnected from the raise bit body and removed from the recess on the stem. The stem may then be withdrawn from the central opening in the raise bit body. A new stem may be inserted in its place and the retaining element repositioned on the raise bit body, thereby locking the new stem to the raise bit body. The raise bit of the present invention may be transported through small drifts or passages by removing the drive stem. The drive stem is reattached and the raise bit is ready for operation. The high-strength heat-treated stem is not weakened by welding. The raise bit body may be constructed of materials that are less expensive than the materials that make up the drive stem. Different sized drive stems may be attached to the raise bit body to allow the raise bit to be used in pilot holes of different sizes. The removal of the stem and replacement with a new stem may be accomplished in the field under adverse conditions with simple hand tools. Zero clearance is provided between the stem and the retaining element and between the retaining element and the raise bit body. This insures a rigid connection between the drive stem and the raise bit body. The drive stem of the present invention may be easily removed and a new stem put in its place without removing the cutter saddles adjacent the stem. The above and other features and advantages of the present invention will become apparent from a consideration of the following detailed description of the invention when taken in conjunction with the drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of a bit constructed in accordance with the present invention.

FIG. 2 shows a partial section of a portion of the bit shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, an exploded view of a raise bit constructed in accordance with the present invention is shown. The raise bit includes a raise bit body 11. The raise bit body 11 consists of a cutter stage plate 19, having a central opening 20. A multiplicity of saddles 22 are mounted on the cutter stage plate 19. A corresponding multiplicity of rolling cutters 21 are positioned in the saddles 22. The rolling cutters 21 contact and disintegrate the formations surrounding the pilot liole during the raise drilling operation.

A drive stem is positioned in the central opening 20. A pair of

flats

12 and 13 has been machined into the lower shank 14 of the stem 10. A two-piece collar .23 clamps onto the

flats

12 and 13.

Sections

27 and 28 of the two-piece collar 23 are connected and drawn together by

bolts

31 and 32 that extend through

holes

33 and 34. Flange plates 24 and on the two-piece collar are bolted to flange plate 26 on the cutter stage plate 19. The flange plate 26 is an integral part of the cutter stage plate 19. Bolts 29 and extend into holes 39 in the flange plate 26 and secure the two-piece collar 23 and stem 10 to the raise bit body 11.

Referring now to FIG. 2, a view in a partial section of a portion of the raise bit of FIG. 1 is shown. The drive stem 10 is connected to the cutter stage plate 19 by the

sections

27 and 28 of the two-piece collar 23. The

flange plates

24 and 25 are connected to the flange plate 26 by

bolts

29 and 30. A multiplicity of dowel pins help prevent the stem 10 from rotating in the raise bit body 11. The section 28 fits within the flat 12 on the drive stem 10. The shoulder 37 on section 28 is in abutment with the sholder 17 on drive stem 10. This prevents drive stem 10 from being pulled through the central opening 20 in the flange plate 19.

The structural details of a raise bit constructed in accordance with the present invention having been described, a raise drilling operation will now be considered using the bit shown in FIGS. 1 and 2. The raise drilling operation begins by drilling a small diameter pilot hole through the earth from a first location to an opening at a second location using a small diameter pilot bit. After the pilot hole is completed, the pilot bit is removed from the drill column and the raise bit shown in FIGS. 1 and 2 is attached to the drill column. The raise bit is rotated and drawn along the pilot hole thereby enlarging the pilot hole to the desired size. The two-piece collar 23 positioned in flats l2 and 13 on the drive stem 10 provides a rigid connection between the drive stem 10 and the raise bit body 11.

The raise bit may be transported through small drifts or passages by removing the drive stem 10 and transporting the drive stem 10 and raise bit body 11 through the small drift or passage separately. The

bolts

29 and 30 are removed, thereby disconnecting the

flange plates

24 and 25 from the flange plate 26. The

bolts

31 and 32 are removed allowing the

sections

27 and 28 of the two-piece collar to be removed from the

flats

12 and 13 in the drive stem 10. The drive stem 10 is withdrawn through the central opening 20 in the cutter stage plate 19 and the drive stem 10 and raise bit body 11 are transported through the small drift or passage. The drive stem 10 is inserted through the central opening 20 in the cutter stage plate 19 and the

sections

27 and 28 of the two-piece collar are positioned in the

flats

12 and 13. The

bolts

31 and 32 are inserted and the two-piece collar is locked to the drive stem 10.

Bolts

29 and 30 are inserted in the

flange plates

24 and 25 and connected to the flange plate 26. The drive stem '10 is again locked to the raise bit body 11 and the raised bit is ready for operation.

Should the drive stem 10 experience failure prior to failure of the raise bit body 11, the drive stem may be removed from the raise bit body 11 and a new drive stem inserted in its place. The

bolts

29 and 30 are removed, thereby disconnecting the

flange plates

24 and 25 from the flange plate 26. The

bolts

31 and 32 are removed allowing the

sections

27 and 28 of the two-piece collar 23 to be removed from the

flats

12 and 13 in the drive stem 10. The drive stem 10 may be withdrawn through the central opening 20 in the cutter stage plate 19. A new drive stem may be inserted in place of the drive stem 10. If the raise bit is to be used in a pilot hole of a different size, the new drive stem may have the appropriate diameter for the new pilot hole. The new drive stem is inserted through the opening 20 in cutter stage plate 19 and the two-piece collar connected together by

bolts

31 and 32. The

flange plates

24 and 25 are again connected to the flange plate 26 by

bolts

29 and 30 and the raise bit is ready for operation.

The embodiments of an invention in which an exclusive property or privilege is claimed are defined as follows:

l. A bit for enlarging a pilot hole into a larger diameter hole by distintegrating earth formations surrounding the pilot hole, comprising:

a main bit body including a multiplicity of cutters for contacting and disintegrating earth formations surrounding the pilot hole;

a central opening in said main bit body;

a drive stem positioned in said central opening with a portion of said drive stem extending beyond said central opening;

recess means on the portion of said drive stem extending beyond said central opening that provide said portion with a non-circular cross section;

a retaining element positioned in said recess means, said retaining element being a two-piece collar adapted to be bolted to said main bit body; and means for attaching said retaining element to said main bit body.

2. A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating earth formations surrounding the pilot hole, comprising:

a cutter stage plate;

a multiplicity of saddles mounted on said cutter stage plate; I

a multiplicity of rolling cutters positioned in said saddles;

a central opening in said cutter stage plate;

a drive stem positioned in said opening with a portion of said drive stem extending below said central opening; r

recess means on the portion of said drive stem extending below said central opening that provide said portion with a non-circular cross section;

retaining element means positioned in said recess means, said retaining element means .being a twopiece collar adapted to be bolted to said cutter stage plate; and

means for attaching said retaining element means to said cutter stage plate.

3. A bit for enlarging a pilot hole into a larger diame ter hole by disintegrating earth formations surrounding the pilot hole, comprising:

a main bit body including a multiplicity of cutters for contacting and disintegrating earth formations surrounding-the pilot hole;

a central opening in said main bit body;

at least one flat on the portion of said drive stem extending beyond said central opening;

a retaining element positioned in said at least one flat, said retaining element having a flat portion that fits against said flat and a connecting portion; and

means for attaching said connecting portion of said retaining element to said main bit body.

4. A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating earth formations surrounding the pilot hole, comprising:

a cutter stage plate;

a multiplicity of saddles mounted on saidv cutter stage plate;

a multiplicity of rolling cutters positioned in said saddles; 1

a central opening in said cutter stage plate;

a drive stem positioned in said opening with a portion of said drive stem extending below said central opening;

a recess on the portion of said drive stem extending below said central opening that provides the portion with a non-circular cross section;

a retaining element positioned in said recess, said re taining element comprising a multiplicity of sections that at least partially surround said drive stern and prevent said drive stem from rotating in said central opening and being drawn through said central opening; and

' means for attaching said retaining element to said cutter stage plate.

5. A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating earth formations surrounding the pilot hole, comprising:

a cutter stage plate;

a multiplicity of saddles mounted on said cutter stage plate;

a multiplicity of rolling cutters positioned in said saddles;

a central opening in said cutter stage plate;

a flange plate on said cutter stage plate;

recess means -on the portion of said drive stem extending below said central opening that provide said portion with a non-circular cross section; retaining element means positioned in said recess means; flange plate means on said retaining element means; and means attaching said flange plates together. I Y

Claims

1. A bit for enlarging a pilot hole into a larger diameter hole by distintegrating earth formations surrounding the pilot hole, comprising: a main bit body including a multiplicity of cutters for contacting and disintegrating earth formations surrounding the pilot hole; a central opening in said main bit body; a drive stem positioned in said central opening with a portion of said drive stem extending beyond said central opening; recess means on the portion of said drive stem extending beyond said central opening that provide said portion with a noncircular cross section; a retaining element positioned in said recess means, said retaining element being a two-piece collar adapted to be bolted to said main bit body; and means for attaching said retaining element to said main bit body.

2. A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating earth formations surrounding the pilot hole, comprising: a cutter stage plate; a multiplicity of saddles mounted on said cutter stage plate; a multiplicity of rolling cutters positioned in said saddles; a central opening in said cutter stage plate; a drive stem positioned in said opening with a portion of said drive stem extending below said central opening; recess means on the portion of said drive stem extending below said central opeNing that provide said portion with a non-circular cross section; retaining element means positioned in said recess means, said retaining element means being a two-piece collar adapted to be bolted to said cutter stage plate; and means for attaching said retaining element means to said cutter stage plate.

3. A bit for enlarging a pilot hole into a larger diameter hole by disintegrating earth formations surrounding the pilot hole, comprising: a main bit body including a multiplicity of cutters for contacting and disintegrating earth formations surrounding the pilot hole; a central opening in said main bit body; a drive stem positioned in said central opening with a portion of said drive stem extending beyond said central opening; at least one flat on the portion of said drive stem extending beyond said central opening; a retaining element positioned in said at least one flat, said retaining element having a flat portion that fits against said flat and a connecting portion; and means for attaching said connecting portion of said retaining element to said main bit body.

4. A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating earth formations surrounding the pilot hole, comprising: a cutter stage plate; a multiplicity of saddles mounted on said cutter stage plate; a multiplicity of rolling cutters positioned in said saddles; a central opening in said cutter stage plate; a drive stem positioned in said opening with a portion of said drive stem extending below said central opening; a recess on the portion of said drive stem extending below said central opening that provides the portion with a non-circular cross section; a retaining element positioned in said recess, said retaining element comprising a multiplicity of sections that at least partially surround said drive stem and prevent said drive stem from rotating in said central opening and being drawn through said central opening; and means for attaching said retaining element to said cutter stage plate.

5. A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating earth formations surrounding the pilot hole, comprising: a cutter stage plate; a multiplicity of saddles mounted on said cutter stage plate; a multiplicity of rolling cutters positioned in said saddles; a central opening in said cutter stage plate; a flange plate on said cutter stage plate; a drive stem positioned in said opening with a portion of said drive stem extending below said central opening; recess means on the portion of said drive stem extending below said central opening that provide said portion with a non-circular cross section; retaining element means positioned in said recess means; flange plate means on said retaining element means; and means attaching said flange plates together.