EDGE PROTECTOR FOR ROOF DRILL BIT CUTTING INSERT

Abstract

A rotary drill bit includes an elongate drill bit body having a slot at a forward end, an edge protector received in the slot of the drill bit body and a cutting insert having a cutting edge. The edge protector includes: a first side having a first bottom edge and a first top edge; a second side opposed to the first side, the second side having a second bottom edge and a second top edge; and a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side. The cutting insert is received in the edge protector such that the cutting edge is recessed below one of the first top edge of the first side or the second top edge of the second side.

Description

BACKGROUND

The invention pertains generally to an excavating tool such as, for example, a rotary drill bit useful for drilling through various earth strata. More specifically, the invention pertains to a rotary drill bit with a cutting insert such as, for example, a roof drill bit useful for drilling bore holes in an underground mine.

The expansion of an underground mine, such as for example, a coal mine, requires digging a tunnel. Initially, this tunnel has an unsupported roof. In order to support and stabilize the roof in an underground tunnel, bore holes are drilled in the roof, i.e., earth strata. The apparatus used to drill these holes typically comprises a drill with a long shaft, i.e., drill steel, attached to the drill. A roof drill bit is detachably mounted to the drill steel at the distal end thereof. In certain roof drill bits, a hard cutting insert is mounted on a body of the roof drill bit.

A hard cutting insert for use in a roof drill bit is typically formed of cemented tungsten carbide and can be secured by brazing the insert within a slot formed within a top working surface of the body of the roof drill bit. Tungsten carbide is a costly material and cutting inserts are expensive to manufacture. Thus, it is important that the hard cutting insert be securely held in the slot of the roof drill bit so as not to become dislodged during use. Therefore, it is important to use a technique to produce an effective braze joint between the bit body and the hard cutting insert so as to provide a more durable tool having an increased useful life.

Because tungsten carbide is a costly material and cutting inserts are expensive to manufacture, it is also important that care be taken not to damage the hard cutting insert prior to being used, e.g. during shipping, while installing the hard cutting insert, and/or prior to the operation of the roof drill bit containing the hard cutting insert. Heretofore, hard cutting inserts have been damaged in one or more of these situations resulting in the hard cutting insert being defective and not suitable for use or having a shortened useful cutting life.

There is a need for improved roof drilling bits that overcome disadvantages, limitations and shortcomings of known roof drilling bits. It would also be desirable to provide an improved roof drill bit that has a longer useful life. It would also be desirable to provide a hard cutting insert that is not damaged prior to being used for a cutting operation.

SUMMARY

An aspect of the present invention is to provide rotary drill bit for engaging an earth strata material that includes an elongate drill bit body having an axial forward end and an axial rearward end, wherein the drill bit body contains a slot at the forward end. The rotary drill bit also includes an edge protector received in the slot of the drill bit body, the edge protector including: a first side having a first bottom edge and a first top edge; a second side opposed to the first side, the second side having a second bottom edge and a second top edge; and a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side. The rotary drill bit also includes a cutting insert having an elongate insert body rotatable about a central axis, the elongate insert body having a pair of symmetrical halves symmetrical about the central axis, each symmetrical half including: a leading face; a top surface; and a cutting edge formed between the leading face and the top surface. The cutting insert is received in the edge protector such that the cutting edge is recessed below one of the first top edge of the first side or the second top edge of the second side.

Another aspect of the present invention is to provide an edge protector assembly for a rotary drill bit includes a shim having a first side having a first bottom edge and a first top edge, a second side having a second bottom edge and a second top edge, and a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side. The edge protector assembly also includes a cutting insert having a leading face, a top surface, and a cutting edge formed between the leading face and the top surface. The cutting insert is received in the shim such that the cutting edge is recessed below one of the first top edge of the first side or the second top edge of the second side.

A further aspect of the present invention is to provide an edge protector for a roof drill bit cutting insert having at least one cutting edge, the edge protector including a first side having a first bottom edge and a first top edge, a second side having a second bottom edge and a second top edge, and a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side. The first side, the second side and the bottom portion are configured for receiving the cutting insert such that the at least one cutting edge is recessed below the first top edge of the first side or recessed below the second top edge of the second side.

These and various other features and advantages will be apparent from a reading of the following detailed description.

DRAWINGS

FIG. 1 is an exploded assembly view of a rotary drill bit, e.g. a roof drill bit, in accordance with an aspect of the invention.

FIG. 2 is an isometric view of an edge protector shown in FIG. 1, in accordance with an aspect of the invention.

FIG. 3 is a front elevational view of the edge protector shown in FIGS. 1 and 2, in accordance with an aspect of the invention.

FIG. 4 is a front elevational view of the edge protector and cutting insert shown in FIG. 1 as assembled, in accordance with an aspect of the invention.

FIG. 5 is an isometric view of one end of the assembled edge protector and cutting insert shown in FIG. 4, in accordance with an aspect of the invention.

FIG. 6 is an isometric view of another end of the assembled edge protector and cutting insert shown in FIG. 4, in accordance with an aspect of the invention

DETAILED DESCRIPTION

The following description is for purposes of illustrating various aspects of the invention only and not for purposes of limiting the scope of the invention.

Referring to the drawings, FIGS. 1-6 illustrates a rotary drill bit assembly in the form of a roof drill bit, generally designated as 10, useful for drilling through various earth strata, in accordance with various aspects of the invention. Roof drill bit assembly 10 has an elongate drill bit body 12 typically made of, for example, steel. Drill bit body 12 presents a generally cylindrical geometry. Drill bit body 12 has an axial forward end 14 and an axial rearward end 16. Drill bit body 12 contains a transverse slot 18 in the axial forward end thereof 14. Drill bit body 12 also may include a debris evacuation or collection port 20 that is mediate between the axial forward end 14 and the axial rearward end 16. During the drilling operation, dirt and debris may pass through the port 20.

The roof drill bit assembly 10 also includes a cutting insert 22 (or rotary drill bit insert). The cutting insert 22 is made from, for example, a cemented tungsten carbide that is a mixture of cobalt and tungsten carbide. Other super hard, wear resistant materials such as polycrystalline diamond, ceramics, or cermet may be used as a supplement and/or substitute. For example chromium carbide-coated metals and other cermets where titanium carbide or vanadium carbide is added to tungsten carbide may be candidates for inserts materials in accordance to aspects of the invention. Alternate ceramics for such applications include aluminum-based, silicon based, zirconium-based and glass varieties. Still other insert materials alternatives include cubic refractory, transition metal carbides or any other known or subsequently developed material(s) harder than the base material. Also coatings of the inserts such as PVD or CVD coatings can be used.

Cutting insert 22 has a cutting insert body, generally designated as 24, that has a top surface generally designated as 26, a bottom surface generally designated as 28, and opposite end surfaces generally designated as 32 and 34. The cutting insert body 24 is structured and arranged into two opposite symmetric connected portions, i.e. a pair of symmetrical halves, which are symmetric about the central axis A-A. One symmetric portion includes a leading face 40 and a cutting edge 50 formed between the leading face 40 and the top surface 26. In one aspect, the top surface 26 includes a primary relief surface 44. In another aspect, the top surface 26 also includes a secondary relief surface 46 wherein the primary relief surface 44 and the secondary relief surface 46 are contiguous and non-coplanar. It will be appreciated that each symmetric portion is generally the same and only one symmetric portion will be described in detail herein.

The rotary drill bit or roof drill bit assembly 10 also includes an edge protector, generally designated as 60, configured to be received in the transverse slot 18 of the drill bit body 12. The edge protector 60 includes a first side 62 having a first bottom edge 64 and a first top edge 66. The edge protector 60 also includes a second side 68 generally opposed to and/or parallel to the first side 60. The second side 68 includes a second bottom edge 70 and a second top edge 72. The edge protector 60 also includes a bottom portion 74 adjoining or connecting the first bottom edge 64 of the first side 62 and the second bottom edge 70 of the second side 68.

In accordance with an aspect of the invention, the cutting insert 22 is configured to be received in the edge protector 60 such that the cutting edge 50 is recessed below one of the first top edge 66 of the first side 62 or the second top edge 72 of the second side 68. As shown, for example, in FIG. 4, the cutting edge 50 is recessed below the first top edge 66 of the first side 62. In one aspect, the cutting edge 50 is recessed below a portion of the first top edge 66 that is generally parallel to the cutting edge 50 (see, for example, FIG. 4). The first top edge 66 (and the second top edge 72) may have various portions that are not coplanar with one or more of these portions providing the protection for the cutting edge 50 (and the cutting edge 51). In another aspect, the cutting edge 50 is recessed below the first top edge 66 a distance D of about 0.001 inches to about 0.050 inches.

Advantageously, the described and illustrated configuration of the cutting edge 50 with respect to the first top edge 66 of the first side 62 provides for the first top edge 66 to protect the cutting edge 50 to prevent, for example, chipping or other damage to the cutting edge 50 prior to being used, e.g. during shipping, while installing the hard cutting insert 22, and/or prior to the operation of the roof drill bit 10 containing the hard cutting insert 22.

It will be appreciated that the other symmetric portion of the cutting insert 22 can include a second cutting edge 51 (see FIG. 1) that is configured with respect to the second top edge 72 of the second side 68 generally the same as described herein in regards to the cutting edge 50 with respect to the first top edge 66 of the first side 62.

The edge protector 60 is positioned within the transverse slot 18 and the insert 22 is positioned in the edge protector 60. In one aspect, the edge protector 60 is affixed to the slot 18 of the drill bit body 12. In another aspect, the cutting insert 22 is affixed to the edge protector 60. The cutting insert 22 and the edge protector 60 may be affixed to each other first and then affixed to the slot 18, or all may be affixed to one another at generally the same time. They may be affixed as described by, for example, attaching mechanically or otherwise, via brazing or gluing using conventional compositions and techniques known to those skilled in the art. To assist in, for example, affixing these components by brazing, the first side 62, second side 68 and/or the bottom portion 74 can include a plurality of perforations 76 formed therein. The perforations can be of various shapes and sizes and aid in allowing the braze material to flow efficiently in relation to the cutting insert 22, the edge protector 60 and the slot 18 to provide for a better attachment of these components to each other.

In another aspect of the invention, the edge protector 60 is formed of a material having a hardness value that is less than a hardness value of the cutting insert 22. As described, the cutting insert is made of a relatively hard material such as, for example, cemented tungsten carbide. The edge protector 60 is made with a material such as, for example, copper, steel, aluminum, brass, triclad, or any iron based material that is less hard in comparison to the cutting insert 22 material. Advantageously, by selecting the relative hardness of the edge protector 60 and the cutting insert 22 as described, the edge protector 60 will provide the desired shielding or protection for the cutting edges 50 and 51 while allowing for the roof drill bit 10 to be put directly into operation without the need to remove the edge protector 60 because the edge protector 60 will wear relatively quickly during operation of the roof drill bit 10 to expose or unshield the cutting edges 50 and 51 so that they may perform the desired cutting operation.

In another aspect, the edge protector 60 may also be configured such that other parts of the cutting insert 22 are shielded or protected. For example, as illustrated in FIG. 4 an end 78 of the edge protector 60 may be configured to extend beyond the end 32 of the cutting insert 22 such that the end 32 is recessed with respect to the end 78 and protect the end 32. In another aspect, the first top edge 66 and the end 78 of the edge protector combine to protect a corner 50a of the cutting edge 50.

In another aspect, the edge protector 60 also may be in the form of a shim that also provides and includes the edge protection benefits as described herein. In one aspect, the shim helps the flow of braze to fully and uniformly cover the cutting insert 22 and transverse cutting slot 18. The shim also helps to provide a uniform gap between the cutting insert 22 and the transverse cutting slot 18.

Whereas particular aspects of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.

Claims

1. A rotary drill bit for engaging an earth strata material, the rotary drill bit comprising:

an elongate drill bit body having an axial forward end and an axial rearward end, the drill bit body containing a slot at the forward end;

an edge protector received in the slot of the drill bit body, the edge protector comprising: a first side having a first bottom edge and a first top edge; a second side opposed to the first side, the second side having a second bottom edge and a second top edge; and a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side; and

a cutting insert having an elongate insert body rotatable about a central axis, the elongate insert body having a pair of symmetrical halves symmetrical about the central axis, each symmetrical half comprising: a leading face; a top surface; and a cutting edge formed between the leading face and the top surface,

wherein the cutting insert is received in the edge protector such that the cutting edge is recessed below one of the first top edge of the first side or the second top edge of the second side.

2. The rotary drill bit of claim 1, wherein the cutting edge is recessed below one of the first top edge or the second top edge a distance of about 0.001 inches to about 0.050 inches.

3. The rotary drill bit of claim 2, wherein the cutting edge is parallel to one of the first top edge or the second top edge.

4. The rotary drill bit of claim 1, wherein the first side, the second side and the bottom portion each include a plurality of perforations formed therein.

5. The rotary drill bit of claim 1, wherein the edge protector is formed of a material having a hardness value that is less than a hardness value of the cutting insert.

6. The rotary drill bit of claim 1, wherein the edge protector is formed of at least one of copper, steel, aluminum, brass, triclad, or any iron based material.

7. The rotary drill bit of claim 1, wherein the edge protector is affixed to the slot of the drill bit body.

8. The rotary drill bit of claim 7, wherein the cutting insert is affixed to the edge protector.

9. An edge protector assembly for a rotary drill bit, the edge protector assembly comprising:

a shim having a first side having a first bottom edge and a first top edge, a second side having a second bottom edge and a second top edge, and a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side; and

a cutting insert having a leading face, a top surface, and a cutting edge formed between the leading face and the top surface,

wherein the cutting insert is received in the shim such that the cutting edge is recessed below one of the first top edge of the first side or the second top edge of the second side.

10. The edge protector assembly of claim 9, wherein the cutting edge is recessed below one of the first top edge or the second top edge a distance of about 0.001 inches to about 0.050 inches.

11. The edge protector assembly of claim 10, wherein the cutting edge is parallel to one of the first top edge or the second top edge.

12. The edge protector assembly of claim 9, wherein the first side, second side and bottom portion each include a plurality of perforations formed therein.

13. The edge protector assembly of claim 9, wherein the shim is formed of a material having a hardness value that is less than a hardness value of the cutting insert.

14. The edge protector assembly of claim 9, wherein the shim is formed of at least one of copper, steel, aluminum, brass, triclad, or any iron based material.

15. The edge protector assembly of claim 9, wherein the cutting insert is affixed to the shim.

16. An edge protector for a roof drill bit cutting insert having at least one cutting edge, the edge protector comprising:

a first side having a first bottom edge and a first top edge;

a second side having a second bottom edge and a second top edge;

a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side,

wherein the first side, the second side and the bottom portion are configured for receiving the cutting insert such that the at least one cutting edge is recessed below the first top edge of the first side or recessed below the second top edge of the second side.

17. The edge protector of claim 16, wherein one of the first top edge or the second top edge is parallel to the at least one cutting edge of the cutting insert.

18. The edge protector of claim 16, wherein the first side, second side and bottom portion each include a plurality of perforations formed therein.

19. The edge protector of claim 16, wherein the edge protector is formed of a material having a hardness value that is less than a hardness value of the cutting insert.

20. The edge protector of claim 16, wherein the edge protector is formed of at least one of copper, steel, aluminum, brass, triclad, or any iron based material.