AU702625B2 - Cable bolt head - Google Patents

Description

-2- CABLE BOLT HEAD BACKGROUNDS OF THE INVENTION 1. Field of the Invention The present invention relates to mine roof bolts. Specifically, the present invention relates to flexible mine roof bolts utilizing a multi-strand cable and which are adapted to be rotated in the bore hole by a drive head at a first end thereof.

2. Description of the Prior Art Flexible cable bolts and cable systems have been utilized in the construction and mining industries since about 1970. More recently, cable mine roof bolts have been utilized as a roof control in the mining industry with both resin grouting and more conventional cement grouting techniques. Examples of cable mine roof bolts utilized in resin grouting applications can be found in U.S. Patents Nos. 5,230,589 to Gillespie; 5,259,703 to Gillespie; 5,375,946 to Locotos; and WIPO Publication No. WO 93/03256 to Fuller et al. All of these mine roof bolt designs incorporate some type of drive head assembly for rotating the cable bolt. All of these 15 prior art systems suffer from various drawbacks.

The mine roof bolt disclosed in the Gillespie patents replaces a tubular barrel of a conventional barrel and wedge assembly with a specially machined hexagonal head collar.

The hexagonal head collar must necessarily be large enough to receive the internal wedges therein which make the head collar too large to be driven with conventional bolting equipment. Consequently, in addition to the special machining of the hexagonal drive head, the Gillespie patents require the use of specialized adapters by the bolting equipment to accommodate the enlarged hexagonal head.

-3- WIPO Publication No. WO 93/03256 and the Locotos patent disclose cable mine roof bolts which utilize a hex nut attached to the end thereof to both rotate the cable bolt and support the bearing plate. The WIPO publication discloses inclusions of threads on at least one of the strands of the cable so that the hex nut can be threaded directly onto the cable. The Locotos patent utilizes a collar having a threaded end which is attached to the cable with the hex head threaded onto the collar. These designs require the attachment of the hex nut to the cable to meet the loading capacity of the cable bolt since the drive heads also serve to support the bearing plate.

It is an object of the present invention to provide a mine roof bolt design which overcomes or at least ameliorates one or more of the disadvantages of the abovedescribed prior art. It is a further object of the present invention, at least in its preferred forms, to provide a mine roof bolt design which can be utilized with conventional roof bolting equipment. A further object of the preferred forms of the present invention is to provide a mine roof bolt which is relatively easy and economical to manufacture.

SUMMARY OF THE INVENTION Accordingly, in a first aspect the present invention provides a mine roof bolt comprising: a flexible multi-strand cable having a first end and a second end; and a drive head integrally formed on said first end, said drive head having a plurality 20 of driving faces on an exterior surface thereof, wherein material of said multi-strand cable of said first end forms at least a portion of said integral drive head.

Preferably, the integrally formed drive head is forged on the first end being Sformed, in part, by a multi-strand cable at the first end.

In a second aspect the present invention provides a mine roof bolt comprising: a flexible multi-strand cable having a first end and a second end wherein said first end of said multi-strand cable is splayed such that individual cables are separated and spaced from each other at said first end and; a drive head formed on said first end of said multi-strand cable, said drive head having a plurality of driving faces on an exterior surface thereof wherein said drive head is cast directly onto said splayed first end whereby material forming said drive head is positioned between said strands of said multi-strand cable at said first end.

A sleeve may be provided surrounding the first end of the cable to assist in -4forming the drive head during the foregoing operation such that part of the sleeve and part of the first end of the cable combine to form all of the forged drive head.

The flexible mine roof bolt which includes the forged drive head, according to the first embodiment of the present invention, may be formed as follows. At least a first end of a flexible multi-strand cable is heated to the appropriate forging temperature and the drive head is forged on the heated first end by an appropriate shaped die in a forging machine wherein the multi-strand cable at the heated first end forms at least part of the forged drive head. The method of the present invention may additionally include the step of attaching a sleeve to the first end of the cable prior to heating. With an attached sleeve, both the first end of the cable and the sleeve are heated and subsequently forged wherein the drive head is formed by material from the sleeve and from the multi-strand cable. The sleeve may be attached by swaging, use of an adhesive, welding, or combinations thereof. Additionally, metal filings •f may be incorporated within the adhesive to provide a more secure bond of the sleeve to the multi-strand cable.

15 These and other advantages of the present invention will be clarified in the brief description of the preferred embodiments wherein like reference numerals represent like S-element throughout.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example oa only, with reference to the accompanying drawings, in which: SFig. 1 is a side view of a cable mine roof bolt according to the first embodiment of the present invention; Fig. 2 is an enlarged sectional view of the cable mine roof bolt illustrated in Fig. 1; Fig. 3 illustrates the first step in manufacturing the cable mine roof bolt illustrated in Figs. 1 and 2 according to the method of the present invention; Fig. 4 is a flow chart illustrating the method of the present invention of manufacturing the cable mine roof bolt illustrated in Figs. 1 and 2; Fig. 5 is a side view of a cable mine roof bolt according to a second embodiment of the present invention; BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 1 and 2 illustrate a cable mine roof bolt 10 according to the present invention. The mine roof bolt 10 includes a central cable 12 which is adapted to be received into a bore hole.

The cable 12 is preferably standard seven-wire cable which is described in ASTM designation A 416 entitled "Standard Specification for Steel Strand, Uncoated Seven-Wire for Prestressed Concrete". The cable 12 is preferably of a seven-strand type which has a center strand enclosed tightly by six helically wound outer strands with a uniform pitch of between twelve °oo• and sixteen times the nominal diameter of the cable. The cable 12 generally comes in grades determined by the minimum ultimate strength of the cable. For example, Grade 250 has a minimum ultimate strength of 250,000 psi and Grade 270 has a minimum ultimate strength of 270,000 psi. Additionally, bird cages may be incorporated into the length of the cable 12 at selected positions thereon. Similarly, buttons can be swaged onto the cable 12 at spaced positions thereon. The bird cages and buttons help improve the mixing, of the resin as well as increase the bond strength of the attachment as is known in the art.

At a first end of the cable 12 is an integral drive head 14. The drive head 14 includes oooo• four planar driving faces 16 formed on an exterior surface thereof. The four driving faces 16 form a substantially one inch square drive head on the drive head 14. A sleeve 18 surrounds -6the cable 12 at the first end thereof. The sleeve 18 is adjacent to and integral with the drive head 14.

The mine roof bolt 10 can be formed according to the following method. The cable 12 is cut slightly larger than the ultimately desired length. A sleeve 18 is attache.d to the cable 12 at the first end thereof with the sleeve 18 flush with the first end of the cable 12 as shown in Fig. 3 and Step 20 in Fig. 4. The sleeve 18 can be attached to the cable 12 by swaging, adhesives, welding, or combinations thereof. Additionally, if adhesives are utilized to attach the sleeve 18 to the cable 12, metal filings or metal powder may be incorporated to the adhesives to increase the bond strength. The interior of the sleeve 18 may also be roughened to increase bond strength. The attachment of the sleeve 18 to the cable 12 is not believed to be critical since this particular attachment will not be required to withstand the loading strength of the mine roof bolt •,i The sleeve 18 and first end of the cable 12 are then heated to an appropriate forging temperature as noted in Step 22 in Fig. 4. The sleeve 18 and the first end of the cable 12 are 15 then inserted into a forging machine where appropriate shaped dies will be utilized to form the drive head 14 with appropriately shaped driving faces 16 as noted in Step 24 of Fig. 4. In this manner, the drive head 14 is forged onto the first end of the cable 12 such that the first end of a.° the cable 12 and the sleeve 18 combine to form the drive head 14.

-o By forming the drive head 14 integral with the cable 12 by forging, the drive head 14 meets the loading requirements of the mine roof bolt 10. The drive head 14 will be utilized to support a bearing plate assembly in a conventional manner. Additionally, the drive head 14 ooooo will be utilized for rotating the mine roof bolt 10 in the resin grouted installations in a conventional manner as known in the art.

-7- The drive head 14 may be forged directly on the first end of the cable 12 without the use of the sleeve 18. However, without the sleeve 18, a longer portion of the first end of the cable 12 will be required to form the drive head 14 which increases the difficulty in the forging operation. The sleeve 18 assists in the forging operation and provides a stiffener for the first end of the cable. Furthermore, if desired, the mine roof bolt 10 of the present invention may further include a conventional barrel and wedge assembly (not shown) to support the bearing plate. Barrel and wedge assemblies are well-known and are well-accepted mechanisms for retaining tensioned cable systems in place such as retaining a bearing plate against a roof. If a barrel and wedge assembly is utilized with the mine roof bolt 10, the forged drive head 14 will only need to have strength requirements for rotating the mine roof bolt 10 during installation.

Fig. 5 illustrates a cable mine roof bolt 30 according to a second embodiment of the present invention. The mine roof bolt 30 includes a multi-strand cable 32 which is substantially identical to the cable 12 described above. A first end of the cable 32 is splayed.

A drive head 34 is cast directly onto the splayed first end of the cable 32. The drive head 34 includes four planar driving faces 36 forming a substantially one inch square drive head substantially the same as the driving faces 16 and drive head 14 described above. The splaying of the first end of the cable 32 assures a secure attachment of the integral, cast drive head 34. A stiffener sleeve 38 may be utilized adjacent the drive head 34 and may be formed ,i integrally with the drive head 34 during the casting operation. The mine roof bolt 30 is used in a conventional fashion as described above in connection with mine roof bolt 10. Mine roof bolt 30 may also be utilized with the conventional barrel and wedge assembly (not shown) wherein the drive head 34 would be required only for rotating the mine roof bolt wherein the drive head 34 would be required only for rotating the mine roof bolt -8- In all of the embodiments described above, the drive heads fit conventional bolting equipment without requiring additional adapters. Additionally, the drive heads are easily incorporated onto the mine roof bolt.

It will be apparent to those of ordinary skill in the art that various changes and modifications may be made to the present invention without departing from the spirit and scope thereof. Consequently, the scope of the present invention is intended to be defined by the attached claims.

*o* oo THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A mine roof bolt comprising: a flexible multi-strand cable having a first end and a second end; and a drive head integrally formed on said first end, said drive head having a plurality of driving faces on an exterior surface thereof, wherein material of said multi-strand cable of said first end forms at least a portion of said integral drive head.

2. The mine roof bolt of claim 1 wherein said drive head is forged on said first end, and wherein said multi-strand cable at said first end forms at least part of said drive head.

3. The mine roof bolt as claimed in claim 2 further comprising a sleeve surrounding said cable and positioned adjacent said drive head, wherein said drive head is formed integrally with said sleeve.

4. The mine roof bolt of claim 3 wherein part of said sleeve and part of said multistrand cable at said first end form all of said forged drive head.

A mine roof bolt comprising: 15 a flexible multi-strand cable having a first end and a second end wherein said first end of said multi-strand cable is splayed such that individual cables are separated and spaced from each other at said first end; and a drive head formed on said first end of said multi-strand cable, said drive head having a plurality of driving faces on an exterior surface thereof wherein said drive head 20 is cast directly onto said splayed first end whereby material forming said drive head is positioned between said strands of said multi-strand cable at said first end.

6. A method of forming a flexible mine roof bolt, comprising the steps of: a) heating at least a first end of a flexible multi-strand cable; and b) forging a drive head on said heated first end, wherein said multi-strand cable at said first heated end forms at least part of said forged drive head.

7. The method of claim 6 further comprising the step of attaching a sleeve to said first end of said first cable prior to said heating, wherein said heating step heats said first end and said sleeve, and wherein said sleeve forms at least part of said drive head.

Claims (3)

1. 8. The method of claim 7 wherein said sleeve is attached by a process selected from the group consisting of swaging, using an adhesive on an interior of said sleeve, welding, and combinations thereof.
2. 9. The method of claim 7 wherein said sleeve is attached at least in part by use of an adhesive having metal filings therein. A mine roof bolt substantially as hereinbefore described with reference to any one of the embodiments of the invention shown in the drawings.
3. 11. A method of forming a flexible mine roof bolt substantially as hereinbefore described with reference to any one of the embodiments of the invention shown in the drawings. Dated this 16th Day of February, 1998 JENNMAR CORPORATION Attorney: CAROLINE M. BOMMER Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS ABSTRACT A mine roof bolt (10) having a flexible multi-strand cable (12) including a first and second end with a drive head (14) integrally formed on the first end. The drive head (14) is formed such that it includes a plurality of driving faces (16) on an exterior surface thereof. In one embodiment the drive head (14) is forged onto the first end of the flexible multi-strand cable (12). C. S o C