AU754805B2

AU754805B2 - A bolt and attachment, and a method of fitting the attachment

Info

Publication number: AU754805B2
Application number: AU87173/98A
Authority: AU
Inventors: Jeffrey Robert Fergusson
Original assignee: Industrial Roll Formers Pty Ltd
Current assignee: Industrial Rollformers Pty Ltd
Priority date: 1997-10-08
Filing date: 1998-09-30
Publication date: 2002-11-28
Anticipated expiration: 2018-09-30
Also published as: AU8717398A

Description

-1I- Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

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a a. a a. a a a. *a a a Name of Applicant: Actual Inventors: Address for Service: Industrial Roll Formers Pty Ltd FERGUSSON Jeffrey Robert ADDRESS FOR SERVICF

ALTERED

koctekb\so\ 010( AlI hnes, U.evei 3,o ~q AWfe~ o7 DAkVIES COLLIbSO)N CAVE, Patelft Attuiiicyb,, of be~veiA 0 10 Barrak Strcct, Sydncy I c ,th W ales 2000 M115r'-spot-f *vREGo Invention Title: Details of Associated Provisional Application No: P09653/97 The following statement is a full description of this invention, including the best method of performing it known to us: Q:\OPER\DH\P09653.273 30/9/98 A BOLT AND ATTACHMENT. AND A METHOD OF FITTING THE

ATTACHMENT

The present invention relates to a rock bolt and attachment, and a method of fitting the attachment to the rock bolt.

It is known to install a rock bolt in mining construction by drilling a hole in a rock wall, inserting a resin cartridge into the hole and subsequently inserting the bolt to break the cartridge. The bolt is generally spun in the hole so as to work the resin through an annulus formed between the hole and the bolt and to sufficiently mix the resin, prior to the resin S. setting. The annulus must be large enough to allow the resin to pass along the length of the bolt, but small enough to resist the resin shearing under load. The smaller the annulus, the greater the effective bonding strength of the resin.

15 A problem with conventional resin bolting is that it becomes less cost effective when larger holes are employed due to the need for increased diameter bolts with attendant increased material costs. For example, a conventional rock bolt used for resin bolting has a diameter of 22 mm and is normally installed in a 27 mm diameter hole. However, holes used in large scale production mining generally utilise larger drill assemblies which produce holes with 20 diameters from 35 mm to 38 mm, which would require bolts of diameter 30 mm to 34 mm if a resin bolting technique were to be used. The larger of these bolts would require about three times the amount of steel to manufacture, to provide similar bond strength characteristics as those of the conventional 22 mm diameter bolt and associated hole.

The present invention seeks to address these difficulties.

In accordance with a first aspect of the present invention there is disclosed a rock bolt for use in mining, said bolt comprising a bar having a plurality of outwardly extending deformations and being partially located interior of a sleeve, said sleeve being formed onto said bar by deformation of said sleeve to interengage said bar deformations and sleeve interior whereby said interengagement of bar and sleeve both resists longitudinal tensional forces applied to said rock bolt and acting to pull said bar from the interior of said sleeve, and resists rotation of w eeve relative to said bar.

In accordance with a second aspect of the present invention there is disclosed a method of forming a rock bolt for use in mining, said method comprising the steps of: inserting a bar having a plurality of outwardly extending deformations partially into the interior of a sleeve, and deforming said sleeve to interengage said bar deformations with the interior of said sleeve, whereby the interengagement of said bar and sleeve both resists longitudinal tensional forces applied to said rock bolt and acting to pull said bar from the interior of said sleeve and resists rotation of said sleeve relative to said bar.

A method of installation of a rock bolt is also disclosed.

A preferred embodiment of the invention is more fully described, by way of non-limiting example only, with reference to the accompanying drawings in which: 1 Figure 1 is a side view of a bolt and attachment in accordance with the preferred S 15 embodiment, showing the attachment in cross section before forming; Figure 2 is a side view of a bolt with the attachment formed thereon, showing the attachment in cross section after forming; Figure 3 is a side view of the bolt and attachment; Figure 4 illustrates the bolt after installation; Figure 5 is a perspective view of a bolt and attachment prior to being fixed onto the bolt and thus is an exploded perspective view of Fig 1; and ~Figure 6 is a perspective view of the attachment formed onto the bolt and thus is a perspective view of Figs 2 and 3.

With reference to Figures 1 to 6, a bolt 1 is shown as including an elongate bar portion 2 with deformations 3 formed along the length thereof. One end 4 of the bolt 1 (Figs 1 to 4) is threaded for receipt of a nut 5 and the other end 6 of the bolt is adapted for receipt of an attachment 7 in the form of a cylindrical sleeve 8 which has a larger internal diameter than the maximum external diametric dimension of the bolt 1. The sleeve 8 preferably comprises heavy steel (ie a steel tube which is not light or thin walled) which is formed onto the bolt in the manner illustrated in Figures 2, 3 and 6. Specifically, the sleeve is cold formed by being pressed or rolled so that the deformations on the bar project into the comparatively softer or S ,e malleable material of the attachment 7, to secure the attachment 7 in place. Also, the pressing or rolling causes formation of a thread 10 or similar protuberances along the length of the attachment 7.

The attachment 7, after being formed onto the end of the bolt 1, may then be inserted in a blind hole 11 in a rock face 12, following insertion of a resin cartridge (not shown), as illustrated in Figure 4. The bolt 1 is inserted and rotated to mix the resin from the resin cartridge. As opposed to conventional rotation of the bolt to transport the resin along the length of the bolt, the thread 10 formed in the attachment 7 is preferably of an opposite handedness to the conventional rotation direction so as to auger the resin back toward the blind end 13 of the hole.

The increased diameter of the attachment 7 allows sufficient bonding strength between the resin and the attachment to be achieved to securely locate the bolt in the hole 11. A load plate :14 can then be fitted over the end 4 of the bolt and the nut 5 threaded onto the threaded end to S• •15 thereby tension the bolt.

The thread is preferably formed with a first flank 15 angled toward the bolt 1 and extending in an axial direction by a greater degree than the second 16 flank of the thread so as to maximise compressive load acting on the attachment in a radial direction to thereby serve to further e. 20 secure the attachment to the bolt. The effective diameter of the thread 10 is also sufficient to provide a annulus between the attachment 7 and wall 17 of the hole 11 which allows maximum bonding strength between the resin and the attachment. The remaining portion of the bolt 1 may extend in spaced relation from the wall 17 of the hole, acting as a steel tendon between the attachment 7 and the load plate 14, and need not itself be directly bonded in the hole. Although it has been general practice to fully encapsulate rock bolts with resin, it has been found using the bolt and attachment of the preferred embodiment of the present invention that a sufficient anchorage is provided to securely hold the bolt in place as a result of bonding between the attachment and the resin alone, without the need to fully encapsulate the bolt.

The preferred embodiment of the present invention has been applied in relation to two bolts with a core diameter of 18 mm and 22 mm respectively. The attachment 7 was provided in the form of a heavy steel tube of a length in the order of 300 mm which was fitted over the end of ,qeebolt and subsequently formed thereto, although it should be appreciated any suitable length of tube may be employed. It was found that using the attachment 7 with the above described thread 10 resulted in a bond strength between the bolt 1 and the tube 8 greater than the tensile strength of the bolt 1 alone (nominally 24 tonnes force). The 18 mm diameter bolt 1 was fitted with a 27 mm external diameter tube 8 of 4 mm wall thickness which was rolled to produce a 30 mm diameter attachment 7. The 22 mm diameter bolt 1 was fitted with a 33 mm external diameter tube 8 of 4 mm wall-thickness which was rolled to a 34 mm diameter attachment 7.

Accordingly, the attachment 7 allowed the bolt 1 to be secured in a blind hole 11 using resin for bonding the bolt in place with similar tensile strength characteristics as compared to a conventionally formed steel bolt.

Finally, it is to be understood that the inventive concept in any of its aspects can be incorporated in many different constructions so that the generality of the preceding description is not to be superseded by the particularity of the attached drawings. Various alterations, S. modifications and/or additions may be incorporated into the various constructions and 15 arrangements of parts without departing from the spirit or ambit of the invention.

The term "comprising" (and its grammatical variations) as used herein is used in the inclusive sense of "having" or "including" and not in the exclusive sense of "consisting only of'.

9999 9 00 0

Claims

1. A rock bolt for use in mining, said bolt comprising a bar having a plurality of outwardly extending deformations and being partially located interior of a sleeve, said sleeve being formed onto said bar by deformation of said sleeve to interengage said bar deformations and sleeve interior whereby said interengagement of bar and sleeve both resists longitudinal tensional forces applied to said rock bolt and acting to pull said bar from the interior of said sleeve, and resists rotation of said sleeve relative to said bar.

2. The rock bolt as claimed in claim 1 wherein the deformation of said sleeve deforms said sleeve exterior to create protrusions on said sleeve exterior.

3. The bolt as claimed in claim 1 or 2 wherein that part of said bolt interior of said sleeve substantially fully occupies the interior of said sleeve.

4. The bolt as claimed in any one of claims 1 to 3 wherein said sleeve deformation extends along substantially all the length of said sleeve. The bolt as claimed in any one of claims 1 to 4 wherein said bar deformations extend along substantially the length of said bar. l: S"6. The bolt as claimed in any one of claims 1 to 5 wherein said bar deformations do not comprise a thread. S7. The bolt as claimed in any one of claims 1 to 6 and having said sleeve at one end of said bar.

8. The bolt as claimed in claim 7 and having a thread formed at the other end of said bar.

9. The bolt as claimed in claim 7 or 8 wherein said one end of said bar extends beyond said sleeve. The bolt as claimed in any one of claims 7 to 9 wherein following deformation of said sleeve, said sleeve is open at that end of said sleeve opposite the other end of said bar.

11. The bolt as claimed in any one of claims 2 to 10 wherein said sleeve exterior protrusions comprise a thread.

12. The bolt as claimed in claim 11 wherein said thread has unequal flanks.

13. The bolt as claimed in claim 11 or 12 when either is dependent on claim 8 wherein said threads have opposite hands.

14. The bolt as claimed in any one of claims 1 to 13 wherein said deformation of said sleeve is by cold forming. The bolt as claimed in any one of claims 1 to 14 wherein said deformation of said -sleeve is by rolling.

16. The bolt as claimed in any one of claims 1 to 14 wherein said deformation of said sleeve is by pressing.

17. The bolt as claimed in any one of claims 1 to 16 wherein prior to deformation said sleeve is substantially cylindrical.

18. The bolt as claimed in any one of claims 1 to 17 wherein both said bar and sleeve are formed from steel.

19. The bolt as claimed in claim 18 wherein said sleeve is more malleable than said bar. A rock bolt for use in mining, said bolt being substantially as herein described with reference to Figs 1 to 4 of the drawings.

21. A method of forming a rock bolt for use in mining, said method comprising the steps of: inserting a bar having a plurality of outwardly extending deformations partially into the interior of a sleeve, and deforming said sleeve to interengage said bar deformations with the interior of said sleeve, whereby the interengagement of said bar and sleeve both resists longitudinal tensional forces applied to said rock bolt and acting to pull said bar from the interior of said sleeve and resists rotation of said sleeve relative to said bar.

22. The method as claimed in claim 21 wherein during deformation of said sleeve, the exterior of said sleeve is deformed to create protrusions on said sleeve exterior.

23. The method as claimed in claim 20 or 2lincluding the step of inserting that part of said bar within said sleeve interior substantially fully into the interior of said sleeve.

24. The method as claimed in any one of claims 21 to 23 including the step of deforming said sleeve along substantially all the length thereof. The method as claimed in any one of claims 21 to 24 wherein said bar deformations extend along substantially the length of said bar.

26. The method as claimed in any one of claims 21 to 25 wherein said bar deformations do not comprise a thread.

27. The method as claimed in any one of claims 21 to 26 including the step of locating said sleeve at one end of said bar prior to deformation of said sleeve.

28. The method as claimed in claim 27 including the step of forming a thread at the other end of said bar.

29. The method as claimed in claim 27 or 28 wherein said sleeve is located on said bar with said one end of said bar extending beyond said sleeve. 8 The method as claimed in any one of claims 27 to 29 wherein that end of said sleeve opposite the other end of said bar is open following said deformation of said sleeve.

31. The method as claimed in any one of claims 22 to 30 including the step of deforming said sleeve exterior so that said protrusions comprise a thread.

32. The method as claimed in claim 31 including the further step of forming said protrusions into a thread having unequal flanks.

33. The method as claimed in claim 31 or 32 when either is dependent on claim 28 including the step of forming said threads with opposite hands.

34. The method as claimed in any one of claims 21 to 33 including the step of deforming said sleeve by cold forming. The method as claimed in any one of claims 21 to 33 including the step of deforming said sleeve by rolling.

36. The method as claimed in any one of claims 21 to 33 including the step of deforming said sleeve by pressing.

37. The method as claimed in any one of claims 21 to 36 wherein prior to deformination said S" sleeve is substantially cylindrical.

38. The method as claimed in any one of claims 21 to 37 including the step of forming both said bar and sleeve from steel.

39. The method as claimed in claim 38 wherein said sleeve is more malleable than said bar. A method of forming a rock bolt for use in mining, said method being substantially as herein described with reference to Figs. 1 to 4 of the drawings.

41. A method of installing a rock bolt in a hole drilled in a rock face, said method comprising the steps as claimed in any one of claims 21 to 39 followed by the steps of inserting said rock bolt in said hole, and locating resin or grout between said hole and sleeve whilst maintaining the region between said bar and hole substantially free of said resin or grout.

42. A method of installing a rock bolt in a hole drilled in a rock face, said method being substantially as herein described with reference to Figs 1 to 4 of the drawings. Dated this 30t h Day of September, 2002 INDUSTRIAL ROLLFORMERS PTY LTD By: HODGKINSON OLD McINNES Patent Attorneys for the Applicant