AU732599B2

AU732599B2 - A roof bolt nut

Info

Publication number: AU732599B2
Application number: AU45231/97A
Authority: AU
Inventors: John Ross Allen; Ian Cribb; Jeffrey Phillip Crowe; Thomas Charles Woods
Original assignee: Dywidag Systems International Pty Ltd
Current assignee: DSI Underground Australia Pty Ltd
Priority date: 1996-11-15
Filing date: 1997-11-17
Publication date: 2001-04-26
Anticipated expiration: 2017-11-17
Also published as: AU4523197A

Description

S F Ref: 400574

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Thomas Charles Woods 4 Yaringa Lane Carey Bay New South Wales 2283

AUSTRALIA

John Ross Allen 58 Lake Road Swansea New South Wales 2281

AUSTRALIA

Jeffrey Phillip Crowe 3 Little Stewart Street Paddington New South Wales

AUSTRALIA

2021 lan Cribb 7 Northminster Way Rathmines New South

AUSTRALIA

Wales 2283 Actual Inventor(s): Address for Service: Invention Title: Thomas Charles Woods, John Ross Crowe and lan Cribb Allen, Jeffrey Phillip Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia A Roof Bolt Nut ASSOCIATED PROVISIONAL APPLICATION DETAILS [311 Application No(s) [33] Country P03674 AU P05007 AU [32] Application Date 15 November 1996 7 February 1997 -1- A Roof Bolt Nut Technical Field The present invention relates to the manufacture of bolt nuts and more particularly but not exclusively to roof bolt nuts used in the mining industry.

Background of the Invention In the mining industry nuts are applied to roof bolts and need to be tensioned to a required minimum torque. It is also necessary not to over tension the roof bolt.

When inspecting the roof bolts it is difficult to determine whether the nut has been tensioned to within specification.

In addition to the above, roof bolts do not affectively aid in the mixing of the chemical adhesives which secure the roof bolt to the rock layer penetrated by the roof bolt.

Object of the Invention It is the object of the present invention to overcome or substantially ameliorate the above disadvantage, or at least a useful alternative.

Summary of the Invention There is disclosed herein a nut to engage a bolt to drive and tension the bolt, said nut having a body including: a threaded part having a threaded passage to threadably engage the bolt; 20 a drive part having a drive part passage aligned with the threaded passage so that the bolt can pass through the threaded passage to enter the drive part passage, said drive part further including an obstruction extending across said drive part passage to engage the bolt so that a torque applied to said drive part will cause rotation of the bolt with the drive part until the torque exceeds a first predetermined torque at which said obstruction 00 25 is displaced to permit said bolt to pass through said drive part so that said bolt can be :*tensioned; and intermediate portion of a smaller cross-sectional area relative to said drive part so that said intermediate portion ruptures to permit separation of the threaded part from the drive part when said torque exceeds a second predetermined torque, which second torque is greater than said first torque.

[R:\LIBLL 10543specie.doc:keh -2- Brief Description of the Drawings A preferred form of the present invention will now be described by way of example only with reference to the accompanying drawings wherein: Figure 1 is a schematic plan view of a mine strata control roof bolt stear nut; Figure 2 is a schematic sectioned side elevation of the nut of Figure 1; and Figure 3 is a schematic sectioned side elevation of a modification of the nut of Figure 1.

Detailed Description of the Preferred Embodiment In Figures 1 and 2 of the accompanying drawings there is schematically depicted a mine strata control roof bolt shear nut 10. The nut 10 includes an elongated body 11.

The body 11 has a threaded part 12 which is internally threaded so as to have threads 13 to threadably engage a roof bolt. The thread 13 surround a central passage 14 extending along the longitudinal axis 15 of the nut The body 11 further includes a drive part 16 having flat longitudinally extending drive surfaces 17 which enable the drive part 16 to be gripped by an instrument to apply a torque to the nut 10 to tension the roof bolt. The drive part 16 has a central passage aligned with the passage 14, which is dimensioned to allow the roof bolt to pass l therethrough without. interference.

The body 11 further includes an intermediate portion 18 which is of a smaller cross sectional area, which cross sectional area is transverse of the longitudinal axis The smaller cross section is provided by forming a groove 19 in the body 11.

~When sufficient torque is applied to the drive part 16, the intermediate portion 18 ruptures so that the drive part 16 separates from the threaded part 11. Accordingly, no further torque can be transmitted. This also provides a means enabling visual inspection .25 of the nut 10 to determine whether it has been tensioned to the required specification.

Thus a positive visual indication is provided at time of installation. The intermediate portion 11 would be dimensioned to determine the magnitude of the torque at which the o intermediate portion 18 ruptures.

o ooo In Figure 3, there is schematically depicted a modification of the roof bolt sheer nut 10. In this embodiment, the body 11 is provided with an end cap 21 which for example, may be formed integral with the body 11 and located at the end of the drive part 16. Preferably, adjacent the junction of the end cap 21 and body 11 there is provided an annular groove 22, which would act as a stress raiser to aid in displacement of the cap 21.

SThe cap 21 closes the passage [R:\LIBLL] 10543specie.doc:keh -3- In use of the nut 10 of Figure 3, a bolt engaged by the nut 10 would threadably engage within the passage 14 and ultimately abut the cap 21. Thereafter, the application of torque to the nut 10 will cause rotation of the bolt. When sufficient torque is applied to the drive part 16, the cap 21 becomes dislodged relative to the body 11, sothat the bolt s may pass through the passage 20, that is, so that the bolt may pass longitudinally through the nut 10. In the case of a roof bolt, when the nut is engaged with the cap 10, the roof bolt will rotate thereby mixing the chemical adhesive located within the rock passage that the bolt is located. As the adhesive reacts and begins to fix the roof bolt to the surrounding rock structure, the torque applied to the nut 10 will increase. When sufficient torque is applied, the cap 21 is displaced relative to the body 11 allowing the threaded part 12 to pass down the roof bolt and tension the bolt. Ultimately, when a greater torque is reached, the drive part 16 will separate from the threaded part 11, as discussed with reference to Figures 1 and 2.

It should further be appreciated in respect of the embodiment of Figure 3, the end cap 21 could be used in conjunction with a standard roof bolt not having the groove 19.

The cap 21 is an obstruction engaged by the bolt to cause rotation of the bolt to mix the adhesive within the rock passage occupied by the bolt. The obstruction (cap 21) extends i transverse with respect to the passage 20, adjacent an end thereof.

o* 0..

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Claims

1. A nut to engage a bolt to drive and tension the bolt, said nut having a body including: a threaded part having a threaded passage to threadably engage the b6lt; a drive part having a drive part passage aligned with the threaded passage so that the bolt can pass through the threaded passage to enter the drive part passage, said drive part further including an obstruction extending across said drive part passage to engage the bolt so that a torque applied to said drive part will cause rotation of the bolt with the drive part until the torque exceeds a first predetermined torque at which said obstruction 0to is displaced to permit said bolt to pass through said drive part so that said bolt can be tensioned; and an intermediate portion of a smaller cross-sectional area relative to said drive part so that said intermediate portion ruptures to permit separation of the threaded part from the drive part when said torque exceeds a second predetermined torque, which second torque is greater than said first torque.

2. The nut of claim 1, wherein said obstruction is a cap closing the drive part passage. i

3. The nut of claim 1 or 2, wherein the obstruction is located adjacent an end of the drive part remote from said threaded part. o* 20

4. The nut of claim 1, 2 or 3 wherein a stress raiser is located adjacent the SO• ~obstruction to aid in displacement of the obstruction.

5. The nut of claim 4, wherein the stress raiser is an annular groove.

6. The nut of any one of claims 1 to 5, wherein the cross sectional area of said intermediate portion is smaller than the cross sectional area of the drive part and the threaded part.

7. A nut substantially as herein described with reference to any one of the embodiments of the invention shown in the accompanying drawings. S• Dated

8 February, 2001 oooe• S" Thomas Charles Woods John Ross Allen Jeffrey Phillip Crowe lan Cribb Patent Attorneys for the Applicant/Nominated Persons J SPRUSON FERGUSON [R:\LIBLL] I 0543specie.doc:keh