AU2004202519B2 - Friction bolt - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE

SPECIFICATION

FOR A STANDARD

PATENT

ORIGINAL

Name of Applicant: Actual Inventor: Address for Service: Invention Title: INDUSTRIAL ROLL FORMERS PTY

LIMITED

JEFFREY ROBERT

FERGUSSON

FRASER OLD SOHN Patent Attorneys Level 6, 118 Alfred Street MILSONS POINT NSW 2061 FRICTION

BOLT

Details of Basic Application(s): Australian Provisional Patent Application No. 2003 902 963 Filed 13 June 2003 The following statement is a full description of this invention, including the best method of performing it known to us: FIELD OF THE INVENTION The present invention relates to rock bolts and, in particular, to friction bolts.

BACKGROUND

ART

Friction bolts are widely used in mining to stabilize rock surfaces. In particular, in order to protect underground workers steel mesh is secured to overhead rock surfaces in order to prevent any sizeable rock pieces which may become dislodged from the rock surface from falling down and injuring such workers.

Typically, a sheet of steel mesh is secured in place using several friction bolts, then more rock is removed to create a fresh overhead surface. Next another sheet of mesh is overlapped with the preceding sheet, secured in place with friction bolts, and so on.

One popular size of friction bolt has a nominal outer diameter of 47mm and is thus dimensioned to be received in a blind hole of nominal diameter 45mm. The wall thickness of the sheet steel from which the 47mm friction bolts if fabricated is 3.2mm so the nominal internal diameter of the 47mm friction bolt before installation is 40.6mm. An installation tool, having a main body from which projects a spigot of approximately 40mm diameter, is provided to enable the friction bolt to be repeatedly longitudinally driven in pile driver fashion. The trailing end of the friction bolt is provided with a steel ring welded to the longitudinally slit tube from which the bolt is formed. The steel ring of internal diameter approximately 47mm distributes the force of the blows from the installation tool and prevents the trailing end of the friction bolt becoming too deformed or damaged during installation.

Once installed, the friction bolt is compressed by the hole and its hoop strength urges the bolt to expand radially, thereby providing a strong force resisting longitudinal extraction of the bolt. Thus after installation, the internal diameter of the 47mm friction bolt is reduced so as to be less than 40.66mm.

It so happens that another popular size of friction bolt has an uninstalled outer diameter of 40mm and is intended to be installed within a hole of nominal 38mm diameter. The 40mm friction bolt is provided with a steel ring of internal diameter 2945DC-AU approximately 40mm at its trailing end. Since the wall thickness of the steel from which the 40mm friction bolt is fabricated is 2.33mm, the interior diameter of the friction bolt before installation is approximately 35mm. Thus the friction bolt is intended to be driven by an installation tool having spigot of approximately 33mm diameter.

It follows from above, that after installation of a 47mm friction bolt into a hole, a 40mm friction bolt can then be inserted into the 47mm bolt. This is exactly what is done at the overlap of the individual sheets of mesh since it saves the need for drilling further holes in the rock face.

However, in order to carry out the installation of the 40mm friction bolt, the 47mm friction bolt installation tool has to be removed from the installing machine and the 40mm friction bolt installation tool fitted. This has long been regarded as a tiresome procedure by the machine operators.

OBJECT OF THE INVENTION It is a desirable objective to save time during this mesh installation procedure.

Since the installation tool for the 47mm bolt is always on the machine when the 40mm bolts have to be installed, various attempts have been made to try and make an installation tool which is able to install both sizes of the bolt. To date, all such attempts have failed.

SUMMARY OF THE INVENTION The present invention is based on the realization that instead of finding an installation tool which will install both sizes of bolt, it is more expedient to modify the trailing end of the 40mm bolt so that it can be installed by the 47mm bolt installation tool. Of course, once this insight has been grasped, it will be appreciated that the bolt modification is not limited to any specific bolt size, or pair of bolt sizes.

In accordance with a first aspect of the present invention there is disclosed a friction bolt comprising a longitudinally slit tube of first nominal outer diameter having a leading end and a trailing end, said trailing end being enlarged and provided with a support ring having an internal diameter larger than said first diameter and 2945DC-AU gZ-LO-9OZ2(P-nY-A) 0180 LtSL (wu:H) OWljIRlsflV dl Aq POA!030H 99L661.-SOHV :o0 C sLAJOS 00 3 2945 DC-AU corresponding to the nominal outer diameter of a larger size friction bolt, whereby an Cl installation tool dimensioned to he received by said larger size bolt can be used to install said bolt of first nominal outer diameter.

V) 5 Preferably the first nominal outer diameter is substantially 40mm and the support o ring internal diameter is substantially 47mmn.

O In accordance with a second aspect of the present invention there is disclosed a Cl method of installing a smaller size friction bolt in the interior of a previously installed larger size friction bolt utilizing the installation tool used to install said larger size bolt, said method comprising the step of enlarging the wrailing end of said smaller size bolt to mate with said larger bolt size installation tool.

BRIEF DESCRIPTION OF TI-E DRAWINGS An embodiment of the present invention will now be described with reference to the drawings in which: Fig. I is a schematic perspective view showing installation of a smaller size friction bolt in the interior of a previously installed larger size friction bolt, Fig. 2 is a longitudinal cross-sectional view through the pair of installed bolts, Fig. 3 is a side view of the smaller size bolt, Fig. 4 is a perspective view of the smaller size bolt, and Fig. 5 is a plan view of the smaller si ze bolt.

DETAILED DESCRIPTION In Fig. I as tunnelling, for example, in mine proceeds, a first sheet 1 of steel mesh is secured to the exposed rock surface 2. This installation is via relatively long 47mm size conventional friction bolts 3, the primary furnction of which is control of the rock strata to prevent cave-ins, collapse of the rock surface 2, and the like. A secondary consideration is that the conventional bolts 3 retain the mesh 1.

Once the first sheet 1 has been installed, further excavation of rock takes place and then a second sheet 21 is overlapped with the sheet 1 and secured in place. This process is repeated and a third sheet 31 of steel mesh is then installed, and so on.

-4- C d c -d ~02S966a0 IWH0S OF-U a-10 MIJSUdA 9:98021C9 sc:sT aooa jnr sa The conventional bolts 3 are installed in the conventional way following drilling of a 45mm hole and driving of the bolt and its associated apertured plate 4 by means of a conventional 47mm driver 5 having a spigot 6. The spigot 6 passes into the interior of the bolt 3 and the body of the driver 5 bears against a steel ring 8 welded to the trailing end 9 of the bolt 3.

When a subsequent sheet 21, 31 of mesh is to be initially attached to the rock face 2, instead of using a conventional rock bolt of 40mm nominal diameter and changing the driver 5, the driver 5 is left as is and a modified rock bolt 13 is used.

The modified bolt 13 is formed in substantially conventional fashion being rolled to form a slit tube 15 (Fig. However, the trailing end of the tube 15 is belled at 16, or radially outwardly expanded, so as to snugly fit inside a steel ring 18 which is the same size as the ring 8. The ring 18 is welded to the expanded bell 16.

In this way, utilizing another plate 4 of the same size as used for bolt 3, the smaller bolt 13 can be driven by the driver 5 into the interior of the bolt 3 to arrive at the installed pair illustrated in Fig. 2.

Since the bolt 13 is only required to hold the mesh, and does not have a rock strata control role, it can be short in order to save expense. However, the bolt 13 can be of any length so long as it is shorter than the bolt 3.

As seen from Fig. 2, the plates 4 neatly overlie the rings 8, 18 and securely hold the overlapped pair of mesh sheets. One size plate 4 can be used for both bolts 3, 13 instead of two different sized plates previously thereby saving on inventory.

The bolt 13 is easily fabricated using the traditional method, however, before welding the conventional sized ring to the tube 15, the trailing end of the tube is expanded to snugly fit the ring 18. Then the ring 18 is welded to the expanded tube.

This low cost procedure which adds slightly to the fabricated cost of the bolt 13 is more than offset by the operator being saved the time and drudgery of having to change drivers to one of a different size.

2945DC-AU The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention. For example, a range of friction bolts all having different diameters and intended to be driven into different sized holes can be produced, all of which can be driven by the same driver.

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'.

2945DC-AU

Claims (7)

1. A friction bolt comprising a longitudinally slit tube of first nominal outer diameter having a leading end and a trailing end, said trailing end being enlarged and provided with a support ring having an internal diameter larger than said first Cl 5 diameter and corresponding to the nominal outer diameter of a larger size friction ci bolt, whereby an installation tool dimensioned to be received by said larger size o belt can be used to install said bolt of first nominal outer diamnetcr, o2. The friction bolt as claimed in claim 1 wherein said first nominal outer diameter is substantially 40mm and said support ring internal diameter is substantially 47mm.

3. The bolt as claimed in c lai m I or 2 wherein said enlarged trailing end is expanded.

4. The bolt as claimed in any one of claims 1-3 and fabricated from sheet steel. The bolt as claimed in claim 4 wherein said support ring is welded to said enlarged trailing end.

6. A friction bolt having an expanded trailing end and being substantially as herein described wit reference to the drawings.

7. A method of installing a smaller size friction bolt in the interior of a previously installed larger size friction bolt utilizing the installation tool used to install said larger size bolt, said method comprising the step of enlarging the trailing end of said smaller size bolt to mate with said larger bolt size installation tool.

8. The method as claimed in claim 7 wherein said trailing end is enlarged by radially expanding the trailing end of' a split tube from which said smaller size bolt is fabricated.

9. The method as claimed in claim 8 or 9 including the step of affixing a steel ring to the enlarged trailing end. A method of installing a smaller size friction bolt in the interior -of a previously installed larger size friction bolt utilizing the installation tool used to install the larger size bolt, said method being substantially as herein described with reference to the drawings. 7 00LaSS68Z0 bJHOS OWU 0-10 ?I3SUNI cST80 ICS sc:sT aooa inr sa I S~Z-LO-9Q& (P-wY-Ak) aea Lt7:gL aw Ilj IMlV dl Aq pOAIQaoj 966L-SONV ON CI SIJO 2945DC-AU Dated this 25th clay of July 2008 INDUSTRIAL ROLL FORMERS PTY LIMKITED By FRASER OLD SOHN Patent Attorneys for the Applicant q d sd 00L2ss6820 WHi-OS GNU a110 MIJSUdA ss:sT oo inn sa