AU733349B2

AU733349B2 - Bearer plate

Info

Publication number: AU733349B2
Application number: AU52749/98A
Authority: AU
Inventors: Keith Vandervliet
Original assignee: Dywidag Systems International Pty Ltd
Current assignee: DSI Underground Australia Pty Ltd
Priority date: 1995-07-28
Filing date: 1998-01-23
Publication date: 2001-05-10
Anticipated expiration: 2015-07-28
Also published as: AU5274998A

Description

Pr S F Ref: 406983 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION

(ORIGINAL)

Name and Address vc Ss-ca s vl .c.

of Applicant: The A4M Corporation Limited 25 Pacific Highway Bennetts Green New South Wales 2290

AUSTRALIA

Inventor(s): Address for Service: Keith Vandervliet Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Bearer Plate The following statement is a full description of this invention, including the best method of performing it known to me/us 3579F/GMM5846 Bearer Plate Technical Field The following invention relates to a bearer plate for use with rock bolts or friction rock stabilisers and in particular to a bearer plate having an increased compression resistance.

Figure 1 of Australian Patent No. 684644, the parent patent of the present application, shows a bearer plate comprising a flat plate having a frustoconical central portion extending therefrom. Impressed into the central portion are a number of indented ribs 8. Formed in the flat plate portion 3 are a number of radial strengthening ribs 17 which extend from the base of the frustoconical portion 7 to the peripheral edge 2 of the flat portion 3. Large versions of such plates have been demonstrated to deform under load conditions. As load is applied to the bearer plate via the upper rim 9 of the frustoconical portion 7, the flat plate 3 tends to raise as shown in Fig. 1 herein. Although this is acceptable for small diameter plates, such deformation is not generally acceptable for larger diameter plates.

In order to address the problem of plate deformation, various attempts have been made at providing improved plates. For example, US Patent 4,112,693 shows a mine roof support plate having a square base portion 12 having a centrally located conical protrusion 14 thereon. A number of strengthening ribs 20 are formed in the side wall of the conical portion 14 to increase the strength of the overall structure. It is envisaged by the present applicant that the plate of US Patent 4,112,693, when loaded, would deform and possibly fail due to the concentration of stresses at the periphery of the flat plate portion 12.

US Patent 4,371,293 again shows a square mine roof bearer plate having a raised 25 conical portion about which there radiates a number of strengthening ribs 60. As the base S.i plate is square, it is envisaged by the present applicant that the plate would undergo stress i concentrations and possible failure under heavy load conditions.

on Object of the Invention S" It is the object of the present invention to overcome or substantially ameliorate the oo 30 above disadvantages and/or more generally to provide an improved bearer plate.

Disclosure of the Invention There is disclosed herein a bearer plate for use with a rock bolt or the like, the bearer plate comprising: a base formed of material having a predetermined thickness, a central portion extending from the base and including an aperture through which said rock bolt or the like can pass, the central portion including a wall, and a plurality of webs extending between the wall and the base, wherein II:\DayLib\LBLL]00857.doc:KEH:AvS the central portion is provided with a plurality of radial indentations circumferentially interposed between said webs.

Preferably, the webs are pressed into the bearer plate Brief Description of the Drawings A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic cross-sectional elevational view of a prior art bearing plate as shown in Australian Patent Application No. 27258/95, Fig. 2 is a schematic perspective view of an improved bearer plate, and Fig. 3 is a schematic cross-sectional elevational view of the bearer plate of Fig. 2.

Description of the Preferred Embodiment In Fig. 2 of the accompanying drawings there is schematically depicted a bearer plate 10. Bearer plate 10 is fabricated from a circular piece of rigid material, typically mild steel or stainless steel for example. However, any suitably strong and rigid material can be used.

The bearer plate 10 comprises a substantially planar circular base portion 3 having a central portion pressed therein, so as to extend upwardly therefrom. The central portion comprises an engagement surface 9 against which a washer surrounding a rock bolt *o Z~ RA [I:\DayLb\LIBLL]oo857docooEH::A5 [I\ayi\LBL005.d**E :V passing through the central aperture A can bear. The central portion also comprises a frustoconical wall 7 as shown.

Impressed or otherwise formed in the frustoconical wall 7 are a number of indentations 16 to increase rigidity of the structure.

Extending between the wall 7 and the planar portion 3 are a number of webs 12.

Each web 12 comprises a pair of opposed faces 13 and 14 separate by a hollow therebeneath. Each web 12 falls short of the peripheral edge 2 by a width W. Width W is typically at least approximately 1.5 times the dimension of the material thickness from which the bearer plate is formed. However, the minimum width W can vary slightly from this.

Likewise, the webs 12 fall short of the bearing surface 9 by a width W which is also dimensioned to be at least approximately 1.5 times greater than the thickness of the material from which the bearer 10 is formed.

It is important to the load bearing characteristics of the bearer plate 10 that the webs 12 stop short of the outside diameter of the base and the top of the cone or central portion to provide "bands" of material 11 and 18 around these locations which remain intact and act as a continuous force transmission member when load is applied.

The provision of the buttresses or webs 12 in combination with the inverted ribs 16 result in the ability to withstand high loads without deformation of the bearer plate 20 When load is applied to the bearing surface 9 by a washer associated with a rock bolt, the load is transferred through the webs 12 to the base portion 3 which bears against the rock **"face. If the frustoconical wall 7 were not stiffened by means of the indentations 16, there would be no matching support for the web 12 at the intersection of the webs 12 with the wall 7. The addition of the inwardly pressed indentations 16 in the frustoconical wall 7 S 25 between the webs 12 gives the support required. The prime purpose for the introduction of the webs 12 is to keep the planar portions 3 of the base plate flat under load for as a high a load as possible. The webs 12 are much more effective in maintaining flatness of the plate portion 3 when the frustoconical wall 7 is stiff. The indentations 6 provide the required stiffness to support the webs 12.

In use as a bearer plate for a rock bolt, the bearer 10 of Fig. 2 is inverted such that its underside surface contacts the rock surrounding the hole from which their extends the threaded end of a rock bolt. This threaded end passes through the aperture A and a nut and washer are applied thereto such that a washer bears against the bearing surface 9.

It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention.

[N:\LBLL00857:KEH

Claims

1. A bearer plate for use with a rock bolt or the like, the bearer plate comprising: a base formed of material having a predetermined thickness, a central portion extending from the base and including an aperture through which said rock bolt or the like can pass, the central portion including a wall, and a plurality of webs extending between the wall and the base, wherein the central portion is provided with a plurality of radial indentations circumferentially interposed between said webs.

2. The bearer plate of claim 1, wherein the webs are pressed into the bearer plate.

3. A bearer plate, substantially as hereinbefore described with reference to Figs 2 and 3 of the accompanying drawings. 1i Dated 18 January, 2001 The ANI Corporation Limited Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON *S S o *oo [I:\DayLib\LILL]00857.doc:YEH:AVS