AU767584B2

AU767584B2 - Deformable bearing plate

Info

Publication number: AU767584B2
Application number: AU48942/00A
Authority: AU
Inventors: Peter Dr. Gray
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-08-02
Filing date: 2000-08-01
Publication date: 2003-11-20
Anticipated expiration: 2020-08-01
Also published as: AU4894200A

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

TO BE COMPLETED BY APPLICANT Name of Applicant: Actual Inventor(s): Address for Service: EVELYN FRANCES GRAY 1 ADDRESS FOR SERVICE ALTERED p

AT-

Dr. Peter Gray y tF SIf"TtNA I f I 1T High Street, Kew, Victorit 3101, Australia.

Invention Title: DEFORMABLE BEARING PLATE The following statement is a full description of this invention, including the best method of performing it known to me:- 31/07/00,all0767.l 1,1 Deformable Bearing Plate Field of the Invention The present invention relates to a bearing plate for use with rock bolts. More particularly, the present invention relates to a deformable bearing plate designed to accommodate uneven rock surfaces.

Background to the Invention Rock excavation is a principle activity of mining and tunnelling operations worldwide. For the tunnelling industry, this is typically undertaken with a tunnel-boring machine in soft to 10 medium strength rocks. Tunnel boring machines generally excavate a round opening with usually smooth rock walls, which are subsequently supported by bolts, bearing plates, i: shotcrete, concrete linings, or other support method. However, if the tunnel-boring machine encounters excessively weak or strong rock, then the tunnel walls can be uneven and irregular.

In the underground coal industry, continuous miner machines excavate roadways in a coal seam. The sedimentary nature of coal enables a clean split to be made between the top of the coal seam and the overlying roof rock thus creating a flat roof However, the side walls of the opening are excavated in coal which is often weak, and can fracture along uneven surfaces.

This creates uneven side walls or "ribs" in coal roadways. oooo In the underground metal mining industry, rock excavation is often undertaken in very strong rocks with compressive strengths up to 300 MPa. In this case, blasting is the only practical method to break the rock, which is subsequently removed with front-end loader type machine.

In this case the surface of the rock excavation is also uneven.

The most efficient method to support underground rock excavations is to use rock bolts, and S 25 virtually every rock bolt used around the world requires a bearing plate. The bearing plate is typically retained on the exposed end of the bolt by a nut, forged head or welded collar.

However, most bearing plates have a flat, planar surface which contacts the exposed rock face.

For example, wooden bearing plates are commonly made from either hardwood or from plywood which is flat, and square or rectangular with a central hole drilled through it to accommodate the rock bolt. Plastic bearing plates are typically round, and with a flat face against the exposed rock face, while steel bearing plates are often square, flat pieces of steel sometimes with a central domed section around the central hole. Other steel bearing plates, such as thin steel plates, have reinforcing ribs and a domed shape to increase strength, but still have a planar contact face with the rock. All these plates have some form of planar contact surface, which may be discontinuous, which contacts the rock surface.

Where the above bearing plates are installed against an irregular rock face, the contact points between the rock face and the bearing plate can be very small. Under high loads, this can cause wooden and plastic bearing plates to fail prematurely. This particularly occurs where the contact points are near the outside of the bearing plate since this generates a high bending moment on the plate. Where flat steel plates are in contact with an irregular rock face and are under high load, excessive bending of the entire plate can occur, leading to premature failure.

It is the object of the present invention to provide a deformable bearing plate that can accommodate an irregular rock surface such that the rock face can be retained by the bearing plate without causing premature failure of the entire bearing plate. Under an applied load, where the bearing plate is in contact with an irregular rock face, the bearing plate deforms such as to increase the total contact area until the resisting contact stresses of the bearing plate decrease. In this way, the applied load is spread over a much larger contact area with the rock face than the initial contact area.

Summary of the Invention According to the present invention, there is provided a bearing plate including an outer member covering a deformable inner member, the deformable member in use, conforming to the shape of the surface onto which it abuts and wherein the bearing plate is adapted to receive a fastening means to allow the bearing plate to be fastened to said surface.

Preferably, the deformable member is selected from at least one row of bristles or fins, said at least one row having at least one fin or bristle wherein said at least one fin or bristle is of a suitable thickness and strength. More preferably, the deformable member is a plurality of spaced apart rows of fins which intersect one another in a substantially perpendicular manner through a series of slots, said slots having a suitable depth, wherein the depth of the slots is variable to provide additional strength to the deformable member. The invention also extends to the deformable member comprising a series of rows of fins which are joined together to reinforce each other.

Preferably, the outer member has a substantially domed internal surface and a circumferential flange. More preferably, the at least one row of fins has a profile complementary to the substantially domed internal surface of the bearing plate, said plurality of rows of fins is in continuous contact with the internal surface of the outer member.

Preferably, the outer member is selected from a rigid, partially rigid or deformable outer member.

In one preferred form of the invention, the outer member is a partially rigid outer member including a rigid bell-shaped central portion edged by a deformable circumferential flange. In a further preferred form of the invention, the outer member is a deformable outer member including a deformable bell-shaped central portion edged by a deformable circumferential flange. Typically, a deformable circumferential flange is included to help prevent any loose or broken rock from falling away from underneath the bearing plate. In this way, progressive deterioration of the rock face under the bearing plate either due to high stress, movement or weathering is minimised. Any loose or broken rock that does separate from the rock face beneath the bearing plate is retained between the fins and this helps to provide additional reinforcement to the plate.

Preferably, the fastening means is a rock bolt which is drilled into a rock surface on which said deformable inner member rests. Preferably, the deformable inner member progressively deforms under applied high contact stresses, until the imposed load on the bearing plate is resisted by the contact stresses.

Preferably, the number and thickness of the fins may be varied depending on the size of the applied load. Where an increased resistance to an applied load is required, the number and thickness of the fins is increased.

Preferably, the deformable inner member enables irregular rock surfaces to be successfully retained by accommodating an irregular rock surface and spreading the imposed load on the bearing plate over a larger contact area than is possible with a rigid bearing plate on an irregular rock surface. Such a deformable inner member will prevent high bending moments from occurring in a bearing plate.

In a preferred embodiment of the invention, there is provided a bearing plate having an outer member which includes a partially rigid outer member covering rows of perpendicularly intersecting deformable fins, wherein the fins are in continuous contact with an irregular rock surface. In a particularly preferred embodiment, the fins form an integral part of the structural design of the bearing plate. Preferably, the fins are tapered away from the rock surface. More preferably, the perpendicularly intersecting rows of fins are in the form of a one-piece moulding, which is integral with the partially rigid outer member.

Preferably, the fins are formed from any suitable material, but the material is typically selected from foam, rubber or plastic. Preferably, the outer member is formed from any suitable material but the material is typically selected from wood, plastic or steel.

The invention is further explained by means of the following non-limiting drawings: 10 Description of the Drawings Figure 1 is a plan view of the outer member of the bearing plate in accordance with the present invention Figure 2 is a plan view of the underneath of the bearing plate showing the deformable inner member covered by the outer member in accordance with the present invention Figure 3 is a perspective view of the outer member of the bearing plate of the present invention ooe, Figure 4 is a perspective view of the underneath of the bearing plate showing the deformable inner member covered by the outer member in accordance with the present invention.

Figure 5 is a side-on view of the outer member of the bearing plate of the present invention.

S 20 Figure 6 is a cross-sectional view along and in the direction of arrow A-A in Figure Detailed Description of the Preferred Embodiment of the Invention In the drawings, the same numerals have been used to designate similar integers in each figure to avoid duplication of description.

The bearing plate (10) of the present invention comprises an outer member (11) and a deformable inner member such that the outer member (11) covers the inner member The bearing plate (10) is adapted to receive a rock bolt through an opening (14) in the outer member (11) to fasten the bearing plate (10) to the rock surface.

The deformable inner member (16) comprises at least one row of fins (20) having a suitable number of fins and being of a suitable thickness and strength. The rows of fins perpendicularly intersect one another through a series of slots (26) to constitute the deformable inner member The outer member (11) is substantially helmet-shaped having a bell-shaped central portion (13) and a circumferential flange The outer member (11) is formed with a domed internal surface (22) and a circumferential flange The row of fins is in continuous contact with the domed internal surface (22) of the outer member (11).

In use, the bearing plate (10) is fastened to the rock surface by means of a rock bolt through the opening (14) of the outer member (11) and the deformable inner member (16) conforms to the shape of the rock surface to which it abuts. The number of fins in each row of fins 0 may be increased and the thickness and strength of the fins may be altered according to the imposed load on the bearing plate. The row of fins (20) may also be a row of deformable I: bristles such that when a load is applied to the bearing plate the imposed load on the bearing plate (10) is spread over a larger contact area. The row of fins may comprise one 15 continuous fin, having no slots.

The outer member (11) may be rigid, partially rigid or deformable. In the rigid form, the bellshaped central portion (13) and the circumferential flange (12) of the outer member (11) are both rigid and made of a non-deformable material such as steel, wood or non-deformable plastic. In the partially rigid form, the bell-shaped central portion (13) is rigid, but the circumferential flange (12) of the outer member (11) is made from a deformable material such as a flexible plastic material. In the deformable form, both the bell-shaped central portion (13) and the circumferential flange (12) of the outer member (11) are made from a deformable material such as a flexible plastic material.

Those skilled in the art will appreciate that the invention described herein is susceptible to 0 variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions, and compounds referred to or indicated in this specification (unless specifically excluded) individually or collectively, and any and all combinations of any two or more of said steps or features.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated integer or group of integers, but not to the exclusion of any other integer or group of integers.

Where the specification refers to a "bristle" or to a "fin", it is to be understood that the invention includes all such variations and modifications of the above, and any other single or multiple deformable element that could be used to provide a system that would provide an increasing contact area with an irregular rock surface under an increasing imposed load.

Where the specification refers to a "bearing plate" it is to be understood that the invention includes all such variations and modifications of a "bearing plate" but is not limited to these alone and includes one or many "plates", "straps", or "collars"

Claims

1. A bearing plate including an outer member covering a deformable inner member, the deformable member in use, conforming to the shape of a surface onto which it abuts and wherein the bearing plate is adapted to receive a fastening means to allow the bearing plate to be fastened to said surface.

2. A bearing plate according to claim 1, wherein the deformable member is selected from at least one row of bristles or fins, said at least one row having at least one fin or bristle wherein said at least one fin or bristle is of a suitable thickness and strength.

3. A bearing plate according to claim 2, wherein the deformable member is a plurality of rows of fins which intersect one another in a substantially perpendicular manner through a series of slots, said slots having a suitable depth wherein said depth is variable to provide additional strength to the deformable member.

4. A bearing plate according to claim 1 or claim 2, wherein the deformable member 9 comprises a series of rows of fins wherein said fins are joined together to reinforce each other. eo. A bearing plate according to any one of claims 1 to 4, wherein the outer member has a substantially domed internal surface and a circumferential flange.

6. A bearing plate according to claim 5, when appended to claim 2, wherein the at least one row of fins has a profile complementary to the substantially domed internal surface of the bearing plate, said plurality of rows of fins being in continuous contact with the internal surface of the outer member.

7. A bearing plate according to claim 5 or claim 6, wherein the outer member is selected from a rigid, partially rigid or deformable outer member.

8. A bearing plate according to claim 7, wherein the outer member is a partially rigid outer member including a rigid bell-shaped central portion edged by a deformable circumferential flange.

9. A bearing plate according to claim 7, wherein the outer member is a deformable outer member including a deformable bell-shaped central portion edged by a deformable circumferential flange. 9 A bearing plate according to any one of claims 1 to 9, wherein the fastening means is a rock bolt which is drilled into a rock surface on which said deformable inner member rests.

11. A bearing plate according to claim 7, wherein the outer member includes a partially rigid outer member covering rows of perpendicularly intersecting deformable fins, wherein the fins are in continuous contact with an irregular rock surface.

12. A bearing plate according to claim 11, wherein the fins form an integral part of the structural design of the bearing plate.

13. A bearing plate according to claim 12, wherein the fins are tapered away from the rock surface.

14. A bearing plate according to any one of claims 11 to 13, wherein the perpendicularly intersecting rows of fins are in the form of a one-piece moulding, which is integral with the partially rigid outer member. DATED this 1 st day of August 2000 4' EVELYN FRANCES GRAY By her Patent Attorney CALLINAN LAWRIE S 20 A,