WO2000047871A1

WO2000047871A1 - Rock anchor

Info

Publication number: WO2000047871A1
Application number: PCT/IB2000/000130
Authority: WO
Inventors: Grant Spencer Gore
Original assignee: Grant Spencer Gore
Priority date: 1999-02-11
Filing date: 2000-02-07
Publication date: 2000-08-17
Also published as: AU2125200A

Abstract

The invention provides a rock anchor which is adapted to be inserted into a drill hole or the like to be anchored therein, comprises an elongated body member which defines a longitudinal wedging surface, such wedging surface tapering outwardly in the direction of the leading end of the anchor, and a wedging member which defines a sliding surface which co-operates slidingly with the wedging surface, so that the wedging member is movable along the wedging surface from a first retracted position wherein it is disposed generally co-extensively with, or within, the lateral extent of the body member, and an extended position wherein it extends laterally from the body member to engage the inner surface of the drill hole and to wedge the body member within the drill hole; and actuator means for moving the wedging member to its extended position in use.

Description

ROCK ANCHOR

Technical Field

THIS invention relates to a rock anchor suitable for, but not limited, use in

mining operations.

Background Art

Rock anchors are commonly used in underground mining to provide securing

points for equipment and services, bolting of the rock face, lacing and netting

and the like. Conventional rock anchors define jaw formations which are

expanded outwardly by means of a central axially threaded cone which moves

along a threaded shank upon rotation of the latter. Such arrangements are

complex and costly. An alternative arrangement includes a cam member which

is pivotally mounted to a shank for outward angular movement into engagement

with the interior of a drill hole. Such arrangements are also relatively complex,

and the loading of the bolt is dependent on the strength of a pivot pin. Objective of the Invention

It is an object of the present invention to provide a rock anchor of a robust and

relatively inexpensive construction. A further object of the invention is to

provide such a rock anchor which will be capable of a relatively high loading.

Disclosure of the Invention

According to the invention, a rock anchor which is adapted to be inserted into

a drill hole or the like to be anchored therein, comprises an elongated body

member which defines a longitudinal wedging surface, such wedging surface

tapering outwardly in the direction of the leading end of the anchor, and a

wedging member which defines a sliding surface which co-operates slidingly

with the wedging surface, so that the wedging member is movable along the

wedging surface from a first retracted position wherein it is disposed generally

co-extensively with, or within, the lateral extent of the body member, and an

extended position wherein it extends laterally from the body member to engage

the inner surface of the drill hole and to wedge the body member within the drill hole; and actuator means for moving the wedging member to its extended

position in use. In one arrangement the actuator means could be in the nature

of gripping means associated with the wedging member and adapted to move

the wedging member towards its extended position when the body member is

moved in a direction withdrawing the body member from the drill hole.

Preferably the wedging member will be in the form of an elongated wedge

which tapers inwardly towards its leading end to mate with the profile of the

wedging surface of the body member in a complementary fashion.

Further according to the invention the gripping means comprises a finger

element which extends laterally from the wedging member and which is adapted

to engage the inner surface of the drill hole in order to move the wedging

member to its extended position. Thus in a preferred arrangement, the finger

element will be a resilient element which is preferably angled towards the

trailing end of the body member. It is envisaged that the resilient finger

element could project from a cradle formation which is adapted to receive at

least part of the wedging member. Such cradle formation could thus be

interposed between the wedging member and the wedging surface. Also according to the invention, an attachment formation is provided at or

towards the trailing end of the body member, the attachment formation being

adapted to mate with a corresponding formation for securing a chain, cable,

shank or the like, to the body member. The securing formation could for

example be in the form of a clevise formation, tongue formation, socket

formation, spigot formation, or the like.

A further feature provides for the wedging member to be held slidingly within

the wedging surface by means of a flexible collar, band or the like.

Brief Description of the Drawings

Figure 1 is a schematic perspective view of a rock anchor in accordance

with the invention;

Figure 2 is a schematic perspective elevation of the anchor in Figure 1 with

a wedge thereof in a retracted position;

Figure 3 is a schematic perspective elevation of the anchor in Figure 1 in

an extended position; and Figure 4 is a schematic illustration of the rock anchor in Figure 1 in

position within a drill hole or the like.

In order more clearly to illustrate the invention, a preferred embodiment thereof

is described hereunder purely by way of example with reference to the

accompanying drawings. Referring to the drawings, a rock anchor 10 in

accordance with the invention comprises an elongated body member 11 of

generally cylindrical configuration.

It is a feature of the invention that an elongated longitudinal wedging surface

12 will be defined on the outer surface of the body member 11, the wedging

surface 12 tapering outwardly towards the leading end 11a of the body member

11. In the arrangement illustrated, the wedging surface 12 is substantially

linear in longitudinal section, but if desirable a curved or cam-like surface, not

shown, can be provided.

The rock anchor further includes a wedging member 15 which is adapted to

mate with the wedging surface 12 in sliding relationship to be movable from a

retracted position, Figure 2, wherein the wedging member 15 is substantially co-extensive with the lateral extent of the body member 11, and an extended

position, Figure 3, wherein the wedging member 15 is longitudinally displaced

towards the leading end 11a of the body member 11 to extend laterally

therefrom.

In the arrangement illustrated, the wedging member 15 is in the form of an

elongated wedge 15 which tapers from a wider trailing end 15a to a narrower

leading end 15b to match the taper of the tapered surface 12 of the body

member 11, so that the wedge 15 is receivable within the recess defined by the

wedging surface 12.

The invention further provides for actuator means in the form of a resilient

finger formation 14 which extends laterally from the wedging formation 15 to

be secured to the latter, and adapted to engage the inner surface 17a of a drill

hole 17, Figure 4, so as to move the wedging formation 15 to its extended

position, when the body member 11 is moved in a direction out of the drill hole

17. Preferably, the finger formation 14 will be angled in the direction of the

mouth zone of the drill hole 17, or in other words towards the trailing end 15a

of the wedge 15 to ensure a positive engagement with the inner wall 17a of the

drill hole 17. In the arrangement illustrated, the resilient finger formation 14 is disposed in the region of the leading end 15b of the wedge 15, and extends

from a cradle formation 14a within which the wedge formation 15 is seated.

The cradle formation 14a is thus interposed between the wedging surface 12 and

the lower surface 15c of the wedge 15.

Alternatively, the actuator means could comprise a rod or the like, not shown,

which is adapted to be operated manually to move the wedge 15 to its extended

position. In a further alternative arrangement, the actuator means could

comprise biasing means which is adapted to act between the trailing end 15a of

the wedge 15 and the step 12a defined by the wedging surface 12 to bias the

wedge 15 to its extended position.

Preferably, the wedge 15 will be held in position within the recess formed by

the wedging surface 12 by means of a resilient band or strap 20 which permits

sliding movement of the wedge 15. Alternatively, a frangible securing means

could be employed.

In use, the rock anchor 10 of the invention will be inserted into a drill hole 17,

Figure 4, and act as a high strength anchoring point for a cable 19, chain 20, shank or the like. The trailing end lib of the body member 11 will be provided

with a securing formation such as clevis shown at 13 to engage a corresponding

formation on the chain 20 or the cable 19. The cable 19 could for example be

swaged by means of a ferrule 18a to a tongue formation 18, Figure 4.

It will be understood by persons skilled in the art that as tension is applied to

the body member 11 to withdraw from the drill hole 17, the wedge 15 will slide

on the wedging surface 12 to its extended position, Figures 3, 4, to engage the

inner surface 17a of the drill hole 17, and to wedge the body member 11 within

such drill hole 17. The greater the tension applied to the body member 11, the

more secure the wedging action will tend to be. It has been found that because

of the relatively large contact surface of the wedging member 15 and body

member 11, a secure and high strength anchoring point will be provided. Other

advantages of the rock anchor 10 of the invention will be apparent to persons

skilled in the art.

Doubtless variations of the invention are possible without departing from the

spirit of this disclosure and the scope of the consistory clauses. For example,

in the arrangement described herein, a single wedging surface 12 and mating wedging member 15 are provided. If required, a plurality of such wedging

surfaces 12 and wedging members 15 could be provided. Also, the cross-

sectional profile of the body member 11 is not limited to a circular one, but

could be polygonal.

Claims

1. A rock anchor which is adapted to be inserted into a drill hole or the like

to be anchored therein, comprises an elongated body member which

defines a longitudinal wedging surface, such wedging surface tapering

outwardly in the direction of the leading end of the anchor, and a

wedging member which defines a sliding surface which co-operates

slidingly with the wedging surface, so that the wedging member is

movable along the wedging surface from a first retracted position

wherein it is disposed generally, co-extensively with, or within, the

lateral extent of the body member, and an extended position wherein it

extends laterally from the body member to engage the inner surface of

the drill hole and to wedge the body member within the drill hole; and

actuator means for moving the wedging member to its extended position

in use.

2. The rock anchor according to claim 1 wherein the actuator means is in

the nature of gripping means associated with the wedging member and

adapted to move the wedging member towards its extended position when the body member is moved in a direction withdrawing the body

member from the drill hole.

3. The rock anchor according to claim 1 or claim 2 wherein the wedging

member is in the form of an elongated wedge which tapers inwardly

towards its leading end to mate with the profile of the wedging surface

of the body member in a complementary fashion.

4. The rock anchor according to any one of claims 1 to 3 wherein the

actuator means is in the nature of gripping means associated with the

wedging member, and comprises a finger element which extends

laterally from the wedging member and which is adapted to engage the

inner surface of the drill hole in order to move the wedging member to

its extended position, when the body member is moved in a direction

withdrawing the body member from the drill hole.

5. The rock anchor according to claim 4 wherein the finger element is a

resilient element.

6. The rock anchor according to claim 5 wherein the finger element is

angled towards the trailing end of the body member.

7. The rock anchor according to any one of claims 4 to 6 wherein the finger

element projects from a cradle formation within which at least a portion

of the wedging member is received.

8. The rock anchor according to claim 7 wherein the cradle formation is

interposed between the wedging member and the wedging surface of the

body member.

9. The rock anchor according to any one of claims 1 to 8 wherein an

attachment formation is provided at or towards the trailing end of the

body member, the attachment formation being adapted to mate with a

corresponding formation for securing a chain, cable, shank or the like

to the body member.

10. The rock anchor according to claim 9 wherein the securing formation is

in the form of a device formation, tongue formation, socket formation

or spigot formation.

11. The rock anchor according to any one of claims 1 to 9 including a

flexible collar which surrounds the wedging member and body member

to hold the wedging member slidingly within the recess defined by the

wedging surface.