CA1202191A

CA1202191A - Mine support

Info

Publication number: CA1202191A
Application number: CA000441142A
Authority: CA
Inventors: Errol B. Dengler; Johan A. Conradie
Original assignee: H L and H Timber Products Ltd Pty
Current assignee: H L and H Timber Products Ltd Pty
Priority date: 1982-11-19
Filing date: 1983-11-15
Publication date: 1986-03-25
Also published as: DE3341743A1; GB2132248A; AU2140983A; GB8330460D0

Abstract

ABSTRACT OF THE DISCLOSURE

A mine support prop which consists of an elongate timber load supporting member which carries a plurality of circumferentially spaced grooves which extend over a portion of its length adjacent one of its ends with the grooves preferably being angled relatively to the prop axis.

Description

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2--FIELD OF THE INVENTION

This invention relates to mine supports of the timber prop type.

BACKGROUND OF THE INVENTION

An unprofiled timber pole has an extremely limited degree of compression in the direction of the grain of the timber. These props have limited use in deep level mines where the rate of closure of the hanging and footwall is rapid. Numerous expedients, mainly due to considerations of cost, have in the past been resorted to increase the degre~ of compressibility of timber props and so to prolong their useful lives. With one type of known~
support the prop is encircled by a ductile metal, glass fibre or like sleeve to increase its compression capability while remaining load supporting. In another type of more cost effective prop one or both ends of the prop are tapered. A major difficulty, however, with all known types of yieldable elongate timber prop is that one or both ends of the props burr radially outwardly as the prop is reduced in length under load and that more often than not one of the burring ends brushes predominantly to one side to cause the prop to skew and become ineffective as a load support.

OBJECT OE' THE INVENTION

It is an object of this invention to provide a prop type mine support adapted to minimize the skewing problem mentioned above.

SUMMARY OF THE INVENTION
An elongate timber mine support according to the invention .,. ~

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includes a plurality of grooves which lie in substantially the axial direction of the prop adjacent at least one of its ends.

Preferably the grooves are angled relatively to the axial direction of the prop.

In another form of the invention the grooves are each a portion of a helix.
Further according to the invention one end of each groove is deeper into the timber towards the axis of the prop than the other end.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described by way of example only with reference to the drawings in which :

Figure 1 is a side elevation of one end of a prop of the invention, Figure 2 is a plan view of the prop of Figure 1, Figure 3 is a similar view to that of Figure 1 of a second embodiment of the prop, Figure 4 is a plan view of the prop of Figure 3, Figure 5 is a plan view of a variation of the Figure 3 prop, Figure 6 is a side view of yet another prop end, Figure 7 is a plan view oE the prop of Figure 6, Figure 8 is a side elevation of a further prop embodiment, Figure 9 is a side elevatlon of a further embodiment of the prop, and Figure 10 is a perspective view of still another prop end.

DETAILED DESCRIPTION OF THE DRAWINGS

All of the props illustrated in the drawings are elongate timber poles 10 with the grain of the timber lying in the axial direction of the props. The timber is conveniently a hard timber such as saligna.

One or both ends of the prop 10 of Figures 1 and 2 carry grooves 12 which are cut into the timbèr in the axial direction of the prop. The bases of the grooves are deeper towards the prop axis towards their ends remote from the prop end.
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In the prop of Figures 3 and 4 the deeper ends of the grooves are at the free end of the prop. Figure 5 - illustrates a prop similar to that of Figures 3 and 4 but with the grooves 12 cut into the pole at an angle and not ràdially as with thé previous embodiments.

In a preferred form of the invention the grooves 12 are angled relatively to the prop axis as illustrated in Figures 5, 6 and 7. The grooves 12 in this embodiment of the prop could be cut into the prop at an angle as with the Figure 5 prop.

In all of the props which have thus far been described and illustrated the grooves 12 extend from a position below to the Eree end oE the prop. The ends of the grooves 12 could, however, terminate short of the free end of the b 3 ~iL

prop to provide an uncut headpiece for the prop. It is however, important that the ends of the ~rooves are not too remote from the end of the prop otherwise, if the grooved zone is not supported, the prop will-merely break in the grooved zone under load. Such a prop is illustrated in Figure ~ where a plurality of circumferentially spaced grooves 14 have been cut into the prop below its free end.
The grooves 14 could be cut with a flat bladed saw so that the qrooves are deeper at their centres than at their ends. To further deepen the grooves at their longitudinal centres they could be cut with a circular saw.

The prop of Figure 9 carries a plurality, conveniently four, grooves 16 which are cut at an angle into the sides of the prop and shaped as illustrated in the drawing.

. . . .
The Figure 10 prop carries four deeply fluted almost helical grooves 20 as illustrated in the drawing.

In use, the props of Figures 1 to 10 are wedged between a hanging and footwall in the conventional manner. As the hanging closes in time with the footwall the grooved and so weakened ends of the props crush and burr outwardly.
The inclined grooves of the Figures 5 to 10 props cause the prop ends to burr with a twisting efEect which promotes even radial spreading of the burred timber fibres. This even spread of the burred timber tends to prevent the props Erom skewing out of their installed position.
All of the props described above may and preferably do carry mild steel restraining bands adjacent or around their grooved ends to prevent premature splitting of the prop ends under load.
The invention is not limited to the precise details as herein described and the grooves 12 to 18 in any of the illustrated props could be of any suitable cross-sectional shape or depth to suit specific prop requirements. For example, a prop that is required to yield at a lesser load would have wider and/or deeper grooves than those of a prop which is to remain highly load supporting in stopes which close slowly. This control of the yieldability of a prop is made further variable by varying the angle of the grooves. The more the groove angle is inclined to the vertical the greater will be the load at which the prop will yield and the further the grooves are from the vertical, within reason, the lower will be the yield load and the greater the twisting tendency.

Claims

1. A mine support prop including an elongate timber load supporting member having a plurality of circumferentially spaced grooves which extend over a portion of the length of the timber member adjacent at least one of its ends.

2. A mine prop as claimed in claim 1 in which the grooves are parallel to the axis of the timber member.

3. A mine prop as claimed in claim 1 in which the grooves are angled relatively to the axis of the timber member.

4. A mine prop as claimed in claim 1 in which the grooves are helically arranged on the timber member.

5. A mine prop as claimed in claim 1 in which the grooves taper in depth from the end of the timber member towards its sides.

6. A mine prop as claimed in claim 1 in which the grooves taper inwardly in depth from the end of the timber member towards its axis.

7. A mine prop as claimed in claim 1 including reinforcing bands which surround the timber member adjacent its ends.