CA2012302A1

CA2012302A1 - Yielding mine prop

Info

Publication number: CA2012302A1
Application number: CA002012302A
Authority: CA
Inventors: Donovan Gericke; Anthony John Spencer Spearing
Original assignee: Individual
Current assignee: Dorbyl Ltd
Priority date: 1989-03-16
Filing date: 1990-03-15
Publication date: 1990-09-16
Also published as: AU5136890A; AU619959B2

Abstract

ABSTRACT

A mine prop has a plunger and cylinder made of tubular steel.
The cylinder has a flared mouth and a cone collet adapted to grip the plunger is shaped complementally to the flare. The ends of the plunger and cylinder are domed. The prop is set by jacks acting between the cone collet and a clamp detachably secured to the plunger.

Description

BACXGROUND TO THE INVENTION

THIS invention relates to a yieldable support of the kind which is suitable for use as a yielding mine prop.

A variety of yielding props are known. One class of prop which is used relies on hydraulics, but such a prop is too expensive to leave in place and is usually reclaimed and re-used. Yielding props or supports which remain in place are usually based on timber. Thus elongated supports comprising largely timber as the yielding element and timber packs are commonly used.

At present timber suitable for use in mine supports is in short supply and is costly and as a result of the recent drought, subsequent floods and increased demand from the pulp and paper industry, the supply position is not likely to improve very quickly.

Yieldable mine supports made of tubular metal have been proposed. Thus ~outh Africa patent no. 77/5348 discloses two tubes that can telescope together with the outer tube carrying cutting bits digging into the inner member. Force acting between the ends of the prop is resisted by the bits cutting away metal on the inner tube. In South African patent no. 87/2548 an annular tapered mandrel carried by one tube engages in the mouth of another tube of the same diameter. The mandrel is of hard metal and it is envisaged that the prop will be reclaimed.

It would be an advantage to have a yieldable prop made of tubular metal which is cost effective and can be left in place.

SUNMARY OF THE INVENTION

According to the invention an elongate support comprises an open ended steel cylinder, a plunger which can telescope into the open end of the cylinder, a flared mouth to the open end, and a truncated frustoconical formation tapering complementally to the flare of the mouth, carried by the plunger and adapted to be adjustably fixed on the plunger, so that forces tending to cause the plunger to telescope into the cylinder cause the formation to deform the unflared part of the cylinder thus permitting the support to yield in a controlled manner.

DESCRIPTION OF THE DRawINGg Figure 1 is a longitudinal section through a prop in a collapsed position for transportation, Figure 2 is a view showing the prop in an extended position, Figure 3 is a view showing how the prop can be set, Figure 4 is a fragmentary view of another prop, Figure 5 is a top view of Figure 4, Figure 6 is an exploded view of a modified cone, and igure 7 is a section through a further prop.

DE~CRIPTION OF EM~ODIMENTS

The prop in Figures 1 to 3 is composed of three main parts:
a cylinder 10 made of tubular steel, a plunger 11 also made of tubular steel and a split coned collet 13. The mouth 12 of the cylinder 10 is prebelled to form a flare complemental to the cone of the collet 13. This prebelling ensures rapid load build-up. The outer ends of the cylinder 10 and the plunger 11 are closed by domed members 14 to which are secured rubber bearing pads 15. The inner end of the plunger 11 is closed and carries a threaded rod 16 which can pass through a hole at the closed end of the cylinder 10 where it can be secured by means of a winged nut 17 to hold the prop in a collapsed position for transportation.

In use the prop is extended to a position like that shown in Figure 2 with the bearing pads 15 against the roof and hanging wall. Knocking the collet 13 down into the flare 12 secures the parts together. However, for a more positive setting of the prop the procedure illustrated in Figure 3 is used. Here a set of hydraulic jacks 20 are positioned on the collet 13 and arranged to act on a clamp 21 removably locked to the plunger 11. The jacks are connected to a portable hydraulic pump to cause them to extend and thus to set the prop in place at a predetermined load.

A prop thus installed is suitable for resisting slow convergence or rapid loading as during a seismic event and has constant yield characteristics.

The prop shown in Figures 4 and 5 has an outer and lowermost tubular section 10 into which can telescope an inner and narrower tubular section 11. The top of the section 10 is flared to accept a truncated bored cone 12. The cone 12 is split and the split is narrowed by means of a sunk bolt 13.
Tightening of the bolt 13 causes the cone 12 to be clamped on to the section 11.

In use when a large enough force is applied axially to the illustrated assembly, the cone 12 will move along the section 10 and flare it out progressively. If the top of the section 10 is prebelled the initial stiffness may be increased.

Figure 6 shows another method of securing a cone 12 on an inner section 11. In this case a locking collet 19 is knocked into a space between the bore 20 of the cone 12 and the inner section 11 to ensure that the cone 12 locks on to the inner section.

In Figure 8 the plunger 11 is surrounded by a frustoconical sleeve 13 shaped complementally to the flare 12 on the cylinder 10. ~ pin 22 in one of a series Gf holes through the plunger 11 acts on the sleeve 13 to force it down when the prop has to yield.

Claims

1.
An elongate support comprising an open ended steel cylinder, a plunger which can telescope into the open end of the cylinder, a flared mouth to the open end, and a truncated frustoconical formation tapering complementally to the flare of the mouth, carried by the plunger and adapted to be adjustably fixed on the plunger, so that forces tending to cause the plunger to telescope into the cylinder cause the formation to deform the unflared part of the cylinder thus permitting the support to yield in a controlled manner.

2.
The support claimed in claim 1 in which the plunger is tubular.

3.
The support claimed in claim 1 in which the formation is pinned to the plunger.

4.
The support claimed in claim 1 in which the formation is a solid, holed split cone adapted to be clamped to the plunger.

5.
The support claimed in claim 1 in which the formation is a solid holed cone adapted to lock on the plunger by means of a locking collet or collets.

6.
The support claimed in claim 1 in which the formation is a locking collet composed of tapered sections with serrations on the inside to grip the plunger.

7.
The support claimed in claim 1 in which the outer ends of the plunger and cylinder are domed.

8.
The support claimed in claim 7 in which the domed ends are rubber covered.

9.
A method of setting a prop as claimed in claim 1 in which a jacking force is applied between the formation and an element acting on the plunger and the formation is caused to grip the plunger during the exertion of a predetermined jacking force.