WO1995034743A1

WO1995034743A1 - Mine prop

Info

Publication number: WO1995034743A1
Application number: PCT/EP1995/002232
Authority: WO
Inventors: Joachim Peter Heinrich Struss; Ian Andrè McKENZIE
Original assignee: ContiTech Luftfedersysteme GmbH
Current assignee: ContiTech Luftfedersysteme GmbH
Priority date: 1994-06-13
Filing date: 1995-06-09
Publication date: 1995-12-21
Anticipated expiration: 1996-12-13
Also published as: AU2789895A

Abstract

A mine prop comprises an elongate substantially rigid support member (10) including a biassing device (11) adapted to extend the effective length of the support member when there is a divergence between a hanging wall (20) and foot wall (21) between which the prop extends. The biassing device (11) comprises a pneumatically biased expansion device. With such an arrangement controlled yielding of the prop (10) can also be achieved by providing a pressure relief valve (18) for releasing fluid from the expansion device at a predetermined pressure.

Description

Mi ne prop

This invention relates to a support such as a mine prop generally employed for supporting such as a hanging wall in underground mining operations.

A problem associated with conventional mine props is that these become dislodged when the hanging wall and foot wall between which the props are wedged move apart.

It is accordingly one of the objects of the present invention to provide a novel mine prop which will overcome or at least minimize the above problem encountered when the hanging wall and foot wall diverge. A further object of the invention is to provide controlled and effective operation of the prop when the hanging wall and foot wall converge.

According to the invention a support includes an elongate substantially rigid support member including a biassing device adapted to extend the effective length of the support member when there is a divergence between opposed faces, for instance, a hanging wall and foot wall between which the prop extends.

Further according to the invention the biassing device comprises a pneumatically biased expansion device. With such an arrangement controlled yielding of the support can also be achieved by providing a pressure relief valve for releasing fluid from the expansion device at a predetermined pressure.

In one arrangement in accordance with the invention the pneumatically biassed expansion device will be in the nature of a piston and cylinder arrangement, preferably provided with a reservoir of pressurised gas. Such reservoir will be adapted partially to compensate for pressure loss and consequently the biassing force of the device after elongation of the prop and subsequent compression thereof.

With the arrangement above the piston and cylinder arrangement can conveniently be sealed with respect to one another by means of an internal flexible bag which occupies the compression zone between the piston and cylinder.

Further according to this aspect of the invention the space between the piston and cylinder and the gas reservoir communicate with one another by way of a non-return valve which closes when pressure in the reservoir exceeds that in the piston and cylinder. In an alternative arrangement the operation of the non-return valve could be reversed for appropriate applications as explained in more detail hereunder.

In order more clearly to illustrate the invention an embodiment thereof is described hereunder purely by way of example with reference to the accompanying drawings wherein:

Figure 1 is a partially sectioned perspective view of a mine prop in accordance with the invention; and

Figure 2 is a partially sectioned elevation of a different embodiment of the mine prop in Figure 1.

Referring to the drawing a prop comprises a elongated support 10 which could for example be in the form of a steel pipe or timber pole which is characterised in a biassing device 11 at its one end, for example at the lower end of the prop 10. The device 11 is adapted to extend the effective length of the prop 10 when a hanging wall 20 and foot wall 21 between which the prop extends, diverge. Such extension will thus prevent the prop 10 from becoming dislodged. The invention moreover envisages that an effective support will be maintained for the hanging wall 20 when subsequent convergence of the walls occurs.

The extension device 11 will also in practice be used to tension the prop 10 in position between the hanging wall 20 and foot wall 21 with the desired axial force and thereafter yield in a controlled fashion while maintaining the desired force on the hanging wall 20.

In the arrangement illustrated in Figure 1 the extension device comprises a pneumatically biassed piston 12 and cylinder 13 arrangement which define a compression zone 14 between them. The piston 12 and cylinder 13 are sealed relative to one another by means of a flexible bag member 15 which is disposed in the cylinder 13 and is secured to the piston member 12 at 15a. Thus expansion of the bag 15 by means of compressed gas or any fluid under pressure will cause the piston 12 to move relative to the cylinder 13 to cause elongation of the extension device 11. Likewise venting of fluid from the bag 15 will cause contraction of the extension device 11.

It is a further feature of the invention that the flexible bag member 15 will communicate with a gas reservoir by means of non-return valve 17 which will close when the pressure therein exceeds that in the bag 15. Thus for example upon a sudden divergence of the hanging wall and foot wall 20, 21, the extension device 11 will expand rapidly causing a sudden pressure loss within the bag 15. This will cause the non-return valve 17 to close sealing the pressurised gas in the reservoir 16. Subsequently when pressure in the bag member 15 again increases upon convergence of the hanging wall and foot wall 20, 21, the non-return valve 17 will again ultimately open when it experiences equal pressures in the reservoir 16 and the bag member 15. This arrangement will enable the bag member 15 to be filled or partially filled with water of other incompressible liquid so that the pressurised gas in the reservoir 16 will provide the biassing force which will cause the extension device 11 to extend itself.

A further feature of the invention is the provision of a pressure relief valve 18 which communicates with the bag device 15 and which is adapted to vent fluid therefrom at a predetermined high pressure thus allowing for a controlled collapse of the bag 15 and contraction of the extension device 11.

Doubtless variations of the inventions in detail exist and it is intended that these should fall within the scope of this disclosure. Thus in an alternative arrangement the operation of the non-return valve 17 can be reversed or adjustable so that when pressure in the bag member 15 exceeds that in the reservoir 16, the valve 17 will close. With such an arrangement, during controlled yielding of the prop, the non-return valve 17 will be closed so that upon subsequent divergence of the hanging wall and foot wall 20, 21, pressurised gas from the reservoir 16 can flow into the bag member 15 to equalise pressure between these members and thus maintain a functional although slightly reduced pressure in the bag member. With such an arrangement therefore greater support will be provided for the hanging wall 20 once the extension device 11 has extended its length.

With the above arrangement the bag member 15 could be fully filled with an incompressible liquid, while the reservoir 16 is partially filled with liquid and partially with compressed gas so that upon expansion of the bag member 15, liquid will pass through the non-return valve 17 from the reservoir 16 under the influence of the compressed gas. Thus upon divergence of the hanging wall and footwall 20, 21, the prop 10 will extend itself while the bag member 15 will remain filled within compressible liquid. Thus upon convergence of the walls 20, 21, the bag member 15, being essentially incompressible, the prop 10 will in effect provide rigid support.

The arrangement in Figure 2 is similar to that in Figure 1 except that the position of the bag member 15 and that of the reservoir 16 has been inverted and the reservoir 16 divided into two chambers 16a and 16b by means of a piston member 22 which is axially movable within the reservoir 16. With this arrangement for example the chamber 16a can be filled with incompressible liquid and the chamber 16b with pressurised gas. With such an arrangement also therefore the prop 10 will operate as described above with liquid passing from the chamber 16a into the bag member 15 when the prop 10 is elongated. Upon convergence of the walls 20, 21, an incompressible bag member 15 will again provide rigid support.

It is intended that the invention will include its scope both the extension device disclosed herein for the described application, as well as a prop including one or more extension devices. The advantages of the arrangement of the invention will be apparent to persons skilled in the art. It will be appreciated that a robust and versatile prop which can meet requirements of both expansion and yielding is provided.

Clearly the use of the aforesaid prop is not confined to underground mining operations. It could equally be used as a lateral support intended stably to hold up the side walls of trenches and the like. It could also find use supporting building features to allow work to proceed safely in the region of the support.

It will be appreciated that many variations in detail are possible without departing from the scope and/or spirit of the invention as defined in the consistory statements.

Claims

1. A support including an elongate substantially rigid support member is characterised in a biassing device adapted to extend the effective length of the support member where there is a divergence between opposed faces such as a hanging wall and a foot wall between which the support extends.

2. The support according to claim 1 wherein the biassing device comprises a pneumatically biased expansion device.

3. The support according to claim 2 wherein the expansion device includes a pressure relief valve for releasing fluid from the expansion device at a predetermined pressure to permit controlled yielding of the support.

4. The support according to claim 2 wherein the pneumatically biassed expansion device is a piston and cylinder arrangement.

5. The support to any one of claims 2 to 4 including a reservoir for pressurised gas in communication with the expansion device.

The support according to claim 4 and claim 5 wherein the piston and cylinder are sealed with respect to one another by means of an internal flexible bag which occupies a zone for fluid between the piston and cylinder.

The support according to claim 5 wherein the pneumatically biassed expansion device and the gas reservoir are in communication with one another by means of a non-return valve which closes when pressure in the reservoir exceeds that in the piston and cylinder.

A support according to claim 5 wherein the pneumatically biassed expansion device and the gas reservoir are in communication with one another by means of a non-return valve which opens when pressure in the reservoir exceeds that in the piston and cylinder.

The support according to any one of claims 5, 7 or 8 wherein the reservoir includes movable internal separation means which divides the reservoir into two chambers, the volume of the chambers varying in accordance with the movement of the

10

separation means, and at least one of the chambers being in communication with the expansion device.

10. The support according to claim 9 wherein the separation means comprises a movable piston or a flexible diaphragm.

11. A method of installing a support as claimed in any of claims 1 to 10 comprising the steps of locating the support between surfaces which are to be propped at least partially filling the pneumatic expansion device with a liquid to cause the support to extend into engagement with the faces.

12. The method according to claim 11 wherein the support includes a reservoir in communication with the expansion device and the method includes the step of at least partially filling the reservoir with a pressurised gas.

13. The method according to claim 11 or claim 12 wherein the expansion device is filled with liquid and the reservoir is partially filled with liquid and partially filled with a pressurised gas so that upon expansion of the gas, liquid passes from the reservoir to the expansion device.

14. The method according to claim 13 wherein upon expansion of the expansion device, liquid passes from the reservoir to the expansion device through a non-return valve.