SUPPORT PROP

Abstract

A support prop which includes a cylindrical aluminium liner which is externally reinforced with a shell made from a composite material, an aluminium plunger with a seal which engages with an inner surface of the liner, a filler valve through which a volume inside the liner, adjacent the seal, in use is pressurized with a fluid, and a pressure relief valve which in use allows fluid under pressure to escape from the volume as the plunger is forced into the liner.

Claims

1. A support prop, comprising: an elongate cylindrical body with a first end which is sealed; an opposing second end which is open; a bore and a wall which bounds the bore; and wherein the wall includes an inner metallic liner which faces the bore and an outer shell which is made from a composite material and which surrounds and reinforces the liner.

2. The prop of claim 1 wherein the liner is made from aluminium or an aluminium alloy, and the composite material comprises a reinforced plastics material.

3. The prop of claim 1 wherein the first end is sealed by a force transferring component and wherein the prop includes a one-way filler valve which is fixed to the body close to the first end and which is operable to allow a fluid under pressure to be introduced into the bore.

4. The prop of claim 3 which includes a tubular plunger which extends through the open second end into the bore, the plunger including a leading end with a piston and a seal, on the piston which is configured to engage in a sealing and sliding manner with an inner surface of the liner, the prop including a pressure relief valve which is configured to allow fluid under pressure in excess of a predetermined threshold pressure value to flow from an interior of the bore between the leading end of the plunger and the first end of the cylindrical body.

5. The prop of claim 4 wherein the pressure relief valve is mounted to the piston so that said fluid under pressure flows into an interior of the plunger.

6. A support prop, comprising: a cylindrical aluminium liner which is externally reinforced with a shell made from a composite material; an aluminium plunger with a seal which engages with an inner surface of the liner; a filler valve through which a volume inside the liner, adjacent the seal, in use, is pressurized with a fluid; and a pressure relief valve which in use allows fluid under pressure to escape from the volume as the plunger is forced into the liner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention is further described by way of example with reference to the accompanying drawings in which:

[0014] FIG. 1 is a side view in section of a support prop according to the

[0015] invention,

[0016] FIG. 2 shows, in cross section, on an enlarged scale a cylindrical body which is included in the support prop, and

[0017] FIG. 3 illustrates a construction of a leading end of a plunger which is used in the support prop.

DETAILED DESCRIPTION

[0018] FIG. 1 of the accompanying drawings illustrates a support prop 10, according to the invention, which includes an elongate cylindrical body 12 and an elongate plunger 14.

[0019] The body 12 has a lower first end 16 which is sealed and an opposing upper second end 18 which is open.

[0020] FIG. 2 is a cross sectional view on an enlarged scale of the body 12. The body has a wall 22 which encloses a bore 24. The wall 22 has an inner tubular liner 26 with a smooth inner surface 28 which faces the bore 24 and an outer shell 30 which encloses and reinforces the liner. The liner is preferably made from aluminium or an alloy which includes aluminium. The use of aluminium is beneficial for the material is light and rust-resistant and when manufactured (extruded) under controlled conditions has a smooth inner surface which does not require to be machined in order to be engaged in leakproof manner with a seal, as is explained hereinafter.

[0021] The shell 30 is made from a settable composite and reinforced material e.g. a plastics material formed from components which, when mixed, set. The settable material may be an appropriate resin, which is reinforced by means of glass fibres, carbon fibres, fibres or strands of plastics materials, chopped strands, metallic windings e.g. of thin steel wire or the like. The shell reinforces the liner 26 in a radial sense and increases the burst strength of the prop particularly at a lower portion 24A of the prop which is pressurised in use.

[0022] The first end 16 is sealed by means of a hemispherical component 36 which preferably is made from aluminium and which is capable of transmitting a compressive force when, in use, the support prop 10 is under an axially directed load. A one-way filler valve 40, fixed to the wall 22 adjacent the component 36, is configured to allow controlled flow of a pressurized fluid e.g. water from an external source (not shown) into the bore 24.

[0023] An aluminium scrubber ring 44 is fixed, e.g. by means of welding, a screw thread, thermal shrinkage or a press fit, to the open end 18 of the body thereby to define a reinforced mouth 46 into the bore.

[0024] The plunger 14 comprises an elongate tubular member 50 which is made from aluminium or an aluminium alloy, and which encloses an interior 52. A reinforcing aluminium hemispherical component 54, which is similar to the component 36, is fixed to an upper end 56 of the plunger.

[0025] The plunger 14 has a lower, leading end 60 which is positioned inside the bore. This end carries a steel piston 62 to which is fitted a pressure relief valve 64 made from stainless steel. A seal 66 of urethane or a similar resilient sealing material extends circumferentially around the piston.

[0026] The scrubber ring 44 bears tightly against an outer surface of the plunger 14 is designed to prevent an ingress of dirt and foreign material into the bore 24, but allows sliding movement of the plunger relative to the ring, and thus relative to the cylindrical body 12.

[0027] In use of the prop 10 the component 54 is brought into contact with a surface of a hanging wall 70 of an underground excavation, and the component 36 rests on a surface of an opposing foot wall 72. Fluid under pressure, e.g. water, is introduced through the filler valve 40 into that part of the bore, marked 24A, which is between the piston 62 and the component 36. The bore portion 24A forms a sealed volume, of variable size. As the bore portion 24A is pressurised it expands and the plunger 14 is forced in a longitudinal direction, outwardly from the bore 24 of the body 12, thereby to place the prop 10 under an axially directed compressive load.

[0028] If closure of the hanging wall and foot wall takes place then the pressure relief valve 64 allows fluid which is in the bore portion 24A and which is pressurised to above a threshold pressure value which is determined by the setting and nature of the valve, to escape from the bore portion 24A through the valve 64 into the interior 52 of the tubular member 50. This escape path is preferred, but it is possible to use a relief valve, with suitable safeguards, which directs pressurized fluid through a wall of the bore portion 24A directly to the surrounding environment.

[0029] The aluminium liner 26 is rust resistant, and has a smooth inner surface 28 which engages in a sealing manner with the seal 66 carried on the piston 62 at the leading end of the plunger 14. The use of an aluminium tube as a liner improves manufacturing time and reduces cost. If the liner is manufactured (extruded) under controlled conditions the need for machining and for the use of a mandrill in the manufacturing process is eliminated. The aluminium liner on its own does not necessarily possess the strength required in a prop of this kind, unless the thickness of the liner is substantial. However a liner of reduced wall thickness can be employed by reinforcing the liner with the shell.

[0030] The shell 30 increases the radial strength of the liner and is designed to withstand the burst pressure, inside the bore portion 24A, which arises in use of the support prop. The plunger 14 is engineered to withstand the axially directed compressive force for which the prop is rated and which arises upon closure of the hanging or foot wall. The prop 10 comprising the relatively lightweight plunger 14 and the shell reinforced liner 26 is easy to handle, and to install in an underground location.

[0031] While a particular embodiment of the present support prop has been described herein, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.