GB2177476A

GB2177476A - Hydraulic support for mine roof linings

Info

Publication number: GB2177476A
Application number: GB8615991A
Authority: GB
Inventors: Zdzislaw Sender; Jeremi Maciejewski; Leonard Liduchowski; Ryszard Borowik
Original assignee: KATOWICKIE GWARECTWO WEGLOWE
Current assignee: KATOWICKIE GWARECTWO WEGLOWE
Priority date: 1985-07-01
Filing date: 1986-07-01
Publication date: 1987-01-21
Also published as: PL254324A1; GB8615991D0; DE3621506A1

Abstract

A hydraulic support for a mine roof, permitting a series of small collapses is equipped with two pistons 2 and 4 dividing each prop into two unequal parts. The lower part 5 is of approximately constant volume over a fixed period of use. It is filled with viscoelastic matter absorbing energy of impacts and vibrations. The upper part 6 of variable volume by virtue of a small-"bleed" exit is filled with a well known water/oil emulsion as a hydraulic fluid. Parts 5, 6 are separated by the floating piston 4. Thus, a sudden shock conveys pressure to the viscoelastic material, which deforms to prevent damage elsewhere in the equipment, and then regains its shape with consequent loss of liquid from space 6. <IMAGE>

Description

SPECIFICATION Hydraulic support for mine roof linings This invention relates to hydraulic supports for mine roof linings as used for protecting the working area particularly in the regions imperilled with danger of roof falls and collapse.

For protecting the working areas in working headings, metal linings with hydraulic supports are commonly used. There are many types of such supports, which differ only in minor technical details since the general principle of operation of all hydraulic supports is the same. The principle is that each support is equipped at the lower end with a prop filled with hydraulic fluid, usually water/oil emulsion, under high pressure and at the upper end with a piston supporting a roof bar of the lining.

Support of this kind is adequate when subject to static load. However, in the case of dynamic load as present during small collapse or settlement of the roof, the emulsion pressure rises considerably over a very short time. The prop, and the other elements of the lining, become damaged and the support ceases to act properly.

In order to avoid excessive inreases of emulsion pressure during such collapse, so-called high-release valves have been used. These are designed to let out some emulsion from the lower prop of the hydraulic support at the moment of collapse and therefore to prevent the emulsion pressure inside the prop from rising above the admissible limit. Several kinds of high-release valves, differing in constructional detail, are known, However, all such valves have a relatively large inertia. Each collapse releases in the ground a large amount of energy within a period of less than 0.1 seconds. In such a short time none of the known high-release valves is able to let out an appropriate amount of emulsion from the prop.

Excessive increase of pressure inside the prop and, consequently, damage of the constituents of the hydraulic support, can therefore still arise.

It has now been realised according to the present invention that a hydraulic support for a mine roof lining can usefully incorporate into its structure a support component capable of absorbing some energy release on minor roof collapse.

In one aspect the invention consists in a hydraulic support for a mine roof lining, of the type subject of sudden mining roof collapse, comprising a piston defining a hydraulic chamber separated from a chamber containing a viscoelastic substance by a partition movable at least in part, means being provided for loss of hydraulic fluid from the hydraulic chamber under pressure: whereby sudden pressure on the piston acts rapidly to deform the viscoelastic substance, and elastic regain of the said substance to essentially its original volume continues and completes the loss of fluid from the hydraulic chamber to the exent that the piston stabilises under the new pressure conditions.

More specifically, the invention provides a hydraulic support for a mine roof lining, particularly in the regions imperilled by sudden minor roof collapse, in which a hydraulic cylinder includes two piston members defining with the end of the cylinder two chambers, a larger upper chamber for hydraulic fluid, provided with a small exit for such fluid whereby the upepr chamber may slowly change its volume and pressure, and a smaller lower chamber containing an essentially fixed volume of a viscoelastic material which can absorbed the energy of sudden minor collapse by compression and thereafter regains its dimensions.

In a variant form of the above the lower piston is itself located for movement in a fixed partition, being spring biassed to a neutral position therein and with a maximum possible displacement therefrom corresponding to the maximum expected amplitude of roof collapse.

In another aspect the invention extends a mine roof lining comprising one or more of the supports defined above.

Such a lining allows large amounts of energy to be transferred from the ground to the lining within a very short time, corresponding to the collapse time. A mechanised lining equipped with supports of construction according to the invention can absorb without damage to its elements a collapse energy of very large valves, e.g. 1010 J, which would not be ensured by any of the known high-release valves.

The invention will be further described with reference to the accompanying drawings, in which; Figure 1 shows diagrammatically the lower prop of a hydraulic support with a floating piston, in axial vertical section, and Figure 2 shows a lower prop with a differential piston, also in axial vertical section.

Figure 1 shows a lower end of a hydraulic support for a mine roof lining. The prop 1 has a piston 1 with a piston rod 3 equipped with the head, not shown, adapted to cooperate with the roof bar of a mechanised lining or individual portion of such lining (also not shown). Towards the bottom of the prop 1 there is another piston 4. Pistons 2 and 4 divide the interior of the prop into two unequal parts, the lower part 5 of which, defined by the floating piston 4 is filled with viscoelastic matter, advantageously silico-organic, for absorbing the energy of impact and vibrations. The upper part 6 defines between the two pistons 2 and 4 has a variable volume, depending on the location of, i.e. the function performed by the lining at any particular moment. This part is filled with the well known water-oil emulsion as commonly used in mines to feed hydraulic elements of mechanised linings.

change of volume or this part 6 occurs during drawing off; displacing the lining to another location; and spragging it between the roof and the floor of the heading. It is achieved by adding or taking away hydraulic fluid.

A lower prop of a hydraulic support may alternatively have the different construction shown in Figure 2. In this the lower part 5 of the lower prop, is defined by a fixed partition 7 instead of the floating piston 4.

Differential piston 8 is mounted slidably in partition 7. Coil spring 9 is placed between the partition 7 and the piston 8, the tension of spring 9 compensating for differences of emulsion pressure acting on the upper and lower surfaces of this piston.

The stroke of piston 8 is such as to correspond to the maximum amplitude of roof deflection during a maximum energy collapse.

Floating piston 4 and differential piston 8 are both furnished with seals which prevent the wateroil emulsion contained in the upper part 6 of the lower prop 1 from mixing with the viscoelastic matter filling the lower part 5 of the lower prop.

In the course of collapse, within a very short time (about 0.1 seconds) a large amount of energy is transferred from the ground to the environment, that is to say to the lining of the headings located within the collapse area. This effect is accompanied by a corresponding deflection of the roof, corres-ponding to a maximum amplitude of collapse usually amounting to several millimetres.

According to the invention, the collapse energy is transferred from the roof bars through the piston rods 3 and pistons 2 to the water/oil emulsion contained in the upper parts 6 of the prop 1. This increase of emulsion pressure is transferred to the walls of the lower prop and to the floating piston 4. This in turn transfers it to the viscoelastic matter filling the lower part 5 of the prop 1. That matter absorbs the sudden release of energy, compensating in this way emulsion overpressure in the upper part 6 of the lower prop 1.

Practical experiments conducted on an experimental rig show that 1 kg of viscoelastic silico-organic matter can absorb collapse energy of the order of 105J, the pressure distribution having the shape of the parabola with its vertex situated on the straight line of external energy action. Some of the energy absorbed by the matter in question is transferred to the heading floor, while the rest is used to carry the supports after collapse.

Claims

1. A hydraulic support for a mine roof lining, of the type subject to sudden mining roof collapse, comprising a piston defining a hydraulic chamber separated from a chamber containing a viscoelastic substance by a partition movable at least in part, means being provided for loss of hydraulic fluid from the hydraulic chamber under pressure: whereby sudden pressure on the piston acts rapidly to deform the viscoelastic substance, and elastic regain of the said substance to essentially its original volume continues and completes the loss of fluid from the hydraulic chamber to the extent that the piston stabilises under the new pressure conditions.

2. A hydraulic support for a mine roof lining, particularly in the regions imperilled by sudden minor roof collapse, in which a hydraulic cylinder includes two piston members defining with the end of the cylinder two chambers, a larger upper chamber for hydraulic fluid, provided with a small exit for such fluid whereby the upper chamber may slowly change its volume and pressure; and a smaller lower chamber containing an essentially fixed volume of a viscoelastic material which can absorbed the energy of sudden minor collapse by compression and thereafter regains its dimensions.

3. A hydraulic support as claimed in claim 2 in which lower piston is itself located for movement in a fixed partition, being spring biassed to a neutral portion therein and with a maximum possible displacement therefrom corresponding to the maximum expected amplitude of roof collapse.

4. A hydraulic support as claimed in claim 1 and substantially as herein described with reference to, and as illustrated in the accompanying drawings.

5. A mine roof lining comprising one or more supports as claimed in any one preceding claim.