US3530490A - Self-advancing mine and roof support systems - Google Patents

Description

Sept. 22, 1970 WARD ETAL 3,530,490

SELF-ADVANCING MINE AND ROOF SUPPORT SYSTEMS Filed Sept. 23, 1968 5 Sheets-Sheet 1 DERic A. sTAW Sept. 22, 1970 W RD ET AL 3,530,490

SELF-ADVANCING MINE AND ROOF SUPPORT SYSTEMS Filed Sept. 23, 1968 5 Sheets-Sheet 3 nam A STAIN mi Sept. 22, 1970 E. WARD ET AL 3,530,490

SELF-ADVANCING MINE AND ROOF SUPPORT SYSTEMS Filed Sept. 23, 1968 5 Sheets-Sheet 5 INVENTORS ERiC WARD DERIC A .STAiN BY United States Patent C US. Cl. 91-170 3 Claims ABSTRACT OF THE DISCLOSURE A hydraulic self-advancing mine roof support has hydraulic prop means and a hydraulic ram for advancing the support, said prop means and ram being in a hydraulic system which includes fluid-flow control valves for the release of pressure-fluid from the prop means and the supply of pressure-fluid to the advancing ram for advancing the support and means for delaying operation of the advancing means to advance the support for a predetermined time with respect to the release of hydraulic fiuid from the prop means to free the support from between floor and roof to enable it to be advanced.

This invention is for improvements in or relating to self-advancing mine roof support systems in which each support is of the kind (hereinafter referred to as the kind specified) having one or more pressure-fluid extensible props or legs by which it is secured between floor and roof and a pressure-fluid operated device for effecting its advancement towards the mineral face as mineral is removed therefrom. Often, but not always, this advancing device is a hydraulic ram which utilises the mineral face conveyor or an adjacent support as an anchorage or abutment for the advance of the support.

In the longwall method of working mineral-bearing strata and utilising a roof support system comprising supports as just described, the following sequence of operations takes place:

Stage 1.The coal winning machine removes a strip of coal or other mineral from the length of the face.

Stage 2.The face conveyor, which receives the mineral removed from the face, is advanced towards the newly exposed face.

Stage 3.Each roof support is lowered from its roofsupporting condition, advanced up to the conveyor and then reset to the roof. This phase is systematic, in the systems with which the present invention is concerned, insomuch as each support is advanced, following the passage of the mineral winning machine, only after the completion or near completion of the advancing and resetting cycle of an adjacent or neighbouring preceding support.

There are several known ways in which the lowering of the supports and their advance takes place.

For instance, there is what is known as the servo-lowering system in which an advancing ram or jack of the support is operable to advance the support only when the pressure in the roof-supporting props or legs reaches a predetermined figure. Should the roof-supporting structure meet an obstruction the advance is delayed until further lowering of the support has been effected and it can clear the obstruction.

The servo-lowering system just described has the disadvantage of the roof support dragging along the mine roof and in so doing there is a tendency for the props or legs of the support to be set in an attitude leaning away from the mineral face. This is detrimental to proper roof support since natural convergence of the roof moves the 3,530,490 Patented Sept. 22, 1970 props or legs in the same direction and there is set up an off-centre loading condition.

Another known method of support advance is to lower the prop or props of the support to a positive stop position and upon reaching this stop position pressure is built up to actuate the advancing ram or other advancing device. This method has the disadvantage of slowing up the advancement of the support since at each support there will be a delay until such support has been lowered to the predetermined height.

According to the present invention there is provided a mine roof support having a fluid-operated prop or props and a fluid-operated advancing means which is inoperable until a predetermined time lapse has taken place from the release of the fluid-pressure in said prop or props.

More specifically the present invention provides a mine roof support system comprising a series of supports of the kind specified and in which lowering and advance of the supports in turn is initiated by the completion or near completion of the advance and resetting of a preceding support in the support series, wherein means is provided for automatically delaying for a selectable period the start of advancement of the support with respect of the lowering thereof.

In other words, the means for delaying advance of the support until its height has been reduced by a predetermined amount is adjustable so that the delay may be varied to suit the prevailing conditions in the mine. For instance, a relatively long delay will be required where big roof steps are likely to be encountered and a short delay where the roof is relatively flat or only small roof steps are likely to be encountered.

One particular embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic representation of the support and its valve mechanisms,

FIG. 2 is a side elevation of the support, and

FIG. 3 is a rear elevation.

Referring to FIG. 1 of the drawings, 10 indicates a hydraulically extensible prop or leg which it may be assumed constitutes a part of a hydraulic self-advancing mine roof support of known form. Such a support is shown in FIGS. 2 and 3 and comprises, in addition to the props or legs 10, a base 10a and a roof-engaging structure 1012 supported on the props or legs 10'. A doubleacting hydraulic ram for advancing the support is indicated at 11 and is anchored to the support at 11a and has a clevis 11b for anchoring its piston to a face conveyor. The ram 11 has ports 13 and 12 which serve as pressurefluid supply and exhaust ports according to whether the ram is being extended to, for example, push over a mineral conveyor towards the mineral face or retracted so as to advance the support up to the conveyor in the well known way.

The prop 10 is provided with a port 14 for the introduction and discharge of pressure-fluid according to Whether the prop is being extended to roof-supporting condition or lowered for the advance of the support.

The hydraulic system in which the prop 10 and ram 11 are connected includes two pilot-operated valves 15 and 16 and a metering or control valve 17 which can be adjusted as to the rate at which it will allow fluid to pass through it.

The pilot-operated valve 15 has a piston 18, a valve seat 20 and a spring-biassed sealing member or valve proper 22.

Similarly, the pilot valve 16 has a piston 19, a valve seat 21 and a spring-biassed sealing member or valve proper 23.

The pilot pistons 18 and 19 are fed with pressure-fluid via the pressure- fluid lines 24 and 25 respectively, the

3 pilot valves 18 and 19 controlling the flow of pressurefluid through lines 26 and 27.

The pressure-fluid system of each support is connected to the pressure-fluid system of an adjacent or neighbouring preceding support by a pressure-fluid line 28.

Assuming that the support is set in the roof-supporting condition and the advancing device 11 has been fully extended, in other words, the system is at stage 2 referred to above.

A pressure-fluid signal is now transmitted, via the line 28. This signal may be transmitted from a preceding sup port which has just completed its own advancing sequence and been reset between floor and roof. This signal acts immediately on the pilot piston 18 which depresses the sealing member 22 from the seat 20 and allows pressurefluid to pass from the hydraulic prop 10, via the port 14 and the seat 20 into the fluid line 26 and thence to exhaust. Thus, the support is lowered off to free it from between floor and roof.

At the same time the pressure-fluid signal via the line 28 is metered through the valve 17 and via the line 25 to the pilot piston 19. This, after a period of time which depends on the setting of the valve 17 and the cubic capacity below the pilot piston, lifts the sealing member 23 from the seat 21 and allows pressure-fluid to flow from the line 27 through the port 12 to the retract side of the advancing ram 11. The advancing ram then operates to advance the support.

By adjustment of the metering valve 17 the operation of the advancing ram 11, to advance its support, can be delayed for a long or short time after fluid from the supporting member 10 has been released. This ensures that advance of the support will not commence until the member 10 has been lowered sufiiciently to clear any steps in the roof. At the same time the delay can be selected so that it is not unnecessarily long and therefore results in an objectionable slowing up of advancement of the supports as in the method previously referred to where advance of a support is delayed until its props or legs have been lowered to a positive stop position.

It will be appreciated that with the above-described arrangement the time delay depends on the time taken for fluid-pressure from the supply 28, 25, to lift the piston 19 sufliciently to open the valve proper 23. This in turn depends on the amount of opening of the valve 17.

The arrangement whereby a hydraulic signal and hydraulic supply is passed from one support to the next via the pipe lines 28 may, for example, be similar to that described in our British patent specification No. 1,038,262 and US. patent specification No. 3,320,001.

The valve 17 may be replaced by a constant flow device (e.g. an orifice of predetermined fixed size) in conjunction with a pilot valve 19 of predetermined cylinder volume and piston stroke.

The system may be introduced into any automatic or manual control system where a delay is advantageous.

We claim:

1. A self-advancing mine roof support comprising a base, hydraulically extensible prop means mounted on said base and having inlet and exhaust means for pressure fluid, a roof engaging structure mounted on said prop means for application thereby to a mine roof for the support thereof, hydraulic ram means connected to said support and having inlet and exhaust means for pressure fluid and operative, when connected to an anchorage, to advance the roof support, and a hydraulic pressure fluid system for said prop means and said hydraulic ram means, said system including a source of pressure fluid, a pilot operated fluid control valve connected to said exhaust means of the hydraulic prop means for controlling the exhaust of pressure fluid therefrom, means connecting said valve and said source of pressure fluid whereby pressure fluid is supplied to said valve for the opening thereof, a further pilot operated fluid control valve connected to the pressure fluid inlet means of the ram means, means connecting said further control valve and said source of pressure fluid whereby pressure fluid is supplied to said ram means under the control of said further valve, means connecting said further Valve and said source of pressure fluid whereby pressure fluid is supplied to said further valve for the opening thereof, and a restricting means in said means for connecting said further valve and said source of pressure fluid for restricting the flow of pressure fluid to said further valve and thereby delaying opening of said further valve with respect to the opening of the valve controlling the exhaust of pressure fluid from the prop means thereby to ensure release of the support from between room and floor of the mine working before it is advanced.

2. A self-advancing mine roof support as claimed in claim 1, wherein the restricting means is an adjustable fluid metering valve.

3. A self-advancing mine roof support as claimed in claim 1, wherein at least one of said pilot operated fluid control valves has a piston and is opened by the applica tion of said pressure fluid to said piston.

References Cited UNITED STATES PATENTS 2,585,297 2/ 1952 Beuscher. 3,198,083 8/1965 Farr et a1. 9l461 3,357,313 12/1967 Pawling 91-452 FOREIGN PATENTS 558,976 7/ 1957 Belgium.

PAUL MASLOUSKY, Primary Examiner Us. 01. X3.

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