US3120105A

US3120105A - Self-advancing mine roof supports

Info

Publication number: US3120105A
Application number: US57462A
Authority: US
Inventors: Kibble John Dunbar; Bennett Albert Edward; Woodhead Peter Elliott
Original assignee: University of Surrey
Current assignee: University of Surrey
Priority date: 1959-09-25
Filing date: 1960-09-21
Publication date: 1964-02-04
Anticipated expiration: 1981-02-04

Description

Feb. 4, 1964 J. D. KIBBLE ETAL 3,120,105

SELF-ADVANCING MINE RooF SUPPORTS Filed Sept. 21, 1960 6 Sheets-Sheet l FiGJ.

MAY/AWAY Fela'. 4, 1964 J. D. KIBBLE ETAL SELF-ADVANCING MINE RooF SUPPORTS Filed Sept. 2l, 1960 6 Sheets-Sheet 2 Feb. 4, 1964 J. D. KIBBLE Erm.

sELF-ADvANcING MINE RooF SUPPORTS 6 Sheets-Sheet 3 Filed Sept. 21, 1960 Feb. 4, 1964 .1. D. KIBBLE ETAL SELF-ADVANCING MINE ROOF vSUPPORTS 'Filed sept. 21, 1960 6 Sheets-Sheet 4 Feb. 4, 1964 J. D. KIBBLE r-:rAL

sELF-ADvANcING MINE RooF SUPPORTS 6 Sheets-Sheet 5 Fle d Sept. 2l, 1960 Feb. 4, 1964 J. D. KIBBLE ETAL sELF-AnvANoING MINE RooF SUPPORTS Filed Sept. 2l. 1960 6 Sheets-Sheet 6 United States Patent O 7 Claims. (Ci. lil--en This invention relates to mine roof supports and is particularly although not exclusively, applicable to the supports in me system described and claimed in our copending application Serial Number 61,210.

According to the present invention a mine roof support is provided with means which is responsive to the force required to advance the support and w ich is arranged to control the lowering of the support 1n accordance with the magnitude of the force required. The means may be such that when the force required exceeds a predetermined value the support is lowered until the force required drops to said predetermined value or below it.

The support may be provided with duid-operated extensible legs by which the support can be raised and lowered, and the means may comprise a duid valve arranged to control the discharge of fluid from the legs. In this case, the valve may be resiliently biased into a closed position in which it prevents discharge or" fluid from the legs and ie arrangement may be such that the torce required to advance the support is applied to the valve in opposition to the force resiliently biasing the valve to its closed position.

In one arrangement, the support is provided with a duid-operated ram by which the support can be advanced and the means is responsive to fluid pressure applied to the ram for the purpose of advancing the support. ln such an arrangement, the arrangement may be such that the iluid pressure applied to the ram is also applied to a valve in opposition to a torce resiliently biasing the valve into its closed position in which the discharge of fluid from the legs is prevented. The valve may be a piston valve and, in this case, the arrangement may be such that the fluid pressure applied to the ram is also applied to one side of the piston of the valve and the force resiliently biasing the valve to its closed position is applied to the opposite side of the piston.

In an alternative arrangement, the support provide with a cable (which may constitute a hose by which fluid can be supplied from a pressure main to the support) by which the support can be advanced and the means, iu this case, may be such as to be responsive to the tension in the cable during advancing of the support. The tension applied to the cable for the purpose or advancing the support may be arranged to act in opposition to a force resiliently biasing the valve to its closed position in which discharge of fluid from the legs of the support is prevented. The cable may be connected to a winch, the operation of which applies tension to the cable ror advancing the support and the 'winch may be such that tension can be applied to the cable of each of more than one such support, for example, the winch may be such that tension can be applied selectively to any one of the cables of the supports. In the arrangement in Which a winch is such that tension can be applied to the hoses of more than one support, the winch may be provided with means by which the hoses can be selectively connected to a source of main lluid pressure.

Advantageously, manually operable means to lower the support are arranged in operation to override the means responsive to the force required to advance the support.

Two embodiments of the present invention will now "ice be described, in greater deteail, by way of example only, with reference to the accompanying drawings, of which:

FGURE l is a partly sectional diagrammatic view in a direction parallel to the coal face of one embodiment of the invention.

FGURE 2 is a partly sectional diagrammatic view at right angles to the coal race looking towards the unexcavated coal,

FIGURE 3 is a diagram of the hydraulic circuit,

FIGURE 4 is a partly sectional elevation of a roof support unit and a face conveyor of a second embodiment of the invention,

FIGURE 5 is a somewhat diagrammatic plan showing four roof support units and a conveyor,

FIGURE 6 is a diagrammatic cross-section of a valve,

FIGURE 7 is a cross-section of parts of a winch,

FiGURE 8 is a partly-sectional and diagrammatic elevation of the Winch, and

FIGURE 9 is a diagram illustrating a hydraulic circuit.

The unit shown in FIGURES l to 3 inclusive of the accompanying drawings consists of a base l upon which are mounted resiliently two single acting

hydraulic legs

2 and 3, upon which is resiliently mounted a roof bar 4. Within the base l a double-acting hydraulic ram 5, is mounted a gimbal bearing 6 which permits angular movement of the ram S. The piston rod 7, of the ram 5', is connected by means of a pin 3 and a bracket 9, to an armoured flexible face conveyor lll. The conveyor carries a spill plate ll upon which are mounted at intervals along its length brackets l2 which carry the

dexible pipes

17 and 18 passing along the length ot the face. These pipes l7 and l are connected to each support unit by branch exible pipes. A hydraulic valve block la, is mounted in a suitable position on the base. This is connected with the ram 5 and the legs Z and 3, by pires which are not shown. Similar support units are placed at short intervals throughout the length of the conveyor 1Q.

The roof bar in FIGURE l (or, in any alternative construction, any bars or canopies which contact the roof) is constructed so that a smooth, tlat and continuous surface is presented to the roof and at the front end, a short sloping portion i5 is provided as shown, to permit the bar to ride under any projection in the root and to prevent it from catching.

The hydraulic circuit required is shown in FlGURE 3, and is a diagram of the fluid pressure operated equipment of one support unit. In FIGURE 3 the legs of the support unit are shown at 2 and 3 and its horizontal ram at 5. The necessary Valves may be constructed in one block represented by the dotted line i6. The flexible pipe running along the face conveying hydraulic lluid from the pump is shown at 17 and that returning fluid to the tank at 18.

Fressure from the pipe i7 is applied to a port of a four-ported selector valve 2@ controlling the supply of uid to the ram 5. In the position in which the valve is shown, pump pressure is applied to the end 19 of the cylinder While the other end 2l is Connected to the return pipe 18. In this position the ram 5 tends to thrust the conveyor forward.

VJhen it is desired to advance the support unit, the valve Ztl is moved to a position in which the connections are reversed, the side 211 of the ram 5 being pressurized and the side 19 exhausted. The ram 5 will then tend to contract thereby tending to advance the support.

Initially, when the

legs

2 and 3 are still forcing the root bar l against the roof, the support will be prevented from moving and the pressure in the space 2l will rise considerably. This pressure in the space 21 is also applied to a volume Z2 on one side of the piston of a piston valve 23. Valve 23 constitutes a stop cock so constructed that in its normal position the port 2li communicating enemies position by a spring 26 the compression of which is ad justable by a screw 27'. The end of the valve 23, having therein the spring 26, is provided with a leak exit 23 to Y atmosphere so that pressure is not built up in this end of the valve 23.

The screw 27 is so adjusted that the initial rise of pressure in the space 2l and the space 22 causes the valve 23 to operate, so that the ports 25 and 24 are connected. This permits release of the hydraulicV pressure within the

legs

2 and 3 so that they lower under their own Weight. Forward motion of the whole unit will then occur, pressure in the

spaces

2 and 22 falling to a lower value determined by the sliding friction of the support unit over the face floor. Adjustment of the valve 23 by adjustment of the degree of compression of spring 26 by screw 27 is such that this lower pressure is iusufiicicnt to keep the valve 23 in the open position. Thus further lowering of the

legs

2 and 3 is prevented. Adjustment of the valve Z3 can, in fact, be such that the unit advances with the roof bar 4 in comparatively gentle contact with the roof. Y

The most likely causes of the unit encountering increased resistance to forward motion'are rises in the floor, accumulations of loose material on theriloor, and downward projections from the roof. bar 4 is caused to be forced against the roof again and greater force (Le. pressure in space 21) will be required to advance the support unit. Any such rise in pressure in the space 2l will, for as long as it persists, cause the valve 23 to op rate again, so that the

legs

2 and 3 descend further until, once again, there is sullicient clearance for the unit to slide over obstacles on the lloor or under those on the root and the required pressure in space 21 to advance the support unit drops to the lower value.

When the forward motion of the unit is complete, the valve 26 is placed in an intermediate position in which pressure is applied to neither side of the ram 5. The valve 22 will then be closed (by spring 26) and the

legs

2 and 3 may be re-set against the root by opening a stop coclt 29 which allows the supply of fluid to them from the pump through the pipe 17. The cock 29 is then closed and the valve 2o may be restored to its original position so that the conveyor is thrust forward.

A relief valve 3i? is provided to allow the escape of uid from the

legs

2 and 3 if strata convergence occursV when the

valves

23 and 2% are both shut, thus preventing the generation in the legs of an excessively high pressure.

Alternative operation of the valve 23 is possible by means of the hand-operated screw 31, when it is desired to lower the legs without pressurising the space 2l.

Automatic lowering of the

legs

2 and 3 may be prevented if desired by altering the setting of the screw 27 so that even the full pump pressure if applied to the pilot cylinder 22 does not cause the valve 23 to open.

Whilst the above described embodiment refers to a support unit having two

legs

2 and 3, it will be understood that the invention is applicable to support units with only one leg orto those with more than two.

lf it is desired to divide the legs of the unit into two or more hydraulically independent groups, this may be done by providing for each group a further set of valves equivalent to

valves

23, 29, Vand 3d in FIGURE 3. Alternatively, only one of any or each of these valves may be used with non-return valves in the pipes connecting each group of legs to thervalve. These non-return valves should be arranged so that the above described operation may occur but so that reverse ilow is prevented; thus, if pressure should be lost in one group of legs, the other groups are not affected.

Further, the valves are represented in the diagram as rotary and slide valves only for clarity, and each may in fact be of either type or be a puppet valve. In cerln each'case the roorV tain constructions it may be Vconvenient to combine

valves

23 and 29 into one valve, or to control the two ends of ram 5 from two separate valves replacing valve 20, the hydraulic operation remaining as described. lt is alternatively possible, if

valves

23 and 29 are combined, to arrange for the legs to rise automatically towards the roof again necessary so as to remain in close contact with it during forward movement of the support unit. However, if such an action were to occur, particularly if it wer to occur repeatedly, a friable roof might be brel-ren up by the motion ot the roof bar.V It is therefore preferred to control automatically the lowering of the legs only.

In another alternative arrangement the iluid supply to the valves and 29 is derived from two separate sources.

The means by which a pulling action on the part of the advancing ram is caused to release the support unit leg pressure may be purely mechanical, ratherV than hydraulic as has been described. ing d (FGURE l) of the ram 5 is omitted, andthe longitudinal force is taken by a link connected to the piston of the valve 23, the cylinder of the valve being lined to the support unit base. It is then arranged that the pull ot the ram 5 is taken by a spring equivalent to the spring 26, the valve 23 opening when the force reaches a value set by adjustment. Such a system may be used in conjunction with a circuit in which the lluid supplies to the cylinder and the legs are separate, that the legs being from a hand operated pump mounted on the support unit itself.

rthe invention is particularly suitable for systems in which the operating valves ot the support unit are themselves controlled remotely or automatically. The valves 2Q and 2% (FGURE 3) may thus be operated, not manually as shown, but by electric means or by pilot cylinders press rised by a special fluid pressure circuit, for example, as disclosed in our co-pending application Serial Number 61,210.

A further embodiment of the present invention will now be described in greater detail, by way of example only, with reference to FIGURES 4 to 9 inclusive of the accompanying drawings.

As shown in FIGURES 4 to 9 inclusive of the accompanying drawings, this roof support unit comprises two

legs

2 and 3 each mounted on a separate base 92 and 93 respectively, the bases S22 and 93 resting on the floor F and being of suicient size to prevent the

legs

2 and 3 from falling over. Each

leg

2 and 3 may bermounted rigidly on its base 92 or 93, or it may be. located in a resilient bush on the base. Each leg 2 and-3 also has a roof bar 9d and 95 respectivel, which can engage the roof R and is pivotally mounted on the piston portion of the respective leg. The front leg 2 has a roof bar 43 extending in cantilever fashion towards .or over a tace conveyor lil. The two roof bars 4- and 95 are interconnected (being attached by means of hinged joints 9o and 97) to a spring steel strap 98 spanning the roof between them. The two bases 32 and 93 are similarly interconnected by means of hinged joints S59 and lili) and a steel strap lill. A valve 2th? which controls the release or" the hydraulic fluid in the two

legs

2 and 3 is rigidly mounted on the base 92 of the front leg 2 and is connected to both legs 2 an 3 by means of ilexible hoses M2 of which the iirst few inches only are shown in FIGURE 4. f

FIGURE 5 shows diagrammatically a plan of a small part of a coal face equipped with such roof support units, four roof support units 104, lllS, lilo and lll? being indicated. One of four hoses 16S, M9, lll) and 111 only runs to each roof support unit, and this hose is Y used to supply iluid to the respective unit and also to In such a case the mount-` As shown in FIGURE 5, the roof support units are arranged in groups, each group comprising two pairs and the hoses from all tour units are connected to the winch 35. Each group of four roof support units is also equipped with one hydraulic single-acting ram which advances the face conveyor il?. The ram comprises a piston 37 attached to a bracket 38 on the conveyor lli, and a cylinder portion 39 which lies loosely on the ground etween the two adjacent front bases 92 of the units of one pair or" units. The cylinder portion 39 has a crosspiece 46 attached to it at right angles in such a way that it bears against whichever of the two front bases 92 is in front at any time. The piston portion 37 is hollow and is connected to a hose 112.

FlGURE 6 is a diagrammatic cross-section of the valve 243) of one roof support unit. The supply hose (not shown in FIGURE 6) is attached to a union 49 and there are two outlets for supplying the front and rear props respectively, of which only one, outlet 41, is shown in FIGURE 6. The main portion of the valve 260 is a combined release and yield valve comprising a cone 42 urged towards a seating 43 by a stack of disc springs 44 in a housing 45 with a plate 46. In order to Set the props against the roof iiuid under pressure is supplied through the respective hose and union 40 and enters the spring chamber 47 in the housing 45 by means of drillings 43 in the cone 42. From chamber 47 it passes through a channel 49 between the housing 4S and the cover plate de into a recess 50 in which is mounted a nonreturn valve 5l through which the iluid is able to pass in one direction to the outlet 4l to the props. A similar channel and non-return valve permits huid to pass from the chamber 47 to the outlet communicating with the other prop. It the feed hose is disconnected from the supply or pressure huid the non-return valve 5l prevents the huid in the prop trom leaking away. ln addition to the passage of fluid through the outlet 41 to the props, iiuid also passes through another non-return valve 52 which, similar to valve 51 permits passage of uid in one direction only, to the main valve cone 4Z. The function of the valve 52 (two of which are provided, one for each prop) is described below with reference to FlGURE 9. Ir roof convergence occurs and when the pressure reaches a high enough value, the duid compresses the disc springs 44 and escapes past the main valve cone 42 back into the hose.

When the hose is pulled so as to advance the roof support unit the torce is suliicient to compress the disc springs 44 and lift the release valve cone 42 from its seating 43. The valve cone 42 may also be lifted from its seating 43 by means of a manual operating handle 53 which acts upon a collar 54 screwed on to the union it? which is integral with the release valve cone 42. lt will thus be seen that the main cone valve 42 serves both as a yield valve in the event of roof convergence occurring and as a release valve for operation either by increased tension in the hose, or by the handle 53.

The winch 36 which advances all the roof support units of a group is shown in more detail in cross-section in FIGURE 7 and in a partially-sectioned elevation in FlGURE 8. lt is a quadruple winch, powered in this example by a hydraulic gear motor 66. In FIGURE 7 it may be seen how the hose 3.08 terminates in the drum 61 which is one of four

drums

6l, 62, 63 and 64, and how

channels

65, 66, 67 and 68 are provided for the fluid to reach the centre spindle 69 of the winch, rotary fluid seals (not shown) being provided on either side of each winch drum so that the fluid can pass into only one of the four

axial holes

65, 79, 71, 72 in the spindle 69 to which a drilling such as the channel 66 is provided on the centre-line of each one particular drum. The hydraulic gear motor 6i) drives a shaft 73 parallel to the drum spindle 69, on which shaft 73 are mounted eight eccentrics of which only one is shown at 74 in FIGURE 7. On each eccentric there is a pawl which engages with a toothed disc attached to one of the winch drums. Only one drum 6i and its pawls 76 and 77 and toothed discs 7d and 79 are shown in full in FIGURE 8. rlhere are two toothed discs attached to each winch drum, each operated by means of a pawl, and each pair or pawls is either forced out of engagement with the toothed discs or held in engagement with them by means ot a small hydraulic ram acting upon a universally-jointed cross-member between the pawls; FIGURE 7 shows one ram Si? and a cross-member 3l. The eccentrics driving the pawls are arranged to be 180 out or phase so that as the motor shaft 73 revolves the two pawls of one winch drum can alternately cause the winch drum to rotate. The shaft 73 will require several bearings to support it, but these are not shown for clarity. The bearings and the motor et) itself are mounted on a manifold block Si?. which also carries one rotary face valve S3 controlling the supply of tluid to each winch drum and its operating cyhnder and certain other hydraulic connections. The winch drum spindle 9 and the manifold block S2 are mounted on a further block S4 by which the whole winch is attached to the conveyor lil. This block S4 also acts as a hydraulic manifold, in that the face hydraulic mains enter it at one side and emerge at the other, the necessary connections to the winch itself being taken o by cross-drillings.

Part of the hydraulic circuit of the whole system is shown in `lillilld 9. The high pressure face main HP is connected by a duct 9% to each ot the four rotary face Valves S3 controlling one roof support unit and its associated winch drum. Only one such circuit is shown in FEGURE 9. With the valve 83 in the position in which it is shown the high pressure uid is dlowed to pass to the upper side of the ram Sil controlling the pawls (not shown in FIGURE 9) forcing them into engagement with the toothed discs on the winch drum and also, through a nonreturn valve 9i duid passes to the hydraulic motor, thus causing it to operate. At the same time the hose ltl itself through the drillings in the winch drum 51 and the valve 33 is connected .to the return main RMP Thus the hose lili? is hauled in, `advancing ethe roor support unit, and the fluid in the

legs

2 and 3 is allowed to escape through the hose ll to the return main RM so long as the force required to advance the unit is suliicient to lift the release valve cone 42 from its seating 43 in the valve 20?.

In order to reset a support unit the rotary face valve such as the valve 33 controlling it is moved to a position clockwise from that shown in FXGURE 9. Then the passage leading to the hydraulic motor tif@ and to 'the top side of the ram t? is connected to the return main RM while the passage connected to the lower side of the ram S@ is pressurised, forcing the pawls out of engagement with their toothed discs. The hose l leading to the roof support unit is also pressurised. Therefore the winch no longer pulls on the hose lt and the

legs

2 and 3 are reset against the roof.

With the valve 33 in an intermediate position all outputs from it are connected :to the return main RM except that leading to the lower side of the ram il which remains connected to high pressure, ensuring that the pawls are out of contact with their toothed discs. The purpose of the non-return valve 9l in the passage leading to lthe hydraulic motor di? is to ensure that when the hydraulic motor stl is driven through one ot' the other valves fluid cannot pass back to the rant Si? in order to engage the pawls of a drum whose vdve has not been operated.

The function of the four non-return valves 5l and 52 in the valve 260 on each support unit is to ensure that should pressure be lost in one of the

legs

2 and 3 while the unit is not connected to the pressure main HP, -as might be caused by the roof above that leg breaking up, pressure is `not then lost in the other leg also.

The ram 37, 39 which advances the conveyor lll is controlled by a tfth rotary face valve S5 and its hydraulic araches connections are shown in FIGURE 9. With the valve d in lthe position shown, the low pressure face main Ll is connected through the hose il?. to a drling in the centre of the piston rod 37 thus causing the ram 37, 39 to push. When the valve 85 is rotated 90 clockwise the ram 37, 39 is connected to the return main RM, thus stopping 'he pushing action as will be required before `advancing either of the support units associated with that ram.

One great advantage of this invention is that the traveling Way along the face is almost completely unobstructed by the bases or" roof support units or by ramsin contrast to conventional roof supports. The thin spring steel roof bars 94 and 95 occupy very little space; the principal remaining obstruction to travelling is the conveyor advancing ram 37, 39, but this being single-acting, can be of small diameter, and also only one ram is required for every four roof support units. It will also be noticed that all the roof support units of a group together with the conveyor-advancing ram may :all be controlled from the winch.YV Thus .the operator has to do less travelliny to do his Work. These two points are of particular advantage in thin seams.

A further advantage is that the amount by which the -roof support units may be advanced at each operation is no longer limited by the maximum convenient length of hydraulic rams. Advantage may be taken or this to allow the roof support units to be released and reset much less frequently than is necessary with existing designs. ln FIGURE v5, for example, the roof support unit 197 at the extreme right is supposed just to have been advanced from a rear position such las that in which the roof support unit V165 second yfrom Ithe left is shown, the latter being adjacent 'to the waste edge and ready to be advanced. Y The lef-hand roof support unit 16d or lite of each pair will not be advanced at this operation, but only'after a further web of coal has been removed. The frequency with which they have to be released and reset is one of `the principal disadvantages of present designs of powered roof support units, and in certain conditions it has a very adverse eiect upon the roof. Y

'It will also be noted that fewer loops of loose 'nose than is usual are required by the present system. There is, in fact, only one hose to each roof support unit, and that hose is under the control Vof the winch 36.

In an alternative embodiment of the invention the roof support units are hauled forward not by the hose but by a length of chain, wire rope or other form of cable connecting the release valve 253%' to the multiple winch 36. The hose is then run separately and takes no tensile force. It may in fact be connected directly to a hydraulic manifold without passing through the winch, thus avoiding the rotary seal required otherwise. In a further variation the roof support units are also hauled forward by means of a chain or a rope but no Xed hose at all is provided to each unit. Yielding or release of the props is allowed with discharge of uid on to the floor on the open circuit principle. Resetting of the roof oupport units is accomplished by one length of hose which may be attached to any selected roof support unit of a group by means of a quick-release hydraulic coupling.

It is to be further understood that the hydraulic motor Vshown is only one of the possible ways of powering the winch required to advance the support units. Other possibilities would be a compressed air or an electric motor drive, or Ya mechanical drive taking power from the armoured conveyor itself or from a special moving chain placed alongside it. m

We claim:

l. An `advancing mine roof support comprising: at leastV one vertical extensible and retractable support member of the type incorporating a cylinder and piston assembly to the vertical cylinder of which liuid under pressure can be admitted for` the purpose of extending the said support member into `a roof-engaging position, said vertical cylinder having connected thereto an outlet conduit capable oi serving as a passage forV the exhausting of liuid from said vertical cylinder for the purpose of retracting said support member; a control valve associated with said outlet conduit, said control Avalve comprising a valve housing defining valve inlet and valve outlet passages, a valve closure member movably located within `a chamber deiined by the housing, and spring means associated with the valve closure member and adapted to exert a resilient force in a direction such that the Said valve-closure member is normly maintained in a closed position in which tluid olw between the said valve inlet passage and the said valve outlet passage is prevented, said valve inlet passage having hydraulic connection with the said outlet conduit; advancing 'means connected to said support member and to an abutment spaced from the said support member, said .advancing means being further adapted to exert an advancing torce `whereby said support member is urged towards the said abutment; Valve actuating means interconnecting said advancing means and said control valve and adapted to transmit to the said valve closure member a valve actuating force proportionate to the said advancing force in opposition to the said resilient force whereby, when the said advancing force attains a predetermined value, the valve actuating force overcomes said resilient force to move said valve closure member into an open position in which fluid ow is established between the said valve inlet and outlet passages to exhaust said vertical cylinder.

2. An advancing mine roof support as claimed in claim l, wherein said advancing means comprises an extensible and contractable horizontal piston and cylinder assembly to the horizontal cylinder or" which iiuid under pressure can be supplied through an inlet conduit leading into said horizontal cylinder for the purpose of contracting the said horizontal piston and cylinder assembly whereby the said support member can be moved towlards said abutment, and the valve actuating means is in the form of a pressuretransmitting conduit interconnecting said inlet conduit and said chamber denedby Vsaid valve housing, whereby the pressure ofthe iluid supplied to the horizontal cylinder is also supplied to the said cli-amber to act on the said valve closure member so as to urge the latter againstsaid resilient force.

3. An advancing mine roof support as claimed in claim 2, wherein the said valve closure member is in the form of a valve piston presenting a tir-st face acted upon by the pressure of iiuid supplied to said chamber, and a second face acted upon by said resilient force in opposition to the said pressure of iluid.

4. An advancing mine roof support comprising: at least one vertical extensible and retractable support member of the type incorporating fa vertical cylinder and piston assembly to the vertical cylinder yof which fluid under pressure can be admitted for the purpose of extending the said support member into a roof-engaging position, said vertical cylinder having connectedV thereto an outlet conduit capable of serving as a passage for the exhausting of iluid from said vertical cylinder for the purpose of retractingsaid support member; a control valve associated with said outlet conduit, said control valve comprising a valve housing deining valve inlet and valve outlet passages, a valve-closure member located within a chamber defined by said valve housing, spring means associated Awith said valve closure member and adapted to exert a resilient force in a direction such that the said valve closure member is normally maintained in a closed position in which iiuid flow between said valve inlet passage and said valve outlet passage is prevented, said valve inlet passage having hydraulic connection with said outlet conduit; advancing means in the form of a cable adapted to interconnect said support member to an abutment spaced horizontally from said support member; tensioning means for applying tension to the said ca. le in a direction such that lthe said support member is urged towards said abutment; the

alzados valve closure member being connected to an end of the cable whereby the said tension acts on the said valve closure member in opposition to said resilient Jforce, the latter having a value such n at, when said tension attains a predetermined value, the said tension overcomes said resilient force -to move the said valve closure member into an open position in which fluid iiow is established between said valve inlet and outlet passages to exhaust said verticai cylinder.

5. An advancing mine roof support as claimed in claim 4, wherein the said cable is constituted by `a hose by which fluid under pressure can be admitted to the said vertical cylinder for the purpose of extending said support member into a roof-engaging position.

6. An advancing mine roof support las claimed in claim 4, wherein the tensioning means for applying tension to said cable, comprises a winch adapted to be attached to said abutment, said Winch comprising a rotatably mounted drum upon which said cable can be Wound, at least one peripherally toothed disc arranged co-aXial with land isel@ cured to said drum, reciprocally-mounted pawl means adapted to enge-.ge said toothed disc, and pawl-operating means adapted to reciprocate said pawl means and thereby rotate said drum.

7. An advancing mine roof support as claimed in claim 6, wherein said Winch comprises a plurality of rotatably mounted drums arranged co-axial, and a plurality of associated pawl means, each pav/l means having retracting means capable of retracting its associated pawl means out of engagement with the respective toothed disc, whereby tension can be applied selectively to the cable of more than one such support unit.

References Cited in the file of this patent UNiTED STATES PATENTS 2,859,022 Frye Nov. 4, 195s FOREIGN PATENTS 742,850 Great Britain lan. 4, i956

Claims

1. AN ADVANCING MINE ROOF SUPPORT COMPRISING: AT LEAST ONE VERTICAL EXTENSIBLE AND RETRACTABLE SUPPORT MEMBER OF THE TYPE INCORPORATING A CYLINDER AND PISTON ASSEMBLY TO THE VERTICAL CYLINDER OF WHICH FLUID UNDER PRESSURE CAN BE ADMITTED FOR THE PURPOSE OF EXTENDING THE SAID SUPPORT MEMBER INTO A ROOF-ENGAGING POSITION, SAID VERTICAL CYLINDER HAVING CONNECTED THERETO AN OUTLET CONDUIT CAPABLE OF SERVING AS A PASSAGE FOR THE EXHAUSTING OF FLUID FROM SAID VERTICAL CYLINDER FOR THE PURPOSE OF RETRACTING SAID SUPPORT MEMBER; A CONTROL VALVE ASSOCIATED WITH SAID OUTLET CONDUIT, SAID CONTROL VALVE COMPRISING A VALVE HOUSING DEFINING VALVE INLET AND VALVE OUTLET PASSAGES, A VALVE CLOSURE MEMBER MOVABLY LOCATED WITHIN A CHAMBER DEFINED BY THE HOUSING, AND SPRING MEANS ASSOCIATED WITH THE SAID VALVE CLOSURE MEMBER AND ADAPTED TO EXERT A RESILIENT FORCE IN A DIRECTION SUCH THAT THE SAID VALVE CLOSURE MEMBER IS NORMALLY MAINTAINED IN A CLOSED POSITION IN WHICH FLUID FLOW BETWEEN THE SAID VALVE INLET PASSAGE AND THE SAID VALVE OUTLET PASSAGE IS PREVENTED, SAID VALVE INLET PASSAGE HAVING HYDRAULIC CONNECTION WITH THE SAID OUTLET CONDUIT; ADVANCING MEANS CONNECTED TO SAID SUPPORT MEMBER AND TO AN ABUTMENT SPACED FROM THE SAID SUPPORT MEMBER, SAID ADVANCING MEANS BEING FURTHER ADAPTED TO EXERT AN ADVANCING FORCE WHEREBY SAID SUPPORT MEMBER IS URGED TOWARDS THE SAID ABUTMENT; VALVE ACTUATING MEANS INTERCONNECTING SAID ADVANCING MEANS AND SAID CONTROL VALVE AND ADAPTED TO TRANSMIT TO THE SAID VALVE CLOSURE MEMBER A VALVE ACTUATING FORCE PROPORTIONATE TO THE SAID ADVANCING FORCE IN OPPOSITION TO THE SAID RESILIENT FORCE WHEREBY, WHEN THE SAID ADVANCING FORCE ATTAINS A PREDETERMINED VALUE, THE VALVE ACTUATING CLOSURE MEMBER INTO AN OPEN POSITION IN WHICH FLUID FLOW IS ESTABLISHED BETWEEN THE SAID VALVE INLET AND OUTLET PASSAGES TO EXHAUST SAID VERTICAL CYLINDER.