Patent GB-982978-A (GB)
Title: Roof supports suitable for use in mines
Inventor: FARR PETER
IPC: E21D23/00
Filed: 1960-08-10
Abstract: 982,978. Hydraulic apparatus. DOWTY MINING EQUIPMENT Ltd. Nov. 6, 1961 [Aug. 10, 1960], No. 27726/60. Heading F1P. [Also in Division B8] Control apparatus for an hydraulic prop unit 13, Figs. 1,2 and 3 (Prov.) and an hydraulic jack 21 for connection between the prop unit and a mining machine, such as a conveyer 12, comprises a hydraulic circuit for connection to a source of power and including an hydraulically-actuated main control valve 20 to effect extension and contraction of the prop unit, an hydraulically-actuated main jack control valve 80 to effect power operation and to permit free movement of the jack, and selectivelyoperable pilot valves 41, 88 arranged to actuate the main prop control valve and the main jack control valve for only effecting a number of required combinations of operative conditions of the prop unit and jack, which member is less than the maximum possible number of combinations. The arrangement prevents the jack being contracted when the props are extended or being extended when the props are contracted. The prop unit 13 may consist of frames 16 joined by transverse members 18, each frame having a pair of props 14, 15 between a foot plate and a roof bar. Each unit is connected by a jack 21 to a flexible conveyer 12 associated with a coal cutter 11 which may be of the disc-shearer type. Supply and return pipes P. R run along the side of the conveyer and are connected by branches T, S to the main prop control valve 20 which, in turn, is connected by pipes P1, P2, to the props 14, 15 and the main jack control valve 80. The main prop control valve has ball valves 29, 37 selectively urged into engagement with seats 24, 27, 33, 34 by pistons 46, 47, 49 subject to the pressure in pipes P, R under the control of pilot valve 41 which is actuated by a solenoid 43 whereby the pipe P from the source of pressure is connected to pipe P1 or P2 to extend or contract the props, the other pipe P2 or P1 being connected to the return pipe R. Both pipes Pl and P2 are connected to valve housings 51, 52 each housing being associated with a pair of props 14, 15 and containing a non- return valve 58, 61 and a pressure relief valve 72 for each of its props. The non-return valves are opened when the main prop control valve is actuated to connect pipe P2 the pressure pipe P by the pressure acting on pistons 63 which first lift balls 61 from seats in the members 58 to initially permit slow contraction of the props and then lift the members 58 from their seats to permit rapid contraction of the props. The jack control valve 80 comprises two ball valves 97, 103 which are disposed between seats 95, 96, 101, 102 and controlled by pistons 93, 94, 99, 105, pistons 99, 105 being subjected to the pressures existing in pipes P1, P2 and pistons 93, 94 being connected to or disconnected from the pressures in pipes P1, P2 by the pilot valve 88 which is controlled by a solenoid 90. When the pipe P1 or P2 is connected to the pressure pipe P to extend or contract the props and the solenoid is not energized, both sides of the piston 109 of the jack 21 are connected to the return pipe R so that the piston is free to move. To advance the prop unit 13, pipe P2 is connected to the pressure pipe P by operation of the main prop control valve 20 to contract the props and when solenoid 90 is energized, the pipe P2 is connected to pipe 207 - to contract the jack 21 so as to move the prop unit towards the conveyer 12. The props can then be extended in their new position by de-energizing the solenoid 43 of the prop control valve to connect pressure pipe P to pipe P1. When it is desired to advance the conveyer towards the mine face, the solenoid 90 is energized to actuate the pilot valve 88 and disconnect pistons 93, 94 from the pressure in pipe P1 and the ball valves move to connect pipe 108 to the pipe P1 to extend the jack 21, pipe 107 being connected to the return pipe R. An embodiment having a single-acting jack 133, Fig. 7 (Prov.) between the prop unit and the conveyer for advancing the prop unit towards the conveyer, but not for advancing the conveyer, has a main control ball valve 129 which is between two seats 123, 128 and has actuating pistons 124, 127 and a pilot ball valve 139 operable by a solenoid 142 to connect or disconnect the pipe P2, which is connected to the pressure pipe P when the props are to be contracted, from the actuating piston 124. When pressure pipe P is connected to pipe P1 to extend the props, the pressure on the pistons 124, 127 maintains ball-valve 129 on seat 123 to prevent operation of the jack 133, even if the solenoid 142 is operated. When pressure pipe P is connected to pipe P2 and the props contracted, the pressure acts on the pistons 124, 127 to cause the ball valve 129 to engage seat 128 so that the jack is inoperative. Thereafter, energization of solenoid 142 disconnects pipe P2 from the piston 124 and the pressure acts to lift the ball valve from its seat 128 and the jack is contracted. In another embodiment for use on a plough face, a third pipe at a pressure lower that the main pressure source is connected to the main jack control valve and acts when the props are extended to maintain an extension force on the jack. In a further embodiment, the jack A, Fig. 1 (Comp.) is connected by a valve J operated by hydraulicallyactuated unit G, H to a pressure pipe P, each unit G, H also being connected to the pipe P by a solenoid-operated pilot valve E, F. The pipe P is also connected to hydraulicallyactuated units M.K. of a prop control valve 2 connected by pipes N, O to the prop C, pipe N being connected by a non-return valve Q to the lower end of the prop. With both solenoids S1 S2 of the pilot valves de-energized, the pipe P is connected to both units G, H and the valve J is urged to its central position wherein it connects both ends of the jack A to return R. Pipe P is, at the same time, connected by valve 2 to the lower end of the prop which is thus extended. When solenoid S1 is energized, the unit G is connected to return R and the valve J moved to the left to connect pipe P to the left-hand end of jack A which extends to advance the conveyer. When both solenoids are energized the valve J moves back to its central position to connect both ends of the jack to the return R1 at the same time unit K is connected to return R and pressure from pipe P acting on unit M moves the valve L to reverse the connections to the prop C, the pressure in pipe O acting on a unit U to open the non-return valve Q to permit contraction of the prop. With the prop contracted and solenoid S2 only energized, the unit H is connected to the return R and the valve J moves to connect the right hand end of the jack to the pipe P to contract the jack and move the prop unit towards the conveyer.