GB1105655A - Improvements relating to hydraulic systems - Google Patents

Abstract

1,105,655. Advancing mine roof supports. FAIREY ENGINEERING Ltd. March 12, 1965 [March 13, 1964], No. 10783/64. Heading F1P. A hydraulic system, for operating a self advancing mine roof support having two legs or groups of legs connected by a horizontal hydraulic ram, comprises two sequence controllers, each arranged first to lower one of the legs or groups of legs, then to extend or contract the horizontal ram, then to raise the leg or group of legs. The two sequence controllers operate in succession, and a reversing device is provided so that in the first sequence the horizontal ram is extended, and in the second sequence it is contracted. Hence the order in which the controllers operate determines whether the support advances or retreats. As shown, the piston of the horizontal ram 16 is connected to one group 11, 12 of legs, and the cylinder to another group 13, 14. The legs 11, 12 are connected to a pressure supply 72 through a poppet valve 25, and may be lowered by opening individual valves 21, 22 connected to the fluid return pipe 75. The legs 13, 14 have similar connections to valves 31, 32, 35. These valves are operated by cams on piston rods of rams 41, 42, through tappets 47, and the rams are supplied with fluid through a restriction 71 and solenoid change-over valves 68, 69. These valves also supply fluid to opposite ends of a reversing valve 70, the position of which depends on which valve 68, 69 is operated first. The inoperative valve allows fluid to escape to the return pipe 75, but when the second valve is operated there is no change in the position of the reversing valve because the end pressures are the same. A friction device may be used to prevent any such movement. The reversing valve 70 supplies fluid to the horizontal ram 16 from 24 or 33 and returns it to valves 23 or 34. The valves 24, 34 are operated together by the sequence ram 41, and the valves 23, 33 by the ram 42. This joint operation is effected by common shafts 53, instead of individual shafts 52, each operated by a single tappet 47. Thus when the rams 41, 42 operate in sequence, fluid is supplied first to one side of the horizontal ram 16, then to the other. To move the support in one direction the valves 68 is operated, the valves 21, 22, 24 and 34 and 25 operate in sequence, and then microswitches 63 are operated to operate the valve 69, and hence the ram 42. The microswitches 62, 63 are biased by a fluid-pressure piston 67 to a position in which they can be contacted by the rams 41, 42. Hence, if there is a sufficient pressure reduction in the first half of the cycle, the second half is not initiated. The tappet shafts 52, 53 project through the casing of the system so that they may be rotated manually. The invention may also be applied to the control of machine tools.