GB974716A - Hydraulic control system - Google Patents

Abstract

974,716. Valves. GENERAL CONTROLS CO. Sept. 24, 1962, No. 36165/62. Heading F2V. [Also in Division F1] A tapered gate valve 10, Fig. 1, which coof the stem co-operates with a rotatable nut 19 operates with screwed-in seats 7, 8, has its and extends into a hollow sleeve 30 in a housing operating stem 11 guided by a resilient sleeve 20. The lower part of the sleeve 32 is splined 12 urged against a bonnet shoulder 16 by a to the nut 19 and formed with a crown cam 33, strap 15; the upper threaded part 17, Fig. 3, rotation of which raises and lowers the valve 815 A tapered gate valve 10, Fig. 1, which cooperates with screwed-in seats 7, 8, has its operating stem 11 guided by a resilient sleeve 12 urged against a bonnet shoulder 16 by a strap 15; the upper threaded part 17, Fig. 3, of the stem co-operates with a rotatable nut 19 and extends into a hollow sleeve 30 in a housing 20. The lower part of the sleeve 32 is splined to the nut 19 and formed with a crown cam 33, rotation of which raises and lowers the valve stem; the cam is supported on a ball race 48. The cam 33 is driven by a number of hydraulically-actuated pistons 39 equiangularly disposed around the cam axis, the supply and exhaust of liquid to and from the pistons passing through ports 31a in a bearing 31 for the sleeve 32, which ports are controlled by two sets of slots in the sleeve 32, each set leading from one of two grooves 50, 51 whereby the pistons are driven in a motor-like manner to open and close the valve. The actuating liquid is supplied by a pump 64 comprising large and small pistons 63, 67, Fig. 4, each with a spring-loaded plate-valve 71, 72, respectively, which pistons are driven through an eccentric pin 85 in a transverse slot 86, Fig. 3, the pin 85 being connected to the shaft 82 of an electric motor 81. A ball check valve and a spring-loaded ball-type pressure-relief valve are associated with the supply fire from the larger pump piston; when the relief valve is open the pistons 39 are only supplied with liquid from the smaller pump piston and the valve moves slowly on to its seat. A pilot valve 99 selectively connects the grooves 50, 51 to the pump output or a reservoir 61 in which the pump is disposed and thereby controls actuation of the gate valve; this pilot valve is adjustable whereby the speed of operation of the gate valve can be varied. The position of the pilot valve 99 is determined by energization of one of a pair of electromagnetically actuated valves 121, Fig. 1, the coils of which are so connected that only one valve can be energized at any one time. The coil circuits are controlled by two push buttons 126, 136, Fig. 17, and each include a limit switch 129 or 141, a pressure switch 130 or 142, a normally-closed switch 131 or 135 and a coil 133 or 137 which operates contacts 134 or 138 in a parallel circuit to the pump motor 81. A holding circuit is provided across the push buttons 126, 136. The pressure switches 130, 142, Fig. 13, are actuated by plungers 161, 164 controlled by conical surfaces on a piston 144 movable axially by liquid acting on opposed diaphragms 147, 152 connected across the grooves 50, 51, Fig. 3; the piston 144, Fig. 13, is maintained in the position shown by plungers 166, 170, the loading springs of which are differently biased to take account of the fact that one diaphragm is open to pump pressure and the other to the reservoir. Should the supply pressure attain a dangerous level the piston 144 is traversed to the left and switch 130, Fig. 17, is opened while switch 142 remains closed. The limit switches 129, 141 are actuated by adjustable screws 173, 174, Fig. 3, on a plate 176 rotatably mounted on sleeve 32 and driven from the latter through worm-gearing 180, 181, 184, 185 and a link 190 by which the transmission ratio can be adjusted.