Patent GB-751031-A (GB)
Title: Improvements in or relating to a system for controlling a fluid actuated device
IPC: B60T11/32
Filed: 1954-03-10
Abstract: 751.031. Operating clutches. ROSS OPERATING VALVE CO. March 10, 1954 [March 17 1953; June 18, 1953], No. 6961/54. Class 80(2) [Also in Group XXIX] In a system in which a fluid-pressure motor 12. Fig. 1, is controlled by duplicated main and pilot valves 13, 19 and 13<SP>1</SP>, 19<SP>1</SP>, sensing connections 25, 25<SP>1</SP> are made from parallel conduits 16. 16<SP>1</SP> feeding the motor to opposed pressure responsive elements in a safety valve 21 whereby failure of one of the main or pilot valves, resulting in differing pressures in the conduits 16, 16<SP>1</SP>, causes the safety valve to cut off the pressure fluid supply conduit 11 from a conduit 23 which feeds the pilot valves thereby preventing further operation of the main valves despite continued cyclic operation of the pilot valve, by, e.g. a solenoid. In a modification, the safety valve controls the supply to the main valves or to both the pilot and main valves. The safety valve may also have an outlet 27 for exhausting the conduit leading to the pilot and/or main valves when the supuly is cut off. Alternatively. the safety valve could be arranged to exhaust the supply conduit leading to the pilot and/or main valves instead of cutting it off. The invention may also be applied to a double-acting motor controlled by two pairs of pilot and main valves with a safety valve for each pair or a single safety valve for both pairs. Each main valve comprises an inlet chamber 47, Fig. 3, an exhaust chamber 53, a chamber 49 communicating with the motor, and closure members 58, 59 actuated by a piston 55 having a connection 86 with the pilot valve which consists of a spring- urged ball 79 normally closing a port 89 to isolate the connection 86 from the supply 77. A plunger 81 with a vent passage 91 is operated by a solenoid 68 to raise the ball from its seat. Instead of the three-way main valve shown, two-way or four-way valves may be employed. The sensing connection to the safety valve comprises passages 64, 65, 67. Alternatively, the sensing connection may open to a point adjacent the inlet valve member 59 either in the inlet chamber or in the chamber 49, it may open into the exhaust chamber near the exhaust valve member 58, or it may communicate with the pilot valve. In one form the safety valve has inlet and outlet ports 22, 23, Fig. 5, which are interconnected when a spring-centred plunger 97 is in its normal position but which are cut off from one another by a land 103 or 103' when the plunger is moved in either direction by differing sensing pressures admitted by ports 96, 96'. A spring-pressed detent 105 locks the plunger in its operated position and requires to be manually withdrawn. An additional port may be controlled by the plunger to connect the port 23 to exhaust. An alternative form of safety valve has closure members 126, 126<SP>1</SP>, Fig. 6, carried by diaphragms 111, 111' which are rigidly interconnected by an element 117 and loaded by springs 127, 127'. The controlled passage 123, 121, 124 is closed when either closure member engages its seat 125, or 125' in response to differing sensing pressures in chambers 112, 112'. Manually releasable detents 128. 128' lock the movable assembly in either of its closed positions.