GB711975A - Improvements in or relating to fluid operating systems - Google Patents

Abstract

711,975. Hydraulic machines; fluid actuated valves. SMITH'S JACKING SYSTEMS, Ltd. Sept. 16, 1952 [Sept. 24, 1951], No. 22279/51. Classes 69 (2) and 135 A hydraulic control apparatus comprises a main differential area piston jack, an auxiliary jack having inlet and output ports arranged to intercommunicate when the auxiliary jack is fully extended whereby the main jack is supplied with pressure fluid, and solenoid. actuated valves to control the operation. A pump 12 driven by an electric motor 13 controlled by a solenoid actuated switch 38 draws from a reservoir 10 and delivers pressure fluid by a line 15, having a normally open bye-pass valve 16 which is closed by the pressure, and a pipe 18 having a pressure relief valve 31, to a jack 33 which operates at a low pressure to lift a spring loaded catch 34. The pipe 18 also feeds a jack 19, the ram of which when it completes its outward stroke connects the pipe to a pipe 22, having a non-return valve 21, leading to one side of a main jack 23. A pipe 29 branches from the pipe 22 to a normally closed solenoid operated valve 26 the other end of which is connected to the opposite end of the jack 23 by pipes 28, 24, the latter being also connected to a second normally closed solenoid actuated valve 25, the other end of which is connected by a pipe 27 to the reservoir 10. The solenoids of valves 25 or 26 are connectible in series with the solenoid of the switch 38 by means of switches 44, 45 respectively. To open the jack 23, switch 45 is closed thereby starting the motor and opening the valve 26. Jack 33 opens followed by jack 19 which supplies fluid to both sides of a differential piston in the jack 23 which is opened and liquid is byepassed to the reservoir through valve 31 until switch 45 is opened. The valve 26 closes and jacks 19 and 33 return under spring pressure, the liquid discharging through the valve 16 which has now opened. To close the jack 23 the switch 44 is closed to start the motor, open the valve 25, open the jacks 33, 19 and supply fluid to one side of the piston of jack 23 while liquid from the other side discharges through the valve 25. The valve 16 comprises a body 90, Fig. 4, having ports 91, 92, 93 connected respectively to pipes 15, 18, 30. A piston 95 is raised by pressure entering the port 91 and carries a member 96 which closes the port 93. The piston is returned by springs 102 and is bored to permit flow to the port 92, the bore being fitted with a restriction 99. A restriction 101 controls the return flow from port 93. The apparatus is described as being suitable for use for actuating a vehicle hood. Specification 655,817 is referred to.