GB909768A - Improvements in or relating to hydraulic regulating device - Google Patents

Abstract

909,768. Hydraulic apparatus; valves. SCHWEIZERISCHE INDUSTRIE-GESSELSCHAFT. Jan. 16, 1961 [Jan. 18, 1960], No. 1666/61. Classes 69 (2) and 135. [Also in Group XXX] An hydraulic regulating device for the synchronism of at least two differently-loaded actuators, such as the cylinders of an automobile lifting platform, comprises a valve bush 2, Fig. 1, connected to a pressure fluid source E and having a number of throttle openings 20a, 20b corresponding to the number of actuators, each throttle opening serving to direct a quantity of the incoming pressure fluid to its associated actuator A, a control piston 4 displaceable to control the throttle opening so that all are exposed to equal extents at each position of the piston, and an adjustable differential pressure valve 13 between each throttle opening and each actuator for maintaining the same pressure head for the fluid quantities directed through the openings. The control piston 4 has a throttle bore 12 and is movable by the pressure from the inlet E against a spring 5, an adjustable abutment 6 limiting the movement of the piston. The throttles 20a, 20b are of triangular cross. section and lead to chambers 18 between the lands of the valves 13, which chambers communicate by passages 19 with chambers 16 housing adjustable springs 14 which urge the valves against the pressure in chambers 17 connected by passages 21 to the pressure at the inlet E. In operation, the fluid pressure from the inlet E initially passes through the bore 12 to fill the space 22 and at a predetermined pressure open a master control valve 7 to permit movement of the piston 4 which opens the throttles 20a, 20b by equal amounts. The throttles cause a pressure drop in the chambers 16 which, with the pressure from the springs 14, opposes the pressure in the chambers 17 so that the control edges 13a of the valves open outlets 23 leading to the actuators, the arrangement maintaining equal the pressure head and flow to the actuators. In an alternative embodiment, the control piston 31, Fig. 2, is movable by operation of a lever 32 to control the flow of pressure fluid from a pump P to raise or lower the actuators V1, V2, the movement of the lever also. operating reversing valves 35a, 35b, located between the differential pressure valves 34a, 34b and the control bush 30 which is formed with throttle openings 38a of square form controlled by edges 31a, 31b on the control piston. The operation of the reversing valves ensures that during both raising and lowering of the actuators, the pressure differential valves are effective to control the pressure and rate of flow through the throttle openings 38a so that the movements of the actuators are always synchronized.