GB1342925A - Hydraulic power circuits employing remotely controlled directional control valves - Google Patents

Abstract

1342925 Hydraulic control circuits GENERAL SIGNAL CORP 14 May 1971 [14 May 1970] 14973/71 Heading F1P [Also in Division F2] A distributing valve 3 controlling the supply of fluid from a pump 6 via a line 8 to an hydraulic ram 1 is actuated by a remote pilot valve 15 which is provided with a sufficiently high control pressure by connecting it to the line 8 upstream of a throttle valve 29 via a combined throttle and relief valve 31. The pilot valve 15 has a spool 23 which in its neutral position shown connects both actuating means 11, 12 of its distributing valve 3 to drain 5 via ports 21, 22, notches 26, 27 in the spool 23 and chambers 18, 19, and, in this position, the spool 35 of throttle valve 29 is moved to the right to a low throttling position against spring 36 by pressure fluid entering chamber 38 via passage 41 and acting on the left end of the spool 35, to minimise neutral pressure losses. Movement of pilot valve spool 23 from the neutral position vents chamber 38 via line 42, ports 43 or 44 and chamber 18 or 19, the spool 35 moves to its high throttling position, and the increased pressure upstream of the valve 29 is fed via valve 31 to the pilot valve inlet 16 and via port 21 or 22 to actuating means 11 or 12. Back pressure in the line 8 is applied to a piston 45a via line 46, and before any ram movement is obtained is sufficient to move spool 35 to reduce energy losses in valve 29. Valve 31 comprises a throttling spool 51 movable against a spring 52 by the pressure of fluid admitted to chamber 47, and a relief valve 58 located within the spool 51 and openable when the fluid pressure exceeds a predetermined value. A second ram 2 is controlled independently of ram 1 by a distributing valve 4 and pilot valve 15a connected in tandem with valves 3 and 15.