GB1037289A - Improvements in and relating to hydraulic valves - Google Patents

Abstract

1,037,289. Valves. ARMSTRONG PATENTS CO. Ltd. Dec. 1, 1964 [Dec. 6, 1963], No. 48234/63. Heading F2V. [Also in Division G3] A manually actuated spool valve for selectively directing hydraulic fluid, e.g. for control in tractors, earth moving machinery and cranes, is retained in neutral position (Fig. 1) by centring spring 78 whereby pressure fluid entering port 16 passes to reservoir port 18 and, upon displacement of spool 20 to the right until a detent 58 engages a groove 25, a conical head 30 enters narrowed chamber portion 32 to restrict flow therethrough which is diverted to unseat closure 40, against spring 44, to supply a service line, e.g. to operate a ram, via port 14. A passage 74 connects through the valve body between port 16 and spring chamber 76 to equalize force upon the spool. When the service line is filled the consequent pressure rise displaces a relief valve 50 whereby a transverse port 64 thereof, communicating via spring chamber 51 and passage 68 with port 18 and passage 54 to equalize pressure on both sides of detent piston 56, is closed and transverse port 72 is opened to passage 60 whereby pressure fluid is applied to piston 56 to release the detent and the spool 20 is returned to the neutral position and continued displacement of valve 50 thereafter connects extension 17 of port 16 directly to passage 54. The consequent release of pressure build-up enables valve 40 to seat at 34 to retain pressure fluid in the service line which may gradually be released therefrom upon displacement of spool 20 to the left so that closure 46 is unseated by abutment of conical head 30 with spigot 48, provided with a gradually increasing taper. In the Fig. 2 embodiment position (not shown), the spool is engaged by detent 120 with pressurized fluid supplied from port 110 to service port 112 until relief valve 124 operates to permit flow via passage 128, constricted passage 130 and passage 144 to reservoir port 114 and to release detent 120 to permit the spool to be returned by springs 138 to a centralized neutral position whereby pressurized fluid is directed from ports 110 to 114, via ports 140, 144 connected by spool passage 142, whilst pressure is retained in service port 112 by the central portion 119 of the spool. Upon moving the spool to the right, fluid is released from the ports 112 to 114 and the pump continues to discharge via ports 140, 144.