GB698073A - Improvements in or relating to hydraulic controlling valves - Google Patents

Abstract

698,073. Hydraulic control systems. VICKERSARMSTRONGS, Ltd. Sept. 8, 1950 [June 3, 1949, No. 14915/49. Class 69(ii) A hydraulic control valve unit comprises a combined hydraulic pressure and mechanically operated valve 5 which controls the admission of pressure liquid to an operated ram and also the flow of liquid to exhaust at a mechanically predetermined portion of the ram stroke and a mechanically operated relief valve 19 which is operable to allow the pressure liquid acting on the valve 5 to pass to exhaust. Pressure liquid enters through a port 2 and depresses the valve 5 to uncover a port 7 through which the liquid passes into a chamber 8 and then through a port 9 and check valve 10 to an outlet chamber 11. The relief valve 19 is opened by a plunger 22 having a lost motion connection with a plunger 20 operated by a lever 21 which is moved by the ram at the end of its stroke. When the relief valve 19 is opened the pressure in chamber 8 escapes to exhaust through ports 14, 3 causing the valve 5 to be moved upwards by its spring 6 to place the outlet chamber, and hence the ram cylinder, in communication with the exhaust port 3 through passages 15, 13, 16, 14. The ram returns under its own weight, or by other means, and near the end of the return stroke a lever 24 is operated to depress the valve 5 and thus throttle the exhaust so as to bring the ram to rest without shock.