GB990046A - Improvements in or relating to hydraulic valves - Google Patents

Abstract

990,046. Valves. COAL INDUSTRY (PATENTS) Ltd. May 25, 1961 [May 27, 1960], No. 18862/60. Heading F2V. A valve comprises a slider for connecting a first port to either a second or third port, an inlet through which operating fluid can move the slider, return means for the slider, means for applying fluid pressure to hold the slider against the action of the return means even if the operating pressure is removed, and selectively operable means to over-ride the effect of the fluid pressure and allow the return means to actuate the slider. When a supply of pressure fluid, controlled for example by a solenoid valve, is admitted to a port 10 it displaces a cap 39 and a closure member 41 to the left so that pressure fluid from a second port 9 flows through a seat 31 to a port 8 connected through a restrictor to apparatus, such as a pit prop. The port 8 is connected by a conduit (not shown) to a port 6 so that the pressure fluid also acts on a piston 43 to hold the closure member in its leftward position against a spring 46 after the solenoid valve has closed. Admission of pressure fluid to a port 5 restores the closure member to its original position in which the apparatus is connected to an exhaust port 7. The valve may be manually actuated by a key-operated screw 47. If the area of the cap 39 is smaller than that of a seat 25 the port 6 may be dispensed with since the hydraulic pressures in the spaces connected to ports 8 and 9 hold the valve in the operated position.