GB568927A - Improvements in and relating to hydraulic piston valves - Google Patents

Abstract

568,927. Valves. TOWLER, J. M., and TOWLER, F. H. June 30, 1943, No. 10577. [Class 135] A control valve of the piston type can be connected in series with a number of similar valves, the last in series being of the type such as in Specification 557,340, which unloads a pump when pressure liquid is not directed to an associated cylinder, the arrangement being such that the valves can be operated independently to control supply of liquid from the pump to one of a number of cylinders. As shown in the Figure, the valve member reciprocates in a cylinder bore surrounded by six annular chambers of which chamber 1 communicates with the next valve in the series, chamber 2 with the pump delivery via a passage 18, chamber 3 with exhaust, chambers 4 and. 6 with the hydraulic cylinder under control, chamber 5 through a passage fitted with a non-return valve 14 with the pump delivery, while the chambers at the two ends of the bore communicate with exhaust. The valve member has three lands A, B, C, with bevelled control edges. The land A has two series of radial ports 16 communicating with an axial passage 15. The valve member has five positions and when in either of the two end positions communication between the chambers 1, 2 is interrupted and pressure is supplied to one end of the hydraulic cylinder, while the other end is connected to exhaust. In the mid - position, communication is established between the chambers 1, 2 and the chambers, 4 and 6 are isolated from both pressure and exhaust. In two intermediate positions, communication is maintained between the chambers 1, 2 and one of the chambers 4 or 6 is connected to exhaust while pressure is maintained in the other chamber via the non- return valve. A spring-loading may be fitted, urging the valve to return to one of the intermediate positions when the operating handle is released after the valve has been moved to one of its extreme positions. A spring detent may be fitted to hold the valve in the intermediate positions. In a modification, four lands cooperate with ports in a cylindrical liner, exhaust from one end of the hydraulic liner being effected through an axial passage extending to one end of the valve member. Both forms may be modified to control a single-acting cylinder by omitting one of the lands and one of the annular chambers. In a modification permitting more than one valve being effective at the same time, the check valves 14 are isolated from the passage 18 leading to the chamber 2 and are connected to a manifold supplied to the pump.