GB727624A - Improvements in or relating to fluid-metering shut-off valves - Google Patents

Abstract

727,624. Hydraulic machines; valves. BENDIX AVIATION CORPORATION. Feb. 27, 1953 [April 8, 1952], No. 5595/53. Classes 69 (2) and 135. A combined fluid-metering and shut-off valve which is particularly adapted for limiting the stroke of a hydraulic motor comprises a body 20 divided into two fluid chambers, each having a port connected thereto, and a piston and valve assembly 37, 38 slidably mounted in one of the chambers so as to divide it into two compartments 50, 51 which communicate with the other chamber 45 through a series of identical apertures 48, 49 in parallel relation, the ratio of the flow resistance of the apertures 48 communicating with the compartment 51 to the flow resistance of the aperture or apertures 49 communicating with the other compartment 50 being in the inverse ratio of the numbers of the two sets of apertures. Thus, when fluid enters the port 46 of the chamber 45, the piston 38 is gradually moved towards the other port 35 and valve 37 finally engages a valve seat 36 so as to cut off the port 35. As the apertures 48, 49 are all of the same size, they have the same flow characteristics. The ratio of the flow resistance to each compartment is therefore independent of changes in viscosity. The apertures 48 are formed in a cylindrical wall 25 forming an extension of a closure cap 21 secured to the body 20 by screws 22. The end of the compartment 50 is closed by a cap 26 urged against the end of the wall 25 by a leaf-spring 34 and guided on an adjustable screwed rod 27 which limits the movement of the piston 38 to the left. The piston 38 is pressed against the rod 27 by a light spring 40. The complete valve 14 is installed between pipes 16, 18 connecting one end of a hydraulic cylinder 13 to a four-way selector valve 12, which alternatively connects the ends of the cylinder to a pump 11 or to a tank 10. The valve 14 limits the movement of the-motor piston 13a from right to left but allows a full stroke of the piston in the opposite direction, the cap 26 then acting as a check valve to allow free movement of the piston 38.