GB813698A - Improvements in and relating to hydraulic control valves - Google Patents

Abstract

813,698. Fluid-pressure servomotor control systems. LEAR, Inc. March 8, 1956 [March 9, 1955], No. 7258/56. Class 135. The aluminium or magnesium casing 66<SP>1</SP> houses a pilot valve 10<SP>1</SP>, a relay valve 30<SP>1</SP> and a conically ended shaft 61<SP>1</SP> which is resiliently mounted in substantially frictionless bearings and together with the casing end cap 166 is provided with " O " rings to prevent leakage; the shaft 61<SP>1</SP> has arms 14<SP>1</SP>, 172, which are attached to the valve 10<SP>1</SP> and a rod 174 coupled to a mechanical or electrical force input source, such as a torque motor. One end of a flat coil spring 46<SP>1</SP>, which is connected to the arm 141 and disposed perpendicularly to the axis of the relay valve 30<SP>1</SP>, is attached to the latter by a rod 44<SP>1</SP>. Counter-clockwise movement imparted to the shaft 61<SP>1</SP> by the rod 174 causes leftward travel of the valve 10<SP>1</SP> and opens a port 100 to enable pressure fluid from an inlet 116 to traverse a duct 102 and act upon the outer end of relay valve land 38<SP>1</SP> and since the pressure fluid also acts upon the outer end of relay valve land 34<SP>1</SP>, which is half the area of land 38<SP>1</SP>, the valve 30<SP>1</SP> also moves to the left, which movement continues until the pilot valve returns to its initial position. Pressure fluid is directed from between relay valve lands 36<SP>1</SP>, 38<SP>1</SP> to a port 54<SP>1</SP> connected to one side of a mechanical member 56<SP>1</SP> whilst the other side thereof is connected via a port 52<SP>1</SP> and the space between relay valve lands 34<SP>1</SP>, 36<SP>1</SP> to an exhaust port 122 so that member 56<SP>1</SP> accelerates up to a constant speed corresponding to the degree of opening of ports 104, 106. Concomitantly the inner end of spring 46<SP>1</SP> is also moved leftwardly to exert a clockwise torque on the shaft 61<SP>1</SP> and when the moments on the latter are balanced, the pilot valve 10<SP>1</SP>, arms 14<SP>1</SP>, 172 and rod 174 are returned to their initial positions wherein the pilot valve enables a pressure of one half of the supply pressure to be exerted on the outer end of land 38<SP>1</SP>, which pressure produces a force balanced by that on the outer end of land 34<SP>1</SP>, and the relay valve is held stationary. A succeeding counter-clockwise force applied to shaft 61<SP>1</SP> will cause a repetition of the above operation and the relay valve will be moved further to the left. Clockwise rotation of the shaft 61<SP>1</SP> will result in member 56<SP>1</SP> decelerating to a constant speed dependent upon the degree of opening of ports 104, 106 until the relay valve has moved far enough to reverse the supply and pressure connections to the member 56<SP>1</SP>. The coil spring may be replaced by a torsion bar and the relay valve may have a differential area at both ends.