GB585389A - Improvements relating to hydraulic control systems - Google Patents

Abstract

585,389. Fluid-pressure servomotor control systems. HYDRAULIC CONTROL - ENGINEERING CO. Aug. 16, 1943, No. 13294. Convention date, April 16. [Class 135] A hydraulic control system comprises a double-acting servomotor and a valve having an element controlling the flow of pressure liquid to either end of the servomotor, and the liquid coming from-the discharging end of the servomotor is applied to a double-acting motor to actuate a second element of the control valve to shut off the flow of pressure liquid to the servomotor and so provide follow-up for the first valve element. The system comprises a supply tank 5, Fig. 1, pump 7, and accmnulator 3 which supplies liquid through a control valve 1 to one side or the other of the piston of a servo-cylinder 9. The piston is connected to a chain 175 running over sprockets of which one is connected to an aileron 11 or other aircraft control surface or vehicle steering gear. The control valve comprises a casing with a rotary plug 15, Figs. 2 ... 4, to which a handle 33 is secured, and a rotary sleeve 17 carrying a vane 53 which can move between stops 59, 61 in an enlarged part, 27 of the casing.' The sleeve is held in the casing by a set-screw 31 which rides in a groove in the sleeve. If the handle 33 is moved in a clockwise direction, Figs. 3 and 4, pressure liquid flows through grooves 73, 77 and an inter-connecting passage, passages 81, 85, groove 87<1> in the sleeve, passage 95<1>, groove 89<1>, port 127, and conduit 155, to the right-hand chamber of the servocylinder and pushes the piston to the left to lower the surface 11. The liquid in the lefthand chamber of the servo-cylinder is forced out and flows through conduit 157, port 129, groove 89, passage 95, groove 87, passages 97, 99, 100, groove 117, passage 123 and into chamber 175 where it moves the vane and the sleeve in a clockwise direction until the lands 91, 93 on the sleeve cut off the supply of pressure liquid to the servo-cylinder. The vane in moving will force the liquid in chamber 177 out through passage 125, groove 117<1>, passages 115, 111, 139, groove 133, passage 137 and groove 135 back to the tank 5. Movement of handle 33 in an anti-clockwise direction reverses these operations and raises the surface 11. The plug 15 carries a loose disc with an indicating pointer 47 and the handle 33 carries a pin 41 engaging a slot in the disc to give a lost-motion connection which takes up the overlap of lands 91, 93 on passages 85, 97. If vane 53 gets out of synchronism with the handle and rotary plug 15, they can be brought back by moving the handle backwards and forwards to its limiting positions two or three times. During this operation, excess pressure which may develop in one of the chambers 175, 177 is relieved through a valve 107 back.to the supply tank. The servo-cylinder is provided with taps 181, 183 to permit the escape of air when the system is being filled with liquid.