GB634334A - Improvements in or relating to power assisted remote control systems - Google Patents

Abstract

634,334. Fluid-pressure servomotor-control systems. AUTOMOTIVE PRODUCTS CO., Ltd., and BRADBURY, F. J. July 30, 1947, No. 20682. [Class 135] A power assisted remote control system of the kind in which an operated member, e.g. an aircraft control surface connected at 16 to a movable cylinder 15 of a hydraulic motor device having a fixed piston 13, follows the movement of an operating member, e.g. a pilot's control connected to a link 23 itself connected through a floating lever 22 to a piston valve 18, so that actuation of the valve causes movement of the cylinder 15 which movement is transmitted by the floating lever back to the value to provide follow-up action, has annular liquid passages 35, 36 formed on the valve and provided with tapered portions to give a progressive increase in cross-section of the passages away from a cylindrical land 34 whereby the rate of flow of liquid to and from the motor device is limited so as to avoid " judder ". The angle of the tapered portions is such that the effective area upon which pressure liquid acts to operate the motor device bears a ratio to the change in the valve opening for a given axial movement thereof, this ratio being between 0.40 P.K. and 0.60 P.K. for a movement of the valve of 0.010 inch, where P represents the liquid pressure in p.s.i. and K the ratio of the relative displacement between the valve 18 and its housing to the relative displacement between the cylinder 15 and its piston 13 if the link 23 is held stationary. The system is supplied from a reservoir 28 feeding a pump 43 which delivers pressure liquid via a cut-out valve 44 to an accumulator 11 whence the liquid passes to a port 42 which is permanently in communication with the left-hand end of the cylinder 15. An exhaust port 41 is connected to the reservoir whilst a port 32, controlled by the valve, communicates with the right-hand end of the cylinder, a greater area being exposed to liquid pressure at this end of the cylinder than at the other end, so that movement of the cylinder is effected by admitting or exhausting pressure liquid to or from the right-hand end.