GB715215A - Improvements in and relating to hydraulically operated servo mechanisms - Google Patents

Abstract

715,215. Fluid-pressure servomotor-control systems. BOULTON PAUL AIRCRAFT, Ltd. Jan. 12, 1953 [Jan. 11, 1952], No. 915/52. Class 135 In a variable delivery hydraulic pump which is controlled through a hydraulic follow-up relay, the relay is rendered inoperative and the delivery controlling member of the pump is locked in the no-delivery position should the master element of the relay bind to the slave element. In an embodiment applied to a system for actuating a control surface on an aircraft, movement of the pilot's control lever acts through a differential, a link 25, and a lever 26 to move the master element of a relay 15. The control surface is also connected to the differential so that the relay-which is similar to that described in Specification 693,504-is controlled by the error signal. The slave pistons 7, 8 of the relay vary the eccentricity of the reaction ring of a pump 1, the latter supplying fluid through lines 2 to a double-acting jack connected to the control surface. Fluid to operate the relay is supplied by a variable delivery pump 17, the reaction ring of which is loaded by a spring 19 acting against a piston 20 subject to the output pressure so that the latter is kept constant. Pump 17 may comprise a bank of pistons and cylinders in pump 1 or may be a separate pump. Lever 26 normally pivots about a point 42 on a lever 43 and a spring box 51 is connected at the pivoting point 42. Should the master and slave elements of relay 15 bind, lever 26 will pivot about its point of connection 41 with element 24, lever 43 will turn anti-clockwise about its pivot 44 and its other end will free the stem 29 of a valve 30. The latter will then be projected by its loading spring to a position in which a line 13 supplying pressure fluid to the relay 15 and to a cylinder 11 will be vented to sump 23. A bolt 10 which is normally held back by the pressure in cylinder 11 will then be projected by its loading spring into a recess 9 carried by the reaction ring of pump 1 to lock the latter in the nodelivery position. At the same time, a switch 52 actuated by the pressure fluid will operate a warning lamp 53. Specification 639,819, [Group XXVIII], also is referred to.