Patent GB-891703-A (GB)
Title: Servo-mechanisms
IPC: B64C13/24
Filed: 1958-05-06
Abstract: 891,703. Fluid-pressure servomotor-control systems; valves. CONSOLIDATED CONTROLS CORPORATION. May 6, 1958 [May 20, 1957], No. 14470/58. Class 135. Actuation of a member, e.g. an aircraft control, is effected by a vane type power device 15, supplied with fluid through a pressureregulating valve 20 and a floating disc valve 21. Pressure regulating valve.-Within the upper part of a casing 11 is secured a sleeve 36 defining an inlet groove 34 and an outlet groove 72, each opening to the sleeve interior by ports 47, 48, respectively; slidable within the sleeve is a hollow piston closure 35 with a land 52 which co-operates with the inlet ports 47 to vary the area of communication between the latter and ports 48 via an annular groove on the closure 35, which groove is also connected to an exhaust port 70 via leakage passages 54, 55 in a plug 53 disposed in the closure bore, and slots 68 in a cap 66 attached to the right-hand end of the closure, the cap providing an abutment whereby the closure is urged leftwardly by a loading spring 62. The output pressure in groove 72 is supplied to the left-hand end of the closure 35 by leakage past the plug 53 whereby the pressure in outlet groove 72 is maintained constant by moving the closure 35 in opposition to the spring 62 to vary the degree of opening of the inlet ports 47. The inlet groove 34 is connected to the pressure side of the engine fuel-supply system through a filter; the port 70 is connected to the return side of the fuel system, and groove 72 leads to a duct 73. Power device.-The duct 73 opens into a bore 86 in a partition 80 in the lower part of the casing 11, the bore 86 being intersected by aligned but spaced nozzles 87, 88, the inner ends of which are formed as valve seats for co-operation with a floating disc 90 which normally occupies a position intermediate the seats so that each nozzle is supplied with pressure fluid from the duct 73. The lower part of the casing is divided into two chambers 13, 14 by a vane 15 and the nozzles 87, 88, respectively, open into these chambers. The vane 15 has an output shaft 16 which has ports that always connect the interior of the vane to the regulator valve part of the casing 11 adjacent the exhaust port 70 via passages 115, 116. Journalled within the shaft 16 is an input shaft 17 having a depending arm 18 that passes into the vane through a slot 117 in the shaft 16 and provided at its lower end with an adjustable cross-pin 24. The outer end of the vane 15 embodies ports 121, 122 that are normally closed by poppet valves 22, 23, each comprising a spring-loaded closure 126 with a pin 130 that slides in a guide 127 ; these closures may be replaced by ball valves, not shown. The spring rate of the arm 18 determined by its length and cross-section, is chosen to ensure snap-action by the valves 22, 23. The casing 11 is made up of a number of sections that are bolted together. Operation.-When the input and output shafts 17, 16 are in alignment the arm 18 is central in the vane 15, both valves 22, 23 are closed, the floating disc 90 connects both chambers 13, 14 to the pressure regulating valve 20 and the vane 15 is stationary. Upon the pilot rotating the shaft 17 either valve 22, 23 will be unseated by the pin 24 depending upon the direction of shaft rotation, thereby exhausting the corresponding chamber 13 or 14 through the associated port 121, 122, the vane interior, the ports in the output shaft 16, passages 115 116 and port 70. The disc 90 then moves due to the pressure differential thereacross to prevent further fluid supply to the low pressure chamber so that the pressure differential across the vane 15 causes it to move in the same direction as the input shaft carrying with it the output shaft. When rotation of the shaft 17 ceases the shaft 16 continues to move until the appropriate valve 22, 23 is out of engagement with the pin 24 so that the valve can close. The passages 54, 55 provide a leakage path between chambers 13, 14, so as to quickly equalize the pressures in these chambers when the valves 22, 23 are closed. Should the system pressure fail and rotation of shaft 17 does not cause motion of the vane 15, then a slight further rotation of the shaft takes up the clearance between the arm 18 and the slot 117 and the shaft 16 is directly driven by shaft 17.