Patent GB-528770-A (GB)
Title: Improvements in or relating to fluid pressure remote control systems
IPC: F15B11/12
Filed: 1939-05-11
Abstract: 528,770. Controlling aircraft. AUTOMOTIVE PRODUCTS CO., Ltd., and CLENCH, E. C. S. May 11, 1939, No. 14111. [Class 4] [Also in Group XXIX] A fluid-pressure remote control system which is especially appliable for controlling the pitch of screw propellers for aircraft is constructed of a cylinder 33, Fig. 1, in which is arranged a piston 32, adapted to act as the control member, and the position of the piston is controlled by a tubular slip member 56, a movable stop member 40, and a fixed stop member 35, the movements of the piston to four control positions being obtained by admitting an unrestricted supply of pressure fluid from a pump 24 and pipe lines 21, 22 under control of valves 27, 28, 29, 30 connected to the pump 24 and to a reservoir 26. The valve members may be operated by cams 96, Fig. 7, on a cam shaft 95 which can be set to open valves 91, 117, and two other valves not shown so as to connect the pipe lines 21, 22 to the pump 24, or the reservoir 26 in various ways, the valves having a connection 82 for the reservoir, 31 for the pump, and 109, 110, for the lines 21, 22. As shown in Fig. 1, the pump is connected by line 21 an aperture 62 in the right-hand end of cylinder 33 and at the other end by aperture 73 and line 22 to the reservoir. The fluid pressure acts to move the stop 40 to the left and also upon a sliding plunger 47, which is guided in an extension of the stop 40, and maintains the piston 32 in its extreme left-hand position by acting on a piston 48 integral with the piston 32. The piston head 48 engages a flange 51 on a sleeve 50 and moves the sleeve with it compressing a spring 54 which acts on a flange 55 of the sleeve 50. In the next position of the cam shaft 95 both apertures 62, 73 connect to the reservoir, and the spring 54 expands and moves sleeve 50 to the right into contact with a tubular stop member 56 fitted with packing members 58, 57 of which the member 58 engages its coacting surface with greater friction than the member 57. The position of the tubular stop member 56 can be controlled by a master cylinder unit 72 (not shown) which can force fluid through aperture 70 into the working space 69 between the fixed stop member 35 and the stop member 56, and so the aperture can vary the pitch by manipulation of the master cylinder unit. In the next position of the valves the apertures 73, 62 are both connected to the pump 24 and the piston head 48 moves to the right relatively to the sleeve 50 and is finally stopped by engagement with a tubular extension 46 of the movable stop 40. This stop is maintained in its extreme left-hand position by the fluid pressure acting on a piston 42 attached to the stop. This position can be adjusted by varying the position of a stop nut 44. In the final position of the valves the aperture 62 is connected to the reservoir and the aperture 73 to the pump and the stop 40 is moved to the right permitting the plunger 32 to move still further to the right. In a modification, Fig. 8, a simplified form of slave unit 20 is employed in which the plunger 32 is controlled by valves operated by push buttons 123, 124, 125, 126, and the pressure liquid is supplied from a hydraulic accumulator 121 charged from a reservoir 26 by a hand pump 122. The body of the unit 20 is formed with three cylindrical bores of different diameters in one of which the flange 136 of the sleeve 50 slides, in another a larger flange 138 of sleeve 50 glides until it engages a flange 145 which replaces the first stop 35, and in the third bore the movable stop 40 slides under control of a spring 143. By actuating the buttons 123, 124, 125, 126 in succession the plunger 32 is moved to positions corresponding to those described in the first modification. The buttons are inter-connected by chain 175 which prevents more than one from being pushed in at a time, and they operate rods formed with frusto conical parts acting as cams to engage balls 170 and to force ball valves 163- 166 off their seats. The plunger 32 is connected to the sleeve 50 by a friction device comprising balls and a conical surface, which tends to retain the rod 32 in a partly retracted position in the event of failure of the pressure fluid by preventing forward movement of the main piston 48 relatively to the sleeve member 50 except when the main piston is pushed by the plunger 47.