Patent GB-591292-A (GB)
Title: Improvements in or relating to hydraulic valves and to hydraulic power devices embodying such valves
IPC: F16K11/07
Filed: 1945-03-20
Abstract: 591,292. Fluid-pressure servomotorcontrol systems. WATSON, C. D. March 20, 1945, Nos. 7057 and 18174. [Class 135] A hydraulic power device comprises a motor member moved by the pressure liquid, a control valve housed in the device and actuated by variations in a pressure fluid to effect positional control of the motor member, and a compression spring located within the motor member around the axis thereof and co-operating with that member and the control valve so that the two will be held in balance by the forces acting on them, a variation in the pressure fluid acting on the control valve resulting in a consequential movement of the motor member until balance is regained. In an embodiment, pressure variations from a distant point are applied through a conduit 24, Fig. 3, to one side of a piston 31A carried by a piston-type pilot valve 25, the latter controlling the connection of pressure liquid and exhaust conduits 21, 22, respectively, to the left- and righthand sides of the pistons 12, 13 of power and slave units, respectively. The other sides of these two power pistons are interconnected by a conduit 16 so that the two power devices are in series. Pressure liquid applied to the left-hand side of piston 12 also flows through a bore 94 in the valve and is applied to the lefthand end of the valve stem. The actuating rod of piston 12 houses a spring 40 which abuts against the piston and also against a head 39 on an extension 29 of valve 25, and the movement of piston 12 resulting from a movement of valve 25 is transmitted back to the valve through the spring so that the valve will be re-centred. Both pistons 12, 13 are provided with relief valves 42 to blow off at the limiting positions of the pistons should the latter get out of synchronism. In a modification, piston 31A is situated at the opposite end of the valve rod and works in an extension of the block 20, the controlling liquid being led to the distant face of the piston through a longitudinal bore in the valve and its extension rod. In another modification, the extension 29 is of smaller diameter than the valve itself which thus constitutesa piston replacing the piston 31A. In a further modification, the piston 31A is spring loaded on both sides and the valve 25 is provided with a spring-loaded follow-up sleeve. Movement of valve 25 applies pressure liquid to move the follow-up sleeve and the latter controls the connection of the power devices to pressure and exhaust. Several power units may be combined in parallel to actuate the flaps 46, Fig. 6, of a folding wing aircraft. The pressure and exhaust lines 62, 63, respectively, are also led through a piston pressure-regulating valve 81 to a further line 64 in which is set up the control pressure actuating the valves 25 in the power-units. Actuation of the control lever 89 moves a casing housing springs 86 between which a piston 84 is suspended, the piston being connected to the valve 81. Movement of the latter valve connects line 64 to pressure or exhaust and thus varies the pressure in the line, this pressure being applied to a spring-pressed piston 75 connected to the seat 80 of the valve 81 so that the latter will be shut off when the pressure acting on piston 75 corresponds to the position given to lever 89.