GB1204874A - Compressed fluid operated control valve actuators - Google Patents

Abstract

1,204,874. Fluid-pressure servomotor systems. IMPERIAL CHEMICAL INDUSTRIES Ltd. Sept.17, 1968 [Sept. 22, 1967], No.43186/67. Heading G3P. [Also in Divisions F1 and F2], Pistons 4, 5 Fig.1 of a compressed air operated actuator suitable for controlling the outlet valve of a water tank having a constant supply are connected together by a rod 6 passing through a gland 7 in a fixed partition 3 which divides the cylinder into two piston chambers, and supply and exhaust ports 8, 9 in the cylinder wall are located between the partition 3 and the pistons 4, 5 and are connected to ports 32, 33 Fig.3 of an adjacent double-acting pilot valve. The latter comprises spools 34, 35 on a rod 36 which is held in the position so as to close ports 32, 33 from exhaust and from a high-pressure supply port 31 by a spring 39 acting on one side of a diagram 37 and balanced by air-pressure on the other side. The air-pressure is controlled by a liquid level responsive member so that when the level falls below a desired value the air-pressure is increased and overcomes spring 39 to move rod 36 to the left thereby admitting air-pressure to piston 4 whilst venting piston 5 which results in leftword movement of actuator rod 6 and consequent reduction of flow through the tank valve. Conversely, when the fluid level rises above the desired value, the air-pressure on diaphram 37 fall below the pressure exerted by spring 39 which thus moves rod 36 to the right thereby connecting ports 31, 33 and moving the actuator rod to the right to increase flow through the outlet valve. In a modification the pistons of the actuator are of the diaphragm type.