GB1303206A - - Google Patents

Abstract

1303206 Valves G L REXROTH GmbH 3 Aug 1971 [4 Aug 1970 19 Nov 1970] 36506/71 Heading F2V Control of flow between a pressure source P, a tank T and two work ports A, B is effected with the aid of a main spool valve 1 operable under the control of an actuator 2, the actuator offering a high level of control sensitivity at the beginning of its control range. The main spool valve 1 is selectively connectible, at its ends, to a pressure source P and to a tank source T of the actuator by appropriate positioning of the actuator spools 31. On tilting the manual actuator 41, a piston-like member 39 is moved inwardly into the body of actuator 2 and so, by way of conical compression spring 32, moves the actuator spool 31. Initially, the resistance to deformation of the spring is small and so a sensitive control exists between actuator 41 and spool 31. Thereafter, the resistance increases and so the control sensitivity decreases. As the spool 31 is being moved towards its service port 33 or 34, the port is placed in communication with the actuator pressure source P which thus creates a pressure within actuator chamber 50 which acts on the actuator spool in a direction opposing spring 32. In modifications (Figs. 3 and 4, not shown), the single conical compression spring may be replaced by two helical springs which are of different length and are disposed one within the other. Alternatively, one helical spring may be used in which case the spring is disposed about two relatively movable abutments, the latter engaging one another and so overriding the spring at a stage in the actuation corresponding to the end of the sensitive range on the conical compression spring.