NZ334716A - Fluid actuator including a piston drivable in two directions - Google Patents

Abstract

A fluid actuator comprises a main fluid ram 10 including a piston 12 coupled to a piston rod 18, and a control valve 30 which includes a body member 44 moveable from a first position (Fig.2) in which a port 34 is coupled to a port 42 and port 38 is coupled to port 34 allowing fluid to be passed to port 14 and taken from port 16 of ram 10. Valve 30 causes the piston to be driven in a first and a second direction A and B. Driver means 52 are activated directly or indirectly in response to movement of the piston in one direction to cause operation of the valve 30 to drive the piston in the other direction. When fluid is fed to port 16 (and taken from port 14) piston 12 is driven to move in the direction of arrow A. When fluid is fed to port 14 (and taken from port 16) piston 12 is driven to move in the direction of arrow B. The actuator further comprises a mechanical latch (not shown) operable when latched to prevent operation of the actuator and when released permits operation of the actuator. Driver means 52 comprises a valve having a body member 68 moveable between first and second positions under the influence of a cam 26 (carried by piston rod 18) as it moves in response to movement in one direction of the piston rod. Cam 26 is arranged to carry member 68 to a first position in which fluid is passed via a flow control valve 66 to one side of a timer piston 48 in a sense to drive the timer piston to move a control valve body member 44 to a position to cause the piston to move in the other direction.