Patent ID: 7011289

Claim:
A sliding spool valve for controlling flow of a fluid transmitted between an inlet at a relatively high pressure and an outlet at a relatively low pressure, the spool valve comprising first and second opposed ends and first and second hydraulic actuators, each hydraulic actuator acting on one of the opposed ends of the sliding spool valve, wherein the spool valve is reciprocally displaced between open and closed positions by hydraulic action of the transmitted fluid selectively acting on the first and second hydraulic actuators, characterized in that each hydraulic actuator comprises a piston reciprocally slidable in a bore to pressurize a working fluid which acts on one of the opposed ends of the spool valve, a lock mechanism being provided for retaining the pistons of the hydraulic actuators in positions equating to the open and closed positions of the spool valve, wherein the lock mechanism for retaining the pistons is operated by any of an electronic, electro-magnetic or mechanical trigger.