Double valve with anti-tiedown feature

摘要

A double valve (10) is reset when a source of pressurized fluid is connected to a reset port. First and second reset pistons (38,64) are actuated in response to the pressurized fluid to reset first and second movable valve units (18,20) of the double valve (10), respectively. First and second pilot chambers (74,75;81,82) are vented when the first and second reset pistons are actuated, the first and second pilot chambers corresponding to first and second pilot valves (76,83) for actuating the first and second movable valve units, respectively. The venting prevents the first and second movable valve units from moving out of a deactuated position, respectively. The source of pressurized fluid is removed from the reset port. The first reset piston is retracted so that the second pilot chamber receives pressurized fluid while the first pilot chamber continues to be vented. The second reset piston is retracted after a predetermined delay time following retraction of the first reset piston, the predetermined delay time being sufficient to allow the second pilot chamber to become substantially pressurized. If the second pilot valve is actuated when the second reset piston is retracted, then the pressurized fluid in the second pilot chamber drives the second movable valve unit out of a deactuated position during a time that pressurized fluid in the first pilot chamber is insufficient to drive the first movable valve unit out of a deactuated position.