| 摘要 |
A valve and actuator are disclosed with fluid flow through the valve controlled by a piston directly responsive to in line fluid pressure during both opening and closing movement. The actuator shifts a valve stem to open a poppet valve in the piston to admit in line pressure into a chamber to act on rearward surfaces of the piston to advance the piston into valve closing, seated contact with a valve seat. Initial closing movement of the piston is by the actuator with continued closing movement by in line fluid pressure. An additional valve on the stem controls communication of the chamber in which the piston is carried with an outlet to close the chamber for pressurization to effect forward seating of the piston. Valve opening movement of the actuator closes the piston mounted poppet valve and also vents the chamber to permit in line fluid pressure to shift the piston rearwardly to an open retracted position. A modified form of the valve and actuator includes a housing partially defining axially extending passageways communicating an inlet with an outlet and permitting installation of the valve and actuator in a system requiring an axial flow path.
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