| 摘要 |
A valve with proof of closure includes a valve body with a first port and a second port separated by a valve member that is biased toward a closed position. A piston is mounted within a pressure chamber with a pressure fluid port for connecting to a source of pressurized fluid. Piston is biased toward a retracted position and is moved to an extended position in response to pressurized fluid entering through pressurized fluid port. A control member is attached to valve member and is engaged by piston as it is moved a first distance from retracted position toward extended position. A valve position indicator with a closed state and as open state is biased toward the closed state and is actuated by piston as piston moves a second distance from retracted position toward extended position to move valve position indicator from closed state toward open state. |
