| 摘要 |
PROBLEM TO BE SOLVED: To provide a return mechanism of a shutoff valve capable of surely maintaining a valve element in an open position (returned position). SOLUTION: This mechanism comprises a return shaft 5 positioned within a gas flow passage 2d to impart a force in the direction to separate a valve element 4b from a valve seat 4a, a cylinder 6 surrounding and freely axially movably guiding the return shaft 5 and guiding the rear end of the return shaft 5 opposite the valve element to the atmosphere side, and a return rod 7 located on the atmosphere side for pressing the rear end of the return shaft 5 toward the valve element 4b so as to move the valve element 4b in the direction away from the valve seat 4a. A locking part 61a is provided at the position of the rear end of the cylinder 6 and a locked part 7a which, when the return shaft 5 is pushed in by a predetermined amount, locks to the locking part 61a to keep the return shaft 5 pushed in by the predetermined amount is provided at the position of the front end of the return rod 7.
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