| 摘要 |
PURPOSE:To return a shut-off valve securely by utilizing the driving force of a gas meter which operates with gas pressure in the gas meter. CONSTITUTION:When gas leaks and an electromagnetic device 2 is powered on, the shut-off valve 22 is pressed against a shut-off valve seat 25 at a gas intake 2 and the gas is confined to maintain safety. When the valve 22 is returned, a pilot exciting coil 19 is powered on and the engagement of a clutch 12 is secured to cut off a current to the coil 19. This operation separates a pilot valve 17 from a pilot valve seat 26 to open a pilot gas passage 27. Therefore, the gas is supplied, bit by bit, and a changeover valve 7 performs changeover operation. Further, a pinion 11 also rotates to separate the valve 22 from the valve seat 25 through the clutch 12, a driving shaft 15, and a cam 18 for return, thereby opening the valve. The valve 22 attenuates attracting force beyond some press-contacting limit and the clutch 12 is released, so that the cam 18 returns to its original position. At the same time, the driving shaft 15 and valve 17 are pressed against the valve seat 26 and closed to finish the releasing operation.
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