| 摘要 |
PROBLEM TO BE SOLVED: To prevent a valve element from being damaged by a valve seat member, and prevent accidents of leakage of gas in large quantities from occurring even if the valve seat member is destroyed by fire. SOLUTION: A pair of valve seat members 3A, 3B and a spherical valve element 4 are housed in a valve housing portion 22 of a gas passage 21. The valve element 4 is turnably supported by the valve seat members 3A, 3B. The valve seat members 3A, 3B are formed of a resin. A sub-valve seat member 8 in the form of a metal cylinder is slidably provided in an outflow hole 24 of the gas passage 21. The sub-valve seat member 8 is biased by a metal coil spring 9 toward the side of the valve element 4. When the valve seat members 3A, 3B is destroyed by fire, the coil spring 9 presses the sub-valve seat member 8 into contact with the valve element 4, and further presses and moves the valve element 4 toward the side of an inflow hole 23 to press the valve element 4 into contact with a sub-valve seat surface 27. COPYRIGHT: (C)2004,JPO
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