| 摘要 |
PROBLEM TO BE SOLVED: To certainly seal fluid by raising contact surface pressure between a valve chest seat part and a valve element seat part and to remarkably reduce valve opening and closing operating torque. SOLUTION: An elastic rubber seat 21 and a backup ring 24 free to elastically press on a valve element seat 10 at the time of closing a ball type valve element 7 are provided on a ring sheet part 2 provided on a valve chest 4 on the upstream side of the ball type valve element 7 at least, and an air supply pipe 23 free to inject and extract compressed air is provided in a ring space 22 formed on the back of these elastic rubber seat 21 and backup ring 24.
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