| 摘要 |
PURPOSE: To obtain satisfactory sealability for a long time with a simple structure without exchange operation of a seal member requiring decomposition of a piping and a valve itself. CONSTITUTION: A main seal member having a first seat retainer 21 and a backup seal member having a second seat retainer 22 are parallely arranged between a body 11 and a ball 14 as a seal member 20 in a diameter direction. The seat retainers 21, 22 are energized to the side of the ball 14 by means of spring members 25, 26. A rotary member 30 is arranged near the second seat retainer 22. Switching is performed between the position where the second seat retainer 22 is locked at the position that an elastic seat 24 on the side of the backup seal is separated from the ball 14 and the position where it is released. This switching is preformed by external operation such as excessive rotation of the ball 14. |
