| 摘要 |
A cylindrical housing for insertion in a conduit has a conically seated circular aperture accommodating a valve disk (24), pivoting, near one edge, on a transverse shaft extending into a cylindrical side-case, with a position indicator on the end. In case of excessive local heating, the fusing of a thermally sensitive pin (41) allows the valve to close under its own weight assisted by a rotary spring box (11), which still exerts force after closing, ensuring a firm seal. The disk is thickened on its upper face, augmenting its weight. Closing is also initiated by energising, via a remote manual switch or heat sensor, a release solenoid (15) - opt., hydraulic or pneumatic actuator - in the case.
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