| 摘要 |
<p>A valve body (15) is formed of two half sections (16, 18) which are secured together to define a drain line passage (12) and to confine therebetween a thin gate valve (45) between a lower open position and an upper closed position. Actuator (110) includes flexible bellows (80) confined between a cylindrical wall (88) and cover (110). Valve body (15) and bellows (80) define an expandible chamber connected by a bottom port or extension line (97) to the drain line (12). If sewage water backs up, air within the fluid chamber expands bellows (80) upwardly to close valve (45). When sewage water flows from the drain line (12), bellows (80) moves downwardly due to differential pressure and top plate (102), automatically returning the valve blade (45) to its open position.</p> |
