| 摘要 |
<p>A valve body is formed in two half sections which are secured together to define a drain line passage and to confine therebetween a thin gate valve blade for movement between a lower open position and an upper closed position. A cylindrical bellows is sealed to the valve body above the passage and is covered by circular top plate which is connected by a rod to the valve blade. The bellows defines an expandable fluid chamber connected by a bottom port to the drain line passage. The valve body is connected within a sewage drain line extending under a floor. In the event sewage water backs up within the drain line, air within the bellows is compressed to expand the bellows upwardly for closing the valve. When the sewage water drains from the drain line, the air pressure reduces, and the bellows collapses due to the weight of the top cover plate and automatically returns the valve blade downwardly to its open position.</p> |
