Negative pressure cut valve

摘要

A negative pressure cut valve disposed between a feed pipe and a forward pipe includes a main body having a first outer wall and a second outer wall, an urging spring provided on the first outer wall, a diaphragm provided on the main body and actuated by the relative action of the force of the urging spring and the inner pressure on the feed pipe side to produce an opening action in the state in which the inner pressure on the feed pipe side rises is above the inner pressure on the forward pipe side and a closing action in the other pressure state, and a valve provided on the main body and actuated to produce an opening action in the state in which the inner pressure on the feed pipe side falls below the inner pressure on the forward pipe side and a closing action in the other pressure state. The first outer wall has a first atmospheric vent formed therein. The second outer wall is disposed around the periphery of the first atmospheric vent and enabled jointly with the first outer wall to define an empty space for precluding intrusion of extraneous substances. The empty space has a capacity at least above an operating capacity of the diaphragm. The second outer wall has a second atmospheric vent formed therein and endowed with a function of releasing pressure and a function of discharging water.