| 摘要 |
<p>A gas diffuser for use in aerobic sewage treatment includes a valve device operable to seal the interior of the diffuser from a gas supply pipe whenever the pressure of gas in the pipe is below a predetermined level, increase in the gas pressure above the predetermined level causing the valve to open. The amount by which the valve opens is dependent upon the pressure of gas in the supply pipe. In one embodiment the valve comprises an inlet port one end of which is closed by a ball held there by gravity until lifted by the pressure of gas applied to the inlet port. The sides of the bore in which the ball rises with increasing gas pressure may diverge along the length of the bore away from the inlet port. In an alternative arrangement the walls of the bore are slotted. Alternatively, the valve member may comprises an inlet port coupled to a member having flexible walls which normally close the inlet port and which flex to open the port when the pressure applied to the inlet port exceeds the predetermined level. <IMAGE></p> |
