| 摘要 |
<p>A check valve (10) comprises, a flexible tube (11) having first and second e nd portions defining an inlet (13) and an outlet (14), respectively, and a rigi d valve body (12) surrounding the flexible tube (11). The end portions of the flexible tube are sealingly fixed to the valve body (12) to define an enclos ed space (17) between the exterior of the flexible tube and the interior of the valve body. A fixed volume of a substantially incompressible fluid is locate d in the enclosed space (17). When the pressure at the outlet (14) is greater than the pressure at the inlet (13), the flexible tube is substantially collapsed so as to close the valve or allow severely restricted flow. Howeve r when the pressure at the inlet is greater than that at the outlet, some of t he fluid is displaced from the inlet area towards the outlet area so that the flexible tube (11) is expanded in the area adjacent the inlet and the tube i s substantially open. A pump based on a series of valves having some of the attributes of the check valve is also disclosed, as is a vacuum driven sewer system that incorporates a pinch valve.</p> |
