| 摘要 |
Flushing valves of the type having a control chamber with a movable wall are disclosed, the chamber being partially emptied to cause the main valve surface and seat to separate and open the valve, and being slowly refilled to close the valve. A cleaning needle is provided which moves in the restricted inlet to the chamber to remove dirt and scale therefrom. In one form, the valve actuating element sequentially lifts a valve closure element, to which the needle is secured, from a seat to open said outlet and thereafter acts on the movable wall part to cause a reduction in the volume of said chamber and force some of its contents through the open outlet. In a further form, the actuating element pressurizes the chamber by forcing the movable wall in the direction which reduces the volume thereof. The increased pressure forces a flexible wall part of the chamber from a sealing surface to allow liquid to flow from the chamber.
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