| 摘要 |
Metering pumps for the metered feed of liquids are fitted with an intake valve (8) built into an intake line from an intake container, a pump chamber (5) downstream of it with a pumping component (6) altering its displacement volume, a pressure valve (23) leading to the metering connector (22) and a vent and by-pass valve (20) built into a return line (21) leading to the intake container. In order to keep the quantity of by-passed metering liquid as small as possible while maintaining adequate venting, there is valve chamber (4) between the pressure valve (23) and the pump chamber (5) and separated from the latter by a return valve (12) and a movable control wall (13), in which is incorporated the vent (20) controlled by the control wall (13), opening on the suction stroke of the pumping component (6) and closing on its delivery stroke. There is also preferably in the valve chamber (4) a prestressed displacement wall (26) altering the volume of said chamber (4) in the opposite direction to that of the control wall (13).
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