Importance

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Abstract

A positive displacement pump, particularly a liquid metering or batching pump, includes a fluid inlet, a pump chamber of variable volume, an outlet through which fluid leaves the pump chamber, a driven injection member for repetitive displacement of fluid from the pump chamber, and a valve which functions to open and close a flow passage connecting the inlet with the pump chamber. The flow passage is formed by a gap which extends around at least the major part of the circumference of the pump chamber and which can be open to a height which varies from a smallest value at the ends of the gap to a largest value at a location between the circumferential ends of the gap. The valve includes a valve member which extends along the flow passage and which is pivotally mounted on a pivot adjacent the circumferential ends of the passage.

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First Claim