Variable geometry collector for centrifugal pump

In an impeller-type pumping arrangement, the combination comprising:

• a housing having an impeller chamber and a collector with an inlet encircling the impeller chamber;
• an impeller mounted for rotation within the impeller chamber for forcing fluid into the collector via the inlet thereof;
• a ring mounted upon the housing in coaxial relationship to the impeller for rotation and for axial movement toward and away from the collector such that the inlet area of the collector is respectively reduced and increased;
• cam means responsive to rotation of the ring to axially move the ring such that the inlet area is reduced and increased in accordance with the sense of rotation of the ring;
• an actuator responsive to a control signal operatively connected to the ring for rotating the ring to reduce the inlet area of the collector for low flow rates;
• a metering means in fluid connection with the collector for regulating the rate of flow therethrough irrespective of the inlet area of the collector as determined by the position of the ring;
• means responsive to the rate of flow through said metering means to generate a rate of flow signal indicative of the flow through the impeller chamber and the collector;
• and
• means responsive to the rate of flow signal to generate the control signal for the actuator when the rate of flow falls below a predetermined level.