FLOW RESTRICTING DEVICES IN PUMPS

Restriction of flow along a shaft by interposing a split ring in the annulus between the shaft and housing. When the ends of the split ring are separated, the effective diameter of the ring is increased and a clearance between the ID of the split ring and the shaft is maintained permitting flow. When the ends are released and allowed to come together the split ring closes the annular gap and restricts the flow. Also contemplated is the restriction of flow along a shaft by interposing an axially movable sleeve in the annulus between the shaft and housing. Flow through the annulus between the movable sleeve and the shaft is resisted by the clearance or features such as labyrinths, to thereby create a differential pressure from one end of the sleeve to the other.