GB793623A - Improvements relating to electrically driven pumps - Google Patents

Abstract

793,623. Centrifugal pumps; stuffing-box substitutes. GENERAL ELECTRIC CO. July 22, 1954 [July 24, 1953], No. 21438/54. Classes 110 (1) and 122 (5). A sump pump comprises an opening formed in the driving motor casing and communicating with the exterior, a pressure-sensitive means located in the opening and responsive to the liquid level, a switch operated by the levelresponsive means to energize the motor when the liquid reaches a predetermined level, the pump impeller having blades which exhaust the motor casing to create a holding force on the level-responsive means, and the holding force being relieved to stop the motor when the liquid level has fallen sufficiently to cause the blades to pump air. In the sump pump shown, a seal 30, of rubber or neoprene, prevents leakage of sump water into the motor casing 5 when the pump is stationary. When the water level in the sump has risen sufficiently, the hydrostatic pressure on the underside of a diaphragm 35 deflects the diaphragm to close a snap-action switch 36, thereby energizing the motor 7. The rim 33 of the seal 30 flies outwardly under centrifugal force and out of sealing contact with a stationary wall 23, and auxiliary blades 38 on the back of the pump impeller take over the function of preventing the sump water from reaching the motor casing 5. Initially, the blades 38 remove water from a cavity 14 and thereafter pump only the water leaking through a clearance between the blades 38 and an adjacent portion 40 of the pump casing. In recirculating the water, the blades 38 also withdraw air from the motor casing 5, causing a partial vacuum which exerts a holding force on the diaphragm 35 so that the switch 36 remains closed despite the fact that the water level in the sump is falling. When the water level has dropped to the point at which the impeller pumps air, the blades 38 cease to pump water and maintain a vacuum in the casing 5, and the switch 36 opens to stop the motor. The shaft bearings are lubricated by lubricant held in absorbent material 19, from which a wick 26 extends to an annular groove 25, leakage of lubricant being dealt with by slingers 21, 29. In a modification, the pump casing 1 is divided into a pumping chamber and a sealing chamber by an annular baffle in alignment with the impeller backplate 10, and an opening in the casing wall is provided above the level of the baffle. The blades 38 then pump against the pressure of the water in the sump instead of against the discharge pressure of the pump.