GB976114A - Self priming centrifugal pump - Google Patents

Abstract

976,114. Centrifugal pumps. BELL & GOSSETT CO. July 16, 1962 [July 20, 1961], No. 27228/62. Heading F1C. A self priming centrifugal pump having an impeller 22 supported about a substantially horizontal axis in a casing 10 which defines a main chamber 21 for a reserve of liquid in which the impeller 22 is rotatable, an inlet 12 communicating centrally with the impeller and an outlet 11, and a number of vanes 31-37 spaced about the periphery of the impeller and spiraling forwardly in the direction of impeller rotation and outwardly to define discharge flow passages communicating between the main chamber 21 and the periphery of the impeller, is characterized in that at least one vane with its inner edge originating adjacent the lower downward sweep region of the impeller periphery has its inner end located in such position relative to an outer end portion of an adjacent preceding vane to provide therebetween a reverse flow path from the main chamber 21 to the impeller periphery that is shorter and more direct than any reverse flow path associated with vanes having inner end portions originating adjacent the other regions swept by the impeller periphery. Vanes 31, 32, of a fixed diffuser 30 having preferably uniformly arranged vanes 31-37, are shortened to establish radial flow paths 31A, 32A near the bottom of chamber 21 where a substantially maximum head of reserve liquid acts to establish a high pressure differential and thereby create a reverse radial flow of air free liquid from the chamber 21 to the periphery of the impeller 22. The turbulence thereby created in this region mixes air with the liquid to form a foamy mixture from which air bubbles are peeled off, principally at the inner edges of vanes 33 and 34, and are discharged upwardly to prime the pump by the momentum induced by the impeller and their inherent buoyancy. Long reverse flow passages exist between vanes 35, 36 and 37, which have inner edges close to the impeller periphery, so that an hydraulic seal is maintained between the high pressure air within the pump chamber 21 and the low pressure air within the impeller 22, thereby eliminating the likelihood of creating a vortex of air. Since the vane 33 is closely adjacent the lower downward sweep region of the impeller periphery it may likewise have a portion of its inner end eliminated. In two alternative embodiments (not shown), having a diffuser with four and five vanes respectively, only one vane in each diffuser is shortened and the angle of the vanes with respect to the impeller periphery is so small that the inner end of the shortened vane still remains closely adjacent the impeller. The resulting reverse flow path, in the case of the four vane diffuser, is radial but, in the case of the five vane diffuser, it is only substantially radial. Specifications 546,541 and 691,362 are referred to.