GB776635A - Improvements relating to centrifugal pumps - Google Patents

Abstract

776,635. Centrifugal pumps. FABIG, G. Nov. 7, 1955 [Nov. 24, 1954], No. 31794/55. Class 110 (1). A self-priming centrifugal pump comprises a casing in two halves and provided with suction and outlet openings, a lateral annular passage for liquid provided only in the suction-side casing half, a receiving space in the pressureside casing half which extends only over a fraction of the periphery and is arranged substantially symmetrically with respect to the outlet opening into which it runs, and inclined or helically twisted impeller blades arranged with the edges of their front surfaces which are adjacent the receiving space trailing, relative to the opposite edges, with respect to the direction of rotation of the impeller. The suction side casing half 1, Fig. 1, has a lateral annular working passage 3 which, starting adjacent the suction opening 2, gradually increases in crosssection in the direction of rotation and finally decreases, the last part of the passage being brought closer to the axis of the pump in spiral fashion. The pressure side casing half 5, Fig. 6, has a receiving space 9 having its greatest depth in the region of a discharge opening 6 and gradually decreasing in width towards each end. A further discharge opening 7 is provided. The impeller comprises radial blades, each blade having a wedge-shaped cross-section, Fig. 12, with the front and rear surfaces bounded by a concave and a convex arc respectively. The edge 11 of the front surface trails with respect to the direction of rotation. A triangular pocket 12 is provided adjacent the casing half 1. The rear wall 13 of the pocket 12 is sloped off so that in the region of the discharge opening 6 each blade has the cross-section shown shaded in Fig. 12. During priming, the spaces between the impeller blades are filled with liquid through an auxiliary opening 8. The liquid and air entering through the suction opening 2 passes partly into the spaces between the blades and partly into the pockets 12. The liquid is thrown outwards by centrifugal force, to augment the ring of liquid in the passage 3, and the air is expelled through the discharge opening 7 by displacement effect. On completion of priming, the liquid is discharged partly by displacement effect through opening 7 but mainly by centrifugal effect through opening 6. The liquid entering the pockets 12 forms a cushion which tends to neutralize the end thrust of the impeller.