GB1065849A - Improvements relating to pump impellers - Google Patents

Abstract

1,065,849. Centrifugal pumps. FLYGTS PUMPAR A.B. Dec.30, 1963 [Jan. 5, 1963; July 19, 1963], No.51180/63. Heading F1C. Fig. 1 shows a single-channel pump impeller in which the single impeller blade 1 is formed with a step 3 adjacent its inlet edge 2, and a further step 4 situated, for example, opposite the step 3 and providing an outflow direction 5 which diverges from the adjacent blade surface 6. Any solids contained in the liquid being pumped are deflected away from the impeller blade surface by the steps, whereby wear caused by abrasive solids is reduced or damage to fragile solids such as fish or fruit is avoided. The turbulence produced behind each step serves to carry away any gases entrained in the liquid. A step 7 may be provided on the outside surface of the blade 1 to deal with entrained air between the blade and the walls of the pump casing. Fig. 3 shows how a step can be formed by curving the outlet edge 10 of a blade 9 outwardly. In a two-channel pump, the steps on the two blades may be diametrically opposite one another. In both single-channel and two-channel pumps, Figs. 2 and 7 (not shown), the abrupt steps may be replaced by scalloped contours such as those shown at (8), (21) and (22). Fig.6 (not shown) shows a single S-shaped blade provided with steps (24) and (25) on its pressure and suction sides, respectively. In a single-channel pump Fig.4 (not shown), the steps may be disposed at right angles to the impeller axis, being formed by abrupt increases in the radial dimension of the impeller at the junction of the axial inlet orifice of the impeller with the single impeller blade. As a further alternative, the steps may be disposed helically. The action of the steps or other contours may be reinforced by creating a whirl in the liquid by means of an auxiliary impeller (37), Fig. 14 (not shown), located adjacent the back-plate of the main impeller and comprising blades extending between a hub (38) and a peripheral ring (39). The hub (38) deflects solids away from these blades. The ring (39) may be omitted. The auxiliary impeller (37) may be driven through pawls or may be independently rotated, either slower or faster than the main impeller, by means of an inner shaft passing through the hollow shaft of the main impeller. Alternatively, the auxiliary Impeller may be fixed to the main impeller, either on the front surface of the back-plate of the main impeller or recessed into the back-plate. In single-channel impellers, the blades of the auxiliary impeller may be of varying radial length to conform to a helical flow path through the main impeller, longer blades having less axial depth than shorter blades to provide a hydrodynamically uniform action of the auxiliary impeller. The steps or other blade profiles and the auxiliary impeller may be replaceable and may be of elastic or plastics material.