Improvements in or relating to centrifugal pumps

886,248. Centrifugal pumps. EDWARDS, M. L. May 16, 1958, No. 15835/58. Class 110 (1). In an impeller for a centrifugal pump comprising blades projecting from a back plate, the back plate is shaped to provide orifices on the trailing sides of the blades and to allow liquid at the leading sides of the blades to flow past the orifices to entrain vapour or gas through the orifices from between the blades, portions of the back plate extending from leading edges of the blades to points on the blades adjacent the orifices. In the submersible centrifugal fuel pump shown in Fig. 1, the impeller back plate 52 is cut away as shown in Fig. 3 to form projections 53 adjacent each impeller blade. Preferably, a kink 62 is provided in each impeller blade, fading out towards the bottom edge of the blade. The inlet portion of each impeller blade between the leading edge 51 and the kink 62 is shaped to provide an axial component of motion towards the back plate 52. A jet of liquid passes upwardly along the pressure face 60 of each impeller blade at the kink 62 and through the adjacent cut-away part of the back plate 52 towards a stationary diffuser 40, thereby exerting an ejector effect at an orifice 64 to entrain and remove gas or vapour accumulating at the opposite face 61 of the blade. After passing through the diffuser 40, the mixture of liquid and gas or vapour escapes into the fuel tank 11.