Patent GB-939888-A (GB)
Title: Improvements in or relating to self-priming gas-expelling pumps
IPC: F04C7/00
Filed: 1962-02-14
Abstract: 939,888. Centrifugal pumps. M. L. EDWARDS. Feb. 14, 1962, No. 5698/62. Class 110 (1). A self priming pump assembly comprises an impeller having blades with first portions shaped to induce fluid flow axially of the impeller from an axial fluid inlet to an impeller chamber and further portions shaped to discharge fluid centrifugally from the impeller chamber to a volute pumping chamber, an axial gas outlet communicating with a zone in the impeller chamber such that fluid directed to the zone by the first portions of the impeller blades is not substantially affected by the centrifugal discharge force of the further portions of the impeller blades, and a gas pump arranged to draw fluid through the gas outlet from such zone for preventing the impeller from becoming gas bound. A booster pump assembly, Fig. 1, for an aircraft, comprising a liquid pump A, a liquid ring gas pump B and a driving motor 10, is attached by screws 12 to a plate 11 secured by screws 13 and mounting ring 14 to the outside of a fuel tank 9. The inlet pipe 16 is preferably provided with a curved pipe extension or hose (not shown) extending down close to the bottom of the fuel tank. Each blade 42, Figs. 1 and 3, of the impeller 30 of the liquid pump A, extends from a forwardly extending screw-shaped leading end 43 approximately 180 degrees in compound curvature to a trailing end 46, which is reduced in axial width to correspond with the width of the volute chamber 20 and is approximately parallel to the rotational axis. Each blade is connected to a transverse crescentshaped wall 50 connected to hub 38 and a rearwardly extending annular flange 51. The blades 42 have sharp leading edges 44 which slice into the approaching liquid, the latter then being fed axially by the screw action of the leading ends 43 and then centrifugally, by the trailing ends, to the outlet 21. Entrained gas and vapour is likewise initially impelled axially, but separates out centripetally and passes through openings 52 and an annular passage 40 to a suction chamber 41. Liquid collecting in a sump 69 is drawn through a passage 67, Figs. 1 and 10, to one side of the impeller 31 of the liquid ring gas pump B, and gas and vapour are drawn through a passage 65A to the other side of the impeller 31. The whole booster pump assembly may be rotated 90 degrees so that the passage 65A instead of the passage 67 passes into the sump 69. The liquid fed through the passage 67 forms the liquid ring in the pump B, and any excess, together with the gas and vapour, is passed through outlet ports 72, Fig. 6, into a chamber 73 and through openings 81 between axial-flow blades 80 to a reservoir 85. The blades 80 maintain a whirling pool of liquid in the reservoir 85 which keeps the gas and vapour in a ring around hub 79. Additional gas, vapour, and liquid passed to the reservoir from the pump B is discharged back to the fuel tank 9 through an outlet pipe 86, which controls the radial depth of the whirling liquid so that the blades 80 are in constant engagement with a portion of the whirling liquid to keep the liquid rotating and also to return some of the liquid to the pump B to maintain the liquid ring therein. When the pump assembly is not operating, an annular flange 37 and flanges 82 retain sufficient liquid in the suction chamber and pump B respectively, irrespective of any manoeuvre of the aircraft, to start pumping action when required.