Vacuum pump

Claim 1

A multi-stage liquid ring pump comprising a casing, a rotatable drive shaft at least partly in said casing, a plurality of lobes in said casing and mounted in stages in the direction of the longitudinal axis of said drive shaft, a rotor on said drive shAft a port member disposed in a central opening of said rotor, a fluid entry means in said casing, communicating with an external cold seal liquid source, a fluid outlet means in said casing, a plurality of impeller means in successive stages mounted on said rotor, a separating member on the rotor between two successive stages of said impeller means, said separating member having an inner peripheral edge defining a running clearance with an adjacent port member surface, a substantially annular groove in said separating member edge, said groove being connected to said fluid entry means whereby cold seal liquid is introduced from said external source to the interior surfaces of said impeller means under relatively small pressure, to flow over the surface of the liquid of the liquid ring in the first stage of the pump in order to effectively seal the high and low vacuum areas of successive stages of said impeller means and to create a higher vacuum in the pump and reduce flashing between said fluid entry means and said fluid outlet means.