Vacuum pump e.g. liquid-sealed vacuum pump, for use as rotary vane pump, has two pumping stages respectively arranged at vacuum side and pressure side, where one of pumping stages is implemented as screw pumping stage with screw pump unit

摘要

The pump has two pumping stages (1, 2) arranged at a vacuum side and a pressure side, respectively. One of the pumping stages is implemented as a membrane pumping stage with a membrane pump unit (10). The pumping stage is dimensioned such that the pumping stage provides 20 percentage of pumping speed to the pump at atmospheric pressure. The other pumping stage is implemented as a screw pumping stage with a screw pump unit (5). A pair of screw-shaped rotors (7a, 7b) is supported at the screw pump unit. The pumping stage is implemented as the screw pumping stage whose medium-contact surfaces are made of chemically persistent fluoroplastics or metal coated with fluoroplastics or ceramics.