Abstract: A nozzle device for purging a vacuum pump includes a nozzle, the top portion of the nozzle is a tapered portion, two sides of the tapered portion are installed with nozzle holes for guiding the exhausted air sub-flow to be exhausted from the two sides of vent end.

Abstract: A multistage pump includes a shaft assembly and a housing and spacing plates. The shaft assembly completed by forming shafts and rotors integrally. The spacing plates defining a plurality of successive compression chambers, each chamber is delimited by two symmetrical spacing plates, there has a ring groove associated with the spacing plates, and having an elastic component placed. When the elastic component pressed by the housing, it became leakage and the clearance between the rotors and the spacing plates be easily controlled, by this way, the pump using parts are easy to manufacture, can be machined accurately and which enable highly accurate assembly to be achieved. As to the assembling method, which is characterized by mounting the high pressure end axial bearing seat and the high pressured end plate, then to control the clearance between the high pressure end plate of the bearing seat and the rotors. Furthermore, to install the spacing plates and the housing make the compression chamber formed.