Screw type vacuum pump

摘要

A screw vacuum pump including a plurality of casings and a pair of rotors defining a plurality of working chambers. The working chambers are constituted by working chambers whose volumes undergo a change as the rotors rotate, and working chambers whose volumes undergo substantially no change as the rotors rotate. The screw vacuum pump is capable of achieving pressure of 10-1 to 10-4 Torr or a low or medium vacuum by means of a single pump operating in a single stage.