Patent ID: 6554593
Filing Date: 2003-04-29
Classification: F04C,F05C

Abstract:
A screw rotor-type dry vacuum pump comprising:a pair of right and left handed screw rotors, a cross section of each of which is formed by a Quimby curve, a circular arc and a quasi-Archimedean spiral curve; a casing having an inlet and an outlet in which casing the pair of screw rotors are received and intermesh with each other so as to pump a process gas from the inlet of the casing and discharge the process gas from the outlet of the casing; each screw rotor having a plurality of leads; a nitrogen-supplying tube that communicates with a position near the outlet in the casing, the nitrogen-supplying tube supplies nitrogen into the chamber to increase the heat capacity of a processed gas being pumped by the dry vacuum pump; and an outer pipe that connects the outlet with a scrubber or a trap, the outer pipe being a straight pipe that does not include a silencer.