Patent ID: 6302641
Filing Date: 2001-10-16
Classification: F04D

Abstract:
A multiple-type vacuum pump, comprising:a rotatable rotor, within a casing having a cylindrical inner surface, around a rotary shaft disposed in coaxial alignment with said casing, said rotor having an air transfer portion on an outer surface thereof for transferring air in a direction of said rotary shaft at the time of rotation;said air transfer portion having a turbo-molecular type pump air transfer portion located at an upstream portion of an air transfer direction, and a screw type pump air transfer portion located at a downstream portion;said screw type pump air transfer portion having a plurality of screw threads each having a spiral shape with a width of 5 mm or more and disposed circumferentially at prescribed intervals in said downstream portion of said outer surface of said rotor, and screw grooves formed between each of said screw threads, said screw type pump air transfer portion taking in the air that has streamed into an upstream edge thereof at the time of rotation and transferring it to the downstream side; andsaid turbo-molecular type air transfer portion having a plurality of vanes with a fixed vane angle and formed circumferentially at prescribed intervals in said upstream portion of said outer surface of said rotor, and air transfer grooves formed between each of said vanes, each of said vanes having an upstream edge with a width of 3 mm or less and a downstream edge formed as to be continuous with an upstream edge of said screw threads of said screen type pump air transfer portion, a downstream edge of a base of said air transfer grooves formed as to be continuous with an upstream edge of a base of said screw grooves, wherein said turbo-molecular type air transfer portion takes the air that has been brought in from an upstream edge at the time of rotation, compresses it, then transfers it to the upstream edge of said screw type pump air transfer portion.