Patent ID: 6123526
Filing Date: 2000-09-26
Classification: F04C

Abstract:
A multistage pump comprising:a shaft assembly, which includes a pair of shafts and a plurality of rotors wherein the shafts and the rotors are formed integrally;an end plate provided in a bottom portion of said shaft assembly;a first rotor housing provided immediately above said end plate for housing a first pair of interacting rotors and defining a first compression chamber therein;a plurality of successively stacked composite housings provided above said first rotor housing;wherein each of said composite housing comprises:a rotor housing to house a pair of interacting rotors and define a respective compression chamber, said rotor housing also containing a through hole to allow gas to travel from one compression chamber to another;a cavity disposed below said rotor housing and having a width greater than said rotor housing for receiving a spacing plate therein; andan O-ring received in an O-ring groove provided on an upper face of said spacing plate to define a clearance between said rotors and said spacing plate within each composite housing;further wherein within each composite housing, said rotor has a height shorter than a height of said rotor housing, said spacing plate has a height shorter than said cavity, and each said spacing plate containing two identical half plates wedged together around said pair of shafts.