Patent ID: 7278839

Claim:
A multi-stage vacuum pump comprising: a plurality of casings axially connected in series, said casings each defining a compression chamber inside thereof; a plurality of partition plates each respectively mounted between two adjacent casings of said plurality of casings to separate the compression chambers of said two adjacent casings, said partition plates each having a predetermined wall thickness and two through holes; a mover module, said mover module comprising two parallel shafts respectively extended through the two through holes of each of said partition plates, and a plurality of rotors symmetrically formed integral with said two parallel shafts respectively and arranged in pairs, wherein each pair of two adjacent rotors of said plurality of rotors is received in one corresponding compression chamber of said casings; and a synchronizer gear module being driven to rotate said shafts and said rotors synchronously; wherein said partition plates each have a front face, a rear face, and at least one air path respectively formed in the respective wall thickness and extended from said front face to said rear face; and wherein the at least one air path of each said partition plate is formed in between the two through holes of the respective partition plate.