Patent ID: 8251678

Claim:
A vacuum pump unit comprising: a main pump disposed at an outside-pressure side; a booster pump disposed at a vacuum side; and a pump mount base having a substantially horizontal upper surface and a substantially vertical side surface, wherein said booster pump and said main pump are coupled in series, wherein said booster pump has a higher pumping speed than that of said main pump, wherein each of said main pump and said booster pump includes: a pair of pump rotors; a casing having an inlet port and an outlet port; and a pair of magnet rotors rotatable with said pair of pump rotors, wherein a communication passage is formed in said pump mount base for providing fluid communication between said outlet port of said booster pump and said inlet port of said main pump, and wherein said booster pump is mounted on said upper surface of said pump mount base, and said main pump is mounted on said side surface of said pump mount base.