1. Field of the Invention
The present invention relates to a turbomolecular pump for evacuating gas by means of a rotor having blades and/or spiral grooves which rotates at a high speed.
2. Description of the Related Art
FIG. 6 shows a conventional turbomolecular pump. The turbomolecular pump comprises a rotor R having a main shaft 10 and a rotating cylindrical section 12 which rotates integrally with the main shaft 10, a stator S having a stationary cylindrical section 14 which surrounds the main shaft 10, and a cylindrical casing 16 which surrounds the rotating cylindrical section 12. A base B is fixed to the stationary cylindrical section 14. Between an apparatus (or a chamber) to be evacuated and the turbomolecular pump, there are provided a conductance adjustment valve 100 and a gate valve 110.
However, in the conventional turbomolecular pump shown in FIG. 6, since drive mechanisms of the respective valves are provided adjacent to the respective valves, the overall structures of the valves are extremely enlarged to thus increase the size of the overall structures of the turbomolecular pump including the valves.