| 摘要 |
PURPOSE:To prevent the reverse diffusion of oil to the vacuum side by making a screw rotor of a vertical type, providing a bearing in the rotor, and requiring no bearing on the vacuum side. CONSTITUTION:A pair of rotors 1, 2 are supported by a bearing 4 located at the discharge side with a slight gap between the rotors in a casing 3 and between the rotor and the casing, and a bearing 6 located in the rotor. The rotor is driven by an accelerating gear 9 and a motor 10, and the bearing 6 in the rotor is fitted to a stator 16 integrated with the casing. Accordingly, no bearing is required to be provided on the vacuum side, and the reverse diffusion of oil to the vacuum side can be prevented.
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