| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-stage Roots vacuum pump consuming a less power with a normal pressure during operation. SOLUTION: The multi-stage Roots vacuum pump comprises multi-stage Roots type rotors 3, 4, 5, 6, 7, 8 arranged on two rotary shafts 9, pump chambers in which mutually mating rotors at each stage of two shafts are stored as one set, and a casing provided at the periphery of the rotors and having bulkheads between the pump chambers and stages, wherein the pump chambers are connected in series, and the number of leaves of the rotors 7 and 8 at the rear stage is made larger than the number of leaves of the rotors 3, 4, 5, 6 at the front stage.
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