| 摘要 |
PROBLEM TO BE SOLVED: To provide especially simple and low-cost dynamic attenuation by the method highly effective for suppressing the discharge noise. SOLUTION: The discharge noise of a rotating vacuum machine with a complementary outline is attenuated by disposing a transfer device 25 having independent cavities, for example, cavities 24-24g on a rotor 25 rotated with a shaft 26 between a discharge part 16 of the primary pump and an outlet 23 to the atmosphere. The cavities 24-24g, by moving from the discharge part 16 to the outlet 23 one by one, coincidently separate the discharge part 16 and the outlet 23 from each other.
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