| 摘要 |
PROBLEM TO BE SOLVED: To provide an evacuating apparatus having high energy efficiency, when suction side pressure is the ultimate pressure or a certain degree of vacuum, by decreasing the motive power by differential pressure. SOLUTION: The evacuating apparatus 100 has a roughing vacuum pump B and a booster pump A. The roughing vacuum pump B and the booster pump A are respectively constituted of screw vacuum pumps. A designed pumping speed of the roughing vacuum pump B is set in the size sufficiently smaller than a designed pumping speed of the booster pump A, but functioning as the roughing vacuum pump. The number of turns of screw of the booster pump A is set less than the number of turns of screw of the roughing vacuum pump B. COPYRIGHT: (C)2008,JPO&INPIT
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