| 摘要 |
PURPOSE:To reduce a load on shaft seal parts by providing a multi-stage vacuum Roots blower with a centrally disposed compression chamber serving as a target-high-negative-pressure reaching vacuum chamber and compression chambers disposed at opposite sides of the chamber serving as vacuum chambers having a pressure near to the atmospheric pressure. CONSTITUTION:A multi-stage vacuum Roots blower has a centrally disposed target-high-negative-pressure reaching vacuum chamber 61 and low negative pressure compression chambers 64 disposed at opposite sides of the disposing direction of the compression chamber. There are disposed a second chamber 62 and a third chamber 63 between the low negative pressure compression chambers 64 and the target-high-negative-pressure reaching vacuum chamber 61, respectively, differential pressures between the respective compression chambers and between the low negative pressure compression chamber 64 and the atmosphere being set at small values. As a result, a load on shaft seal labyrinth parts 23 through 28 of a shaft for driving a Roots rotor 10 is reduced for improving seal performance of shaft seal parts.
|
