| 摘要 |
PURPOSE:To prevent a rotary disk setting part side from the invasion of polluted gas containing dust by separating a closing means into a rotary disk setting part and a driving mechanism setting means, extracting air from the rotary disk setting part to the driving mechanism setting part and exhausting air to the rotary disk setting part through a prescribed course. CONSTITUTION:The closing means 13 is separated into the rotary disk setting part 14 and the driving mechanism setting part 15 and air is extracted from the setting part 14 to the setting part 15. The pressure of the means 13 on the setting part 15 side is not easily affected by pressure on the upstream side of a transducer supporting means 5 on the setting part 14 side and a greater part of air flowing from the setting part 4 side to the setting part 15 side through a 1st aperture part 17 is allowed to flow from the downstream side of the means 5. The inflow air cools a driving mechanism system, is filtered through a filtering means 18 of an exhausting means 22 and then exhausted to the setting part 14 side through a 2nd aperture part 20. Consequently, the rotary disk setting part 14 in the closing means 13 can be prevented from the invasion of polluted air.
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