| 摘要 |
PURPOSE:To shorten a time for collecting dusts by combining and using filters having different dust collecting efficiencies. CONSTITUTION:In order to collect dust generated in a DE efficiently, an air filtered A having a good efficiency and an air filter B having a lower efficiency than the filter A are provided in an independent circulating passage. Since the mesh of the air filter B is rough, an air passes through rapidly, the number of air stream passing through the air filter B is increased. Accordingly, coarse dust can be collected in a short time. Since the mesh of the air filter A is fine, the passing of the air is slow and the number of the air stream passing through the air filter A is reduced, and the air stream in which the coarse dusts taken by the air filter B passes through the air filter A, thereby the dust collecting time is shortened.
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