| 摘要 |
PURPOSE:To prevent the excessive rotation of an exhaust fan so that the life of the fan is not shortened by providing, in a duct, an openable and closable pressure valve capable of being opened to the inside of the duct by the negative pressure in the duct when the negative pressure exceeds a prescribed value. CONSTITUTION:The gas from each unit is passed in a dust collecting filter 2 and an ozone treatment filter 3 in this order through a duct 1 to conduct the dust removal and ozone treatment of floating toner. The gas after passed through the filter is exhausted by an exhaust fan 4. A valve 5a provided between the filters 2, 3 and the fan 4 in such a manner as to be opened to the inside is closed by a coil spring 6a when the dust collecting filter 2 is new, but when the dust collecting filter 2 is clogged to generate a negative pressure between the ozone treatment filter 3 and the fan 4, the pressure valve 5a is opened to the inside of the duct 1 against the elastic force of the coil spring 6a. The gas is thus introduced into the duct 1 by opening the pressure valve 5a, and the rotation rise of the exhaust fan 4 can be suppressed. |
