| 摘要 |
PURPOSE:To completely close a ventilating port during the time when no ventilation is performed and at the same time prevent ventilating flow from generating turbulence during ventilation by a method wherein a shield curtain, composed of an impermeable part and permeable part and stretched across rollers provided at both sides of the ventilating port, is shifted while being brought into close contact with the ventilating port. CONSTITUTION:The guide rollers 8 and 9 with the same length as the vertical width of the ventilating fan are arranged at the front part of frames 6 and 7 forming an opening and at the same time a drum 10 driven by a motor is installed at the side of the one guide roller 8. The endlessly formed shield curtain 11 is stretched across both the guide rollers 8 and 9 and the drum 10. The shield curtain 11 is composed of the gas impermeable part 12 and the reticulated permeable parts 13 and 14 so as to set the relationship such as l1 l2<=l3, where l1 is the length of the impermeable portion 12, l2 and l3 are the lengths of the permeable parts 13 and 14 respectively. In such a manner as mentioned above, the permeable part 13 is faced to the opening, during ventilation, while the impermeable part 12 is faced to the opening during the time when no ventilation is performed by properly rotating the drum 10. |
