| 摘要 |
PURPOSE:To cut off the effect of air pressure and reduce the manufacturing cost by causing runners to move toward or away from each other by the rotation of a screw rod to change the angle of arms so as to move a cover member up and down. CONSTITUTION:A damper 23 closes off a ventilator opening 1 as the packing 39 is pressed against the flange 46. For ventilation, a screw rod 19 is rotated by a motor 27. As the screw rod 19 rotates, a runner 20 engaged with the clockwise screw thread 28 and a runner 21 engaged with the counterclockwise screw thread 29 move away from each other along the screw thread grooves for the clockwise screw thread 28 and counterclockwise screw thread 29. The ends of arms 25, 26, then, move upward to suspend the damper 23 higher to fully open the damper 23. In order to close the ventilator opening, the screw rod 19 is rotated in a reverse direction.
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