| 摘要 |
PROBLEM TO BE SOLVED: To provide a ventilation damper which is able to close a path by it self utilizing airflow when the airflow of a certain speed is generated by large pressure difference between indoor and outdoor generated to the path, to open the path certainly when the wind speed decreases, to reduce the driving force required to generally force fins directed towards the direction the path opens and to certainly close the path by itself with desired wind speed. SOLUTION: A ventilation damper 1 is provided with a frame 5 in which having a path 4 having an inlet hole 2 and an outlet hole 3, a fin 6 rotatively arranged inside the frame 5 opening and closing the path 4 by the rotation in the direction of R1 and R2, a rotating means rotating forcibly the fin 6 in the direction of R2 to have the fin 6 open and close the path 4 and a resilient means resisting the free rotation in the direction of R2 of the fin 6 heading for the position of closing the path 4, wherein the free rotation in the direction of R2 of the fin 6 heading for the path closing position is allowed when the fin 6 is rotated towards the path opening position.
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