DAMPER FOR FLOW ADJUSTMENT

PROBLEM TO BE SOLVED: To suppress the occurrence of vibration and noises from a damper more effectively, by securing an indispensable minimum of an air current in the damper whatever sliding position a movable valve plate may be locked in by the fault of an actuator to drive the movable valve, and dispersing the air current passing a fixed valve plate finely, even if the number of small holes in the fixed valve plate is not increased specifically, in a damper for adjustment of flow the which is equipped with a fixed valve plate having many small holes and a movable valve plate having many valve holes corresponding to those small holes and overlapping the fixed valve plate and capable of sliding between the first sliding position and the second sliding position. SOLUTION: Each shape and position of many small holes Hf and many valve holes Hm is set so that it may minimize the total effective aperture of those small holes Hf, lying in the position straddling each small hole Hf that each valve hole Hm corresponds to and a small hole Hf adjacent to it when a movable valve plate Vm is in the second sliding position X2.