Flow control unit for air distribution system

Abstract

The flow control unit includes a shell or housing defining a flow passage and a damper assembly disposed in the housing for controlling the volume of air flowing through the flow passage. The damper assembly includes a pivotally mounted damper blade which is partially surrounded by a pair of perforated members, one located upstream and the other located downstream of the damper blade pivot axis. Each of the perforated members have an arcuate cross-sectional shape and is disposed in close proximity to the travel path of one of the outer edges of the damper blade. The perforate members preferably have an open edge spaced from a longitudinal plane extending through the damper blade pivot axis. During initial damper blade travel from the closed position toward the open position, substantially all of the air flows through the perforations of the perforate members. During subsequent damper blade travel as the damper blade approaches the fully open position, an open flow passage exists between the damper blade and the open edges of the perforate members. The open edges of the perforate members preferably extend at an angle to the above plane so that the flow area of the open flow passage gradually increases as the damper blade approaches the fully open position.