Abstract: A proportioning air diffuser system, and an air diffuser therefor, for venting air from a dynamic plenum having areas of relatively greater and lesser static pressure. Each diffuser has a plurality of selectively adjustable vent openings, and a corresponding plurality of air extractors extending into the plenum to divert air through the diffuser. The effective venting area is selectively adjustable, but only within limits that prevent the diffusers from being completely closed. The diffusers are distributed along the plenum, with their effective vent areas progressively increasing from plenum areas of greater to areas of lesser static pressure. The volumetric rate of air flow through the diffusers can thereby be balanced.In a preferred embodiment, two plates having alignable vent openings are positioned over each other. One of the plates is slidable over the other, thereby functioning as a damper to control the alignment between plate vent openings, and thus the effective vent area.

Abstract: A jet pair weir gate is provided in an air diffuser outlet and includes two pairs of nested jet weir members, each member having a generally U-shaped channel configuration consisting of an imperforate web portion and two flange portions. Each pair of members in both laterally expansible and laterally moveable across the outlet width to cooperate with each other in providing selectable air flow patterns through the outlet. In a prefered embodiment, the medial flange of each pair of jet weir members is provided with an extended length serving as a control surface, each adjacent flanges together acting as an air nozzle to focus a jet flow of air therebetween.