Abstract: A control damper is mounted in a building duct system for closing a control opening through a housing or frame and includes a linkage connected to the housing and to a vane positioned in the control opening and is operative for moving the vane between a flow permitting position and a position closing the control opening. The linkage includes a fusible portion permitting a resilient member to move the vane to the position closing the control opening in the event of temperature above the melting point of the fusible portion. Cooperating latch members are mounted on the housing and on the vane and are moved into vane holding engagement after melting of a fusible portion and movement of the vane to the position closing the control opening through the housing.

Abstract: A folding blade damper comprising a rectangular frame and an assembly of blades hingedly interconnected along longitudinal marginal edges by tubular hinge elements. A spring is interposed between each interconnected pair of blades to resiliently urge the blades from a folded to an unfolded flow blocking position across the frame. The spring comprises a flat member having an arcuate portion generally coaxially of the tubular hinge elements and oppositely extending arms in overlying engagement with adjacent blades with fingers extending over an edge of a respective blade to engage the opposite face thereof and cooperate with the arms to resiliently and removably secure the spring to said blades whereby the arcuate portion is contracted upon folding of said pair of blades and then exerts a torque urging the connected blades to unfolded position.

Abstract: A control damper is mounted in a building duct system for closing a control opening through a housing or frame and includes a linkage connected to the housing and to a vane positioned in the control opening and is operative for moving the vane between a flow permitting position and a position closing the control opening. The linkage includes a fusible portion permitting a resilient member to move the vane to the position closing the control opening in the event of temperature above the melting point of the fusible portion. Cooperating latch members are mounted on the housing and on the vane and are moved into vane holding engagement after melting of a fusible portion and movement of the vane to the position closing the control opening through the housing.