Flap for air flow control in vehicle heating and cooling systems

A flap for controlling the flow of air in a duct, and particularly in a heater or air conditioner for a motor vehicle, said flap having a peripheral edge being formed by two substantially identical, half-flaps stamped from a sheet of light material having a thickness of less than about 0.6 mm, the half-flaps being joined together in face-to-face relation, each of said half-flaps having a plurality of outwardly projecting hollow stiffener ribs disposed opposite from each other and having rib interiors facing each other when the two are joined forming box section channels, the ribs in each half-flap including longitudinal, transverse, and diagonal rib portions all being in contiguous relation with each other, a duct sealing ring of resiliently deformable material, molded over the peripheral edge of the flap, and an end piece fixed between the mating half-flaps on at least one end of the flap when joined and serving as a stub-axle about which the flap may pivot.