Counterweighted backdraft damper blade with improved airflow profile

摘要

A backdraft damper for permitting a flow of air in an outflow direction and preventing the flow of air in a backdraft direction has a frame provided with a transverse opening allowing the passage of air through the frame. One or more blades extend across the frame and are mounted to the frame about a central portion by pivot members, for rotation between open and closed positions. Each blade comprises a blade body having a leading portion upstream of the central portion, the leading portion of the blade body comprising a channel, a trailing portion downstream of the central portion, the trailing portion of the blade having a larger surface area than the leading portion and comprising a seal disposed adjacent to a distal edge of the trailing portion, for sealing against either the leading portion of an adjacent blade or a blade stop projecting from the frame, and a counterweight disposed in the channel, whereby the counterweight balances the blade such that the blade is biased to the closed position by gravity and movable to the open position by the force of air flowing through the frame in the outflow direction.