Thermal damper for rectangular flue

A damper assembly for operation between confronting side faces of a flue comprising, in combination, a vane disposed between said side faces and having a width substantially equal to the separation between said side faces, axle means generally perpendicular to said side faces and projecting through the space between said side faces, bimetallic coil means convoluted about said axle means, and means cooperating with said axle means to retain the innermost convolution of said coil means against rotation about said axle means, means affixing said vane to the outermost convolution of said coil means, said vane having first and second wing portions projecting outwardly and oppositely from said coil means, said wing portions disposed generally radially with respect to said axle means and orbited about said axle means in response to changing temperatures of said coil means causing the outermost convolution of said coil means to progress circumferentially about the innermost convolution of said coil means.