Abstract: A thermally controlled damper construction for a gas fired combustion apparatus such as a furnace or the like is described. A damper is pivotally mounted within the stack or flue of the combustion apparatus for pivotal movement from a closed position, wherein the damper is located at an acute angle with respect to the axis of the stack, to a full open position. One edge of the damper is recessed to provide a vent opening between the damper and the stack to permit the venting of gases generated by operation of the pilot light during periods when the furnace is not operating. The damper is pivotally moved between its closed and open positions by a bi-metallic thermally responsive element which is located upstream of the damper and which is connected to the damper by means of a linkage. The linkage includes means for permitting the unrestrained rotational movement of the bi-metallic element after the damper is in its position thereby preventing stressing of the thermally responsive element at high temperatures.

Abstract: A thermally controlled damper construction for a gas fired combustion apparatus, such as a furnace. The damper has a generally eliptical shape and is mounted on a shaft in the stack or flue for pivotal movement from a closed position, where the damper is located at an angle of approximately 45.degree. with respect to the axis of the stack, to a full open position. One edge of the damper is recessed to provide a vent opening between the damper and the stack and permit venting of gases generated by operation of the pilot light during periods when the furnace is not operating. The damper is moved between the closed and open positions by a bi-metallic element which is located upstream of the damper and connected to the damper by a linkage. When the furnace is operated, the increase in flue temperature will operate the bi-metallic element to move the damper to the open position.