Abstract: A flue gate device operated by a solenoid whose energy comes from any outside source, which energy is controlled by the furnace burner control of the furnace to which it is attached. The pull of the solenoid is resisted by a spring which will restore the flue gate to an open position when the solenoid is deenergized or in case of an electrical failure in the flue gate device itself. Through relay switches, the solenoid is deenergized when the furnace burner is energized, and the solenoid is energized when the burner is deenergized, thus enabling a "fail-safe" condition, which enables the furnace to function completely free of the flue gate device.

Abstract: Dampers operable by energization of an electrical circuit or by deenergization thereof to open or close, for control of smoke ventilation in case of a fire. The dampers are held closed, or open, either by a magnet or by a spring. The dampers may be used in ventilation systems of any other type.

Abstract: An isolating valve or damper for the gas-tight closure of a flue or duct, comprising a frame or housing fitted in the flue or duct and a closure member operable between an open position and a closed position in which the member closes the flue or duct, wherein the closure member is a lightweight low inertia body, preferably a cone or a sphere, and wherein the closure member may be moved between its open and closed positions by means of a rapid-acting operator.