Abstract: A guillotine-style door closure system for a furnace comprises a furnace opening with a door frame on a vertical side of the furnace; a furnace door adapted to mate with the frame; a left closing chain mounted, at one end, to the vertical side of the furnace approximate the left jamb and the lintel of the frame, and mounted, at its other end, to a left pin extending from the furnace door approximate the left vertical side of the door, below the vertical centerline of the door and distal from the rear vertical side of the door; and a right closing chain mounted, at one end, to the vertical side of the furnace approximate the right jamb and lintel of the frame, and mounted, at its other end, to a right pin extending from the furnace door approximate the right vertical side, below the vertical centerline and distal from the rear vertical side of the door.

Abstract: An energy-saving closure system is provided for use in preventing needless energy loss. The system employs a pivotal closure adapted to alternately move between the fully open and fully closed portion in a conduit for conveying gases relative to a combustion zone. The closure requires pressure diffentials only for being urged into the open and closed positions such as normally occur in the heating cycle. No energy-consuming, auxiliary apparatus is needed.