Abstract: In a bimetal-actuated damper a loop-shaped bimetal element engages a damper element. One end of the loop is fixedly fastened while the other end of the loop is movably connected with the damper element. This improves temperature-dependent response and sensitivity of the damper and prevents damage from overheating or permanent change of operating characteristics.

Abstract: In an exhaust gas duct from a furnace a ventilation opening with a ventilation flap is openable in chronological conjunction with the cut-off of the furnace and it is closable in chronological conjunction with the switching on of the furnace. The ventilation opening is formed by a draft-limiter opening located downstream from the furnace and the ventilation flap is formed by a draft-limiter flap. During a pause in furnace operation, the draft-limiter flap is held in an open position independently of the pressure difference prevailing at the draft-limiter flap. One opening and one flap are eliminated. The draft-limiter flap provides the ventilation function as well as the draft-limiter function. If necessary, it can be installed in a small space together with an exhaust gas flap.

Abstract: A draft limiting device for controlling the draft in a flue gas passage, includes a flap which is supported on a swing shaft in a secondary air inlet for swiveling movement between a closed position, at which the flap extends in a substantially vertical plane to block entry of air from a room into the secondary air inlet, and a fully open position at which the flap is displaced a certain angle about the axis of the swing shaft to admit air through the air inlet to the flue gas passage. A solid, semi-cylindrical member is fixed to the flap so that the center of radius of the member is parallel to the swing shaft axis, and the member extends on diametrically opposite sides of the swing shaft axis. The member thereby provides a restoring moment to the flap as the flap is moved in response to a differential pressure from the closed to the open position. The magnitude of the restoring moment is either constant or decreases as the flap moves in the direction from the closed to the open position.

Abstract: A draft control arrangement for a heating apparatus. The draft control arrangement includes a vent damper comprised of one element formed of a shape memory material and another element form of a thermostat material with the elements arranged for coacting to provide a rapid rate of flow passage opening during an initial phase of temperature rise followed by a rate of flow area opening substantially proportional to further temperature rise.

Abstract: A draft control arrangement for use with a gas-fired heating apparatus. The flow of waste gas through a draft hood of the apparatus is throttled by bimetal element means which responds to temperature change for reducing or enlarging the throttle area. Control means is provided for causing the rate of throttle area change during a certain phase of operation to vary from the rate of throttle area change during other phases of operation.

Abstract: Combustion apparatus having a vent with a damper actuated by an element comprised of a material having a shape memory effect. The element is heated and cooled above and below the deformation temperature for causing the element to deform between its different shapes for changing the position of the damper within the vent. Control means is provided in one embodiment for heating the shape memory element so that it deforms for moving the damper closed during a shutdown mode of the combustion apparatus, and in another embodiment the shape memory element is heated so that it deforms to a shape for holding the damper open during the heating mode of the apparatus.

Abstract: Thermally actuated damper for vents or flues of gas-fired heating appliances having bimetallic slotted blades each of which performs both the sensing and the closing function. In the present invention the slots, which are necessary to enable the bimetal blade to flex in the desired direction, are covered, or eliminated, or substantially reduced for a more complete closure of the damper in the closed position.

Abstract: A shut-off device for installation in the waste gas line from combustion spaces. The device includes a flow-through housing, a shut-off plate mounted in this flow-through housing and adjustable, and a positioning motor arranged on the outside of the flow-through housing for the shut-off plate. The shut-off plate is biased by a spring in a direction toward a first terminal position defined by an abutment and is capable of being adjusted by the positioning motor in a direction toward a second terminal position defined by a second abutment. At least one limit switch is provided for actuation by a control element in the open position of the shut-off plate and serving to initiate operation of combustion spaces arranged upstream from the shut-off device. The positioning motor is a rapidly rotating electric motor having a motor shaft connected with the transmission input of a step down transmission for converting the rotary speed of the motor into a slower speed.

Abstract: A draft control arrangement for use with a gas-fired heating apparatus. The flow of waste gas through a draft hood of the apparatus is throttled by bimetal element means which responds to temperature change for reducing or enlarging the throttle area. Control means is provided for causing the rate of throttle area change during a certain phase of operation to vary from the rate of throttle area change during other phases of operation.

Abstract: A draft control arrangement having bimetallic damper elements mounted in a draft hood and adapted to change shape in response to temperature change to open and close the flow passage for vent gases from a combustion apparatus. The damper elements are positioned in the hood relatively close to the source of hot flue gases to provide faster opening and less tendency for vent gas spillage. When open the damper elements cooperate with stationary walls of the draft hood so that the resulting streamlined passage prevents minimum flow resistance. In certain embodiments the damper elements are arranged to undergo a spreading action during opening movement to achieve a disproportionately large passage for the vent gases during the initial phase of opening. In another embodiment a damper unit is mounted separate from the draft hood and provides the same operating results as the other embodiments.

Abstract: A draft control arrangement having bimetallic damper elements mounted in a draft hood and adapted to change shape in response to temperature change to open and close the flow passage for vent gases from a combustion apparatus. The damper elements are positioned in the hood relatively close to the source of hot flue gases to provide faster opening and less tendency for vent gas spillage. When open the damper elements cooperate with stationary walls of the draft hood so that the resulting streamlined passage presents minimum flow resistance. In certain embodiments the damper elements are arranged to undergo a spreading action during opening movement to achieve a disproportionately large passage for the vent gases during the initial phase of opening. In another embodiment a damper unit is mounted separate from the draft hood and provides the same operating results as the other embodiments.