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: 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 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 vent control arrangement for energy conservation having bimetallic damper elements mounted in a draft hood which forms an integral part of the heating apparatus. The bimetallic elements open and close the flow passage for vent gases from the combustion apparatus in response to temperature change. The vent control arrangement is designed for minimum resistance to the flow of vent gases when installed in the integral draft hood. A design without friction surfaces and without transfer of movements or signals between components is used. Opening time is minimized by closeness to the heat source and in one embodiment by alternate bimetal reeds of different initial tension, in other embodiments by alternate orientation, or by different flexivity of alternate bimetal reeds.

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.

Abstract: The combustion gases of a burner in a heating furnace are discharged to a vent through a draft hood having three ports. The first and second ports communicate with the furnace and the vent respectively and define a first flow path for combustion gases through the chamber of the hood. The third port is open to the ambient atmosphere and defines a second flow path for dilution air through the chamber. Separate temperature responsive, bimetallic elements sense the temperatures in the two paths and cause a vent damper to be moved toward and away from a position in which it closes the second port in response to the sensed temperatures to minimize the flow of dilution air. In a modified embodiment the draft hood is vertically elongate with the bimetallic elements positioned in a zone filling with hot products of combustion for minimizing the flow of dilution air and minimizing spillage of products of combustion during start-up and sudden changes in draft.