HEAT GENERATOR HAVING AUTOMATIC CONTROL FUNCTION FOR PLURAL TEMPERATURES

摘要

A multiple temperature autoregulating heater comprises a laminate of a conductive material, a first ferromagnetic layer on a surface of the conductive material and a second ferromagnetic layer insulated from the first layer. The layers have different Curie temperatures. A switching device is provided to connect one or the other of the layers to be energized from a constant current source. The device autoregulates in the region of the Curie temperature of the selected layer. The conductive material may be non-magnetic (copper) or a low resistivity ferromagnetic material having a Curie temperature well above the Curie temperatures of the autoregulating layers. In the latter case, a thin layer of copper or the like may be interposed between the surface and the conductive ferromagnetic material to further increase conductivity. The device may be provided with multiple ferromagnetic layers to provide multiple different autoregulating temperatures.