Abstract: A heater for a sheet material comprises an insulating substrate, and a plurality of heating resistor strips formed on the substrate to extend in parallel to each other between first and second common electrodes. At least one of the resistor strips is electrically connected to both of the first and second common electrodes while at least another of the resistor strips is electrically separated from the first common electrode.

Abstract: A heater for a sheet material comprises an insulating substrate and a main resistor strip formed on the substrate. The substrate is further formed with auxiliary resistor strips adjacent to both ends of the main resistor strip. In operation, the main and auxiliary resistor strips are actuated simultaneously for heat generation. As a result, the additional heat generated by the auxiliary resistor strips compensates for higher heat dissipation at both ends of the heater, thereby equalizing the temperature distribution longitudinally of the heater.

Abstract: A heater for heating a moving sheet material by contact therewith is used, for example, in electrophotographic apparatus for fixing toner to printing paper. The heater comprises an insulating substrate formed with a striplike heating element on its upper surface, and a support plate for supporting the substrate. A higher heat preserving property is given to the opposite end portions of the heating element than to a longitudinal intermediate portion thereof to thereby compensate for a temperature reduction at the element end portions and make the heating element uniform in temperature over the entire length thereof.