Patent ID: 8481898
Filing Date: 2013-07-09
Classification: H05B

Abstract:
1. A heater, comprising: a printed or coated PTC material providing a resistance of 20 to 1500 ohms/sq, the printed or coated PTC material comprising a sharp melting polymer, the resistance of the printed or coated PTC material increasing three to five orders of magnitude at a threshold temperature corresponding to a melting temperature of the sharp melting polymer, the printed or coated PTC material in thermal communication with a heated area, the resistance of the printed or coated PTC material responsive to a temperature of the heated area; and a constant resistance heating material in contact with and in thermal and series electrical communication with the printed or coated PTC material, the printed or coated PTC material having a length in a direction of electric current flow of 10% or less of a length of the constant resistance heating material, wherein the resistance of the printed or coated PTC material is lower than a resistance of the constant resistance heating material below the threshold temperature such that a majority of a voltage drop during heater use occurs across the constant resistance heating material below the threshold temperature, and wherein the resistance of the printed or coated PTC material is higher than the resistance of the constant resistance heating material above the threshold temperature such that a majority of the voltage drop during heater use occurs across the printed or coated PTC material above the threshold temperature.