LIGHT ALTERATION THERMOSTAT
Original Publication Date: 1985-Aug-31
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
In an electrophotographic printing machine, it is frequently necessary to control the temperature of heated rollers. More particularly, the fuser roller used to permanently affix the toner powder image to the copy sheet requires that its temperature be maintained within a prescribed bandwidth. This may be achieved by utilizing a temperature sensitive paper mounted to the exterior circumferential surface of the fuser roller. The light source directs light rays onto the surface of the temperature sensitive paper. A light detector measures the intensity of the light rays reflected from the temperature sensitive paper. By way of example, the light source may be a light emitting diode and the light detector a phototransistor. When the phototransistor indicates that the color of the temperature sensitive paper is white, the fuser roller is below the desired temperature. Alternatively, when the phototransistor indicates that the temperature sensitive paper is black, the fuser roller is above the desired temperature. The color change of the temperature sensitive paper is non-reversible. Once the paper has changed color, it must be replaced with a new temperature sensitive paper.