Device for preventing overheating of electrophotographic fixing device

摘要

A thermal fixing device for a xerographic reproducing apparatus includes a thin planar resistance heating element having a low thermal mass and a high coefficient of thermal expansion. The heating element is supported in such manner that one end thereof is free to move linearly under thermal expansion to activate a heater displacement detector comprising a pivotally mounted lever arm having a right angle configuration. One end of the lever arm is received in an opening in the heating element and the other end form a contact of a normally open switch which is adapted to be closed by pivoting of the arm due to expansion of the heating element. Closure of the switch activates a power controller to interrupt the power supply to the heating element.