Thermal fuse for fluorescent lamps

Abstract

A fluorescent lamp thermal fuse arrangement is disclosed. The arrangement in a preferred embodiment comprises a fluorescent glass tube lamp, a thermal fuse wrapped externally around an end of the lamp, electrically insulated mechanical means, lead portions of the thermal fuse and strain relief, and a thermally and electrically insulating protective cover placed over the thermal fuse to concentrate heat around the fuse and to electrically isolate the lamp end from the surrounding environment. The lamp has a maximum normal operating temperature, a coating of emissive material on a cathode of the lamp, a plurality of lamp cathode leads, and a termination electrically connected to a fluorescent lamp power source. The thermal fuse is electrically connected in series between at least one lamp cathode lead and the termination. The protective cover provides electrical insulation to the surrounding environment and a small space for melted fuse material to flow regardless of lamp orientation. A strain relief is preferably provided at a point of exit of the termination from the protective cover. In operation, when the temperature of the lamp end rises above the maximum normal operating temperature of the lamp, the fuse material melts and breaks the electrical circuit to the lamp.