Patent ID: 8901817

Claim:
A metal halide lamp with a ceramic discharge tube comprising: a ceramic discharge tube having a discharge cavity and two electrodes, a filler is disposed in the discharge cavity; the ceramic discharge tube is structured as a main discharge tube having two ceramic capillary tubes respectively located at two ends of the main discharge tube, the two electrodes are respectively enwrap in the two ceramic capillary tubes and extend into the discharge cavity being opposite to each other, outer ends of the two ceramic capillary tubes are sealed; the main discharge tube has a central protuberant part located in middle thereof and two cylindrical parts respectively connected to two ends of the central protuberant part, thereby the discharge cavity formed has a central protuberant part together with two cylindrical parts at two ends respectively, the two electrodes are respectively disposed in inner cavities of the two cylindrical parts, the two cylindrical parts are respectively connected to the two ceramic capillary tubes; an inner diameter of the central protuberant part is larger than the inner diameter of the cylindrical part, and the distance between the two electrodes is larger than a maximum inner diameter of the central protuberant part; a distance A between two ends of the central protuberant part, a distance B between two ends of the main discharge tube, an inner diameter C of the ceramic capillary tube, an inner diameter D of the cylindrical part, a maximum inner diameter E of the central protuberant part, and a distance L between the two heads of the electrodes satisfy the following relations: 0.2<A: B<1, 0.3<D: E<1, and 0.2<E: L<1.