Koninklijke Philips Corporation N.V.

U.S. Philips Corporation

Willem Van Erk

Paul D Goodell

Hui-Meng Chow

Wouter Edgard Koen Broeckx

Oscar Gerard Stappers

Martin F Willemsen

Arnoldus Henricus Franciscus Maria Toonders

The invention provides a metal halide lamp with a ceramic discharge vessel and two electrodes. The discharge vessel encloses a discharge volume containing an ionisable salt filling. The ionisable salt filling comprises 3.5-82 mol % sodium iodide, 0.5-8.5 mol % thallium iodide, 14-92 mol % calcium iodide, 0.5-5.5 mol % cerium iodide and 0.5-3.5 mol % indium iodide. The mol percentages are relative to the total amount of ionisable salt filling. The lamp is dimmable, at least in a range of 50-100% of nominal intensity, while maintaining its light-technical properties and while not substantially deviating from the black body locus. Further, the lamp has a relatively high efficacy. Further, the lamp can be operated horizontally and vertically, i.e. the lamp is suitable for universal burning.

Metal halide lamp comprising an ionisable salt filling

The high-pressure gas discharge lamp () comprises a lamp vessel () having a wall () which is exposed to a wall load of at least 30 W/cmduring operation of the lamp, and a discharge space () in which a pair of electrodes () is disposed. The discharge space () has a filling which comprises mercury, argon, and halides (not fluorides) of tin and indium, to which filling an alkali metal halide is added, the alkali metal being potassium, rubidium, or cesium, and the halide being chlorine, bromine, or iodine. The high-pressure discharge lamp () according to the invention has an improved resistance against corrosion and crystallization of the quartz glass wall ().

High-pressure gas discharge lamp

The high-pressure discharge lamp ( ) comprises a lamp vessel ( ) having a wall ( ) which is exposed to a wall load of at least 30 W/cm during operation of the lamp, and a discharge space ( ) in which a electrodes ( ) are disposed. The discharge space ( ) has a filling that comprises mercury, argon, and halides (not fluoride) of tin and indium, to which filling an alkali halide is added, the alkali being potassium, rubidium, or cesium, and the halide being chlorine, bromine, or iodine. The high-pressure discharge lamp ( ) according to the invention has an improved resistance to corrosion and to crystallization of the quartz glass wall ( ) because of shielding or spacer means ( ) by which a direct contact between electrode rods ( ) and the wall ( ) of the lamp vessel ( ) is counteracted.

The high-pressure metal halide discharge lamp has tungsten electrodes in a light-transmitting lamp vessel which is closed in a vacuumtight manner. The electrodes comprise an emitter which is distributed throughout their mass and is formed by a first oxide chosen from hafnium oxide and zirconium oxide and by a second oxide chosen from yttrium oxide, lanthanum oxide, cerium oxide and scandium oxide, and are substantially free from thorium oxide. The lamp retains its initial light output to a high degree throughout its life.

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Eindhoven, Netherlands

Willem Van Erk