| 摘要 |
PURPOSE:To prevent any increase in starting voltage which might be caused as the lighting time increases by winding a tungsten wire on which thorium oxide is sintered around a tungsten bar on which thorium oxide is sintered. CONSTITUTION:A spiral groove 5 is provided on the surface of a tungsten bar 3, and thorium oxide is sintered in the groove 5. Next a tungsten wire 4 on which thorium oxide is sintered is wound around the tungsten bar 3 to make a main electrode 1. The thus made main electrode 1 is combined with an auxiliary electrode 2 made of a tungsten bar on which thorium oxide is sintered, thereby constituting an electrode for a high pressure metallic vapor electric-discharge lamp. Owing to the above constitution, glow discharge between the main electrode 1 and the auxiliary electrode 2 as well as that between main electrodes 1 are facilitated. Besides, since thorium oxide is sintered in the groove 5 of the tungsten bar 5, any scattering of the thorium oxide is prevented and almost no increase in starting voltage is caused as the lighting time increases, thereby securing stable electric discharge. |
