Patent ID: 6774566
Filing Date: 2004-08-10
Classification: H01J

Abstract:
A luminaire, comprising:a luminaire main-body; a high pressure discharge lamp with a rated lamp wattage equal to or less than 50 W, which is mounted on the luminaire main-body; and a lighting circuit for driving the high pressure discharge lamp, at a rated lighting frequency in the range of 15 to 30 kHz or the range of 40 to 50 kHz., the lamp including: a light-transmissive ceramic discharge vessel having a swollen portion defining a discharge space and a pair of slender cylindrical portions formed in integral with the swollen portion and communicating with the swollen portion at opposite ends of the swollen portion, wherein the inner surface of the boundary portion between the swollen portion and the each slender cylindrical portion defines a continuous curved surface; a pair of electrodes which penetrate the slender cylindrical portions of the light-transmissive ceramic discharge vessel and having distal ends which lie in the swollen portion of the light-transmissive ceramic discharge vessel; lead-conductors connected to the proximal ends of the electrodes, sealed in the light-transmissive ceramic discharge vessel at least at their mid-portions and exposing outside from the light-transmissive ceramic discharge vessel at their proximal ends; and a filling filled in the light-transmissive ceramic discharge vessel, wherein the inner surface of the swollen portion of the light-transmissive ceramic discharge vessel has an almost spherical shape, wherein the wall-thickness ratio Tmin/Tmax of the minimum wall-thickness Tmin and the maximum wall-thickness Tmax of the light-transmissive ceramic discharge vessel is equal to or less than 0.75, wherein the outer surface of the boundary portion between the swollen portion and the each slender cylindrical portion defines a continuous concave surface, wherein the inner diameter D of the swollen portion and the curvature radius R of the concave outer surface around the boundary portion between the swollen portion and the slender cylindrical portion satisfies a following equation 0.1&lE;R/D&lE;1.5.