| 摘要 |
PURPOSE:To prevent the going up of the lamp voltage or the leakage of gas in the tip portion of a lamp by locating the tip portion of a luminous tube on the upper side of the horizontal plane passing through the center of the luminous tube and on either side of and apart from the central cross section passing through the center of both electrode ends when the lamp is lighted in porizontal psition. CONSTITUTION:The tip portion 2 of a luminous tube 1 is provided on a portion 8 mm apart from the center of both electrode ends on one electrode side. In the luminous tube 1 a pair of electrodes 3 connected to outer lead wires 5 through metal foils 4 respectively is provided. The discharge arc 12 is curved upward by the buoyancy. and especially in the central portion between the ends of the electrodes 3 the are 12 is adjacent to the inner wall surface of the luminous tube 1 so that a locally heated high temperature area is produced. But ths tip portion 2 is located on one electrode side of the center of the ends of the electrodes 3, thus the tip portion is located outside of the local high temperature area. Thereby the tip portion can be avoided from the local high temperature area so that the going up of the lamp voltage due to the ejection of water vapor from the tip portion or the leakage of the gas in the tip portion due to the reaction of the sealed metal and the quartz of the luminous tube can be prevented.
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