JPS5490874A - Ring-shaped fluorescent lamp - Google Patents

Abstract

PURPOSE: To provide a ring-shaped fluorescent lamp, in which a mixture of rare gases of argon, xenon and krypton, having a smaller heat loss than argon itself, is used as charge gas, whereby starting of the lamp can be facilitated and a high output of light can be afforded with a relatively low electric power.

CONSTITUTION: A ring-shaped fluorescent lamp of this invention is designed such that outer diameter (d) of bulb 1 is 26W30 mm and outer diameter D of the ring is 215W235 mm. A mixture gas of xenon, krypton and argon is charged in the bulb 1 at 1.5W3.0 mmHg, with the content of xenon and krypton being smaller than 20 % and 50 %, respectively, by the volume ratio. If outer diameter (d) of bulb 1 exceeds 30 mmm, tube current is increased because of low impedance of the charged gas, so that there is aroused a fear of breaking stabilizer. On the other hand, if outer diamether (d) is smaller than 26 mm, energy loss on the tube wall is increased, so that it becomes difficult to make an efficient use of ultraviolet rays and thus output of light is lowered. Further, it results in increasing of starting voltage, so that starting of the lamp becomes difficult, for instance, at a low temperature.

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