| 摘要 |
PURPOSE:To prevent the occurrence of a leak or a crack in time of sealing a cover to the opening part of a luminous envelope, by installing a concave part or a convex part, capable of absorbing a difference in thermal expansion with a material for the luminous envelope, in the cover consisting of a metal material, while welding the cover to the envelope opening part. CONSTITUTION:A metal cover 15 or 15' having a concave part 16 or a convex part 17 is used in this fluorescent lamp. With this method, for example, the concave part 16 installed in the central part of the cover 15' performs its role as a cushion to absorb a difference in thermal expansion at a sealing process between an envelope outer body 2 and the cover 15'. Even in such a case that a convex part 17 is installed in the central part, the same effect can be obtained as well. However, lamp efficiency falls off to a certain degree as compared with that in case of installing the said concave part 16 and in addition, it may be said there is a rather disadvantage in time of being solidified with a ballast. That is to say, the concave part 16 raises the reflection efficiency of light at the opening part of a luminous envelope 1 and yet suitable for housing the ballast inside. |
