| 摘要 |
PURPOSE:To obtain a fluorescent lamp substituted for an incandescent lamp the appearance of which is deteriorated by adhesion of mercury to a small degree by concentrating adhesion of mercury on a small area at a given position by providing a convex section at the top of the outer tube. CONSTITUTION:Owing to a conic convex section 12 provided at the top of an outer tube 2, its surface area locally increases in the convex section 12 thereby increasing the amount of radiation. Besides radiational heat from heating parts, or inner tubes, per unit surface area of the outer tube 2 decreases resulting in a lower temperature of the convex section 12 than that of its peripheral area. As a result mercury adheres only to the inner surface of the convex section 12. That is to say, since adhesion of mercury develops in a small area at a given position, the adhesion of mercury is seen as a stain with more difficulty than when small-spot-like adhesion of mercury develops in various areas on the inner surface of the outer tube 2. The vicinity of the top of the outer tube 2 generally is the coldest area. Therefore the convex section 12 provided at the top securely becomes the coldest part. |
