| 摘要 |
PURPOSE:To reduce a loss of plasma for improving efficiency by making two U-shaped inner tubes housed inside an outer tube so as to make the parts adjacent to their respective opening parts in the shape of a straight tube while the opening parts are provided on their sides for being opposed. CONSTITUTION:A fluorescent lamp of a duplex construction of inner and outer tubes is formed by housing the U-shaped inner tubes 3 and 3', whose one end each has a seald-in electrode 4 while the other end each is opened, inside a gastight container formed of the outer tube 1 and the outer tube base part 2. And the sections near the opening parts of the inner tubes 3 and 3' are made in the shape of a straight tube for being kept semicircularly closed while heating the tip sides with a burner flame for melting glass of the parts corresponding to the openings and injecting high pressure gas from the other ends for blowing through and forming the opening parts 8 and 8' to make them opposed. Accordingly, a loss of plasma 7 is minimized for reducing deterioration in a luminous flux while the edge parts 9 and 9' are formed by welding thus excluding generation if cracks for preventing damage to the inner tubes. |
