| 摘要 |
PURPOSE:To improve strength and simplify manufacture by molding both legs of a bulb into a U-shape through the connecting part while making the inside shape of the bulb connecting part into a tumbler-shape hole provided with the small diameter part on the joint of both legs. CONSTITUTION:A glass bulb 1 consists of two legs 11 and the connecting part 12. Glass stems 3, wherein electrodes are planted, are sealed on both ends of the bulb 1, while a phosphor layer 13 is formed inside thereof. The part 14 corresponding to the inside of the connecting part 12 is formed into a tumbler-shape hole provided with the small diameter part. Im this way, the strength of the connecting part 12 can be improved. Further, for forming the connecting part 12, two glass tubes 11 having both end openings are held in parallel, being closely jointed, while forming a connecting hole on the spot near the opening ends of the neighboring parts of the tubes 11 with gas burners 4, while subsequently the vicinity of the connecting hole is softened by the other gas burners so that the connecting part may be formed into the U-shape. Further, metal molds 6 softened by heating and divided in two are put on and the bulb inside is pressurized for molding the connecting part having a concave 61 of small diameter. |
