| 摘要 |
PURPOSE:To prevent crack and misalignment by providing 1st and 2nd end hats with a cylindrical part each, of wall thickness nearly equal to the wire diameter of a filament, and positioning both points where the cylindrical parts of the end hats and the ends of the filament are laser-welded, at opposite sides of the center axis. CONSTITUTION:Wall thickness t1 of a cylindrical part 8b of 1st end hat 8 and wall thickness t2 of a cup member 9b of 2nd end hat 9 are set to both 0.6mm which is nearly equal to the wire diameter phif of a filament 1. Centers of laser- welded points A, B are placed at distances d1 and d2 inward from the opening ends of the respective cylindrical parts, provided that two laser beam-welded points A, B are positioned at opposite sides from the center axis Y of the filament 1, distances d1, d2 are 0.1mm or over, and welded parts of the filament 1 are shadowed by respective cylindrical parts from the laser beam. When the welded parts A, B are exposed to a laser beam under such a construction, the cylindrical part 8b is melted at the welded point A to cover the end of the filament 1.
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