| 摘要 |
PURPOSE:To reduce the manufacturing error in the peripheral length of a metallic ring, which is attached around the maximum outer diameter of a cathode- ray tube in order to prevent its explosion, by using two metallic belts having reference convex areas for welding work and reference convex area for bending work to make the metallic ring. CONSTITUTION:A metallic ring 10 is attached around the maximum outer diameter of a cathode ray tube in order to prevent its explosion. It is made by connecting the ends of two belt-like steel plates 11A and 11B by welding before the connected body is formed into a ring. Each steel belt 11 is obtained by punching work and has reference convex areas 13a and 13b for welding work in its ends and a reference convex area 14 for curving work in its center. It is sub- jected to the primary work of pressing before being subjected to the secondary work of bending. The bent steel plates 11 are then subjected to welding work before the welded body is formed into a ring. As a result, variation in the peripheral length of the metallic ring 10 can be reduced by almost completely eliminating the amount of spring back, thereby improving the quality and the productivity of the metallic ring 10.
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