| 摘要 |
PURPOSE:To manufacture a shadow mask excellent in a dimension and shape accuracies by providing an annular wrinkle presser by a specified material on the inner side edge part of a die around the knockout for forming in case of manufacturing the shadow mask for a color Braun tube by warm forming a thin steel plate. CONSTITUTION:The peripheral side part of a plate like flat mask 12 on which numerous electron beam passing holes are pierced in regular arrangement is pinched by a blank holder 13 and die 14 opposing each other and a punch 15 and knockout 16 for forming the flat mask 12 in the forming face having a specified curvature are arranged at the inner side thereof. The punch 15 and knockout 16 are surrounded by annular wrinkle pressers 30, 31 and composed by the member having low coefficient of thermal expansion as well, a wrinkle presser 31 is composed by the tool steel excellent in wear resistance at its corner part 32 and each side parts 33, 34 are composed of the material having low coefficient of thermal expansion surface hardened by TiN on a spherical graphite cast iron base material. The flat mask 12 is pressurized by the punch 15 and knockout 16 with this device and the shadow mask excellent in the accuracy of dimension and shape is manufactured.
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