| 摘要 |
PURPOSE:To make a fitted state of a cover exact by forming a ring by welding both ends of a tape material of a prescribed length, curving its one end edge to the inside as a U-shaped section, and subsequently, bending it by providing a gap a little against the inside wall. CONSTITUTION:A tape material cut to a prescribed length is formed in a circular shape, and subsequently, by butting both ends and welding them, a ring 2 is formed. As for a die groove 4a of a upper die 4, arc-shaped recessed grooves 4b, 4c whose curvature is smaller than that of a projecting bar 3a of a lower die 3 are provided continuously. When the upper die 4 descends to the lower die 3, first of all, the upper end edge side of the ring 2 on the die lower 3 rises by the arc-shaped groove 4b of the outside circumferential side. Subsequently, a curved section is formed against the projecting bar 3a of the lower die 3 by the groove 4c. Also, when the ring 2 is fitted to a lower die 6, and formed by a upper die 7 having a die groove 7a, the lower edge of a U-shaped section is formed under the curved section. According to this mechanism, a fitted state of a cover becomes exact and strong. |
