Patent attributes
The outer side of a pair of curved parts 3d of a longitudinal annular blank is pressed and energized towards the curved part 3d of the opponent side with a molding outer die 14 of a shaping device 13 to press and widen each curved part 3d to a large curved part of large curvature radius, and a half-finished article 17 is molded, and thereafter, the half-finished article 17 is pressed and widened by cooperative operation of a finishing inner die of the shaping device and a window part of a perfect circle functioning as an outer die to manufacture a ring-shaped member. Therefore, a yield rate or a percentage of the weight of the ring-shaped member with respect to the weight of the raw material and the yield rate or the percentage of the ring-shaped member with respect to the blank can be improved, and the cost can be reduced.
