| 摘要 |
PURPOSE:To hold the outer periphery of a tube stock uniformly and prevent a swing, by holding the outer peripheral wall of the tube stock between a freely rotatable male mold having a concave and convex part along the direction of its circular periphery and an engaging female mold and forming a bellows by pushing the mold of a same shape as the female mold for a swing rest so as to match the push in amount of the female mold. CONSTITUTION:A tube stock 6 is fitted onto a mandrel 1, a part of the outer peripheral wall of the tube stock 6 is placed between a male mold 3 and a female mold 5 and also the concave and convex parts 7a, 8a of the swing rests 7, 8 are contacted to the outer peripheral wall of the tube stock 6. A push in force is added to the female mold 5 in an arrow direction a and the male mold 3 is rotated together with the mandrel 1. Then, a bellows 9 is obtained by forming a hill part 9a and a valley part 9b alternately on the outer peripheral wall of the tube stock 6 by the concave and convex parts 2, 4. In this time, the swing rest molds 7, 8 are pushed in to the arrow direction b matching the push in amount of the female mold 5, the concave and convex parts 7a, 8a engage with the bellows 9 and the swing of the tube stock 6 is prevented by the cooperation of the female mold 5 and the swing rest molds 7, 8. |
