| 摘要 |
PURPOSE:To use an inexpensive circular pipe blank and to easily obtain the necessary elliptical bellows by using a circular pipe blank and after forming a circular bellows by a split die executing a tension work by upper and lower tension dies. CONSTITUTION:Both ends of a pipe blank 1 are subjected to liquid pressure sealing and three units of split dies 11, 16 and 12, 17 and 13, 18 are integrated by the advance and fitted to the outer peripheral part of the pipe blank 1. A circular bellows is formed by approaching the respective slit die by executing bulging among each split die with liquid pressure 20. After removing the liquid pressure 20, the seal holders 4, 5 are retreated to recover an oil. Upper and lower tension dies 23, 24 are passed to the inside of the circular bellows to insert the corrugated parts 23a, 24a of the upper and lower tension dies 23, 24 into the crest part 1a of the bellows. The upper and lower tension dies 23, 24 are fixed to upper and lower tension die supporting plates 23b, 24b by advancing spindles 21a, 22a. After the split dies 11-13, 16-18 being released from the bellows, a tensile load is loaded on the circular bellows by the upper and lower tension dies 23, 24 to exert a plastic deformation and an elliptical bellows 26 is obtd.
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