| 摘要 |
PROBLEM TO BE SOLVED: To provide a mandrel for bending of a bellow tube used for bending the bellow tube having a bellow-shaped cross section in the direction orthogonal to the axis of an inner tube. SOLUTION: In the mandrel for bending, which has plural mandrel pieces 11 and is connected in the same center axial line in a bendable and adjoined state, these mandrel pieces 11 are inserted into a bellow tube having the bellow- shaped inner periphery cross section of an inner tube in the direction orthogonal to the axis and have the outer periphery of the bellow shape roughly same as the bellow shape of the bellow tube. The outer periphery cross sectional shape in the direction orthogonal to the axis of the mandrel pieces of the mandrel is made to the bellow shape roughly same as the bellow shape of an inner periphery cross sectional shape of an inner tube in the direction orthogonal to the axis of the bellow tube, thereby the mandrel pieces 11 are inserted/fitted into the inside of the bellow tube, further in bending, the cross sectional shape of the whole working part of the inner tube having a bellow shape is maintained.
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