| 摘要 |
PURPOSE:To easily finish a spiral forming body in a necessary shape with high accuracy by passing the outer circumferential part of a spiral preforming body through a shaping groove by setting properly the position in the axial line direction of the >=three pieces shaping rolls having shaping grooves and the holding axial diameter. CONSTITUTION:The spiral preforming body 1' progressing with revolving around a holding shaft 27 is shaped with the pitch being enlarged by passing in order through the shaping groove 28a of 1st-3rd forming rolls 28, 28', 28'' at its outer circumferential part. At this time the inner diameter of the preforming body 1' is deformed with its diameter contraction with the pitch being enlarged and its deformation amt. is regulated constantly by the circumferential face of the holding shaft 27. The spiral preforming body 1' can therefore be shaped in the necessary spiral forming body 1'' by adequately setting the interval in the axial line direction of the 1st-3rd shaping rolls 28, 28', 28'' and the outer diameter of the holding shaft 27.
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