| 摘要 |
PROBLEM TO BE SOLVED: To easily produce a double tube of a metal by winding with inclining a metal band plate on a mandrel, producing an external tube, spirally feeding the external tube and sequentially inserting the external tube onto the outside of an internal tube. SOLUTION: A metal band plate 10 is wound against a rotary shaft of a mandrel by an inclining angle, a guide 4 is set at the position in contact with the end part of the metal band plate 10, the mutual end parts of the width direction of the wound metal band plate 10 are welded continuously with a welding machine 5 and a spiral tube like external tube 1 is produced, and the external tube 1 is inserted sequentially onto the outside face of an internal tube 2 and a double tube of metal is produced. When the end part 1-1 of the external tube 1 is reached to B-B, the internal tube 2 is cut at B-B, the external tube 1 is cut at C-C, the double tube of metal with the length P is taken out. When the inclining angle against the axis of the mandrel is made asθ, the next relation is held neary cosθ=(W/πD) here, W: plate width (mm) of the metal band plate, D: external diameter (mm) of the mandrel,π: ratio of the circumference of a circle to its diameter.
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