| 摘要 |
A former for forming an elongated planar bag-making material into a tubular form is composed of a hollow cylindrical tubular part and a shoulder part which has a planar guide section and is connected to the tubular part along a connecting line surrounding the tubular part. Both the tubular and shoulder parts are formed by cutting a tube-forming piece and a shoulder-forming piece from a flat blank sheet in appropriate shapes and bending these pieces into the shapes of the tubular and shoulder parts. The connecting line is designed such that the angle between its tangent and the axial direction of the tubular part changes at a constant rate. Portions of the edges of the tube-forming and shoulder-forming pieces may be in a shape of a parabola or a hyperbolic function curve, and these pieces are obtained by making a numerical control program from the desired shapes of the curve and controlling a laser cutter by the program to cut a blank sheet in the desired shapes.
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