| 摘要 |
In order to produce a self-standing hag in which the two lateral edges of the opposing two side wall sheets are mutually joined directly by heat-fusing, a continuous strip of blank sheet is folded along its longitudinal centerline to be formed with a central folding line as it is fed in the direction of its length, and the strip is then subjected to punching operation to be formed with a series of slots at a predetermined pitch along and adjacent the central folding line, the strip being thereafter folded to be formed with two secondary folding lines on opposite sides of the central folding line in parallel therewith while being fed further. A part of the strip between the secondary folding lines is thereafter depressed transversely inwardly to reverse the folding direction of the central folding line, whereby the slots are drawn inwardly between the folded two halves of the strip. The strip is then subjected to transverse heat-fusing operation in the regions of the slots and is cut successively along transverse lines passing through the slots. |
