| 摘要 |
A method and system for preparing flat bottom thermoplastic sacks comprising process steps and means for forming a tube of thermoplastic film, collapsing said tube while forming two oppositely disposed gussets therein, simultaneously or spatially sequentially opening a gusset fold on each side of said collapsed tube to their full, lay-flat extent; simultaneously or spatially sequentially forming in each of the four gusset folds, a diagonal sealed seam (20) over the portions of the tube width corresponding to the gussets along lines diagonal to the length of the tube so that the ends of the sealed seams of adjacent gusset folds are at least closely spaced or in contact so as to form an angle of at least approximately 90 DEG , returning said gusset folds to their original position so that their seal-pairs are superimposed, forming a transverse sealed seam (24) across the tube along a line which includes the inboard ends of the diagonal seams and forming preweakened transverse lines closely adjacent to said transverse sealed seam or forming a severing line along this line; removing the four double triangular regions (34) bounded by the diagonal seams, the transverse seam and the side edges of the tube; and collecting the resulting structures either while still interconnected or by stacking the severed sacks. The final structure can have handles (38) or it can be handleless. |
