Methods and systems for preparing flat-bottom thermoplastic sack

A method of continuously preparing an at least substantially flat, rectangular-bottom, thermoplastic film sack comprising:

• (a) forming a tube of thermoplastic film having two oppositely disposed, parallel gussets;
• (b) forming two pairs of diagonal sealed seams over the portions of the tube width corresponding to the gussets along lines diagonal to the length of the tube, the seal pair of opposite sides being at an angle to one another and the seams of each pair being in registration with one another;
• (c) forming a transverse sealed seam across said tube along a line which includes the inboard ends of said pairs of diagonal seams, thereby forming four double film triangular regions bound by said seams, said transverse seam, and the side edges of the tube, said transverse sealed seam simultaneously defining a top seal and bottom seal, respectively, for adjacent sacks formed from said tube;
• (d) collecting the resulting structure in a stack;
• (e) removing the four double film triangular regions;
• and
• (f) continuously removing a portion of said tube corresponding to the upper region of each individual sack for forming double-film loop handles and sack mount opening at the end opposite from said bottom seal of each sack.