Patent ID: 7510515

Claim:
A method for manufacturing a packaging bag, comprising the steps of: (a) continuously feeding in a longitudinal direction a single strip of plastic film material for a main bag body extending in said longitudinal direction, said single strip having opposite half portions between which a longitudinal central line of said single strip exists, said single strip having a longitudinally-extending area, said longitudinally-extending area including said longitudinal central line for forming a bottom of said main bag body; (b) continuously feeding in said longitudinal direction a pair of strips of thin sheet material for a framework member on a surface of said single strip in predetermined positions on the respective opposite half portions of the single strip, said predetermined positions excluding said longitudinally-extending area such that the bottom of the bag body is free from the framework member; (c) bonding said pair of strips for the framework member to said single strip for the main bag body in respective opposite half portions thereof; (d) folding said single strip for the main bag body with said pair of strips for the framework member in two along said longitudinal central line of said single strip for the main bag body to bring one of said opposite half portions close to another of said opposite half portions such that said pair of strips for the framework member are in an inside of said folded composite strip; (e) thermally bonding said folded composite strip in a direction perpendicular to said longitudinal direction by predetermined intervals to form heat-sealed portions; (f) cutting each of said heat-sealed portions in two in a direction perpendicular to the longitudinal direction of said folded composite strip, and (g) prior to said step (b), forming bending facilitation portions on each of said pair of strips for the framework member, said bending facilitation portions extending in a direction perpendicular to said longitudinal direction, thereby continuously manufacturing a plurality of packaging bags each of which comprises the main bag body and the framework member, which is foldable/unfoldable together with said main bag body, to enable said framework member and said main bag body to be shifted between a generally flat collapsed state and an expanded state.