Zippered bag and method of forming the same

Claim 1

A gusset bag having one end to be formed as a bottom end and another end to be formed as an end opening through which a content packed in the gusset bag is taken out, the gusset bag comprising: a bag body having a tubular structure and composed of a pair of opposing flat portions constituting front and back surface portions of the bag body, said front and back surface portions having respectively two side edges, and two side surface portions connecting the front and back surface portions at both side edges thereof and respectively having lines folded inward which extend along longitudinal direction of the side surface portions an along which the side surface portions are folded inwardly a zipper element mounted on inner surfaces of the flat portions at portions near the end opening of the bag body; and a fused seal portion formed to and near the end opening portion of the bag body to substantially entirely seal the end opening portion said fused seal portion including an end seal portion having two ends and extending substantially along an entire length of the end opening and side seal portions extending from both ends of the end seal portion along the side edges of the flat portions of the bag body, said side seal portions each extending beyond the portions on which the zipper element is mounted, wherein a sealing process is carried out integrally with portions of the side surface portions near the end opening of the bag body, which are once inwardly folded along the folding lines and then drawn out and folded outward from the end opening of the bag body for once opening in the end opening and wherein the zipper element is mounted to the portions near the end opening portion of the bag body between the end opening portion and the once folded and then drawn out side surface portions.