US 4,526,565 AGranted

Method of making flat bottom plastic bag

AssigneeLinear Films, Inc.

InventorsJohn E. Hummel, William E. Baab

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Abstract

A flat bottom plastic film bag includes triangular gusset portions formed by a plurality of parallel heat welds which fuse portions of opposed pleats together and cooperate with a transverse central bottom seam to form a flat bottom bag from a seamed or seamless plastic film tube. The longitudinal side and end walls of the bag are provided with heat embossed corrugations which enhance the freestanding characteristics of the bag and a transverse crease is formed along the fold line between the sidewalls of the bag and the bottom wall to enhance the bottom forming characteristics of the bag when it is snapped from a folded position to an opened position. The bag may be made by an improved process wherein a blown film tube is continuously slit sealed into a plurality of tubes which are reinflated, then collapsed to form opposed double pleat folds, followed by corrugation of the side and end walls of the tube, formation of the transverse crease defining the fold line between the bottom and sidewalls and, finally, formation of the gusset welds, the transverse bottom seal and perforation or cutoff to form the individual bags.

Claims11

Dependent claims

A method of forming a plurality of flat bottom bags from a continuously formed tube of plastic film, said bags being formed such that when opened have opposed longitudinal sidewalls and end walls and a generally rectangular integral bottom wall, said method comprising the steps of:

forming a continuous plastic film tube;
collapsing said tube to a substantially flat band having opposed sidewalls;
passing said tube through means for forming at least one continuous longitudinal band seal;
slitting said tube along said at least one band seal to form at least two continuous tubes each having at least one longitudinal heat sealed seam;
passing said tubes through pleat forming guides wherein said tubes each are folded along opposed longitudinal fold lines to form pairs of opposed longitudinal inwardly folded pleats between said sidewalls;
providing a pair of opposed dies associated with each pair of pleats of a tube and an anvil plate insertable between opposed ones of said pleats of each pair of pleats on each of said tubes;
passing said tubes between said dies while inserting an anvil plate between opposed ones of said pleats of each pair of pleats on each of said tubes and between said dies, and causing said dies to be pressed against said anvil plates to heat seal a portion of each of said sidewalls to said pleats, respectively, along respective diagonal lines extending toward respective ones of said longitudinal fold lines;
heat sealing said sidewalls of each of said tubes along a transverse line at the convergence of respective pairs of diagonal lines with said longitudinal fold lines to form a center seam of said bottom wall and to form opposed triangular gussets of said bottom wall;
and
cutting said tubes adjacent said center seam to define the bottom end of one bag and the top end of another bag formed of each of said tubes.

7 more elements

Dependencies are inferred from the claim text.