| 摘要 |
PROBLEM TO BE SOLVED: To form a gusset excellently for a cylindrical film formed in a square cylindrical shape, and having seal ribs at corners.SOLUTION: A gusset forming member 28 for forming a gusset at a cylindrical film F has a chevron shaped push-in piece 32 bent from the center in a vertical direction. A push-in edge 32b of the push-in piece 32 is formed in an arc shape. At a push-in tip of the push-in piece 32, a pair of protruding pieces 36, 36 are provided, vertically apart from each other. At a push-in position, a film Fa in the vicinity of extension base ends of upper and lower seal ribs 10 on a side face of the cylindrical film F is supported by the push-in edge 32b of the push-in piece 32. A sag part of the film is located at a recessed part 42 between both of the protruding pieces 36, 36 provided in the push-in piece 32, at the push-in position. |
