Production of bags from a panel of sheet material

In a method for producing bags in succession from an elongate panel of flexible sheet material having parallel longitudinal edges, which method includes:

• advancing the panel in the direction of its length between a shaping tube having a rectangular cross section and extending in the direction of panel advance and a folding box surrounding a portion of the length of the shaping tube, to fold the panel into a tubular structure of rectangular cross section with the longitudinal edges of the panel overlapping;
• joining the longitudinal edges of the panel together to form a longitudinal seam of the tubular structure;
• forming a closed bottom at the leading end of the tubular structure, which is the leading end with respect to the direction of advance of the panel;
• and severing a portion of the tubular structure having such closed bottom to provide a bag which is open at its top and to establish a new leading end of the tubular structure at the plane of severance, the improvement wherein:
• said step of joining the longitudinal edges of the panel together comprises applying a longitudinal bead of adhesive material along one of the longitudinal edges and then pressing the other longitudinal edge against that bead to form the longitudinal seam;
• and
• said step of forming a closed bottom comprises:
• applying adhesive to the outer surface of one narrow side and both wide sides of the tubular structure, while the structure is stationary, to form a transverse adhesive bead having a U-shaped configuration in a plane perpendicular to the length of the tubular structure and located in a region of the tubular structure at which a closed bottom is to be formed;
• and, in sequence, folding a portion of the one narrow side at the leading end of the tubular structure inwardly to lie in a plane perpendicular to the length of the tubular structure, folding a corresponding portion of the other narrow end inwardly to lie in the same plane as the folded portion of the one narrow side, to cause the other narrow side to contact the base of the U-shape defined by the transverse adhesive bead and to be attached thereby to the one narrow side, said steps of folding the narrow sides imparting to the corresponding portions of the wide sides of the tubular structure the form of ears each composed of two layers of sheet material, the layers of each ear being fastened together by a portion of a respective arm of the U-shape defined by the transverse adhesive bead, and folding the ears in succession against the folded narrow side portions in a manner to cause the ears to be fastened together and to the folded narrow side portions by the end portions of the arms of the U-shape defined by the transverse adhesion bead.