Patent GB-528547-A (GB)
Title: Paper and like containers and method of making the same
IPC: B31B50/64
Filed: 1939-05-09
Abstract: 528,547. Paper bags &c. HUMOCO CORPORATION. May 9, 1939, No. 13844. Convention date, Aug. 16, 1938. [Class 94 (ii)] Moisture - proof containers for packaging tobacco &c. are made from laminated blanks comprising a layer of wax-impregnated fibrous material, such as paper, and a layer of foil. Preferably the laminated material is made in web form and subsequently cut into blanks, and may comprise a layer of paper secured to a layer of aluminium foil by an elastic adhesive such as a combination of latex and casein. The layers may be secured together throughout their entire areas, after which the paper is proofed or rendered water resistant by coating its surface with wax and then subjecting the compound material to a baking heat to impregnate the paper. Subsequently the surface of the metal foil is coated with a film of thermoplastic lacquer which serves to protect it from oxidation and provides a surface suitable for receiving printed matter. The fibrous lamina of the web is next striped with a thermoplastic adhesive along areas 7, Figs. 1 and 2, corresponding to the top, bottom, and right-hand margins of container blanks, preferably before the separate blanks are cut from the compound web. Either before or after cutting into blanks the material is embossed or creased to provide a plurality of vertical folding lines A dividing the blank into wide and narrow rectangular portions adapted to form the side walls and also an end tab or section 11. Top and bottom closure sections 12, 13 are formed by transverse creases or grooves B, C, D, and notches 8 are cut in both the vertical edges at the sections 15, 17, Fig. 1. Diagonal creases E and F may also be provided to facilitate the folding of the top and bottom flaps. The top and bottom sections 14, 16 are next folded inwardly along the grooves D on to the sections 15, 17 to form sealing flanges or hems, and an opening-string 22, previously rendered non-absorbent is attached by heat and pressure at the inturned part 22a of the upper edge. The blank thus prepared is folded, with the metal foil 6 outermost, about a mandrel 23, Fig. 13, and the overlapping ends are heat-sealed together, preferably by an electric sealing-iron 30 containing a heating coil 31. As shown the sealing device is associated with folding-mechanism comprising a lower plate 24 for holding a central portion 9 of the blank against the lower face of the mandrel 23, a pair of plates 25 for folding the sides of the blank up against the sides of the mandrel, and members 26, 27 for folding the edge portions into overlapping relation on the top face. To facilitate the extrusion of air from the seam 28 the mandrel is provided with a longitudinally extending groove or channel 39 containing a pressureequalizing pad 40. The imperviousness of the seam is also increased by contouring the face of the iron 30 in such manner as to exert pressure locally over an area bounded by lines a .. d, Fig. 16, the pressure on the area 41 between lines a and b being less than that on the area between lines a and d. The face of the sealing-iron may also be ribbed to produce longitudinal flutes 42 in the central portion of the seam. Subsequently the end of the container at which the opening- string is attached is folded inwardly along the preformed grooves and heat-sealed between a pair of opposed sealing-irons to form a closure seam 43, Fig. 22, which may be simultaneously embossed with transverse grooves 51 to increase its imperviousness and is then folded inwardly to form a flat bottom with side tabs 44 that can be secured on to the side walls 10 either by adhesive or by an applied adhesive stamp or the like.