GB1067881A - Thermoplastic bag - Google Patents

Abstract

1,067,881. Block bottom bags. UNION CARBIDE CORPORATION. Oct. 22, 1963 [Nov. 9, 1962; May 15, 1963], No. 41620/63. Heading B8K. The heat-sealed block bottom of a thermoplastic bag includes a separate membrane 16 of thermoplastic film heat-sealed in overlapping relation to infolded portions or tabs on each of one pair of opposed side walls of the bag, and either the membrane is heat-sealed to at least one of the other pair of side walls or to a flap thereon, or there are flaps on said other pair of side walls which flaps are inwardly folded and heat-sealed to each other. In one embodiment the bag bottom comprises side flaps 11, 12 and end tabs 13, 14 formed by slitting a tubular blank (Fig. 1, not shown), and these are infolded and outfolded respectively against a split platen 15 as in Fig. 2. The membrane 16 is then applied under the tabs 13, 14 and heat-sealed thereto and to the bag walls adjacent flaps 11, 12 by seals 17-20. Flaps 11, 12 are folded over and sealed longitudinally to provide a handhold. Side flaps 11, 12 may be dispensed with or made just large enough to fold over seals 19 and 20. Alternatively seals 19 and 20 may be eliminated and the flaps, which in this case overlap fully are sealed across their side edges (Fig. 5a, not shown). In another embodiment, tabs 13, 14 cover more of the bag bottom and the membrane 16 is smaller. In a further embodiment, Fig. 6, tabs 13, 14 are cut out, and triangular extensions on the membrane 16 are sealed at 61 and 62 to the bag walls. In any embodiment the top of the bag may be closed in a similar manner to the bottom and may include a membrane which has a tubular extension forming a valve. If no valve member is included the top of the bag is closed after filling by tape, sewing, or adhesive.