Elektrische Waermebehandlung zur Versiegelung von Kartons od.dgl.

摘要

1,212,877. Seaming non-metallic sheet material. CONTINENTAL CAN CO. Inc. 28 Dec., 1967 [28 Dec., 1966], No. 58777/67. Heading B5K. [Also in Divisions B8 and H5] One side of an electrically non-conducting material 14 is heat sealed to another surface by a heat sealable material by applying at least one resistive heating element 10 to the one side of the material 14 and applying a high frequency alternating voltage to the other side of the material 14 to produce a flow of alternating current in the element 10 by capacitive coupling to heat the one side by Joulean heating. As shown in Fig. 1, the element 10 is fixed to a substrate layer 12 secured to the non- conductive layer 14 and is heated by placing the layer 14 adjacent to electrodes 16, 18 positioned to apply the tangential portion of an electric field generated therebetween to the element 10. The method is applicable to sealing frozen food cartons which are imprinted, in the regions to be sealed, with heating elements comprising electro-conductive ink, the conductive material being carbon, aluminium, silver, platinum, gold, nickel, tin or copper. The heating elements are arranged in any of the patterns shown in Fig. 2 and are covered with polyethylene or a heat sealable wax, e.g. an ethylene vinyl acetateparaffin blend. A carton 34, Fig. 7, provided with conductive lines 101 is moved past a pair of etched comb-like electrodes 221, 241 whose individual teeth are intermeshed and which are embedded in a polystyrene block 26 and coated with a polystyrene sheet 28. In Fig. 9, filled cartons 34 are fed by a conveyer 40 past electrode structures 36, 38..to seal the side flaps and then past chill rails 42, 44 to cool the seals. The front flap of the carton is sealed by subsequently moving it past a similar electrode structure and chill rail. The flaps of milk cartons (45), Fig. 10 (not shown) having conductive lines (46) thereon, are closed by cams 50, are sealed by passage between electrode structures (52), (54) and are cooled by chill rails (56), (58).