| 摘要 |
Device for welding a moving packaging material ( 1 ) comprising a layer that can be heated by electro-magnetic induction and a thermoplastic layer incorporating a welding zone ( 2 ) which lies in the direction of movement of the packaging material; the welding device comprising an alternating current generator, a coil ( 3, 5, 6 ) for transforming the alternating current into a magnetic field, a ferromagnetic element ( 7, 8, 10 - 13 ) for channelling the magnetic field lines in a specific direction, the magnetic field being oriented so as to cross the packaging material ( 1 ) in order to induce heating of the layer that can be heated by electromagnetic induction; the welding device being characterized in that it comprises a set of ferromagnetic elements ( 7, 8, 10 - 13, 19 - 21 ) which are arranged so that the magnetic field lines cross the packaging material ( 1 ) in at least two distinct regions ( 14, 16 - 18 ) located along the welding zone ( 2 ).
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