Patent ID: 7002117

Claim:
Device for welding a moving packaging material comprising a layer that can be heated by electromagnetic induction and a thermoplastic layer incorporating a welding zone which lies in the direction of movement of the packaging material; the welding device comprising an alternating current generator, a coil for transforming the alternating current into a magnetic field, a ferromagnetic element for channeling the magnetic field lines in a specific direction, the magnetic field being oriented so as to cross the packaging material in order to induce heating of the layer that can be heated by electromagnetic induction; wherein the welding device comprises a set of ferromagnetic elements which are arranged so that the magnetic field lines cross the packaging material in at least two distinct regions located along the welding zone; and wherein a plurality of the ferromagnetic elements are placed alternately close to each side of the packaging material so that each end of a ferromagnetic element is located above or below the end of another ferromagnetic element.