Device for the heat-sealing of thermoplastic material or paper material coated with thermoplastics

A device for heat sealing at least two layers of a thermoplastic material comprising a metal body having at least two substantially parallel side walls, a first metal wall connected to said side walls, a second metal wall connected to said first wall substantially equidistant from said side walls, a coaxial cable having a central conductor, a shield conductor, said central conductor being connected to said second wall, and shield conductor being connected to one of said side walls and means connecting said coaxial cable to a high frequency generator and a metal yoke connected to and spaced from said side walls to provide a space therebetween for the passage of a web of material.