Method and apparatus for heat sealing of multiple layers of a laminate

The invention relates to a method and an apparatus for heat sealing of multiple layers of a laminate from the particular gable top carton can be prepared to receive liquid foods, the laminate having a support layer of electrically non-conductive material, for example cardboard, and a sealant layer of thermoplastic material, for example polyethylene, to comprises at least one surface of the laminate. Another problem is the heat sealing in the high-frequency alternating electric field, when the number of layers of the laminate varies in the seal area. In order to provide a method and an apparatus for heat sealing of multiple layers of a laminate in a high frequency alternating electric field which avoids the problems caused by a too large or too small heat into the to be sealed layers of the laminate, the invention proposes that the alternating electric field in a first portion of the seal portion having a first line of the RF power supply and is produced in at least a second portion of the sealing region with a deviating from the first conduit second power of the RF voltage supply so that a different distribution of heat over the portions of the sealing area is obtained. The different heat distribution in the partial regions allows a specific adjustment to the level specified in the respective regions of heat demand.