Patent ID: 7722730

Claim:
A method for heat-sealing windows into folding carton blanks in order to produce liquid-proof folding cartons having film windows comprising the steps: placing the folding carton blanks onto a transport belt and locally fixing the folding carton blanks on the transport belt, placing film pieces that have been cut to measure onto window openings of the folding carton blanks and locally fixing the film pieces on the transport belt, arranging a tail pulley for the transport belt to deflect an area of the transport belt, thereby changing a direction of motion of the transport belt, introducing the folding carton blanks together with the film pieces into a gap between the tail pulley and the transport belt resting thereon, feeding the folding carton blanks and the film pieces through the change of direction of the transport belt by the tail pulley, and after the change of direction of the transport belt, suspending the folding carton blanks with the heat-sealed film pieces from a lower side of the transport belt, continuously heat sealing edges of the film pieces in a liquid-proof manner to the folding carton blanks using at least two heated pressure segments or heat-sealing dies with pressure edges, that are situated on an outer periphery of the tail pulley by pressing the at least two heated pressure segments or heat-sealing dies radially from inward against the transport belt in the area of deflection of the transport belt, thus pressing on the edges of the pieces of film, using suitable devices to synchronize the transport belt with the tail pulley in such a way that the folding carton blanks locally fixed on the transport belt come into contact with the pressure segments or heat sealing dies in the gap between the tail pulley and the transport belt in the area of deflection of the transport belt, and so that pressure edges of the pressure segments are pressed onto the edges of the film pieces with a precise fit, and pressing the transport belt against the tail pulley radially inwardly with the aid of support rollers engaged with the transport belt in the area of deflection of the transport belt.