Process and device for positioning a sealing jaw

摘要

A first welding plate(1) moves either around a closed track(4) or a linear path and in the welding position lies opposite a support or a second welding plate(6). Two films forming a tubular film are pressed together between the sealing faces(30) of the welding plates by a drive mechanism. The gap(a) between the sealing faces is set by a control unit for the drive mechanism. Gap dimensions are always less than or equal to total thickness of the two film layers lying on each other. When welding plates(1,6) move along a linear path the gap is set by the control unit with the tubular film stationary and welding plates in contact with the film. When the welding plates move around closed tracks(4) the plates move along a straight section(5) with the film during the welding stage and the gap(a) is set by the control unit. The gap may remain constant or vary during the welding stage. Prior to welding the distance(a) can be set to a value equal to or greater than the thickness of both film layers to permit preheating. The gap can then be reduced to exert sealing force. An independent claim is included for a packaging machine, in particular a vertical tubular bag production machine with an electromagnetic linear drive. The drive works on the principle of a suspended railway and comprises a first part and a second part moving relative to the first to vary the gap, which is determined by each position of the moving second part relative to the first part.