Patent ID: 8308881

Claim:
A method for creating a welding force and/or a welding pressure for a welding jaw, in particular a welding jaw of a cross-sealing station ( 2 ) of a vertical tubular bag machine, wherein the welding jaw is moved back and forth along a linear path or is moved along a closed path to strike a resistance, in particular a second welding jaw moving in the opposite direction, wherein a tubular film is compressed between the resistance and at least one of the sealing surfaces of the welding jaws to weld the tubular film by means of ultrasonic vibrations applied to the tubular film via the sealing surface at an applied pressure in a sealing plane under a sealing force (Fs) within a sealing time (ts), and wherein at least one drive is provided to move the welding jaws back and forth in a direction normal to the surface of the resistance in order to perform the welding operation in a stationary position or along an effective sealing path (Zseff) within the sealing time (ts), and wherein the sealing force (Fs) or a sealing parameter which correlates with the sealing force (Fs), in particular the sealing pressure or the drive power of the drive, is predetermined by a control unit during the sealing time (ts), such that the sealing force (Fs) runs along a sealing force curve within the sealing time (ts), wherein the sealing force curve has a first relative sealing force maximum with a sealing force (Fs 1 ), and has at least one second relative sealing force maximum with a sealing force (Fs 2 ), such that the sealing force (Fs 1 ) at the first sealing force maximum is higher than the sealing force (Fs 2 ) at the second sealing force maximum.