Ultrasonic transverse sealing method and device for sealing walls of a packaging material filled with a pourable food product

摘要

An ultrasonic transverse sealing method for sealing the walls (9) of a tube (2) of packaging material filled with a pourable food product and fed along a path (P), and wherein the packaging material has heat-seal plastic material; the method providing for gripping two walls (9) of the tube (2) locally between a first and a second face (17; 21) of respective jaws (3, 4) of a sealing device (1); compressing the walls (9) to a first pressure (P1) along a first portion (15) of the walls (9); subjecting the first portion (15) to ultrasonic vibrations to melt the heat-seal plastic material and seal the walls (9) along the first portion (15); and compressing the walls (9) one against the other and by means of the jaws (3, 4) to a second pressure (P2), lower than the first pressure (P1), along a second portion (28) of the walls (9) adjacent to the first portion (15), so as to form a barrier between the first portion and the food product.