Patent ID: 6359447
Filing Date: 2002-03-19
Classification: B31B,G01M

Abstract:
A control unit for checking the integrity of tear-off closing devices applied to openings in a packaging material strip for forming aseptic packages of pourable food products, wherein the packaging material strip has a first face for defining an inside of a package, a second face opposite the first face, and a multi-layer structure comprising at least one electrically conductive sheet of barrier material disposed between layers of heat-seal plastic material, and wherein the tear-off closing devices each comprise a sheet patch element made of heat-seal plastic material and applied to the first face of the packaging material strip to cover a respective one of the openings, and a tear-off tongue made of heat-seal plastic material and applied to the second face of the packaging material strip and sealed to the sheet patch element through the respective one of the openings, the control unit comprising:first and second idle rollers a) having parallel rotational axes and b) arranged to cooperate respectively with the first and second faces of the packaging material strip at the patch elements and the tongues, the first idle roller having an electrically conductive outer surface; a third idle roller a) having an electrically conductive outer surface connected to ground potential and b) having a rotational axis perpendicular to the rotational axes of the first and second idle rollers and c) arranged to contact the at least one electrically conductive sheet of barrier material at a peripheral edge of the packaging material strip; and a detecting circuit connected between an operating electric potential and the electrically conductive outer surface of the first idle roller, to detect an electric current flow between the first and third idle rollers, the detecting circuit being arranged to a) detect an absence or presence of at least one microhole in one of the patch elements when a portion of the packaging material strip including the one of the patch elements is between the first and second idle rollers, based on the detected electric current flow between the first and third rollers, and b) output a signal indicating the detected absence or presence of at least one microhole in the one of the patch elements.