Patent ID: 7385702

Claim:
Process for controlling the integrity of planar substrates, such as sheets of paper, characterised by the following steps: providing a first trigger at a selected first location along the direction of displacement of the substrate for detecting the passage of an edge of the substrate at said first location; providing a second trigger at a selected second location disposed downstream of said first trigger along the direction of displacement of the substrate for detecting the passage of an edge of the substrate at said second location; providing at least a first checkpoint detector at a selected third location disposed between said first and second triggers along the direction of displacement of the substrate, said at least first checkpoint detector being adapted to detect the passage of said edge of the substrate at a selected place along said edge which is different than the place at which said first and second triggers are adapted to detect the passage of said edge; detecting the passage of said edge of the substrate at said selected locations by means of said first trigger, said at least first checkpoint detector and said second trigger; controlling whether the passage of said edge of the substrate was detected by said at least first checkpoint detector after detection by said first trigger and before detection by said second trigger; and generating an integrity check failed message in case the passage of said edge of the substrate was not detected by said at least first checkpoint detector after detection by said first trigger and before detection by said second trigger.