Process and apparatus for register adjustment or maintenance, with automatic initial register adjustment, of a web of preprinted material

A process of register adjustment or maintenance of a continuous printed web of material in a processing station of a machine in which a position pulse train is produced whose relative position with regard to an index pulse, is a measurement of the instantaneous position of a processing element, of said processing station, during each of its cycles a detector signal is picked up from a printed format on the web continuously and which is a function of a difference of characteristic between the material that makes up said web and the printed format on said web that is carried thereon, wherein the signal from the detector is sampled during one of said cycles, in synchronism with the position pulses, and wherein signals which are the result of said sampling are written in a memory, in a numerical form at successive address therein, with a register mark being selected from said memory contents and said that the deviation between a real position and a set point position of the register mark is determined, and from the deviation thus determined, the desired correction is applied to bring the deviation to zero,

• comprising in that, to permit an automatic initial register adjustment and maintenance of register of a preprinted web in an off-line machine, the steps of:
• storing, in the form of a digital sequence, at least one characteristic of the register mark selected, acting on said detected signal;
• continuously sampling the detected signal and writing the results in memory;
• periodically analyzing the contents of the memory to locate in it a sequence of numerical values corresponding best to that determined as a function of the register mark selected, and
• calculating any deviation between the actual position and the set point position of the register mark from a determined address of said sequence and from the position of the processing element associated with it.