Printing press strip datum mark automatic detector system - uses detectors in geometrical configuration aimed at mark with inclined edge

摘要

The equipment automatically detects a datum mark when adjusting a strip of material passing through a machine, partic. a rotary printing press. The datum mark has a predetermined geometrical shape, with one or more edges inclined to the travel direction, and aimed at the area on which the marks are printed are a number of optical detectors mounted at the corners of a predetermined geometrical figure. An unprinted surface causes them to emit a 'bright' signal, and a printed one a 'dark' signal. A computer combines the signals from the detectors into logic form and determines, taking strip speed into account, one or more specific characteristics. These are compared with that of the datum mark, and when a mark is shown to be present the computer generates a release signal (f) for the alignment error detection equipment. If it is not present, a computer resetting signal is emitted.