Method and device for checking for double layers in sheet processing

摘要

The invention relates to a method and a device for checking for double layers in automatic sheet processing. It is the aim of the invention to prevent double and multiple layers from being processed. The invention achieves the object of improving the checking reliability of previous capacitive devices, particularly of eliminating the interfering influence of machine vibrations. The essence of the invention consists in that when sheets are supplied in scale-like overlap, sheet overlap boundaries are scanned by means of two high-frequency-fed plate-shaped sensing capacitors, the high-frequency pulses are amplified and rectified with reference to phase, one of two storage capacitors is charged up in proportion to pulse amplitude depending on the pulse polarity and their voltage sum is evaluated by a threshold switch. The sensing capacitors, which are in each case mechanically coupled in pairs, are arranged behind one another in the transport direction so that the overlap boundaries scanned in each case pass through the sensing capacitors at the minimum distance of one capacitor plate length. The invention can be used in printing and packaging machines. Figure 1 shows the invention most characteristically. <IMAGE>