US 7,405,577 B2Granted

Apparatus and method for distinguishing between flat objects

AssigneeHeidelberger Druckmaschinen AG

InventorsStephan Limper, Volker Haushahn

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Abstract

An apparatus and a method for detecting the material of a surface of flat objects on a stack, in particular of objects individually separated from one another in the stack by interlayers, preferably of printing plates. The object is to reliably detect the material of the surface of the object that was taken from the stack before it is provided for further processing. The object is achieved by a sensor apparatus that carries out a measurement of the electrical resistance in the region of the object surface to be determined. For this purpose, contact is made between the surface and sensor electrodes, and a measuring current is conducted through the surface. On the basis of the current intensity determined, a distinction is made as to the material of which the object surface is formed.

Claims5

Dependent claims

A method for detecting a material of a surface of a flat object on a stack of flat objects, the flat object being printing plates, which are separated by interlayers, the method which comprises the steps of:

using sensor electrodes resting on the surface of the flat object and connected to sensor electronics for conducting a measuring current through the surface of the flat object;
varying a frequency of the measuring current using a controllable frequency generator;
carrying out a plurality of measurements at different frequencies;
distinguishing a surface material by depending on the frequency of the voltage which is applied to the sensor electrodes;
evaluating measuring voltages determined from the plurality of measurements to detect the material of the surface;
and
distinguishing between an exposure layer of the printing plates, the interlayers, and a rear of the printing plates before providing the printing plates for further processing.

4 more elements

Dependencies are inferred from the claim text.