Method and device for the contactless detection of flat objects

Method for the contactless detection of flat objects, such as multilaminated materials like labels adhesively applied to support material, with respect to a presence or absence of said flat objects, said flat objects being placed in a beam path between a transmitter (T) and an associated receiver (R) of a sensor device, wherein a radiation transmitted through the flat objects or the radiation received in the case of an absence of said flat objects by said receiver (R), is received as a measuring signal (UM),

• said measuring signal (UM) is supplied to a following evaluation for generating a corresponding detection signal,
• wherein a characteristic of an input voltage (UE, UM) of said measuring signal (UM) is formed,
• wherein at least one correction characteristic (KK) is supplied to said evaluation, said correction characteristic (KK) transforms the characteristic of the input voltage (UE, UM) of said measuring signal (UM) from said receiver (R) as a function of a weight per unit area of said flat objects to a target characteristic (ZK),
• wherein for said multilaminated materials an almost linear characteristic with a maximum finite gradient in said weight per unit area range to be detected is obtained as said target characteristic approximated to an ideal target characteristic between an output voltage (UA, UZ) at the output of the evaluation and said weight per unit area, for generating said corresponding detection signal,
• and wherein said sensor device is operated in a switchable manner, in pulsed operation, or continuous operation.

Device for the contactless detection of flat objects,

• with first flat objects such as papers in sheet form, with respect to a single sheet, a missing sheet and multiple sheets of said first flat objects, and
• second flat objects such as multilaminated materials like labels adhesively applied to support materials, with respect to a presence or absence of said second flat objects,
• said device having at least one sensor device with at least one transmitter (T) and an associated receiver (R),
• said first and second flat objects being placed in a beam path between said transmitter (T) and said receiver (R) for detection,
• said receiver (R) receiving a measuring signal by a radiation transmitted between said at least one transmitter (T) and said associated receiver (R),
• with means for forming a characteristic of an input voltage (UE, UM) of said measuring signal (UM), and with a downstream evaluating device to which said measuring signal (UM, UE) is supplied for generating a corresponding detection signal, wherein
• said evaluating device has several specific channels for the detection of said first flat objects such as papers and said second flat objects such as multilaminated materials,
• said specific channels having impressed different correction characteristics for the characteristic of the input voltage (UE, UM) of said measuring signal (UM) for papers and for multilaminated materials,
• said correction characteristics (KK) transform said characteristics of the input voltage (UE, UM) of said measuring signal from said receiver (R) as a function of a weight per unit area of the flat objects so as to give a corresponding target characteristic (ZK),
• wherein the first flat objects such as papers produce an approximately linear characteristic approaching an ideal single sheet characteristic with a gradient of approximately “0” in the form of said corresponding target characteristic (ZK) between an output voltage (UA, UZ) at an output of said evaluating device and the weight per unit area, in order to generate said corresponding detection signal, for said first flat objects,
• wherein the second flat objects such as multilaminated materials produce an almost linear characteristic having a maximum finite gradient in said weight per unit area range to be detected, as a target characteristic approximating said ideal target characteristic between an output voltage (UA, ZU) at the output of said evaluation device and said weight per unit area, in order to generate said corresponding detection signal for said second flat objects,
• wherein said sensor device has an operating mode which can be transformed from pulsed operation to continuous operation and vice versa, and wherein in continuous operation the transmitting signal has phase jumps or short interruptions.