EP0374481B1 - Apparatus and method for automatically monitoring the destruction of thin sheets - Google Patents

Abstract

The invention relates to a method and apparatus for monitoring the destruction of thin sheet material, in particular bank notes, in an automatic sorting machine, whereby the sheet material is fed by a transport means successively sheet by sheet to a motor-driven cutting means having meshing cutter boards. The destruction process and/or its immediate result are detected by sensor means.

Description

The invention relates to a method and a device for monitoring the destruction of thin sheet material, in particular banknotes in an automatic sorting system, the sheet material being fed from a transport device, sheet by sheet, one after the other to a motor-driven cutting device having intermeshing knife rollers.

Damaged, worn, dirty or otherwise unusable banknotes are sorted out of the money in circulation and destroyed. This is happening increasingly with automatic banknote sorting systems in which, among other things, banknotes that are not fit for circulation are sorted out. Unfit banknotes must be destroyed. For this purpose, the banknotes are cut into narrow strips in a cutting or shredding device and, under certain circumstances, also additionally cut into pieces by cross cutting.

In principle, it is possible to destroy the banknotes sorting machine which are automatically rejected in the banknote sorting machine at a separate location in a separate cutting or shredding device. However, it must be ensured that no banknotes can be lost during the transport of the separated banknotes to the cutting device.

The immediate destruction within the banknote sorting machine is safer. One speaks here of an on-line operation or an on-line destruction in the machine. The advantage of this on-line method is that manipulation is practically impossible, so that no separated banknotes can be lost in any way.

While in the case of the destruction of unfit banknotes separated from the banknote sorting system, it is still possible to count them beforehand, an exact count of the destroyed banknotes must be ensured in the online operation, that is to say in the destruction of unfit banknotes.

DE-PS 27 59 678 shows a device for the automatic destruction of banknotes separated in an automatic sorting system, a light barrier being arranged in front of the cutting device for monitoring the destruction and for counting the destroyed banknotes. The banknotes classified as unfit for circulation reach the cutting device via a branch of the transport device, and they pass the light barrier shortly before entering the cutting device. The known system and also the known method for monitoring the destruction have proven themselves, but it has been shown that erroneous counts can occur due to certain sources of error.

In order to enable the bank notes entering the cutting device to be recorded as completely as possible, the light barrier must be arranged as close as possible in front of the knife rollers of the cutting device. This ensures that a banknote that has passed the light barrier cannot be branched off or picked out in front of the knife rollers. However, the close proximity of the light barrier and knife rollers leads to a rapid contamination of the light barrier, since a considerable amount of chips and dust is generated with each individual cutting process. The function of the light barrier is impaired if cleaning is not carried out at extremely short intervals.

Although the light barrier is arranged relatively close to the knife rollers of the cutting device, there is still a certain distance between the inlet gap of the knife rollers on the one hand and the light barrier on the other hand for design reasons. It has been observed that especially very lobed banknotes or banknotes with kinked leading edges or donkey ears tend to curl up in front of the counter rotating knife rollers so that, although properly counted, they are not destroyed.

If a banknote is partially rolled up in front of the knife rollers, the rear part of the banknote can also remain like a flag in front of the light barrier. Since the light barrier does not report the proper passage of a bank note in good time in this case, an emergency stop of the machine is initiated for reasons of counting security. Since the knife rollers continue to run for a certain time due to the inertia of the moving parts, further separated banknotes may get into the cutting device and either get caught together with the partially rolled banknote in front of the knife rollers or pass through the shredder device with the partially rolled banknote. In any case, the trailing banknotes are not properly counted by the light barrier, since the light barrier of the partially rolled-up banknote in front of the knife rollers is out of function.

In order to avoid a banknote jam in the area of the cutting device, the speed at which banknotes are drawn into the cutting device is set so that it is somewhat greater than the speed at which the banknote is transported to the cutting device. The banknotes entering the cutting device are accelerated briefly while the rear section of the banknote is still in the transport system located. If the banknote breaks, the light barrier may report two events, that is to say two banknotes that have passed through incorrectly, even though they were only the two parts of a single torn banknote.

The object of the invention is to provide a method and a device for monitoring the destruction of thin sheet material, in which the detection of individual sheets and thus the counting of the sheets intended for destruction is carried out with greater accuracy.

The object is achieved by the features specified in claims 1 and 10. Further training is mentioned in the subclaims.

The basic idea of the invention is to monitor the destruction of a bank note using suitable sensory means, the destruction process itself or its immediate consequence being recorded.

The process of destruction itself can be sensed by detecting changes in the electrical or mechanical behavior of the shredder device or by monitoring the typical shredder noise that occurs during the destruction with suitable detectors. In addition to the abovementioned possibilities, the direct consequence of the destruction can be detected by sensing the cut sheet material leaving the cutting device, which forms a kind of "snippet cloud" behind the cutting device in the direction of transport.

In all the methods mentioned, which can be used alone or in combination, only the banknotes actually destroyed are recorded. Furthermore, there is no risk of contamination in all processes, so that corresponding maintenance work is unnecessary or reduced to the usual size. When a sensor signal is recognized, it can safely be assumed that the banknote has been destroyed. The point in time at which a banknote should enter the cutting device can be determined precisely on the basis of the geometry of the transport system and the transport speed. If the sensor signal fails to appear, a machine stop can be reacted to very quickly. Rolled-in notes are recognized in good time. The likelihood of further notes entering the shredder is much lower.

With the solution according to the invention, an almost maintenance-free, trouble-free and very safe counting of the banknotes intended for destruction is possible. In addition to the counting function, the solution according to the invention also allows further statements to be made, for example about banknote length, banknote quality and throughput of multiple banknotes. The sensor signals generated by the sensor means used have a specific duration, intensity and also a specific amplitude profile depending on the banknote length, on the nature of the destroyed banknote and on the excess thickness resulting from overlapping banknotes. For example, the sensor signal can be used to determine whether a whole or two parts of a torn banknote have been destroyed. If several banknotes arrive despite the quick switch-off options, the characteristic of the sensor signal can also provide information about the number of shredded banknotes.

The sensor signals generated according to the invention can be correlated with other detector signals generated in other parts of the banknote sorting system in order to ensure the reliability of the counting and the evaluation of the above To further improve the parameters of destroyed notes.

According to a development of the invention, the sensor signal can be correlated with the signal of a light barrier provided in front of the cutting device. With the help of the light barrier signal, an expectation window is generated, within which the sensor signal must appear if it is running properly. The light barrier can be arranged at a sufficient distance from the knife rollers, which protects it from dirt.

Further advantages and developments of the invention result from the subclaims and from the following exemplary embodiment of the invention, which is explained with reference to the figures.

Fig. 1

eine schematische Ansicht einer automatischen Banknotensortieranlage mit integrierter Vorrichtung zum automatischen Vernichten nicht umlauffähiger Banknoten,

Fig. 2

eine schematische Ansicht einer Vorrichtung zum Zerstören nicht umlauffähiger Banknoten, wobei verschiedene Ausführungsbeispiele zusammengefaßt sind,

Fig. 3

ein Impulsdiagramm zur Veranschlaulichung der Signalverarbeitung der mit der Anordnung nach Fig. 2 gewonnenen Signale,

Fig. 4

ein Blockschaltbild einer Steuer- und Auswerteschaltung für die Einrichtung nach Fig. 2. und

Fig. 5

die grobe Funktionsweise einer piezoelektrischen Folien.

Show it:

Fig. 1

1 shows a schematic view of an automatic banknote sorting system with an integrated device for the automatic destruction of unfit banknotes,

Fig. 2

2 shows a schematic view of a device for destroying banknotes that are not fit for circulation, various embodiments being summarized,

Fig. 3

2 shows a pulse diagram to illustrate the signal processing of the signals obtained with the arrangement according to FIG. 2,

Fig. 4

a block diagram of a control and evaluation circuit for the device according to Fig. 2. and

Fig. 5

the rough functioning of a piezoelectric film.

The invention can be used in general for sheet-like material, but is used in particular for automatic banknote sorting systems. The embodiment described below relates to such a system, as is generally shown in Fig. 1 (see also DE-PS 27 59 678).

According to FIG. 1, this known automatic bank note sorting system 1 comprises several modules or modules 10a, 10b, 10c, 100, 10d - 10h. The pack of banknotes transported in magazines is debanded in module 10a. The banknotes are separated in module 10b. In block 10c it is checked, among other things, whether the banknotes are damaged, worn, soiled or otherwise unsuitable for further circulation. Unfit banknotes can be destroyed in module 100. For this purpose, the module 100 contains a cutting device 20, to which the banknotes that are not fit for circulation are successively fed. The cutting device 20 contains two counter-rotating and intermeshing knife rollers which slit each individual bank note. Cutting devices are also known which cut the banknotes lengthways and crosswise. In any case, the snippets may get into a container 2 with suction air support, which can also be installed remotely from the system. Alternatively, banknotes that are not fit for circulation can also be stored in subsequent modules 10d and 10e in tandem operation. Eligible banknotes are stacked and banded in modules 10f and 10g. In the last module 10h, banknotes are collected which have to be reworked by hand.

The bank notes cut or shredded into chips in module 100 must be counted using a very reliable method, since no conclusions can be drawn from the shredded snippets as to the number of destroyed bank notes. To do this, it is necessary to record each individual cutting or destruction process exactly.

In an exemplary embodiment, FIG. 2 shows details of the cutting device 20 with a plurality of sensors, which can be provided individually or in any combination in order to detect the destruction of a banknote or the direct result of a destruction.

2, individual bank notes are introduced along a transport path T in the direction of the arrow through a slot into a housing of the cutting device 20. At a sufficient distance from the cutting device 20 to avoid contamination, a light barrier 11 is arranged on the transport path T, which registers bank notes passing through. The cutting device 20 comprises two intermeshing knife rollers 12 and 13 which are rotated against each other in the direction indicated by the arrow. The two knife rollers are driven by an electric motor 15 via a drive belt 14.

A first sensor device for generating a signal representative of the destruction of a bank note detects the increased mechanical load occurring during the cutting process. In the exemplary embodiment shown, this is done with a proximity switch 16, which registers the deflection of a tensioning roller 9. When the knife rollers 12 and 13 rotate idle, that is to say without a banknote between the rollers, the drive belt 14 has a certain tension. If a banknote gets between the knife rollers 12 and 13, it increases on the knife rollers acting mechanical load, with the result that the tension of the drive belt 14 increases. As a result, the tensioning roller 9 is moved in the direction of the proximity switch 16, which generates a corresponding signal. A similar signal can be determined on all system components that are affected by the increased mechanical load using suitable sensors (displacement accelerometers or force transducers).

When a banknote passes through the knife rollers 12 and 13, the torque acting as a load moment on the electric motor 15 also increases, with the result that the electric motor 15 connected to a voltage source V draws more current. This increased current consumption is detected by a current sensor 17, which generates a signal representative of the increased current consumption of the motor 15. Such sensors are available as finished components.

This second sensor for detecting the destruction process of a bank note can of course also be used when the electric motor 15 is rigidly coupled to the knife rollers. The signal obtained via the change in current is all the more meaningful the lower the kinetic energy due to the moving masses, which more or less compensates for mechanical stress during shredding. The method described is therefore preferably used when the kinetic energy of the system is low.

A further possibility of sensing the process of destruction by sensors is to evaluate the noise that occurs during each cutting process.

This noise is detected by a microphone 18 and converted into a corresponding electrical signal. The microphone 18 can be coupled via air or directly be connected to the housing of the cutting device, absorbing the structure-borne noise.

Depending on the design of the cutting device and the influence of disturbing machine and ambient noises, the most suitable coupling variant will be selected. Under certain circumstances, the entire cutting device can also be acoustically decoupled from the sorting machine via a corresponding bearing. Acoustic monitoring is preferably used when the kinetic energy present in the system is relatively high, so that a signal obtained via the current change described above does not have the desired informative value.

In addition to the detection of the destruction process, the destroyed sheet material behind the shredder rollers can also be detected using suitable detectors.

Especially in longitudinal cross-cutting devices with suction air support, each destroyed banknote forms a dust and snippet cloud W after it emerges from the knife rollers 12 and 13. The area in which the cloud is formed can be monitored, for example, by an optical sensor 19, the Sensor is arranged outside a housing 8 which is transparent to the sensor radiation. Others, for example ultrasound sensors, are also suitable for detecting the snippet cloud.

Another option for monitoring is the use of piezoelectric materials, in particular piezoelectric foils, which are distinguished by special electrical properties. External forces or deformation result in surface charges of different polarity on opposite surfaces of such a material, which can be measured by measurement. This tension only occurs when the force changes. At As with a capacitor, the voltage signal returns to the value 0 with a constant force, with a certain time constant. A negative force effect of the same size causes a voltage pulse of opposite polarity.

A well-known representative of such piezoelectric films is polyvinylidene fluoride (PVDF) from Pennwalt Piezo Film Ltd. (Great Britain), a long chain semicrystalline polymer made of CH 2 - CF 2. 5 shows the simplest embodiment of such a piezo film for sensor technology purposes. Both surfaces of the piezo film 21 are given a complete metallic coating 23. The change in the surface charge density caused by deformation or bending can be measured on the measuring device 24 as a voltage between the metallic regions or can be processed further for the corresponding purposes.

Further more complicated embodiments of such piezofilms and their metrological evaluation are described in the article by J. Victor Chatigny (Medical Electronics Sept. 1988, 90).

Piezo foils have the advantage that they work in a wide frequency range (1 ... 10 MHz) and have a wide dynamic range in sensitivity. This sensitivity when converting mechanical deformation into electrical signals ranges from the slightest touch to the monitoring of material destruction. Another important point is the low manufacturing and processing costs of these films.

2 shows the use of a piezoelectric film according to the invention in its simplest embodiment. The film 21 is fastened in a flag-like manner behind the shredder rollers 22 in such a way that the snippet cloud when shredding banknotes W meets the piezo film. The pounding banknote chips W deform the film in the manner indicated in FIG. 5 25 and thus induce a voltage between the electrodes 23. This voltage pulse is further processed by the measuring electronics 24. In this way, e.g. B. the analog signal of the film processed and compared with the signal of the light barrier 11 (Fig. 2) in front of the shredder rollers to make sure that every single bank note has actually passed through the shredder.

For all of the sensor signals mentioned above, the simplest form of evaluation consists in comparing the sensor signal with a suitable threshold value once or several times over the signal curve. If the sensor signal exceeds the threshold value, a corresponding counter is incremented by one. The comparison process can be initiated with the rising edge of the sensor signal. With suitable threshold values, statements about destroyed banknotes, about double or multiple banknotes, about the length of the destroyed banknote and its quality are also possible.

A very reliable counting function is guaranteed with all the methods mentioned. If further statements, for example about the banknote quality, are desired, the most suitable procedure will be selected. For example, the acoustic signal is preferably used when statements about the quality of the grade are desired. A relatively well preserved and still rigid banknote makes a different sound than a worn, lobed note. With the help of suitable analysis methods (e.g. frequency analysis) statements about the quality of the destroyed note are possible.

3 and 4, further details of the evaluation will be explained using the example of acoustic monitoring. The acoustic signal is correlated with a light barrier signal, among other things.

FIG. 3 shows the time profile of a rectangular pulse signal S11 generated by the light barrier 11 and a sensor signal S18 generated by the microphone 18. Since the light barrier 11 has a certain distance from the knife rollers 12 and 13 and the bank note has a certain speed, there is a corresponding time delay Δt1 between the two front and back edges of the signals S11 and S18. Depending on the throughput speed of the banknote and the banknote length, the signal S18 has a time period Δt2.

From the light barrier signal S11, a so-called expectation window is generated in a control device, in which the rising edge of the sensor signal S18 must appear after the time Δt1 during normal operation. If the signal does not appear, there is a fault. With this evaluation method, interference signals that lie outside the expected gate are automatically hidden. Another expectation window can be generated to check the time Δt2, which is proportional to the length of the destroyed banknote.

The signal S18 shown in FIG. 3 can alternatively also be a signal generated by the proximity sensor 16, a signal generated by the current sensor 17 or a signal received by the optical detector 19.

4 shows a control and evaluation circuit, the essential component of which is a microprocessor 30 equipped with a memory 32, into which setpoint signals can be input via an input device 31.

The microphone 18 is connected to the microprocessor 30 via a bandpass filter 21, a regulated amplifier 22 and an analog / digital converter 23. The gain of the amplifier 22 can be adjusted by the microprocessor 30 via a digital / analog converter 24. The signal picked up by the microphone 18 is filtered, amplified and converted into a digital value and then, as already mentioned, in the microprocessor 30 correlated with the light barrier signal, processed accordingly.

To check and adjust the functioning of the microphone 18 and the circuit elements downstream of it, the microprocessor 30 outputs a test signal to a loudspeaker 33 and evaluates the test signal recorded by the microphone 18. Corrections are made via the digital / analog converter 24 to the amplifier 22.

The microprocessor 30 is connected to a unit 35, which is responsible, among other things, for controlling the sorting system and for logging the recorded data. For this purpose, the unit 35 has access to a part of the memory 32 in which, depending on the number of parameters evaluated, the results for the notes destroyed in each case are stored. These are, for example: number of destroyed notes, information about length, quality and multiple deduction.

The microprocessor can also be connected to a sensor 36 which permanently monitors the speed of the shredder knives. This information can be used to improve the determination of the length of a destroyed note. Likewise, signals from the state sensors 37 present in the sorting machine can be routed to the microprocessor in order to include the results of these sensors in the evaluation of the quality of a destroyed note.

Finally, the light barrier 11 can be used to obtain additional information that can also be included in the evaluation of the acoustic signal. If the front edge of a banknote is detected by the light barrier 11, the microprocessor 30 outputs an increased current signal to the light barrier 11 so that it can be operated practically as a transmitted light sensor. If several banknotes pass through the light barrier, the translucent light is attenuated more and the amplitude of the signal correspondingly weaker.

Claims (18)

1. A method for monitoring the destruction of thin sheet material, in particular bank notes, in an automatic sorting machine, whereby the sheet material is fed by a transport device successively sheet by sheet to a motor-driven cutting device having meshing cutter blocks, characterized in that the destruction process and/or its immediate result are detected by sensor means.
2. The method of claim 1, characterized in that the electrical load of the drive system is detected.
3. The method of claim 1, characterized in that the mechanical stress of the cutting device or the drive system is detected.
4. The method of claim 1, characterized in that the noise involved in the destruction process is detected by an acoustic sensor device.
5. The method of claim 1, characterized in that the cut sheet material leaving the cutting device is detected by sensor means directly behind the cutting device, in the direction of transport.
6. The method of claim 1, characterized in that the cut sheet material leaving the cutting device is detected by piezoelectric means directly behind the cutting device, in the direction of transport.
7. The method of claims 1 to 6, characterized in that one or more sensor means are used for detecting the destruction process.
8. The method of claim 7, characterized in that the signal of a presence detector disposed before the cutting means, in the direction of transport, is used to form an expectation window.
9. The method of claim 7, characterized in that the signal of at least one sensor is fed to a microprocessor in which the signal can be evaluated with respect to a plurality of parameters, such as a count, a determination of length, a determination of quality, a detection of multiple notes.
10. An apparatus for automatically destroying a certain class of thin sheets, in particular bank notes and the like, rejected by an automatic sorting machine (1), having a motor-driven cutting device (20) equipped with cutter blocks (12, 13) to which sheets to be destroyed are fed singly, and with sensor means serving to count the sheets to be destroyed, characterized in that the sensor means (16, 17, 18, 19) are designed and coupled with the cutting device or follow it in such a way as to detect the destruction process and/or its direct result.
11. The apparatus of claim 10, characterized in that a current sensor (17) is provided for detecting the motor current for the cutting device.
12. The apparatus of claim 10, characterized in that a displacement, force or acceleration transducer (16) is provided for detecting the mechanical stress on the cutting device.
13. The apparatus of claim 10, characterized in that a sound transducer (18) is provided which, directly coupled with the cutting device (20) or coupled via air, detects the noise involved in a destruction process.
14. The apparatus of claim 10, characterized in that the cutter blocks (12, 13) are followed by an optical sensor (19) or an ultrasound sensor for detecting the cut sheet material leaving said blocks.
15. The apparatus of claim 10, characterized in that the cutter blocks (12, 13) are followed by a piezoelectric sensor for detecting the cut sheet material leaving said blocks.
16. The apparatus of claim 15, characterized in that the piezoelectric sensor is a piezoelectric film.
17. The apparatus of one or more of claims 10 to 16, characterized in that a microprocessor is provided for correlating at least one signal representing the destruction process or its direct result with further signals from the cutting and/or sorting device.
18. The apparatus of claim 17, characterized in that the signal representing the destruction process is correlated with the signal from a light barrier (11) disposed before the cutter blocks (12, 13).

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