AT398497B - CODING SYSTEM AND CODE CARRIER - Google Patents

Description

AT 398 497 B

The invention relates to a coding system for the identification of products with a code carrier and a device for evaluating the code of the code carrier and a code carrier for evaluating a code for marking products, which code carrier is arranged under a cover layer and made of magnetic, magnetizable and / or electrically conductive material is for use in a coding system.

Many industrial products are manufactured in large quantities, and their production should and must be monitored step by step. This is necessary in order to be able to optimize the manufacturing process and to be able to recognize an imminent failure of production machines based on tolerances which have not been observed or other production errors.

In this way, manufacturing processes can be optimized, the downtimes of production machines due to planned revision work can be reduced, and the number of products that do not pass quality control can be reduced, thus saving costs.

A complete monitoring of a product means that the product is provided with an appropriate marking or coding, if possible at the beginning of its manufacture. This marking can then be read and logged at every production step. For example, it is possible to register the time of the individual manufacturing steps of each product. This can facilitate cost optimization of the manufacturing process.

Systems for registering products and monitoring production are known in large numbers.

This is how " Barcode " a simple optically read line pattern. This type of coding is used today on a large scale to identify mass products in sales, but problems arise in the manufacture of products when reading the bar code, since contamination can occur or the bar code can be covered during manufacture.

Electronic marking systems consist of an electronic logic circuit into which information can be placed without contact, e.g. can be read in or out via infrared or inductive. Well-known here are the so-called " chip cards " which are used for high security systems, but also for production monitoring. Here the information is stored in a programmable memory chip, which can then be read in and read out via HF. This is an intelligent system that is very versatile. There are read and write functions that can be protected by an appropriate protocol. The disadvantage arises that such systems are too expensive for production with large quantities. The chip can therefore never be permanently integrated into the product. In most cases, the chip would not be able to withstand the production process due to thermal and mechanical loads, since this system is not sufficiently robust.

DE-OS 32 22 789 discloses a magnetoresistive transducer device for reading coded information for franking machines. Here, the code is implemented by the known change in an electrical resistance in a magnetic field ("magnetoresistance"), the arrangement of magnetoresistors and so-called soft-magnetic focusing units representing the code. The shape of the code carrier and its magnetization play no role here. A disadvantage of this system is that, due to its arrangement and its space requirement, it is not suitable for coding mass products. The measurement of the magnetoresistance is also hardly possible without contact.

From DE-OS 37 29 740 an identification system for modules that are moved along a transport path is known. Here, the magnetic code is realized by an arrangement of permanent magnets, the code being represented by the north or south poles. The geometrical shape of the magnets plays no role in this system. The reading elements consist of Hall elements, which allow the north or south pole to be recognized by the voltage supplied. The Hall voltage output in this case is very dependent on the distance and decreases approximately with the third power of the distance, so that a measurement can only produce reproducible statements if the distance tolerances are adhered to. The magnets cannot be placed very close to one another either, otherwise they will influence each other. Such modules, which contain permanent magnets, are neither cheap to manufacture nor easy to integrate into any mass product.

From DE-OS 33 31 694 a similar electronic system for acquiring binary data on workpieces on a transfer line is known. The code information is written into a so-called EPROM (erasable memory component). An inductive system, consisting of a special transmitter, serves both to supply the EPROM with energy and for data transmission. The disadvantage here is that the use of an EPROM is both too expensive for many mass-produced products and that the environmental conditions existing during manufacture, for example pressure, temperature or the like, would destroy the EPROM. In addition, the use of an active component as a code memory basically requires an energy supply, which leads to significant restrictions. 2nd

AT 398 497 B

From DE-OS 27 12 016 a method and a device for detecting and identifying objects provided with coded labels are known. The aim of this known prior art is to facilitate the automatic sorting of packages and mail bags. The code consists of thin magnetic strips or wires. The code is realized by subdividing these magnetic strips or by grouping together several such magnetic strips. Another possibility is to use materials with different coercive field strengths. It is again disadvantageous that this code can hardly be produced so inexpensively in terms of production technology that it can be used in mass products. The known reading unit consists of an AC-supplied excitation coil, which can also have Helmholtz geometry in a known manner in order to generate a more homogeneous field. The code is detected with the aid of balanced detector coils by measuring the voltage amplitudes resulting from induction, or phase shifts, in the case of code materials with different stereoscopic loops. With this system, the measured signal depends on the speed of the moving object. It is therefore only of limited suitability, for example, for a product moving on a conveyor belt.

DE-OS 24 37 547 discloses a method for displaying and evaluating a digital code applied to a carrier using ferromagnetic material. Here, the code is produced by intermeshing, ferromagnetic strips or strip groups. The disadvantage here is that the manufacturing implementation of this code carrier for mass products is too complicated. The presence of the code is determined by a ferromagnetic E-shaped core with three coils. Another disadvantage is that an exact positioning of the reading head is necessary, and furthermore no measures are taken against " wrong " generated by interference from external voltages. Bits are hit.

A code recognition device has become known from DE-OS 30 07 182, magnetic codes being provided in a coded instrument, for example a key, at a multiplicity of code locations. For evaluation, the element having the code is moved, for example, under a Hall effect device, as a result of which an output signal is generated which is dependent on the soft side of the magnet facing the Hall effect device. This makes it possible to evaluate the code

From AT-PS 309 111 it is known to attach a ferromagnetic carrier to a body to be labeled and to magnetically code it from a distance in order to read the code with a reading head. The disadvantage of this method is the attachment of a magnetic carrier, which can easily be disturbed without taking the appropriate precautions.

Some patents deal with the coding of skis, which corresponds to the coding of a mass product. It has become known, for example, to print the surfaces of skis with markings that become visible under UV radiation. The main disadvantage here is that these markings are deleted during certain processing operations, such as grinding, as is also the case with the use of so-called barcodes, which is customary for product identification.

From AT-PS 390 005 it is known to code skis by magnetically applying a code to the edges made of ferromagnetic material (iron) ("magnetic areas"). Again, it is disadvantageous that this code can easily be disturbed or demagnetized if special materials are not used. This code can also be destroyed every time the edges are sanded. For many purposes, an inexpensive coding system that is and remains firmly attached to each individual product would be desirable. It is also advantageous if the coding element is covered in the product, i.e. cannot be arranged directly visible. This also enables the career of the product to be checked after its sale, which e.g. Theft can also be advantageous in warranty cases.

The invention now aims to provide a coding system of the type mentioned at the outset, which is robust, e.g. to survive the production process, which can easily be integrated into as many different products as possible and which can be hidden in them if necessary, and which can also be produced and encoded cost-effectively in order to be usable primarily for mass products.

To achieve this object, the coding system according to the invention is essentially characterized by at least one code carrier made of magnetic, magnetizable and / or electrically conductive material with a defined shape, such as e.g. Recesses, openings and / or cross-section changing over an axis of the code carrier, at least one field source and at least one field sensor for measuring the stray field caused by the code carrier.

The coding system is preferably designed in such a way that the field source generates an electromagnetic field which is displaceable relative to the code carrier, the field source preferably generating a peridi-magnetic alternating field. The field sensor is preferably of a third

AT 398 497 B

Hall probe or field plates or a pick-up coil formed.

In principle, two physically different reading methods can be carried out with the coding system according to the invention: the eddy current method and the inductive method. For the eddy current method, the coding system according to the invention is essentially constructed in such a way that it includes a reading device for the code of the code carrier, comprising the field source and the field sensor, an oscillator for an electromagnetic HF field for exciting eddy currents in the code carrier, a detector coil system, a differential amplifier, a comparator and an output stage for converting the attenuation of the RF field, which is dependent on the geometric shape of the code carrier, into an evaluable code signal. In this way, eddy currents are generated in a metallic conductor by a high-frequency alternating field. For the inductive method, the coding system according to the invention is essentially constructed in such a way that it comprises a reading device for the code of the code carrier, comprising the field source and the field sensor, an oscillator for an electromagnetic HF field for exciting eddy currents in the code carrier, a detector coil system, a differential amplifier, one Comparator and an output stage for converting the deposition of the RF field, which is dependent on the geometric shape of the code carrier, into an evaluable code signal. With the inductive method, a magnetic flux change is measured according to the law of induction.

The information on the code carrier is always read without contact, since it is located inside the product and is preferably not on the surface, although the latter case is not excluded.

The code of the code carrier can be detected in various ways. The reading method to be used depends on the material of the code carrier and its environment. An electrically conductive code carrier such as made of copper, can be scanned using eddy currents. If the code carrier consists of a soft magnetic or ferromagnetic material such as iron or permalloy, the shape variation and thus the code of the code carrier can be scanned inductively. This method has the advantage that the code can also be detected in the presence of other metals.

Any metal is suitable as a code carrier for eddy current scanning. It is preferably a good electrical conductor. The code carrier can also be soft magnetic.

The invention further aims to provide a code carrier of the type mentioned at the outset, which has sufficient mechanical stability and is possibly invisible from the outside, i.e. can only be detected with special devices to be safe against manipulation and environmental influences.

To achieve this object, the code carrier according to the invention essentially consists in the fact that for the evaluation of a stray field of the code carrier which changes in an axis of a plane parallel to the main axis or reading direction of the code carrier, there are openings, recesses or a changing cross section.

The code carrier is the element that contains the information. The material of the code carrier is preferably electrically conductive, i.e. a metal. Soft magnetic behavior and metallic conductivity are particularly favorable. Good conductors, such as Copper. However, the material of the code carrier can only be magnetic. Extremely soft magnetic materials, but also permanent magnetic materials are of particular importance here. The choice of material depends on the reading method chosen.

The code information is stored in a variation of the cross section, or more generally in a special shape of the code carrier. The code is the change of form, e.g. of the cross-section, the profile or the surface, wherein openings, recesses or a changing cross-section are particularly preferred along at least one spatial axis, in particular the main axis of the code carrier.

In a particularly advantageous manner, the code carrier is designed as a plate or film, the code carrier being formed in a particularly preferred manner from a conductive metal-plastic emulsion or magnetic powder-plastic emulsion applied to a substrate. Furthermore, the code carrier has openings, recesses or changing cross-section in at least two planes parallel to the main axis and the openings, recesses or the changing cross-section is (are) regularly formed in one plane.

The optimal shape of the openings or recesses should be adapted to the shape and type of the sensor that is to be used for reading the code information. A metal foil with punched holes can be used as a particularly inexpensive code carrier.

In order to reliably eliminate undesired mainulations of the code carrier, the design is advantageously made such that the code carrier is arranged invisibly from the outside. The code carrier is simply integrated into the workpiece and is not visible from the outside. The code is entered at the beginning of the 4th

AT 398 497 B

Manufacturing can be determined once and cannot and should not subsequently be changed. The code can only be destroyed by destroying the element itself. In any case, there is visible damage to the product, so that the change in the code carrier is also visible. Unwanted manipulations, or those with fraudulent intentions, can easily be discovered.

The invention is explained in more detail below with reference to the drawing. Figures 1 to 6 show schematic views of different code carriers. 7 and 8 show schematically the reading of two code carriers and FIG. 9 shows a circuit diagram. 10 to 16 illustrate various read processes, some with associated signal diagrams. 17 shows a block diagram of an embodiment of the evaluation electronics.

Examples of the shape of the code carrier are shown in FIGS. 1 to 6. 1 shows a metal plate 1, along the spatial axis 2 of which a coding in the form of projections 3 is attached. The coding here is thus in the spatial arrangement of the projections 3 along the spatial axis 2. A bit pattern which is derived thereon is shown.

2, the code carrier is a metal body 4, the surface of which has ribs 5 in an arrangement that means the code. 3 shows in cross section a metal plate 6 which has bulges 7 for coding at certain intervals.

A further advantageous embodiment for such code carriers can e.g. be formed by a metal foil 8, as shown in Fig. 4. This consists of a good leader such as Copper. The coding results from the arrangement of the holes 9. The holes are circular in FIG. 4, but can also have any other shape.

FIG. 5 shows another form of a code carrier similar to that of FIG. 1. The metal plate 10 is provided with projections 11 from both sides and thus coded. FIG. 6 shows an embodiment in which the code carrier consists of disks 12 connected in series. Each disc carries extensions 13, the arrangement of which represents the code.

Components that are used separately do not necessarily have to serve as code carriers. Existing components of the product can also be used for the recording of the code by changing their outer shape accordingly and thus coding them.

A reading arrangement is shown schematically in FIG. Either the reading head 14 is guided past the code carrier 16 in the direction of the arrow 15, or it is the code carrier 16 that is moved past the fixed reading head. 7b is a plan view of the measuring arrangement according to FIG. 7 in the direction of arrow VII b. The reference number 17 denotes holes in the code carrier 16, the arrangement of which represents the code.

Fig. 8 shows a similar arrangement as Fig. 7, wherein the code carrier consists of a metal plate with side extensions, as shown in Fig. 1.

Fig. 9 shows schematically the basic equipment for a reader according to the eddy current method. The principle of the scanning is based on contactless, electronically operating proximity sensors. The reader essentially consists of an oscillator, a trigger and an amplifying switching output.

With its oscillating circuit coil, the oscillator 18 generates an alternating electromagnetic field 21, which emerges from the active surface of the sensor. The frequency of this alternating field determines the depth of penetration into a metallic body, as represented here by the code carrier. The depth of penetration is a parameter that must be adapted to the intended use. Eddy currents are generated in the code carrier by the alternating electromagnetic field according to the Maxwell equations, which are directed in such a way that the primary field is shielded. The strength of these eddy currents depends on the frequency of the alternating field, on the electrical conductivity and, in the case of a magnetic material, also on its permeability. The sensitivity of the overall system can be influenced by a suitable choice of the material of the code carrier. Energy is drawn from the oscillator due to the eddy currents. This causes an amplitude change at the output of the oscillator, which is converted into a logic signal via trigger 19 and the output stage. Logic 20. The HF field is designated 21 and the code carrier is designated 22.

The strength of these eddy currents and thus the strength of the damping depends, among other things, on the geometric shape of the metal, as a result of which the existence of the code elements, namely holes, ribs, etc., can be determined.

Several read heads can be arranged in parallel in order to read several code tracks in parallel.

In the case of inductive scanning, the code carrier consists primarily of a soft magnetic material. The code is transmitted to the outside through the geometry-dependent stray field of the code carrier. There are various technical solutions for reading the code here. 5

AT 398 497 B

After the magnetization process, the code carrier is magnetized by an exciting magnetic field generated from outside. This magnetic field can either be a direct field or an alternating field.

10 shows a reading arrangement according to the method of magnetization with a constant field. The constant field is generated by the permanent magnet 23. Instead of a permanent magnet, a field coil through which direct current flows can also be used. The product and with it the code carrier 24 is moved in the direction of arrow 25 by the magnetic field. Due to the high permeability of the material, the field lines of the external magnetic field are distorted in a way that is significant for the special shape of the code carrier. An example of the field line distribution is shown schematically in Fig. 12. The shape-specific field line distribution is measured over the length of the code carrier via the halo probes 26. Instead of the Hall probes, other appropriate sensors can also be used, such as e.g. Field plates.

To determine the code, the voltage that is induced in pick-up coils can also be used here when the code carrier is moved through a pick-up coil and a magnetic flux change and thereby an induction signal is generated in this way. In Fig. 12 the field coil is designated 27. The code carrier 28 is moved in it and the magnetic field lines shown are formed, which can be used to read the code.

If an alternating field is used as the primary field, the law of induction and thus a so-called pick-up coil are suitable for reading the code. FIG. 13 shows an arrangement suitable for this and FIG. 14 schematically shows the resulting read signal. Within the primary coil 29, which generates an alternating field, the code carrier 30 is moved in the direction of the arrow 31. In accordance with the law of induction, an induction voltage is generated in the pick-up coil 32, the amplitude of which is proportional to the field line density and thus to the special shape of the code carrier. The use of a periodic alternating field is advantageous in terms of measurement technology, since a substantial improvement in the signal-to-noise ratio of the code signal can be obtained by using frequency- and phase-sensitive amplifiers. The amplitude of the code signal changes in the rhythm of the shape variation of the code carrier, so that the read signal reproduces the code of the code carrier.

Instead of the pick-up coil, e.g. a Hail probe can be used which measures the stray field, which varies in shape.

15, 16 show further explanations for the reading method. An iron yoke 33 is used here. The code carrier can be a soft magnetic, but also a permanent magnetic material that is provided with ribs. The sequence of the ribs represents the code. The ribs are identified by the reference numerals 34, 35. The code carrier is partially magnetized by the magnetic yoke 33 moving past if the code carrier is soft magnetic. In the case of a permanent magnetic code carrier, this code carrier reversely magnetizes the soft magnetic yoke. In both cases, the flux change is measured without contact by a secondary coil on the same yoke. Other magnetic field sensitive sensors can also be used here, e.g. Hall probes and field measuring plates. The code read results from the measurement of the stray field, which is scanned in a spatially resolving manner, which is a result of the variation in the magnetic resistance caused by the ribs. The result is an output signal whose amplitude represents a bit sequence that corresponds to the code.

A purely schematic block diagram of the evaluation electronics of the measured signals is shown in FIG. 17. The controller 36 controls the sensors 37. The signals coming from the sensors are amplified in the amplifier 38 and converted into digital signals in an analog-digital converter 39 and forwarded to the computer 40. The code recognition, evaluation and data storage takes place in the computer. The control of the sensors 36 is in turn regulated via the feed control 41, optionally with the interposition of the position detection 42.

Some essential aspects of the invention are emphasized below:

The coding system is used to identify (code) products that are manufactured in large quantities. It is primarily intended for monitoring the production process, but also for safety, quality and guarantee services. A feature is the placement of a code on a code carrier, which can consist of an electrically conductive material (metal), but also of a magnetic (soft or permanent magnetic) or magnetizable material. The choice of material is decisive for the reading process, but also for the legibility of the code. The code consists of shape variations, changes in cross-section, changes in the outlines, ribs or recesses (holes) that are detected using eddy currents or their geometrically determined magnetic stray field. The correspondingly determined location-dependent analog measurement signal can be converted into digital information that corresponds to the code. 6

Claims (12)

AT 398 497 B The code element should preferably be mechanically and thermally robust and invisible from the outside and is therefore largely insensitive to environmental influences and should preferably be accommodated in or on the product, in fact inextricably linked to it. The code carrier can have any shape. The outer shape can be adapted to the shape of the product. The invention is also distinguished by its high flexibility in terms of shape. However, parts of the product which consist of electrically conductive or magnetic material can also be used as code carriers by changing the cross-section, the outlines, the surface or by making recesses of any shape. The code carrier can also consist of permanent magnetic elements. It is advantageous that a magnetic code carrier can be detected even in the presence of electrically conductive other components of the workpiece. This also applies if these are arranged directly above or below the code carrier. In an arrangement for determining the code, consisting of one (or more) eddy current sensors, past which the workpiece containing the code carrier is moved, eddy currents are generated by a high-frequency alternating field. These eddy currents depend on the shape (cross section, thickness, holes, etc.) of the code carrier. The properties of the high-frequency resonant circuit which are changed as a result of the eddy currents thus generated are used as a signal for determining the code. In the case of an arrangement for ascertaining the code contained in a magnetic code carrier, the code is generated in a soft magnetic material by a special shape (cross section, surface, etc.). The code carrier is magnetized in a constant field. The location-dependent stray field, which represents the code, is scanned using field-sensitive sensors. If the code carrier contains permanent magnetic parts, the location-dependent stray field of these permanent magnetic parts is scanned using field-sensitive sensors. The location-dependent stray field that represents the code can be registered by moving the product (with the code carrier) through a coil system with the help of the pick-up voltage thus created. The magnetizing magnetic field can be a periodic alternating field. The location-dependent stray field, which represents the code, is detected as a periodic AC voltage with the aid of a pick-up coil. The advantage here is the use of frequency- and phase-sensitive amplifiers for signal processing, which result in a better signal-to-noise ratio. The location-dependent stray field, which represents the code, can also be detected as a periodic AC voltage using magnetically sensitive sensors (Hall sensors, field plates, etc.). The periodic AC voltage makes the use of a frequency and phase sensitive amplifier for signal processing particularly advantageous. The result is a better signal-to-noise ratio. The code contained in a soft magnetic code carrier, which is defined by a special shape, can be determined with the help of an iron yoke. The eode is fixed by changing the magnetic resistance either with the help of a special coil or again with field-sensitive sensors. If the code carrier contains permanent magnetic parts, these can be scanned using an iron yoke. The code is determined by changing the magnetic resistance either using a special coil or again using field-sensitive sensors. The arrangement of the detector reading heads is preferably such that reading is carried out without contact. Otherwise, the arrangement of the heads of the geometry of the code carrier, as well as that of the product can be adapted and is therefore freely selectable. The distance is determined by the geometric shape of a " bit " and its size, but also by the underlying physics (distance dependence of the stray field). The optimal shape of the "bits" (e.g. holes) is directly related to the shape of the active surface of the sensor used. 1. Coding system for the labeling of products with a code carrier and a device for evaluating the code of the code carrier, characterized by at least one code carrier (1,4,6,8,10,12,22,24,28,30,35, 48) made of magnetic, magnetizable and / or electrically conductive material with a defined shape, such as Recesses, breakthroughs and / or cross-section changing over an axis of the code carrier (3,5,9,9 ', 11,13,17,24,34), at least one field source (14,18,23,27,29,33 ) and at least one field sensor (18, 26, 32) for measuring the stray field caused by the code carrier. 7 AT 398 497 B 2. Coding system according to claims 1, characterized in that the field source (14, 18, 23, 27, 29, 33) generates an electromagnetic field which can be displaced relative to the code carrier. 3. Coding system according to claim 1 or 2, characterized in that the field source generates a periodic, alternating magnetic field (27,29,33). 4. Coding system according to claims 1, 2 or 3, characterized in that the field sensor is formed by a shark probe (26) or field plates. 5. Coding system according to one of claims 1 to 4, characterized in that the field sensor is formed by a pick-up coil (32). 6. Coding system according to claims 1 or 2, characterized in that a reading device for the code of the code carrier comprising the field source and the field sensor comprises an oscillator (18) for an electromagnetic RF field (21) for exciting eddy currents in the code carrier (22), a trigger (19) and an output stage (logic 20) for converting the attenuation of the RF field, which is dependent on the geometric shape of the code carrier (22), into an evaluable code signal. 7. Coding system according to claims 1 or 2, characterized in that a reading device for the code of the code carrier comprising the field source and the field sensor includes an oscillator (18) for an electromagnetic RF field (21) for exciting eddy currents in the code carrier (22), a detector coil system (48), a differential amplifier, a comparator and an output stage (logic 20) for converting the attenuation of the RF field, which is dependent on the geometric shape of the code carrier (22), into an evaluable code signal. 8. code carrier for evaluating a code for identifying products, which code carrier is arranged under a cover layer and consists of magnetic, magnetizable and / or electrically conductive material for use in a coding system according to one of claims 1 to 7, characterized in that for the evaluation of a stray field of the code carriers (1,4,6,8,10,12,22,24,28,30) which changes in an axis (2,15,25,31) of a plane parallel to the main axis or reading direction of the code carrier , 35.46) has openings, recesses or changing cross-section (3.5.9.9M 1.13.17, 24.34). 9. Code carrier according to claim 8, characterized in that the code carrier is designed as a plate (4,6,10) or film (8,16,46). 10. Code carrier according to claim 8, characterized in that the code carrier is formed by a conductive metal-plastic emulsion or magnetic powder-plastic emulsion applied to a substrate. 11. Code carrier according to claim 8, 9 or 10, characterized in that the code carrier (8, 10, 24) has openings, recesses or changing cross-section (9, 9, 11) in at least two planes parallel to the main axis and that in the openings, recesses or the changing cross-section is (are) regularly formed on one level. 12. Code carrier according to one of claims 8 to 11, characterized in that the code carrier (1,4,6,8,10,12,22,24,28,30, 35,46) is arranged invisibly from the outside. Including 7 sheets of drawings 8