ANTISTATIC DEVICE AND ASSOCIATED OPERATING METHOD

Abstract

An antistatic device for reducing electrostatic charges on moving material webs may include an active positive electrode assembly having a plurality of active individual positive electrodes electrically connected to a positive high voltage source. The device may include an active negative electrode assembly having a plurality of active negative electrodes electrically connected to a negative high voltage source. A sensor system may be included for detecting a polarity of a neutralising current between the material web and the antistatic device during operation of the antistatic device, and a controller for controlling the high voltage sources. The controller may be coupled to the sensor system and may be at least one of programmed and configured to one of active or leave activated the high voltage source required in each case and one of deactivate and leave deactivated the high voltage source not required in each case in response to the detected polarity of the neutralising current.

Claims

1. Antistatic device for reducing electrostatic charges on moving material webs (2), having an active positive electrode arrangement (7) with a plurality of active, needle-shaped individual positive electrodes (10) and which is electrically connected to a positive high voltage source (12) during operation of the antistatic device (4), having an active negative electrode arrangement (8) with a plurality of active, needle-shaped individual negative electrodes (13) and which is electrically connected to a negative high voltage source (15) during operation of the antistatic device (4), having a sensor system (20) for detecting the polarity of a neutralising current between the material web (2) and the antistatic device (4) during operation of the antistatic device (4), having a controller (18) for controlling the high voltage sources (12, 15), wherein the controller (18) is coupled to the sensor system (20) for controlling the high-voltage source (12, 15) and is programmed and/or configured such that it activates or leaves activated the high-voltage source (12, 15) required in each case and deactivates or leaves deactivated the high-voltage source (12, 15) not required in each case depending on the determined polarity of the neutralising current.

2. The antistatic device according to claim 1, characterized in that the controller (18) is configured and/or programmed in such manner that it can be switched between at least a learning phase (24), during which the positive high voltage source (12) and the negative high voltage source (15) are activated, and a working phase (25), in which only one of the high voltage sources (12, 15) is active, the sensor system (20) is configured and/or programmed in such manner that it monitors the currents flowing out of the respective high-voltage source (12, 15) in order to detect the polarity of the neutralization current.

3. The antistatic device according to claim 1, characterized in that in addition, a sensor electrode assembly (9) is provided that has a plurality of needle-shaped individual sensor electrodes (16) and is electrically connected to a grounding element (19) during operation of the antistatic device (4), the sensor system (20) is programmed and/or configured in such manner that it monitors the current flowing out from the sensor electrode assembly (9) in order to detect the polarity of the neutralization current.

4. The antistatic device according to any of claims 1 to 3, characterized in that the controller (18) actuates the respectively activated high voltage source (12, 15) in such manner that it delivers a positive or negative non-pulsed DC voltage.

5. The antistatic device according to any of claims 1 to 4, characterized in that the controller (18) is programmed and/or configured in such manner that it determines the polarity of the neutralisation current of the sensor electrode assembly (9) during a learning phase (24) and that it switches to a working phase (25) and in said working phase actuates the high voltage source (12, 15) of the required active electrode assembly (7, 8) for generating a non-pulsed DC voltage depending on the determined polarity.

6. The antistatic device according to claim 5, characterized in that the controller (18) is configured and/or programmed such that, during the learning phase (24) it actuates both high-voltage sources (12, 15) for generating a pulsed DC voltage at the respective active electrode assembly (7, 8), and in the working phase (25) deactivates the high voltage source (12, 15) of the active electrode assembly (7, 8) that is not needed, and switches from pulsed DC voltage to non-pulsed DC voltage for the required active electrode assembly (7, 8), or it keeps both high-voltage sources (12, 15) deactivated during the learning phase (24) and in the working phase (25) only activates the high-voltage source (12, 15) of the required electrode assembly (7, 8).

7. The antistatic device according to any of claims 1 to 6, having a sensor system (20) for measuring a neutralising current from the respectively activated active electrode assembly (7, 8), having a controller (18) for controlling the high-voltage sources (12, 15), wherein the controller (18) is coupled to the sensor system (20) and is programmed and/or configured in such manner that it can switch automatically between to operating modes of the antistatic device (4) depending on the measured neutralisation current.

8. The antistatic device according to any of claims 1 to 7, having a sensor system (20) for measuring a quiescent current of at least one of the two active electrode assemblies (7, 8) and/or of the sensor electrode assembly (9), having a controller (18) for controlling the high-voltage sources (12, 15), wherein the controller (18) is coupled to the sensor system (20) and is programmed and/or configured in such manner that it evaluates the measured quiescent current for detecting electrode abrasion and/or contamination of an electrode, wherein it may be provided in particular that the controller (18) performs the measurement and evaluation of the quiescent current during a diagnostic phase, which is carried out in particular during start-up of the material web (2).

9. Antistatic device according to any of claims 1 to 8, characterized in that the active electrode assemblies (7, 8) are arranged in or on a common bar-shaped electrode carrier (31).

10. Antistatic device according to claims 3 and 9, characterized in that in addition, the sensor electrode assembly (9) is arranged in or on the common electrode carrier (31).

11. Antistatic device according to claim 9 or 10, characterized in that the common electrode carrier (31) comprises terminals (32, 33, 34) for the high-voltage sources (12, 15) and the sensor system (20).

12. Antistatic device according to any of claims 9 to 11, characterized in that the electrode carrier (31) comprises a partition wall (35) that is located between the active electrode assemblies (7, 8) and the sensor electrode assembly (9), wherein it may particularly be provided that the partition wall (35) is designed to be electrically insulating and/or that the partition wall (35) projects beyond the electrodes (10, 13, 16) in the direction of material web (2).

13. Antistatic device according to any of claims 9 to 12, characterized in that the electrode carrier (31) comprises at least one high-voltage conductor (43) that is electrically connected to the respective terminal (32, 33).

14. Antistatic device according to any of claims 1 to 13, characterized in that the sensor electrodes (16) are arranged side by side in a straight sensor electrode (38) row, and/or the positive electrodes (10) are arranged side by side in a straight positive electrode (36) row, and/or the negative electrodes (13) are arranged side by side in a straight negative electrode (37) row, wherein it may be provided in particular that the positive electrodes (10) and the negative electrodes (13) are arranged side by side in a common straight electrode row (39) in an alternating sequence, wherein it may be provided in particular that the sensor electrodes (16), the positive electrodes (10) and the negative electrodes (13) are arranged side by side in a common straight electrode row (40) in an alternating sequence.

15. Antistatic device according to any of claims 1 to 14, characterized in that one or more or all of the positive electrodes (10) are disposed on a carrier foil (41) on which one or more or all of the series resistors (11) of said positive electrodes (10) are imprinted, and/or one or more or all of the negative electrodes (13) are disposed on a carrier foil (41) on which one or more or all of the series resistors (14) of the negative electrodes (13) are imprinted, and/or one or more or all of the sensor electrodes (16) are disposed on a carrier foil (41) on which one or more or all of the series resistors (17) of the sensor electrodes (16) are imprinted, wherein it may be provided in particular that the positive electrodes (10) and the negative electrodes (13) are disposed on a common carrier foil (41), on which the series resistors (11, 14) of the positive electrodes (10) and the negative electrodes (13) are imprinted, and/or wherein it may be provided in particular that the sensor electrodes (16), the positive electrodes (10) and/or the negative electrodes (13) are disposed on a common carrier foil (41), on which the series resistors (17) of the sensor electrodes (16) and the series resistors (11) of the positive electrodes (10) and the series resistors (14) of the negative electrodes (13) are imprinted.

16. Antistatic device according to claim 15, characterized in that the carrier foil (41) is prepared together with the electrodes (10, 13, 16) and the series resistors (11, 14, 17) in a continuous strip material, and/or the carrier foil (41) if furnished with series resistors (11, 14, 17) on both sides thereof, and/or the carrier foil (41) consists of a flexible material.

17. Method for operating an antistatic device (4) for reducing electrostatic charge on a moving web of material (2), wherein the antistatic device (4) comprises an active positive electrode assembly (7) and an active negative electrode assembly (8), in which a polarity of the moving material web (2) is determined, and in which the electrode assembly required in each case to reduce the electrostatic charge of the moving material web (2) depending on the determined polarity is activated or left in the activated state, while the respective electrode assembly (7, 8) that is not required is deactivated or left in the deactivated state.

18. Method according to claim 17, wherein the polarity of the material web (2) is determined during a learning phase (24) and the required electrode assembly (7, 8) for generating a non-pulsed DC voltage is actuated in a working phase (25).

19. A method according to claim 17 or 18, in which a neutralization current of the respectively activated active electrode assembly (7, 8) is measured particularly during the working phase (25) and the antistatic device (4) is switched automatically between at least two operating modes depending on the measured neutralization current, and/or in which a quiescent current of at least one of the two active electrode arrangements (7, 8) and/or a sensor electrode assembly (9) is measured and the measured quiescent current is evaluated for detecting electrode abrasion and/or electrode contamination, wherein in particular the measurement and evaluation of the quiescent current is performed during a diagnostic phase, which is conveniently carried out during startup and/or during standstill of the material web (2).

20. Method according to any of claims 17 to 19, in which the two active electrode arrangements (7, 8) are operated with a pulsed DC voltage during a learning phase (24), in such manner that positive current pulses of the positive electrode system (7) alternate with negative current pulses of the negative electrode assembly (8), in which during a working phase (25) the one active electrode assembly (7, 8) is deactivated while the other active electrode assembly (7, 8) is activated and is operated with non-pulsed DC voltage.

21. Method according to claim 20, in which the two active electrode arrangements (7, 8) are initially operated with a predetermined initial pulse width ratio of positive current pulses to negative current pulses during the learning phase (24), in which during the learning phase (24) after the polarity of the material web (2) has been determined the two active electrode arrangements (7, 8) are operated with at least one transition pulse width ratio of positive current pulses to negative current pulses, wherein with the at least one transition pulse width ratio compared to the initial pulse-width ratio the current pulses required for neutralising the material web (2) are lengthened, whilst the current pulses that are not needed are shortened correspondingly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The diagrammatic drawings show:

[0050] FIG. 1 a highly simplified view of a production facility in the area of an antistatic device,

[0051] FIG. 2 a block diagram of the antistatic device,

[0052] FIG. 3 a voltage-time diagram illustrating different phases of operation of the antistatic device,

[0053] FIGS. 4-6 each show a highly simplified isometric view of various embodiments of an electrode carrier,

[0054] FIG. 7 a cross section through an electrode carrier,

[0055] FIGS. 8 and 9 each show a plan view of various embodiments of a substrate.

DETAILED DESCRIPTION

[0056] As shown in FIG. 1, a production facility 1 in which a material web 2 is moved in a direction of movement 3 comprises at least one antistatic device 4 with the aid of which an electrostatic charge on material web 2 may be reduced and preferably eliminated. Purely for exemplary purposes, in FIG. 1 five positive charge units 5 are indicated on material web 2 before antistatic device 4 in direction of movement 3, wherein said charge units are carried by material web 2 as a result of the production process. Five negative charge units 6 that are generated with the aid of antistatic device 4 are indicated in the area of antistatic device 4 and effect a neutralisation of the positive charge of five positive charge units 5. In the ideal case illustrated, material web 3 has no charge or is charge-neutral after antistatic device 4 in direction of movement 3 of the web.

[0057] As shown in FIG. 2, antistatic device 4 comprises an active positive electrode assembly 7, an active negative electrode assembly 8, and in the example shown a sensor electrode assembly 9 as well. Positive electrode assembly 7 comprises a plurality of active needle-shaped individual positive electrodes 10, to each of which, in FIG. 2, a single series resistor 11 is assigned and which are connected electrically to a positive high voltage source 12. Negative electrode assembly 8 comprises a plurality of active needle-shaped individual active negative electrodes 13, to each of which, according to FIG. 2, a single series resistor 14 is assigned and which are connected electrically to a negative high voltage source 15. Sensor electrode assembly 9 comprises a plurality of individual needle-shaped sensor electrodes 16, to each which, as shown in FIG. 2, a single series resistor 17 is assigned, and which are connected electrically to a grounding element 19. Grounding element 19 is usually an earth conductor. Positive electrode assembly 7 and negative electrode assembly 8 may also be referred to as ionisation electrode assemblies 7, 8. Generally, in another embodiment said sensor electrode assembly 9 may also be dispensed with.

[0058] A controller 18 cooperates with a sensor system 20, which may be used to determine a polarity of a neutralisation current of sensor electrode assembly 9 during the operation of antistatic device 4. Controller 18 serves to actuate high voltage sources 12, 15 and is suitably coupled to sensor system 20. In the example, sensor system 20 is integrated with controller 18. In order to evaluate the signals detected with the aid of sensor system 20 and actuate high voltage sources 12, 15, controller 18 may contain a corresponding microprocessor 21.

[0059] FIG. 2 also shows a plurality of measuring resistors 22, via which electrode assemblies 7, 8, 9 and high voltage sources 12, 15 are connected to grounding element 19, wherein parallel sensor lines 23 are routed to controller 18 and to sensor system 20, which is able to detect the currents flowing through its grounding element 19.

[0060] In this way, the polarity of the charge of material web 3 may be detected through sensor system 20 in conjunction with sensor electrode assembly 9 from the polarity of the neutralisation current of sensor electrode assembly 9. Since sensor electrodes 16 are connected to grounding element 19 via their series resistors 17 and measuring resistor 22, sensor electrode assembly 9 functions as a passive neutralising electrode assembly, through which a neutralisation current flows when material web 2 carries a corresponding charge. The polarity of the charge on material web 2 may be detected by determining the polarity of the neutralisation current. If sensor electrode assembly 9 is not present, the polarity of material web 2 may also be determined with reference to the neutralisation currents that drain off from active electrode assemblies 7, 8, and are detectable by sensor system 18. For example, if a relatively large neutralisation current is flowing at positive electrode assembly 7, it may be assumed that material web 2 is negatively polarised. In this case, both active electrode assemblies 7, 8 are activated while the polarisation of material web 2 is being determined.

[0061] Controller 18 can now disable the active electrode assembly 7, 8 that is not needed depending on the polarity determined. For example, the polarity of the neutralisation current of sensor electrode assembly 9 may be negative, which indicates a negative charge of material web 2. Subsequently, controller 18 activates positive high voltage source 12 and therewith positive electrode assembly 7. At the same time, negative high voltage source 15 and therewith negative electrode assembly 8 is deactivated. On the other hand, if it is determined that the neutralising current of sensor electrode assembly 9 is positive, this indicates that the charge carried by material web 2 is positive. Accordingly, controller 18 causes positive high voltage source 12 to be deactivated, and therewith deactivates positive electrode assembly 7, while simultaneously activating negative high voltage source 15 and negative electrode assembly 8.

[0062] Controller 18 preferably actuates the currently activated high voltage source 12 or 15 at least during a working phase in such manner that a non-pulsed DC voltage is present at the respective active electrode assembly 7, 8, and this voltage is preferably also constant.

[0063] A particularly advantageous approach, which can be implemented with the aid of controller 18, is explained in detail with reference to FIG. 3. For this purpose, controller 18 is configured and programmed accordingly. In the diagram in FIG. 3, the X axis defines a time axis t, and the Y axis indicates voltage U at active electrode assemblies 7, 8. In this context, the voltage curve of positive electrode assembly 7 is located in the positive area of the Y axis, and the voltage curve of negative electrode assembly 8 is reflected in the negative area of the Y axis. Time axis t is divided into a learning phase 24 and a working phase 25. During learning phase 24, which begins at a time t.sub.0, controller 18 causes for example positive high voltage source 12 to supply positive electrode system 7 with positive voltage pulses 26. At the same time, negative electrode assembly 8 is supplied with negative voltage pulses 27 by negative high voltage source 15. Advantageously, positive voltage pulses 26 and negative voltage pulses 27 are temporally phase-offset relative to each other to such a degree that a kind of rectangular AC voltage is created over both active electrode assemblies 7, 8. In other words, positive voltage pulses 26 are positioned synchronously with gaps 28 between adjacent negative voltage pulses 27. Conversely, negative voltage pulses 27 are also positioned so that they take place synchronously with gaps 29 between adjacent positive voltage pulses 26. During learning phase 24, controller 18 in conjunction with sensor system 20 determines the polarity of the neutralisation current of sensor electrode assembly 9. In the example of FIG. 3, a positive polarity is determined, so that the system switches from learning phase 24 to working phase 25 at a t.sub.1. If the polarity of the neutralisation current of sensor electrode assembly 9 is positive, positive high voltage source 12 is deactivated in working phase 25, so that a voltage is no longer supplied to positive electrode assembly 7. At the same time, negative high voltage source 15 is actuated in such manner that starting from said time t.sub.1 it generates a non-pulsed negative DC voltage 30.

[0064] In another embodiment, it may be provided that both ionisation electrode assemblies 7, 8 are deactivated during learning phase 24. As soon as a neutralising current with stable polarity is detected via sensor electrode assembly 9, controller 18 causes the respective required ionisation electrode assembly 7, 8 to be activated.

[0065] During this working phase 25, the neutralisation current of the respective active electrode assembly 7, 8 may be monitored constantly, for example. Thus, in the example of FIG. 3 the neutralisation current of activated negative electrode assembly 8 is monitored in working phase 25. If irregularities or predetermined events occur within this neutralisation current, controller 18 can switch from the current operating mode to another operating mode. Advantageously, controller 18 switches from working phase 25 back to learning phase 24, in which both high voltage sources 12, 15 are active, and advantageously apply DC voltage 26, 27 to both active electrode assemblies 7, 8.

[0066] Additionally or alternatively thereto, a degree of electrode abrasion and/or a degree of electrode contamination may also be monitored by measuring a quiescent current of the respective active electrode assembly 7, 8 and/or the sensor electrode assembly 9.

[0067] The quiescent current is expediently monitored during a diagnostic phase, which is active or switched on for example whenever material web 2 is started up, for example after the material web has been changed. When material web 2 is started up or at a standstill, there is little or no build-up of static charge, so that particularly no ions flow from one of the ionisation electrodes 7, 8 to the material web. The same is also true for passive sensor electrode assembly 9. On the other hand, ions flow through the air between negative electrode assembly 8 and positive electrode assembly 7, and between sensor electrode assembly 9 and at least one of the ionisation electrode assemblies 7, 8. These quiescent currents vary significantly according to the degree of contamination, and also correlate with the abrasion of electrodes 10, 13, 16, and with the erosion of electrode tips 10, 13, 16.

[0068] As shown in FIGS. 4 to 6, positive electrode assembly 7, negative electrode assembly 8 and sensor electrode assembly 9 may be arranged in or on a common bar-shaped electrode carrier 31. Electrode carrier 31 then comprises a positive terminal 32 for connecting positive electrode assembly 7 to positive high voltage source 12, a negative terminal 33 for connecting negative electrode assembly 8 to negative high voltage source 15, and a sensor terminal 34 for connecting sensor electrode assembly 9 to sensor system 20. In the embodiments of FIGS. 4 and 5, electrode carrier 31 may include a partition wall 35, which may particularly be configured to be electrically insulating and to extend between the two active electrode assemblies 7, 8 on the one side and sensor electrode assembly 9 on the other. In this way a short circuit through the air between the two active electrode assemblies 7, 8 and the passively functioning sensor electrode assembly 9 may be avoided. To improve this effect, partition wall 35 may be designed so that it extends beyond electrodes 10, 13, 16 and the tips thereof in the direction of material web 2.

[0069] In the embodiment shown in FIG. 4, the individual positive electrodes 10 are arranged in a straight row of positive electrodes 36. Negative electrodes 13 are arranged in a straight row of negative electrodes 37, and sensor electrodes 16 are arranged in a straight row of sensor electrodes 38. Thus, FIG. 4 shows an embodiment with three separate rows of electrodes 36, 37, 38, which are positioned one behind the other relative to the direction of movement 3 of material web 2 when antistatic device 4 is installed, and rows 36, 37, 38 extend transversely to direction of movement 3.

[0070] FIG. 5 shows a particularly advantageous embodiment in which positive electrodes 10 and negative electrodes 13 are arranged side by side together in a shared straight row of electrodes 39, in such a way that they alternate with each other. In the embodiment shown in FIG. 5, therefore, only two rows of electrodes 38, 39 are discernible.

[0071] In the embodiment shown in FIG. 6, a single row of electrodes 40 is provided, in which positive electrodes 10, negative electrodes 13 and sensor electrodes 16 are arranged side by side in alternating sequence. The order in which the various electrodes 10, 13, 16 alternate in said row of electrodes 40 is indicated in FIG. 6 for exemplary purposes only, so any other sequence or order may also be implemented.

[0072] Since the antistatic device 4 shown here only works with one active electrode assembly 7 or 8 when operating, that is to say during working phase 25, it is not necessary to maintain an especially large distance between electrode assemblies 7, 8, even relative to direction of movement 3 of material web 2. For example, as shown in FIG. 4, the two active electrode assemblies 7, 8 are positioned at a distance 50 from one another in the direction of movement 3 of material web 2 that is smaller than an extension 51 of antistatic device 4 and electrode carrier 31 transversely to material web 2, or smaller than a distance 52 between a first electrode 10 and a last electrode 10 of an electrode group comprising at least five electrodes 10 arranged one after the other or side by side within one of the electrode assemblies 7, 8. In the example of FIG. 4, said electrode group contains five individual electrodes 10. Of course, the electrode group may also comprise more than five electrodes 10, ten for example. Such a compact construction may also be realised if active electrode assemblies 7, 8 are arranged in separate electrode carriers, as long as the small separation distances in the direction of motion 3 of material web 2 described above are observed.

[0073] FIG. 7 shows a cross section through am electrode carrier 31 with a U-shaped profile, which contains only one row of electrodes in the example. This may be positive electrode row 36 or negative electrode row 37, or also sensor electrode row 38, or the shared electrode row 39, or even shared electrode row 40. The respective electrode 10, 13, 16 is mounted on a substrate 41, which is embedded in an electrically insulating material 42. Electrode carrier 31 also includes a high voltage conductor 43 that is electrically connected to the respective terminal 32, 33 or 34. High voltage conductor 43 may be made from a carbon fibre composite body and in this case may serve to stiffen electrode carrier 31. In the example, the carbon fibre composite body is in the form of a strip and flat, and has a rectangular profile.

[0074] As shown in FIG. 8, substrate 41, on which electrode 10, 13, 16not shown in FIG. 8can be mounted, comprises a carrier material 44 on which a resistor track 45 made from a resistor paste 46 is imprinted. In addition, two contact zones 47 are imprinted on substrate 44 in the region of the ends of resistor track 45, such that the ends of resistor track 45 are in electrical contact with the two contact zones 47. Substrate 44 is advantageously a plastic material. For example, said plastic material may be FR4, which is used for example for manufacturing printed circuit boards. Alternatively, the plastic material may be polyester or PEEK or polyimide. Resistive paste 46 is a polymer paste. Examples of substances that may be considered for use as polymer paste include an epoxy resin varnishing system, wherein electrically conductive particles and electrically non-conductive particles are embedded in the epoxy resin. The ratio of the electrically conductive particles to electrically non-conductive particles, and the density of the particles within the epoxy resin determine the electrical resistance of the resistive track 45 that is produced using the polymer paste. Electrically conductive particles are for example carbon black or graphite. Electrically non-conductive particles are for example titanium oxide (TiO) and aluminium oxide (Al.sub.2O.sub.3). Substrate 41 may be manufactured with resistance values ranging from 100 k to 100 G. Substrate 41 may be used in voltage ranges from 1 KV up to 150 KV. Substrate 41 has a power consumption not exceeding 1 W. Depending on the size of substrate 1, in principle the power consumption may also be greater than 1 W.

[0075] Since a plastic is used as carrier material 44, it is also possible to implement relatively thin support materials 44, having a thickness less than 1 mm or less than 1.0 mm. In this case, it is also possible to create a flexible carrier material 44 depending on the plastic material used. In particular, substrate 41 may be constructed as a carrier foil. Said carrier will also be designated with reference sign 41 in the following.

[0076] Contact zones 47 can be used to attach said electrode 10, 13, 16 to one side of carrier foil 41, and an electrical connection to the other side. The respective terminal and the respective electrode 10, 13, 16 may be soldered to the respective contact zone 47, for example. It is also possible to crimp the terminals or electrodes 10, 13, 16 with contact zones 47. Alternatively, electrical contacts may also be produced by applying a coating or adhesive layer using an electrically conductive adhesive or an electrically conductive varnish. A plug connection or clamping connection is also conceivable. Foil carrier 41 may also be provided with a protective layer 48 made from a plastic, which is designed to be electrically insulating and is applied to carrier foil 41 in such manner as to cover at least the resistive paste 46 or resistor track 45. More particularly, the entire carrier material 44 may be coated with said electrically insulating protective layer 48, preferably leaving recesses for electrical contact zones 47.

[0077] In order to manufacture the carrier foil 41 presented here, the electrical contact zones 47 may first be imprinted on carrier material 44. Then, contact zones 47 may be burned in. Contact zones 47, may be burned in in a temperature range from about 150 C. to 220 C. inclusive. Electrical contact zones 47 may be made from conductive silver for example, which may preferably be prepared on a polymer epoxy resin. After electrical contact zones 47 are burned in, the respective resistor track 45 can be imprinted on carrier material 44. After resistor track 45 has been imprinted, said resistor track 45 is also burned in. The burning in process for resistor track 45 may be carried out in a temperature range from about 150 C. to about 240 C. inclusive. After the respective resistor track 45 has been burned in, an injection moulding process may also be carried out, by means of which the insulation layer 48 is applied. Insulation layer 48 covers at least resistor track 45. Depending on whether electrical terminals and electrodes 10, 13, 16 have already been attached to contact zones 47, insulation layer 48 may also cover contact zones 47. The injection moulding process for applying insulating layer 48 is preferably designed as a low-temperature spraying process, which is carried out at a temperature below 200 C. Contact zone 47 and/or resistance track 45 is/are expediently applied in a screen printing process. The use of a polymer paste as a resistance paste 46 makes it possible to burn in resistor track 45 at relatively low temperatures, so that a plastic material may be used for carrier material 44. In this way, carrier foil 41 is extremely inexpensive. The manufacturing process is also relatively inexpensive, since only relatively low firing temperatures have to be implemented, so the energy requirements for obtaining the firing temperatures and carrying out the burning in processes are comparatively low. An embodiment of the process in which a plurality of carrier foils 41 is produced on a sheet of carrier material 44 at the same time, and are then separated by cutting or punching is particularly convenient. In this way, the time for producing single carrier foils 41 can be significantly reduced by printing a plurality of contact zones 47 and/or a plurality of resistor tracks 45 at the same time.

[0078] The carrier foil 41 shown in FIG. 8 is suitable for positioning a single electrode 10, 13, 16. Of course, as shown in FIG. 9 for example, in other embodiments a plurality of electrodes 10, 13, 16 may be arranged on such a carrier foil 41, in which case a corresponding number of series resistors 11, 14, 17 may be imprinted on carrier foil 41 in the form of resistance paths 45. It is also possible to provide a common carrier foil 41 bearing all series resistors 11 in the form of resistance paths 45 for all positive electrodes 10. The same applies for a shared carrier foil 41 for all negative electrodes 13 with the corresponding series resistors 14. Again, this also applies for a shared carrier sheet 41 for all sensor electrodes 16 and the associated series resistors 17 in the form of resistive tracks 45. In principle, any permutations of the above arrangements are also conceivable.

[0079] As shown in FIG. 9, in another embodiment of carrier foil 41 it may be provided to imprint a plurality of resistor tracks 45 made from resistive paste 46 on carrier material 44. Further, a corresponding number of contact zones 47 may also be imprinted, for contacting the electrodes 10, 13 or 16 for example. If electrodes 10, 13, 16 are assigned to the same electrode assembly 7, 8, 9, all the resistive tracks 45 may be electrically connected to each other via a common contact strip 49, wherein the contact strip 49 itself is imprinted in correspondence with contact zones 47. In this context, an embodiment in which carrier foil 41 is produced from a flexible material is particularly advantageous. It is also advantageous if carrier foil 41 is produced as a continuous strip together with resistive tracks 45, contact zones 47 and contact strip 49. The carrier foil 41 may then be customised for a given application by cutting the required number of electrodes to size.

[0080] In another advantageous embodiment, it may be provided for the carrier foil 41 to be usable on both sides. For example, positive electrode assembly 7 may be created on the front of carrier foil 41, facing the viewer in FIG. 9, by applying series resistors 11 of positive electrodes 10 to the front of carrier foil 41 in the form of resistive tracks 45. Resistive tracks 45 may then be applied to the rear of carrier foil 41, facing away from the viewer in FIG. 9, to form series resistors 14 of negative electrode assembly 8. In this case, carrier foil 41 can be printed conveniently on both sides in such manner that that the positive electrodes 10 and negative electrodes 11 are printed in alternating sequence in the longitudinal direction of carrier foil 41. Further, printed conductor strips 49 may be positioned such that a short circuit through the support material 44 can be avoided.