Sensor system, sensor roll and method

Abstract

The invention relates to a sensor system for a sensor roll, comprising a first set of sensors and a second set of sensors, which are each distributed over the width of the sensor roll in or on the cover of the sensor roll, characterised in that the sensor system has an electrically conductive shield which is arranged between the sensors and the lateral surface of the sensor roll, wherein the shield is designed such that the first set of sensors is influenced by the shield, while the second set remains completely or largely unaffected by the shield.

Description

[0001] Sensor system, sensor roller and process

[0002] The invention relates to a sensor system for a sensor roller according to the preamble of claim 1, a sensor roller with such a sensor system and a method for operating a treatment device for a fibrous web according to the preamble of claim 10:

[0003] In plants for the production or processing of web-like material, especially for the production or processing of fibrous webs, the web-like material is often passed through treatment nips—so-called nips. These nips can be formed by two rollers or by a roller and another counter element. Examples include press nips, which are used to dewater the web, calender nips, in which the surface of the web is influenced, or nips for transferring a starch solution or an ink (coating color or printing ink) to the web.

[0004] For the operation of the system, it is important to have as good an understanding of the conditions in such a treatment nip, especially the pressure conditions. For this purpose, one of the nip-forming rollers can be equipped with sensors.

[0005] Document EP2331923 B1 proposes the use of fiber optic sensors for this purpose. For this purpose, an optical fiber with Bragg gratings is inserted into the roll cover or between the cover and the core. While these systems allow for precise measurements, they are comparatively expensive and require considerable installation effort.

[0006] Piezo sensors have proven to be a cost-effective and practical alternative. The use of piezo sensors in sensor rolls of paper machines is also already known and is described, for example, in EP 1 753 912. In this case, a series of piezo sensors are connected to a common ground line and a common signal line. The pressure in the nip generates an electrical signal that can be picked up via the signal line. This type of sensor roll is comparatively inexpensive to manufacture, but has several disadvantages. The ceramic sensors described are comparatively thick and inflexible. Due to the constant loading and unloading cycles during operation of the sensor roll, the risk of delamination and thus of destruction of the roll is relatively high.

[0007] As an improvement to this technology, utility model FL 12489 proposes replacing ceramic piezo sensors with printed sensors. Such printed piezoelectric sensors are known per se and are described, for example, in WO2014037016A1. The efficient production and improvement of the signal quality of such printed sensors has recently been the subject of various development projects.

[0008] The object of the present invention is to further improve the capabilities of sensor technology in nip-forming rolls. In particular, the object of the invention is to upgrade existing sensor technology so that new variables and effects can be observed. Furthermore, the object of the invention is to propose improved options for controlling and regulating industrial processes.

[0009] The object is achieved according to the invention by a sensor system according to claim 1, a sensor roller according to claim 9 and a method according to claim 10. Further advantageous embodiments of the present invention can be found in the subclaims.

[0010] A sensor system for a sensor roller is proposed, in particular for a sensor roller for a system for producing or processing a fibrous web. The sensor system comprises a first set of sensors and a second set of sensors, each of which is arranged in or on the cover of the sensor roller, distributed across the width of the sensor roller. According to the invention, the sensor system also has an electrically conductive shield, which is arranged between the sensors and the outer surface of the sensor roller. The shielding is designed such that the first set of sensors is influenced by the shielding, while the second set remains completely or largely unaffected by the shielding.

[0011] During operation of rollers, e.g. in paper machines, printing machines or similar, these rollers can become electrostatically charged. This electrostatic charge is particularly high when the roller is in contact with a counter element, e.g. a counter roller, as is the case in treatment nips. If such rollers are designed as sensor rollers, there is a risk that the built-in sensors or associated electronic components will be affected by this electrical charge, which will lead to interference with the measurement signals. Measures have therefore been developed to prevent this interference with the measurement signals. For example, document DE 10 2023 129 720 describes the provision of electrically conductive shielding arranged between the sensors and the roller surface.

[0012] A key idea of ​​the present invention is that the inventors have recognized that this interference with the measurement signals caused by electrostatic charging can also be used to determine information about the operating state of the system in which the sensor system is used. Therefore, in sensor systems according to aspects of the present invention, a first set of sensors is used, which is intended to determine a desired variable - for example, a pressure, a temperature, etc. - as accurately and reliably as possible. For this reason, an electrically conductive shield is provided for this first set of sensors in order to prevent interference caused by electrostatic charging. The combinations of sensors and shields described in DE 10 2023 129 720 can serve as examples of such a set of first sensors.

[0013] In addition, a second set of sensors is provided, which is either not shielded at all or only significantly weaker than the first set of sensors. One goal of this at least largely avoiding shielding is to prevent the sensor signal from being noticeably disrupted by electrostatic charging on the roller. The signal disruption, or the magnitude of the signal disruption, then provides an indication of the extent of the electrostatic charging on the sensor roller. Depending on the location, this electrostatic charging can indicate a malfunction of the system.

[0014] For example, if a sensor roller is used in a treatment nip where the roller is typically covered by a liquid film, this greatly reduces the electrostatic charge. If this liquid film is missing due to disturbances ("dry running"), the electrostatic charge on the roller increases dramatically. In a measuring system according to aspects of the present invention, this can be detected immediately and reliably via a disturbance in the sensor's measurement signal.

[0015] It is particularly advantageous if the sensors in the first and second sets are of the same type, especially piezo sensors. With such similar sensors, it is particularly easy to detect and assess any disturbance in the measurement signal because the current, undisturbed signal from a similar, shielded sensor is available for comparison.

[0016] In preferred embodiments, both the sensors of the first set and the sensors of the second set can be at least partially printed or comprise printed electronics. Printed sensors are quick and inexpensive to manufacture and, due to their very low thickness, can be used effectively in roll shells without the risk of delamination.

[0017] The sensors of the first set and the sensors of the second set can, for example, be arranged on a common carrier, in particular a common carrier film, or printed onto this common carrier. In this way, it is very easy and precise to ensure the relative position of the sensors to one another, even if the sensor system is not yet installed in a sensor roller. It can also be advantageous if the shielding is also printed in whole or in part, and in particular together with the sensors of the first set and the second set on a common carrier. This way, the shielding is also very precisely defined and can be permanently positioned. This is advantageous because it prevents the sensors of the second set from being excessively affected by the shielding. With this design, almost all essential components of the sensor system can be provided compactly on a common carrier.This simplifies installation and reduces the risk of incorrect installation due to inaccurate positioning of the individual elements relative to one another.

[0018] In principle, in sensor systems according to aspects of the invention, it is possible for the first set and the second set to comprise the same number of sensors. Alternatively, it is possible for the second set to have a different number of sensors, in particular fewer, than the first set. For example, it may be useful to measure a property profile—e.g., a pressure profile—with the first set of sensors at a higher resolution and / or at different positions than those required to detect dry running.

[0019] In preferred embodiments, it can be provided that at least some, in particular all, sensors of the second set each have a corresponding sensor of the first set, and these two corresponding sensors are arranged at the same width position of the roller.

[0020] Corresponding sensors are sensors from the first set and the second set whose signals can be compared to determine the effect of electrostatic charging.

[0021] It is advantageous if the corresponding sensors are of the same type.

[0022] If two corresponding sensors are arranged at the same width position (“CD position”) - or their width position differs by only 10 cm or less - such a comparison of the signals is particularly easy, since possible differences in the signals cannot be caused by the different width position.

[0023] For analogous reasons, it is advantageous if the corresponding sensors are spaced apart from each other in the circumferential direction of the roller by no more than 20°, preferably no more than 10°.

[0024] In a preferred embodiment, it can be provided that the sensors of the first set are arranged over the entire width of the sensor roller, while the sensors of the second set are arranged only in some areas, in particular at the edges of the sensor roller.

[0025] Such a design can be particularly advantageous when coating fiber webs with starch in so-called film presses. Here, it is important to determine the pressure profile across the entire width of the roll gap. However, the risk of dry running is greatest in the area of ​​the edges. Edge scrapers are typically provided there to remove excess starch solution from the roll surface. In dry running, the edge scrapers can cause surface damage to the roll covering after just a short period of time. This problem is particularly critical with roll covers made of polyurethane (PU).

[0026] In alternative embodiments, both the first set of sensors and the second set of sensors can be arranged distributed across the entire width of the roller. In particular, it can be provided that a corresponding sensor from the second set is provided for each sensor in the first set. If the sensors in the first and second sets are of the same type, such an embodiment enables a certain redundancy in the measurement. If, for example, some or all of the sensors in the first set fail - for example, due to damage to the cables or the electronics - the profile of the desired target variable can still be determined using the sensors in the second set.Although these measurements are disturbed by electrostatic effects, since the sensors of the second set do not have sufficient shielding, these disturbed signals still provide more information than would be available in the event of a complete sensor failure.

[0027] Depending on the application, other arrangements of the two sets of sensors may also be advantageous.

[0028] Furthermore, the invention relates to a sensor roller for an industrial plant, in particular for a machine for producing or treating a fibrous web, wherein the sensor roller has at least one sensor system according to one aspect of the invention, which is arranged in or on the cover of the sensor roller.

[0029] In principle, all known types of roller covers are suitable for covering such a roller, such as rubber, polyurethane, or composite covers. Various resins can be used to create the composite covers.

[0030] The mechanical properties of a resin or composite, such as brittleness or flexibility, can be influenced, among other things, by the selection of the resin or by the addition of appropriately selected additives. The following are examples of resins that are generally suitable for use in roll covers, especially in paper machine rolls, and especially for the sensor rolls described here.

[0031] For example, epoxy resins based on bisphenol F diglycidyl ether, which were mixed with various reactive diluents and cured with 2,4,6-tris(dimethylaminomethyl)phenol, showed significantly higher flexural strength than their analogues based on bisphenol A diglycidyl ether (Eren Ozeren Ozgul, M. Hulusi Ozkul: Effects of epoxy, hardener, and diluent types on the hardened state properties of epoxy mortars. Constr. Building Mater. 187, 2018, 360- 370. doi: 10.1016 / j.conbuildmat.2018.07.215).

[0032] Epoxidized novolaks can be designed as oligomers of bisphenol diglycidyl ethers. For example, it has been reported that for fiber-reinforced, particularly glass fiber-reinforced, composites, tensile strength, compressive strength, and flexural strength increase when the matrix resin bisphenol A diglycidyl ether is replaced with a resin based on an epoxidized novolak (Pyeong-Su Shin, Jong-Hyun Kim, Ha-Seung Park, Yeong-Min Baek, Dong-Jun Kwon, K. Lawrence DeVries, Joung-Man Park: Mechanical, Interfacial and Thermal Properties of Different Chemical Structures of Epoxy Resin. J. Powder Metall. Min. 6(2), 2017, 169:1-169:4. doi: 10.4172 / 2168-9806.1000169).

[0033] Epoxy resins prepared by the reaction of epichlorohydrin with novolak phenolic resins formed films when crosslinked with phenolic resins that were more flexible than films made from the homopolymeric bisphenol A epoxy resins (Frank N. Jones, Mark E. Nichols, Socrates Peter Pappas: Epoxy and Phenolic Resins. In: Organic Coatings: Science and Technology, Fourth Edition - Summary: https: / / onlinelibrary.wiley.eom / doi / 10.1002 / 9781119337201 ,ch13).

[0034] Using hybrid resins consisting of inflexible epoxy resins and soft silicone rubbers as an example, it was shown that the elastic modulus of the cured hybrid resins (depending on the ratio of the two resin types) can be adjusted over five orders of magnitude (from approx. 20 kPa to approx. 2 GPa) (Vincent Sebastian Joseph, Theo Calais, Thileepan Stalin, Snehal Jain, Naresh Kumar Thanigaivel, Naresh D. Sanandiya, Pablo Valdivia y Alvarado: Silicone / epoxy hybrid resins with tunable mechanical and interfacial properties for additive manufacture of soft robots. Appl. Mater. Today 22, 2021 , 100979:1 -100979:11. doi: 10.1016 / j.apmt.2O21 .100979). The addition of ether-terminated poly(dimethylsiloxane) to bisphenol A diglycidyl ether resulted in composites with increased toughness and elongation at break; the toughness increased twofold at a poly(dimethylsiloxane) content of only 10 wt% (A. Romo-Uribe, K. Santiago-Santiago, A. Reyes-Mayer, M.Aguilar-Franco: Functional PDMS enhanced strain at fracture and toughness of DGEBA epoxy resin. Eur. Polym.

[0035] J. 89, 2017, 101 -118. doi: 10.1016 / j.eurpolymj.2017.01.041).

[0036] The fibrous webs can be cellulose webs, paper, cardboard or tissue webs, or even textile fibrous webs such as nonwoven webs or fabric webs.

[0037] Such sensor rollers can be used advantageously in paper machines, coating machines, calenders or printing machines, for example.

[0038] With regard to the method, the object is achieved by a method for operating a treatment device for a fibrous web, in particular a press or a film press, wherein the treatment device has a treatment nip for treating the fibrous web, and this treatment nip is formed by a sensor roller according to one aspect of the invention and a counter element, preferably a counter roller, wherein the signals from at least one sensor of the first set are compared with the signals from at least one sensor of the second set.

[0039] As already described, it can be advantageous if the signals from two corresponding sensors are compared with each other.

[0040] The sensors of the first and second sets are typically monitored simultaneously, rather than selectively. This improves the comparability of measured values ​​and the detection of faults.

[0041] Preferably, conclusions about the operating status of the treatment device can be drawn from the comparison of the signals, and in particular, dry running of the treatment device can be detected. Upon detection of a malfunction such as dry running, an alarm can be triggered or automated countermeasures can be initiated. For example, in a film press, the edge scrapers can be lifted.

[0042] The sensor signals are typically forwarded to a central control unit and can be stored there. In the event of a failure, the stored data can also be used to obtain information for subsequent root cause analysis. For example, the sensor data can be analyzed together with other measured values ​​from the system to uncover relevant correlations.

[0043] The invention is explained below with reference to figures. The invention is not limited to the illustrated embodiments. The figures show in detail:

[0044] Figure 1 a shows a sensor system according to one aspect of the invention

[0045] Figure 1 b shows a sensor system according to a further aspect of the invention

[0046] Figure 2 shows a sensor roller according to one aspect of the invention

[0047] Figure 3 shows a film press with a sensor roller according to another aspect of the invention.

[0048] Figures 4a and 4b show sensor signals from shielded and unshielded sensors

[0049] Figure 1a shows a sensor system 1 comprising a first set 10 of sensors 3a and a second set 20 of sensors 3b. The sensors 3a, 3b can be, for example, pressure sensors 3a, 3b. Advantageously, the sensors 3a, 3b of the two sets 10, 20 can be identical sensors 3a, 3b. Particularly preferably, each pair of corresponding sensors 3a, 3b is identical.

[0050] In the embodiment shown here, all sensors 3a of the first set 20 are connected to a common signal or ground line. The same applies to the sensors 3b of the second set 20. While this enables a compact design and is therefore often advantageous, it is not absolutely necessary. In alternative sensor systems 1 according to further aspects of the invention, several signal or ground lines, etc., can also be provided for a set 10, 20 of sensors 3a, 3b. In extreme cases, each sensor 3a, 3b of a set 10, 20 can also be connected individually. The first set 10 and the second set 20 are arranged in Figure 1a on a common carrier 5 in the form of a carrier film 5. The sensors 3a, 3b as well as the lines can advantageously be printed onto the carrier film 5.Furthermore, the sensor system 1 of Figure 1a has an electrically conductive shield 4, which covers the sensors 3a of the first set 10, but not the sensors 3b of the second set 20. This electrically conductive shield 4 can also be printed. Advantageously, a separating layer is provided between the sensors 3a and the shield. Alternatively, the electrically conductive shield 4 can also be implemented in the form of a metal foil or a fine metal mesh.

[0051] While a shielding 4 printed or glued onto the common carrier 5 is advantageous because all essential components are located on the carrier film 5 and the sensor system 1 can be designed essentially in one piece, it is also possible to arrange the shielding 4 separately in the roller cover.

[0052] In the sensor system shown in Figure 1a, the first set 10 has more sensors 3a than the second set 20. The sensors 3a of the first set 10 are distributed across the entire width of the roller after the installation of this sensor system 1. (The distribution can be uniform, but does not have to be). They are used to determine a property profile, for example, a pressure profile. The sensors 3b of the second set 20 are only provided at the edge. This can be advantageous, for example, when used in film presses, where the risk of dry running is greatest in the edge areas.

[0053] The sensor system of Figure 1b differs from the sensor system of Figure 1a only in that the first set 10 of sensors 3a and the second set 20 of sensors 3b both have the same number of sensors 3a, 3b, which are distributed across the entire width of the roller. While in the sensor system 1 of Figure 1a only some of the sensors 3a of the first set 10 have corresponding 33 sensors 3b of the second set 20, in Figure 1b there is a corresponding 33 sensor 3b of the second set 20 for each sensor 3a of the first set 10. Furthermore, with a sensor system 1 as shown in Figure 1b it is also possible to measure a property profile with the sensors 3b of the second set 20, even if this profile is susceptible to electrostatic interference due to the missing shielding 4.

[0054] Figure 2 now shows a sensor roller 2 according to one aspect of the invention. This roller 2 incorporates a sensor system 1 that is largely similar to the sensor system 1 shown in Figure 1a. The sensors 3b of the second set 20 are provided only at the edge.

[0055] The sensor system 1 can be arranged in the roller cover. The roller cover can be made of a polymer material—for example, polyurethane—and the sensor system 1 can be incorporated into the roller cover during the application of the polymer material. If the shielding 4 is not attached to the common carrier film 5, this can also be inserted during the application of the polymer material. Care must be taken to ensure precise positioning. The two sets 10, 20 of sensors 3a, 3b are connected here to a sensor data unit 6. Depending on the design, this sensor data unit 6 can collect the incoming signals, and / or process them, and / or forward them to an external control unit.

[0056] In the embodiment shown in Figure 2, each set 10, 20 of sensors 3a, 3b is arranged helically on the roller. In this way, all sensors 3a, 3b of a set 10, 20 never pass through a treatment nip 31 at the same time. This facilitates the assignment of the individual pressure signals to the corresponding sensors 3a, 3b when measuring a pressure profile.

[0057] Figure 3 shows a film press 30 as an exemplary application. Here, a fibrous web 9, in particular a paper web 9, is guided through a treatment nip 9 formed by a sensor roller 2 and a counter roller 7. An application head 8 is provided on one or both rollers 2, 7, which metered a film of application medium—usually a starch film—onto the surface of the respective roller. This film of application medium is then transferred to the fibrous web 9 in the treatment nip 31. The sensor roller 2 can be designed according to aspects of the invention. This is particularly advantageous because, in such film presses 30, so-called edge scrapers 32 are usually provided on the edges to remove any application medium adhering to the roller 2, 9. If running dry occurs, these edge scrapers 32 can damage the surface of the rollers 2, 9.Therefore, the detection of dry running can be used particularly advantageously in these film presses.

[0058] Figures 4a and 4b show exemplary sensor signals from shielded and unshielded sensors, as they can be measured, for example, when dry running occurs.

[0059] Figure 4a shows the signals from four shielded sensors (S9–S12) passing through a treatment nip 32. The shielding is provided by a grounded metal foil. Although the signals differ in their magnitude—due to a pressure profile that varies across the width—the width of the peaks is narrow and sharply defined, and the signal profile is undisturbed. No interference from electrostatic effects is noticeable.

[0060] Figure 4b shows the signals from the four corresponding, unshielded sensors (S9-S12) for comparison. These are similar sensors to those in Figure 4a. It is clear that the signal width increases noticeably. The signal profile is also visibly distorted, and artifacts are clearly visible in the curve.

[0061] However, if the rollers are moistened instead of running dry, the signal curves for the shielded and unshielded sensors are very similar. The rollers become less electrostatically charged, or rather, the charge is dissipated via the moisture. Thus, there is no interference with the unshielded sensors. If, during operation of a roller, it is determined that - continuously or suddenly

[0062] - If the signal curve of the unshielded sensors changes compared to the shielded sensors, this indicates that the roller is unintentionally running dry. If the signal curve does not change for all unshielded sensors, but only for some of them—e.g., at the right edge of the roller—this can also determine the position where the roller malfunction is occurring.

[0063] List of reference symbols

[0064] 1 sensor system

[0065] 2 sensor roller

[0066] 3a Sensor

[0067] 3b Sensor

[0068] 4 Shielding

[0069] 5 Carrier film

[0070] 6 Sensor data unit

[0071] 7 Counter element, counter roller

[0072] 8 Application head

[0073] 9 Fibrous web

[0074] 10 first set of sensors

[0075] 20 second set of sensors

[0076] 30 film press

[0077] 31 Treatment nip

[0078] 32 edge scrapers

[0079] 33 corresponding sensors

Claims

Patent claims 1. Sensor system (1) for a sensor roller (2), comprising a first set (10) of sensors (3a), as well as a second set (20) of sensors (3b), which are each arranged distributed over the width of the sensor roller (2) in or on the cover of the sensor roller (2), characterized in that the sensor system (1) has an electrically conductive shield (4) which is arranged between the sensors (3a, 3b) and the outer surface of the sensor roller (2), wherein the electrically conductive shield (4) is designed such that the first set (10) of sensors (3a) is influenced by the shielding (4), while the second set (20) remains completely or largely unaffected by the shielding (4).

2. Sensor system (1) according to one of the preceding claims, characterized in that the sensors (3a, 3b) of the first set (10) and the second set (20) are similar sensors (3a, 3b), in particular piezo sensors.

3. Sensor system (1) according to one of the preceding claims, characterized in that both the sensors (3a) of the first set (10) and the sensors (103b) of the second set (20) are at least partially printed or have printed electronics.

4. Sensor system (1) according to one of the preceding claims, characterized in that the sensors (3a) of the first set (10) and the sensors (3b) of the second set (20) are mounted on a common carrier (5), in particular a common carrier film (5).

5. Sensor system (1) according to one of the preceding claims, characterized in that the shielding (4) is also printed in whole or in part, and in particular is printed together with the sensors (3a, 3b) of the first set (10) and the second set (20) on a common carrier (5).

6. Sensor system (1) according to one of the preceding claims, characterized in that at least some, in particular all sensors (3b) of the second set (20) each have a corresponding (3310) sensor (3a) of the first set (10), and these two corresponding (33) sensors (3a, 3b) are arranged at the same width position of the roller (2).

7. Sensor system (1) according to claim 6, characterized in that the corresponding (33) sensors (3a, 3b) are spaced apart from one another in the circumferential direction of the sensor roller (2) by no more than 20°, preferably no more than 10°.

8. Sensor system (1) according to one of the preceding claims, characterized in that the sensors (3a) of the first set (10) are arranged over the entire width of the sensor roller (2), while the sensors (3b) of the second set (20) are arranged only in some areas, in particular at the edges of the sensor roller (2).

9. Sensor roller (2) for an industrial plant, in particular for a machine for producing or treating a fibrous web (9), wherein the sensor roller (2) has at least one sensor system (1) according to one of the preceding claims, which is arranged in or on the cover of the sensor roller (2).

10. Method for operating a treatment device (30) for a fibrous web (9), in particular a press or a film press (30), wherein the treatment device (30) has a treatment nip (31) for treating the fibrous web (9), and this treatment nip (31) is formed by a sensor roller (2) according to claim 9 and a counter element (7), preferably a counter roller (7), wherein the signals from at least one sensor (3a) of the first set (10) are compared with the signals from at least one sensor (3b) of the second set (20). 11 . Method according to claim 10, characterized in that the signals from two corresponding (33) sensors (3a, 3b) are compared with each other.

12. Method according to 11, characterized in that conclusions are drawn about the operating state of the treatment device (30) from the comparison of the signals, and in particular dry running of the treatment device (30) is detected.

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