Roll having shielding for sensors

Abstract

The invention relates to a roll for a material-web-processing machine, the roll comprising a roll cylinder having a cylindrical roll core, a roll coating surrounding the roll core, and a lateral surface, the roll coating consisting of one or more roll-coating layers in the radial direction and containing sensors, characterized in that an electrically conductive shielding is located in the radial direction between the sensors and the lateral surface. The invention also relates to a material-web-processing machine comprising the sensor roll and a pressure roll arranged in parallel with the sensor roll, with a treatment gap being located therebetween, wherein each of the sensors of the sensor roll can measure the pressure exerted onto the sensor roll when material passes through the treatment gap.

Description

Roller with shielding for sensors Field of the invention The present invention relates to a roller for a material web processing machine and to a material web processing machine containing the roller. State of the art WO 2013 / 104600 A1 and US Pat. No. 5,562,027 disclose rolls for a paper machine equipped with sensors for measuring pressure in a roll nip. WO 2013 / 104600 A1 discloses fiber optic sensors, while US Pat. No. 5,562,027 uses conventional piezoelectric sensors. Printed piezoelectric foils for pressure sensing are known from WO 2014 / 037016 A1. FI 12489 U1 discloses a roll for a paper machine with a sensor structure printed beneath the roll surface. Problems to be solved by the invention In a roller with pressure sensors, the quality of the readout signal decreases under certain conditions. For example, this occurs when the roller forms a roller pair with another roller with a treatment nip in between, and the roller pair is operated in a dry state. The inventors have recognized that this disturbance in signal quality is caused by electrostatic charging of the roller reference surface. Therefore, it is the object of the present invention to provide a roller with an improved sensor system that delivers reliable sensor values ​​of good quality even under difficult operating conditions. Summary of the invention The object was achieved by providing a roller for a material web processing machine, wherein the roller contains an electrically conductive shield, as well as a material web processing machine containing the roller. The subject matter of the present invention is defined in the following aspects: [1] Roller for a material web processing machine, wherein the roller comprises a roller cylinder having a cylindrical roller core, a roller cover surrounding the roller core and a lateral surface, wherein the roller cover consists of one or more roller cover layers in the radial direction and contains sensors, characterized in that an electrically conductive shield is arranged in the radial direction between the sensors and the lateral surface. [1 -1] Roller according to aspect [1], wherein the sensors are arranged under the functional layer of the roller, wherein the thickness of the functional layer is preferably 3 mm to 40 mm. [1 -2] Roller according to aspect [1] or [1 -1], wherein the material web processing machine is a paper web processing machine. [1 -3] Roller according to one of the preceding aspects, wherein the length of the roller is 1 to 20 m, the diameter of the roller core is 5 to 100 mm, the thickness of the roller cover is 5 to 50 mm, the roller cover has more than 5, preferably more than 10 sensors and the thickness of the shielding is 1 pm to 10 mm. [2] Roller according to one of the preceding aspects, wherein the sensors are pressure sensors. [2-1] Roller according to aspect [2], wherein the sensors are piezoelectric sensors. [3] Roller according to one of the preceding aspects, wherein the sensors are arranged on the roller core or between two roller covering layers. [4] Roller according to one of the preceding aspects, wherein the sensors are separated from the shield by insulation. [5] Roller according to one of the preceding aspects, wherein the sensors are applied as a sensor layer to the roller core, to a roller covering layer, to the insulation or to a sensor film. [5-1] Roller according to aspect [5], wherein the sensor layer contains the sensors and electrical conductors. [5-2] Roller according to aspect [5] or [5-1], wherein the thickness of the sensor layer is 1 pm to 50 pm. [5-3] Roller according to one of the aspects [5] to [5-2], wherein the sensors are arranged on the shield and separated from it by insulation. [5-4] Roller according to any one of aspects [5] to [5-3], wherein the shield is a metal foil, the insulation is printed on the metal foil and the sensors are printed on the insulation. [5-5] Roller according to aspect [5-4], wherein the thickness of the metal foil, the insulation and the sensors is each 1 pm to 50 pm. [5-6] Roller according to one of aspects [5] to [5-2], wherein the sensor film is a polymer film. [5-7] Roller according to aspect [5-6], wherein the thickness of the polymer film is 50 pm to 3 mm. [6] Roller according to one of the preceding aspects, wherein the sensors are printed or the sensor layer is printed. [7] Roller according to one of the preceding aspects, wherein the shield is electrically conductive by containing metal-containing or carbon-containing materials. [8] A roller according to any one of the preceding aspects, wherein the shielding is a roller covering layer containing electrically conductive material, a shielding film, a shielding net or a shielding layer applied to the sensors or the insulation on the sensors. [8-1] Roller according to aspect [8], wherein the electrically conductive material is a fabric or contains threads or particles, preferably soot particles or nanotubes, embedded in the roller covering layer. [8-2] Roller according to aspect [8], wherein the thickness of the shielding film is 1 pm to 100 pm. [8-3] The roller according to aspect [8], wherein the shielding foil is a metal foil having a thickness of 1 pm to 50 pm. [8-4] Roller according to aspect [8], wherein the shielding layer covers the sensors and adjacent areas. [9] Roller according to aspect [8] or [8-4], wherein the shielding layer is printed. [9-1] Roller according to aspect [9], wherein the thickness of the shielding layer is 1 pm to 50 pm. [9-2] Roller according to aspect [9], wherein the sensors are printed on a sensor film, an insulation is printed on the sensors and the shielding layer is printed on the insulation, wherein the thickness of the sensors, the insulation and the shielding layer is each 1 pm to 50 pm, preferably 5 pm to 40 pm.

[0010] Roller according to one of the preceding aspects, wherein the roller core is electrically conductive and electrically contacts the shield. [10-1] Roller according to aspect

[0010] , wherein the shield touches the roller core. [10-2] A roller according to aspect

[0010] or [10-1], wherein the roller core is electrically grounded. [10-3] Roller according to one of the aspects

[0010] to [10-2], wherein the shielding is a shielding film or an electrically conductive roller covering layer and the sensors are separated from the shielding by insulation.

[0011] Roller according to one of the aspects

[0010] to [10-3], wherein either the shielding is a foil which extends beyond the roller cylinder and electrically contacts the roller core, or the sensors are arranged between the roller core and an electrically conductive roller covering layer and the roller core and the electrically conductive roller covering layer are in electrical contact between the sensors. [11-1] Roller according to aspect

[0011] , wherein the roller core extends longitudinally beyond the roller cylinder.

[0012] Roller according to one of the preceding aspects, wherein the signals generated in the sensors are transmitted to a sensor data unit via a signal line. [12-1] Roller according to aspect

[0012] , wherein the sensors distinguish each other in their position in the circumferential direction of the roller cylinder. [12-2] Roller according to aspect

[0012] or [12-1], wherein a single signal line carries the signals from several or all of the sensors to the sensor data unit.

[0013] Roller according to one of the preceding aspects, wherein a position sensor for detecting the angle of rotation of the roller is arranged on one of the end faces of the roller.

[0014] Roller according to aspect

[0013] , wherein the position sensor and the sensor data unit are arranged on the same end face of the roller and are connected to one another via a data line.

[0015] Material web processing machine comprising a roller according to one of the aspects [1] to

[0014] as a sensor roller and a counter-roller arranged parallel to the sensor roller with a treatment gap in between, wherein each of the sensors of the sensor roller can detect the pressure exerted on the sensor roller when passing through the treatment gap. Advantages of the invention The shielding in the roller according to the invention improves the quality of the signals detected by the sensors in the roller. Embodiments of the invention The roller according to the invention for a material web processing machine is hereinafter sometimes referred to simply as "the roller." Likewise, the components of the roller or material web processing machine according to the invention are hereinafter sometimes referred to simply as "the sensors," "the shield," and the like. The roller comprises a roller cylinder having a cylindrical roller core, a roller cover surrounding the roller core and a shell surface, wherein the The roller cover consists of one or more roller cover layers in the radial direction. The roller core is made of metal, for example. The roller cover is made of polyurethane, rubber, a composite material, or a fiber composite, for example. The roller can be used for pressure detection in a web processing machine. Examples of web materials include nonwovens, fabrics, foils, paper webs, or metal webs. The machine can be suitable for the following web processing applications: • Coating processes, for example for encapsulations, in particular in photovoltaics, in packaging technology, in particular food packaging, battery production, in particular in the production of anodes, cathodes and separators, for OLED and optical layers as well as for anti-scratch coatings, anti-dust coatings and electrostatic coatings; • Bonding processes, laminating processes, calendering processes; • Laminations, for example in the production of encapsulations, multi-composites, PCB laminates, packaging or pouches, batteries and fuel cells, wound capacitors, flexible electronic circuits and solar cells, displays and for medical applications, in particular for the production of plasters or test strips; • Assembly processes, for example for the production of electronic components; • Grinding and rolling mills; • Conveyor belts, for example for recycling or sorting; • Extrusion systems, for example for film production; • Printing processes such as graphic printing, newspaper or paper printing, label printing, money printing, for printed electronics, offset printing, gravure printing, flexographic printing, gravure printing, OLED and optical applications; • In printing processes such as nanoimprint lithography or hot stamping, in particular anti-reflective coatings; • Web run optimization, for example for measuring web tension or tensile force or in vacuum coating, particularly for metal coatings, also for food; • Finishing of textiles, in particular by printing, coating or dyeing; • Steel and metal strip production; • Condition monitoring for large substrates, especially wind turbines. A paper machine, as an example of a material web processing machine, produces paper webs with a width of over 10 m. The rollers required for this are even wider, as they extend beyond the paper web on both sides. For processing the paper web, pairs of rollers with a treatment gap between them are used. A treatment nip can be, for example, a press nip for mechanical dewatering, a calender nip for smoothing, or an application nip for injecting a starch solution into the web to increase strength. At least one of the rollers in the roller pair contains sensors for pressure detection. Since a pressure profile is typically recorded across the entire working width, a large number of sensors can be manufactured, for example, on a sensor film at least as long as the roller and applied to the roller. In the roller, the sensors, insulation, and shielding can be applied as layers onto another layer or substrate. Herein, the term "applied" means that the starting material of the desired layer is applied in a coatable form, for example, in liquid or paste form, and then solidified into the desired layer. Application can be carried out by printing, vapor deposition, or spraying, with printing being preferred, so that the term "applied" always preferably means "printed." On the other hand, when printed layers are described herein, this is done for convenience only, and the layers can equally be applied by another method. Components may be referred to in the singular, for example, "a sensor layer" and "the shielding." These expressions are not intended to exclude a plural and therefore mean "at least one sensor layer" or "the at least one shielding." Accordingly, expressions such as "contains ... a sensor layer" and "contains ... the shielding" or similar formulations are synonymous with "contains ... at least one sensor layer" or "contains ... the at least one shielding." This also applies accordingly to the other components of the roller or the material web processing machine. Sensors The roller contains, for example, 5 to 20 sensors. The sensors are distributed along the entire length of the roller. In other words, the sensors differentiate from one another in their position along the roller's rotational axis. They can also differentiate from one another in their position along the circumferential direction of the roller cylinder. The sensors respond to at least one change in an environmental property selected from the group consisting of pressure, temperature, and light intensity. They can therefore be pressure, temperature, and / or optical sensors, with a pressure sensor being preferred. The pressure sensor can be a piezoelectric sensor. The sensors can be embedded in a roller coating material, such as a polymer. They can also be applied as a thin sensor layer on a substrate. be applied. Examples of substrates are films, preferably flexible plastic films. The use of a printed sensor layer is very advantageous for many applications, for example for use in rotating rollers. Firstly, it is inexpensive to produce. Secondly, the flat design and flexible film structure of the sensor layer allow it to be easily attached to a curved roller without the risk of delamination. With conventional sensors, this risk is quite high because the roller is subjected to considerable continuous flexion during operation when it forms a press nip with a second roller. The sensor may be a layered sensor comprising a first electrically conductive layer, a layer of a ferroelectric polymer, and a second electrically conductive layer, in that order. Preferably, the ferroelectric polymer layer, the electrically conductive layers, and the conductor are printable. Shielding The shielding is electrically conductive. Here, the term "electrically conductive" also includes the meaning of "electrically dissipative." The shielding should be sufficiently conductive to achieve the desired goal of consistent signal quality by preventing electrostatic charging of the composite. For example, the volume resistance of the shielding layer is less than 10 9 Ohm. The shielding is arranged radially between the sensors and the outer surface. This means that the shielding is arranged with respect to a sensor such that, in a circular cross-section of the roller cylinder, the shielding and the sensor are intersected by the same radial line. In the roller, electrostatic interference is reduced both by the distance between the sensors and the roller surface and by the electrically conductive shielding. Since the thickness of the roller covering is usually between 15 mm and 30 mm, electrostatic interference can be reduced simply by applying the sensors to the roller core or to a layer below the roller surface. For example, a base layer of the roller covering with a thickness of 3 mm to 7 mm can be applied to the roller core. The sensor film can then be applied to this base layer. The remainder of the roller covering can then be applied over the sensor film as a functional layer. A functional layer is the outermost layer of the roller's outer surface and represents the contact surface for the material web. The thickness of the functional layer can be between 12 mm and 25 mm. The distance between the shielding and the sensors should be small to ensure the shielding effect is as effective as possible. For technical reasons, a distance of and the sensor electronics. Therefore, the required insulation thickness determines the minimum distance. The shielding can have any planar structure; it can be a continuous layer without through-holes or it can have a grid, mesh, or woven structure. The shielding is preferably designed as a shielding layer, with the following embodiments (i) to (iv) being possible. (i) The shielding can be a foil, for example, glued or laminated. The foil can be a metal foil, such as aluminum foil, or a foil made of a conductive polymer. An example of a conductive polymer is PEDOT:PSS (PEDOT:PSS: poly(3,4-ethylenedioxythiophene):polystyrenesulfonate). Alternatively, a grid or mesh structure can be used instead of a continuous foil, for example, to save weight. (ii) The shielding can be applied as a layer to a substrate, for example, by printing. If the electronics are printed anyway, it can be advantageous to also print the shielding layer. In this case, the shape, size, and thickness of the shielding can be very flexible. For example, the shielding only needs to be printed in the area of ​​the electronic elements and the wires. Printable materials that can be used include electrically conductive polymers, such as PEDOT:PSS, or printable metallic nanowires, carbon, and / or Ag. The applied shielding layer can also be a layer of an electrically conductive adhesive, for example, an acrylate adhesive filled with Ag nanoparticles, thus fulfilling the additional function of firmly bonding two layers or substrates. (iii) The shielding is based on a non-conductive material, i.e., it contains at least 50 mass percent, more preferably at least 80 mass percent, of this material. For example, the shielding can be a polymer-based film in which conductive substances are embedded such that a shielding film is formed that is conductive as a whole. Examples of such substances are carbon nanotubes or conductive carbon black. (iv) In a special case of embodiment (iii), the shielding can have another function in addition to its shielding effect, possibly as its primary function. For example, carbon or metal threads can be incorporated as a woven fabric in a roller covering layer made of an epoxy resin, with the thread-like materials also providing the strength necessary for the actual function of the roller covering layer. The shielding must at least cover the electrically conductive elements of the sensors. Preferably, the shielding also extends laterally beyond these elements. For example, the shielding extends beyond the sensor by at least the distance between the shielding and the sensor. When using a foil, this is usually the case anyway. Case. With printed shields according to (ii), however, very thin and small-area shields can also be produced. For example, an insulating layer with a thickness of 15 μm is applied to the printed electronics. The shielding layer is printed onto this insulating layer. In this case, the shielding layer should be wide enough to cover the electronic components and extend at least 15 μm beyond them laterally. The shielding can be very thin. For example, commercially available aluminum foils with a thickness of 4 to 20 pm, especially 10 to 15 pm, are sufficient for shielding. The insulation consists of a material that electrically isolates the sensors from the shielding. To fulfill this function, the insulation must have a higher electrical resistance than the shielding. An example of an insulation material is a non-conductive polymer. The insulation is preferably printable as a layer. The insulation can also be an adhesive layer that, for example, bonds a film substrate printed with sensors to the shielding layer. In one embodiment, the roller core is electrically conductive, for example, metallic, and electrically contacts the shield. The shield can be a foil that extends beyond the sensors or extends longitudinally beyond the roller cylinder and electrically contacts the roller core. Alternatively, the sensors can be arranged between the roller core and an electrically conductive roller covering layer, with the roller core and the electrically conductive roller covering layer being in electrical contact between the sensors. The roller core can be electrically grounded. Signal cable and position sensor When a sensor passes through the treatment gap, a signal is generated that is transmitted via a signal line to the end face of the roller, where it is then processed by a sensor data unit and, if necessary, transmitted to an external evaluation unit. Such a sensor data unit is preferably mounted on the end face, i.e., the cover of the roller. If the sensors are mounted parallel to the roller axis, all sensors pass through the treatment gap simultaneously. To assign the signals to the correct sensors, each sensor requires its own signal line. However, this requires very wide sensor bands when using many sensors. Therefore, the sensor band is preferably applied to the roller or roller core in the form of a slight spiral, so that each sensor differs from every other sensor both in its position in the axial direction of the roller and in its position in the circumferential direction of the roller. Alternatively, the sensors can differ from one another in their position along the roller's rotational axis, and not all sensors can have the same position along the roller's circumferential direction. This makes it possible to ensure that only a few sensors, in particular only one sensor at a time, pass through the treatment gap, so that multiple sensors can use the same signal line. In the case of a spiral, all sensors can be connected to the sensor data unit via the same signal line. A further development of the present invention involves attaching a position sensor to one of the end faces of the roller cylinder to detect the angle of rotation of the roller. The position sensor is preferably an optical sensor. The position sensor and the sensor data unit can be located on the same end face and connected to each other via a data line. A transmission unit on the same end face can then transmit both data derived from the sensor signals and data derived from the position sensor signals to the evaluation unit. This has the advantage that no additional module needs to be installed, as all necessary components can be contained in the signal data unit. A material web processing machine can comprise a sensor roller and a counter-roller arranged parallel to the roller with a treatment gap in between, wherein each of the sensors of the sensor roller can detect the pressure exerted on the sensor roller as it passes through the treatment gap. Based on the detection of the angle of rotation of the sensor roller by the position sensor, the position in the circumferential direction relative to the treatment gap can be determined for each sensor. The sensors can be arranged such that only one of the sensors passes through the treatment gap when the rollers rotate. The same applies if the material web processing machine has a sensor roller with several counter-rollers, wherein a first and a second treatment gap are present.Based on the detection of the rotation angle of the sensor roller by the position sensor, the circumferential position of each sensor relative to the first treatment gap and the second treatment gap can be determined. In this embodiment, the sensors can also be arranged such that only one of the sensors passes through a treatment gap at a time when the rollers rotate. The position sensor reliably determines which treatment gap a sensor is currently passing through. This ensures that sensors are clearly assigned to a treatment gap, eliminating confusion. This is especially important when multiple counter rollers are adjacent to the sensor roller. Example In one example according to the invention, a roller was manufactured that included a roller core, sensors, a shield, and a roller cover surface, in that order. A foil substrate with printed pressure sensors and electrical lines glued to the roller core served as the sensor layer, and an aluminum foil glued to the sensor foil served as the shield. In a comparison example, the same roller was manufactured without aluminum foil. The rollers were tested in a test bench, and pressure signals were recorded. The signals obtained from the roller of the inventive example showed significantly better quality, particularly improved clarity and noise-free performance, than those of the comparative example.

Claims

Patent claims 1. Roller for a material web processing machine, wherein the roller comprises a roller cylinder having a cylindrical roller core, a roller cover surrounding the roller core and a lateral surface, wherein the roller cover consists of one or more roller cover layers in the radial direction and contains sensors, characterized in that an electrically conductive shield is arranged in the radial direction between the sensors and the lateral surface.

2. Roller according to claim 1, wherein the sensors are pressure sensors.

3. Roller according to claim 1 or 2, wherein the sensors are arranged on the roller core or between two roller covering layers.

4. Roller according to one of the preceding claims, wherein the sensors are separated from the shielding by insulation.

5. Roller according to one of the preceding claims, wherein the sensors are applied as a sensor layer to the roller core, to a roller covering layer, to the insulation or to a sensor film.

6. Roller according to one of the preceding claims, wherein the sensors are printed.

7. Roller according to one of the preceding claims, wherein the shield is electrically conductive in that it contains metal-containing or carbon-containing materials.

8. Roller according to one of the preceding claims, wherein the shielding is a roller covering layer containing electrically conductive material, a shielding film, a shielding net or a shielding layer applied to the sensors or the insulation on the sensors.

9. A roller according to claim 8, wherein the shielding layer is printed.

10. Roller according to one of the preceding claims, wherein the roller core is electrically conductive and electrically contacts the shield.

11. A roller according to claim 10, wherein either the shielding is a foil that extends beyond the roller cylinder and electrically contacts the roller core, or the sensors are arranged between the roller core and an electrically conductive roller covering layer, and the roller core and the electrically conductive roller covering layer are in electrical contact between the sensors.

12. Roller according to one of the preceding claims, wherein the signals generated in the sensors are transmitted to a sensor data unit via a signal line.

13. Roller according to one of the preceding claims, wherein on one of the end faces of the roller a position sensor is arranged to detect the angle of rotation of the roller.

14. Roller according to claim 13, wherein the position sensor and the sensor data unit are arranged on the same end face of the roller and are connected to each other via a data line.

15. Material web processing machine comprising a roller according to one of claims 1 to 14 as a sensor roller and a counter-roller arranged parallel to the sensor roller with a treatment gap therebetween, wherein each of the sensors of the sensor roller can detect the pressure exerted on the sensor roller when passing through the treatment gap.