DE102022125630A1 - Arrangement with two rollers spaced apart to form a gap with a gap width measuring system - Google Patents

Abstract

Arrangement with a gap (1) between two rollers (2, 3) with a gap width measuring system, comprising a light source (4) for a coherent light beam (5), a light detector (9) with a receiving surface (10) for the detection of diffraction signals (11) of the light beam only in zeroth and first order starting from the gap, adjustment means (12, 13) for the light source and/or the light detector in at least one lateral adjustment direction oriented skewed to the rollers and/or for the width of the gap between the two rollers, an evaluation unit (14) with stored empirical values and a comparison logic for comparing the diffraction signals with the empirical values and a control unit (15) for the adjustment means, wherein the light source, gap and light detector are arranged in a line in the order mentioned and limits are provided in the comparison logic for the comparison with triggering means for trigger signals for the control unit.

Description

The invention relates to an arrangement with two rollers spaced apart from one another to form a narrowest gap, with a gap width measuring system, in particular for use as an in-line gap measuring system for gap width measurement between the surfaces of two calender rollers in a calender, for example for electrode production for battery cells, with the features of the first patent claim.

The invention is located in the field of measurement technology and is used in particular for quality assurance in production using a calender, e.g. for the manufacture of flat workpieces and sheets such as battery electrodes. In the latter case, the aim is to increase the energy density on the electrodes by precisely adjusting the electrode thickness, which can be indirectly determined by measuring the distance between the calender rollers processing the electrode (gap width measurement). However, this quality assurance measure can also be transferred to other rolling and calendering processes.

The gap width measuring system is part of a rolling process and is intended to ensure a high level of repeatability of the workpiece thickness of the workpieces processed by the rolling process, such as the aforementioned electrodes, in an automated manner. It is intended to provide control signals for setting the gap by adjusting the rollers for an automated rolling process. An absolute measurement of the rolled workpiece thickness is not intended, however, since thermal and mechanical elastoplastic deformations of the workpiece, the rollers and also the roller bearings and suspensions in particular cause a sensitive measurement drift. This is not the aim in an automated manufacturing process.

• Optische Mikrometer:
  • Optische Mikrometerkonzepte, beispielhaft in DE 579 951 A , DE 2 237 329 A oder DE 197 24 364 C2 offenbart, werden zur berührungslosen In-Line-Überwachung von Fertigungsprozessen oder zur In-Line-Qualitätskontrolle eingesetzt.

The following concepts for gap width measurement between two rollers are known from the state of the art:

• Optical micrometers:
  • Optical micrometer concepts, exemplified in DE 579 951 A , DE 2 237 329 A or DE 197 24 364 C2 disclosed are used for non-contact in-line monitoring of manufacturing processes or for in-line quality control.

An optical micrometer comprises a light source, preferably an LED or a laser as a transmitter, a combination of lenses, filters and/or mirrors as transmitter optics and a detector, for example CCD or CMOS chips.

The light from the light source is expanded in the transmitter optics to form a light curtain of parallel beams and is then directed to the detector. If there is a measuring object in the light curtain, it is partially shaded and directed to the detector. The shading provides information about the dimensions and position of the measuring object, as well as slit widths and diameters, for example.

However, the accuracy of optical micrometers depends on the distance between the transmitter and receiver. A resolution of less than 1 µm required in electrode production cannot be guaranteed for an application on calender rolls with diameters of up to 700 mm due to the lack of available installation space.

Capacitive gap sensor:

Furthermore, EN 25 03 130A1 , DE 40 09 544 C1 as well as EP 0 698 428 A Capacitive sensors developed for gap measurement are known. These have two capacitive sensors on the top and bottom that can be inserted into a gap to measure the gap width.

Indirect roll gap measurement:

In an indirect gap width measurement, as in DE 25 43 738 A1 As disclosed, it is not the roll gap that is measured directly, but the thickness of the workpiece deformed in the roll gap or another test material. Such an indirect measurement is not suitable for automating a continuous process flow.

Tactile gap measuring devices:

Several approaches are known for tactile, contact gap measurement.

From the EN 10 2008 023 028 A1 is a hand-held measuring device that was specially developed for measuring the gap width between rollers or other objects with a cylindrical surface. A measuring wedge is connected to the hand-held measuring device via a cable, which in turn is inserted into the gap to be measured. The contact points to the rollers are determined on the wedge surface. The gap is calculated from this and shown on the display of the hand-held device. The resolution is 5 um.

US7,305,894 B2 also discloses a gap measuring device with measuring tips with spring elements and strain gauges with line and point contact. It therefore fulfils the function of a classic feeler gauge.

Furthermore, DE 351 22 90 A1 a measuring device for measuring the gap between two rollers or rolls with a measuring body on which at least three support rollers are provided on one side for aligning the measuring body between the rollers or rolls, which come into contact with a surface of one of the rollers or rolls, the axes of the support rollers being directed perpendicular to the axes of the rollers or rolls and being pivotably mounted on the measuring body.

For use on calenders, the main problem associated with tactile measurement is the sensitive roller surface. This must not be damaged in order to fulfil its function, which is why direct contact should be avoided. In addition, the tactile gap measuring devices mentioned are not suitable for automation or do not meet the requirement of a maximum resolution of 1 µm.

Eddy current sensor-based method:

DE 196 31 438 C2 discloses an example of a contactless eddy current sensor. It uses a coil that generates an electric field when fed with a high-frequency alternating current, which causes eddy currents in conductive measuring objects. This leads to a distance-dependent change in the coil's impedance, which is used to determine the distance. In addition to two eddy current sensors, the system also includes evaluation electronics. The two eddy current sensors are used to measure the distance from the roller shaft to the sensor surface, so that the roller gap can be derived from the difference. In order to prevent the rollers from becoming skewed, such a system is installed on both sides of the roller gap.

However, eddy current sensor-based methods only allow measurements outside the roll gap and thus only serve to indirectly measure the gap width via a calculation and without influences such as roll deflection.

An important quality assurance variable recorded after the calendering process is the material thickness of the workpiece being processed. The influencing process parameters are the height of the roller gap and the force acting on the workpiece in the gap, which can be recorded, for example, via the pressure of the hydraulic cylinders generating the force. The material thickness of the workpiece is influenced by the roller gap dimensions and the force as well as elastic compliances that must be taken into account. The workpiece springs back after the rolling process, so the exact gap height cannot be determined via the material. In addition, the rollers undergo bending due to the forces acting, so that knowledge of the travel paths of the hydraulic cylinders alone is not sufficient to record the material thickness.

Based on this, one object of the invention is to propose an arrangement with two rollers spaced apart from one another to form a narrowest gap with a contactless gap width measuring system without the aforementioned restrictions, whereby the gap width measuring system records the gap width directly on the calender rollers and does not require applications directly between the calender rollers. The course of the roller gap and the absolute gap size should be able to be determined with sufficient accuracy using the measuring system.

The objects are achieved with an arrangement having the features of the first patent claim. Subclaims that relate to these describe advantageous embodiments.

• 1. eine Lichtquelle für einen kohärenten Lichtstrahl mit einem den Querschnitt des Spaltes kreuzenden und bis zu den an den Querschnitt angrenzenden Linien auf den Mantelflächen der beiden Walzen reichenden Wirkbereich:
  • Um Beugungsmuster eines Lichtstrahls an einem Spalt zwischen zwei vorzugsweise um ihre Symmetrie- oder Drehachse rotationssymmetrische Walzen zu erzeugen, muss dieser nicht nur den Querschnitt des Spaltes kreuzen, sondern auch die Spaltweite bildenden an den Querschnitt angrenzenden Linien auf den Mantelflächen der beiden Walzen als Spaltgrenzen mit angeleuchtet werden. Vorzugsweise sind diese beiden an den Querschnitt angrenzenden Linien auf den Mantelflächen der beiden Walzen parallel zueinander ausgerichtet, sodass sich die Spaltweite zumindest im Messbereich, d.h. im Lichtstrahlquerschnitt, in axialer Walzenrichtung unverändert und damit einheitlich ist. Weiter bevorzugt sind die beiden Walzen - wie bei Kalanderwalzen üblich - zylindrisch und wie deren Symmetrie- oder Drehachsen parallel zueinander angeordnet.
  • Eine mögliche Ausgestaltung sieht vor, die Walzen kegelstumpfförmig zu gestalten, wobei deren Symmetrie- oder Drehachsen in einem spitzen Winkel zueinander angeordnet sind. Windschief sind die beiden Walzen sowie deren Symmetrie- oder Drehachsen dabei nicht zueinander angeordnet. Der Querschnitt des Spalts liegt auf einer Ebene, die durch die Symmetrie- und Drehachsen der beiden rotationssymmetrischen Walzen beidseitig des auszumessenden Spalts aufgespannt wird. Die Ebene durchschneidet auch die Walzenoberflächen exakt auf den vorgenannten begrenzenden Linien auf den Mantelflächen der Walzen, die zugleich den kleinsten Abstand der Oberflächen zueinander darstellen und so die zu erfassende Spaltweite begrenzen.
• 2.einen Lichtdetektor mit einer Aufnahmefläche für die Erfassung von Beugungssignalen des Lichtstrahls nur in nullter und erster Ordnung ausgehend vom Spalt:
  • In diesem Bereich zwischen der nullten und ersten Ordnung zeigt sich, dass die an den Walzenoberflächen erzeugten Reflexions- und Streusignale im Verhältnis zu den gebeugten Lichtsignalen am geringsten ausfallen und so in vorteilhafter Weise die Messung am geringsten beeinflussen. Auch weisen die Beugungsmuster in diesem Beugungsbereich absolut die größten Intensitäten auf. Die Aufnahmefläche des Lichtdetektors ist vorzugsweise eben und dabei bevorzugt parallel zum Querschnitt des Spalts ausgerichtet.
• 3.Verstellmittel für die Lichtquelle und/oder dem Lichtdetektor in zumindest eine windschief zu den Walzen orientierte laterale Verstellrichtung und/oder für die Weite des Spalts zwischen den beiden Walzen:
  • Die Verstellmittel ermöglichen einerseits optional eine Höhenverstellung von Lichtdetektor und/oder Lichtquelle und damit der Justierung des Lichtstrahls zwischen diesen Komponenten durch den Spalt, vorzugsweise durch die geometrische Spaltmitte zwischen den beiden Walzen. Ziel ist es, Lichtquelle, Spalt und Lichtdetektor in der genannten Reihenfolge in einer Linie anzuordnen, wobei die Linie gerade durch die vorgenannte Spaltmitte verläuft und durch den Lichtstrahl gebildet wird. Die Höhenverstellung erfolgt folglich in einer windschiefen Richtung, weiter bevorzugt zusätzlich orthogonal zu den Kalanderwalzen, im beispielhaften Falle horizontal ausgerichteter Walzen vorzugsweise in vertikaler Richtung abseits der Walzen. Optional wird vorgeschlagen, die Verstellmittel als Positionsverstellmittel und/oder Winkelverstellmittel mit mehreren Freiheitsgraden für die Lichtquelle und/oder dem Lichtdetektor auszugestalten, die nicht nur die vorgenannte laterale Einstellung des Lichtstrahls auf die Spaltmitte ermöglichen, sondern zumindest auch eine Winkelverstellung des Lichtstrahls zu einem bevorzugt orthogonalen Durchtritt des Lichtstrahls zum Querschnitt des Spalts ermöglicht. Vorzugsweise ist neben der vorgenannten lateralen Verschiebbarkeit auf einer Ebene über die Spaltweite zwischen den Walzen (d.h. auf einer Ebene orthogonal zur Querschnittsfläche des Spalts und orthogonal zu den bevorzugt zueinander parallelen Walzen oder zumindest an den Querschnitt angrenzenden Linien auf den Mantelflächen zumindest einer der beiden Walzen) auch eine Winkelverschiebbarkeit auf derselben Ebene (über die Spaltweite zwischen der Walzen).
  • Die Verstellmittel ermöglichen andererseits optional eine Verstellbarkeit der Spaltweite zwischen den beiden Walzen. Die Verstellung der Spaltweite verläuft über den Spaltquerschnitt gleich, d.h. die bevorzugt parallel zueinander ausgerichteten Walzen bleiben auch während und nach der Verstellung parallel zueinander (parallele Verschiebung). Damit lässt die Dicke eines gewalzten Werkstücks während des laufenden Walzprozess ohne Unterbrechung korrigieren. Eine bevorzugte Ausgestaltung sieht motorische Verstellmittel (Stellantrieb) vor, die an der Symmetrie- oder Drehachse zumindest, vorzugsweise nur einer Walze angreifen und diese gleichförmig lateral verschieben, und zwar beidseitig der Walze. Die Änderung der Spaltweite zwischen den beiden Walzen wird bevorzugt mit Stellantrieben für eine Parallelverschiebung einer Walze umgesetzt.
• 4. eine Auswerteeinheit mit hinterlegten Erfahrungswerten und eine Vergleichslogik für einen Vergleich der Beugungssignale mit den Erfahrungswerten:
  • Die Auswerteeinheit dient der Auswertung der Messwerte aus dem Lichtdetektor, vorzugsweise der Bestimmung der Spaltweite des vom Lichtstrahl angestrahlten Bereichs des Spalts. Ferner dient die Auswerteeinheit der Überwachung der von den Kalanderwalzen bearbeiteten Werkstücke, indem die bestimmten Spaltweiten, zumindest aber die Beugungssignale (Rohmesswerte) als Istwerte mit den hinterlegten Erfahrungswerten (Sollwerte) mittels einer Vergleichslogik vergleichbar sind. Abweichungen zwischen Ist- und Sollwerte sind für eine Auslösung einer Maßnahme wie z.B. eine Alarmauslösung oder eine Verstellung der Kalanderwalzen zueinander heranziehbar. In der Vergleichslogik sind hierzu Limits für den Vergleich mit Auslösemittel für Triggersignale für die Steuereinheit vorgesehen.

To solve the problem, an arrangement with two rollers spaced apart from each other to form a narrowest gap with a gap width measuring system is proposed, comprising the following components:

• 1. a light source for a coherent light beam with an effective range crossing the cross-section of the gap and extending to the lines adjacent to the cross-section on the lateral surfaces of the two rollers:
  • In order to generate diffraction patterns of a light beam at a gap between two rollers that are preferably rotationally symmetrical about their symmetry or rotation axis, the light beam must not only cross the cross section of the gap, but also illuminate the lines that form the gap width and border the cross section on the lateral surfaces of the two rollers as gap boundaries. Preferably, these two lines bordering the cross section on the lateral surfaces of the two rollers are aligned parallel to each other so that the gap width is unchanged and therefore uniform in the axial direction of the rollers, at least in the measuring area, i.e. in the light beam cross section. The two rollers are also preferably cylindrical - as is usual with calender rollers - and arranged parallel to each other like their symmetry or rotation axes.
  • One possible design involves designing the rollers in the shape of a truncated cone, with their symmetry or rotation axes arranged at an acute angle to each other. The two rollers and their symmetry or rotation axes are not arranged relative to each other. The cross-section of the gap lies on a plane that is spanned by the symmetry and rotation axes of the two rotationally symmetrical rollers on both sides of the gap to be measured. The plane also cuts through the roller surfaces exactly on the aforementioned limiting lines on the outer surfaces of the rollers, which at the same time represent the smallest distance between the surfaces and thus limit the gap width to be measured.
• 2.a light detector with a receiving surface for the detection of diffraction signals of the light beam only in zeroth and first order emanating from the slit:
  • In this range between the zeroth and first order, it is evident that the reflection and scattering signals generated on the roller surfaces are the smallest in relation to the diffracted light signals and thus have the least influence on the measurement. The diffraction patterns in this diffraction range also have the greatest absolute intensities. The recording surface of the light detector is preferably flat and preferably aligned parallel to the cross section of the gap.
• 3. Adjustment means for the light source and/or the light detector in at least one lateral adjustment direction oriented obliquely to the rollers and/or for the width of the gap between the two rollers:
  • On the one hand, the adjustment means optionally enable a height adjustment of the light detector and/or light source and thus the adjustment of the light beam between these components through the gap, preferably through the geometric gap center between the two rollers. The aim is to arrange the light source, gap and light detector in the order mentioned in a line, with the line running straight through the aforementioned gap center and being formed by the light beam. The height adjustment therefore takes place in a skewed direction, more preferably additionally orthogonal to the calender rollers, in the exemplary case of horizontally aligned rollers preferably in a vertical direction away from the rollers. Optionally, it is proposed to design the adjustment means as position adjustment means and/or angle adjustment means with several degrees of freedom for the light source and/or the light detector, which not only enable the aforementioned lateral adjustment of the light beam to the gap center, but also at least enable an angle adjustment of the light beam to a preferably orthogonal passage of the light beam to the cross section of the gap. Preferably, in addition to the aforementioned lateral displaceability on a plane across the gap width between the rollers (ie on a plane orthogonal to the cross-sectional area of the gap and orthogonal to the rollers, which are preferably parallel to one another or at least to lines adjacent to the cross section on the lateral surfaces of at least one of the two rollers), there is also an angular displaceability on the same plane (across the gap width between the rollers).
  • The adjustment means also optionally allow the gap width between the two rollers to be adjusted. The adjustment of the gap width is the same across the gap cross-section, i.e. the rollers, which are preferably aligned parallel to one another, remain parallel to one another during and after the adjustment (parallel displacement). This allows the thickness of a rolled workpiece to be corrected without interruption during the rolling process. A preferred embodiment provides motorized adjustment means (actuator) that act on the symmetry or rotation axis of at least, preferably only, one roller and move it laterally at a uniform rate, on both sides of the roller. The change in the gap width between the two rollers is preferably implemented using actuators for parallel displacement of a roller.
• 4. an evaluation unit with stored empirical values and a comparison logic for comparing the diffraction signals with the empirical values:
  • The evaluation unit is used to evaluate the measured values from the light detector, preferably to determine the gap width of the area of the gap illuminated by the light beam. The evaluation unit is also used to monitor the workpieces processed by the calender rollers by comparing the determined gap widths, or at least the diffraction signals (raw measured values) as actual values with the stored empirical values (target values) using a comparison logic. Deviations between actual and target values can be used to trigger a measure, such as activating an alarm or adjusting the calender rollers relative to one another. The comparison logic provides limits for comparison with triggering means for trigger signals for the control unit.

An essential idea of the invention is to project light onto the roller gap, which causes diffraction at the roller gap and creates an interference pattern, which allows conclusions to be drawn about the gap size. In the case of With an optionally proposed design of the coherent light beam leaving the light source as parallel light beams, it is also possible to detect the width of a shadow image created by the gap or a portion of the light beam that passes through undiffracted. Diffraction occurs when light hits edges or narrow constrictions such as lines adjacent to the cross section on the lateral surfaces of the two rollers, created by opaque objects.

Interference is the stationary (constant in time) superposition of electromagnetic waves. According to the superposition principle, the waves add up to form a wave with the corresponding amplitude. The prerequisite for stationary interference is the coherence of the light waves over the entire area in which the waves interfere.

The amplitude of the resulting wave depends mainly on the offset of the wave peaks and troughs, which is usually due to a path difference. There are two borderline cases of interference related to the path difference, between which all mixed forms can occur. One borderline case is constructive interference. The peaks of the individual waves collide and add up to create the largest possible amplitude. This occurs when the path difference is an integer multiple of the wavelength or the phase shift is an integer multiple of 360°. If the path difference is exactly half a wavelength larger or smaller or the phase shift changes by ±180°, the second borderline case, destructive interference, occurs, in which a wave peak and a wave trough overlap, which leads to the waves being canceled out.

Diffraction at a single slit occurs when light rays hit edges or narrow constrictions caused by opaque obstacles. In the context of the invention, these obstacles and constrictions are formed by two rollers spaced apart from each other to form a gap. In the process, parts of the light rays deviate from their actual path. This means that light appears in places that are actually shielded from a ray optical perspective.

If the slit is slightly larger than or the same size as the wavelength of the light, interference occurs due to diffraction of the elementary waves. These form an interference pattern with intensity minima and maxima that depend on the diffraction angle and can be received spatially resolved by the light detector (receiving surface). An interference pattern has a zeroth order diffraction maximum, namely in the continuation of the light beam through the slit cross-section at the level of the mean slit width, also called the perpendicular. On both sides of this, several maxima and minima (diffraction maxima or minima of the first, second, third etc., i.e. nth order, n = integer) extend symmetrically in alternating order and with intensity decreasing from the outside. The propagation of diffracted light rays is orthogonal to the slit.

The interference pattern and the angle α (diffraction angle) between the perpendicular (zero diffraction maximum) and the diffraction maxima starting from the slit depends on the slit width b, the wavelength A and the distance a between the slit and the recording surface.

(Wellenlänge λ, Spaltweite b, Ordnung der Beugungsmaxima x) mit x=1 und zu $$\mathrm{\alpha }=\text{sin}-1\left(\left(\pm 3/2\right)\mathrm{\lambda }/\text{b}\right).$$

The zeroth diffraction maximum lies exactly on the perpendicular of the roller gap (ie at the height of the gap center). The angle α between the perpendicular and the first maximum is given by $$\text{sin}\left(\mathrm{\alpha }\right)=\pm \left(x+0.5\right)\mathrm{\lambda }/b$$

(wavelength λ, slit width b, order of diffraction maxima x) with x=1 and $$\mathrm{\alpha }=\text{sin}-1\left(\left(\pm 3/2\right)\mathrm{\lambda }/\text{b}\right).$$

• - Es wird vorgeschlagen, ausschließlich für die Spaltweitenmessung zwischen zwei Walzen nur die Entfernung zwischen nullten und ersten Beugungsmaxima oder weiter bevorzugt des nullten Beugungsmaximums und der ersten Beugungsminima (zwischen nullten und ersten Beugungsmaxima) heranzuziehen.
• - Alternativ oder ergänzend werden zusätzlich hierzu der Glanzgrad der Mantelflächen in den Wirkbereichen des Lichtstrahls mittels einer Beschichtung mit einer matten Oberfläche oder Antireflexschicht oder Erhöhung der Oberflächenrauigkeit verringert, womit in vorteilhafter Weise auftreffende Lichtstrahlen absorbiert und/oder gestreut anstatt reflektiert werden.
• - Um den Einfluss von Reflexionen oder Streuung an den Mantelflächen der Walzen weiter zu reduzieren, wird vorzugsweise der Einwirkbereich des Lichtstrahls der Lichtquelle auf die Mantelfläche weitgehend begrenzt. Der Lichtstrahl wird bereits vor dem Erreichen des Spaltes begrenzt, vorzugsweise nur auf die den Spalt begrenzenden Linien auf den Mantelflächen. Weiter bevorzugt wird hierzu zwischen Lichtquelle und Spalt eine Blende vorgeschlagen, die die Walzen bis auf die den Spalt begrenzenden Linien möglichst weitgehend vom Lichtstrahl abschattet.
• - Eine weitere Maßnahme sieht eine Ausgestaltung der hinter dem Kalanderspalt angeordneten Komponenten oder Flächen in der Weise (Ausrichtung oder Schwärzung von Reflexionsbereichen) vor, dass an diesen Beugungen höherer Ordnung nicht reflektiert werden können.

A special feature of the claimed arrangement is the limitation of the gap by the lines on the lateral surfaces of the rollers that border the cross section of the gap with a roller radius instead of sharp-edged gap boundaries. A light beam that hits the lines on the lateral surfaces cannot therefore be diffracted unhindered at the line, but reflections and light scattering form on the lateral surfaces of the rollers surrounding the lines, which significantly influence or disrupt the aforementioned interference pattern transmitted to the receiving surface, the larger the diffraction angle. In order to limit this influence, the following measures are proposed:

• - It is proposed to use only the distance between the zeroth and first diffraction maxima or, more preferably, the zeroth diffraction maximum and the first diffraction minima (between the zeroth and first diffraction maxima) for the gap width measurement between two rollers.
• - Alternatively or additionally, the degree of gloss of the lateral surfaces in the effective areas of the light beam is reduced by means of a coating with a matt surface or anti-reflective layer or by increasing the surface roughness, whereby incident light rays are advantageously absorbed and/or scattered instead of reflected.
• - In order to further reduce the influence of reflections or scattering on the lateral surfaces of the rollers, the area of effect of the light beam from the light source on the lateral surface is preferably limited as far as possible. The light beam is limited before it reaches the gap, preferably only to the lines on the lateral surfaces that delimit the gap. It is also preferred to provide a diaphragm between the light source and the gap, which shades the rollers as far as possible from the light beam, except for the lines that delimit the gap.
• - A further measure provides for a design of the components or surfaces arranged behind the calender gap in such a way (alignment or blackening of reflection areas) that higher order diffractions cannot be reflected at them.

A decisive factor in generating the interference spectrum is the coherence of the light. Lasers are particularly well suited as a light source for generating coherent light. Laser light also offers the advantage of good focusability and high intensity, which ensures that the diffraction signals are clearly recognizable by the light detector. The roller gap width is recorded with a resolution in the 0.1 μm range, preferably with a line camera with a recording configuration of 8160 pixels, sensor length 40.8 mm and pixel size 5 pm, which is arranged at a distance of preferably between 1000 and 1500 mm (e.g. 1135 mm) from the gap. The light source can be a diode point laser with a wavelength between 400 and 600 nm (e.g. 450 nm), which must be detectable by the light detector.

In a preferred embodiment, an idealized point-shaped light source, more preferably a laser light source, is proposed, preferably suitable for generating a light beam with a wavelength between 400 and 500 nm. A point-shaped light source is preferably arranged at a distance greater than ten times, more preferably than twenty times the gap width in front of the gap, so that the light beam appears almost parallel across the entire gap width.

An alternative embodiment provides a light source for generating a rectangular light beam cross-section with parallel light beams, with which the entire gap width is captured, including the lines on the lateral surfaces adjacent to the cross-section of the gap. The rectangular light beam cross-section with a length to width ratio of preferably more than 10, more preferably more than 20, is preferably projected onto the cross-section of the gap perpendicular to the adjacent lines. The light beam is preferably generated by a corresponding light source with an attachment optic.

Preferably, the coherent light beam crosses the cross-section of the slit orthogonally.

In a preferred embodiment, the light detector is a camera, for example the aforementioned line camera with a recording configuration of 8160 pixels, sensor length 40.8 mm and pixel size 5 pm, which records the intensity profile of the light spectrum and images it as a photo. In order to avoid falsification of the diffraction signals in the photo or the need for complex conversion and calibration, a camera is preferably proposed without a lens or other optically manipulating upstream elements. The extent of the diffraction spectrum depends on the distance between the rollers. The gap width can be derived from the distance of the interference phenomena using the relationships derived for diffraction at a single gap, whereby within the scope of the invention, preferably only the distance of the zeroth and first diffraction maximum or the zeroth diffraction maximum and the first diffraction minimum are used.

An alternative preferred embodiment provides a line camera or a CCD line detector as a light detector. From the perspective of the light source, the line camera is preferably aligned orthogonally to the slit (like the aforementioned rectangular light beam cross-section), with the lines aligned parallel to the area spanned by the slit and the light beam. The slit and light detector are thus skewed and not parallel to each other in their respective largest geometric extent and thus overlap to form a cross when viewed from the perspective of the light source. The lines of the line camera or CCD line detector are preferably aligned parallel to the largest extent of the slit.

A preferred embodiment provides that at least the two lines adjacent to the cross section on the lateral surfaces of the two rollers are parallel and/or the two rollers are cylindrical and parallel to one another, at least around the area of impact of a light beam. This means that the gap axially to the rollers has a uniform gap width over the entire gap length or around the area of impact of a light beam.

The gap width measuring system described above is an in-line measuring system system, which allows contact-free determination of the width of even very small gaps. A particular advantage is that the light beam and thus in particular the geometric distance, in particular the light source to the gap, can be designed flexibly and also allows longer running lengths, e.g. over 1m up to 20 or 50 m and further. The arrangement offers the possibility of placing the laser and detector almost any distance from the roller pair, since only the obscuring of the light beam (preferably laser line) has to be prevented. This means that the gap width measuring system can also be flexibly integrated into more complex or cramped calender roller arrangements and systems.

The geometric distance from the slit to the light detector can also be designed flexibly. There is basically no limitation to the measuring range with the solution described, since the diffraction effects increase with increasing distance from the calender, i.e. from the slit, and the slit width can therefore be evaluated even more precisely. The only limitation is the reduction in the diffracted light intensity that occurs with increasing distance from the slit.

In comparison with the conventional systems mentioned above, the solution is particularly notable for its expected accuracy advantage. The only limitations here are the resolution and the distance of the light detector from the slit. The resolution of the detector is limited by the current state of the art, although it should be noted that further major improvements are to be expected in the field of industrial cameras.

• 1 eine schematische Darstellung einer Anordnung mit zwei voneinander unter Ausbildung eines Spaltes beabstandeten Walzen mit einem Spaltweitenmesssystem,
• 2 schematisch im Detail den Bereich zwischen Spalt und Aufnahmefläche des Lichtdektors mit Beugungsmuster mit Beugungsmaxima nullter und erster Ordnung,
• 3a und b Draufsichten zweier Anordnungsbeispiele einer Spaltweitenmessung zwischen zwei Kalanderwalzen in einem Kalander beispielsweise für die Elektrodenproduktion für Batteriezellen,
• 4 einen beispielhaften Ablaufplan für eine Einstellung des Lasers sowie
• 5 einen beispielhaften Ablaufplan für eine Ausrichtung und Darstellungsoptimierung einer Messung eines Beugungsspektrums.

The invention is explained in more detail using embodiments, the following figures and descriptions. All features shown and their combinations are not limited to these embodiments and their configurations. Rather, they should be viewed as representative of other possible configurations that are not explicitly shown as embodiments. They show

• 1 a schematic representation of an arrangement with two rollers spaced apart from each other to form a gap with a gap width measuring system,
• 2 schematically in detail the area between the slit and the receiving surface of the light detector with diffraction pattern with zeroth and first order diffraction maxima,
• 3a and b top views of two examples of arrangements for a gap width measurement between two calender rolls in a calender, for example for the electrode production for battery cells,
• 4 an example flow chart for setting up the laser and
• 5 an example flow chart for alignment and display optimization of a diffraction spectrum measurement.

The basic structure acc. 1 shows an arrangement with two rollers 2 and 3 spaced apart from one another to form a gap 1, with a gap width measuring system. The latter comprises a light source 4 for generating a coherent light beam 5 with an effective range that crosses the cross section 6 of the gap and extends to the lines 7 adjacent to the cross section on the lateral surfaces 8 of the two rollers. The gap width measuring system also comprises a light detector 9 with a receiving surface 10 for detecting light beams 11 diffracted at the gap (diffraction signals of the light beam).

Furthermore, adjustment means 12, 13 for the light source or the light detector are arranged in at least one lateral adjustment direction oriented at an angle to the rollers. In the example shown, the rollers 2 and 3 are shown horizontally, and the adjustment directions of the adjustment means 12 and 13, indicated by double arrows, are shown vertically. Light source 4, gap 1 and light detector 9 are arranged in the order mentioned, aligned in a preferably straight line, and can be adjusted to this line using the adjustment means mentioned. Furthermore, an evaluation unit 14 with stored empirical values and a comparison logic for comparing the diffraction signals recorded by the recording surface with the empirical values and a control unit 15 for control signals 17 for starting and/or stopping the adjustment means 12 and 13 are provided. Limits for the comparison mentioned are provided in the comparison logic, which, provided with triggering means, generate trigger signals 16 for the control unit. This allows the adjustment means to adjust the position of the light source and the light detector relative to the slit depending on the detected and evaluated diffracted light rays and to optimize them in favor of an improved signal-to-noise ratio.

Furthermore, the control unit 15 supplies control signals 17 for adjusting means 26 for the width of the gap 1 between the two rollers 2 and 3. In the example shown, these adjusting means comprise an actuator 27 for a preferred parallel displacement of preferably only one roller (for example the lower roller). Within the scope of the invention, the adjusting means also comprise actuators for only the upper roller or also both rollers, depending on the design of the calendering process and the for the required geometric framework conditions. Preferably, the aim is that only the roller that comes into contact with the workpiece passing through, such as the electrode strip of a battery, either with a lower axial load or with a smaller contact area on the outer surface (preferably only the aforementioned adjacent line 7, while the workpiece rests on the outer surface of the other roller beyond the line, for example) is made adjustable by the adjustment means.

Preferably, in addition to the vertical lateral adjustability indicated by double arrows, the adjustment means 12 and 13 also have further adjustment options such as vertical angle adjustability for the light source and/or light detector, which provides further adjustability of the gap measuring system. In particular, the angle of the light beam impinging on the gap cross-section can be optimized from a fundamentally preferred orthogonal irradiation onto the gap cross-section in favor of a further improved signal-to-noise ratio of the received diffracted light signals.

Not shown are optional shading elements such as diaphragms preferably between the light source 4 and the gap 1, which shade the roller surfaces from the light beam except for the area of the lines 7 of the roller surfaces 8 adjacent to the cross section.

2 shows schematically in detail the area between gap 1 between rollers 2 and 3 and recording surface 10 of the light detector with indicated interference pattern 18 with zeroth and first order diffraction maxima 19 and 20 respectively as well as the first order diffraction minima 21. Furthermore, starting from the gap, the angle α between the perpendicular 22 (light beam to the zeroth order diffraction maximum 19) and the diffracted light beam 11, the gap width b as well as the distance a between the gap and the recording surface are also displayed.

Two preferred application examples of the gap width measuring system in a calender are shown in 3a and b. For better clarity, in the two top views, only the lower roller 3 is shown under the electrode strip 23 of the roller pair to be processed (cf. 1 and 2 ). The upper roller, not shown, is arranged congruently above the electrode strip. In the example, the direction of movement of the electrode strip between the pair of rollers runs from left to right (ie in the same direction as the light beam 5) and is marked on it with an arrow. However, a light beam oriented in the opposite direction is also within the scope of the invention. In both application examples, a gap width measuring system is arranged on both sides of the electrode strip, with the diffracted light beams 11 and the plumb line 12 in the extension of the coherent light beam 5 each spanning a plane preferably aligned perpendicular to the electrode strip 23. 3a shows two separate gap width measuring systems, whose measuring signals are preferably forwarded to a common evaluation unit and whose adjustment means are preferably controlled by a common control unit.

In the embodiment according to 3a lateral surface areas with different, preferably reduced gloss levels 24 are specified, which extend in particular over the peripheral areas of the lateral surface illuminated by the light beam. These areas on the lateral surfaces are changed in their gloss level at least in the peripheral effective areas of the light beam by means of preferably a coating with a matt surface or anti-reflective layer or by means of an increase in the surface roughness.

In the embodiment according to 3b the two light beams 5 are fed via a common light source 4 arranged outside the calender by means of mirror elements 25. In this way, not only can both light beams be generated by one light source, but the equipment required can also be reduced due to a decentralized arrangement of the light sources outside the calender. Since the parts of the coherent light beam 5 run parallel before reaching the slit cross-section 6, there is no fanning out; the different running lengths of the two light beams therefore play no role in the slit width measurement. The 3b Adjustment means not further shown include adjustment means for the light source and/or for the mirror elements.

4 shows an example flow chart for adjusting the light sources arranged on both sides of the workpiece. The adjustment is proposed in two blocks 28 and 34, whereby an adjustment aid with a representation of a cross with one bar parallel and orthogonal to the preferably horizontal gap extension is used to adjust the respective focus beam. In the first block, the two coherent beams are aligned before reaching the gap between the rollers, while in the second block, the light beam that has passed through the gap and is diffracted (zero-order diffraction maximum) is aligned.

As in 4 As shown, the first block 28 initially involves activation 29 of the two light sources preset to the slit len and the adjustment means for the light sources. This is followed by a separate adjustment 30 or 31 of the two coherent light beams emitted from these onto the cross arranged in front of the slit, comprising a vertical lateral adjustment and subsequent horizontal angle adjustment of the light sources, followed by a subsequent vertical angle adjustment 32 or 33 of the two light beams via the aforementioned adjustment means. The adjustment aid is arranged between the respective light source and the slit.

In the following second block 34, the light beam that has already passed through the slit and diffracted is adjusted, preferably based on the zero-order diffraction maximum, using adjustment means for the light detector. The adjustment aid with the cross is arranged behind the slit, starting from the respective light source. In a first step, a horizontal angle adjustment 35 or 36 is carried out, followed by a vertical angle adjustment 37 or 38 with subsequent deactivation 39 of the light source and the adjustment means mentioned.

However, it turns out that alignment of the light beam through the gap using the zero-order diffraction maximum becomes increasingly difficult with decreasing gap width b. For this reason, it has proven to be practical to first carry out a preliminary alignment at a gap with an increased gap width. The increased gap width is set by moving only one of the two rollers, preferably by the 1 shown adjustment means for the width of the gap. Accordingly, this is the laser beam which shines through the enlarged gap width just past the fixed, ie non-adjusted roller. Due to the larger gap width, not only does the diffraction spectrum generated change, but also reduces the disruptive influence of this on the detection of the signals required for the adjustment. The adjustment is then reduced with a reduced gap width, if necessary iteratively in several steps with different gap widths.

The aim of the adjustment procedure described above is to ensure that the laser beam is precisely aligned with the cross at two points, i.e. before and after passing through the gap.

5 shows an example flow chart for an alignment and display optimization of a measurement of a diffraction spectrum. This is preceded by a check and, if necessary, adjustment of the setting of the two light sources as previously based on 4 described. A measurement is shown for only one, either the first or second arrangement of light source, slit and recording surface, whereby the sequence of the other arrangement takes place in the same way, preferably synchronously in parallel or at a different time.

In a first step, the recording surface of the light detector is adjusted 40 by means of the adjustment means provided for this purpose to the perpendicular at which the zero-order diffraction maximum is expected (cf. 1 and 2 ). This is followed by a step-by-step vertical movement of the light source using the adjustment means provided for this purpose (preferably in the example - because of the initially unknown gap width - from the fixed roller to the movable roller, i.e. from top to bottom), during which the interference pattern projected onto the recording surface is detected 41 via the light detector. The interference pattern is checked 42 with regard to the detection quality of the gap width b to be monitored. If the quality of the interference pattern is not sufficient (-), the aforementioned detection 41 and check 42 are repeated after previously making a change 43 to the travel parameters, preferably the step size of the light source method and/or changing the travel direction (e.g. from bottom to top), if necessary also other travel parameters, for example an adjustment of the travel path, optical or electronic filtering of the detected signals e.g. for noise suppression or also a limitation of the light beam to the gap by shading elements such as guide plates or diaphragms, in particular between the light source and the gap. If the quality is sufficient (+), a spectrum 44 suitable for recording is available, which can be processed using data technology for continuous monitoring 45 of the slit width b. During the entire process, the quality of the diffraction spectrum must be monitored in the camera's recording program and the alignment adjusted according to the recordings until they are suitable for evaluation.

The recording is made particularly difficult because the guide plates in the calender and also the rollers themselves cause reflections, which can create the impression of a diffraction spectrum if they occur randomly. It has been shown that an overlay with up to three spectra-like phenomena is very likely. When the lifting table was moved, there was generally an overlay of reflections of the spectra of both rollers with the diffraction spectrum at the gap, but also with additional noise signals resulting from reflections on the rollers or other components such as the aforementioned shading elements (e.g. apertures and/or guide plates) or the workpiece.

List of reference symbols:

1

gap

2

upper roller

3

lower roller

4

Light source

5

coherent light beam

6

Cross section of the gap

7

lines adjacent to the cross section

8th

Shell surface

9

Light detector

10

Recording area

11

diffracted light rays

12

Adjustment device (lifting table) for the light source

13

Adjustment device for the light detector

14

Evaluation unit

15

Control unit

16

Trigger signal

17

Control signal

18

Interference pattern

19

Zero-order diffraction maximum

20

First order diffraction maxima

21

First order diffraction minima

22

Lot

23

Electrode band

24

Surface area with different gloss level

25

Mirror element

26

Adjustment means for the width of the gap

27

Actuator

28

first block for flow chart for light source adjustment

29

Activation of the two light sources

30

Adjustment for first light source

31

Adjustment for second light source

32

vertical angle adjustment for first light source

33

vertical angle adjustment for second light source

34

second block for flow chart for light source adjustment

35

horizontal angle adjustment of the first light source

36

horizontal angle adjustment of the second light source

37

vertical angle adjustment of the first light source

38

vertical angle adjustment of the second light source

39

Deactivation of the two light sources

40

Adjustment of the light detector’s receiving surface

41

Detection of the interference pattern projected onto the recording surface

42

Checking the interference pattern

43

Changing the travel parameters

44

spectrum

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 579951 A [0004]
• DE 2237329 A [0004]
• DE 19724364 C2 [0004]
• DE 2503130 A1 [0008]
• DE 4009544 C1 [0008]
• EP 0698428 A [0008]
• DE 2543738 A1 [0009]
• DE 102008023028 A1 [0011]
• US 7305894 B2 [0012]
• DE 3512290 A1 [0013]
• DE 19631438 C2 [0015]

Claims (15)

Arrangement with two rollers (2, 3) with lateral surfaces (8) spaced apart from one another to form a narrowest gap (1) with a gap width measuring system, comprising a) a light source (4) for a coherent light beam (5) with an effective range that crosses the cross section (6) of the gap and extends to the lines (7) adjacent to the cross section on the lateral surfaces (8) of the two rollers, b) a light detector (9) with a receiving surface (10) for detecting diffraction signals (11, 19, 20, 21) of the light beam only in zeroth and first order starting from the gap (1), c) adjustment means (12, 13, 26) for the light source (4) and/or the light detector (9) in at least one lateral adjustment direction oriented obliquely to the rollers and/or for the width of the gap between the two rollers, d) an evaluation unit (14) with stored empirical values and a comparison logic for comparing the diffraction signals with the empirical values and e) a control unit (15) for starting and/or stopping the adjustment means (12, 13, 26), whereby f) the light source (4), slit (1) and light detector (9) are arranged in a line in the order mentioned and g) limits are provided in the comparison logic for the comparison with triggering means for trigger signals for the control unit (15). Arrangement according to Claim 1 , characterized in that the two lines (7) adjacent to the cross section on the lateral surfaces (8) of the two rollers (2, 3) are parallel to each other. Arrangement according to Claim 1 or 2 , characterized in that the two rollers (2, 3) are cylindrical and arranged parallel to each other. Arrangement according to one of the preceding claims, characterized in that the light source (4) is a laser light source, preferably suitable for generating a light beam (5) with a wavelength between 400 and 500 nm. Arrangement according to one of the preceding claims, characterized in that the coherent light beam (5) orthogonally crosses the cross section (6) of the gap. Arrangement according to one of the preceding claims, characterized in that the adjustment means (12, 13) comprise position adjustment means and/or angle adjustment means with several degrees of freedom for the light source (4) and/or the light detector (9). Arrangement according to one of the preceding claims, characterized in that the receiving surface (10) is aligned parallel to the cross section (6) of the gap. Arrangement according to one of the preceding claims, characterized in that the light detector (9) is a line camera or a CCD line detector. Arrangement according to Claim 8 , characterized in that the line camera or the CCD line detector has on the recording surface (10) at least one of a plurality of mutually parallel recording lines, wherein the recording lines are arranged parallel to the main extension of the cross section (6) of the gap. Arrangement according to one of the above Claims 1 until 7 , characterized in that the light detector (9) is a camera. Arrangement according to one of the preceding claims, characterized in that the light detector (9) is dimensioned in its lateral extension such that it is suitable for detecting diffraction signals (11, 19, 20, 21) of the light beam (5) at least of zero order and of first order on both sides thereof. Arrangement according to one of the preceding claims, characterized in that a diaphragm is arranged between the light source (4) and the gap (1), which shades the roller surfaces from the light beam except for the area of the lines (7) of the roller surfaces (8) adjacent to the cross section. Arrangement according to one of the preceding claims, characterized in that the lateral surface (8) of the rollers (2, 3) is changed in its degree of gloss at least in the effective areas of the light beam (5) by means of a coating with a matt surface or anti-reflective layer or by increasing the surface roughness. Arrangement according to one of the preceding claims, characterized in that the receiving surface (10) is suitable for the detection of diffraction signals (11, 19, 20, 21) of the light beam (5) only in zeroth and first order starting from the slit, wherein the first order diffraction signals (20, 21) are only the first order diffraction minima arranged on both sides of the zeroth order diffraction signal (19). Arrangement according to one of the preceding claims, characterized in that the adjusting means (26) for the width of the gap between the two rollers (2, 3) comprises a motor actuator (27) for a parallel displacement of only one roller.

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