EP2981647B1 - Film press - Google Patents

Description

The invention relates to a film applicator for one or two-sided application of a liquid or pasty coating medium on a fibrous web, in particular paper or board web according to the preamble of patent claim 1 and a method according to the preamble of claim 13.

From the prior art, for example the US 5,462,594 A Film applicators are known. Likewise, methods are known in the art to determine the pressure in a roll nip. These are the scriptures EP 0978 589 A2 . WO 96/25288 A1 . WO 2012/113747 A1 . WO 2010/034321 A1 such as DE 20 2008 014477 U1 cited.

It is furthermore known from the prior art to measure the pressure profile in the nip in the case of applicators, through which the fibrous web is guided for applying the fluid or pasty coating medium, such as, for example, coating color or starch. So is, for example, from the DE11 2009 000 095 a coater for the direct application of a coating medium is known in which the pressure profile is measured in a nip formed between a backing roll and an applicator unit to achieve a uniform application of the coating medium on the fibrous web.

In indirect applicators such as. For example, where the coating medium is applied by means of an applicator in excess on an applicator roll and then by means of a nip with the applicator roll forming a doctor element such as a doctor blade or a doctor blade in which to form a film The medium is again partially removed before the film is transferred from the applicator roll in a further nip through which the fibrous web is guided, from the applicator roll on the coming into contact with the applicator roll side of the fibrous web, there is also the problem that the provided on the respective applicator roll film formed as uniformly as possible in the cross-machine direction must be to provide a uniform amount of coating medium in the cross machine direction.

In addition, there is generally the need for the lowest possible rejects at the start of production or resumption of production after web break to set the desired coating amount when using film applicators. High scrap rates up to the reliable setting of the desired coating amount occur especially in film applicators in high-speed paper machines, such as graphic paper or board machines, as they have several breaks of the fibrous web per day and it often several seconds at startup or restart of production takes until the desired amount of coating medium in the cross machine direction is set.

In known from the prior art Filmauftragswerken is trying to date to close the pressure distribution in the first and second nip by the pressure in hydraulic cylinders, by which the two rollers are employed in the film applicator or the doctor element to the respective applicator roll against each other. However, this procedure proves to be often insufficient because of the pressures in the hydraulic cylinders can often be closed only very inaccurate on the true pressure conditions in the first and second nip.

Moreover, with simultaneous coating of the fibrous web on both sides, it is currently not reliably possible to reliably determine the amount of coating medium on each side of the web. With the scanners available today, it is only possible after simultaneous coating on both sides to determine whether the desired amount of coating medium has been applied in total or not. However, it is currently not possible to determine with certainty the currently available film applicators on which side of the fibrous web too much or too little coating medium was applied.

It is the object of the present invention to provide a film applicator and a method for applying a pasty or fluid coating medium, with which the disadvantages described above are eliminated or at least significantly reduced.

The object is achieved by a film applicator with the features of claim 1 and the method with the features of claims 13 and 17th

Characterized in that by means of the elastic cover of one or both applicator roller (s) embedded and arranged in the cross machine direction pressure sensors both in the first nip-nip for transferring the film from the applicator roll on the fibrous web - as well as in the second nip -Nip for forming the Films on the applicator roll - the pressure profile is determined before and / or during the job process, both the pre-metering and the transfer of the film during the job process can be accurately measured and controlled accordingly. Furthermore, by the solution according to the invention already at the start of the coating process, the desired amount of coating medium, i. the film thickness can be set exactly on the applicator roll, and then the application process can be started with the desired coating amount, which is homogeneous in particular in the cross-machine direction, without producing an unnecessary scrap of fibrous web.

Furthermore, it is possible with the inventive solution, with simultaneous two-sided application of coating medium to determine exactly what amount of coating medium is applied to the respective side of the fibrous web.

Furthermore, the solution according to the invention is characterized by its simplicity, as for example. In a film applicator for only one-sided application of coating medium on a fibrous web only through the embedded in the elastic reference of the applicator roll sensors reliable statements about the Pressure distribution can be made in both relevant for the reliable coating nips.

For the purposes of the invention, the term coating is understood to mean not only the application of coating color to the fibrous web, but also any application of a pigment-containing mixture and / or a mixture for sizing, such as starch-containing mixture, to the fibrous web.

Advantageous embodiments and further developments of the invention are specified in the subclaims.

According to a preferred embodiment of the invention, an evaluation unit communicating with the pressure sensors and a display unit communicating with the evaluation unit are provided, wherein the signals coming from the pressure sensors are transmitted to the evaluation unit and further processed in the evaluation unit such that they are used as the pressure profile of the first and the first second nips can be visually displayed by means of the display unit. In this context, it is conceivable, in particular, for the pressure profiles of the first and the second nips to be displayed on one side of the display device, for example in the same graph. Due to the visual representation of the pressure signals as pressure profile (s) it is possible for a machine operator to monitor at a glance both the film formation on the applicator roll and the transfer of the film from the applicator roll to the fibrous web and to intervene in case of deviations from the desired value.

Alternatively or additionally, it is also conceivable that the evaluation unit communicates with an acoustic signal generator which, when the pressure values in the first and / or second nip deviate, emits an acoustic signal characteristic of the respective nip in order to inform the machine operator about possible problems in the application process. By providing acoustic signals, the operator does not need to constantly look at the display, but can devote himself to other tasks and is informed when intervention in the order process or a more accurate tracking of the Order process is necessary. For example, the acoustic signals of the different nips may have different pitches. So then the machine operator can decide which signal an immediate intervention is required and not, depending on which nip for the result in the concrete production process is particularly critical.

Preferably, both rolls of the roll pair are applicator rolls, so that the fibrous web is simultaneously coated on both sides with the coating medium by the thus executed film applicator. In this case, each of the two applicator rollers for the respective provision of a film of the coating medium is assigned in each case an application device and a doctor blade element forming a second nip with the respective applicator roll such that the coating medium present in the form of a film on the one applicator roll of the one applicator roll in the second nip one side of the fibrous web is transferred while the coating medium present on the other applicator roll in the form of a film is transferred from the other applicator roll in the second nip to the other side of the fibrous web.

In this connection, pressure sensors communicating with the evaluation unit are preferably embedded in the elastic relationship between the two applicator rollers, which are arranged side by side in the cross-machine direction, by means of which the pressure profile of at least one second nip, in particular of the second nip, and of the first nip, which adjusts itself in the cross-machine direction, is determined. By ascertaining the pressure profiles of both second nips which are established in the transverse direction of the machine, it is possible in particular to determine the application quantity on each side of the fibrous web individually and independently of one another. This is not possible with the hitherto known scanners, which are arranged according to the simultaneous application of the film applicator on both sides, with which only the entire amount of coating medium applied on both sides can be determined.

It should be noted that the composition of the coating medium applied to one side of the fibrous web is not necessarily the same must be as the composition of the applied to the other side of the fibrous web coating medium.

A further preferred embodiment of the invention provides that at least one of the applicator rollers, in particular both applicator rollers, has or have a signal transmitter communicating with the evaluation unit, which outputs signals characteristic of the rotational position of the applicator roller to the evaluation unit. From this, the evaluation unit can ascertain, in particular, an association of the signals of the pressure sensors during the passage of the pressure sensor (s) through the first and the second nips.

Preferably, the film applicator is operated such that a smaller line force is measured by the pressure sensors in the second nip than in the first nip. Preferably, the line force measured in the second nip is at least a factor of 10, in particular at least a factor of 15 smaller than the line force measured in the first nip. The pressure sensors used are in this case designed in particular such that a line force in the range of 0.01 kN / m to 10 kN / m and in the first nip a line force in the range of 50 kN / m to 200 kN / m can be determined by these in the second nip. If the doctor element is designed, for example, as a doctor blade, then the line force measured by means of the pressure sensors in the second nip can be between 0.5 kN / m and 5 kN / m. If the doctor element is designed, for example, as a doctor bar, then the line force measured by means of the pressure sensors in the second nip can be between 0.01 kN / m and 1 kN / m.

Preferably, the pressure sensors are fiber optic sensors, in particular Bragg grating sensors. Fiber-optic pressure sensors are particularly -bspw. compared to Piezosensoren- by their small dimensions and their very high signal sensitivity. With fiber optic sensors, therefore, extremely small line forces can be measured. Fiber-optic sensors are also characterized by an extremely wide range in signal sensitivity, so that with these both very small and very high line forces can be measured.

According to a specific embodiment of the invention, the one and / or other applicator roll has a roll core, the lateral surface of which is surrounded by the reference, wherein the reference a can be brought into contact with the coating medium functional layer and viewed in the radial direction of the reference between the functional layer and the roll core arranged connecting layer, wherein the pressure sensors are arranged in the connecting layer or in the boundary region between the functional layer and the connecting layer. For the cost-effective simple embedding of the fibers, it has proved to be advantageous to embed the fibers between the two layers. Preferably, the bonding layer is harder than the functional layer, in particular by a factor of 10 to 100 harder than the functional layer. This ensures that a pressure in the nip can spread well as a deformation in the functional layer and thus the pressure sensors can reliably detect the pressure. Due to the harder formation of the connection layer lying below the functional layer, the pressure sensors can be supported on it, whereby the sensitivity of the arrangement is further enhanced.

With regard to possible variants of the specific arrangement of the pressure sensors in relation and the exemplary construction of references of applicator rollers, reference is made to the following Table 1: PU roller Rubber roller Rubber roller Rubber roller Rubber roller Composite roll Functional layer material polyurethane rubber rubber rubber rubber Epoxy resin / fibers thickness 10-20mm 10-20mm 10-20mm 10-20mm 10-20mm 5-15mm hardness 60-100 Shore A 60-100 Shore A 60-100 Shore A 60-100 Shore A 60-100 Shore A 80-90 shore D link layer 1st bonding layer (D = thickness of the layer) Epoxy resin / glass fiber; Thickness = 1-10mm; Hardness = 88-92 Shore D Epoxy resin / glass fiber; Thickness = 1-10mm; Hardness = 88-92 Shore D Hard rubber; Thickness = 1-10mm; Hardness = 88-92 Shore D Hard rubber; Thickness = 1-10mm; Hardness = 88-92 Shore D Epoxy resin / glass fiber; Thickness = 1-10mm; Hardness = 88-92 Shore D Epoxy / glass fiber; Thickness = 1-10mm; Hardness = 88-92 Shore D 2. bonding layer --- Rubber; Thickness = 1-10mm; Hardness = 5-10 P & J Rubber; Thickness = 1-10mm; Hardness = 5-10 P & J Rubber; Thickness = 1-10mm; Hardness = 5-10 P & J Hard rubber; Thickness = 1-10mm; Hardness = 76-86 Shore D --- 3. bonding layer Rubber; Thickness = 1-10mm; Hardness = 5-10 P & J Position sensors Within 1. Connection layer Interface 1. to 2. connection layer Interface 1. to 2. connection layer Within 1st or 2nd connection layer Interface 1. to 2. connection layer Within 1st connection layer

Preferably, all pressure sensors of at least one application roller are arranged along a straight line, wherein the straight line extends in particular parallel to the axis of rotation of the roller. Preferably, in both applicator rollers, the pressure sensors are each arranged along a straight line, in particular along a straight line parallel to the axis of rotation of the respective roller.

According to concrete embodiments of the present invention, the doctor element is, for example, designed as a doctor bar or as a doctor blade, so that the doctor bar or the doctor blade together with the lateral surface of the applicator roll forms the second nip.

According to a further aspect of the invention, a method is proposed for applying a liquid or pasty coating medium on at least one side of a moving fibrous web, in particular paper or board web, in which the coating medium on an applicator roll in front of a second nip formed by the applicator roll and a doctor element applied in excess and partially removed again to form a film of the coating medium on the applicator roll by the doctor element in the second nip and in which the film is subsequently transferred in a first nip from the applicator roll to a side of the fibrous web which comes into contact with it. The method according to the invention is characterized in that the pressure profile which is established in the cross-machine direction in the first nip and in the second nip is determined by means of pressure sensors embedded in relation to the applicator roll.

The pressure profile in the first and second nip is preferably determined by means of pressure sensors embedded in relation to the applicator roll and arranged side by side in the cross-machine direction, which communicate with an evaluation unit.

According to a preferred embodiment of the method, the fibrous web is simultaneously coated on both sides with the coating medium by means of two provided by a pair of rollers and between the first nip forming rollers, wherein the coating medium on the respective applicator roll in front of a respective applicator roll and one of these associated doctor element second Nip applied in excess and for the formation of a film of the coating medium on the respective applicator roll by the respectively associated doctor element in the respective second nip again partially removed and the film subsequently in the first nip of the respective applicator roll on the respective coming into contact with one side of the Fibrous web is transmitted, wherein in the respective first nip and in the second nip in the cross-machine direction adjusting pressure profile embedded in the reference of the respective applicator roll pressure sensor oren is determined.

The advantages of the two aforementioned embodiments of the method according to the invention have already been explained in the same way previously in the description of the corresponding device. Therefore, it should not be further discussed at this point.

Preferably, the pressure profile is determined before and / or during the application of the coating medium to the fibrous web. By determining the pressure profile in the first and second nip before the application process, the amount of coating without the production of rejects can be set exactly in advance become. As a result, the rejection rate is significantly reduced, especially in the case of film applicators working online, ie integrated into the production line of the paper or board machine, since the paper or board machine can go into production directly after start-up without any paper or board web, for example must be driven to the exact setting of the order amount in the pulper.

• Bildung der Faserstoffbahn aus einem Faserstoffgemisch mit einem Stoffauflauf und einer Formierpartie,
• Entwässerung der Faserstoffbahn in einer Pressenpartie,
• Vortrocknung der Faserstoffbahn bis auf einen bestimmten Trockengehalt,
• zumindest mehrmaliger Auftrag eines Beschichtungsmediums mittels dem Verfahren nach einem der vorangehenden Ansprüche,
• Nachtrocknung der beschichteten Faserstoffbahn, wobei

zumindest ein Auftrag eines Beschichtungsmedium on-line in der Maschine erfolgt und die Herstellung der Faserstoffbahn bei einer Maschinengeschwindigkeit von 1200 Meter / Minute oder mehr, insbesondere bei einer Maschinengeschwindigkeit von 1500 Meter / Minute oder mehr erfolgt.Accordingly, according to a third aspect of the invention, a method is proposed for producing a coated fibrous web, in particular paper, board or tissue web, with the following steps:

• Forming the fibrous web from a pulp mixture with a headbox and a Formierpartie,
• Dewatering the fibrous web in a press section,
• Predrying the fibrous web to a certain dry content,
• at least repeated application of a coating medium by means of the method according to one of the preceding claims,
• Post-drying of the coated fibrous web, wherein

at least one application of a coating medium takes place on-line in the machine and the production of the fibrous web takes place at a machine speed of 1200 meters / minute or more, in particular at a machine speed of 1500 meters / minute or more.

Preferably, the fibrous web is a printable fibrous web and the at least one application is applied to one in which a pigment-containing coating medium is applied to the fibrous web.

Figur 1

ein erfindungsgemäßes Filmauftragswerk im Querschnitt,

Figur 2

Signale von einem Sensor beim Durchgang durch den ersten und den zweiten Nip und

Figur 3

eine Papier- oder Kartonmaschine zur Durchführung des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to schematic drawings. Show it

FIG. 1

a film applicator according to the invention in cross-section,

FIG. 2

Signals from a sensor as it passes through the first and second nip and

FIG. 3

a paper or board machine for carrying out the method according to the invention.

The FIG. 1 shows an inventive film applicator 1 for applying a pasty or fluid coating medium 8 on a moving fibrous web 2, in particular paper or board web in cross section.

That in the FIG. 1 shown film applicator 1 has a first nip 3 through which the fibrous web 2 is guided and is simultaneously coated on both sides with the coating medium during the implementation. The first nip 3 is formed by two juxtaposed rollers 4, 5. In the present case, both rollers 4, 5 of the roller pair are application rollers, so that the fibrous web 2 is simultaneously coated on both sides 6, 7 with a coating medium 8 by the thus executed film applicator.

Like from the FIG. 1 can be seen, each of the two application rollers 4, 5 for the respective provision of the coating medium in the form of a film 9, 9 'respectively an applicator 10, 10' and with the respective applicator roll 4, 5 a second nip 11, 11 'forming doctor element 12, 12 'assigned such that the present at the one application roller 4 in the form of a film 9 coating medium 8 is transferred from the one applicator roll 4 in the second nip 3 on the one side 6 of the fibrous web 2, while at the other application roller 5 in Shape of a film 9 'present coating medium 8 is transferred from the other applicator roll 5 in the second nip 3 on the other side 7 of the fibrous web 2. As a result, a double-sided coated fibrous web 2 leaves the first nip 3.

In the present case, an application roller 10, 10 'associated with an applicator roller 4, 5 and the doctor element 12, 12' are arranged on a common support beam 13, 13 '. Furthermore, in the present case, each of the doctor elements 12, 12 'is designed as a doctor bar.

In the present case, a plurality of pressure sensors 14, 14 'arranged side by side in the cross-machine direction are embedded in the elastic covering of each applicator roll 4, 5 (of which in FIG FIG. 1 only one pressure sensor 14, 14 'can be seen), by means of which the pressure profile in the cross machine direction in the first nip 3 and in the two second nips 11, 11' can be determined.

In the present case, the pressure sensors 14, 14 'are designed as fiber-optic sensors, in particular Bragg grating sensors. For the purposes of the invention, it would also be possible to design the pressure sensors 14, 14 'as piezoelectric sensors. In the present case, in each application roller 4, 5 all pressure sensors 14, 14 'are arranged along a straight line running parallel to the axis of rotation of the rollers.

In the in the FIG. 1 1 is the line force measured by the pressure sensors 14, 14 'in the second nips 11, 11' as the line force measured in the first nip 3, wherein a line force in the region by the pressure sensors 14, 14 'in the second nip 111, 11' from 5kN / m to 50kN / m and in the first nip a line force in the range of 60kN / m to 200kN / m is determined.

Each of the applicator rollers 4, 5 has a roller core 20, 20 ', the lateral surface of which is surrounded by the cover, the cover being a functional layer 21, 21' which can be brought into contact with the coating medium 8 and a functional layer 21 viewed in the radial direction of the cover , 21 'and the roller core 20, 20' arranged connecting layer 22, 22 ', wherein the pressure sensors 14, 14' present in the interface between the functional layer 21, 21 'and the connecting layer 22, 22' are arranged. In the present exemplary embodiment, the functional layer 21, 21 'is made of polyurethane with a hardness in the region of 80 Shore A, whereas the connecting layer 22, 22' is a fiber composite layer of epoxy resin and glass fibers with a hardness of 90 Shore D. Thus, the connecting layer 22, 22 ' harder than the functional layer 21, 21 '.

When the pressure sensors 14, 14 'pass through the respective nip 3, 11, 11', each of the pressure sensors generates one or more signals corresponding to the pressure action in the nip, which signal is transmitted to an evaluation unit 15. present is the evaluation unit 15 completely outside the applicator rollers 4, 5 arranged. But there are also designs in which parts of the evaluation are rotatably connected to the respective roller and other parts are arranged outside the roller, that are not rotatably connected to the respective roller. In the present case, the signals of the pressure sensors 14, 14 'are transmitted wirelessly to the evaluation unit.

The signals coming from the pressure sensors 14, 14 'are then further processed in the evaluation unit 15 in such a way that they can be displayed visually as the pressure profile 16 of the first nip and 17, 17' of the two second nips 11, 11 'by means of a display unit 18.

In order to determine the rotational position of the two applicator rollers 4, 5, a signal transmitter 19, 19 'communicating with the evaluation unit 15 is provided in each of the applicator rollers 4, 5, which outputs characteristic signals to the evaluation unit 15 for the rotational position of the respective applicator roller 4, from which the evaluation unit 15 determines an assignment of the signals of the pressure sensors 14, 14 'to the passage of the respective pressure sensors 14, 14' through the first nip 3 and the respective second nip 11, 11 '. In the present case, the signal transmitters 19, 19 'are designed according to the Hall sensor principle.

The FIG. 2 shows for several revolutions of one of the applicator rollers 4, 5, the signals that are measured by the pressure sensors 14, 14 'when passing through the first nip 3 and by one of the second nips 11, 11'. Here, the signals A are generated by the pressure sensors 14, 14 'as they pass through the second nip 11, whereas the signals B are generated by the pressure sensors 14, 14' as they pass through the first nip 11. The line force at the pressure sensor 14, 14 'is proportional to that in the FIG. 2 shown peak-to-peak values of the signals A, B of the pressure sensors 14, 14 '. With regard to the details for evaluating the signals of the pressure sensors 14, 14 ', reference is made to the German patent application no. 10 2012 206 689.6 the content of which is fully incorporated into this application in this context.

• Bildung der Faserstoffbahn 2 aus einem Faserstoffgemisch mit dem Stoffauflauf 23 und der Formierpartie 24,
• Entwässerung der Faserstoffbahn in der Pressenpartie 25,
• Vortrocknung der Faserstoffbahn bis auf einen bestimmten Trockengehalt in einer Vortrockensektion der Trockenpartie 26, 27,
• Vorglätten der vorgetrockneten Faserstoffbahn in einem Glättwerk 31,
• beidseitiger Auftrag eines pigmenthaltigen Beschichtungsmediums 8 mittels einem aus der Figur 1 bekannten Filmauftragswerk 1,
• Trocknung der beidseitig beschichteten Faserstoffbahn 2 mittels eines Infrarot-Trockners 28 und
• zumindest einseitiger Auftrag eines pigmenthaltigen Beschichtungsmediums 8 mittels einem aus der Figur 1 bekannten Filmauftragswerk 1 sowie wieder
• Trocknung der beschichteten Faserstoffbahn 2 mittels eines weiteren Infrarot-Trockners 29 und
• Aufrollung der Faserstoffbahn2.

The FIG. 3 shows a machine for producing a coated fibrous web, in particular paper or board machine with a headbox 23, a Formierpartie 24, a press section 25, a drying cylinder 26 comprising drying section 27 and a plurality of applicators 1, both of which Filmauftragswerke corresponding to that in the FIG. 1 are shown. With the in the FIG. 3 A machine for producing a coated fibrous web 2 can be made as follows:

• Forming the fibrous web 2 from a pulp mixture with the headbox 23 and the Formierpartie 24,
• Dewatering the fibrous web in the press section 25,
• Predrying the fibrous web to a certain dry content in a pre-drying section of the dryer section 26, 27,
• Pre-smoothing the predried fibrous web in a calender 31,
• two-sided application of a pigment-containing coating medium 8 by means of one of FIG. 1 known film applicator 1,
• Drying of the coated fibrous web 2 on both sides by means of an infrared dryer 28 and
• at least one-sided application of a pigment-containing coating medium 8 by means of one of FIG. 1 known Filmauftragswerk 1 and again
• Drying of the coated fibrous web 2 by means of another infrared dryer 29 and
• Roll-up of the fibrous web2.

As from the representation of FIG. 3 is apparent, the order of the coating medium 8 takes place by means of both film applicators 1 on-line in the machine. Further, in the illustrated machine, the production of the fibrous web is performed at a machine speed of 1200 meters / minute or more, particularly at a machine speed of 1500 meters / minute or more.

Claims (19)

1. Film application unit for applying a pasty or fluid coating medium to a running fibrous web, in particular a paper or cardboard web, having a first roller pair forming a first nip through which the fibrous web is guided, wherein at least one of the rollers of the roller pair is an application roller by way of which the coating medium which is provided in the form of a film on the application roller in the first nip is transferable from the application roller to a side of the fibrous web that comes into contact with said application roller, wherein the application roller is assigned an application installation and a doctor element in such a manner that prior to the first nip the coating medium by means of the application installation is first excessively applied to the application roller and then by means of the doctor element which together with the application roller forms a second nip is again partially removed in the second nip in order for the film to be configured, characterized in that a plurality of pressure sensors, which in the machine cross direction are disposed beside one another and by means of which the pressure profile in the machine cross direction in the first and in the second nip is ascertainable, are embedded in the elastic covering of the application roller.
2. Film application unit according to Claim 1, characterized in that an evaluation unit which communicates with the pressure sensors, and a display unit which communicates with the evaluation unit are provided, wherein the signals emanating from the pressure sensors are transmitted to the evaluation unit and are further processed in the evaluation unit in such a manner that said signals by means of the display unit are capable of being visually displayed as the pressure profile of the first and of the second nip.
3. Film application unit according to one of the preceding claims, characterized in that both rollers of the roller pair are application rollers, wherein, in order for a film of the coating medium to be in each case provided on the respective application roller, both application rollers are assigned in each case one application installation and one doctor element which together with the respective application roller forms a second nip, such that the coating medium which is present in the form of a film on the one application roller in the second nip is transferable from the one application roller to the one side of the fibrous web, and in that the coating medium which is present in the form of a film on the other application roller in the second nip is transferable from the other application roller to the other side of the fibrous web.
4. Film application unit according to one of the preceding claims, characterized in that pressure sensors which in each case communicate with the evaluation unit are embedded in the elastic covering of both application rollers and in the machine cross direction are disposed beside one another, and the pressure profile in the machine cross direction by means of the pressure sensors and of the evaluation unit is ascertainable in at least one of the first nips, in particular in both second nips, and in the first nip.
5. Film application unit according to one of the preceding claims, characterized in that at least one of the application rollers has a signal generator which communicates with the evaluation unit and which emits signals which are characteristic of the rotational position of the application roller to the evaluation unit and from which the evaluation unit ascertains an assignment of the signals of the pressure sensors to the passage of the pressure sensor(s) through the first and the second nips.
6. Film application unit according to one of the preceding claims, characterized in that the pressure sensors are fiber-optic sensors, in particular Bragg grating sensors.
7. Film application unit according to one of the preceding claims, characterized in that a lower line force is measured by the pressure sensors in the second nip than in the first nip.
8. Film application unit according to one of the preceding claims, characterized in that a line force in the range of 5 kN/m to 50 kN/m is ascertainable by the pressure sensors in the second nip, and a line force in the range of 60 kN/m to 200 kN/m is ascertainable in the first nip.
9. Film application unit according to one of the preceding claims, characterized in that the one and/or other application roller(s) have/has a roller core the sleeve surface of which is surrounded by the covering, wherein the covering comprises a functional layer which is capable of being brought into contact with the coating medium, and when viewed in a radial direction of the covering a connecting layer which is disposed between the functional layer and the roller core, and the pressure sensors are disposed in the barrier region between the functional layer and the connecting layer.
10. Film application unit according to one of the preceding claims, characterized in that the connecting layer is harder than the functional layer, in particular is harder than the functional layer by a factor of 10 to 100.
11. Film application unit according to one of the preceding claims, characterized in that the doctor element is configured as a doctor bar or a doctor blade.
12. Film application unit according to one of the preceding claims, characterized in that all pressure sensors are disposed along a straight line which runs parallel with the rotation axis of the rollers.
13. Film application unit according to one of the preceding claims, characterized in that the coating medium is a pigment-containing or starch-containing mixture.
14. Method for applying a liquid or pasty coating medium to at least one side of a running fibrous web, in particular a paper or cardboard web, in which method the coating medium prior to a second nip which is formed by the application roller and a doctor element is excessively applied to an application roller and in order for a film of the coating medium to be configured on the application roller is again partially removed in the second nip by the doctor element, and the film subsequently in a first nip is transferred by the application roller to a side of the fibrous web that comes into contact therewith, characterized in that a plurality of pressure sensors, which in the machine cross direction are disposed beside one another, are embedded in the elastic covering of the application roller, and the pressure profile which is established in the machine cross direction in the first nip and in the second nip is ascertained by means of the pressure sensors which are embedded in the covering of the application roller.
15. Method according to Claim 14, characterized in that the pressure profile is ascertained prior to and/or during application of the coating medium to the fibrous web.
16. Method according to one of preceding Claims 14 to 15, characterized in that the pressure profile in the first and second nips is ascertained by means of pressure sensors which are embedded in the covering of the application roller, which in the machine cross direction are disposed beside one another, and which communicate with an evaluation unit.
17. Method according to one of preceding Claims 14 to 16, characterized in that the fibrous web is simultaneously coated with the coating medium on both sides by means of two application rollers which are provided by a roller pair and between them form the first nip, wherein the coating medium is excessively applied to the respective application roller prior to a second nip which is formed by the respective application roller and a doctor element assigned thereto, and in order for a film of the coating medium to be configured on the respective application roller, is again partially removed in the respective second nip by the in each case assigned doctor element, and the film subsequently in the first nip is transferred by the respective application roller to that one side of the fibrous web which in each case comes into contact with said respective application roller, wherein the pressure profile which is established in the machine cross direction in the respective first nip and in the second nip is ascertained by means of pressure sensors which are embedded in the covering of the respective application roller.
18. Method for manufacturing a coated fibrous web, in particular a paper, cardboard, or tissue web, the method comprising the following steps:

    - forming the fibrous web from a fibrous mixture, using a headbox and a forming section;

    - dewatering the fibrous web in a pressing section;

    - pre-drying the fibrous web to a specific dry content;

    - an at least multiple application of a coating medium by means of the method according to one of preceding Claims 14 to 18;

    - post-drying the coated fibrous web, wherein at least one application of a coating medium is performed in-line on the machine and manufacturing of the fibrous web is performed at a machine speed of 1200 meters/minute or more, in particular at a machine speed of 1500 meters/minute or more.
19. Method according to Claim 18, characterized in that the fibrous web is a printable fibrous web, and a pigment-containing coating medium is applied to the fibrous web at least in one application.

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