EP1392918B1 - Device, method and arrangement for pressing two axis-parallel rollers approachable to one another in a device for producing and/or treating a web of material - Google Patents

Abstract

A parallel double-roller (14, 16) assembly spreads a coating of liquid or paste to a web (10) of paper or carton. The assembly has a jack (26) which applies a converging force to the rollers and a sensor (36) determining the force. The sensor (36) is esp. positioned in the compression force transmission system between the jack and rollers. The system has two or more compression transmission paths each incorporating a pressure sensor. The compression applied by each jack is individually variable. One of the rollers is fixed but rotates within a machine frame. The second roller rotates within the frame but moves in response to pressure from the jack (26) applied through a lever.

Description

The invention relates to the mutual pressing of a pair of two axially parallel rolls in a device for producing or / and treating a moving material web.

Roller pairings are frequently used in machines on which paper, board or other material webs are produced or treated. By means of such roller pairings material webs are, for example, calendered, coated or printed. Regular attention is paid to the pressure applied between the rollers of the pairing. The adherence to a certain pressing force is usually of decisive importance for the result of the treatment of the material web, be it, for example, the calendering result in calendering or the weft result when applying a glue or a pigmented coating color.

Out EP 0 978 589 A2 It is known to detect the force applied between a pair of rollers pressing force and in particular their axial distribution by means of sensors which are embedded in one of the rollers near the surface and in the mantle of the roller or a coating applied to the jacket. Although in this way the line pressure between the rollers can be detected very accurately and, in the event of deviations from the desired values, a corresponding activation of suitable force devices can take place in order to effect a stronger or weaker contact pressure of the rollers. The embedding of the sensors in the roll body has admittedly the disadvantage that this complicates the production of the roller and expensive. In addition, it must be taken into account that, from time to time, it may be necessary to abrade the outer functional layer of the roll in order to eliminate damage in the roll surface. If the sensors are arranged close to this functional layer or even embedded in it, this can mean that the outer layer of the roller is available only for a small portion of its thickness for the abrading and, accordingly, an early replacement of the roller may be required.

The object of the invention is therefore to develop a device of the generic type so that the above problem can be avoided.

By laying the sensor means out of the roll bodies of the rolls, the manufacture of the rolls is less complicated and costly. Because no sensors must be embedded in the roll body, the possibility opens up to resort to standard rollers. Also, the occasional grinding of the rollers can be made so regardless of the sensor means. Nevertheless, furthermore, the pressure prevailing between the rollers can be measured directly, since the sensor means are arranged in the transmission path of the pressing force.

If a roll body of a roll is mentioned here, this essentially means the barrel-shaped (usually hollow-cylindrical) barrel-shaped structure usually coated with a covering of elastic or hard material, which forms the actual roll. Bearing journals that serve to rotatably support the roller, are not counted to the roller body.

In principle, it is conceivable that the force provided by the force-generating means is transmitted substantially completely on the force transmission path extending over the rollers as the only force transmission path. However, provision may also be made for the force provided by the force-generating means to branch to the force transmission path extending over the rollers and at least one further force transmission path. In this case, the sensor means will be arranged in the force transmission path passing over the rollers after the branching thereof from the further power transmission path.

If a plurality of parallel power transmission paths are provided for the force provided by the force generating means, there is an advantageous possibility for influencing the effective pressing force between the rollers in that the ratio of the forces transmitted via the various power transmission paths is variable. For this purpose, stop means are preferably arranged in the further force transmission path, which are adjustable to change the ratio of the forces transmitted via the various power transmission paths.

In principle, it suffices to measure the transmitted force only at one point along the force transmission path extending over the rollers. This point may be before the roll body of a first of the two rolls or after the roll body of a second following of the two rolls. But it is also possible to make a force measurement at the same time at several points along the running over the rollers power transmission path. For this purpose, the sensor means may comprise at least one sensor arranged in front of the roller body of the first roller and at least one sensor arranged after the roller body of the second following roller. In this case, it is advantageous that the measured values supplied by the various sensors can be compared with one another, so that the sensors, so to speak, control each other. The safety and accuracy of the force measurement can be increased.

In a preferred embodiment of the invention, one of the two rollers is mounted on a stand relative to this stationary, but rotatably mounted on the stand, a roller rotatably supporting the other roller bearing lever which is pivotable relative to the stand for mutual approach of the two rollers , The force generating means engage the bearing lever in this embodiment.

The sensor means may then comprise at least one sensor which is mounted on the bearing lever or the stand. When designing the bearing lever or stator and the positioning of the sensor, it must be ensured that the sensor detects exactly that component of force that is introduced into the roller pairing.

Alternatively or additionally, the sensor means may comprise at least one sensor which is arranged in a bearing region of one of the rollers. For example, the sensor may be mounted on a journal of the respective roller. But it can also be provided with a bearing a journal of the respective roller enclosing bearings with the sensor. In the latter case, the sensor may be integrated in the rolling bearing or mounted on an outer ring of the bearing. It is also conceivable that the sensor is mounted on a bearing housing, in which a bearing journal of the respective roller enclosing rolling bearing is added.

Furthermore, the sensor means may alternatively or in addition to the above-mentioned possible sensor locations include at least one sensor which is housed in a separately manufactured sensor module, said sensor module between the stator or the bearing lever and a bearing assembly for a bearing pin on the stand or the Bearing lever held roller is installed. Such sensor modules are commercially available in the form of mechanically self-contained load cells. For storage of the rollers can then be used on standard, standardized bearing kits, which has a cost-reducing effect.

The sensor means may comprise at least one tensile and / or pressure-sensitive element, in particular a strain gauge, for force sensing. Such sensor elements are known in a variety of configurations and have proven to be robust, reliable and precise in practical use. Of course, sensor elements based on other measuring principles can also be used, as long as they are able to provide a sensor signal representative of the pressure force between the rollers.

Expediently, an electronic control unit which responds to the sensor means and controls the force generating means is provided, which is set up for the controlled maintenance of a predetermined desired value of the pressure force between the rollers. In this case, the force generating means in the region of both axial ends of the roller pairing may each comprise at least one independently controllable, in particular hydraulic force device and the sensor means for independent detection of the pressing force in both axial end portions of the roller pairing. The control unit can then be set up to control the force devices in such a way that over the axial extent of the roller pairing a substantially constant line pressure between the rollers results, as is desired in numerous applications. Nevertheless, it is not impossible to program the control unit in such a way that different values of the line pressure result in the two axial end areas of the roller pairing.

The device according to the invention is preferably intended for use in a coating unit, in which the material web is passed between the two rollers and at least one of the rollers serves to transfer the application medium to the material web.

The invention is based on the solution of the above-mentioned object of a method for adjusting the contact pressure of two approachable axially parallel rolls in a device for producing or / and treatment of a moving material web, wherein at least one of the rollers has a radially elastic roll cover.

According to the invention it is provided that distance sensor means detect the actual value of the axial distance, a distance-force characteristic is determined for the pair of rollers, which represents a relationship between the mutual center distance of the two rolls and the force transmitted between the two rollers contact pressure, and that Achieving a desired pressing force of the rollers in the operating mode of the device, an associated target value of the axial distance is determined from the distance-force characteristic and adjusted at the roller pairing.

The invention deviates from the previous procedure in that it does not detect the pressure force transmitted between the rollers by means of pressure sensors and effects a control of force devices which is dependent on the sensor signals. Instead, it makes use of the spring characteristics of the elastic cover of at least one of the rollers. It is based on the knowledge that - due to the flattening of the cover when pressing the rollers - the mutual distance between the axes of the two rollers changes depending on the pressure prevailing between the two rollers contact pressure. It can therefore be determined a "spring characteristic" for the roller pairing, which is the transmitted between the rollers pressing force with respect to the mutual center distance of Rolls sets. If then in the working mode of the machine in which the roller pairing is used, a certain pressing force can be achieved, it must only be looked up in the spring characteristic, which associated center distance must be set on the roller pairing to obtain ebendiese pressing force.

The embedding of pressure sensors in one of the rolls is not required in the inventive solution. Therefore, common standard rollers can be used, which are considerably less expensive. The occasional grinding of the rolls can also be carried out without difficulty, without the risk of damaging embedded sensors in the rolls by this grinding.

If it is mentioned here that the distance-force characteristic provides different values of the center distance for different values of the pressing force, then it is understood that the term center distance is only representative of any size, that for the mutual center distance of the two Rolls is representative. For example, the distance-force characteristic instead of directly the distance between the axles can provide a position indication for an adjustable component influencing the center distance of the rollers.

In principle, it is not excluded to derive the distance-force characteristic theoretically and to represent it in a formula. In general, however, it will be easier to perform measurements in a calibration phase of the device to determine the distance-force characteristic. These measurements can be carried out in particular with rotating rolls, since it has been shown that the flexing operations occurring during rotation in the elastic roll cover can influence the spring characteristic of the roll pairing. Therefore, it is recommended to determine the distance-force characteristic under conditions that are at least close to the conditions in the working mode of the machine.

Appropriately, to determine the distance-force characteristic at least two pairs of values of center distance and pressure force for different values of the pressing force will be determined. It is advantageous if a zero point and an end point of the spring characteristic of the roller pairing are obtained by measurement. For zero point determination, one of the pairs of values for an approaching position of the rolls can be determined, in which the rolls are substantially brought together until mutual contact is established, but substantially no pressing force is transmitted between the rolls. The end point determination can be carried out by determining one of the value pairs for a pressing force transmitted between the rollers, which at least approximately corresponds to a maximum pressing force for which the device is designed.

It is basically conceivable to substantially completely absorb the spring characteristic. However, it saves effort if only a few points of the spring characteristic curve are determined and if it is interpolated between these points. To a good approximation, it can often be assumed that the roller pairing shows a linear spring behavior. Very easily, the spring characteristic can then be determined by linear interpolation.

As already explained at the outset, reworking of the roll cover will occasionally be necessary in order to completely smooth the roll surface again and to clear it of defects. For this purpose, the roll cover is abraded until the roll surface is again perfect. Of course, the old spring characteristic can no longer be valid for the abraded roll cover. It is therefore advisable to determine the distance-force characteristic again after grinding the roller cover.

It is conceivable to set the setpoint value of the axial spacing determined from the spring characteristic curve once in the sense of a control, for example by means of a path-controlled actuator, however, its compliance in the working operation of the device no further check. However, then static or dynamic distance fluctuations of the axes of the rollers remain unrecognized, which can be caused in the working mode of the machine, for example, by heat deformation, tension or contact vibrations. In order to be able to take account of such influences, a control can be established in which the actual center distance of the rollers is detected by sensors during operation of the device and adjusted to the desired value of the axial distance.

Often the center distance of the rollers in the region of both axial ends of the roller pairing will be independently adjustable. Although this opens up the possibility of adjusting a line pressure linearly changing in the axial direction between the rollers, it will be desirable for most applications to adjust the center distances in the two axial end regions of the roller pair such that a substantially over the axial extent of the roller pairing constant line pressure between the rollers results.

In a preferred embodiment, the inventive method is carried out in a machine for coating a paper or board web, wherein the paper or board web is passed between the rollers and at least one of the rollers for transferring a liquid to pasty application medium on the paper or board web is used ,

The invention further relates to an arrangement for the mutual pressing of two axially parallel rolls in a device for producing or / and treating a moving material web, wherein at least one of the rollers has a radially elastic roll cover, comprising adjusting means, by means of which the two rolls along an approach approach approachable and are adjustable in an approach state, in which a pressing force between the rollers is transmitted with distance sensor means according to claim 1. This arrangement should be suitable for carrying out the method according to claim 26. According to the invention, the arrangement comprises a memory unit for storing a pre-determined distance-force characteristic for the roller pairing, which represents a relationship between the mutual center distance of the two rollers and the pressure force transmitted between the rollers, and a control unit connected to the memory unit and controlling the actuating means , which is adapted to determine a desired pressure force of the rollers from the distance-force characteristic to determine an associated target value of the axial distance and to effect the setting of this target value at the roller pairing. With regard to the advantages of the arrangement according to the invention, reference is made to the above discussion of the method according to the invention.

The arrangement may comprise sensor means for detecting the actual center distance of the rollers, wherein the control unit is responsive to the sensor means and adapted for the controlled maintenance of the desired value of the axial spacing.

The center distance of the rollers may be independently adjustable in the region of both axial ends of the roller pairing. The control unit is then preferably designed for setting the center distances in the two axial end regions of the pair of rolls so that a substantially constant line pressure between the rollers results over the axial extension of the pair of rollers.

One of the first rollers may be held on a roller carrier displaceable relative to the second roller along the approach path. The adjusting means may then comprise force-generating means engaging the roller carrier for introducing a force generating the pressing force into the roller carrier.

The force provided by the force generating means may substantially fully serve to generate the pressing force. The provided force is transmitted essentially on a single power transmission path which extends over the two rollers. Alternatively, the force provided by the force generating means may also be branched, to a first force transmission path transmitting the pressure force between the two rollers and at least one second force transmission path. In this embodiment, a portion of the force provided by the force generating means is transmitted through the pair of rollers in the first transmission path and another portion of that force is transmitted on the at least one second transmission path.

If the force provided by the force generating means is transmitted substantially completely in a single force transmission path extending over the two rolls, a change in the center distance of the two rolls and thus a change in the pressing force between the two rolls can be brought about by corresponding activation of the force generating means become. If a plurality of parallel power transmission paths are provided, to which the force provided by the force generating means divides, there is an advantageous possibility for influencing the pressing force between the rollers in that the ratio between the force transmitted on the first power transmission path and that on the at least one second power transmission transmitted force is variable. This can be realized for example by stop means, which are arranged in the at least one second power transmission path and are adjustable to change the ratio of the forces transmitted in the different power transmission paths. The position of the stop means then serves as a size which is representative of the mutual center distance of the rollers. It only needs to be determined which position of the sling means which value of the center distance the rolls corresponds. If this relationship is known, only the stop means must be brought into the appropriate position to achieve a desired pressing force between the rollers.

The stop means may comprise at least one stop arranged for common movement with the first roller along its approach path to the second roller, and at least one counter stop stationary with respect to the axis of the second roller. In order to influence the force relationships between the various power transmission paths, then at least one of the components: stop and counter stop can be adjusted.

The arrangement according to the invention is preferably intended for use in a machine for coating a paper or board web. The paper or board web is preferably passed between the rollers, wherein at least one of the rollers for transferring a liquid to pasty application medium is used on the paper or board web.

Fig. 1

schematisch eine Gesamtansicht eines Streichwerks mit einer Sensoranordnung zur Detektion der zwischen einer Walzenpaarung herrschenden Linienpressung,

Fig. 2

schematisch einen Lagerbereich einer der Walzen zur Erläuterung von Varianten der Sensoranordnung.

Hereinafter, some embodiments of the invention will be described in more detail with reference to the accompanying drawings. In it represent:

Fig. 1

1 is a schematic view of a coating unit with a sensor arrangement for detecting line pressure prevailing between a pair of rollers.

Fig. 2

schematically a storage area of one of the rollers for explaining variants of the sensor arrangement.

This in Fig. 1 brushing shown used for two-sided indirect application of a liquid to pasty application medium, such as a pigment-containing coating color or a surface glue on a running Material web 10 made of paper or cardboard. The material web 10 moves through an application nip 12 referred to in the jargon as nip, which is formed between two adjacently arranged rollers 14, 16. The rollers 14, 16 are arranged with their axes 18, 20 parallel to each other. One of the rollers - here the roller 16 - serves as a so-called fixed roller, while the other roller - here the roller 14 - forms a so-called moving roller. This means that the roller 16 is rotatable about its axis 20, but otherwise positionally fixed, while the moving roller 14 is approachable to the fixed roller 16 and removable from this. The fixed roller 16 is held for this purpose on a firmly anchored to the ground machine stand 22. A pivoting mounted on the machine stand 22 bearing lever 24 carries the moving roller 14. To pivot the bearing lever 24 and thus to approach and pressing the moving roller 14 to the fixed roller 16 is a power device assembly 26 which preferably at least one hydraulic piston-cylinder Aggregate 28 in the region of both axial ends of the roller pairing 14, 16 has. The power device assembly 26 is controllable by an electronic control unit 30 of the coating unit, wherein suitably an independent controllability of the individual force devices of the power device assembly 26 will be given.

Each of the rollers 14, 16 has in the illustrated embodiment, an elastic roll cover 128 and 130, which consists for example of a rubber or plastic material. In the context of the invention, it is of course sufficient if only one of the rollers 14, 16 has an elastic cover. The other of the rollers can then wear, for example, a steel or chrome sheath.

The coating medium with which the material web 10 is to be coated is first applied to the rollers 14, 16 in a manner not shown in detail, but in a generally known manner. From there, the coating medium is then transferred to the material web 10. Doctor blades 32, 34 are used for Dosing and equalization of the coated on the rollers 14, 16 coating medium. Such squeegee units are well known in the art and require no further explanation in connection with the present invention.

The quantity and thickness of the medium applied to the material web 10 are influenced by the nip load prevailing in the application gap 12, which is the pressing force which is transmitted between the rolls 14, 16. In order to know this Niplast, the coating unit is equipped with a sensor arrangement which directly detects the transmitted pressing force. The sensor arrangement is arranged in the transmission path of the pressing force and measures the latter prior to introduction into or / and after emerging from the roller bodies of the pair of rollers 14, 16. Specifically, the sensor arrangement in the embodiment of Fig. 1 at least one force sensor 36, which is attached to the bearing lever 24 or the stator 22 and its sensor signal to the control unit 30 supplies. In principle, it is sufficient to provide only one such force sensor 36 along the transmission path of the pressing force. It is in itself indiscriminate whether the force sensor 36 is mounted on the bearing lever 24 or on the stand 22, provided that it is aligned and positioned so that essentially only the force component to be detected, but this completely passes through it. The choice of the stator 22 as a mounting location for the force sensor 36 may of course have the advantage that the wiring of the force sensor 36 does not have to be guided over a pivot point, which is not a serious problem with the currently available technology. A preferential choice for the mounting location of the force sensor 36 can still result if the material web 10 is not - as in Fig. 1 - In a straight line in the order gap 12 and runs out of this, but at least one of the rollers 14, 16 partially wraps around. Then, the force sensor 36 is preferably attached to that of the components: bearing lever 24 and stator 22, which are the lower wrapper through the web 10 carries. In this way, the influence of the web tension on the force measurement can be minimized.

However, both the bearing lever 24 and the stator 22 can be provided with at least one force sensor 36, which makes it possible to control the measured pressing force by comparing the sensor signals. Expediently, the bearing lever 24 or the stator 22 will be provided axially on either side of the roller pairing 14, 16, each with a force sensor 36 in order to be able to obtain at least approximately information about the axial distribution of the Niplast.

The force sensor 36 can be constructed, for example, from strain gages applied externally to the bearing lever 24 or the stator 22, which detect the elastic deformations of the bearing lever 24 or of the stator 22 that occur as a result of the mutual contact pressure of the rollers 14, 16. The interconnection of several such strain gauges in bridge circuits is known per se from the prior art.

Depending on the measured actual pressing force, the control unit 30 effects a suitable activation of the force device arrangement 26 in order to obtain a desired pressing force predetermined by an operator, for example, by input at a control console and to maintain it as part of an automatic control. The to be adjusted pressure force will be equal in most applications in both axial end portions of the pair of rollers 14, 16, so that a consistent over the machine width line pressure results. In addition to determining the force, the control unit 30 may also be designed to determine from the sensor signals the oscillation behavior of the roller pairing 14, 16 and to actuate the force device arrangement 26 in the sense of influencing the oscillation.

The force provided by the power device assembly 26 may be transmitted substantially exclusively via the rollers 14, 16 as a single power transmission path. However, the coating can be made stiffer and less susceptible to vibration as the force provided by the power device assembly 26 is transmitted in multiple power transmission paths. This is in Fig. 1 Dashed a pair of cooperating stopper body 38, 40 located, one of which is arranged on the bearing lever 24 and the other is arranged on the stator 22. One of the stop elements 38, 40 - here the stopper body 38 - is adjustable by means of a controllable by the control unit 30 positioning member 42, for example a Spindelhubglieds. Accordingly, two force transmission paths are available for the force provided by the force device arrangement 26: a first, which runs over the rollers 14, 16, and a second, which runs over the stop bodies 38, 40. By adjusting the position of the stopper body 38, the ratio of the forces transmitted via the two force transmission paths and thus the effective pressing force between the rollers 14, 16 can be changed.

The at least one force sensor 36 is located in the over the rollers 14, 16 extending force transmission path at a point after its branch from the second power transmission path and before the reunification with the second power transmission path. In this way, the actual pressure force is still detected by the force sensor 36 immediately, and any distortions or thermally induced deformations within the coating unit can not falsify the measurement result.

During operation of the coating system, the force device arrangement 26 preferably always applies a maximum force to the bearing lever 24. The desired pressing force is then, depending on the supplied sensor signal of the force sensor 36, by suitable adjustment of the Stop body 38 is set. The further the stopper body 38 in Fig. 1 is adjusted to the right, the greater the proportion of the transmitted over the stopper body 38, 40 force on the available total force. As far as the latter remains unchanged, the pressing force then decreases accordingly. When adjusting the stopper body 38 to the left in Fig. 1 the reverse applies.

It is understood that a pair of such stopper body 38, 40 is arranged on both axial sides of the roller pairing 14, 16, wherein these pairs are preferably independently adjustable by means of a respective positioning member 42.

In Fig. 2 are identical or equivalent components with the same reference numerals as in Fig. 1 provided, but supplemented by a lowercase letter. Since only differences from the previous exemplary embodiment are to be discussed below, for explanations of these components, reference is made to the preceding description of FIG Fig. 1 directed.

Fig. 2 shows an embodiment in which one or more, not shown in detail sensor elements, such as strain gauges are housed in a load cell 36a, which forms a mechanically sealed, separate component, which is installed between the bearing lever 24a and a bearing assembly 46a, the storage an axial bearing pin 48a of the roller 14a is used. (It should be understood that the bearing lever 24a and the roller 14a are exemplified herein.) Of course, such a load cell may also be installed between the machine stand and the other roller.) The bearing assembly 46a includes a bearing housing 50a and a rolling bearing 52a received therein an inner ring 54a and an outer ring 56a. The load cell 36a may be, for example, a commercially available force measuring block, as sold by the company FMS Force Measuring Systems AG, Switzerland. The use of the load cell 36a has the advantage that the sought force passes through them exactly and standard components standardized for the bearing housing 50a and the roller bearing 52a can be used.

As an alternative to a load cell, the bearing pin 48a could also be extended to a measuring bolt by attaching one or more suitable sensor elements to it. This is in Fig. 2 indicated by dashed lines at 36b. Furthermore, it is possible to mount such sensor elements in the bearing housing 50a. The bearing lever 24a could then remain structurally unchanged, and for the rolling bearing 52a could in turn be resorted to a standard component.

As a further alternative measuring point for detecting the pressing force, the rolling bearing 52a comes into consideration. Here, one or more sensor elements can be retrofitted, for example, on the outer ring 56a. The rolling elements of the rolling bearing 52a cause under load elastic deformations of the outer ring 56a, which are a measure of the transmitted force and can be detected. Finally, it is conceivable to use a rolling bearing 52a with an integrated force sensor, that is to say a bearing which has already been prepared by the manufacturer with suitable force detection elements. Without constructive changes, the bearings of existing coating units can then be replaced by such "measuring bearings".

As already mentioned above, the coating color, with which the material web 10 is to be coated, is first applied in a manner not shown, but known per se, to the rollers 14, 16, which in turn transfer the coating color to the material web 10. Doctor blades 32, 34 are used for metering and equalizing the coating applied to the rollers 14, 16 coating color. The squeegee unit 32 has a squeegee bar 136 in which a squeegee rod 138 is rotatably supported. The doctor bar 136 is in turn attached to a pivot arm 140 which is pivotally connected to the bearing lever 24. By means of another, between the bearing lever 24 and the pivot arm 140 supporting pivot drive assembly 142, the pivot arm 140 can be approximated to the moving roller 14 and so the squeegee rod 138 pressed against the surface of the roller 14. Similarly, the squeegee assembly 34 includes a squeegee bar 144, a squeegee rod 146, and a pivot arm 148 pivotally mounted to the machine stand 22 which is engageable with the fixed roller 16 by means of a pivot drive assembly 150 supported between the machine stand 22 and the pivot arm 148. The pivoting drive assemblies 142, 150 are preferably each formed by at least one hydraulic piston-cylinder unit.

The amount and thickness of the paint applied to the material web 10 are influenced by the nip load prevailing in the application nip 12, that is to say the pressing force which is transmitted between the rolls 14, 16. When the rollers 14, 16 are pressed against one another, their covers 128, 130 are compressed and flattened in the region of the application gap 12, which results in a reduction of the distance between the axes 18, 20 of the rollers 14, 16. In the elastic region of this compression of the covers of the mutual center distance, which is denoted in the figure with e, a measure of the transmitted pressing force and thus the Niplast order gap 12. This spring corresponding behavior of the pair of rollers 14, 16 is in the illustrated coating used to set a certain desired Niplast in the brushing operation. For this purpose, in a pre-determined spring characteristic, which indicates the dependence of the axial distance e of the transmitted pressing force, looked up, which center distance must be set concretely to obtain this desired pressing force. The spring characteristic is data-technically deposited in an electronic memory 152, accessing the memory contents of a microprocessor-based electronic control unit 30. The data representation of the spring characteristic in memory 152 may be a formulaic one. Frequently, however, the spring characteristic becomes tabular be stored in the form of a plurality of pairs of values, each of these value pairs for a value of the pressing force includes an associated value of the axial distance e or a representative of the axial distance e size.

To adjust the axial distance e is used in the embodiment of a controlled by the control unit 30 positioning member 42, which is preferably designed as an electric motor driven spindle lifting member. The positioning member 42 is used to adjust a relative to the machine stand 22 stationarily arranged first stop body 38, which is intended to cooperate with a fixedly arranged on the bearing lever 24 second stop body 40. In operation of the coating system, the bearing lever 24 is pivoted by means of the power device assembly 26 toward the fixed roller 16 until the two stopper body 38, 40 abut each other. The center distance e of the rollers 14, 16 depends in this working position on the position of the first stopper body 38. By adjusting the first stop body 38 thus the center distance e can be changed. During operation of the coating unit, the control unit 30 controls the positioning member 42 in accordance with the information obtained from the spring characteristic in such a way that the value of the center distance e which corresponds to a desired nip load is set. This desired Niplast is communicated to the control unit 30, for example via an operator not shown in detail by an operator.

The determination of the spring characteristic takes place in a preceding the actual operation of the coating plant calibration phase. In this case, for example, proceed as follows: First, a zero point of the spring characteristic is determined. For this purpose, the first stop body 38 is moved back by means of the positioning member 42 in the figure to the left. Then, the bearing lever 24 is pivoted by means of the power device assembly 26 in the direction of the fixed roller 16, until the rollers 14, 16 substantially free of force transmission, ie without generating a Niplast touch. This condition can be detected, for example, by an operator by means of a paper strip which she holds in the order gap 12. With stationary rollers 14, 16, the desired state is reached when the paper strip can just pull through the application gap 12. For rotating rollers, the achievement of the desired condition can be recognized by the rollers 14, 16 starting to pick on the paper strip. As soon as the desired state is reached, the first stopper body 38 is advanced again by means of the positioning member 42 until it comes into contact with the second stopper body 40. The contact is detected by means of a sensor 62, which may be, for example, a touch sensor, but also a force transducer. This position of the first stopper body 38 is then stored by the control unit 30. It represents a value of the axial distance e, in which substantially no pressing force between the rollers 14, 16 is transmitted, ie the zero point of the spring characteristic.

After determining the characteristic zero point, at least one further characteristic point must be recorded at a defined niplast. This may be, for example, the end point of the spring characteristic, in which there is a maximum nip load for which the coating is intended and designed. To determine this further characteristic point, the first stopper body 38 is retracted again by means of the positioning member 42 until it is out of the range of the second stopper body 40. Then, by activating the power device assembly 26, such a force is introduced into the bearing lever 24 that the roller 14 is pressed against the roller 16 to produce a nip load. By theoretical considerations, taking into account the geometrical conditions of the coating system, the line load prevailing in the application gap 12 can be readily calculated from the force provided by the power device assembly 26, at least as long as the stopper bodies 38, 40 are out of contact and no force is transmitted between them. After using the Power device assembly 26 is generated a defined Niplast, now the first stopper body 38 is moved by means of the positioning member 42 back to the second stopper body 40 until it comes into contact with the latter. The contact production is in turn detected by the sensor 62. The position occupied by the first stopper body 38 at the moment of making contact is different from the zero point determination of the spring characteristic. As a result of the mutual contact pressure of the rollers 14, 16, the roller covers 128, 130 namely in the region of the order gap 12 is slightly flattened, whereby the rollers 14, 16 compared to the zero point of the spring characteristic slightly closer to each other to hike. This means that the center distance e of the rollers 14, 16 is now slightly lower than in the characteristic zero point. Also, this position of the first stopper body 38 is stored by the control unit 30, in conjunction with the associated Niplast.

There are now two characteristic points available, by means of which the control unit 30 can interpolate the entire curve, if desired, stepwise. Of course, more than two characteristic points can be recorded in the calibration phase. In particular, approximately the entire spring characteristic can be recorded by measurement. It is also understood that, instead of the zero and the end point of the spring characteristic, any two other characteristic points lying in between can be picked up and made the basis for a subsequent characteristic interpolation.

In operation of the coating system, the power device assembly 26 preferably always provides such a force that when the first stopper body 38 is out of contact with the second stopper body 40 and consequently no force is transmitted via the stopper members 38, 40, the maximum load is maximized and consequently the center distance e is minimal. If a lower Niplast be set, so causes the control unit 30 based on the memory 152 stored in the characteristic data an adjustment of the first stop body 38 by a corresponding amount in the direction of the second stop body 40. This increases the center distance e between the rollers 14, 16, so that the flattening of the roller covers 128, 130 in the application gap 12 is lower and the Niplast decreases accordingly. Since the force provided by the power device assembly 26 remains unchanged, the difference proportion between this provided force and the force transmitted via the rollers 14, 16 is transmitted via the two stop bodies 38, 40. The total power provided thus branches into a first power transmission path, which leads over the rollers 14, 16, and a second power transmission path, which leads over the stopper body 38, 40. The farther the first stop body 38 is moved to the right in the figure, the greater the proportion of the total force provided via the stop bodies 38, 40. The desired nip load can accordingly be obtained in a simple manner by appropriate adjustment of the first stop body 38.

Thermal influences, mechanical stresses and contact vibrations can cause the center distance e to change during operation of the coating. In order to detect such variations in distance, a distance sensor 64 is provided according to the invention, the sensor signals of which are evaluated by the control unit 30 and, if necessary, converted into corresponding correction signals to the positioning member 42. In this way, a control loop can be set up which keeps the center distance e constant at a desired value. The distance sensor 64 may be, for example, an optical sensor. Of course, other sensor principles are conceivable.

If the sensor 62 allows detection of the transmitted force on the stopper body 38, 40, instead of a distance control and a force control can be set up immediately. Because the over the stopper body 38, 40 transferred force with knowledge of the Kraftgeräteanordnung 26 total force provided directly back to the Niplast in the order column 12, the sensor signals of the sensor 62 can be used to control the position of the first stop body 38.

The assembly of positioning member 42 and stopper members 38, 40 is suitably provided on both axial sides of the pair of rollers 14, 16, wherein each positioning member 42 is preferably independently controllable. In this way, the center distance e can be set independently on both axial sides. This makes it possible to adjust an axially changing line load in the application gap 12, although in many applications a constant line load will be desired. At the same time, this makes it possible to compensate for fluctuations in the axial distance e occurring during operation, which possibly only occur locally on one axial side, individually.

An alternative procedure for determining the spring characteristic will now be described. Initially, only one axial side of the coating unit is considered, although the subsequent process is of course carried out on both axial sides. This alternative procedure begins with the local first stop body 38 being brought into a front, fully extended end position on the considered axial side of the coating unit by means of the associated positioning member 42. Then, the roller 14 is pivoted to the roller 16 until the second stopper body 40 abuts against the first stopper body 38. The front end position of the first stopper body 38 is such that the rollers 14, 16 do not touch each other when the two stopper members 38, 40 are in mutual abutment. The power device assembly 26 is driven so that the force exerted by it on the bearing lever 24 is maximum. By maximum force is meant that force which would result in the maximum nip load if the force alone would be transmitted via the roller pairs 14, 16. However, since at full extended first stopper body 38 of the rollers 14, 16 leading force transmission path is open, the force provided by the power device assembly 26 is transmitted solely through the stopper body 38, 40. The sensor 62 arranged in this force transmission path is designed as a force sensor in the alternative procedure described here. The force value that it detects when fully extended first stop body 38 and maximum force of the power device assembly 26 is stored by the control unit 30.

The roller 14 is now moved back again, and by actuation of the positioning member 42, the first stop body is brought into a rear, fully retracted end position. Subsequently, the roller 14 is pivoted back to the roller 16 with maximum force of the power device assembly 26. The rear end position of the first stopper body 38 is adjusted so that the second stopper body 40 does not abut against the first stopper body 38. In order column 12, therefore, there is maximum Niplast. Now, the first stopper body 38 is advanced by means of the positioning member 42 until it comes into contact with the second stopper body 40. The contact between the two stop members 38, 40 is detected from the signal of the force sensor 62, for example, when the control unit 30 detects a change in the measured force by a predetermined value. The position thus achieved of the first stopper body 38 is stored; it represents the end point of the spring characteristic, in which there is a maximum niplast in the application gap 12.

By actuation of the positioning member 42, the first stopper body 38 is then further extended. In the process, the force transmitted via the stop elements 38, 40 increases. When the first stopper body 38 is extended so far that the force sensor 62 indicates the force value stored at the beginning, the positioning member 42 is stopped and the position of the first stopper body 38 is stored. It corresponds to the zero point the spring characteristic. From the zero and end points of the spring characteristic determined in this way, it is then possible, by linear interpolation, to successively calculate several characteristic intermediate points.

The above-described alternative procedure for determining the spring characteristic has the advantage that no different forces have to be set on the force device arrangement 26, but that it is sufficient to set only the maximum force on the force device arrangement 26 in order to determine both the characteristic zero point and the characteristic curve. Determine endpoint. In addition, the time required for the calibration of the coating system is lower, since only a reversal of the direction of travel of the positioning member 42 is required.

External forces (eg, weight forces of various components of the coating, such as ink supply) can lead to skewing of the rollers 14, 16 relative to each other, to compensate for which it is necessary that the power device assembly 26 on the two axial sides of the coating different forces on the Bearing lever 24 exercises. In order to take account of such external influences already during the calibration, the above-described alternative procedure for determining the spring characteristic can be modified in the following way. At the beginning of the calibration process, the first two stop members 38 are driven to their forwardmost end position on both axial sides of the coating unit, and the power unit assembly 26 is driven to provide the same maximum force on both axial sides of the coating unit. Then it is measured on each axial side by means of the respective force sensor 62, which force is transmitted to the respective pair of first and second stopper body 38, 40. If the first roller 14 is aligned exactly parallel to the axis of the second roller 16, then these force values are the same. On the other hand, if there is an inclination of the first roller 14 relative to the second roller 16, different force values result. The two force values thus determined are stored by the control unit 30. Then - as before - the first stopper body 38 is moved to its rear end position and extended from this rear end position to the contact with the respectively associated second stopper body 40 again. Subsequently, the first stopper body 38 on that axial side, on which initially the greater force value was measured, extended so long towards its front end position, between the measured force values of the force sensors 62 a difference sets, equal to the difference between the initially measured and stored force values. Once this condition is reached, the uneven mutual contact pressure of the rollers 14, 16, which was caused by the original force difference, balanced. The position of each of the first stopper bodies 38 is now stored; it corresponds to the maximum niplast.

Then, both first stopper members 38 are moved together toward their front end position until the force sensors 62 indicate the force value originally stored for the respective axial side. The two positioning members 42 are then stopped simultaneously and their position or that of the first stopper body 38 as a zero-Niplast, i. Defined and saved as characteristic zero point.

In the present example case, it was assumed that the power device arrangement 26 is force-controlled. However, if a path-controlled embodiment of the force device assembly 26 is selected, for example using a spindle drive, then the abutment members 38, 40 and the positioning member 42 may be dispensed with and a desired center distance e instead set directly using the force device assembly 26. In this case, only one power transmission path would exist, passing over the rollers 14, 16. In contrast, the provision of at least one further force transmission path, as it is formed in the illustrated embodiment by the positioning member 42 and the stopper body 38, 40, has the advantage that the coating unit overall stiffer and thus less susceptible to vibrations can be made.

In summary, the invention allows a very precise adjustment of a desired Niplast, especially when it is relatively low. Due to the high precision of the niplaste setting, a high-quality coating result can be achieved irrespective of the roll diameter, the roll cover thickness, the roll hardness and possible stresses. The high precision of the niplaste setting helps to minimize contact vibrations between the rolls. The ability to precisely set even very low nip loads also helps to reduce the so-called "misting", which is a mist-like spraying of the coating color at the outlet of the order gap and can affect the coating result.

Claims (36)

1. Arrangement for pressing against each other two rolls (14, 16) in a device for producing and/or treating a moving material web (10),
   the axes of the two rolls (14, 16) being arranged parallel to one another and at least one of the rolls (14, 16) having a radially resilient roll cover (128, 130), and
   actuating means (26, 42) being provided, by means of which the two rolls (14, 16) can be moved close to each other along an approach path and can be set into a close state, in which a desired pressing force is transmitted between the rolls (14, 16),
   characterized
   in that distance sensor means (64) are also provided, which register the actual value of the axial spacing (e) of the two rolls (14, 16),
   in that a storage unit (152) is also provided, which stores a previously determined axial spacing-pressing force characteristic, this axial spacing-pressing force characteristic representing a relationship between the actual axial spacing (e) of the two rolls (14, 16) which is registered by the distance sensor means (64) and the pressing force transmitted between the two rolls (14, 16), and
   in that a control unit (30) is provided which, as a function of the desired pressing force, determines a setpoint value of the axial spacing (e), on the basis of the axial spacing-pressing force characteristic which is stored in the storage unit (152), and actuates the actuating means (26, 42) in the sense of setting the actual value of the axial spacing (e) to the setpoint value of the axial spacing (e).
2. Arrangement according to Claim 1, characterized in that the control unit (30) actuates the actuating means (26, 42) in the sense of setting the actual value of the axial spacing (e) to the setpoint value of the axial spacing (e) in a regulated manner.
3. Arrangement according to Claim 1 or 2, characterized in that the axial spacing (e) of the rolls (14, 16) in the region of the two axial ends of the two rolls (14, 16) can be set independently of one another, and the control unit (54) is designed to set the axial spacings (e) in the two axial end regions of the pair of rolls (14, 16) in such a way that the result is a substantially constant line pressure between the rolls (14, 16) over the axial extent of the pair of rolls (14, 16).
4. Arrangement according to any one of Claims 1 to 3, characterized in that a first (14) one of the rolls (14, 16) is held on a roll support (24) which can be displaced with respect to the second roll (16) along the approach path, and the actuating means (26, 56) comprise a force-producing means (26) acting on the roll support (24) in order to introduce into the roll support (24) a force that produces the pressing force.
5. Arrangement according to Claim 4, characterized in that the force made available by the force-producing means (26) is used substantially completely for producing the pressing force.
6. Arrangement according to Claim 4, characterized in that the force made available by the force-producing means (26) is branched to a first force transmission path transmitting the pressing force between the two rolls (14, 16) and at least one second force transmitting path.
7. Arrangement according to Claim 6, characterized in that the ratio between the force transmitted on the first force transmission path and the force transmitted on the at least one second force transmission path can be varied.
8. Arrangement according to Claim 7, characterized in that stop means (58, 60) are arranged in the at least one second force transmission path and can be adjusted in order to vary the ratio of the forces transmitted in the various force transmission paths.
9. Arrangement according to Claim 8, characterized in that the stop means (58, 60) comprise at least one stop (60) which is arranged for common movement with the first roll (14) along its approach path to the second roll (16), and at least one opposing stop (58) fixed with respect to the axis (20) of the second roll (16), and in that at least one of the components: stop (60) and opposing stop (58) can be adjusted.
10. Arrangement according to any one of Claims 1 to 9, characterized in that it is intended for use in a machine for coating a paper or board web (10).
11. Arrangement according to Claim 10, characterized in that the paper or board web (10) is led through between the rolls (14, 16), and at least one of the rolls (14, 16) is used to transfer a liquid to pasty application medium to the paper or board web (10).
12. Arrangement according to any one of Claims 6 to 11, characterized in that the sensor means are arranged in the first force transmission path after it branches away from the at least one second force transmission path.
13. Arrangement according to any one of Claims 6 to 12, characterized in that the sensor means (36; 36a; 36b) comprise at least one sensor (36) which, in relation to the force transmission direction of the first force transmission path, is arranged upstream of the roll body of a first following roll (14) of the two rolls (14, 16).
14. Arrangement according to any one of Claims 6 to 13, characterized in that the sensor means (36; 36a; 36b) comprise at least one sensor (36) which, in relation to the force transmission direction of the first force transmission path, is arranged downstream of the roll body of a second following roll (16) of the two rolls (14, 16).
15. Arrangement according to Claim 13 and 14, characterized in that the sensor means (36; 36a; 36b) comprise at least one sensor (36) arranged upstream of the roll body of the first following roll (14) and at least one sensor (36) arranged downstream of the roll body of the second following roll (16).
16. Arrangement according to any one of Claims 4 to 15, characterized in that one (16) of the two rolls (14, 16) is mounted on a stand (22) such that its position is fixed relative to the latter but it can rotate, in that a roll support (24) which mounts the other roll (14) such that it can rotate is fitted to the stand (22) and can be pivoted relative to the stand (22) in order to bring the two rolls (14, 18) close to each other, and in that the force-producing means (26) act on the bearing lever (24).
17. Arrangement according to Claim 16, characterized in that the sensor means (36; 36a; 36b) comprise at least one sensor (36) which is fitted to the roll support (24) or the stand (22).
18. Arrangement according to Claim 16 or 17, characterized in that the sensor means (36; 36a; 36b) comprise at least one sensor (36b) which is arranged in a bearing region of one of the rolls (14a).
19. Arrangement according to Claim 18, characterized in that the sensor (36b) is fitted to a bearing journal (48a) of the relevant roll (14a).
20. Arrangement according to Claim 18, characterized in that an antifriction bearing (52a) enclosing a bearing journal (48a) of the relevant roll (14a) is provided with the sensor.
21. Arrangement according to Claim 20, characterized in that the sensor is integrated into the antifriction bearing (52a).
22. Arrangement according to Claim 20, characterized in that the sensor is fitted onto an outer ring (56a) of the antifriction bearing (52a).
23. Arrangement according to Claim 18, characterized in that the sensor is fitted to a bearing housing (50a) in which an antifriction bearing (52a) surrounding a bearing journal (48a) of the relevant roll (14a) is accommodated.
24. Arrangement according to any one of Claims 16 to 23, characterized in that the sensor means (36; 36a; 36b) comprise at least one sensor which is accommodated in a separately produced sensor module (36a), this sensor module (36a) being built in between the stand or the roll support (24a) and a bearing kit (46a) for a bearing journal (48a) of the roll (14a) held on the stand or the roll support (24a).
25. Arrangement according to Claim 24, characterized in that the actuating means (26) in the region of both axial ends of the pair of rolls (14, 16) each comprise at least an independently controllable, in particular hydraulic, force device (28), and the sensor means (36; 36a: 36b) are designed for the mutually independent registration of the pressing force in both axial end regions of the pair of rolls (14, 16).
26. Method of setting the pressure between two axially parallel rolls (14, 16) which can be moved toward each other in a device for producing and/or treating a moving material web (10), using an arrangement according to any one of the preceding claims,
    characterized
    in that distance sensor means (64) register the actual value of the axial spacing (e) of the two rolls (14, 16),
    in that an axial spacing-pressing force characteristic for the two rolls (14, 16) is previously determined, which represents a relationship between the actual value of the axial spacing (e) of the two rolls (14, 16) and the pressing force transmitted between the two rolls (14, 16),
    in that this axial spacing-pressing force characteristic is stored in a storage unit (152),
    in that a control unit for achieving a desired pressing force of the rolls (14, 16) during operation of the device determines an associated setpoint value of the axial spacing (e), on the basis of the axial spacing-pressing force characteristic which is stored in the storage unit (152), and actuates the actuating means (26, 42) in the sense of setting the actual value of the axial spacing (e) to the setpoint value of the axial spacing (e).
27. Method according to Claim 26, characterized in that, in order to determine the axial spacing-pressing force characteristic, measurements are carried out in a calibration phase of the device.
28. Method according to Claim 26 or 27, characterized in that, in order to determine the axial spacing-pressing force characteristic, at least two value pairs of axial spacing (e) and pressing force are determined for different values of the pressing force.
29. Method according to Claim 28, characterized in that one of the value pairs is determined for a close position of the rolls (14, 16), in which the rolls (14, 16) are moved toward each other substantially until mutual contact is produced but substantially no pressing force is transmitted between the rolls (14, 16).
30. Method according to Claim 28 or 29, characterized in that one of the value pairs is determined for a pressing force transmitted between the rolls (14, 16) which at least approximately corresponds to a maximum pressing force for which the device is designed.
31. Method according to any one of Claims 28 to 30, characterized in that, in order to determine the axial spacing-pressing force characteristic, interpolation between the value pairs determined is carried out, in particular linearly.
32. Method according to any one of Claims 26 to 31, characterized in that, after the roll cover (28, 30) of the at least one roll has been ground, the axial spacing-pressing force characteristic is determined again.
33. Method according to any one of Claims 26 to 32, characterized in that, during working operation of the device, the actual value of the axial spacing (e) of the rolls (14, 16) is adjusted to the desired value of the axial spacing (e).
34. Method according to any one of Claims 26 to 33, characterized in that the axial spacing (e) of the rolls (14, 16) in the region of the two axial ends of the pair of rolls (14, 16) can be set independently of one another, and the axial spacings (e) in the two axial end regions of the pair of rolls (14, 16) are set in such a way that the result is a substantially constant line pressure between the rolls (14, 16) over the axial extent of the pair of rolls (14, 16).
35. Method according to any one of Claims 26 to 34, characterized in that it is carried out in a machine for coating a paper or board web (10).
36. Method according to Claim 35, characterized in that the paper or board web (10) is led through between the rolls (14, 16) and at least one of the rolls (14, 16) is used to transfer a liquid to pasty application medium to the paper or board web (10).

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