CA2060769C - Method for regulation of the transverse profile of the coating quantity on a web material and coating station for carrying out the method - Google Patents
Method for regulation of the transverse profile of the coating quantity on a web material and coating station for carrying out the method Download PDFInfo
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- CA2060769C CA2060769C CA 2060769 CA2060769A CA2060769C CA 2060769 C CA2060769 C CA 2060769C CA 2060769 CA2060769 CA 2060769 CA 2060769 A CA2060769 A CA 2060769A CA 2060769 C CA2060769 C CA 2060769C
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- blade
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C11/00—Component parts, details or accessories not specifically provided for in groups B05C1/00 - B05C9/00
- B05C11/02—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface ; Controlling means therefor; Control of the thickness of a coating by spreading or distributing liquids or other fluent materials already applied to the coated surface
- B05C11/04—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface ; Controlling means therefor; Control of the thickness of a coating by spreading or distributing liquids or other fluent materials already applied to the coated surface with blades
- B05C11/041—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface ; Controlling means therefor; Control of the thickness of a coating by spreading or distributing liquids or other fluent materials already applied to the coated surface with blades characterised by means for positioning, loading, or deforming the blades
- B05C11/042—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface ; Controlling means therefor; Control of the thickness of a coating by spreading or distributing liquids or other fluent materials already applied to the coated surface with blades characterised by means for positioning, loading, or deforming the blades allowing local positioning, loading or deforming along the blades
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
- D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
- D21H23/22—Addition to the formed paper
- D21H23/32—Addition to the formed paper by contacting paper with an excess of material, e.g. from a reservoir or in a manner necessitating removal of applied excess material from the paper
- D21H23/34—Knife or blade type coaters
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
- D21H25/08—Rearranging applied substances, e.g. metering, smoothing; Removing excess material
- D21H25/10—Rearranging applied substances, e.g. metering, smoothing; Removing excess material with blades
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- Coating Apparatus (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Paper (AREA)
Abstract
The invention concerns a method for regulation of the transverse profile of the coating quantity on a paper or any other web material in a coating station, in which the web is passed over a backup roll and a coating agent is smoothed by means of a coating blade loaded against the web. The quantity of coating agent applied onto the web is regulated by actuators acting upon the constructions of the coating station. In the method; the transverse profile of the coating quantity applied onto the web is measured constantly, and a differential profile of the measured transverse profile and the desired transverse profile is calculated. The differential profile is fed as a regulation quantity to the actuators that adjust the transverse profile of the coating quantity so as to correct the transverse profile. The invention is advantageously carried out so that, in the method, an equation is approximated by means of calculation which corresponds to the transverse differential profile of the web coating quantity between the measured transverse profile and the desired transverse profile, and out of said equation, the average error and/or inclination and/or curvature of the differential profile and/or the frequency of a cyclic error of coating quantity is/are determined, they parameters corresponding to said values being fed as regulation quantities to regulation devices that regulate the properties of coating quantity so as to correct the transverse profile. The invention further concerns a coating station construction intended for carrying out the method.
Description
METHOD FOR REGULATION OF THE TRANSVERSE PROFILE
OF THE COATING QUANTITY ON A WEB MATERIAL AND
COATING STATION FOR CARRYING OUT THE METHOD
The present invention is related to the regulation of the quantity of coating agent remaining in a coating machine on a paper or any other web, in particular in the transverse direction of the machine. More specifically, the invention concerns a method for regulation of the transverse profile of the coating quantity on a paper of any other web material in a coating station, in which the web is passed over a backup roll and the coating agent is smoothed by means of a coating blade loaded against the web and in which the quantity of coating agent applied onto the web is regulated by means of actuators acting upon the coating station, and in which method the transverse profile of the coating quantity applied onto the web is measured constantly.
Further, the invention concerns a coating station intended for carrying out the method, wherein the web is passed to run over a backup roll and which coating station is provided with a coating blade loaded against the web, the blade being mounted in a blade holder supported on the frame beam of the coating station, and which coating station is, by the intermediate of a regulation and control circuit, connected with measurement means for measurement of the transverse profile of the coating quantity.
In respect of the prior art related to the invention, reference is made to U.S. Patent Nos. 3,079,889, 3,301,214, and 4,396,648 as well as to Finnish Patent Applications Nos.
851891, ~u~i~~~~
871566, and 894842, which concern so-called short-dwell-time applicators.
Conventionally, the short-dwell-time applicators used far the coating of paper, board, and equivalent comprise a coating-agent chamber, which is defined by a coating blade that rests against the base to be coated, such as paper, board or equivalent, by a front seal and by lateral seals. The coating agent is introduced under pressure into the coating-agent chamber and therein enters into direct contact with the base to be coated. The coating blade spreads and smooths a layer of the coating agent of desired thickness onto the surface of the base to be coated. Substantially two different types of devices of this sort are known. On one hand, so-called large-angle-blade coating is known in which, normally, the coating blade forms an angle of several dozens of degrees with the moving base to be coated. On the other hand, so-called mall-angle-blade coating is known, in which the coating blade farms and angle of just a few degrees (normally about 0 to about 10 °) with the moving base to be coated.
An advantage of small-angle-blade coating especially in the coating of board is relatively good unii:ormity of the thickness of the coating layer, which is of signii:icance in view of uniform absorption of printing ink. Further, impurities in the coating mix and/or in the board can by-pass the blade without adhering to it, in which case no streaks arise from the blade. A drawback in small-angle-blade coating is the difficulty in controlling the quantity of coating, for, e.g., when the small angle between the blade and the moving base is changed even just a little to regulate the coating quantity, the quantity of the coating mix applied to the waving base is changed highly extensively.
In small-angle-blade coating, the mast important parameter or regulation of the coating quantity is, as a rule, so-called pre-stressing of the coating blade, which means that the tip of the coating blade is bent mechanically adjusting the distance of the whole applicator device .from the moving base. Further parameters of regulation are the load on the tip portion of the coating blade as well as regulation of the blade angle.
With respect to the prior art, reference is additionally made to bE publication No. 3,446,525, in whose solution the regulation of the coating quantity is arranged so that the dam blades are made mobile. One of the drawbacks of the solution in accordance with said publication is that the dam blade must be .
very rigid in order that the cylinders intended for displacement of the dam blade must be very rigid in order that the cylinders intended for displacement of the dam blade should not bend it.
In the solution of said publication, the regulation of the return flow of the coating agent is arranged as regulation of the size of the return flow gap, in which case the pressure of the coating agent may vary even considerably in the transverse direction of the web. Thus, the device concerned is not suitable for regulation of the profile of the coating quantity.
Further, FI Pat. Appl. No. 861241 describes a method and a device for the coating of paper wherein the coating mix is pre-spread by means of a resilient blade, and the ultimate doctoring is carried out by means of a dragging doctor blade.
The applicator device is placed at the side of the backup roll, and the coating mix rests against the web over a long distance.
In said solution, deaeration of the coating mix is difficult, and integration of the dragging doctor blade in the applicator equipment makes the maintenance operations more difficult. In said solution, in the application zone preceding the smoothing blade, the coating mix is susceptible to disturbances, such as uneven distribution of the coating material. A typical consequence of this is longitudinal streaks that remain in the coating.
The present invention is directed towards achieving a substantial improvement over the prior art so that the coating quantity can be regulated in the desired way in the transverse direction of the machine.
In one aspect of the present invention, there is provided a method for regulation of the quantity of coating applied to a web in a coating station, in which the web is passed over a backup roll and a layer of the coating agent is applied by means of a coating blade loaded against the web, the quantity of coating agent applied to the web being regulated by means of an actuator acting upon the constructions of the coating station, the coating quantity applied to the web being constantly monitored, characterized in that, in order to regulate the transverse profile of the coating quantity, the thickness of the coating is measured in a plurality of transverse zones so as to calculate a measured transverse profile, a differential profile is calculated by comparing the measured transverse profile with the desired transverse profile, and the differential profile is fed as a regulation quantity to a plurality of actuators arranged to adjust the transverse profile of the coating quantity so as to correct the said transverse profile.
In the method aspect of the invention, therefore, a differential profile of the measured transverse profile and the desired transverse profile is calculated. The differential profile is fed as a regulating quantity to the actuators that adjust the transverse profile of the coating quantity so as to correct the transverse profile.
OF THE COATING QUANTITY ON A WEB MATERIAL AND
COATING STATION FOR CARRYING OUT THE METHOD
The present invention is related to the regulation of the quantity of coating agent remaining in a coating machine on a paper or any other web, in particular in the transverse direction of the machine. More specifically, the invention concerns a method for regulation of the transverse profile of the coating quantity on a paper of any other web material in a coating station, in which the web is passed over a backup roll and the coating agent is smoothed by means of a coating blade loaded against the web and in which the quantity of coating agent applied onto the web is regulated by means of actuators acting upon the coating station, and in which method the transverse profile of the coating quantity applied onto the web is measured constantly.
Further, the invention concerns a coating station intended for carrying out the method, wherein the web is passed to run over a backup roll and which coating station is provided with a coating blade loaded against the web, the blade being mounted in a blade holder supported on the frame beam of the coating station, and which coating station is, by the intermediate of a regulation and control circuit, connected with measurement means for measurement of the transverse profile of the coating quantity.
In respect of the prior art related to the invention, reference is made to U.S. Patent Nos. 3,079,889, 3,301,214, and 4,396,648 as well as to Finnish Patent Applications Nos.
851891, ~u~i~~~~
871566, and 894842, which concern so-called short-dwell-time applicators.
Conventionally, the short-dwell-time applicators used far the coating of paper, board, and equivalent comprise a coating-agent chamber, which is defined by a coating blade that rests against the base to be coated, such as paper, board or equivalent, by a front seal and by lateral seals. The coating agent is introduced under pressure into the coating-agent chamber and therein enters into direct contact with the base to be coated. The coating blade spreads and smooths a layer of the coating agent of desired thickness onto the surface of the base to be coated. Substantially two different types of devices of this sort are known. On one hand, so-called large-angle-blade coating is known in which, normally, the coating blade forms an angle of several dozens of degrees with the moving base to be coated. On the other hand, so-called mall-angle-blade coating is known, in which the coating blade farms and angle of just a few degrees (normally about 0 to about 10 °) with the moving base to be coated.
An advantage of small-angle-blade coating especially in the coating of board is relatively good unii:ormity of the thickness of the coating layer, which is of signii:icance in view of uniform absorption of printing ink. Further, impurities in the coating mix and/or in the board can by-pass the blade without adhering to it, in which case no streaks arise from the blade. A drawback in small-angle-blade coating is the difficulty in controlling the quantity of coating, for, e.g., when the small angle between the blade and the moving base is changed even just a little to regulate the coating quantity, the quantity of the coating mix applied to the waving base is changed highly extensively.
In small-angle-blade coating, the mast important parameter or regulation of the coating quantity is, as a rule, so-called pre-stressing of the coating blade, which means that the tip of the coating blade is bent mechanically adjusting the distance of the whole applicator device .from the moving base. Further parameters of regulation are the load on the tip portion of the coating blade as well as regulation of the blade angle.
With respect to the prior art, reference is additionally made to bE publication No. 3,446,525, in whose solution the regulation of the coating quantity is arranged so that the dam blades are made mobile. One of the drawbacks of the solution in accordance with said publication is that the dam blade must be .
very rigid in order that the cylinders intended for displacement of the dam blade must be very rigid in order that the cylinders intended for displacement of the dam blade should not bend it.
In the solution of said publication, the regulation of the return flow of the coating agent is arranged as regulation of the size of the return flow gap, in which case the pressure of the coating agent may vary even considerably in the transverse direction of the web. Thus, the device concerned is not suitable for regulation of the profile of the coating quantity.
Further, FI Pat. Appl. No. 861241 describes a method and a device for the coating of paper wherein the coating mix is pre-spread by means of a resilient blade, and the ultimate doctoring is carried out by means of a dragging doctor blade.
The applicator device is placed at the side of the backup roll, and the coating mix rests against the web over a long distance.
In said solution, deaeration of the coating mix is difficult, and integration of the dragging doctor blade in the applicator equipment makes the maintenance operations more difficult. In said solution, in the application zone preceding the smoothing blade, the coating mix is susceptible to disturbances, such as uneven distribution of the coating material. A typical consequence of this is longitudinal streaks that remain in the coating.
The present invention is directed towards achieving a substantial improvement over the prior art so that the coating quantity can be regulated in the desired way in the transverse direction of the machine.
In one aspect of the present invention, there is provided a method for regulation of the quantity of coating applied to a web in a coating station, in which the web is passed over a backup roll and a layer of the coating agent is applied by means of a coating blade loaded against the web, the quantity of coating agent applied to the web being regulated by means of an actuator acting upon the constructions of the coating station, the coating quantity applied to the web being constantly monitored, characterized in that, in order to regulate the transverse profile of the coating quantity, the thickness of the coating is measured in a plurality of transverse zones so as to calculate a measured transverse profile, a differential profile is calculated by comparing the measured transverse profile with the desired transverse profile, and the differential profile is fed as a regulation quantity to a plurality of actuators arranged to adjust the transverse profile of the coating quantity so as to correct the said transverse profile.
In the method aspect of the invention, therefore, a differential profile of the measured transverse profile and the desired transverse profile is calculated. The differential profile is fed as a regulating quantity to the actuators that adjust the transverse profile of the coating quantity so as to correct the transverse profile.
According to a preferred embodiment of the invention, in the method, an equation is approximated by means of calculation, which equation corresponds to the transverse differential profile of the web coating quantity and, out of said equation, the average error and/or the skewness and/or the curvature of the differential profiled and/or the frequency of a cyclic error of coating quantity is/are determined, the parameters corresponding to said values being fed as regulation quantities to the regulators that regulate said properties of the coating quantity so as to correct the transverse profile.
In the method in accordance with the invention, the measured transverse profile of the coating quantity and the desired transverse profile are computed, and the magnitude of the movement of regulation required at the locations of regulation is calculated, by means of which movement of regulation the transverse profile is changed in compliance with the desired transverse profile. In the calculation, the knowledge is utilized that a change in the doctoring force perpendicular to the paper face and present at the tip of the coating blade or a change in the coating quantity to be doctored produces a change in the ultimate coating quantity.
In the coating station aspect of the invention, therefore, the coating station or a separate coating blade arranged after the coating station is provided with support and/or regulation constructions connected with separate actuators and divided in zones in the transverse direction of the web and/or with actuators connected with the frame beam of the coating station or with a separate coating blade, said constructions and/or actuators being connected to said regulation and control circuit in view of correcting the transverse profile of the coating quantity on the basis of the measurement data arriving from the measurement means.
By means of the invention, a number of advantages are achieved over the prior art, a most significant one of these advantages being that the regulation of the coating quantity is carried out as closed regulation and automatically.
According to the invention, the transverse regulation of the coating quantity takes place in several locations of regulation in the transverse direction of the machine. For regulation, constructions mechanically connected to the coating blade are employed, by means of which constructions the doctoring force present at the tip of the blade or the differences produced in the coating quantity to be doctored can be altered.
The further advantages and characteristic features of the invention come out from the following detailed description of the invention.
The following drawings are schematic illustrations of different alternative embodiments of the coating station in accordance with the invention for carrying out the method in accordance with the invention, and are not meant to limit the scope of the invention as encompassed by the claims in which:
Figure 1 is a schematic and partial perspective view of a first alternative embodiment of the coating station in accordance with the invention, in which a support construction that has been divided into zones and that can be pressurized is arranged behind the coating blade;
Figure 2 is a schematic side view of a second alternative embodiment of the coating station in accordance with the invention, in which a rigid support rib is fitted behind the coating blade and in which the doctoring force of the coating blade can be altered by bending the support rib in the desired way;
Figure 3 is substantially equivalent to Fig. 2 viewed from above;
Figure 4 shows an alternative embodiment of the coating station in accordance with the invention in which the coating blade is profiled inductively or magnetically;
Figure 5 is equivalent to Fig. 4 viewed from above;
Figure 6 shows an exemplifying embodiment of the coating station in accordance with the invention in which the regulation of the coating quantity is carried out by restricting the return flows and/or the inlet flows of the coating agent and/or by mechanically profiling the spreading blade;
Figure 7 is an alternative embodiment of the coating station in accordance with the invention in which the curvature of the frame beam of the coating station is corrected and regulated;
Figure 8 is a schematic overall illustration of the regulation system in view of illustrating the various steps in the method of the invention.
In Fig. 1, the backup roll is denoted with the reference numeral 1 and the web that is passed over the backup roll, such as a paper web, with the reference W.
The coating blade 3 included in the coating station construction as shown in Fig. 1 is mounted in a blade holder 7, to which it is attached by means of a blade fastening rib 6. Behind the coating blade 3, near the free tip of the coating blade, a hollow support construction 4 is fitted, which is made of a resilient material and which has been divided into zones in the transverse direction of the coating station.
A pressure regulation pipe 5 is connected to each zone in said resilient, hollow support construction 4, through which pipe a pressure medium, such as gas or liquid, is passed into each zone. The pressure in each zone can be varied in the desired way so that the doctoring force, which acts at that tip of the coating blade 3 upon the material web W and upon the coating agent introduced onto its surface, can be varied in the desired way. Thus, the coating blade 3 can be profiled by feeding pressures of different magnitudes into the different zones in the resilient, hollow support construction 4.
In Fig. 1, only the coating blade 3 with its fastening means and the coating blade 3 with its regulating members are shown of the coating station construction. A
construction as shown in Fig. 1 can, however, be applied, e.g., in connection with prior-art applicators of the short-dwell-time type described above or with applicators of the extruder-spreading type, and equivalent. The coating blade 3 may also be used just in order to smooth and to profile a coating agent that has been spread onto the face of a material web before the coating station construction as shown in Fig. 1. Corresponding applications are also possible in connection with the embodiments of the invention described below.
Figs. 2 and 3 show an embodiment alternative to the coating station construction shown in Fig. 1. In Fig. 2 as well, the backup roll is denoted with the reference numeral 1 and the paper web or equivalent with the reference W. In the embodiment shown in Fig. 2, a rigid support rib 11 is fitted behind the coating blade 10, which rib extends across the width of the coating blade in the transverse direction of the machine. In a way 10 corresponding to Fig. 1, the coating blade 10 is mounted in a blade holder 16, to which it is attached by means of a blade fastening rib 15.
In the embodiment of Fig. 2, a number of actuators 13 are installed in the coating station in the transverse direction of the machine, the spindles 12 of said actuators 13 being attached to the support rib 11. Thus, the support rib 11 has been divided into zones in the transverse direction of the machine, so that an actuator 13 of its own ants upon each zone by the intermediate of a spindle 22. The actuator 13 is such that the spindle 12 of the actuator can be shifted back and forth, i.e. pulled ar pushed.
Thus, by means of each actuator 13, by the intermediate of the spindle 12 and the support rib 11, the coating blade 10 can be loaded towards, or away from, the web W. The actuators 13 are mounted on the frame constructions of the coating station by means of an actuator support 14.
The possibilities of movement of the actuators 13 can be accomplished in a number of different alternative ways. One possible embodiment is an actuator 13 in which the movement produced by it in the spindle 12 is based on the effect of thermal expansion. In such a case, by altering the temperature of the actuator 13, the spindle 12 can be made to move towards, or away from, the web S. Thus, by changing the temperature of the actuators 13, it is possible to locally alter the doctoring force acting, at the tip of 'the coating blade 10, upon the web W
and upon the coating present on the web. The actuator 13 may also operate mechanically, or it may be accomplished as operating in some other suitable way.
The actuators can also be accomplished so that their movement is based on the intensity of an inductively produced or amplified magnetic field. Such an embodiment of the invention is shown in Figs. 4 and 5. In the embodiment of Fig. 4, the backup roll continues to be denoted with the reference numeral 1 and the web with the reference S. Similarly to the preceding embodiments, the coating blade 24 is mounted in a blade holder 26, to which it is attached by means of the blade fastening rib 25.
In the embodiment of Figs. 4 and 5, the actuators, a number of which are placed in the transverse direction of the machine, consist of an electromagnetic device, in which the core 19 of each magnet corresponds to the spindle of an actuator in accordance with the embodiment shown in Figs. 2 and 3. The core 19 of the magnet is provided with a coil 22, which is connected to the voltage source 21 by means of the current circuit 20 of the electromagnet. By changing the intensity and/or the sense of the electric current in the current circuit 20 of the electromagnet, the core 19 of the magnet can be made to move in a way corresponding to the spindle 12 of the actuators shown in Figs. 2 and 3. The core 19 of the magnet may act either directly upon the coating blade 24 or upon a support rib 23 placed behind the coating blade 24, in a way corresponding to Figs. 2 and 3.
Thus, by means of the embodiment shown in Figs. 4 and 5, the same effect is produced on the regulation of the coating quantity as is produced by means of the embodiment shown in Figs. 2 and 3.
Fig. 6 is a schematic illustration of a further embodiment for carrying out the method in accordance with the invention. In Fig. 6, the backup roll is denoted with the reference numeral 1 and the web that runs over the roll with the reference W. In the construction of a coating station as shown in Fig. 6, the spreading blade 30 is mounted in a conventional way in a blade holder, which, together with its fastening members, is denoted with the reference numeral 31 in Fig. 6. In Fig. 6, the coating station construction further includes a guide wall 32, which forms a lip between the inlet flow 41 and the outlet flow of 'the coating agent in the coating station. The return flow duct 40 is defined between the guide wall 32 and the support construction of the spreading blade.
In the coating station in accordance with Fig. 6, the quantity of the coating agent can be changed and regulated in the transverse direction of the machine so that the spreading blade 30 is pushed or pulled in relation to the backup roll 1 by means of the first actuators 34 connected mechanically with the spreading blade 30. There are several actuators 34 connected mechanically with the spreading blade 30. There are several actuators 34 in the transverse direction of the machine so that each of the spindles 35 of the actuators corresponds to a zone of its own in the transverse direction of the machine.
On the other hand, in the embodiment of Fig. 6, the quantity of the coating agent can be changed and regulated in the transverse direction of the machine so that, in the coating station, the return flow of the coating agent is restricted or facilitated by changing the geometry of the return flow duct 40.
This is illustrated in Fig. 6 so that the coating station is provided with second actuators 36, a number of such second actuators fitted in the transverse direction of the machine. The spindle 37 of these actuators are connected to a rib or equivalent placed in the return flow duct 40 so that, by displacing said spindles 37, said rib in the return flaw duct 40 can be shifted to choke or to ease the return flow locally.
Thirdly, in the embodiment of Fig. 6, the quantity of the coating agent can be changed and regulated in the transverse direction of the machine so that the length of the profile bar 33 at the lip between the inlet flow and the return flow is changed or the lip or the profile bar is shifted closer to, or further away from, the backup roll 1. This is illustrated in Fig. 6 so that a number of actuators 38 have been connected to the profile bar 33 by the intermediate of spindles 39, by means of which actuators 38 the profile base 33 can be shifted in the way described above.
In the method in accordance with the invention, the coating quantity on 'the web material is additionally regulated by correcting the curvature of the frame beam of the coating station. This is fully illustrated schematically in Fig. 7.
The operation of the coating station is disturbed by a distortion of the frame beam as a result of the effect of thermal expansion and of mechanical strains. This particular phenomenon is called the curvature of the frame b~aam of the coating station.
In Fig. 7, the coating blade is denoted with the reference numeral 27 and the frame beam of the coating station schematically with the reference numeral 28. The curvature of the frame beam 28 can be corrected, e.g., so that, in the way shown in Fig. 7, the frame beam is provided with ducts for circulation of liquid or gas. Said ducts are fitted in the frame beam 28 so that their distance from the coating blade 27 is different. As said ducts in 'the frame beam 28 axe placid at unequal distances from the coating blade 27, the frame beam can be bent in the desired direction by feeding licyuid ar gas at different temperatures into the duct placed next to the blade and into the duct placed further apart from the blade.
In Fig. 7, 'the temperature of the medium in the duct placed next to the blade is denoted with the reference T~, and the temperature of the medium in the duct placed further apart from the blade is denoted with the reference T2. In Fig. 7, the temperature of the frame beam itself is denoted with the reference TP. The frame beam 28 can also be bent, e.g., by means of hydraulic pressure. As a third alternative, it is possible to use a heating member 29 shown in Fig. 7 and attached to the construction of the frame beam 28, the frame beam 28 being bent in the desired way by changing the temperature TL of said heating member 29.
In the following, a more detailed description will be given of the method of the invention with reference to Fig. 8 in the drawing, in which attempts are made to illustrate the various steps of the method. .
In Fig. 8, the web is denoted with the reference W, the backup roll with the reference numeral 1, and the actuators with the reference numeral 55. Each actuator 55 corresponds to one location of regulation. It is a basic prerequisite of the method that, in the transverse direction of the web, the form of the change in the coating quantity produced by a movement of an actuator in one location or regulation is known. This is called the form of the profile response of the actuator, and it depends an the construction of the coating station intended for the application of the method. The form of the profile response is practically independent from the location in the transverse direction of the machine and from the other conditions of the coating process, such as the composition of the coating agent and the quantity of the coating layer that remains on the web W. The ~~~~~'l absolute magnitude of the profile response is determined separately for each casting process.
As the first stage in the method, the amplification coefficient k is determined, which is obtained by comparing the absolute magnitude of the profile response with the necessary velocity of regulation of the coating quantity. The determination of the amplification coefficient k can be carried out, for example, so that the operator of the machine determines the amplification coefficient and feeds it to the programmable unit 50. The amplification coefficient k may also be self~determined, so that, during the regulation method, the control unit 50 constantly calculates and, if necessary, alters the value of the amplification coefficient.
Secondly, in the method, the transverse profile of the coating quantity present on the web W is measured and compared with the desired transverse profile. In Fig. 8, this is illustrated by means of 'the detectors 54 of measurement of coating quantity, which detectors measure the thickness of the coating quantity and feed the signals corresponding to the measurement data to the control unit 50. Instead of the fixed measurement detectors 54 as shown in Fig. 8, it is also possible to use a traversing measurement detector or detectors running across the web W.
The control unit 50 calculates the difference between the measured transverse profile and the desired transverse profile and presents it as a differential profile of coating quantity.
The desired transverse profile has been programmed in advance into the control unit 50.
After the differential profile has been calculated, further, by calculation, the following parameters are determined from the differential profilee ~~~v~
a a parameter that represents the average value of the difference between the measured profile and the desired profile, i.e. the average error b_ a parameter that represents the skewness of the difference between the measured profile and the desired profile, i.e. of the differential profile c a parameter that represents the convexity or concavity of the difference between the measured profile and the desired profile, i.e. of the differential profile.
I~toreover, the sa-called residual differential profile is determined from the differential profile by calculation.
The parameters a, b_ and c as well as the residual differential profile are determined by means of approximation of a parabolic equation which corresponds to the differential profile as well as possible. Said parabolic equation is y = d ~ f (mt) ~ (a -H bx + cx2) , wherein y = coating quantity x = transverse coordinai~e (the origin is in the middle of the web) a,b,c = parameters to be determined, mentioned above t = time d = magnitude of cyclic error in coating quantity a = frequency of cyclic error in coating quantity The parameters d and W are used in actuators whose frequency response permits a speed of displacement of about 20 Hz. They are employed for correction of a cyclic error in the coating quantity in the machine direction by means of a cyclic movement fed to all location of regulation. Said cyclic error in the coating quantity arises, for example, from unevenness in the ~~~'~~~
backup roll, and, when these parameters d and w are taken into account, it is easier to eliminate said cyclic error.
If it is desirable to regulate some of the factors mentioned above only, i.e. to allow them to be regulated through the residual differential profile, the parameters that represent the factoxs to be omitted are given the value 0. The residual differential profile is determined so that the parabola given above is subtracted from the calculated differential profile, which is presented as a function between the transverse position on the web and the coating quantity.
As the next step in the method, the value of the parameter a is transmitted from the control unit 50 to the first regulation device 51, by whose means the value of the coating quantity in the machine direction can be changed. The value in the machine direction can be changed by means of the regulation device 51 either directly through the spindle of the actuators 55 or by displacing the coating unit as a whole, which is illustrated by the regulation line L in Fig. 8. In a corresponding way, the value of the determined parameter b is transmitted to the second regulation device 52, b whose means the: skewness of the coating station can be corrected. Further, thE: value of the parameter c is transmitted to the third regulation device 53, by whose means the curvature of the frame beam of the coating station can be corrected. Thus, the regulation devices 51,52 and 53 operate as "pre--regulators", and the fine adjustment of the profile is carried out by means of the actuators 55.
Next, the movement of the actuator required at the locations of regulation is determined by, each in its turn, comparing the known profile responses of the locations of regulation with the residual differential profiles prevailing to them, by multiplying the local value of the residual differential profile with the amplification coefficient k, by dividing the result by the profile response of the location of regulation, and by adding together the results for the different locations of regulation.
The corresponding required movement profile of the actuator is determined by combining the required movements of actuator calculated in respect of each location of regulation. In such a case, the control unit 50 and the regulation devices 51,52,53 attempt to regulate the profile of coating quantity so that, in the parabalic equation given above, the values of the parameters a,b,c and the residual differential profile become equal to zero.
The movements of regulation calculated by the method produce a time-dependent error in the coating quantity arriving on the web W especially when the embodiments illustrated in Figs. Z to 3 are used in a coating station in accordance with the invention.
Z5 Since the regulation method in accordance with the invention, however, follows the principle of a closed regulation circuit in accordance with the above, the closing of the regulation has the effect that the error produced is corrected immediately during the next cycle of regulation. In this way, the error is eliminated with a delay determined by t:he velocities of the measurement and calculation methods and by the speeds of movement of the actuators.
As was already stated above, the coating stations intended for carrying out the method in accordance with the invention convert the movement profiles of the actuators produced by mans of measurement and calculation into doctoring forces of the coating blade or into coating quantities to be doctored at the locations of regulation placed in the transverse direction of the web. Regarding the constructions of coating stations, it should be stated further that, for example, when such solutions of the embodiments as shown in Figs. 2 to 5 are employed in which the area of contact with the coating blade, 10,24, which is produced by the actuators, is very near the free tip of the coating blade, the advantage is obtained that the angle between the coating blade 10,24 and the web W remains almost invariable during the ' movements of regulation. This is why, after a movement of regulation, the coating quantity is changed directly to its correct value and a grinding of the coating blade 10,24 does not cause time-dependent errors in the coating quantity, which errors are noticed in most coating processes. Earlier, this possibility was limited by sensitivity to variations in the doctoring force produced by dynamic disturbance arising either from the construction of the equipment or from the process, with resulting errors in the coating quantity.
In the embodiments of the coating station as shown in Figs.
2 to 5 with the exception of fully mechanical operation, the physical processes that produce the movements of the actuators are very rapid, so that they can be regulated rapidly immediately after the disturbance noticed by means of measurement. They can also be synchronized with a possible dynamic disturbance that may occur cyclically. By means of a solution as shown in Fig. 1, it is also possible to achieve corresponding rapid operation, because the volumes in the hollow support construction 4 are small.
Besides those described above, the embodiment as shown in Figs. 4 and 5 is also self~adjusting so that a dynamic disturbance produces a movement in the actuators, which movement produces a change opposed to the movement in 'the current circuit.
The tip of the coating blade 24 remains at the same angle in relation to the web W, but the doctoring force is changed.
Hereby it is possible to avoid a time-dependent error in the coating quantity arising from a change in the blade angle.
It is an advantage of the embodiments shown in Fig. 6 that the coating blade 30 does not have to be affected to produce regulation in the transverse direction. This completely eliminates the formation of a time-dependent error in coating quantity which might result from a change in the blade angle.
Here the starting point has been practical observations according to which, when a solution of equipment is used in which a layer of coating agent is first spread onto the face of the web W, which layer is then smoothed by means of a smoothing blade placed after the coating device proper, the quantity of coating agent that was spread onto the face of the web W affects the quantity of coating agent that remains on the web W after the ultimate doctoring coating blade.
Above, the invention has been described by way of example with reference to the exemplifying embodiments shown in the figures in the accompanying drawing. The examples provided above are not meant to be exclusive. Many other variations of the present invention would be obvious to those skilled in the art, and are contemplated to be within the scope of the appended claims.
In the method in accordance with the invention, the measured transverse profile of the coating quantity and the desired transverse profile are computed, and the magnitude of the movement of regulation required at the locations of regulation is calculated, by means of which movement of regulation the transverse profile is changed in compliance with the desired transverse profile. In the calculation, the knowledge is utilized that a change in the doctoring force perpendicular to the paper face and present at the tip of the coating blade or a change in the coating quantity to be doctored produces a change in the ultimate coating quantity.
In the coating station aspect of the invention, therefore, the coating station or a separate coating blade arranged after the coating station is provided with support and/or regulation constructions connected with separate actuators and divided in zones in the transverse direction of the web and/or with actuators connected with the frame beam of the coating station or with a separate coating blade, said constructions and/or actuators being connected to said regulation and control circuit in view of correcting the transverse profile of the coating quantity on the basis of the measurement data arriving from the measurement means.
By means of the invention, a number of advantages are achieved over the prior art, a most significant one of these advantages being that the regulation of the coating quantity is carried out as closed regulation and automatically.
According to the invention, the transverse regulation of the coating quantity takes place in several locations of regulation in the transverse direction of the machine. For regulation, constructions mechanically connected to the coating blade are employed, by means of which constructions the doctoring force present at the tip of the blade or the differences produced in the coating quantity to be doctored can be altered.
The further advantages and characteristic features of the invention come out from the following detailed description of the invention.
The following drawings are schematic illustrations of different alternative embodiments of the coating station in accordance with the invention for carrying out the method in accordance with the invention, and are not meant to limit the scope of the invention as encompassed by the claims in which:
Figure 1 is a schematic and partial perspective view of a first alternative embodiment of the coating station in accordance with the invention, in which a support construction that has been divided into zones and that can be pressurized is arranged behind the coating blade;
Figure 2 is a schematic side view of a second alternative embodiment of the coating station in accordance with the invention, in which a rigid support rib is fitted behind the coating blade and in which the doctoring force of the coating blade can be altered by bending the support rib in the desired way;
Figure 3 is substantially equivalent to Fig. 2 viewed from above;
Figure 4 shows an alternative embodiment of the coating station in accordance with the invention in which the coating blade is profiled inductively or magnetically;
Figure 5 is equivalent to Fig. 4 viewed from above;
Figure 6 shows an exemplifying embodiment of the coating station in accordance with the invention in which the regulation of the coating quantity is carried out by restricting the return flows and/or the inlet flows of the coating agent and/or by mechanically profiling the spreading blade;
Figure 7 is an alternative embodiment of the coating station in accordance with the invention in which the curvature of the frame beam of the coating station is corrected and regulated;
Figure 8 is a schematic overall illustration of the regulation system in view of illustrating the various steps in the method of the invention.
In Fig. 1, the backup roll is denoted with the reference numeral 1 and the web that is passed over the backup roll, such as a paper web, with the reference W.
The coating blade 3 included in the coating station construction as shown in Fig. 1 is mounted in a blade holder 7, to which it is attached by means of a blade fastening rib 6. Behind the coating blade 3, near the free tip of the coating blade, a hollow support construction 4 is fitted, which is made of a resilient material and which has been divided into zones in the transverse direction of the coating station.
A pressure regulation pipe 5 is connected to each zone in said resilient, hollow support construction 4, through which pipe a pressure medium, such as gas or liquid, is passed into each zone. The pressure in each zone can be varied in the desired way so that the doctoring force, which acts at that tip of the coating blade 3 upon the material web W and upon the coating agent introduced onto its surface, can be varied in the desired way. Thus, the coating blade 3 can be profiled by feeding pressures of different magnitudes into the different zones in the resilient, hollow support construction 4.
In Fig. 1, only the coating blade 3 with its fastening means and the coating blade 3 with its regulating members are shown of the coating station construction. A
construction as shown in Fig. 1 can, however, be applied, e.g., in connection with prior-art applicators of the short-dwell-time type described above or with applicators of the extruder-spreading type, and equivalent. The coating blade 3 may also be used just in order to smooth and to profile a coating agent that has been spread onto the face of a material web before the coating station construction as shown in Fig. 1. Corresponding applications are also possible in connection with the embodiments of the invention described below.
Figs. 2 and 3 show an embodiment alternative to the coating station construction shown in Fig. 1. In Fig. 2 as well, the backup roll is denoted with the reference numeral 1 and the paper web or equivalent with the reference W. In the embodiment shown in Fig. 2, a rigid support rib 11 is fitted behind the coating blade 10, which rib extends across the width of the coating blade in the transverse direction of the machine. In a way 10 corresponding to Fig. 1, the coating blade 10 is mounted in a blade holder 16, to which it is attached by means of a blade fastening rib 15.
In the embodiment of Fig. 2, a number of actuators 13 are installed in the coating station in the transverse direction of the machine, the spindles 12 of said actuators 13 being attached to the support rib 11. Thus, the support rib 11 has been divided into zones in the transverse direction of the machine, so that an actuator 13 of its own ants upon each zone by the intermediate of a spindle 22. The actuator 13 is such that the spindle 12 of the actuator can be shifted back and forth, i.e. pulled ar pushed.
Thus, by means of each actuator 13, by the intermediate of the spindle 12 and the support rib 11, the coating blade 10 can be loaded towards, or away from, the web W. The actuators 13 are mounted on the frame constructions of the coating station by means of an actuator support 14.
The possibilities of movement of the actuators 13 can be accomplished in a number of different alternative ways. One possible embodiment is an actuator 13 in which the movement produced by it in the spindle 12 is based on the effect of thermal expansion. In such a case, by altering the temperature of the actuator 13, the spindle 12 can be made to move towards, or away from, the web S. Thus, by changing the temperature of the actuators 13, it is possible to locally alter the doctoring force acting, at the tip of 'the coating blade 10, upon the web W
and upon the coating present on the web. The actuator 13 may also operate mechanically, or it may be accomplished as operating in some other suitable way.
The actuators can also be accomplished so that their movement is based on the intensity of an inductively produced or amplified magnetic field. Such an embodiment of the invention is shown in Figs. 4 and 5. In the embodiment of Fig. 4, the backup roll continues to be denoted with the reference numeral 1 and the web with the reference S. Similarly to the preceding embodiments, the coating blade 24 is mounted in a blade holder 26, to which it is attached by means of the blade fastening rib 25.
In the embodiment of Figs. 4 and 5, the actuators, a number of which are placed in the transverse direction of the machine, consist of an electromagnetic device, in which the core 19 of each magnet corresponds to the spindle of an actuator in accordance with the embodiment shown in Figs. 2 and 3. The core 19 of the magnet is provided with a coil 22, which is connected to the voltage source 21 by means of the current circuit 20 of the electromagnet. By changing the intensity and/or the sense of the electric current in the current circuit 20 of the electromagnet, the core 19 of the magnet can be made to move in a way corresponding to the spindle 12 of the actuators shown in Figs. 2 and 3. The core 19 of the magnet may act either directly upon the coating blade 24 or upon a support rib 23 placed behind the coating blade 24, in a way corresponding to Figs. 2 and 3.
Thus, by means of the embodiment shown in Figs. 4 and 5, the same effect is produced on the regulation of the coating quantity as is produced by means of the embodiment shown in Figs. 2 and 3.
Fig. 6 is a schematic illustration of a further embodiment for carrying out the method in accordance with the invention. In Fig. 6, the backup roll is denoted with the reference numeral 1 and the web that runs over the roll with the reference W. In the construction of a coating station as shown in Fig. 6, the spreading blade 30 is mounted in a conventional way in a blade holder, which, together with its fastening members, is denoted with the reference numeral 31 in Fig. 6. In Fig. 6, the coating station construction further includes a guide wall 32, which forms a lip between the inlet flow 41 and the outlet flow of 'the coating agent in the coating station. The return flow duct 40 is defined between the guide wall 32 and the support construction of the spreading blade.
In the coating station in accordance with Fig. 6, the quantity of the coating agent can be changed and regulated in the transverse direction of the machine so that the spreading blade 30 is pushed or pulled in relation to the backup roll 1 by means of the first actuators 34 connected mechanically with the spreading blade 30. There are several actuators 34 connected mechanically with the spreading blade 30. There are several actuators 34 in the transverse direction of the machine so that each of the spindles 35 of the actuators corresponds to a zone of its own in the transverse direction of the machine.
On the other hand, in the embodiment of Fig. 6, the quantity of the coating agent can be changed and regulated in the transverse direction of the machine so that, in the coating station, the return flow of the coating agent is restricted or facilitated by changing the geometry of the return flow duct 40.
This is illustrated in Fig. 6 so that the coating station is provided with second actuators 36, a number of such second actuators fitted in the transverse direction of the machine. The spindle 37 of these actuators are connected to a rib or equivalent placed in the return flow duct 40 so that, by displacing said spindles 37, said rib in the return flaw duct 40 can be shifted to choke or to ease the return flow locally.
Thirdly, in the embodiment of Fig. 6, the quantity of the coating agent can be changed and regulated in the transverse direction of the machine so that the length of the profile bar 33 at the lip between the inlet flow and the return flow is changed or the lip or the profile bar is shifted closer to, or further away from, the backup roll 1. This is illustrated in Fig. 6 so that a number of actuators 38 have been connected to the profile bar 33 by the intermediate of spindles 39, by means of which actuators 38 the profile base 33 can be shifted in the way described above.
In the method in accordance with the invention, the coating quantity on 'the web material is additionally regulated by correcting the curvature of the frame beam of the coating station. This is fully illustrated schematically in Fig. 7.
The operation of the coating station is disturbed by a distortion of the frame beam as a result of the effect of thermal expansion and of mechanical strains. This particular phenomenon is called the curvature of the frame b~aam of the coating station.
In Fig. 7, the coating blade is denoted with the reference numeral 27 and the frame beam of the coating station schematically with the reference numeral 28. The curvature of the frame beam 28 can be corrected, e.g., so that, in the way shown in Fig. 7, the frame beam is provided with ducts for circulation of liquid or gas. Said ducts are fitted in the frame beam 28 so that their distance from the coating blade 27 is different. As said ducts in 'the frame beam 28 axe placid at unequal distances from the coating blade 27, the frame beam can be bent in the desired direction by feeding licyuid ar gas at different temperatures into the duct placed next to the blade and into the duct placed further apart from the blade.
In Fig. 7, 'the temperature of the medium in the duct placed next to the blade is denoted with the reference T~, and the temperature of the medium in the duct placed further apart from the blade is denoted with the reference T2. In Fig. 7, the temperature of the frame beam itself is denoted with the reference TP. The frame beam 28 can also be bent, e.g., by means of hydraulic pressure. As a third alternative, it is possible to use a heating member 29 shown in Fig. 7 and attached to the construction of the frame beam 28, the frame beam 28 being bent in the desired way by changing the temperature TL of said heating member 29.
In the following, a more detailed description will be given of the method of the invention with reference to Fig. 8 in the drawing, in which attempts are made to illustrate the various steps of the method. .
In Fig. 8, the web is denoted with the reference W, the backup roll with the reference numeral 1, and the actuators with the reference numeral 55. Each actuator 55 corresponds to one location of regulation. It is a basic prerequisite of the method that, in the transverse direction of the web, the form of the change in the coating quantity produced by a movement of an actuator in one location or regulation is known. This is called the form of the profile response of the actuator, and it depends an the construction of the coating station intended for the application of the method. The form of the profile response is practically independent from the location in the transverse direction of the machine and from the other conditions of the coating process, such as the composition of the coating agent and the quantity of the coating layer that remains on the web W. The ~~~~~'l absolute magnitude of the profile response is determined separately for each casting process.
As the first stage in the method, the amplification coefficient k is determined, which is obtained by comparing the absolute magnitude of the profile response with the necessary velocity of regulation of the coating quantity. The determination of the amplification coefficient k can be carried out, for example, so that the operator of the machine determines the amplification coefficient and feeds it to the programmable unit 50. The amplification coefficient k may also be self~determined, so that, during the regulation method, the control unit 50 constantly calculates and, if necessary, alters the value of the amplification coefficient.
Secondly, in the method, the transverse profile of the coating quantity present on the web W is measured and compared with the desired transverse profile. In Fig. 8, this is illustrated by means of 'the detectors 54 of measurement of coating quantity, which detectors measure the thickness of the coating quantity and feed the signals corresponding to the measurement data to the control unit 50. Instead of the fixed measurement detectors 54 as shown in Fig. 8, it is also possible to use a traversing measurement detector or detectors running across the web W.
The control unit 50 calculates the difference between the measured transverse profile and the desired transverse profile and presents it as a differential profile of coating quantity.
The desired transverse profile has been programmed in advance into the control unit 50.
After the differential profile has been calculated, further, by calculation, the following parameters are determined from the differential profilee ~~~v~
a a parameter that represents the average value of the difference between the measured profile and the desired profile, i.e. the average error b_ a parameter that represents the skewness of the difference between the measured profile and the desired profile, i.e. of the differential profile c a parameter that represents the convexity or concavity of the difference between the measured profile and the desired profile, i.e. of the differential profile.
I~toreover, the sa-called residual differential profile is determined from the differential profile by calculation.
The parameters a, b_ and c as well as the residual differential profile are determined by means of approximation of a parabolic equation which corresponds to the differential profile as well as possible. Said parabolic equation is y = d ~ f (mt) ~ (a -H bx + cx2) , wherein y = coating quantity x = transverse coordinai~e (the origin is in the middle of the web) a,b,c = parameters to be determined, mentioned above t = time d = magnitude of cyclic error in coating quantity a = frequency of cyclic error in coating quantity The parameters d and W are used in actuators whose frequency response permits a speed of displacement of about 20 Hz. They are employed for correction of a cyclic error in the coating quantity in the machine direction by means of a cyclic movement fed to all location of regulation. Said cyclic error in the coating quantity arises, for example, from unevenness in the ~~~'~~~
backup roll, and, when these parameters d and w are taken into account, it is easier to eliminate said cyclic error.
If it is desirable to regulate some of the factors mentioned above only, i.e. to allow them to be regulated through the residual differential profile, the parameters that represent the factoxs to be omitted are given the value 0. The residual differential profile is determined so that the parabola given above is subtracted from the calculated differential profile, which is presented as a function between the transverse position on the web and the coating quantity.
As the next step in the method, the value of the parameter a is transmitted from the control unit 50 to the first regulation device 51, by whose means the value of the coating quantity in the machine direction can be changed. The value in the machine direction can be changed by means of the regulation device 51 either directly through the spindle of the actuators 55 or by displacing the coating unit as a whole, which is illustrated by the regulation line L in Fig. 8. In a corresponding way, the value of the determined parameter b is transmitted to the second regulation device 52, b whose means the: skewness of the coating station can be corrected. Further, thE: value of the parameter c is transmitted to the third regulation device 53, by whose means the curvature of the frame beam of the coating station can be corrected. Thus, the regulation devices 51,52 and 53 operate as "pre--regulators", and the fine adjustment of the profile is carried out by means of the actuators 55.
Next, the movement of the actuator required at the locations of regulation is determined by, each in its turn, comparing the known profile responses of the locations of regulation with the residual differential profiles prevailing to them, by multiplying the local value of the residual differential profile with the amplification coefficient k, by dividing the result by the profile response of the location of regulation, and by adding together the results for the different locations of regulation.
The corresponding required movement profile of the actuator is determined by combining the required movements of actuator calculated in respect of each location of regulation. In such a case, the control unit 50 and the regulation devices 51,52,53 attempt to regulate the profile of coating quantity so that, in the parabalic equation given above, the values of the parameters a,b,c and the residual differential profile become equal to zero.
The movements of regulation calculated by the method produce a time-dependent error in the coating quantity arriving on the web W especially when the embodiments illustrated in Figs. Z to 3 are used in a coating station in accordance with the invention.
Z5 Since the regulation method in accordance with the invention, however, follows the principle of a closed regulation circuit in accordance with the above, the closing of the regulation has the effect that the error produced is corrected immediately during the next cycle of regulation. In this way, the error is eliminated with a delay determined by t:he velocities of the measurement and calculation methods and by the speeds of movement of the actuators.
As was already stated above, the coating stations intended for carrying out the method in accordance with the invention convert the movement profiles of the actuators produced by mans of measurement and calculation into doctoring forces of the coating blade or into coating quantities to be doctored at the locations of regulation placed in the transverse direction of the web. Regarding the constructions of coating stations, it should be stated further that, for example, when such solutions of the embodiments as shown in Figs. 2 to 5 are employed in which the area of contact with the coating blade, 10,24, which is produced by the actuators, is very near the free tip of the coating blade, the advantage is obtained that the angle between the coating blade 10,24 and the web W remains almost invariable during the ' movements of regulation. This is why, after a movement of regulation, the coating quantity is changed directly to its correct value and a grinding of the coating blade 10,24 does not cause time-dependent errors in the coating quantity, which errors are noticed in most coating processes. Earlier, this possibility was limited by sensitivity to variations in the doctoring force produced by dynamic disturbance arising either from the construction of the equipment or from the process, with resulting errors in the coating quantity.
In the embodiments of the coating station as shown in Figs.
2 to 5 with the exception of fully mechanical operation, the physical processes that produce the movements of the actuators are very rapid, so that they can be regulated rapidly immediately after the disturbance noticed by means of measurement. They can also be synchronized with a possible dynamic disturbance that may occur cyclically. By means of a solution as shown in Fig. 1, it is also possible to achieve corresponding rapid operation, because the volumes in the hollow support construction 4 are small.
Besides those described above, the embodiment as shown in Figs. 4 and 5 is also self~adjusting so that a dynamic disturbance produces a movement in the actuators, which movement produces a change opposed to the movement in 'the current circuit.
The tip of the coating blade 24 remains at the same angle in relation to the web W, but the doctoring force is changed.
Hereby it is possible to avoid a time-dependent error in the coating quantity arising from a change in the blade angle.
It is an advantage of the embodiments shown in Fig. 6 that the coating blade 30 does not have to be affected to produce regulation in the transverse direction. This completely eliminates the formation of a time-dependent error in coating quantity which might result from a change in the blade angle.
Here the starting point has been practical observations according to which, when a solution of equipment is used in which a layer of coating agent is first spread onto the face of the web W, which layer is then smoothed by means of a smoothing blade placed after the coating device proper, the quantity of coating agent that was spread onto the face of the web W affects the quantity of coating agent that remains on the web W after the ultimate doctoring coating blade.
Above, the invention has been described by way of example with reference to the exemplifying embodiments shown in the figures in the accompanying drawing. The examples provided above are not meant to be exclusive. Many other variations of the present invention would be obvious to those skilled in the art, and are contemplated to be within the scope of the appended claims.
Claims (33)
1. A method for regulation of the quantity of coating agent applied to a web in a coating station, in which the web is passed over a backup roll and a layer of the coating agent is applied by means of a coating blade loaded against the web, the quantity of coating agent applied to the web being regulated by means of an actuator acting upon constructions of the coating station, the coating quantity applied to the web being constantly monitored, wherein, in order to regulate a transverse profile of the coating quantity, the thickness of the coating is measured in a plurality of transverse zones so as to calculate a measured transverse profile, a differential profile is calculated by comparing the measured transverse profile with a desired transverse profile, and the differential profile is fed as a regulation quantity to a plurality of actuators arranged to adjust the transverse profile of the coating quantity so as to correct the transverse profile.
2. Method as claimed in claim 1, wherein in the method an equation is approximated by means of calculation, which equation corresponds to a transverse differential profile of the coating quantity on the web between the measured transverse profile and the desired transverse profile, and out of said equation, an average error and/or a skewness and/or a curvature of the differential profile and/or a frequency of a cyclic error in coating quantity is/are determined, the parameters corresponding to said values being fed as regulation quantities to regulation devices that regulate properties of the coating quantity so as to correct the transverse profile.
3. Method as claimed in claim 2, wherein the parameters corresponding to an average error and/or to a magnitude of a cyclic error in the coating quantity and/or to a frequency of a cyclic error in the coating quantity are fed as regulation quantities to a regulation device that corrects the average value of the coating quantity.
4. Method as claimed in claim 2, wherein the parameters corresponding to a magnitude of a cyclic error in the coating quantity and/or to a frequency of a cyclic error in the coating quantity are fed as regulation quantities to the actuators that regulate the transverse profile of the coating quantity.
5. Method as claimed in any one of claims 2 to 4, wherein in the method a parabolic equation is approximated.
6. Method as claimed in any one of claims 2 to 5, wherein in the method a residual differential profile of the coating quantity is determined by subtracting an approximated equation that represents the differential profile from the measured and calculated differential profile.
7. Method as claimed in any one of claims 1 to 6, wherein in required movement of the actuators placed at locations of regulation is determined by comparing a known profile response of each location of regulation, the form of the change in the coating quantity produced by a movement of the actuator, with a residual differential profile prevailing at a location of regulation concerned, and the actuators are given a corresponding regulation impulse so as to correct the differential profile.
8. Method as claimed in claim 7, wherein the movement of an actuator required at locations of regulation is determined by locally multiplying the value of the residual differential profile by an amplification coefficient and by dividing a result by a profile response of a location of regulation, whereby the amplification coefficient is determined by comparing an absolute magnitude of the profile response with a required speed of regulation of the coating quantity.
9. Method as claimed in any one of claims 1 to 8, wherein in view of correcting the profile of the coating quantity, movement profiles of the actuators are determined by combining required movements of the actuators calculated at each location of regulation.
10. Method as claimed in any one of claims 1 to 9, wherein the method is continued as closed regulation method so that during each cycle of the regulation the coating quantity is again measured after a previous profile correction.
11. Method as claimed in any one of claims 1 to 10, wherein during each cycle of closed regulation or after a certain number of cycles a new value is determined for an amplification coefficient of a location of regulation.
12. Method as claimed in any one of claims 1 to 11, wherein the transverse profile of the coating quantity is regulated by regulating the profile of the coating blade by means of the actuators acting upon the coating blade directly or through a support rib.
13. Method as claimed in claim 12, wherein the profile of the coating blade is regulated by loading the coating blade towards the web by means of the actuators fitted at several locations in the transverse direction of the web by pulling said blade apart from the web.
14. Method as claimed in claim 12 or 13, wherein the movements of the actuators are produced by hydraulic or pneumatic pressure.
15. Method as claimed in claim 12 or 13, wherein the movements of the actuators are produced mechanically.
16. Method as claimed in claim 12 or 13, wherein the movements of the actuators are produced by means of the effect of thermal expansion by heating and cooling the actuators.
17. Method as claimed in claim 12 ar 13, wherein the movements of the actuators are produced inductively or electromagnetically.
18. Method as claimed in any one of claims 1 to 11, wherein the transverse profile of the coating quantity is regulated by regulating the flow of the coating agent.
19. Method as claimed in any one of claims 1 to 18 wherein a skewness of the differential profile of the coating quantity is corrected by turning the coating station or a frame beam of the coating station.
20. Method as claimed in any one of claims 1 to 19, wherein a convexity or concavity of the differential profile of the coating quantity is corrected by bending a frame beam of the coating station.
21. Method as claimed in claim 20, wherein the frame beam is bent by means of differences in temperature produced in the frame beam.
22. Method as claimed in claim 20, wherein the frame beam is bent by loading it hydraulically or mechanically.
23. Coating station intended for carrying out a method as claimed in any one of claims 1 to 22, wherein the web is passed to run over a backup roll and which coating station is provided with the coating blade loaded against the web, said blade being mounted in a blade holder supported on a frame beam of the coating station, and which coating station is, by the intermediate of a regulation and control circuit, connected with a detector for measurement of the coating quantity applied to the web, wherein the coating station is provided with detectors arranged in a plurality of transverse zones, and the coating station or a separate coating blade arranged after the coating station is provided with support and/or regulation constructions connected with separate actuators and arranged in complementary transverse relation and/or with actuators connected with the frame beam of the coating station or with a separate coating blade, said constructions and/or actuators being connected to said regulation and control circuit in view of correcting the transverse profile of the coating quantity on the basis of measurement data arriving from the detectors.
24. Coating station as claimed in claim 23, wherein regulation and/or support construction that is divided in zones comprises actuators which act upon the coating blade or upon a spreading blade at a number of locations in the transverse direction of the web and which are arranged to load the coating blade or the spreading blade towards the web or to pull it apart from the web.
25. Coating station as claimed in claim 24, wherein said regulation or support construction comprises a hollow and resilient support construction, which is divided in zones, which is mounted behind the coating blade or spreading blade, and which is fitted to be loaded by means of hydraulic or pneumatic pressure.
26. Coating station as claimed in claim 24, wherein said regulation or support construction comprises a support rib, which is fitted behind the coating blade or spreading blade and which is connected in zones with the actuators, by whose means the support rib can be pulled and pushed.
27. Coating station as claimed in claim 24, wherein said regulation or support construction comprises heatable or coolable actuators, which are fitted, based on the effect of thermal expansion, to load the coating blade or the spreading blade.
28. Coating station as claimed in claim 24, wherein the actuators operate inductively or electromagnetically.
29. Coating station as claimed in claim 23, wherein the regulation or support construction comprises the actuators for regulation of flows of the coating agent.
30. Coating station as claimed in any one of claims 23 to 29, wherein the actuators, which are connected to the frame beam of the coating station, comprise means for producing a change in temperature in the frame beam in order to bend the frame beam.
31. Coating station as claimed in claim 30, wherein ducts have been formed into the frame beam for circulation of a heat-regulation medium.
32. Coating station as claimed in claim 30, wherein a separate heating member is connected to the frame beam.
33. Coating station as claimed in any one of claims 23 to 29, wherein the actuators connected to the frame beam are hydraulic, being fitted to correct the position and/or the bending of the frame beam by the effect of hydraulic pressure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI910616A FI91025C (en) | 1991-02-08 | 1991-02-08 | Method for adjusting the cross-sectional profile of the amount of paper or other web material and a coating station for carrying out the method |
| FI910616 | 1991-02-08 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2060769A1 CA2060769A1 (en) | 1992-08-09 |
| CA2060769C true CA2060769C (en) | 2005-10-04 |
Family
ID=8531886
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2060769 Expired - Fee Related CA2060769C (en) | 1991-02-08 | 1992-02-06 | Method for regulation of the transverse profile of the coating quantity on a web material and coating station for carrying out the method |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA2060769C (en) |
| DE (1) | DE4203398C2 (en) |
| FI (1) | FI91025C (en) |
| GB (1) | GB2252926B (en) |
| SE (1) | SE509562C2 (en) |
Families Citing this family (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4334556A1 (en) * | 1993-10-11 | 1995-04-13 | Jagenberg Ag | Device for coating a material web, in particular a paper or cardboard web |
| US5480486A (en) * | 1993-12-21 | 1996-01-02 | Beloit Technologies, Inc. | Continuous adjustable backing bar for profiling coater blade |
| FI105260B (en) * | 1994-10-24 | 2000-07-14 | Valmet Paper Machinery Inc | Method and Arrangement for Adjusting the Coating Profile in Short-Dwell Type Coating |
| DE29506731U1 (en) * | 1995-04-20 | 1995-06-22 | Voith Sulzer Papiermasch Gmbh | Application work for coating a running web, in particular made of paper or cardboard |
| GB2305873B (en) * | 1995-10-07 | 1999-06-02 | Crabtree Gateshead Ltd | Roll cleaning assembly |
| DE19627456A1 (en) * | 1996-07-08 | 1998-01-15 | Voith Sulzer Papiermasch Gmbh | Coater for use in web products, especially paper or paper board |
| EP0821102B1 (en) * | 1996-07-08 | 2002-03-27 | Voith Paper Patent GmbH | Apparatus for applying directly a fluid or pasty material onto a moving web, especially of paper or paperboard |
| DE19627489A1 (en) * | 1996-07-08 | 1998-01-15 | Voith Sulzer Papiermasch Gmbh | Web coating applicator |
| DE19627470A1 (en) * | 1996-07-08 | 1998-01-15 | Voith Sulzer Papiermasch Gmbh | Web coating applicator for use in coating web of paper or fabric |
| DE19631888A1 (en) * | 1996-08-07 | 1998-02-12 | Voith Sulzer Papiermasch Gmbh | Applicator for direct or indirect application of a liquid or pasty coating medium to a running material web, in particular made of paper or cardboard |
| DE19637164A1 (en) * | 1996-09-12 | 1998-03-19 | Voith Sulzer Papiermasch Gmbh | Method and device for the direct or indirect application of a liquid or pasty medium to a running material web |
| FI109215B (en) * | 1996-10-28 | 2002-06-14 | Metso Paper Inc | Method and apparatus for coating paper or cardboard web |
| DE29622365U1 (en) * | 1996-12-23 | 1997-06-19 | Voith Sulzer Papiermasch Gmbh | Application unit for direct or indirect application of a liquid or pasty medium to a running material web |
| DE19700633B4 (en) * | 1997-01-10 | 2005-06-02 | Voith Sulzer Papiermaschinen Gmbh | Apparatus for applying a liquid or pasty medium to a moving material web, preferably of paper or cardboard, and machine for paper or board production |
| DE29701176U1 (en) * | 1997-01-24 | 1997-05-22 | Voith Sulzer Papiermasch Gmbh | Device for the direct or indirect application of a liquid or pasty application medium to a running material web |
| DE19715117A1 (en) * | 1997-04-11 | 1998-10-15 | Voith Sulzer Papiermasch Gmbh | Assembly to coat a moving web |
| DE19723458A1 (en) * | 1997-06-04 | 1998-12-10 | Voith Sulzer Papiermasch Gmbh | Device and method for applying a liquid or pasty medium to a moving surface |
| DE19734718A1 (en) * | 1997-08-11 | 1999-02-18 | Voith Sulzer Papiermasch Gmbh | Web coating applicator |
| DE19801140A1 (en) * | 1998-01-14 | 1999-07-15 | Voith Sulzer Papiertech Patent | Device for the direct or indirect application of a liquid to pasty application medium on a running material web and operating method for such a device |
| US6235115B1 (en) * | 1998-01-27 | 2001-05-22 | Beloit Technologies, Inc. | Fountain coating applicator and support beam |
| DE19803240A1 (en) * | 1998-01-28 | 1999-07-29 | Voith Sulzer Papiertech Patent | Paint curtain applicator |
| DE19812929A1 (en) * | 1998-03-24 | 1999-09-30 | Voith Sulzer Papiertech Patent | Machine continuously metering and leveling coating of fluid or viscous material |
| DE102006018525A1 (en) * | 2006-04-21 | 2007-10-25 | Man Roland Druckmaschinen Ag | Squeegee device for color deck washing, has elastic squeegee cutter forming doctor blade, and supported with respect to color deck roller, so that blade is brought into mechanical contact with surface of color deck roller for cleaning |
| DE102018009535A1 (en) * | 2018-12-07 | 2020-06-10 | Andritz Küsters Gmbh | Commissioned work for the direct or indirect application of a coating medium |
| DE102022112542A1 (en) | 2022-05-19 | 2023-11-23 | Voith Patent Gmbh | Device, use and method for dosing or leveling |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3079889A (en) * | 1959-06-03 | 1963-03-05 | Black Clawson Co | Paper machinery |
| US3301214A (en) * | 1964-03-10 | 1967-01-31 | Black Clawson Co | Paper machinery coating doctor blade backs |
| FI47398C (en) * | 1967-06-22 | 1973-11-12 | Valmet Oy | Scraper device. |
| DE2913421C3 (en) * | 1979-04-04 | 1982-04-29 | J.M. Voith Gmbh, 7920 Heidenheim | Method and device for stripping off excess coating material from a moving web |
| US4396648A (en) * | 1982-02-08 | 1983-08-02 | Consolidated Papers, Inc. | Paper coating apparatus and method |
| DE3446525A1 (en) * | 1984-01-07 | 1985-08-01 | Jagenberg AG, 4000 Düsseldorf | Apparatus for coating, with a controllable coating thickness, lengths of material running over a support roller |
| DE3420412C2 (en) * | 1984-06-01 | 1995-08-10 | Voith Gmbh J M | Coating device for coating running webs |
| US4804556A (en) * | 1984-08-30 | 1989-02-14 | E. I. Du Pont De Nemours And Company | Edge thickness control system |
| GB8508431D0 (en) * | 1985-04-01 | 1985-05-09 | English Clays Lovering Pochin | Paper coating apparatus |
| US4687137A (en) * | 1986-03-20 | 1987-08-18 | Nordson Corporation | Continuous/intermittent adhesive dispensing apparatus |
| FI82617C (en) * | 1987-04-09 | 1991-04-10 | Valmet Paper Machinery Inc | Controller for surface treatment device of material web |
| DE3817973A1 (en) * | 1987-06-10 | 1988-12-22 | Voith Gmbh J M | Smoothing device of an application mechanism |
| DE3729621A1 (en) * | 1987-09-04 | 1989-03-16 | Jagenberg Ag | DEVICE FOR COATING A MATERIAL RAIL THROUGH A COUNTER ROLLER |
| FI100311B (en) * | 1988-09-23 | 1997-11-14 | Voith Gmbh J M | Smoothing device for a coating machine |
| DE3908386A1 (en) * | 1989-03-15 | 1990-09-27 | Jagenberg Ag | METHOD AND DEVICE FOR COATING MATERIAL SHEETS, ESPECIALLY PAPER OR CARDBOARD SHEETS |
| DE4008435A1 (en) * | 1989-06-22 | 1991-01-03 | Voith Gmbh J M | PAINTING DEVICE |
-
1991
- 1991-02-08 FI FI910616A patent/FI91025C/en active
-
1992
- 1992-01-23 SE SE9200192A patent/SE509562C2/en not_active IP Right Cessation
- 1992-02-06 CA CA 2060769 patent/CA2060769C/en not_active Expired - Fee Related
- 1992-02-06 DE DE4203398A patent/DE4203398C2/en not_active Expired - Lifetime
- 1992-02-06 GB GB9202545A patent/GB2252926B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| FI91025B (en) | 1994-01-14 |
| SE9200192D0 (en) | 1992-01-23 |
| SE9200192L (en) | 1992-08-09 |
| FI91025C (en) | 1995-08-22 |
| GB2252926B (en) | 1994-09-21 |
| GB9202545D0 (en) | 1992-03-25 |
| SE509562C2 (en) | 1999-02-08 |
| DE4203398C2 (en) | 2003-01-09 |
| CA2060769A1 (en) | 1992-08-09 |
| FI910616A0 (en) | 1991-02-08 |
| DE4203398A1 (en) | 1992-08-13 |
| GB2252926A (en) | 1992-08-26 |
| FI910616A (en) | 1992-08-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |