Field

[0001] The invention relates to a method and equipment for control and manufacture of corrugated cardboard.

Background

[0002] Corrugated cardboard is widely used as packaging material in transport packages, consumer packages and wrappers, for instance. Corrugated cardboard includes at least one corrugated fluting layer and at least one straight liner. Often, one fluting is glued between two liners. In order to improve strength and resistance, corrugated cardboard may even be provided with a plurality of corrugated layers. The size used is usually starch size but, for humid conditions, wet-strength size may also be used.

[0003] It is important for the quality of corrugated cardboard that the sizing is strong and the surfaces of the cardboards are unwarped in shape. Drawbacks exist in the management of manufacture of corrugated cardboards, which impairs the quality of corrugated cardboards. Therefore, a need exists to improve the manufacture of corrugated cardboard.

Brief description

[0004] An object of the invention is to provide an improved solution for manufacture of corrugated cardboard. This is achieved by control equipment according to claim 1.

[0005] The invention also relates to manufacturing equipment according to claim 13.

[0006] The invention also relates to a control method according to claim 14.

[0007] The invention also relates to a manufacturing method according to claim 24. [0008] The invention also relates to a process controller according to claim 25.

[0009] Preferred embodiments of the invention are disclosed in the dependent claims.

[0010] The equipment and method according to the invention provide several advantages. In the manufacture of corrugated cardboard having one or more flutings and at least two liners, it is possible to control the surface moisture of the liners at processing and sizing steps of the liners and the at least one fluting, which reduces or eliminates warping of the finished corrugated cardboard.

List of figures

[0011] The invention is now described in closer detail in connection with the preferred embodiments and with reference to the accompanying drawings, in which

Figure 1 shows an example of equipment for manufacture of corrugated cardboard;

Figure 2 shows an example of equipment for manufacturing corrugated cardboard having one or more flutings and at least two liners;

Figure 3 shows an example of equipment for manufacture of single- faced corrugated cardboard;

Figures 4A and 4B illustrate behaviour of moisture in a liner;

Figure 5 shows an example of scanning measurement;

Figure 6 shows an example of in-line measurement,

Figure 7 shows an example of a processor and memory; and

Figure 8 shows an exemplary flow chart of a control method.

Description of embodiments

[0012] The following embodiments are presented by way of example. Even though the description may refer to "a", "one", or "some" embodiment or embodiments at different points, this does not necessarily mean that each such reference refers to the same embodiment or embodiments or that the feature only applies to one embodiment. Individual features of different embodiments may also be combined to make other embodiments possible.

[0013] Figure 1 shows an example of equipment for manufacture of corrugated cardboard; a start end of a process is provided with at least one splicer 10, wherein paper rolls 12 are spliced and forwarded towards fluting and sizing. The paper is usually about 2,5 m in width. In order to manufacture fluting, the paper is corrugated by a corrugator or singlelacer 14, which also glues the liner to the fluting. This is how single-faced corrugated cardboard is made. At a glue machine 16B, a second liner is glued to the fluting of the single-faced corrugated cardboard in order to form corrugated cardboard having one or more flutings and at least two liners. Next, the corrugated cardboard having one or more flutings and at least two liners is heated on a grate 18 for drying the glue. Multilayer corrugated cardboards may be manufactured in a similar manner. An emptying paper roll 12 may be replaced by a new paper roll 12, in which case an end of the exhausting paper may be glued to an end of the unfolding paper. Since a corrugated cardboard machine is used for manufacturing differently sized batches of different cardboards, a paper roll may be replaced every fifteen minutes, for instance. The manufacture of corrugated cardboard having one or more flutings and at least two liners necessitates paper from three rolls, which further makes paper roll replacement more frequent.

[0014] The fluting of corrugated cardboard may be provided with a plurality of different flute profiles. With the microwave G&N paper, the thickness or flute height of the corrugated cardboard is about 0.8 mm and the flute number is about 550 per metre. With the microwave F paper, the thickness of the corrugated cardboard is about 1.0 mm and the flute number is about 440 per metre. With the miniwave E paper, the thickness of the corrugated cardboard is about 1.5 mm and the flute number is about 300 per metre. With the fine flute B paper, the thickness of the corrugated cardboard is about 3 mm and the flute number is about 150 per metre. With the coarse flute C paper, the thickness of the corrugated cardboard is about 4 mm and the flute number is about 130 per metre. With the double-flute BC paper, the thickness of the corrugated cardboard is about 7 mm.

[0015] The fluting may be manufactured from primary fibre for instance in a semi-chemical process, and its basis weight may be 80 g/m2 to 200 g/m ² Recycled Fluting, RF, may on one hand also be partly or completely manufactured from recycled paper. Corrugated cardboard may use for instance three kinds of liners: kraftliner, euroliner and testliner. Kraftliners are mostly made from primary fibre and the kraftliners are suitable for food packages. The basis weight may be 60 g/m2 to 400 g/m2 or even more than 400 g/m2. Euroliners are made from recycled paper. Testliners are mainly made from recycled fibre. In connection with the manufacture of corrugated cardboard, instead of papers, terms such as boards, i.e. fluting and liner, may also be used.

[0016] The quality of the corrugated cardboard obtained as end product is affected by the qualities and characteristics of the papers used. Most often paper rolls are stored in outdoor storages where the temperature and of cardboard having one or more flutings and at least two liners vary constantly. Therefore, the moisture and temperature levels of papers on the rolls vary according to weather and, consequently, differ from the driving moisture on the paper machine. In addition, the moisture and temperature of the paper is also affected by whether the moisture and temperature of the paper are examined at the outermost circumferences, inner circumferences, edge or middle of the roll. In particular, when a roll is changed, cardboard having one or more flutings and at least two liners may be subjected to abrupt and great changes. Also the temperature may change drastically. Such changes in moisture cause warping or curling of papers and corrugated cardboards obtained as end products, which impedes the manufacture of corrugated cardboard and folding and assembly of the package from corrugated cardboard. Also temperature may affect warping of the corrugated cardboard in a similar manner.

[0017] Figures 2 and 3 show corrugated cardboard manufacturing equipment for manufacture of corrugated cardboard having one or more flutings and at least two liners. The equipment of Figure 2 relates to the glue ma- chine 16B. The control equipment for the manufacture of corrugated cardboard comprises a sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G and actuator equipment 104A, 104B, 104C, 106A, 106B acting on moisture. Further, the equipment for manufacture of corrugated cardboard may in an embodiment comprise a controller 130 and a user interface 132. The controller 130 may comprise at least one processor and one or more memories provided with a computer program code. The computer program code may by means of said at least processor and said at least one or more memories bring the equipment for control and/or manufacture of corrugated cardboard to operate in a desired manner.

[0018] The sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G measures surface moisture from at least one liner 1 4, 148.

[0019] On the basis of the measurement made by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D acting on moisture adjusts surface moisture of at least one liner 144, 148.

[0020] Figure 3 shows equipment for manufacturing a single-faced corrugated cardboard for manufacturing corrugated cardboard of Figure 2 with one or more flutings and at least two liners. The equipment of Figure 3 thus corresponds to the corrugator 14 of Figure 1. Unwound fluting 120 enters actuators 1 2A, 1 2B at which the fluting 120 is pretreated for fluting. Next, fluting rolls form a fluted fluting 120 and then the fluting 120 advances to the glue machine 16A at which glue is dispensed to flute peaks of the fluting 120 and the fluting 120 is glued to a liner 150.

[0021] The control equipment further comprises a sensor arrangement 202A, 202B, 202C, 202D and actuator equipment 204A, 204B, 206A, 206B acting on moisture.

[0022] On the basis of the measurement made by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may adjust surface moisture of the liner 44 glued to the fluting 120 from the opposite side of the fluting 120. [0023] Also the fluting 120 may be measured by means of one or more sensors 110. Correspondingly, the moisture and/or temperature of the fluting 120 may be adjusted by means of one or more actuators 112A, 112B. Such adjustments may be carried out after unwinding, prior to fluting and gluing.

[0024] In an embodiment, the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may adjust surface moisture of surface 154 of a liner 148, 150 not glued to the fluting 120, on the opposite side of surface 152, on the basis of the measurement made by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D.

[0025] In an embodiment, the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G may carry out the measurement at least at one of the following points in the process direction: between the unwinding part 10 of the liner 150 and the fluting 120, and the glue machine 16A of the fluting 120 and the liner 150; between the glue machine 16A of the fluting 20 and the liner 150, and the glue machine 16B of the liner 148 and the single-faced corrugated cardboard 140, 142; between the glue machine 16B of the liner 148 and the one-faced corrugated cardboard 140, 142 and the grate 16; between the grate 18 and the cutting section 20; and after the cutting section 20.

[0026] In an embodiment, the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may adjust moisture at least at one of the following locations in the process direction: between the unwinding part 10 of the liner 150 and the fluting 120, and the glue machine 16A of the fluting 120 and the liner 150; between the glue machine 16A of the fluting 120 and the liner 150, and the glue machine 16B of the single-faced corrugated cardboard 140, 142 and the liner 144; between the liner 144 and the single-faced corrugated cardboard 140, 142 and the glue machine 16B of the liner 144 and the grate 18.

[0027] In an embodiment, the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D acting on moisture may adjust the moisture of the second surface 154 of the liner 148, 150 between the glue machine 6A of the single-faced corrugated cardboard 140, 142 and the glue machine 16B of the liner 150 and the single-faced corrugated cardboard 140, 142, the second surface 154 of the liner 148, 150 being on the opposite side of the surface 152 to be glued.

[0028] In an embodiment, the control equipment comprises, in connection with the sensor equipment 102F, 102G, equipment for measuring warp or curl in a corrugated cardboard having one or more flutings and at least one liner in the process direction between the grate or the cut 20 or after the cut. Warp may be measured for example by an imaging device, such as a camera and laser. In that case the laser may form a known pattern on the liner 144, 148, 50 of the corrugated cardboard. When an image of the pattern is taken with an imaging device, the image may be compared with the known pattern and the comparison may then be used to determine warp in the corrugated cardboard. The actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may then on the basis of the measurement by the measuring equipment adjust surface moisture of at least one liner 144, 148, 150 of a corrugated cardboard having one or more flutings and at least two liners.

[0029] In an embodiment, the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may adjust surface moisture of at least one liner 144, 148, 150 of a corrugated cardboard having one or more flutings and at least two liners on the basis of an orientation profile available.

[0030] In an embodiment, the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may adjust surface moisture of at least one liner 144, 148, 150 of a corrugated cardboard having one or more flutings and at least two liners in a direction transverse to the machine direction.

[0031] In an embodiment, the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may receive orientation data from the paper machine that manufactured the liner 144, 148, 150. [0032] In an embodiment, the control equipment comprises equipment for measuring the orientation profile of the liner 144, 148, 150 in connection with unwinding 10, for example. However, the measuring equipment may be in the manufacturing equipment anywhere between the unwinding 10 and the glue machine 16B. In that case the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B acting on moisture may receive the orientation data from the orientation profile measuring equipment.

[0033] In an embodiment, the control equipment may control the unwinding direction of the liner 144, 148, 50 on the basis of the orientation profile.

[0034] In an embodiment, the control equipment may select for use at least two liners 144, 148, 150 of different orientation directions on the basis of the orientation profile.

[0035] The manufacturing equipment of a corrugated cardboard having one or more flutings and at least two liners may glue together the liner 148 subjected to adjustment by the actuator equipment 104A, 104B, 104C, 106A, 106B, 106C, 106D, 204A, 204B, 206A, 206B and the fluting 140, 142, which forms part of the single-faced corrugated cardboard, in the glue machine 16B.

[0036] In an embodiment, the sensor arrangement 102A, 102B, 102C, 02D, 02E, 102F, 102G, 202A, 202B, 202C, 202D carries out moisture measurement optically. In an embodiment, the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D measures the liner 144, 148, 150 at one or more wavelengths where water has a higher absorption than the wavelengths in the environment. In an embodiment, the absorption wavelength of water may be for instance about 1.4 μηι, 1.9 μιτι and/or 2.7 μιη. In an embodiment, the measurement of cardboard having one or more flutings and at least two liners is taken from the liner 144, 148, 150 as a reflection measurement. The penetration depth into the liner 144, 148, 150 of optical radiation from optical reflection measurement may correspond to part of the thickness of the liner 144, 148, 150, in which case the optical measurement may be used for measuring the surface moisture of the liner 144, 148, 150. The intensity and wavelength of optical radiation may be adjusted to the characteristics of the liner so as to enable successful surface moisture measurement. The adjustment may be based on theory, simulation or testing.

[0037] In an embodiment, moisture is measured as relative moisture with respect to cellulose or the basis weight of the liner 144, 148, 150. Hence, data on one or more flutings and at least two liners may be obtained for instance as a percentage figure relating to the corrugated cardboard having one or more flutings and at least two liners. In addition, the sensor arrangement 102A, 102B, 102C, 02D, 102E, 102F, 102G, 202A, 202B, 202C, 202D may be used for measuring the amount of cellulose in the liner 144, 148, 150, for instance.

[0038] In an embodiment, in addition to surface moisture, it is possible to measure the overall moisture of the liner 144, 148, 150. In an embodiment, such overall moisture measurement is performed on the liner 144, 148, 50 as diameter measurement.

[0039] In an embodiment, the measurement of cardboard having one or more flutings and at least two liners may be used to determine the distribution and/or gradient of the liner 144, 148, 150 in the thickness direction in the corrugated cardboard having one or more flutings and at least two liners. This determining of the distribution and/or gradient in cardboard having one or more flutings and at least two liners may be carried out by measuring surface moisture on both sides of the liner 144, 148, 150. The determination of the moisture distribution and/or gradient may be carried out by measuring the surface moisture on at least one side of the liner 144, 148, 150 and the total moisture of the liner 150.

[0040] In an embodiment, the actuator equipment is heating equipment 104A, 104B that may adjust the temperature of the liner 150 on the basis of measurement by the sensor arrangement 02A, 102B, 02C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D. The heating equipment 104A, 104B may heat the liner 150 on the side of at least one surface 152, 154 in order to equalize the moisture in the machine direction of the liner 150. If the moisture is high, it may be reduced by the heating equipment 104A, 104B. [0041] In addition, on an embodiment, the actuator equipment is moistening equipment 106A, 106B that may adjust the moisture of the liner 150 on the basis of the measurement by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D. The moistening equipment 106A, 106B may moisten the liner 150 on the side of at least one surface 152, 154 in order to equalize the moisture in the machine direction of the liner 150. If the moisture is low, it may be increased by the heating equipment 104A, 104B.

[0042] Similarly, the moisture of the fluting 120 may be adjusted using as for instance a steam box or another moistening device as the actuator 1 12A. For adjusting the temperature, in turn, a steam cylinder with an adjustable angle of contact or another heating device, for instance, may be used as the actuator 112B.

[0043] In an embodiment, the liner 148, 150 may be moistened by the moisture contained in the glue 224. In that case also the glue unit 16A and the glue machine 16B may serve as actuator equipment acting on the moisture of the liner 148, 150. The glue machine 16B comprises dosing rolls 220, 222 that transfer the glue 224 to the peaks of the fluting 120. When the glue machine 16A glues the liner 150 of the fluting 120, the glue 224 adheres to the liner 150 and moistures it on the contact surface. The same takes place in the glue machine 16B, where corrugated cardboard having at least one fluting and one liner is glued to fluting 148. In that case the glue on the peaks of the fluting 148 adheres to the liner 148 and moistures it on the contact surface. The moisture content, dry matter content and/or amount of the glue influence the moisture of the liner 148, 150 and thus also the warp of the corrugated cardboard.

[0044] In an embodiment, heating equipment 104A, 104B, 204A, 204B comprises at least one drying cylinder, as shown by the heating equipment of Figure 2. In such a case, the temperature of the liner 144, 148, 150 may be adjusted by changing the angle of contact of the drying cylinder on the basis of the measurement carried out by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D. The contact angle may be changed by moving a roll 200, whereby the area of the liner 144, 148, 150 against the drying cylinder increases or becomes larger (curved arrow next to the heating devices). The longer the contact angle, the more the drying cylinder heats the liner 144, 148, 150. The heat of the drying cylinder may be derived from hot steam contained in the drying cylinder.

[0045] In an embodiment, the heating equipment 104A, 104B, 204A, 204B comprises an infrared heater (not shown in the figures) which adjusts its heating power on the basis of the measurement by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D.

[0046] In an embodiment, the heating equipment 104A, 104B, 204A, 204B comprises an induction heater (not shown in the figures) which adjusts its heating power on the basis of the measurement by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D.

[0047] In an embodiment, said moistening equipment 106A, 106B, 106C, 206A, 206B comprises a steam box (not shown in the figures) which adjusts the amount of steam it applies to the liner 144, 148, 150. In an embodiment, the steam box adjusts the temperature of steam it directs to the liner 144, 148, 150. When a steam box is used, energy-optimization may be achieved.

[0048] In an embodiment, the moistening equipment 106A, 106B, 106C, 206A, 206B comprises a set of water nozzles (not shown in the figures) which adjusts the amount of water spray it directs to the liner 144, 148, 150. In an embodiment, the set of water nozzles comprises a water temperature adjustment part (not shown in the figures) which adjusts the temperature of water spray directed to the liner 144, 148, 150.

[0049] In an embodiment, the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D may also measure temperature from the liner 144, 148, 150. In such a case, the heating equipment 104A, 104B, 204A, 204B may adjust the temperature of the liner 144, 148, 150 on the basis of the surface moisture measurement and the tempera- ture. Correspondingly, the moistening equipment 106A, 106B, 106C, 206A, 206B may adjust the moisture of the liner 144, 148, 150 on the basis of the surface moisture measurement and the temperature.

[0050] Figure 4A shows a change in moisture and temperature as a function of time when three different paper rolls 12 change in the manufacture of corrugated cardboard. Moisture is shown as percentages, and time as hours and minutes. Temperature is shown in degrees Celsius, and time as hours and minutes on the same scale as moisture, because temperature and moisture were measured simultaneously. Graph 300 shows the moisture of an unwound paper roll. Graph 302 shows the surface moisture of the liner 150 on a first surface 152 to be glued to the fluting 120. Graph 304 shows the surface moisture of the liner 150 on a second surface 154, which may be the glueless outer surface of the corrugated cardboard.

[0051] Graph 306 shows the temperature of an unwound paper roll. Graph 308 shows the surface temperature of the liner 150 on the first surface 152 to be glued to the fluting 120. Graph 310 shows the surface moisture of the liner 150 on the second surface 154, which may be the glueless outer surface of the corrugated cardboard. The graphs show that when the paper roll changes from roll 1 to roll 2, the temperature rises temporarily to some extent, whereas when changing from roll 2 to roll 3, the temperature decreases slightly. If the moisture of the liner 150 were adjusted on the basis of temperature alone, the heating of the liner 150 would be reduced due to a rise in the temperature. This adjustment would, however, go in the wrong direction because according to the moisture measurement the liner 150 from roll 2 is much moister than the liner 150 from roll 1. Therefore, even though the temperature of the liner 150 increases as the roll is changed, the liner 150 must in fact be heated more in order to remedy the surface moisture and/or the total moisture. Correspondingly, when transferring from roll 2 to roll 3, on the basis of temperature, heating would be increased even though according to the surface moisture measurement heating should be reduced. Figure 4A also shows that moisture measurements on the different surfaces 152, 154 of the liner 150 may reveal a difference in the moisture of the surfaces, which is indicative of moisture distribution in the thickness direction of the liner. By means of the moisture distribution and/or moisture gradient, the moisture on the different surfaces of the liner 150 and/or the total moisture may be adjusted, whereby gluing is easier to perform.

[0052] Changes in temperature and surface moisture also take place within one paper roll. In such a case, too, the surface moisture of the liner 150 may be changed by means of surface moisture measurement. This is also true for the liner 144 on the surface of a single-faced corrugated cardboard.

[0053] On the basis of Figure 4A, it can be concluded that the conditioning of the liner temperature is not essential from the point of view as far of adjusting the surface moisture, but the temperature variations may be allowed. Then, the total moisture and/or surface moisture of the liner 150 may be adjusted more efficiently.

[0054] Figure 4B shows the measured moisture M of the liner 150 as a function of time T on a freely-chosen scale, and the operating power P of the actuator as a function of time T on a freely-chosen scale. Moisture M may refer to the surface moisture of the liner 50 on the first surface 152 to be glued to the fluting 120._The measurement may have been carried out by a sensor arrangement 102A, 102B, 102C, 102D. In this case, the measurement may be thought as having been carried out by the sensor arrangement 102B or 102C. In the case of graph 300, the liner 150 is not moistened or heated. In the case of graph 302, the liner is moistened and heated. The moisture of the liner 150 is quite uniform at first. At TO, the liner roll change takes place, and the moisture of the liner on the second roll is notably higher, at first in particular, than that of the liner on the previous roll. After a while, the moisture of the second liner becomes even but remains slightly different in this example from the moisture of the first roll. At T1 , a new liner change takes place. Here, the moisture of the third liner is at first notably lower than that of the second liner. In this case, too, the moisture becomes even after a while.

[0055] Graph 302 shows a corresponding moisture measurement but now the heater 104A, 104B is switched on or its power is increased at TO as per graph 304. The increase in the heating power may also take place just before TO when the change in moisture is just about to arrive at the gluing unit 100, or slightly after TO when the change in moisture is still great and affects the manufacture of corrugated cardboard. The heating power may be increased and decreased during the change in the heating power. As shown by graph 302, even though the change in moisture in the case of graph 302 is not quite as big as in the case of graph 300, the duration of the moisture change may be shortened by heating. Correspondingly, if heating is started even before a change in moisture, the intensity of the moisture change may be decreased. On the other hand, it is also possible to intensify the increase in moisture and/or extend the duration of the moisture change by a reduction in heating.

[0056] In the case according to graph 302, at T1 the moistening of the liner may be increased according to graph 306, whereby the change in the moisture of the third liner is of shoter duration than in the unmoistened case according to graph 300. Moistening may be increased and decreased step-by- step in the same way as heating. The increase in moistening may be take place just before T1 _r when the moisture change is just about to arrive at the gluing unit 100, or after T1 , when the moisture change in the liner is still great and affects the manufacture of corrugated cardboard. Variations in moisture and temperature and problems associated with the prior art control are also true for a liner 144 on a single-faced corrugated cardboard.

[0057] In an embodiment, the surface moisture of the liner 144, 148, 150 may be measured by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D not only in the machine direction but also in the transverse direction . In such a case, the surface moisture of each transverse point or sector of the liner 144, 148, 150 may be separately measured and adjusted. In an embodiment, shown in Figure 5, the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D may sweep across the liner 144, 148, 150. In an embodiment, shown in Figure 6, the sensor arrangement 102A, 02B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D comprises a row of sensors 500, which is aligned across the liner 144, 148, 150 in the transverse direction. This enables moisture and/or temperature to be measured.

[0058] In an embodiment the moisture of the liner 150 may also be adjusted by the moistening arrangement 106A, 106B, 106C, 206A, 206B not only in to the machine direction but also in the transverse direction. Often, the penetration of glue is poorer at the edges of the liner 144, 148, 50 than in the middle. In that case, the surface moisture at the edges of the liner 144, 148 150 may be increased by moistening and/or heating. In an embodiment, the moistening equipment 106A, 06B, 06C, 206A, 206B may sweep over the liner 144, 148, 150 in the same way as the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D in Figure 5. In an embodiment, the moistening equipment 106A, 106B comprises a row of water nozzles of a set of water nozzles in the same way as the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D in Figure 6, which extends across the liner 144, 148, 150 in the transverse direction. With the nozzles of the set of water nozzles water can be directed towards the liner 144, 148, 150 with precision. The inaccuracy in the targeting of the water may be as little as less than a millimetre. It is often possible to target the water at an inaccuracy of millimetres. The moisture of the liner 144, 148, 150 may thus be adjusted on the basis of the targeting inaccuracy in the transverse direction. Moreover, the amount of the water to be targeted may be dimensioned rapidly and with precision by the set of water nozzles, which enables even minor moisture differences to be adjusted and controlled both in the machine direction and in the direction transverse to the machine direction. The inaccuracy in the water amount dispensed may be millilitres, or less, which enables a low standard deviation in the liner moisture to be maintained. The amount of the water dispensed may be changed in less than one second.

[0059] In an embodiment the surface moisture of the liner 144, 148, 150 may be adjusted by the heaters 104A, 104B, 104C, 104D, 204A, 204B not only in the machine direction but also in the transverse direction. In an embodiment, the heating equipment 104A, 104B, 104C, 104D, 204A, 204B may sweep over the liner 150 in the same way as the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D in Figure 5. In an embodiment, the heating equipment 104A, 104B, 104C, 104D, 204A, 204B comprises a row of sensors in the same way as the sensor arrangement 102A, 102B, 102C, 102D in Figure 6, which extends across the liner 144, 148, 150 in the transverse direction.

[0060] In an embodiment, the surface temperature of the liner 144, 148, 150 may be adjusted by the heating equipment 104A, 104B, 104C, 104D, 204A, 204B not only in the machine direction but also in the transverse direction. In such a case, heating is directed on the liner 144, 148, 150 in a zone-by- zone manner by line-form heating in the same way as the measurements by the sensor arrangement in Figure 5.

[0061] Figure 7 shows an example of a controller 130. The controller 130 may comprise at least one processor 600 and at least one memory 602 containing a computer program code. Said at least one memory 602 together with said at least one processor and computer program code causes the controller 130 to receive the surface moisture of the liner 150, measured by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D, and to control actuator equipment 104A, 104B, 104C, 106A, 106B, 204A, 204B, 206A, 206B to adjust the moisture of the liner 150.

[0062] Figure 8 is a flow chart of an adjustment method. At step 800, the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D measures surface moisture of at least one liner 144, 148, 150. At step 802, surface moisture of at least one liner 144,1 48, 150 is adjusted by the actuator equipment 104A, 104B, 104C, 106A, 106B, 204A, 204B, 206A, 206B acting on moisture on the basis of a measurement by the sensor arrangement 102A, 102B, 102C, 102D, 102E, 102F, 102G, 202A, 202B, 202C, 202D.

[0063] The method shown in Figure 8 may be implemented as a logic circuit solution or computer program. The computer program may be placed on a computer program distribution means for the distribution thereof. The computer program distribution means is readable with a data processing device, and it may encode the computer program commands to control the operation of the measuring device.

[0064] The distribution means, in turn, may be a solution known per se for distributing a computer program, for instance a data processor-readable medium, a program storage medium, a data processor-readable memory, a data processor-readable software distribution package, or a data processor- readable compressed software package. In some cases, the distribution medium may also be a data processor-readable signal, or a data processor- readable telecommunications signal.

[0065] Even though the invention has been described above with reference to the examples according to the attached drawings, it is clear that the invention is not restricted thereto but may be modified in many ways within the scope of the accompanying claims.