FI118813B - Profiles controlling method for profiled roll gap of calendar i.e. multi-roll calendar, involves copying values of last profile of reference profiled roll gaps on to last profile of other profiled roll gaps at small measures - Google Patents

Abstract

The method involves measuring a profile of a web to be calendered by a measuring device, which is positioned in a running direction of the web behind a profiled roll gap (N2). A profiled roll gap (N1) and the roll gap (N2) are controlled with a separably rapid control, and the gaps are selected as reference profiled roll gaps. Values of a last profile of the reference profiled roll gaps are copied on to a last profile of other profiled roll gaps at small measures.

Description

118813

Calendar profile adjustment Profilreglering i en kalander

5 TECHNICAL FIELD

The invention relates to a method according to the preamble of claim 1. BACKGROUND OF THE INVENTION

10

Calendering generally aims to improve the properties such as smoothness and glossiness of a web material such as paper or board. In calendering, the web is guided into a nip formed between rolls to be pressed against each other, i.e. a calendering nip, in which the web is deformed by the effect of temperature, humidity and nip pressure. In the calender, the nips are formed between a smooth-faced press roll, such as a metal roll, and a roll coated with a flexible coating, such as a polymer roll. The flexible surface roll conforms to the surface contours of the web and presses the web evenly against the smooth opposing surface of press rolls.

The multi roll roll calender consists of at least two rolls with a nipple between them. The multi-roll calender can consist of a single roll stack, whereby nipples are always formed between two pairs of rolls. The multi-roll calender may also include a plurality of parallel roll stacks M · · · * · ... The roll stack may be vertical or it may: * * *: form an angle with the vertical.

Thus, a multi-roll calender can consist of one or more roll stacks with upper and lower rolls and intermediate rolls. The upper roller and the lower roller are then deflection compensated rolls, in which case the web profile can be adjusted between the upper roller and the upper intermediate roller. in the profiling nip and in the profiling nip between the lower roller and the lower intermediate roll.

··· |; t 30 In the nip between nip rolls, the web profile cannot be directly adjusted, but the upper and *. · * ·· _ lower roll profile shapes are transmitted to the nip between nip rolls.

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The multi-roll calender may also consist of discrete nipples such that each roll stack comprises only two rolls between which a calendering nip is formed. The deflections of the nip rolls can be compensated by the deflection compression-5 ringers on the upper or lower rolls so that the profile nipples take a straight line shape.

In both of the above cases, each profiling nip has its own profile adjustment, but the measurement profile comes from a common measuring device, i.e. a measuring frame, located after the last profiling nip. Thus, the measuring frame measures only the interaction of the profiling nipples 10 with the web profile. The individual effect of each profiling nip on the web profile cannot be determined by such an arrangement.

The problem with this kind of imitation is that the profile increments of the profile nipples drift to extremes. The web profile may be good, but the adjustments have compensated for each other's errors with opposing profiles, so that the adjustments in the extreme position are no longer able to respond to changes. Depending on the speed of the adjusters, this phenomenon occurs within a few hours or sometimes even less than an hour.

One reason that the profiling nips and their associated adjusters do not remain completely unknowingly is that the adjusters generally do not operate completely freely, but instead receive feedback information from the profiling roller. Once the controller has calculated • · •: * · the new setpoints for the deflection roller loading members, they are fed into a so-called "roll".

··· t to the optimization calculation, which results in the actual load pressure and the roll pressures implementing it. The actual load profile may not be exactly the same in the various profile nipples. The adjustment is implemented using the previous profile as the starting point for the next adjustment calculation. This is one reason why two separate controls react slightly different ··. to changes in the web. Various adjustments to be optimized also take into account ····: 1 · the widths of the load cell zones and thus influence the · · · · 30 output of the adjustment.

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It is also possible to make adjustments so that the adjuster does not have any feedback field from the roll optimization calculation. In this case, two unregulated controllers may remain in sync for a longer period of time, but at some point the control outputs will drift to different situations due to inaccuracies in, for example, calculation and the like.

The above problem is clearly exacerbated if the number of loading members of the different profiling nipples is not the same. In this case, the measurement signal has to be divided into a number of calculation points, which results in different filtering. The largest peaks of the measurement signal distributed to the wide counting point 10 disappear.

This problem has been solved in the prior art e.g. by adjusting the adjustments of the profile nipples following the first profile nip so slow that they do not drift in any direction due to profile malfunctions. If it is only desired to drive the slower adjustment with the profile nipples then the adjustment is too slow. When driving with all profiling nipples, the profiling power of the slow profiling nips will not be used.

Another prior art solution is to always use the same load profile in each profile nipple when the profile nipples are driven automatically. If the profile nipples following the first profiling nip are driven by manual adjustment and are switched to automatic adjustment, the profiles of these profiling nipples immediately change to the same as in the first profiling nip. : This rapid change of the profiles of the profiling nips following the first profiling nip also results in a rapid change in the profile of the web.

• · • · «· · * i ·

The third prior art solution is to run the first profiling ···. Profiling nipples following tinip with manual adjustment only. In this case, the profiled nips with manual adjustment ·· «·: *** must be continuously adjusted to match the load profile of the auto-adjusting ♦ · # li 30 profile nip.

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SUMMARY OF THE INVENTION

The main features of the method according to the invention are set forth in the characterizing part of claim 1.

5

In the solution according to the invention, a fast separate adjustment for each profile nip is followed and one profile nip is selected as the so-called reference profile nip. The value of the load profile of this reference profile nip is copied in small steps over the load profiles of the other profile nip. Preferably, the reference profile-10 warp nip is the first profiling nip in the calender web passage because it has the greatest effect on the web profile.

In the solution of the invention, the effect of the small step copy function on the load profile of the other profiling nipples is at least three times stronger compared to the effect of separate rapid adjustments of said other profiling nips on the load profile.

The copy function prevents the profile nipples from drifting into opposing ptophiles as it overrides the factors that drive the profiles in different directions. Essential • · *: 20 list is that copying can allow different profiles temporarily eg.

• · initial situations, malfunctions, and driver changes for whatever reason.

The solution according to the invention is suitable for adjusting the thickness profile of the web.

• aa • · · · ·· ·

25 BRIEF DESCRIPTION OF THE FIGURES

• · • ·

• M

• * ·!. "! Figure 1 shows the load profiles of the calender profiling ... nipper with two profiled nipples in a prior art solution when the first ·· «·; * '* The profile nip has a slow adjustment and the other profile nip has a quick adjustment.

• · · 30 • M «· · · · · · · · · · · · · ··· 5 118813

Fig. 2 shows the load profiles of the calender profiler nipples with two profiling nips in a prior art solution where both profiling nips have the same load profiles.

Figure 3 shows the load profiles of the calender profiler nipples with two profiling nips in the solution according to the invention when the profiling nips have different load profiles.

Fig. 4 shows the load profiles of the caliper piofiloin-10 tin nipples in a prior art solution with different load profiles.

Fig. 5 is a plan view of a calender with two separate profile nipples in which the solution of the invention can be used.

15

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 shows the load profiles of the calender profiling nipples with two profiling nips in a prior art solution with the first profiling nip N1 having a slow adjustment and the second profiling nip N2 having a fast adjustment. The quick adjustment of the second profiling nip N2 in step 1) responds quickly to the malfunction in the main web, but the slow adjustment of the first profiling nip N1 does not respond to this malfunction in the paper web.

··· • t • · ··· Figure 2 shows a profile of a calender with two profiling nips; load profiles of tinipips in the prior art solution when both ί,., ί profile nipples have the same load profiles. Section 2) describes the situation where .t. another profile nip N2 is with manual adjustment. With this other profiling nipple · «·· · 1. The load profile ··· \ 30 of the second profiling nip N2 is switched back on for automatic adjustment suddenly to the same as the first profiling nip N1, which causes a disturbance in the paper profile. In such a situation, the second profile nip N2 should continue from the value obtained by manual adjustment.

Figure 3 shows the load profiles of the calender profiler-5 tines of the calender with two profiling nipples in the solution of the invention when the profiling nipples N1, N2 have different load profiles. This different load profile of the profiling nipples N1, N2 may be due e.g. to the fact that the second profiling nip N2 has a valve failure at 3) or that the driver at 4) for some other reason wanted to manually load the second profiling nip N2 with a different load profile 10. When the valve defect of the second profiling nip N2 is repaired or when the adjustment of the second profiling nip N2 is changed to automatic adjustment, the adjustment of the second profiling nip N2 continues from its current value and slowly begins to approach the load profile of the first profiling nip N1.

15

Figure 4 shows the load profiles of the calender profiling nipples with two profiling nips in the prior art solution when the profiling nips have different load profiles. Since there is no copy function here, the profile lointx nips N1, N2 remain driven by the profiles shown in the figure, that is, they have drifted to • · * 20 opposite profiles in steps 5) and 6).

Figure 5 shows a schematic view of a calender with two separate profiled nipples in which the solution of the invention can be used. ** **. the hinge has two successive, separate profiling nips N1, N2. The first profiling nip N1 is formed between the first deflection roll 11 and the first thermal roll 12, and the second profiling nip N2 is formed by the second or

a rubber-controlled roll 21 and a second thermal roll 22. Calenderable web W

♦ ··

passes through the profiling nipples N1, N2 and after the second profiling nip N2, the web W

····. ···. is led to a measuring device, i.e. a measuring frame 30, by which the properties of the web W are anything. The measurement signals of the gauge frame 30 are applied to a control unit 40 for controlling the deflection compensated rollers 11,21 of the profiling nips N1, N2. When the profiling pins N1, N2 are closed after a web break, each profiling nip N1, N2 continues to drive with the load profile it had just before the web break. The driver can also select another load profile if, for example, the paper quality to be driven changes. In this case, the same load profile is set as a starting profile in each of the profiling nips N1, N2.

The use of the invention is not bound to the calendar shown in Fig. 5, but can be used in all calendars having at least two profiling nips. The invention can thus also be applied, for example, to a calendar having three or more separate calendering nips with profiling capability. The invention can also be applied to a calendar having one or more roll stacks, each roll stack comprising a top roll, a lower roll, and intermediate rolls. The upper roll and lower roll are then deflected, whereby a profiling nip is formed between the upper roll and the upper intermediate roll and between the lower roll and the lower intermediate roll. The roll stacks may be vertical-15 or they may form an angle with the vertical. The line drawn through the centers of the roll stack rolls can form a straight line or a broken line.

Only some preferred embodiments of the invention have been described above, and it will be apparent to those skilled in the art that they may be subject to numerous modifications within the scope of the appended claims.

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Claims (4)

1. A method for registering the profiles of profiling nip (N1, N2) in a calender consisting of at least two profiling nip (N1, N2) comprising the following steps: 5. for each profiling nip (N1, N2) a load profile is formed, - the profile of a web (W) calendered is measured with a measuring device (30) located after the last profiling nip (N2) in the calender in the direction of travel of the web (W) being calendered, characterized in that the method further comprises the following steps: 10. each profiling nip ( N1, N2) are regulated with each quick controller, - a profile nip (N1, N2) is selected for a reference profiling nip, - the value of the load profile in the reference profiling nip (N1, N2) is copied with small steps on the load profile in at least one other profiling nip ( . 15 2. A method according to claim 1, characterized in that the effect of the small step function for copying the load profile in the reference profiling nip (N1, N2) on the load profile in said at least one other profiling nip (N1, N2) is at least three times more powerful. than the effect of the different rapid control of the load profile in said at least one other profiling nip (N1, N2). • · • · • a • · · • aa. ·. Method according to Claim 1 or 2, characterized in that the first pro fi lm (N1, N2) in the calender in the direction of travel of the web (W) calendered is selected. reference profiling nip (N1, N2). 25 • · • · · Method according to any of claims 1-3, characterized in that the thickness profile of the web is controlled. A · a · a · a · a · a · a · a · a · · · · · · · · · · · · · · · · · · · · · · · ·