EP1209286A2 - Calender and process for treating a web - Google Patents

Abstract

A calender has a bunched array of rollers with two end-rollers and a number of intermediate rollers. In operation two neighbouring rollers, each of which sags slightly, form a nip. The sag of adjacent rollers (i, i + 1) differs. especially the second roller facing the concave surface of the first roller, has less sag than the first. Also claimed is a process to treat a material web passing through several nips where it is subjected to pressure and each nip is formed by a first and second roller. The sag in each roller has a bending amplitude on the convex side of the first roller which is essentially identical to the bending amplitude on the concave side of the second roller. Each roller has a set of support bearings left and right. The distance MbML between the bearings on one roller is 0.1 to 2 per cent different to the distance MbML in the second roller bearing, with reference to the longer of the two dimensions. At least one of the intermediate bearings has a variable bearing distance MbML.

Description

The invention relates to a calender with a roll stack, of the two end rolls and in between several intermediate rolls has, in operation two each other neighboring rolls, each with a deflection, to form a nip. The invention further relates to a method for treating a material web, the passed through several nips and pressurized there with each nip through a first roller and one of these adjacent second rollers is formed becomes.

Such a calender is used, for example, to satinize a paper web. Here you want over the entire width of the paper web achieve even pressure distribution in order to thickness and Quality differences across the direction of the paper web to avoid. The paper webs to be satinized currently have widths of up to 10 m. The correspondingly long rollers therefore tend because of their own weight in the axial center "sag", so they have a deflection. Even if this deflection is not too big, makes them annoying in the pressure treatment of the paper web or another material web noticeable.

An attempt has been made to counteract this phenomenon. For example, it is known from EP 0 679 204 B1 select the intermediate rolls so that they all have the same inherent deflection, and the weight the rollers and the so-called overhanging loads, i.e. the parts connected to the rollers, such as Guide rollers or bearing housings, completely by weight relieve.

Another approach described in DE 198 20 089 A1 assumes that you have the line load profiles by introducing deformation forces on the roll neck the intermediate roller changed. You choose the Deformation forces such that the intermediate rolls for Exercising stress or relief pressures is essentially one get the same deflection, with a Degree of deflection according to a determinable change a roller-related line load difference between the upper and lower nip is set. The deflection-controllable rolls at the ends of the roll stack are then adapted to this bend. you can now observe that despite these same deflections the satin results are sometimes unsatisfactory are.

The invention has for its object the burden to be made uniform in the nip.

This task is performed on a calender of the type mentioned at the beginning Art solved in that the deflections distinguish adjacent rolls from each other, whereby one adjacent to the convex side of a first roller second roll a weaker deflection than the first Has roller.

This leaves the previous approach, to impart the same deflection to all rollers or to select the rollers so that they are of their own accord have the same deflection. But you open up the possibility that the deflection in the nips is stronger can be brought closer together than before. Here the consideration plays a role that one with the Deflection of a roller has not been the different Has considered effects that are on the concave and result on the convex side. If you now choose the deflections differently, then you can take these effects into account.

It is particularly preferred that adjacent rollers each have a deflection in which one Amplitude of the deflection of the surface line on the convex Side of the first roller essentially with one Amplitude of the deflection of the surface line of the neighboring matches the second roller on the concave side. So you can see the deflections of the two Rollers that form the nip under consideration in the nip adjust so that the pressure curve in the nip over the Width of the material web becomes much more uniform. The adjustment takes place where it is required is. You can easily accept that the deflections of the two rollers per se, i.e. the Deflection on the axes, differ from each other. A such a deviation is even a prerequisite that one the deflections at the two surface lines with each other matches.

Preferably points from adjacent rollers at least one force application device. You no longer have to choose rollers, the inherently required deflections exhibit. One can do such a deflection also by introducing external forces.

AB =

Arbeitsbreite

MbML =

Lagerabstand

D_(i) =

Durchmesser der ersten Walze

D_(i+1) =

Durchmesser der zweiten Walze

i =

Index der ersten Walze

i+1 =

Index der zweiten Walze.

Preferably, the amplitude depends f _{EM (i +1)} of the deflection of the second roll according to the relationship of the amplitude f _{EM ( i )} the deflection of the first roller f EM ( i +1) = 2 D ( i +1) k 2 + 4 D ( i +1) k 2 • f EU ( i ) - 2 D ( i +1) k 2 in which f EU ( i ) = f EM ( i ) - 1 4 K 2 • f 2 EM ( i ) • D ( i ) K = 16 FROM • 1 + 3 MbML - AB FROM 5 + 12 MbML - AB FROM

AB =

working width

MbML =

bearing distance

D _(i) =

Diameter of the first roller

D _{(i + 1)} =

Second roller diameter

i =

First roller index

i + 1 =

Second roller index.

Adjacent rollers preferably have different ones Stock clearances if they are in at least one parameter differ from each other. Achieved with this configuration not just a match of the deflections, more precisely the amplitudes of the deflections on the two neighboring generatrices of the two the nip forming rollers, but you have the option also set the same bending lines. The bending lines are known not only to depend on the Amplitude of deflection, but also for example from the curve shape of the bending line, which over the shear deformation for example, the degree of slenderness of the rollers depends. If you now have the option of bearing distances to vary the intermediate rolls, then you get the possibility of actually the curve shape of the Bending lines of the surface lines, i.e. of the two the nip better aligning the bounding lines.

The difference in the bearing distances is preferably in Range from 0.1% to 2% based on the larger bearing distance. Such a deviation is perfectly tolerable. There are major changes to the stool not required because of the forces on the stool act, no significantly different force application points receive. Still, with these little ones Changes already bring considerable benefits.

It is particularly preferred that the bearing distance at least one intermediate roller is changeable. To the exchange of the roller in question can then, if necessary the bending line into the desired shape bring.

It is preferred that the storage of all rollers symmetrical to the axial center. this is also valid for the intermediate roller, whose bearing distance is adjusted becomes. Although this means that the adjustment of the Make bearings at both axial ends. The bend the surface line of this roller is then over the entire working width at the bend of the corresponding adjusted second roller.

The task is in a method of the aforementioned Kind of solved in that the deflections of the two rollers chooses differently.

As explained above in connection with the calender, it is with different deflections of the rollers, i.e. their center lines, possible, the deflections the crucial points, namely those that form the nip Align surface lines with each other. To this The satin finish is spread across the working width, i.e. the width of the material web, drastically improved.

It is preferred that the deflection of the first The roller controls the amplitude of the deflection the generatrix on the convex side of the first The roller corresponds to the amplitude of the deflection the surface line on the concave side of the second roller. If you match the deflections brings, you get an improved across the width of the rollers Work product.

It is also an advantage if you have unequal rollers the bearing distance of a roller compared to the bearing distance the other roller sets differently. As stated above not only the amplitude can be determined in this way the deflection in accordance with the two surface lines bring, but also the curve shape of the Bending line.

Fig. 1

eine erste Prinzipskizze zur Erläuterung wichtiger Größen,

Fig. 2

eine zweite Prinzipskizze zur Erläuterung weiterer Größen und

Fig. 3

eine schematische Darstellung von Biegelinien.

The invention is described below with reference to preferred embodiments in conjunction with the drawing. Show here:

Fig. 1

a first sketch to explain important parameters,

Fig. 2

a second schematic diagram to explain other sizes and

Fig. 3

a schematic representation of bending lines.

Fig. 1 shows a section of a roll stack of a calender. A first roller i and is shown a second roller i + 1, which has a nip N between them form. Through this Nip N, a material web is for example, one not shown Paper web, guided and there with pressure and if necessary also acted on at elevated temperature. It is desirable that the treatment over the total width of the nip N (i.e. the extension in axial direction of the two rollers i, i + 1) evenly he follows. A prerequisite for this is that the two Rollers i, i + 1 can also form the Nip N evenly.

In order to achieve such uniform training, the two rollers i, i + 1 have different deflections on. The deflections after a certain approach chosen below to be explained. The goal is the deflection to match the lower surface line of the upper roller i the deflection of the upper surface line of the lower Roller i + 1. For simplification, it is assumed that that the deflection only by the Gravity and the associated weight forces caused by the rollers. The considerations apply but basically also when the deflection is caused by external forces or moments.

The starting point for the following consideration is the opened roll stack, i.e. the middle rolls i, i + 1 hanging, supported in their bearings, freely accordingly their own bending lines made of gravity and rigidity by. This results at least in the first approximation the shape of a parabola. For the following consideration but it is enough if you have the deflection line as a circular line.

For the closing process of the nips, it is ideal to see when the lines of contact to be moved towards each other one of the two rolls forming the Nip N. have the best possible shape. The two Lines of contact are the lower surface line of the upper Roller and the upper surface line of the lower roller. Here you are largely independent of whether in the following Operating case the roller weight partially or be fully compensated.

The requirement that the lower surface line of the roller i in its deflection amplitude f _{EU i} the deflection amplitude f _{EO ( i +1)} corresponds to the upper surface line of the roller i + 1 underneath, cannot be fulfilled with exactly the same inherent deflections f _{EM of} adjacent center rollers i and i + 1, as can be derived from the sketch in FIG. 1.

gleich der Distanz XM der Walzen in der Walzenmitte

d.h. die Walzenspaltdifferenz Δf = XR-XM ergibt sich zu

Because of the same bending lines, the distance XR of the rollers is at the edges of the bales

equal to the distance XM of the rolls in the middle of the roll

ie the roll gap difference Δf = XR-XM results in

daraus folgt: tan α = 16 AB • 1 + 3 MbML - AB AB 5 + 12 MbML - AB AB •fEM = K •fEM Weiter gilt: 1cosα = 1+tan2 α Da tan²α im Vergleich zu 1 immer sehr klein sein wird, gilt als zulässige Vereinfachung: 1+tan2 α= 1 + 12 tan2 α Damit wird

According to known formulas, there is a fixed relationship between the deflection f _EM and the angle of inclination α of the self-bending line at the edge of the bale (if the shear deformation is neglected)

it follows: tan α = 16 FROM • 1 + 3 MbML - AB FROM 5 + 12 MbML - AB FROM • f EM = K • f EM The following also applies: 1 cos = 1 + tan 2 α Since tan ² α will always be very small compared to 1, the following simplification applies: 1 + tan 2 α = 1 + 1 2 tan 2 α So that will

In order to obtain the ideal conformity, ie Δf = 0, the deflection f _{EM of} the roller i + 1 must be smaller than that of the roller i above it. If the amplitude of the deflection of the lower surface line of the upper roller i with f _{EU i} and the amplitude of the deflection of the upper surface line of the lower roller i + 1 with f _{EO ( i +1)} is designated, then should apply f EU i = f EO ( i +1)

The sizes f _{EU i} and f _{EO ( i +1)} can be derived from the following relationships f EU i = f EM i - 1 4 K 2 • f EM i 2 • D i f EO ( i +1) = f EM ( i +1) - 1 4 K 2 • f EM ( i +1) 2 • D ( i +1) it follows: f EM ( i +1) = f EU i - 1 4 K 2 • f EM ( i +1) 2 • D ( i +1)

If you use this expression after f _{EM ( i +1)} dissolves, you get f EM ( i +1) = 2 D ( i +1) • K 2 + 4 D ( i +1) • K 2 • f EU i - 2 D ( i +1) • K 2 where f _{EU i} has been defined above.

AB = 10.000 mm

MbML = 11.700 mm Walzenposition Nenn-Ø D f_EM/mm f_EU/mm Δf_EM/mm zu Walze 2 2 760 2,37000 2,36987 0 3 825 2,36974 2,36960 0,00026 4 760 2,36948 2,36935 0,00052 5 825 2,36921 2,36908 0,00079 6 825 2,36894 2,36880 0,00106 7 760 2,36868 2,36855 0,00132 8 825 2,36842 2,36828 0,00158 9 760 2,36816 2,36803 0,00184 10 825 2,36789 2,36776 0,00211 11 760 2,36763 ---- 0,00237

This means that if you start with the top middle roll of a calender (i = 2), you can calculate the entire roll stack in terms of its ideally differing inherent deflections. This is set out in the following table, whereby the following applies:

AB = 10,000 mm

MbML = 11,700 mm roll position Nominal Ø D f _{EM / mm} f _{EU / mm} Δf _{EM / mm} to roll 2 2 760 2.37000 2.36987 0 3 825 2.36974 2.36960 0.00026 4 760 2.36948 2.36935 0.00052 5 825 2.36921 2.36908 0.00079 6 825 2.36894 2.36880 0.00106 7 760 2.36868 2.36855 0.00132 8th 825 2.36842 2.36828 0.00158 9 760 2.36816 2.36803 0.00184 10 825 2.36789 2.36776 0.00211 11 760 2.36763 ---- 0.00237

The roll stack has twelve rolls, i.e. two deflection adjustable Final rolls and intermediate rolls in between at the roller positions 2-11, which in a known manner alternately designed as hard and soft rollers are. The hard rolls are chilled cast rolls with diameters of 760/410 mm (outer diameter, Internal diameter). The soft rollers are as GG tube rolls with plastic cover and show a diameter of 825/800/428 mm (outer diameter with cover, outer diameter without cover, inner diameter) on.

It can be seen that a deviation Δf _EM from roller 2 of 0.00237 mm has already resulted for the 11th roller.

This first approach has already largely proven itself. However, in the first place only the Amplitudes of the deflections matched to one another.

The leveling of the can be further improved Load in the nip due to the fact that one of the center rollers selects or sets different bearing distances. The setting can, for example, after a change a roller may be required.

In multi-roll calenders, there are adjacent rolls usually not the same. This doesn't just apply on the first and on the last nip, as a rule of an intermediate or middle roll and one Deflection adjustment roller are limited, but also on the remaining nips, each with two intermediate rolls be limited. For example, the elastic Rolling, i.e. the rollers with an elastic Surface and the hard rollers, i.e. the rollers with an unyielding or hard surface, different Slenderness and roll diameter. The degree of slenderness results from the outside diameter Since divided by the working width AB.

mit MbML als Lagerabstand (Mitte bis Mitte Lager). The shear deformation of a roller is, among other things, a function f of the degree of slenderness Da / AB . The shear deformation also influences the curve shape of the bending line (Fig. 3) according to the following equation for the curve factors between the roll center (y = 1 at x = 0) and the edge of the working width (y = 0 at x = ½ AB).

with MbML as the bearing distance (middle to middle of the bearing).

(Definition weiter unten) ergeben sich zwangsläufig abweichende Kurvenformen ihrer Biegelinien, wie dies aus der schematischen Darstellung der Fig. 3 zu erkennen ist.With a common bearing distance MbML of center rolls with unequal

(Definition below) inevitably results in deviating curve shapes for their bending lines, as can be seen from the schematic illustration in FIG. 3.

Even if the deflection amplitudes in the middle of the roll may match the feared M or W profiles in the line load profile of the Result in nips. These are already being weakened, if you compare the deflection amplitudes adapts. However, there is an improvement if you choose the bearing spacing MbML accordingly.

oder aufgelöst nach MbML(_i+1)

It is assumed that the working width AB remains the same for all nips N. The following then applies to two neighboring rolls i and i + 1

or resolved according to MbML ( _{i + 1)}

In addition to the degree of slenderness Da / AB , the shear deformation also depends on the shear distribution number κ of the roll cross section, the transverse expansion factor µ of the roll material and the diameter ratio Di / Da for hollow bore Di as follows

These considerations will be explained using the following example example FROM = 6,360 mm MbML _i = 7,500 mm Roller 1:
Material =
chill casting Since _i = 560 mm Di _i = 250 mm κ _i = 2.01 µ _i = 0.25 Roller 2:
Material =
steel
(the elastic reference is not taken into account) Da _{(i + 1)} = 477 mm Tue _{(i + 1)} = 327mm κ _{(i + 1)} = 2.07 µ _{(i + 1)} = 0.30 Result MbML _{(i + 1)} = 7,517.4 mm ⇒ ΔL ≈ 17.5 mm.

It can be seen that there is a distance of the order of magnitude of 17.4 mm. This is quite a workable one Magnitude.

Claims (11)

Calender with a roll stack, which has two end rolls and several intermediate rolls in between, in operation two adjacent rolls, each having a deflection, form a nip, characterized in that the deflections of adjacent rolls differ from one another, one of the convex sides of one first roller adjacent second rollers has a weaker deflection than the first roller. Calender according to claim 1, characterized in that adjacent rolls each have a deflection in which an amplitude of the deflection of the surface line on the convex side of the first roller essentially corresponds to an amplitude of the deflection of the surface line of the adjacent second roller on its concave side. Calender according to Claim 1 or 2, characterized in that at least one of the rollers which are adjacent to one another has a force introduction device. Calender according to one of claims 1 to 3, characterized in that the amplitude f _{EM ( i + l)} the deflection of the second roller according to the following relationship of the amplitude f _{EM ( i )} depends on the deflection of the first roller f EM ( i +1) = 2 D ( i +1) K 2 + 4 D ( i +1) K 2 • f EU ( i ) - 2 D ( i +1) K 2 in which f EU ( i ) = f EM ( i ) - 1 4 K 2 • f 2 EM ( i ) • D ( i ) K = 16 FROM • 1 + 3 MbML - AB FROM 5 + 12 MbML - AB FROM

AB =

working width

MbML =

bearing distance

D _(i) =

Diameter of the first roller

D _{(i + 1)} =

Second roller diameter

i =

First roller index

i + 1 =

Second roller index.

Calender according to one of claims 1 to 4, characterized in that adjacent rolls have different bearing distances if they differ from one another in at least one parameter. Calender according to claim 5, characterized in that the difference in the bearing distances is in the range of 0.1% to 2% based on the larger bearing distance. Calender according to claim 5 or 6, characterized in that the bearing distance of at least one intermediate roller can be changed. Calender according to one of claims 1 to 7, characterized in that the bearings of all rolls are symmetrical to the axial center. Process for treating a web of material which is passed through several nips and pressurized there, each nip being formed by a first roller and a second roller adjacent to it, characterized in that the deflections of the two rollers are selected differently. Method according to Claim 9, characterized in that the deflection of the first roller is controlled in such a way that the amplitude of the deflection of the surface line on the convex side of the first roller corresponds to the amplitude of the deflection of the surface line on the concave side of the second roller. A method according to claim 9 or 10, characterized in that in the case of unequal rollers, the bearing distance of one roller is set differently than the bearing distance of the other roller.

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