EP0732445B2 - Calander for treating a paper web - Google Patents

Description

The invention relates to a calender according to the preamble of claim 1.

Calenders are from the Brochure "The new super calender concept" of the company Sulzer Papertec Krefeld GmbH from Mal 1994 known. They are used both coated and uncoated Satin paper, such as printing paper or silicone base papers. Called "hard" rollers metal rollers with a smooth and hard surface, which are essentially for smoothness and shine are responsible. Called "soft" rollers one rolls with an elastic or soft surface, which is essentially for even compaction to care. The alternating gap is required so both sides of the paper web are approximately uniform Experience treatment. It is common to have a calender to use with 12 to 18 rollers, the Alternating gap is located in the lower half of the stack. This takes into account the fact that the the stack of paper webs running from top to bottom is deformed to a lesser extent than below, well the load mostly acting from the upper end by the weights of the rollers and possibly with it connected parts, such as overhanging weights, increases towards the bottom. This leads to one from above downward increasing compressive stress and / or Dwell time in the working columns. Have these calenders therefore a large height and are due to the large number of rollers very expensive. A generic calender is from "Das Papier" July 1962, pages 277 to 285. It is a laboratory calender with 8 rolls.

The invention has for its object a To specify calenders of the type described at the outset, , of largely the same satin results for one certain paper type, but a smaller one Construction height and its manufacturing and operating costs are lower.

This object is achieved according to the invention solved by the features of claim 1.

In this construction, the number of working gaps is above or below the alternating gap equal to the number of working columns below the Alternating gap and thus less than the known one Supercalender. Nevertheless, almost the same satin result achieved because - while maintaining a maximum permissible compressive stress in the lowest working gap - because of the lower number of rollers and because of the lower weight influence of the rollers and any associated parts already in the first working gap a higher line load than before can and the line load increase less than in the known cases. The soft rollers are removed Cavities in particular come with hollow tubes with a cover into consideration. This ensures that the rollers themselves are light in weight. this happens in the hard rollers by the get the smallest possible diameter. With the soft One should roll instead of the compact and heavy rolls with paper cover lighter construction Use constructions.

The sum of the line loads is a good guide for the mechanical impact on the paper. Even if the total of the line loads is above the alternating gap is not identical to the total the line loads are below the alternating gap one still fully meets the requirements of practice, excellent calendering results.

Since the calender has a lower overall height, needed one also lower buildings, what the set-up costs significantly lowers. Furthermore, the calender because of the lower number of rollers in both Production and operation cost inexpensive.

It is particularly recommended that the roll stack Such a B-roll calender has eight rolls, where there is above and below the alternate spar There are essentially three working columns the same as a well-known 12-roll calender. The web treatment below the alternating gap is the same in both cases. The railway treatment Above the alternating gap, there is no longer any carried out by four working columns; this is what it is about but the working column with the least influence of deformation. In contrast, with the new construction can handle a very high line load in the first working gap be applied so that the paper web immediately undergoes significant deformation. At the same Compressive stress in the lowest working gap like one 12-roll calenders are therefore in the top working gap of a B-roll calender reaches compressive stresses, which is a uniformity in the satin result effect on both sides of the paper web. That is called three nips above the wax gap at 8-roll calenders achieve almost the same result like the first seven on the 12-roll calender Arbeltsspalte.

The Kalandrierleistung can be more fully characterized, take into account that the sum of the products of dwell time and mean compressive stress in the tsspalten Arbe ⁱ is above the change gap is at least 80% of the sum of said products in the working gaps below the change gap. Because dwell time and compressive stress are two decisive factors for paper deformation.

In order to keep the effective weight as small as possible, it is recommended that the working plane of the roll stack is inclined to the vertical. With this construction only the vertical component of the weight goes in increasing the line load.

There are also advantages if the soft roller is one Has plastic jacket. Such references are essential thinner than paper covers and accordingly lighter.

It is also recommended that the soft Roll a fiber reinforced plastic such as epoxy having. By fiber reinforcement, in particular With carbon fibers, stability and low can be Combine weight with each other.

It is favorable that the top and / or bottom roller is a soft roller. If both end rollers are soft, the result is a 6-roll calender. If only one end roller is soft, you can stack rolls with odd Provide number of rollers. Soft end rollers can also be used lighter than hard end rollers be carried out what the adjustment of the line load sums above and below the alternating gap facilitated.

A particularly low weight is achieved that the roller shell made of one material is insufficient There is wear resistance and a cover made of an elastic plastic, and that the Plastic has a higher wear resistance than that Jacket material.

, This is especially true when the roll shell made of lamellar graphite cast iron, i.e. a cast iron with lamellar Graphite. Whose wall thickness can almost by comparison with a chilled cast iron roller jacket Can be reduced by 50%. However, this is cast iron only little wear-resistant. This disadvantage, however, will balanced that the cover made of elastic Plastic serves as a wear protective layer. For this A layer thickness between B and 15 is sufficient for this purpose mm, preferably 10 mm.

An alternative provides that the roller jacket made of spheroidal graphite cast iron, i.e. a cast iron with spherical Graphite. This allows a reduction in wall thickness compared to chilled cast iron of up to 59%.

In a further embodiment, it is ensured that at least a hard roller is heated. this makes possible it to apply thermal deformation energy so that overall worked with a lower line load can be. In addition, there is the fact that there are different Heating in the different working columns a higher degree of adjustment of the satin result can achieve.

The upper and / or lower rollers can advantageously be heated. Already in the first and also in the last gap therefore heat can be supplied to what is on both sides of the paper web Offers correction options.

It is particularly favorable that at least the top one Center roll is hard and heatable. Here too Deformation energy already in the first working gap of the paper web supplied in the form of heat. Across from an otherwise necessary heating of the top roller but this has the advantage that the top roller very much can be done much easier and cheaper, less Exposed to temperatures and deformed more may be without the seal underneath suffers.

However, the cheapest is when everyone is tough Center rolls are heated. By making the top and possibly also the bottom middle roller trained as a hard roller, you can while maintaining the total number of rollers the number of hard and increase heatable center rolls by one. This allows more heat energy in a simple way or the same thermal energy at a lower temperature level supply.

In particular, the heating can be carried out here Water vapor take place, which can be supplied with excess pressure. This type of heating is much easier and cheaper than heating with oil, as with a heated deflection compensation roller required would.

It also offers advantages that the top and / or bottom roller is a deflection controllable roller, at which is a roll shell over hydrostatic support elements on a penetrating, non-rotatable one Carrier is supported. Deflection control allows the line load across the width of the paper web to keep constant, so a very even one To achieve a satin finish.

It is also recommended that the deflection controllable Roll a multi-zone control has, in which the support elements individually or in pairs Hydraulic fluid can be supplied at different pressures is. This multi-zone control in which the individual Support elements arranged close to each other and an axial width of 5 to 20, for example cm, leads in conjunction with a soft roller jacket to influence the paper individually over very narrow areas already in the top Working gap, leading to a high level of uniformity the desired parameters across the paper web leads.

Fig. 1

eine schematische Darstellung eines erfindungsgemäßen Kalanders,

Fig. 2

eine abgewandelte Ausführungsform,

Fig. 3

einen Schnitt durch eine weiche Walze,

Fig. 4

schematisch einen 6-Walzen-Kalander,

Fig. 5

schematisch einen 9-Walzen-Kalander und

Fig. 6

schematisch einen 7-Walzen-Kalander.

The invention is explained below with reference to exemplary embodiments shown in the drawing. Show it:

Fig. 1

1 shows a schematic representation of a calender according to the invention,

Fig. 2

a modified embodiment,

Fig. 3

a cut through a soft roller,

Fig. 4

schematically a 6-roll calender,

Fig. 5

schematically a 9-roll calender and

Fig. 6

schematically a 7-roll calender.

The calender 1 illustrated in FIG. 1 has one Roller stack consisting of eight rollers, namely a heatable, deflection controllable hard top roller 2, a soft roller 3, a heatable hard roller 4, a soft roller 5, one soft roller 6, a heatable hard roller 7, one soft roller 8 and a heatable, deflection controllable hard bottom roller 9. This way there are six working columns 10 to 15, each limited by a hard roller and a soft roller are, and in the middle of an alternating gap 16, which by two soft rollers 5 and 6 is limited.

A paper web 17 becomes a paper machine 18 fed, passes under the leadership of idlers 19 the working column 10 to 12, the alternating gap 16 and the working column 13 to 15, whereupon they are in a kelvorrichtung 20 is wound up. In the three upper working columns 10 to 12 is the paper web with one Page, in the three lower working columns 13 to 15 with the other side on the hard rollers, so that the desired surface structure on both sides, for example Gloss or smoothness is achieved.

Because of the direct connection of the calender 1 the paper machine 18 results in in-line operation. For this reason, each of the rollers has 2 to 9 its own drive 21. This enables retraction the paper web 17 during operation.

a) Über eine Leitung 24 wird die Kraft P festgelegt, mit der die Oberwalze 2 nach unten gedrückt wird, wobei die Unterwalze 9 zweckmäßigerweise ortsfest gehalten ist. Die Belastung kann auch in umgekehrter Richtung erfolgen, wobei die Kraft P auf die Unterwalze 9 wirkt und die Oberwalze 2 ortsfest gelagert ist.

b) Über die Leitungen 25 und 26 werden die Vorrichtungen 27 bzw. 28 zum Durchbiegungsausgleich der Oberwalze 2 und der Unterwalze 9 mit Druckmittel beaufschlagt. Diese Vorrichtungen sorgen dafür, daß über die Länge der Walzen eine gleichmäßige Druckspannung herrscht, wie dies an-sich bekannt ist. Hierfür können alle üblichen Vorrichtungen verwendet werden, insbesondere solche, bei denen Stützelemente nebeneinander in einer Reihe angeordnet sind und einzeln oder zonenweise mit unterschiedlichem Druck beaufschlagt werden können.

c) Die Walzen 2, 4, 7 und 9 sind beheizbar, wie dies durch Pfeile H angedeutet ist. Die Heizenergie wird über strichpunktierte Pfade 27 bis 30 zugeführt. Dies kann durch elektrische Beheizung, durch Strahlungsheizung, mit Hilfe eines Wärmeträgers u dgl erfolgen.

A control unit 23 has several functions:

a) The force P with which the upper roller 2 is pressed down is determined via a line 24, the lower roller 9 advantageously being held stationary. The loading can also take place in the opposite direction, the force P acting on the lower roller 9 and the upper roller 2 being mounted in a stationary manner.

b) Via lines 25 and 26, devices 27 and 28 for compensating for deflection of upper roller 2 and lower roller 9 are pressurized. These devices ensure that there is a uniform compressive stress over the length of the rollers, as is known per se. All conventional devices can be used for this, in particular those in which support elements are arranged next to one another in a row and can be subjected to different pressures individually or in zones.

c) The rollers 2, 4, 7 and 9 can be heated, as indicated by arrows H. The heating energy is supplied via dash-dotted paths 27 to 30. This can be done by electrical heating, by radiant heating, with the help of a heat transfer medium and the like.

When the stack is loaded by a force P there is a line load in the first working gap 10 f1, which depends on the force P and the effective weight of the Upper roll 2 depends, in the second working gap 11 one Line load f2, the force P and the weights the two upper rollers 2 and 3 depends, and so on up to the line load f6, that of the force P and the effective Weights of all rollers 2 to 8 depends.

1) Die harten Walzen 4 und 7 haben den kleinstmöglichen Durchmesser.

2) Die Wirkebene des Walzenstapels ist schräg gestellt, also zur Vertikalen geneigt (Fig. 2). Daher wirkt die Gewichtskomponente G einer jeden Walze nur mit einer Komponente G 1 in Richtung der Strekkenlast.

3) Die weichen Walzen, z.B. 3, weisen ein Tragrohr oder Walzenmantel 32 aus einem Material unzureichender Verschleißfestigkeit mit einem Hohlraum 33 auf. Auf dem Walzenmantel ist ein Kunststoffbezug 34 angeordnet, der beispielsweise aus faserverstärktem Epoxidharz bestehen kann. Eine solche weiche Walze ist wesentlich leichter als eine übliche Walze mit einem Bezug aus Fasermaterial und hat infolge des Kunststoffbezuges eine hohe Verschleißfestigkeit.

4) Überhängende Gewichte, die das wirksame Gewicht der Walze verstärken, werden in an sich bekannter Weise durch eine Stützvorrichtung kompensiert, was beispielsweise im Rahmen eines Kalanders mit an Schwenkhebeln gelagerten Walzen geschehen kann (vgl. EP 0 285 942 B1).

According to the additional weight influence should be kept as small as possible. Various measures can be provided for this individually or in combination:

1) The hard rollers 4 and 7 have the smallest possible diameter.

2) The active plane of the roll stack is inclined, that is to say inclined to the vertical (FIG. 2). Therefore, the weight component G of each roller acts with only one component G 1 in the direction of the stretch load.

3) The soft rollers, for example 3, have a support tube or roller shell 32 made of a material with insufficient wear resistance with a cavity 33. A plastic cover 34 is arranged on the roll shell, which can consist, for example, of fiber-reinforced epoxy resin. Such a soft roller is much lighter than a conventional roller with a cover made of fiber material and has a high wear resistance due to the plastic cover.

4) Overhanging weights that increase the effective weight of the roller are compensated in a manner known per se by a support device, which can be done, for example, in the context of a calender with rollers mounted on pivoting levers (cf. EP 0 285 942 B1).

Due to the small number of only eight rollers and the low weight of these rollers is one specified line load f6 in the lowest working gap 15 in the uppermost working gap 10 a line load f1 available, far above the usual values lies. This also applies to the line loads f2 and f3 in Working columns 11 and 12. Hence the treatment in the first three working columns 10, 11 and 12 of the treatment in the last three working columns 13, 14 and 15 so closely approximated that the satin effect both sides of the paper web are largely the same. Any necessary corrections can be made with the help different heating of the heated rollers 2, 4, 7 and 9 can be made.

The purpose of the correct dimensioning is according to the invention provided that the sum of the line loads f1 + f2 + f3 of the top working column 10, 11 and 12 at least 80% of the total of the line loads f4 + f5 + f6 the bottom three working columns is 13, 14 and 15.

If you don't, you will get similar results the line load in the individual columns, but the Dwell time t and the compressive stress p in each working gap taken into account by the sum of the products t. p for the top three working columns with the sum of these Products compared for the three lower working columns becomes. Again, the top sum should be at least Amount to 80% of the lower sum.

In one embodiment with a vertical roll stack 1 the calender had a width of 8.5 m and a web speed of 800 m / min. Simply by reducing the weight of the soft ones Rolling of around 40% reached the sum of Products from medium compressive stress p and dwell time t in the working columns above the alternating gap 16 a value of 82% of the total of the products in the working gaps below the alternating gap. Through further measures you can get even higher values with the vertical stack achieve, for example, 83 to 86%. With special designs, like the inclined stack, too higher values can be achieved.

Values between 45 and 60 N / mm ² resulted as the compressive stress p in the working gap, especially in the lowest gap. With the help of the heating H, the heated rollers 2, 4, 7 and 9 were given a surface temperature between 100 and 150 ° C. The diameter of the soft rollers and the elasticity of their covering 34 were chosen so that there was a gap width of about 2 to 15 mm , preferably about 8 mm. Depending on the web speed, this leads to dwell times t in each working gap of 0.1 to 0.9, preferably 0.2 to 0.5 ms. It is preferred if the temperature T is only slightly above the lower limit, for example 110 ° C., if the compressive stress p is only slightly above the lower limit, for example 50 N / mm ² . Compared to a 12-roll calender, slight increases in thermal and mechanical energy are therefore sufficient to achieve the same calendering results in an 8-roll calender.

A 4-roll calender can also be used on the same principle be built up for simpler applications sufficient, but also one on both sides have approximately the same satin finish.

The roll stack illustrated in FIG. 4 has a soft top roller 102 and a soft bottom roller 109 on. The alternating gap located exactly in the middle 116 is made by two soft rollers 105 and 106 limited. Two hard rollers 103 and 107, which the End rollers 102 and 109 are adjacent with Water vapor, which is supplied with excess pressure, is heated.

In the exemplary embodiments described so far the alternating gap was exactly in the middle of the an even number of rolls having rolls. Below are stacks with an odd one Number of rollers described.

5 shows a 9-roll calender, which is a soft top roller 202, but a hard bottom roller 209 has. The changing gap 216 is between the soft middle roller 205 and the soft one Neighbor roller 206 arranged. Otherwise change heated hard center rolls with soft rolls.

6 are a total of seven rollers used. It is a hard top roller 302 and a soft lower roller 309 are provided. The alternating gap 316 is between the soft middle roller 305 and the neighboring one soft roller 306. Otherwise, heated hard ones change medium rolls with soft rolls.

4 to 6 in the exemplary embodiments indicated that the top rollers and bottom rollers in similar to that in Fig. 1 with hydraulic support elements are provided. The roller shells can be constructed similarly to FIG. 3 and for example have a support tube made of spheroidal or lamellar graphite cast iron and wear a cover made of elastic plastic.

Claims (17)

1. Calender with a roll stack which comprises working gaps (10 to 15) formed in each case between a hard roll and a soft roll, and a change-over gap (16) formed between two soft rolls, for the treatment of a paper web which in the working gaps in each case for a dwell time is exposed to a compressive stress, wherein the roll stack comprises less than 10 rolls and the change-over gap (16) is arranged at the centre of the stack, i.e. in the case of an even number of rolls between the two most central rolls and in the case of an uneven number of rolls between the most central roll and an adjacent roll, characterised in that, using soft rolls (3) containing cavities (33), the effective weight of the rolls (2 to 8) and any associated parts is so low that the sum of the line loads (f1 + f2 + f3) of the working gaps (10, 11, 12) above the change-over gap (16) is at least 80% of the sum of the line loads (f4 + f5 + f6) of the working gaps (13, 14, 15) below the change-over gap (16).
2. Calender according to claim 1, characterised in that the roll stack comprises eight rolls (2 to 9).
3. Calender according to claim 1 or 2, characterised in that the sum of the products of dwell time (t) and mean compressive stress (P) in the working gaps (10, 11, 12) above the change-over gap (16) is at least 80% of the sum of said products in the working gaps (13, 14, 15) below the change-over gap (16).
4. Calender according to any of claims 1 to 3, characterised in that the working plane of the roll stack is inclined to the vertical.
5. Calender according to any of claims 1 to 4, characterised in that the soft rolls (3) comprise a plastic casing (34).
6. Calender according to any of claims 1 to 5, characterised in that the soft roll (3) comprises a fibre-reinforced plastic.
7. Calender according to any of claims 1 to 6, characterised in that the upper and/or lower roll (102, 109; 202; 309) is a soft roll.
8. Calender according to any of claims 1 to 7, characterised in that the soft roll (102, 109; 202; 309) comprises a roll casing (32) which is made of a material with inadequate wear resistance and carries a covering (34) made of a resilient plastic, and in that the plastic has a higher wear resistance than the casing material.
9. Calender according to claim 8, characterised in that the roll casing (32) is made of lamellar graphite cast iron.
10. Calender according to claim 8, characterised in that the roll casing (32) is made of spheroidal graphite cast iron.
11. Calender according to any of claims 1 to 10, characterised in that at least one hard roll (2, 4, 7, 9) can be heated.
12. Calender according to any of claims 1 to 11, characterised in that the upper and/or lower roll (2, 9) is hard and can be heated.
13. Calender according to any of claims 1 to 11, characterised in that at least the uppermost centre roll (4; 103) is hard and can be heated.
14. Calender according to claim 13, characterised in that all the hard centre rolls (4, 6, 8, 11, 13; 103, 107) can be heated.
15. Calender according to claim 13 or 14, characterised in that heating takes place by means of steam which can be supplied at excess pressure.
16. Calender according to any of claims 1 to 15, characterised in that the upper and/or lower roll (2, 9; 102, 109; 202, 209; 302, 309) is a roll that can be controlled for deflection, in which a roll casing is supported by means of hydrostatic supporting elements (27, 28) on a non-rotatably held carrier passing through it.
17. Calender according to claims 7 and 16, characterised in that the roll (102, 109; 202; 309) that can be controlled for deflection comprises a multi-zone control system in which compressed fluid can be supplied at different pressure to the supporting elements (27, 28) individually or in pairs.

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