EP1609907B1 - Extended nip calender and process for satinizing a material web - Google Patents

Abstract

Compensation is provided for thinning of the pressure shoe (9) roller (2) casing (5), which operates against a counter-roller (3), forming a wide nip (4). Compensation includes a casing (5) which is thicker near its edges than in the middle. One of the surfaces bordering the wide nip deforms in a direction in which central area pressing becomes more uniform. Compensation reduces towards the axial center of the working region. Further compensation variants are cited. The casing includes a reinforcing inlay, e.g. a fabric. The compensation is located in the half of the casing thickness, which is remote from the counter roller. It acts inside the casing and/or on the pressure shoe, which it heats. In the central region it exerts reduced pressure towards the counter roller. It produces greater pressure at the edges of the working region. The compensation produces a locally-enlarged oil cushion between the shoe and the casing. The pressure shoe projects further towards the counter roller at the edges, where it is thicker than in the center. The compensation acts on the counter roller, heating it more at the ends than in the central region. The compensation provides an expansion zone for the casing, outside the working region. Compensation is controlled as a function of measured product thicknesses. An independent claim is included for the corresponding method of glazing (or satinizing).

Description

The invention relates to a Breitnipkalander with a shoe roll having a circumferential jacket and a pressure shoe, and a counter-roller, which forms a nip with the shoe roll together, wherein the pressure shoe is displaceable in the direction of the backing roll and the jacket in a working area of a circular shape out radially deformed outwards.

For example, a nip calender is used to satinize a paper or board web. The calendering in the nip calender has the advantage over a calendering in a "normal" calender, which has two cooperating rollers, that the treatment time can be extended, while the compressive stresses prevailing in the nip are usually lower than those in a formed between two rollers nip. This results in the web suffers a smaller volume loss in the nip. However, the surface properties produced in a nip are quite similar to the surface properties achieved in a "normal" calender.

The counter-roller is usually heated. The ruling on the surface of the backing roll temperatures are so high that there is a risk that the coat is damaged when it comes into contact with the counter roll. As long as the material web, which is calendered in the nip, is located between the jacket and the counter-roller, the risk of damage is comparatively small because the material web prevents direct contact between the jacket and the counter-roller. However, outside the width of the material web, care must be taken that contact between the counter-roller and the jacket does not take place. To meet this requirement, the jacket is pressed by the pressure shoe outwards in the direction of the counter roll, so that the jacket has conical sections in the region of the counter roll at both ends.

This is in the EP-A-1 424 439 proposed to reduce the roll shell diameter at the ends.

It has now been found that, especially with relatively thin papers, especially with thin graphic papers, problems arise in the reeling when these papers have been treated in a Breitnipkalander.

The invention has for its object to reduce problems in the reeling of webs that have been satined in a wide nip.

This object is achieved in a Breitnipkalander of the type mentioned in that a jacket thinning compensation is provided.

It is in such a Breitnipkalander assume that the problems in the reeling are due to a thickening of the web at the edge. For thin graphic papers, which have a thickness of about 50 to 55 microns in the middle of the web, it can be seen that they are at the edge up to about 5 microns thicker. The too thick edge then leads to problems in the reeling. A second pass through a wide-nip calender is occasionally problematic. Furthermore, it can be observed that the roughness in the edge region is greater and the gloss is lower. However, these described effects can only be observed in the peripheral areas, but not over the web width. This is attributed to the fact that the sheath thins somewhat in the edge regions of the material web, because it is deformed out of its cylindrical shape by the pressure shoe. It is now assumed that these thinner shell sections have the consequence that the material web is less compressed at the edge. The calendering effects are also less pronounced in this edge area. These problems can now be remedied by compensating for the thinning of the jacket. In addition, it is a particular advantage that the gloss becomes more uniform across the width of the web. There are a number of possibilities for compensating the shell dilution.

For example, one can use a sheath which has a greater thickness in the region of the lateral ends of the working area than in a central region of the working area. It is thus precompensated for the dilution of the shell by making thicker coat where dilution is to be feared during operation. This has the consequence that the coat throughout the work area has the same thickness and negative effects can not occur due to a thin shell on the edge.

It is also advantageous if the jacket dilution compensation deforms one of the surfaces which delimits the broad nip in a direction in which the average surface pressure becomes more uniform. So you set the "thickness" of the wide nip over the entire working width so to speak "constant".

It is also advantageous if the jacket dilution compensation has a decreasing effect in the direction of the axial center of the working region. It can be observed namely that the jacket dilution does not stop abruptly, but the coat from the "kink" at the end of the Anpreßschuhs starting an increasing thickness toward the axial center of the work area learns. For example, the length in which the jacket returns to its normal thickness, about 20 to 35 mm. If one now lets the effect of the material compensation decrease, then the fact is taken into account that with increasing approximation At the axial center of the shell, the thinning of the shell becomes weaker.

Preferably, the jacket has a reinforcing insert. Such a reinforcing insert, which may be formed for example by a fabric layer, causes the jacket can be stretched less here. This limits the elongation to a thickness range of the jacket, which lies radially outside the reinforcing insert. Under favorable circumstances, the sheath is even radially compressed within the reinforcing insert when it is deformed by the pressure shoe. As a result, the total dilution of the shell can be kept slightly smaller, so that you can operate the material dilution compensation with less effort.

Preferably, the reinforcing insert is arranged in the half of the thickness of the shell facing away from the counter-roller. For example, the reinforcing insert may be arranged in a range of 10 to 50% of the thickness of the shell. This avoids a negative influence on the Satinagevorgangs by the reinforcing insert.

The jacket dilution compensation preferably acts on the inside of the jacket. There is enough space available, namely inside the shoe roll. Measures that work from the outside are then not necessarily required.

It is preferred that the jacket dilution compensation acts on the pressure shoe. By influencing the interaction between the pressure shoe and the jacket can be compensated in the described small orders of magnitude quite a dilution of the shell.

It is preferred that the jacket dilution compensation heats the pressure shoe. By heating the pressure shoe increases its volume and then presses, so to speak, more strongly against the counter roll.

Alternatively or additionally, it can be provided that the jacket dilution compensation generates a reduced contact pressure in the middle region in the direction of the counter-roller. In the middle axial region of the working area of the pressure shoe is thus loaded to a lesser extent in the direction of the counter roll, as at the axial ends of the working area. This also means that the thickness of the material web can be kept uniform in the extended nip and the surface properties over the width of the material web can be kept practically constant.

It is advantageous that the jacket dilution compensation generates an increased contact pressure at the lateral ends of the working area. The pressure shoe is thus something "bent" or in any case loaded so that the shell dilution is compensated.

The jacket dilution compensation preferably produces an enlarged oil cushion between the pressure shoe and the jacket. Such an oil pad is usually present between the pressure shoe and the jacket in order to reduce the friction between the pressure shoe and the jacket. If you now have a larger, i. thicker or with greater force acting oil pad produced at the axial ends of the work area, then you can easily compensate with the help of this thickened oil pad jacket dilution.

Preferably, the pressure shoe in the region of the lateral ends of the working area is further in the direction of the counter-roller. The pressure shoe is thus not only curved in the circumferential direction of the backing roll, but he has a corresponding "curvature" in the axial direction of the backing roll on. However, this curvature is limited to relatively small areas at the axial ends of the pressure shoe. By this deformation in the direction of the backing roll, the dilution of the shell can also compensate. Such a "curvature" can be realized for example by the fact that the edge support elements are supplied under the pressure shoe with more pressure or further extended.

In this case, it is preferable for the pressure shoe to be thicker in the region of its lateral ends than in a central region. This is an embodiment that can be made, for example, by grinding.

The jacket dilution compensation can also act on the counter roll.

In this case, it is preferred that the jacket dilution compensation heats the counter-roll, wherein the heating in the region of the lateral ends of the working region is stronger than in a central region of the working region. Where the heating is stronger, the diameter of the counter roll is increased. Since this magnification must be only a few microns, the heating of the counter roll is sufficient. Alternatively or additionally, it is possible to provide the counter-roller with an enlarged diameter range at the axial edge.

Another measure is that the jacket dilution compensation places a stretch zone of the jacket outside the work area. So you move the dilution caused by the strain, in an area outside the work area.

The jacket dilution compensation can also have a thickness measuring device connected downstream of the broad nip, which measures the thickness of a material web passing through the broad nip, wherein the shell dilution compensation changes its effect as a function of the determined thickness. This gives a control loop, which ensures that the material to be satinized over its entire width despite the thinning of the shell receives a constant thickness.

In a method of calendering a web in a nip calender with a shoe roll having a circumferential jacket and a pressure shoe, and a counter roll which forms a nip with the shoe roll, wherein the pressure shoe is displaced in the direction of the counter roll and the shell in deformed radially outward from a working area out of a circular shape, the above-mentioned object is achieved by compensating for a jacket dilution.

With this measure, it is avoided that the thinning of the jacket, which results from the circular shape by the shaping out of the jacket, has negative effects on the calendering, in particular on the thickness configuration, of the material web running through the widened nip. For jacket dilution can be used above in connection with the Breitnipkalander proposed measures.

Fig. 1

eine schematische Schnittansicht durch einen Breitnipkalander und

Fig. 2

einen vergrößerten Ausschnitt Z aus Fig. 1.

The invention will be described below with reference to a preferred embodiment in conjunction with the drawings. Herein show:

Fig. 1

a schematic sectional view through a Breitnipkalander and

Fig. 2

an enlarged section Z out Fig. 1 ,

A Breitnipkalander 1 has a shoe roll 2, which forms a broad nip 4 with a counter-roller 3 through a web of material not shown is performed to be satined there. The material web is, for example, a web of paper or cardboard.

The counter-roller 3 is heated by means not shown. For heating, a heat transfer medium can be used, for example a hot liquid or a hot gas, for example steam. A heating from the outside by means of inductive or infrared heaters is possible.

The shoe roll 2 has a jacket 5, which is closed at its two axial ends by end plates 6, which are supported by bearings 7 on a stationary axis 8.

The jacket 5 is pressed by a pressure shoe 9 in the direction of the counter roll 3, i. through the pressure shoe 9 one is able to act with a certain pressure on the web 4 passing through the material web.

The pressure shoe 9 is supported on the axis 8 and is loaded by pressure transducer 10 and above all shifted away from the axis 8, so that the jacket 5, as in Fig. 1 shown deformed from its circular shape. Conical sections 11 then result on the two axial ends because the axially outer ends of the jacket 5 are fastened to the end plates 6 and thus are not displaced further radially outward can be. By this formation of the jacket 5 prevents the jacket 5 comes outside of a working area in which the material web is arranged, with the hot counter roll 3 in contact.

Fig. 2 shows now the end portion of the pressure shoe 9 with the jacket 5 and the backing roll 3. Due to the deformation of the shell 5 results in the section 11 an elongation, which is symbolized by a hatched circular segment 12. Of course, the strain is not limited to this annulus segment 12, but extends around an edge 13 at the axial end faces of the pressure shoe 9 for about 20 to 35 mm. Since the material of the jacket 5 has a volume constancy, a reduction in its thickness is associated with the expansion, that is to say an increase in the axial length of the jacket 5. It corresponds to the volume that would additionally be required by the circular ring segment 12. This decrease in thickness is not particularly great. It is in the range of about 2 to 30 microns. It is the greater, the steeper the angle with which the jacket 5 is deflected. It is the bigger, the thicker the coat is originally. It is in turn larger, the stronger the pressure shoe 9 is raised. However, a relatively small decrease in thickness also causes the material web passing through the wide nip 4 to be somewhat less compressed at the lateral edges. For thin graphic papers, which have a thickness of about 50 to 55 microns, one can observe a thickening at the edge by about 5 microns. The too thick edge leads to problems with the reeling as well as the second pass through the Breitnipkalander 1. Furthermore, the roughness in the edge region is greater and the gloss lower. However, these effects are limited to a range of about 25 mm from the edge of the web.

Such an error is due neither to a thermal camber of the counter-roller 3 nor to a deformation of the Anspreßschuhs 9 in the edge region. Rather, such an error is mainly due to the above-mentioned thinning of the jacket 5.

To eliminate this phenomenon, one now compensates for the dilution of the shell. This measure is referred to as "shell dilution compensation" for short. It can be realized in different ways, which are briefly described below.

It is possible either to deform the mating roll or the pressure shoe or the jacket 5 in the region of the axial end of the working region in such a way that the widened nip 4 maintains a constant thickness over its working width.

In any case, it is favorable if the jacket dilution compensation has an effect which decreases towards the axial center of the counter-roll 3 and is expediently limited to the small edge region on the order of 20 to 50 mm.

For example, it is possible to use a jacket which has a slightly increased thickness in the region of the circular ring segment 12, if appropriate also in the sections 11 and in the sides of the circular ring segments 12 opposite the sections 11. Thus, the shell dilution is precompensated, as it were, i. in the deformed state, the jacket then at least in the work area has the same thickness everywhere.

The jacket 5 may have a reinforcing insert 14. Such a reinforcing insert 14 may be formed for example by a fabric. The reinforcing insert 14 is located in the half of the jacket 5, which faces away from the counter-roller 3. For example, if the sheath has a thickness of 5 mm, then a material thickness of about 3 mm remains from the reinforcing insert 14 to the upper side of the sheath 5, which faces the counter-roll 3.

It can now be assumed in the first Nährung that the jacket does not stretch in the region of the reinforcing insert 14, but only radially outside of the reinforcing insert 14. Under favorable circumstances, the jacket is radially compressed within the reinforcing insert 14 so that the shell dilution less significant falls.

It is now possible to act on the inside of the jacket 5 measures to compensate for the jacket dilution. A first measure, symbolized by an arrow 15 is, is that one heats the pressure shoe 9 at its axial ends. This leads to a slight thickening of the pressure shoe 9 in the region of its axial ends and thus to a compensation of the thinning of the shell. It can also, as shown by an arrow 16, in the axial center of the pressure shoe a reduced contact force in the direction of the pressure shoe 9 act or at the axial ends, as shown by an arrow 17, an increased contact pressure on the Pressing shoe 9 let act. Both measures cause the broad nip 4 over its axial length (which is the extension parallel to the axis 18 of the mating roll 3) has a constant thickness.

One can also, as indicated by an arrow 19, between the pressure shoe 9 and the jacket 5 feed an enlarged and thus thicker oil pad. Between the pressure shoe 9 and the jacket 5 a lubrication is usually anyway generated, for example, by a hydrostatic or hydrodynamic oil pad. If one then feeds oil in the region of the axial ends under a greater pressure or with a larger volume, then the jacket 5 is moved to a lesser extent more strongly against the counter-roller 3.

It can, as shown by an arrow 20, the pressure shoe 9 also bulge in a small extent in the direction of the backing roll 3, in particular the fact that the pressure shoe 9 has a slightly larger thickness in this area.

Alternatively or additionally, the jacket dilution compensation can also be applied to the counter roll 3, for example by means of heating elements 21, which act on the axial end regions of the counter roll 3, ie heat the end regions more strongly than a central region.

Such heating leads to an increase in diameter of the counter roll 3 and thus also to a homogenization of the wide nip 4 over its axial length.

In a manner not shown, you can also shift the dilution zone of the shell axially outward.

In some cases it is also sufficient to improve the smoothness effect at the edge of the web. This can be achieved, for example, by zonewise heating of the mating roll, ie more temperature at the edge by the heating elements 21. The higher temperature also increases the smoothness effect. The heating has therefore in addition to the diameter increase an additional effect. Even by a larger applied amount of moisture, ie steam or water, at the edge of the smoothing effect can be increased.

In a manner not shown, it is possible to ensure that the thickness of the material web, in particular at the edge region, is measured during production. The jacket dilution compensation is then regulated as a function of the determined thickness of the material web, so that the effects of Mantelverdünnung minimized and the cross-profile are equalized.

Claims (18)

1. Extended nip calender (1) having a shoe roll (2) which has a revolving shell (5) and a pressure shoe (9), and an opposing roll (3) which, together with the shoe roll (2), forms an extended nip (4), it being possible for the pressure shoe (9) to be displaced in the direction of the opposing roll (3) and to deform the shell (5) radially outwards out of a circular shape in a working region, characterized in that a shell thinning compensating means is provided.
2. Extended nip calender according to Claim 1, characterized in that the shell thinning compensating means has a shell (5) which has a greater thickness in the region of the lateral ends of the working region than in a central region of the working region.
3. Extended nip calender according to Claim 1 or 2, characterized in that the shell thinning compensating means deforms one of the surfaces which bounds the extended nip (4) in a direction in which the average surface pressure becomes more uniform.
4. Extended nip calender according to one of Claims 1 to 3, characterized in that the shell thinning compensating means has an effect that decreases in the direction of the axial centre of the working region.
5. Extended nip calender according to one of Claims 1 to 4, characterized in that the shell (5) has a reinforcing inlay (14).
6. Extended nip calender according to Claim 5, characterized in that the reinforcing inlay (14) is arranged in the half of the thickness of the shell (5) that faces away from the opposing roll (3).
7. Extended nip calender according to one of Claims 1 to 6, characterized in that the shell thinning compensating means acts on the inside of the shell (5).
8. Extended nip calender according to Claim 7, characterized in that the shell thinning compensating means acts on the pressure shoe (9).
9. Extended nip calender according to Claim 8, characterized in that the shell thinning compensating means heats the pressure shoe (9).
10. Extended nip calender according to one of Claims 1 to 9, characterized in that, in the central region, the shell thinning compensating means generates a reduced pressing force in the direction of the opposing roll (3).
11. Extended nip calender according to Claim 10, characterized in that, at the lateral ends of the working region, the shell thinning compensating means generates an increased pressing force.
12. Extended nip calender according to one of Claims 1 to 11, characterized in that the shell thinning compensating means generates an enlarged oil cushion between the pressure shoe (9) and the shell (5).
13. Extended nip calender according to one of Claims 1 to 12, characterized in that, in the region of the lateral ends of the working region, the pressure shoe (9) protrudes further in the direction of the opposing roll (3).
14. Extended nip calender according to Claim 13, characterized in that, in the region of its lateral ends, the pressure shoe (9) is thicker than in a central region.
15. Extended nip calender according to one of Claims 1 to 14, characterized in that the shell thinning compensating means acts on the opposing roll (3).
16. Extended nip calender according to Claim 15, characterized in that the shell thinning compensating means heats the opposing roll (3), the heating being more intense in the region of the lateral ends of the working region than in a central region of the working region.
17. Extended nip calender according to one of Claims 1 to 16, characterized in that the shell thinning compensating means has a thickness measuring device connected downstream of the extended nip (4), which measures the thickness of a material web running through the extended nip, the shell thinning compensating means changing its action as a function of the thickness determined.
18. Method for supercalendering a material web in an extended nip calender having a shoe roll which has a revolving shell and a pressure shoe, and an opposing roll which, together with the shoe roll, forms an extended nip, the pressure shoe being displaced in the direction of the opposing roll and the shell being deformed radially outwards out of a circular shape in a working region, characterized in that shell thinning is compensated for.

Images