EP1369527B1 - Calender and method of calendering - Google Patents

Description

The invention relates to a. Calender arrangement with a shoe roll and a counter roll, which form between them a broad nip through which a material web is guided, wherein the shoe roll has a circumferential jacket, which is loadable by means of a pressure shoe towards the counter roll and the position of the pressure shoe is changeable. Furthermore, the invention relates to a method for treating a material web in a nip, which is formed by a shoe roll having a circumferential jacket and a counter-roller, wherein the jacket is loaded by a pressure shoe in the direction of the counter-roller.

The invention will be described below using a paper web as an example of the material web, but without being limited thereto. Also with other material webs, which treated in similar way to be, for example, board webs, occur in the following problems.

A paper web is passed at least once in the course of its production through a nip, which is often formed by two rollers which are pressed against each other. In the nip, the paper web is subjected to an increased pressure. This pressure is used for a compression of the paper web. On the other hand, the pressure has an impact on the design of the surface of the paper web. In addition, when heat is introduced into the nip, for example by heating one of the rolls, the fibers of the paper web are plasticized, which contributes to an improved surface, especially with regard to gloss and / or smoothness properties.

With paper webs running ever faster, in some cases there is not enough time left in the nip to enter the required energy into the paper web. It has therefore recently been used to use so-called Breitnips when satinizing a paper web, in which the paper web is subjected to pressure and optionally temperature. A broad nip is formed by a circumferential jacket, which rests against the counter-roller under the action of a pressure shoe, wherein the paper web is arranged between the jacket and the counter-roller. The jacket lies against a part of the circumference of the counter roll. Accordingly, the jacket must be sufficiently deformable, so that it is approximately concave in the region of the pressure shoe adapted to the counter-roller, while it extends convexly in the remaining area.

The jacket can have different configurations. For one thing, it can be relatively thick and revolve in the manner of a roller. But it can also be designed as a thin band, which is guided over several roles.

In virtually all cases, it is customary to use an elastomeric plastic as the material for the jacket. Such a plastic is flexible and yielding enough so that it can adapt to the shape of the backing roll.

In some cases, it is undesirable for the sheath to come in direct contact with the backing roll. This will be explained with reference to the following example: Such plastics are, however, in general thermally only limited loadable. If you heated the counter-roll, then it must quite surface temperatures on the order of 200 to 300 ° C assume. Such temperatures are required in many cases in order to register a sufficient amount of heat in the paper web can. Such a high temperature would damage the jacket when it rests directly against the counter roll. In contrast, areas in which the jacket is separated from the counter roll by the material web are not critical. In this area, the material web acts as a sufficient insulator.

Therefore, various proposals have been made to defuse the problem. To show DE 299 02 451 U1 and DE 299 02 436 U1 a procedure in which the material web is chosen wider than the investment width of the shell on the counter roll. However, this approach has the disadvantage that the web is uncalendered Having areas that need to be treated either before or after, so that the web is even wound up.

Out DE 43 44 165 A1 A method for smoothing a fibrous web in an extended nip and an apparatus for carrying out the method is described. The smoothing gap is designed as a broad nip, which has a shoe roll and a counter-roller. The shoe roll is provided with a circumferential jacket, which is loadable by means of a pressure shoe in the direction of the counter roll. The position of the pressure shoe is variable, both parallel to the axis of the backing roll, as well as orthogonal thereto.

Out WO 01/75225 A1 For example, a method is known for preventing the elastic band forming the circumferential jacket of a shoe roll from being damaged. Furthermore, a calender is disclosed using this method. The counter roll of the shoe roll is heated. One suggestion is to abrade the area of the band that overhangs the web. In this case, a reduction in the thickness of, for example, 2 mm is sufficient. This prevents direct contact of the strip with the heated counter-roll. The tape is not damaged by the heat. A second proposal is to displace the belt so that the first side of the belt is aligned with a first side of the web. Then the pressure shoe is aligned so that it is aligned with the second side of the web. The second end of the band, which projects beyond the material web, is not acted upon by the pressure shoe so that it does not come into contact with the counter-roller.

WO 01/51705 A1 describes another embodiment. Here, the pressure shoe is bevelled at its two end faces. By changing the position of the pressure shoe relative to the backing roll in the direction in which the material web passes through the nip, can be changed within certain limits, the width over which the shell is pressed against the mating roll. However, here are the possibilities for change relatively small.

The invention has for its object to prevent a system of the jacket on the counter roll.

This object is achieved in a calender arrangement of the type mentioned above in that the pressure shoe is parallel to the axis of the counter roll, that is, in the axial direction, displaced into a position in which it is only partially in overlap with the counter roll.

With this embodiment, it is possible to change the width of the zone in which the mantle rests against the mating roll in relatively wide areas. If the pressure shoe is moved beyond the counter roller, then he can press the jacket only in the area against the counter roll, in which he is in overlap with the counter roll. The length of the wide nip relative to the axial direction of the counter-roller is thus determined by the length of the overlap. Outside the pressure shoe, there is then no contact between the jacket and the counter roll. From the end of the pressure shoe, which is opposite the counter roll, the jacket can increasingly move away from the counter roll. This gap is sufficient to sufficiently reduce a negative thermal influence of the mantle by the mating roll. At the other end of the jacket is indeed supported by the pressure shoe. But there is no counter-roller available, which could negatively affect the coat. The term "counter roll" is to be understood here in general. In most cases, the counter roll is actually formed by a cylindrical body. However, the "counter roll" can also be designed in other ways as an abutment for the jacket, for example as a belt or sheath.

Preferably, the counter roll is heated. If one introduces heat into the broad nip via the counter-roller, then one can heat the material web, which likewise has a positive effect on the treatment of the material web, in particular the surface properties of a paper or board web.

Preferably, the pressure shoe is displaceable within the shell. One can then form the sheath closed, i. also provided on its front side with boundary walls. Accordingly, it is possible to effect lubrication between the pressure shoe and the shell by a lubricating fluid, such as oil, inside the shell.

Preferably, the jacket and the counter roll are arranged stationary relative to each other. This is simplified the construction. So you do not have to move the counter roll relative to the jacket or the jacket against the counter roll. It is sufficient if the pressure shoe is moved to adjust the effective axial length of the wide nip.

Preferably, the wide nip is preceded by a web guiding device, with which an offset of the material web is adjustable parallel to the axis of the counter-roller. With this web guide it is now possible to guide the web exactly where the wide nip can work, ie in the overlap area between the mating roll and the pressure shoe. This is possible regardless of whether the material web of the calender arrangement tapers in the correct position. If the material web would not yet reach the correct position, the web guiding device provides a remedy.

Preferably, the pressure shoe has a drive relative to a carrier which is coupled to a web edge sensor. By the drive, it is initially possible to control the displacement of the pressure shoe against the counter roll from the outside, ie there is no intervention of a technician required. On the other hand, a certain degree of automation can be achieved with the aid of the drive and the associated web edge sensor. The drive can move the pressure shoe so that the one end of the pressure shoe is in register with the one web edge and the other web edge terminates with the end of the counter roll. Of course you will have to make certain surcharges or deductions here, because the pressure effect of the shell on the web under certain circumstances may also extend slightly beyond the axial length of the pressure shoe.

Preferably, the jacket is provided at its ends with hold-downs. These hold-downs pull the jacket away from the backing roll when it is not supported by the pressure shoe. This makes it possible to quickly generate a sufficient distance between the backing roll and the shell, so that a negative thermal influence of the shell by the counter roll, such as overheating, can not take place. Basically, such a hold-down is required only for the end of the shell, which is to be pulled away from the counter-roll with a corresponding displacement of the pressure shoe. At the other end, there is no longer any counter-roll in front of which the jacket is to be protected. However, it is expedient and advantageous in many cases if one forms the shoe roll based on its axial center substantially symmetrical.

Preferably, the hold-down are formed by circumferential end plates. The face plates close off the interior enclosed by the jacket on the one hand. On the other hand, they are able, if necessary, to transmit a drive power for the rotation of the shell. By a corresponding positioning of the end plates relative to the counter roller can also fulfill the function that the end plates pull the jacket outside of the pressure shoe of the backing roll away.

The object is achieved in a method of the type mentioned above in that the pressure shoe is displaced parallel to the axis of the backing roll, that is, in the axial direction, in a position in which it is only partially in overlap with the backing roll.

As stated above in connection with the calender arrangement, it is possible in this way to change the axial length in which the material web is treated in the extended nip. This is synonymous with the width in which the jacket is pressed against the counter roll. If a correspondingly narrower material web to be treated, then the pressure shoe is further moved out of the overlap with the counter roll, so that the coat is pressed only over a smaller axial length against the counter roll. Now you can adjust the coverage so that in fact a touch could take place only in the area that is defined by the width of the material web. Since in this area, however, the web is passed through the nip, a contact between the backing roll and the shell of the shoe roll is not possible.

In this case, it is preferred that the shell and the counter-roller are held stationary relative to one another. This makes the process relatively easy. You just have to move a single element, namely the pressure shoe of the counter roll.

Preferably, the material web is offset parallel to the axis of the counter roll before entering the broad nip. Even if the material web, for example, runs centrally to the counter roll, it is then possible, the material web to lead so that it enters the coverage area between the pressure shoe and the counter roll. This overlap area results at the axial end of the counter roll.

It is particularly preferred that one offset the web so that the one edge terminates with one edge of a work area of the counter roll and the other edge with the pressure shoe. This facilitates the control. You get defined conditions for guiding the material web. In addition, in this way also defines how far the pressure shoe against the counter roll must be moved out.

Fig. 1

eine schematische Seitenansicht einer Kalanderanordnung,

Fig. 2

eine schematische Vorderansicht der Kalanderanordnung, teilweise im Schnitt, und

Fig. 3

eine Bahnleiteinrichtung.

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

Fig. 1

a schematic side view of a calender arrangement,

Fig. 2

a schematic front view of the calender arrangement, partly in section, and

Fig. 3

a web guide.

Fig. 1 shows a calender 1 with a shoe roll 2, which forms a nip 4 with a counter-roller 3, through which a material web 5, for example a paper web, is guided. The counter roll 3 is heated. The heating can be effected, for example, by passing a heating fluid or a vapor through passages 6 which are guided parallel to the axis, like this known per se. But it is also possible to heat the counter roll 3 from the outside, as shown schematically by an external heater 7.

The shoe roll 2 has a jacket 8 made of a material which is so flexible that it can be pressed by a pressure shoe 9 in the region of the broad nip 4 against the counter roll and there assumes the shape of the counter roll 3. In this area, therefore, the mantle is formed concave, while it is convex in the rest of circulation.

The jacket 8 may be relatively stiff and rotate in the manner of a roller. This case is shown in FIG. But it is also possible to simply form the jacket 8 as a band, which is guided by means of support rollers and is also performed in circulation.

The pressure shoe 9 has a support surface 10 which may be lubricated in a manner not shown, so that the jacket 8 can slide smoothly over the support surface 10. The support surface is formed in the present case so that it is adapted to the curvature of the counter roll 3. However, this is not mandatory.

The pressure shoe 9 is mounted on a support 11, which is arranged in the interior of the jacket 8 and passes through the jacket 8 over the full length. This carrier 11 can also be seen in Fig. 2.

On the carrier 11, a drive 12 is arranged, which is supported on a carrier-fixed base 13. With the help of the drive 12, it is possible, the pressure shoe 9 in Direction of a double arrow 14 to move parallel to the axis 15 of the backing roll 3 and indeed, as shown in Fig. 2, that the pressure shoe 9 is only partially overlapping with a working area 16 of the backing roll 3.

The jacket 8 is provided at its two axial ends with front discs 17, 18, which are rotatably mounted on the carrier 11. The two end disks 17, 18 are arranged so that their outer periphery has a predetermined distance from the counter roll 3. In order for the jacket 8 to come into abutment against the counter roll 3 or against the material web 5 bearing against the counter roll 3, it is necessary for the pressure shoe 9 to raise the jacket 8 correspondingly in this area. Axially outside the pressure shoe 9, the jacket 8 is pulled away from the counter roll 3 by the end disks 17, 18. The end plates 17, 18 thus form hold-down.

In the direction of the web 5 in front of the nip 4 web edge sensors 19, 20 are arranged, which determine the position of the edges of the web 5. The web edge sensors 19, 20 are coupled to the drive 12. Furthermore, the web edge sensors 19, 20 are coupled to a web guiding device 21, which is likewise arranged in front of the broad nip 4. With the aid of the web guiding device 21, it is possible to impart a lateral offset A to the material web 5. The web 5 should be controlled so that its one edge 22 terminates with the axial end of the working area 16 of the counter roll 3. The drive 12 controls under the specification of the web edge sensor 20 for the other web edge 23, the position of the pressure shoe 9 so that this other Web edge 23 terminates with the axial effective limit of the pressure shoe 9. In this way, it is ensured that the jacket 8 is approximated to the counter-roll 3 only in one area, where the material web 5 is located between the counter-roll 3 and the jacket 8. The remaining areas of the jacket 8 are reliably held by the end disks 17, 18 at a distance from the counter-roller 3.

In the area of the left in Fig. 2 web edge 22 of the pressure shoe 9 holds the jacket 8 while at a height which also corresponds to the height in the overlap region between the jacket 8 and the counter roll 3. However, this is without further thermal consequences, because axially outside this web edge 22 (in Fig. 2 left), the counter roll 3 stops, more precisely, tapers, so that a direct thermal influence of the jacket 8 through the hot counter roll 3 can not take place here either ,

The counter roll 3 and the shell 8 of the shoe roll 2 are arranged stationary relative to each other. In an adjustment of the pressure shoe 9 so the mutual local assignment of mating roll 3 and sheath 8 does not change.

The web guiding device has two guide rollers 24, 25, which are arranged on a common frame 26. This frame is rotatable about a pivot point 27 in the direction of the double arrows 28, as shown in Fig. 3, so that the offset A can be adjusted in relatively wide ranges.

Here, the feed of the web 5 should be adjusted so that the one edge 22 terminates with the edge of the working area 16 of the backing roll 3, while the rest of the pressure shoe 9 is adjusted by the drive 12 so that the effect of the pressure shoe 9 over the jacket 8 stops on the web 5 at the other edge 23. This does not necessarily mean that the pressure shoe 9 must end exactly at the web edge 23. In many cases, it will already end a little way before, because due to the inherent rigidity of the shell 8 still a certain pressure on the web 5 will be applied in the region of its edge 23.

The jacket 8 has a greater axial extent than the working area 16 of the counter roll 3. This is necessary so that the pressure shoe 9 can be moved out so far under the mantle 8 under the mating roll 3, that it only partially overlaps with the mating roll 3 stands.

Claims (12)

1. Calender arrangement (1) having a shoe roll (2) and an opposing roll (3), which between them form an extended nip (4), through which a material web (5) is guided, the shoe roll (2) having a revolving shell (8) which, with the aid of a pressing shoe (9), can be loaded in the direction of the opposing roll (3), and the position of the pressing shoe (9) can be varied, characterized in that the pressing shoe (9) can be displaced parallel to the axis (15) of the opposing roll (3), that is to say in the axial direction, into a position in which it only partly overlaps the opposing roll (3).
2. Arrangement according to Claim 1, characterized in that the opposing roll (3) is heated.
3. Arrangement according to Claim 1 or 2, characterized in that the pressing shoe (9) can be displaced within the shell (8).
4. Arrangement according to one of Claims 1 to 3, characterized in that the shell (8) and the opposing roll (3) are arranged in a fixed location relative to each other.
5. Arrangement according to one of Claims 1 to 4, characterized in that the extended nip (4) is preceded by a web guide device (21), with which it is possible to set an offset (A) of the material web (5) parallel to the axis (15) of the opposing roll (3).
6. Arrangement according to one of Claims 1 to 5, characterized in that the pressing shoe (9) has a drive (12) relative to a support (11) which is coupled to a web edge sensor (19, 20).
7. Arrangement according to one of Claims 1 to 6, characterized in that the shell (8) is provided with hold-downs (17, 18) at its ends.
8. Arrangement according to Claim 7, characterized in that the hold-downs (17, 18) are formed by revolving end discs.
9. Method for treating a material web (5) in an extended nip (4), which is formed by a shoe roll (2) having a revolving shell (8) and an opposing roll (3), the shell (8) being loaded in the direction of the opposing roll (3) by a pressing shoe (9), characterized in that the pressing shoe (9) can be displaced parallel to the axis of the opposing roll (3), that is to say in the axial direction, into a position in which it only partly overlaps the opposing roll (3).
10. Method according to Claim 9, characterized in that the shell (8) and the opposing roll (3) are kept in a fixed location relative to each other.
11. Method according to Claim 9 or 10, characterized in that, before entering the extended nip (4) the material web (5) is offset parallel to the axis of the opposing roll (3).
12. Method according to Claim 11, characterized in that the material web (5) is offset in such a way that one edge ends with an edge of a working region of the opposing roll (3), and the other edge ends with the pressing shoe (9).

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