DE10259442B4 - Extended nip calender - Google Patents

Abstract

A papermaking machine has a wide-nip calander (1) with a drum (4) rotating against a lower mantle (8). The mantle moves over a shoe (3) located within an essentially cylindrical support (6). When the mantle (8) is under pressure from the top (4) and lower (6) cylinder, the mantle is partly deforms radially outwards and partly radially inwards. The maximum outwards radial deformation is equal to the maximum inwards deformation. The bottom cylinder peripheral radius is at least as large as that of the deformed drum mantle (2) at the point of maximum deformation (13).

Description

The The invention relates to a broad-nip calender with an unloaded Condition at least partially having a cylindrical shape, circumferential jacket, a counter-roll and a pressure shoe, which presses the jacket against the counter roll and thereby out of the cylindrical shape deformed out, wherein the jacket pressed in the pressed against the backing roll state starting from the cylindrical shape partially radially outward and partially deformed radially inwardly.

One Such calender is from the post-published WO 03/035978 A1 known.

Another wide-nip calender is for example off DE 299 02 451 U1 known.

DE 196 15 654 A1 shows a press arrangement with a counter-roller, which cooperates with a shoe roll. The shoe roll has a circumferential jacket, which is pressed by means of a pressure shoe to the counter roll. The jacket is deformed out of its cylindrical shape. It is also shown a situation in which the jacket is deformed in the pressed against the counter roll state of the cylinder shape starting partially radially outward and partially radially inwardly.

US 2002/00 59 872 A1 shows a shoe press with a coat that with Help of a pressure shoe pressed against a counter roll becomes. If an error occurs that risks causing the sheath with the hot Counter roller comes into contact, then the coat is relatively fast lowered. Within a nip the mantle is concave deformed. Outside the nip it runs convex.

Extended nip calender serve to a fibrous web, such as a paper or Cardboard web, to satin, so with increased pressure and usually also with an elevated Temperature to apply. Unlike calanders, those with two working against each other acting rollers, has the wide-nip calender a longer treatment length. These treatment length is formed by the fact that the Coat over a part of the peripheral surface of Counter roll against the counter roll. This concern is through the pressure shoe causes, which presses the jacket to the counter roll. The coat has in the "resting state", so then if he is unloaded, about the biggest part its axial length a cylindrical shape. From the outside So he is over the entire circumference curved convexly. In the area where the coat by the pressure shoe against the counter roll depressed is, the jacket is deformed concave. In addition, the coat goes through the pressure shoe often also radially outward is deformed. This creates at the axial ends of the shell conical sections, in which one avoids that the coat with the hot Counter roller comes into contact. Such a contact would make the mantle in the Usually made of a plastic material is thermally overstressed and harm it.

The described deformation leads However, to a partially considerable stress on the coat. This stress caused by a permanent deformation of the shell during operation causes to that the Life of such a jacket is limited. The wide-nip calender so must be shut down from time to time to renew the mantle. This increases the proportion of downtime in the operating time.

Of the The invention is based on the object of specifying a broad-nip calender, where the coat as possible little is charged.

These Task is a wide-nip calender of the aforementioned Art solved by the fact that the roll shell completed at its ends in each case with a side window is whose radius is smaller than a radius of the deformed roll shell in the area of the maximum deformation is radially outward.

With this embodiment, the jacket is still deformed as before. But it holds the deformation within limits, in which the total load of the shell is as small as possible. The jacket is deformed outwardly only over part of its circumference radially beyond the cylindrical shape which it occupies in the unloaded state. In another part, it is even deformed radially inwards relative to the cylinder shape in the unloaded state. One can assume overall that the compressive and tensile loads are then distributed so evenly that the burden remains relatively low overall. However, the burden can not be completely eliminated. If it is mentioned that the jacket rests against the counter roll, then this is of course to be understood in the operation so that it rests with the interposition of a web on the counter roll. Direct contact between the jacket and the counter roll should still be avoided as far as possible. Since the roll shell is closed at its end faces in each case with a side plate whose radius is smaller than a radius of the deformed roll shell in the region of maximum deformation radially outward, is in the areas where the roll shell is deformed radially outward, ie in the direction of rotation of the roll shell at the beginning and at the end of the Preßschuhs, ensured that the roll shell is pulled away from the counter roll.

Here Although a certain deformation of the roll shell in the axial Direction to watch. However, this deformation is due to the Dimensioning of side windows limited.

Preferably corresponds to a maximum deformation radially outward of a maximum deformation radially inside. The maximum deformation is the largest distance that the jacket from the cylindrical shape. This largest distance is radially to Outside as big as, as radially inward. This achieves a deformation equilibrium, in which the load of the rotating jacket is relatively low.

With Advantage corresponds in a press section an external differential volume, that between the cylindrical shape and the deformed shell radially outside the cylinder shape is formed, an internal difference volume, the between the cylindrical shape and the deformed shell radially inside the cylindrical shape is formed. The outer and the inner difference volume are natural only theoretical sizes, because the jacket in operation not at the same time a cylindrical shape and a may have deformed shape. The cylindrical shape can be but mathematically imitate without further ado. By the arrangement of the pressure shoe across from the mating roll and other elements which influence the shape of the mantle, for example, supporting disks at the axial ends of the shell, so can the outer differential volume and equalize the internal difference volume. An exact match is not required. Again, this is a measure which is well suited to produce a deformation equilibrium and because with the burden of the roll shell to keep small. If looking at the whole in a sectional view, then the area is between a circular line that simulates the cylindrical shape, and the jacket radially outside the circular line is equal to a corresponding area radially inside the circular line.

Preferably The side window has a radius that is at least as large as a radius of the deformed roll shell in the area of the maximum deformation radially inward. In this area, the roll shell is indeed no longer pulled away from the roller. For this one keeps the deformation of the roll mantle small. Since the contact time of the roll shell with the counter roll only short, is a touch in certain circumstances even allowed.

The Invention will be described below with reference to a preferred embodiment described in more detail in connection with the drawing. Herein show:

1 a schematic cross-section through part of a Breitnip calender and

2 a schematic longitudinal section.

1 schematically shows a wide-nip calender 1 in the neckline with a circumferential coat 2 , which under the effect of a pressure shoe 3 against a counter roll 4 is pressed. The contact shoe 3 has a pressing surface 5 on, the curvature of the counter roll 4 is adapted. However, a different shape is also possible in principle.

In the pressing area 5 usually means are provided for lubrication between the pressure shoe 3 and the coat 2 to cause when the coat 2 under pressure between the pressure shoe 3 and the counter roll 4 is passed. Such means may for example be outlet openings of a hydrostatic lubrication.

The coat 2 has a cylindrical shape in the unloaded state, in the present case by a circular line 6 is shown. It is not necessary that the coat 2 assumes this cylindrical shape over the entire axial length. For example, conical sections may be provided at the axial ends.

If the coat 2 but against the counter roll 4 is pressed to a nip 7 then form the coat 2 deformed out of the cylinder shape. The deformation is now controlled so that the jacket 2 partly from the circle 6 deformed radially outward and partially radially inward.

Since the coat 2 has a certain thickness, the following explanations are given by a center line 8th of the coat 2 made, the dot-dashed in the coat 2 is drawn.

The contact shoe 3 has in the direction of rotation at its two ends rounded projections 9 . 10 while deepening in the middle of its center 11 having. Of course, the projections go 9 . 10 and the depression 11 into each other, for example along a cylindrical surface.

In the area of the projections 9 . 10 becomes the coat 2 opposite the circle 6 deformed outwards. This creates a maximum deformation 12 in the area of the "tip" of the projection 9 (A corresponding deformation also results at the top of the projection 10 ). A deformation radially inward results in the region of the depression 11 and here in the middle. Again, there is a maximum deformation 13 ,

You can now by appropriate dimensioning of the pressure shoe 3 and the parts that make up the coat 2 position, ensure that the maximum deformation 12 radially outward of the maximum deformation 13 radially inward corresponds. This achieves a deformation equilibrium between the deformation radially outward and the deformation radially inward. The total load of the jacket 2 by the deformation in the circumferential direction remains relatively small.

One can also make sure that a difference volume that is radially outside the circular line between the circular line 6 and the coat 2 more precisely the midline 8th of the coat 2 , forms, is about as large as a corresponding difference volume, which is in the area of the depression 11 forms radially within the circular line. With reference to the cross-sectional view of 1 could also be said that the area between the center line 8th and the circle line 6 radially outside the circle 6 are about the same size as radially inside the circle 6 , However, this relation can affect the actual press area of the mantle 2 restrict. At the remaining circumference of the coat 2 , ie outside a section line of the circle line 6 with the center line 8th , it is no longer crucial whether the coat 2 actually takes a cylinder shape again in operation or not. The deformations of the mantle 2 in this area play only a minor role.

1 represents the deformation of the shell in the circumferential direction. This deformation arises practically only in the area where the pressure shoe 3 is arranged, ie in a partial region of the axial length of the shell 2 ,

Further deformation results at the axial ends of the shell 2 like this in 2 is shown. The coat 2 is shown with solid lines in the region of its maximum deformation radially outward and with dashed lines in the region of its maximum deformation radially inward.

The coat 2 is at its axial ends with side windows 14 completed. These side windows 14 have a radius equal to the radius of the mantle 2 in the undeformed state corresponds. In other words, each side window points 14 a radius smaller than a radius of the deformed roll shell 2 in the area of maximum deformation 12 radially outward, but at least as large as a radius of the deformed roll shell 2 in the area of maximum deformation 13 radially inward. In this way it is achieved that the deformation in the axial edge region can also be kept within certain limits.

Claims (4)

Wide nip calender with a non-stressed state at least partially having a cylindrical shape, circumferential mantle, and a pressure shoe that presses the mantle to the mating roll and thereby deformed out of the cylindrical shape, the mantle in the pressed state to the mating roll of the cylindrical shape starting partially radially outward and partially radially inwardly deformed is characterized in that the roll shell ( 2 ) at its end faces each with a side window ( 14 ) whose radius is smaller than a radius of the deformed roll shell ( 2 ) in the area of maximum deformation ( 12 ) is radially outward. Calender according to claim 1, characterized in that a maximum deformation ( 12 ) radially outward of a maximum deformation ( 13 ) corresponds radially inward. Calender according to Claim 1 or 2, characterized in that, in a press section, an external difference volume lying between the cylindrical shape ( 6 ) and the deformed jacket ( 2 ) radially outside the cylindrical shape ( 6 ), corresponds to an internal difference volume that exists between the cylindrical shape ( 6 ) and the deformed jacket ( 2 ) radially inside the cylindrical shape ( 6 ) is formed. Calender according to one of claims 1 to 3, characterized in that the side window ( 14 ) has a radius which is at least as large as a radius of the deformed roll shell (US Pat. 2 ) in the area of maximum deformation ( 13 ) radially inwards.