WO2006117260A1

WO2006117260A1 - Long nip press

Info

Publication number: WO2006117260A1
Application number: PCT/EP2006/060719
Authority: WO
Inventors: Andreas Meschenmoser; Thomas Augscheller; Peter Mirsberger; Andreas SCHÜTTE
Original assignee: Voith Patent Gmbh
Priority date: 2005-04-30
Filing date: 2006-03-15
Publication date: 2006-11-09
Also published as: ATE416273T1; JP2008540851A; DE502006002264D1; JP4935809B2; EP1880055A1; DE102005020218A1; EP1880055B1

Abstract

The invention relates to a long nip press for dewatering a web of paper, cardboard, tissue or other fibrous material (1) in a machine for producing and/or upgrading the same. Said press comprises a press roll (4) with a flexible roll sleeve (9) and a press element (6) with a concave press surface which forces the roll sleeve (9) towards a cylindrical mating roll (5) for producing a long press nip, the diameter of the press roll (4) being less than 1 m. The aim of the invention is to reduce the load on the flexible roll sleeve (9). For this purpose, the diameter of the mating roll (5) is less than 1.4 m and the ratio between the length (L) of the press surface in the web transport direction (11) and the diameter of the press roll (4) is more than 0.08 and/or the press roll (4) projects over the mating roll (5) by at least 25 cm each at the roll end.

Description

Long nip press

The invention relates to an extended-nip press for dewatering a paper, board, tissue or another fibrous web in a machine for producing and / or finishing the same, consisting of a press roll with a flexible roll shell and a pressing element with a concave pressing surface which the roll shell for Forming an extended press nip presses to a cylindrical counter roll, wherein the diameter of the press roll is less than 1 m.

Such presses are often used in conversions and can replace conventional presses because of the small space required.

Long-nip presses allow intensive and yet gentle dewatering of the fibrous web due to the longer dwell time in the press nip.

However, this is counteracted by the large load on the flexible roll shell in the press nip area as a result of deformation, in particular with relatively small roll diameters. In addition, the pressing pulse and thus the drainage performance is limited.

The object of the invention is therefore to reduce the burden of the flexible roll shell with the smallest possible space requirement of the press arrangement.

According to the invention this object is achieved in that the diameter of the counter roll is less than 1, 4 m and the ratio between the length of the pressing surface in the web running direction and the diameter of the press roll is greater than 0.08 and / or the press roll counter-roll at the end of each roll at least 25 cm surmounted.

The diameter of the counter roll should not exceed a diameter of 1, 4 m because of the space required and the weight. He should, however - 2 -

be large enough that a sufficient load capacity without excessive deflection of the same is guaranteed.

The still possible, relatively large diameter of the counter roll but also has a reduced curvature of the pressing surface and thus a lower load on the flexible roll shell result. This makes it possible to increase the pressing surface of the pressing elements so far that the realization of higher pressing pulses is possible without making a larger diameter of the roll shell required.

In the transition region from the concave pressing surface to the cylindrical clamping of the roll mantle at the ends of the press roll, the flexible roll mantle is subjected to deformation due to deformation. This load is reduced considerably by the relatively strong projection of the roll shell.

Due to the longer pressing surface and the resulting longer residence time of the fibrous web in the press nip, a volume-saving dewatering of the fibrous web is ensured even at higher press pulses.

The load on the roll shell of the press roll as a result of the deformation in the press nip area is further reduced if the diameter of the press roll is smaller than the diameter of the counter roll, as a result results in a lower convex curvature of the press nip in the web running direction.

In order to make optimal use of the resulting possibilities in relation to the effort, the average pressing pressure in the press nip should be greater than 2 MPa, preferably greater than 3 MPa and in particular greater than 4 MPa.

Depending on the conditions of use, in particular the requirements imposed by the fibrous web to be dewatered, it has proved to be advantageous if the pressing surface in the web running direction has a length of more than 80 mm, preferably more than 100 mm. - 3 -

For a realization of particularly long pressing surfaces and thus also long residence times, it may be advantageous, especially at high machine speeds and / or for volume conservation, if the pressing surface in the web running direction has a length of more than 140 mm, preferably more than 160 mm.

Because of the high average compacting pressures and the small roll diameters, the advantages of the invention are obtained especially in presses in which the width of the press roll is less than 7.5 m, preferably less than 6.8 m and in particular less than 5.5 m ,

The reduced load on the roll mantle results in the press roll, i. her roll mantle only only at most 1, 4 m, preferably at most 1 m wider than the counter roll, i. whose lateral surface must be.

However, in order to limit the load on the roll mantle, the roll mantle of the press roll should project axially beyond the mantle surface of the mating roll by at least 300 mm, preferably by at least 350 mm.

The invention will be explained in more detail with reference to an exemplary embodiment. In the attached drawing shows:

1 shows a schematic cross section through an extended-nip press, FIG. 2 shows a side view of the extended nip press, and FIG. 3 shows a representation of the pressure-pressure profile in the extended nip.

According to FIG. 1, the extended press nip for dewatering a fibrous web 1, in particular a paper web in a paper machine, is formed by a cylindrical counter-roller 5 and a press roller 4 arranged above it. The roller axles are mounted on both sides in a roller frame 10.

The fibrous web 1 passes through the press nip here by way of example together with a respective dewatering belt 2, 3 in the form of a press felt on both sides. These - A -

Dewatering belts 2, 3 take up a large part of the water pressed in the press nip from the fibrous web 1 and transport it out of the press nip.

To form an extended press nip, the press roll 4 has a flexible roll shell 9 made of fiber-reinforced plastic, which is pressed by a hydraulic pressing element 6 with a concave pressing surface to the counter roll 5.

Here, the pressing member 6 is formed as an axially extending press shoe.

Because of the long press nip and the associated longer residence time of the fibrous web 1 in the press nip an intensive, yet gentle drainage is possible even at high machine speeds.

While the diameter of the press roll is here by way of example 0.8 m, the counter roll 5 has a diameter of 1 m.

The pressing surface of the pressing element 6 has in the web running direction 11 has a length L of about 160 mm, so that the ratio between this length L and the diameter of the press roll 4 is 0.2.

The thus-dimensioned extended-nip press is a very compact press unit and is therefore ideal for the replacement of conventional press units with a short press nip.

Because of the larger diameter of the counter roll 5 relatively long press shoes can be used without making large press rolls 4 required.

This in turn makes it possible to generate larger pressing pulses, in which case the average pressing pressure p in the press nip is greater than 4 MPa. - 5 -

As can be seen in FIG. 1, the axis of rotation 8 of the roll mantle 9 of the press roll 4 is offset by an amount a against the web running direction 11 to the press plane 7 passing through the supports of the press roll 4 and the mating roll 5.

This displacement of the pressing surface leads to an asymmetric pressure pressure curve.

According to Figure 3, the pressing pressure at the inlet of the press nip should gradually rise to a maximum and then drop suddenly from there to the outlet.

The width of the press roll 4 is about 6.5 m, which has a low deflection of the backing roll 5 result.

Since the ends of the flexible roll mantle 9 of the press roll 4 are supported by cylindrical side windows 12, the roll mantle 9 requires a transition region from the concave shape of the press nip to the circular shape of the side window 12 shown in FIG.

This transition is also referred to as guy length h, b and corresponds to the length by which the roll shell 9 of the press roll 4 projects axially beyond the mantle surface of the counter roll 5.

This guy length li, I ₂ can be the same or different lengths.

Here, the press roll 4 projects beyond the counter roll 5 on both sides by the same length U, I ₂ of approximately 30 cm, so that the press roll 4 is 0.6 m longer than the counter roll 5.

Claims

- 6 patent claims

1. An extended-nip press for dewatering a paper, board, tissue or another fibrous web (1) in a machine for producing and / or finishing the same, comprising a press roll (4) with a flexible roll shell (9) and a press element ( 6) with concave pressing surface, which presses the roll shell (9) to form an extended press nip to a cylindrical counter roll (5), wherein the diameter of the

Press roll (4) is less than 1 m, characterized in that the diameter of the counter roll (5) is less than 1, 4 m and the ratio between the length (L) of the pressing surface in the web running direction (11) and the diameter of the press roll (4) greater than 0.08 and / or the press roll (4) projects beyond the counter roll (5) at the end of each roll at least 25 cm.

2. extended nip press according to claim 1, characterized in that the diameter of the press roll (4) is smaller than the diameter of the counter roll (5).

3. extended-nip press according to claim 1 or 2, characterized in that the average pressing pressure p in the press nip is greater than 2 MPa, preferably greater than 3 MPa and in particular greater than 4 MPa.

4. extended nip press according to one of the preceding claims, characterized in that the pressing surface in the web running direction (11) has a length (L) of more than 80 mm, preferably more than 100 mm.

5. extended nip press according to one of the preceding claims, characterized in that - 7 -

the pressing surface in the web running direction (11) has a length (L) of more than 140 mm, preferably more than 160 mm.

6. extended-nip press according to one of the preceding claims, characterized in that the width of the press roll (4) is less than 7.5 m, preferably less than 6.8 m and in particular less than 5.5 m.

7. extended-nip press according to one of the preceding claims, characterized in that the press roller (4) at most 1, 4 m, preferably at most 1 m wider than the counter-roller (5).

8. extended nip press according to claim 7, characterized in that the press roller (4) projects beyond the counter roller (5) at the end of each roll at least at least 30 cm, preferably at least 35 cm.