Press of a paper machine for thin papers

Details Press of a paper machine for thin papers Press of a paper machine for thin papers

1995-01-30

1997-09-23

Hastings, Karen M.

Paper making and fiber liberation

Apparatus

Running or indefinite length product forming and/or treating...

1623583, 1623603, D21F 304

Patent

active

056700237

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a press section of a paper machine for thin papers, particularly one-sided papers or tissue, and in particular to the removal of the web from the last press unit.
Press sections in paper machines in which the water is discharged to one side of the web have been known for a long time. By way of example, reference is had to the journal "Wochenblatt fur Papierfabrikation 5 (1988)", pages 173 et seq. In that case, the web is removed from the smooth roll following the press nip in a free path in order, for instance, to be fed to a smoothing press, a drying cylinder or a multi-unit drying section.
The disadvantage of these embodiments is that special transfer elements for the web are necessary and that the frequency of web tears is relatively great.
Reference is furthermore had to German Patent Application DE 42 24 730 C1, FIG. 8 of which shows the removal of the web of paper from a roll by a press hose of a long-nip press 13.3. Here there is the disadvantage that the life of the press hose is greatly reduced by contact with the hot surface of the following cylinder 20.


SUMMARY OF THE INVENTION

The object of the present invention is to provide a press section with which such transfer elements can be dispensed with, so that the frequency of the tearing of the web of paper is reduced, and at the same time, there is a saving in cost due to a reduction in the operating expenses.
This object is achieved by the features set forth in the following. In the press section of a paper machine, a first press nip is defined between a smooth surfaced, tubular roll and a felted press roll. A following heatable roll has the web transferred to it from the smooth surfaced roll.
In accordance with the invention, it is proposed by the inventors that, instead of a free path, the web is removed by a tubular press roll, particularly a roll having a rigid shell, from the smooth roll of the last press and is fed to the next machine group, for instance the smoothing unit, smoothing press, drying cylinder, or a multi-unit drying section.
In this way, the following advantages are obtained: the paper is transferred from the tubular press roll does not come into contact with a felt or with a "press hose" or "press shell". felt.
In accordance with the concept of the invention, the following possible embodiments result for a press section for preferably thin papers, particularly also tissue papers:
First, a press nip is provided which is formed by a rotating, smooth paper-contacting surface and a felted press roll. The smooth surface transfers the web of paper, avoiding a free paper path, i.e. an open draw, after the press nip to a heatable roll, the smooth surface is developed as the outer surface of a tubular roll having a dimensionally stiff roll sleeve.
It is advantageous for the felted press roll to be a long-nip or shoe press roll.
Furthermore, it is particularly advantageous if, with a press section developed in this manner, the smooth tubular roll forms, prior to the press nip, another prior press nip (pre-press nip) with a further felted press roll. In this connection it is also advantageous if separate, endless loop felts are provided for the two press nips. However, a single felt for both press nips may also be advantageous, depending on the operating conditions. It may be particularly advantageous with respect to the drying power if the further felted press roll is also a shoe-press or long-nip press roll.
It may also be advantageous for the further felted press roll to be a suction roll having a suction zone which lies predominantly in front of the pre-press nip. In the embodiments shown, it may also be advantageous to develop the smooth tubular roll as a sag-adjustment roll in order to obtain the uniform linear pressures and in this way improve the transfer of the web. Another advantageous development of the press section is obtained if the heatable roll is a non-felted tubular roll which conducts the web and transfers the web to a drying cylinder, a free paper path

REFERENCES:
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patent: 5120400 (1992-06-01), Laapotti
patent: 5308450 (1994-05-01), Braun et al.
patent: 5368697 (1994-11-01), Steiner et al.
patent: 5500092 (1996-03-01), Schiel
patent: 5501775 (1996-03-01), Kotitschke et al.

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