EP1111127B1 - Pressing arrangement - Google Patents

Abstract

Press section for a machine for producing tissue webs (12) comprises a shoe press unit (16) and a counter-roller (18) forming a nip. The unit has one or more press shoes (20) and a flexible, liquid-impermeable belt (22). The counter-roller has a smooth surface and the web is passed on a felt (24) through the nip where the two are separated. The angle between the tangent ( alpha ) to the counter-roller at the end of the nip and the felt emerging from it is not more than 10 degrees (15, 18, 20), bracketed values being given in order of preference. An Independent claim is included for use of the press section in a machine for producing tissue webs, especially a breast roll former, twin wire former, crescent former or fourdrinier machine, in combination with a through air-drying concept.

Description

The invention relates to a press arrangement of a machine for producing a tissue web having at least one press nip formed between a shoe press unit and a counter roll, wherein the shoe press unit comprises at least one press shoe opposite the counter roll and a flexible, liquid-tight press belt guided thereover, the counter roll has a smooth surface and the tissue web is guided together with the press belt and at least one felt through the press nip and is subsequently separated from the felt and taken through the smooth surface of the backing roll. Such a press assembly may form part or at least substantially the entire press assembly of the respective tissue machine.

At one of the DE 196 54 198 A1 known press arrangement of the type mentioned above with a counter-roll forming drying cylinder runs the tissue web approximately in the direction tangential to the drying cylinder surface from the press nip.

The document US4,889,674 describes a process for the production of dimensionally stable, liquid-impermeable, flexible and elastic press jackets in wide-nip presses of paper machines. Among other things, the method makes it possible to produce elevations and depressions on the paper-contacting side of the press jacket.

In the document US 8,849,156 is a compact press section with a Breitnipp and a smoothing tip, to equalize the asymmetry of the paper web roughness disclosed. The broad nip is formed between a pressing element, which is equipped with a flexible jacket and a press roll with a rigid jacket. This press roll is also the counter element to a smooth roller to form the smoothing tip.

The aim of the invention is to provide a press arrangement of the type mentioned, with a higher dry content of the press nip leaving tissue web is achieved and guaranteed in accordance with a more economical Tissueherstellung.

This object is achieved according to the invention in that the angle between the applied at the end of the press nip to the mating roll tangent and at least one expiring from the press nip felt ≥ 10 °, in particular ≥ 15 °, in particular ≥ 18 ° and preferably ≥ 20 ° ,

Due to this design, a higher dry content of the tissue web is achieved after the press in an economical manner.

In particular, a shoe press roll having a press jacket forming the press belt can be provided as the shoe press unit.

As counter-roll preferably a drying cylinder and in particular a so-called Yankee cylinder is provided.

The surface of the press belt may be blind drilled and / or grooved.

Advantageously, the press belt has an open area "f" of f ≥ 25%.

For an open area of, for example f = 36% of a grooved press belt or press jacket could at a flow angle of the felt of a = 20 °, a dry content increase of 4.5% compared to the dry content can be achieved, which, instead of a shoe press roll, with a conventional Saugpreßwalze is reached.

The press arrangement according to the invention is advantageously usable in tissue machines such as, in particular, a suction breast roll former, twin-wire formers, crescent formers, four-wire former and / or the like and / or in combination with "through-air-drying" concepts.

• In dieser zeigt die einzige Figur eine schematische Teildarstellung einer Pressenanordnung 10 einer Maschine zur Herstellung einer Tissuebahn 12.
• Die Pressenanordnung 10 umfaßt einen in Bahnlaufrichtung L verlängerten Preßspalt 14, der zwischen einer als Schuhpreßwalze 16 vorgesehenen Schuhpreßeinheit und einer als Trockenzylinder 18, beispielsweise Yankee-Zylinder, vorgesehenen Gegenwalze gebildet ist.
• Die Schuhpreßwalze 16 umfaßt einen dem Trockenzylinder 18 gegenüberliegenden Preßschuh 20 und einen über diesen geführten, durch ein flexibles, flüssigkeitsdichtes Preßband gebildeten Preßmantel 22.
• Die Tissuebahn 12 ist zusammen mit dem Preßmantel 22 sowie einem Filz 24 durch den Preßspalt 14 geführt. Im Anschluß an den Preßspalt 14 wird die Tissuebahn 12 vom Filz 24 getrennt und durch die glatte Oberfläche des Trockenzylinders 18 mitgenommen.

The invention is explained in more detail below with reference to an embodiment with reference to the drawing:

• In this, the single figure shows a schematic partial representation of a press arrangement 10 of a machine for producing a tissue web 12.
• The press assembly 10 comprises a lengthened in the web running direction L press nip 14 which is formed between an intended as a shoe press roller 16 Schuhpreßeinheit and as a drying cylinder 18, for example Yankee cylinder, provided counter-roller.
• The shoe press roll 16 comprises a press shoe 20 opposite the drying cylinder 18 and a press jacket 22 guided over it and formed by a flexible, liquid-tight press belt.
• The tissue web 12 is guided together with the Preßmantel 22 and a felt 24 through the press nip 14. Following the press nip 14, the tissue web 12 is separated from the felt 24 and taken through the smooth surface of the drying cylinder 18.

The angle α between the tangent 26 applied to the drying cylinder 18 at the end of the press nip 14 and the felt 24 leaving the press nip 14 is ≥ 20 °.

The surface of the press cover 22 may be blind drilled and / or grooved.

The press jacket 22 may in particular have an open area "f" of f ≥ 25%.

LIST OF REFERENCE NUMBERS

10

Press arrangement

12

tissue web

14

nip

16

shoe press

18

drying cylinders

20

press shoe

22

press jacket

24

felt

26

tangent

L

Web direction

Claims (6)

1. Pressing arrangement (10) for a machine for producing a tissue web (12), having at least one press nip (14) formed between a shoe press unit (16) and a mating roll (18), the shoe press unit (16) comprising at least one press shoe (20) located opposite the mating roll (18) and a flexible, liquid-tight press belt (22) led over the said press shoe (20), the mating roll (18) having a smooth surface and the tissue web (12) being led through the press nip (14) together with the press belt (22) and at least one felt (24) and, following that, being separated from the felt (24) and carried along by the smooth surface of the mating roll (18),
   characterized
   in that the angle (α) between the tangent to the mating roll (18) at the end of the press nip (14) and at least one felt (24) running out of the press nip (14) is ≥ 10°, in particular ≥ 15°, in particular ≥ 18° and preferably ≥20°.
2. Pressing arrangement according to Claim 1, characterized in that the shoe press unit provided is a shoe press roll (16) having a press shell (22) forming the press belt.
3. Pressing arrangement according to Claim 1 or 2, characterized in that the mating roll provided is a drying cylinder (18) and in particular what is known as a Yankee cylinder.
4. Pressing arrangement according to one of the preceding claims, characterized in that the surface of the press belt (22) is blind-drilled and/or grooved.
5. Pressing arrangement according to one of the preceding claims, characterized in that the press belt has an open area "f" of f ≥ 25%.
6. Use of a pressing arrangement according to one of the preceding claims in tissue machines, such as in particular a suction press roll former, twin-wire former, Crescent former, Fourdrinier former and/or the like and/or in combination with "through-air drying" concepts.

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