Press and method of controlling the press

Abstract

A press for processing a web and a method of controlling a press. The press includes at least one nip having a first press roll and a second press roll. A first belt runs through the at least one nip. A second belt runs through the at least one nip. A sandwich stretch is formed by the first and second belts and is arranged after the at least one nip. A first mechanism is provided for driving the first belt. A second mechanism is provided for driving the second belt. The method includes driving the first belt at a first speed, and driving the second belt at a second speed, wherein the first speed is substantially the same as the second speed at least in a region of the sandwich stretch.

Description

[0001] The present application claims priority under 35 U.S.C. .sctn.119 of German Patent Application No. 101 02 535.1, filed on Jan. 19, 2001, the disclosure of which is expressly incorporated by reference herein in its entirety.[0002] 1. Field of the Invention[0003] The invention relates to a press for processing a paper, cardboard, tissue or another fibrous material web with at least one nip formed by two press rolls, through which a belt runs next to the fibrous material web on each side, in which the fibrous material web is guided after the nip over a sandwich stretch jointly by both belts and the relevant control processes.[0004] 2. Discussion of Background Information[0005] Such presses for dewatering fibrous material webs have been known for a long time and, particularly in an embodiment with long nips, are linked to a high dewatering capacity. The sandwich stretch thereby also guarantees safe guidance of the fibrous material web even at high web speeds.[0006] The drive capa...

AI Technical Summary

Benefits of technology

[0009] According to the invention both belts outside the nip are assigned at least one belt drive each. By driving both belts, the tension and speed differences between the belts are considerably reduced, which reduces the strain on the fibrous material web and improves its adhesive behavior with regard to the belts.

[0013] Afterwards the belt that guides the fibrous material web alone in both cases can transfer the fibrous material web to a take-up element preferably in the form of another belt. It is advantageous here if the belt is guided over a driven guide roll after transferring the fibrous material web.

[0016] In order to reduce the risk of breaking regarding the fibrous material web and to improve the adhesion to the belt that guides it alone, the belt that guides the fibrous material web alone after the sandwich stretch should have a higher speed after the nip than before the nip and / or the belt that guides the fibrous material web alone after the sandwich stretch should feature a higher tensile stress in the web travel direction after the nip than before the nip. It is advantageous here if the speed of the belt after the nip is up to approximately 4% higher, preferably between approximately 0.1 and approximately 0.3% higher, than before the nip and / or the pull of the belt is up to approximately 6 KN / m higher, preferably between approximately 0.2 and approximately 1.2 KN / m higher, than before the nip.

[0018] In connection with this, but also independent of it, the guide roll in the area of guiding away the other belt should be driven at a slower speed than the guide roll arranged after the transfer of the fibrous material web. This increases the tension of the guiding belt in the section between the guide rolls. As a result the adhesion of the fibrous material web to the belt is improved, so that it counteracts a tugging at the edges while the other belt is guided away.

[0027] The method may further comprise controlling each of the first and second belt drives. The method may further comprise controlling at least one of a speed and a tension of at least one of the first and second belts. The method may further comprise controlling at least one of a speed and a tension of the first and second belts by controlling the first and second belt drives. The method may further comprise controlling at least one of a speed and a tension of the first and second belts by controlling the first and second belt drives, whereby the first and second belt drives are controlled in a manner which minimizes a strain on the web. The method may further comprise transferring the web to a pick-up element after the second belt drive. The method may further comprise guiding away the first belt after the sandwich stretch. The method may further comprise driving the second belt at a greater speed than the first belt after the second belt transfers the web to the pick-up element.

Problems solved by technology

Strains on the fibrous material web occur in the sandwich stretch as a result of differing speeds of the belts, that can lead as far as damage to the fibrous material web.

Furthermore, differences in the tension of the two belts also result in differing adhesive behavior between the fibrous material web and the belts and a shearing load on the web, which renders difficult the secure guidance of the fibrous material web after the sandwich stretch and impairs quality.

As a result, creases and crushing, for instance, can occur.

The differences in tension of the belts have a particularly adverse effect in the sandwich area after a shoe press, as a result of the long, intensive press time.

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