WO2007141377A1

WO2007141377A1 - Treatment apparatus for treating a coated or uncoated fibrous web

Info

Publication number: WO2007141377A1
Application number: PCT/FI2007/050260
Authority: WO
Inventors: Aaron Mannio; Markku Kirvesmäki; Kari Hasanen; Mika Viljanmaa; Teemu Saarikoski; Jani Hakola
Original assignee: Metso Paper, Inc.
Priority date: 2006-06-06
Filing date: 2007-05-09
Publication date: 2007-12-13
Also published as: FI120408B; FI20065384A; FI20065384A0

Abstract

The invention relates to a treatment apparatus (1) for treating a coated or uncoated fibrous web, comprising a belt (2) adapted to circle around guide elements (3), outside said belt being disposed at least one backing element (5) constituting a contact surface with the belt in such a way that the belt (2) and the backing element (5) establish therebetween a web treatment zone for passing the web to be treated therethrough. At least one section between two successive guide elements (3) in the belt running direction is provided with a belt tension roll (4) internal and/or external of the belt circle, which enables compensating for variation in a lateral and/or longitudinal tension profile of the belt.

Description

Treatment apparatus for treating a coated or uncoated fibrous web

The present invention relates to a treatment apparatus for treating a coated or uncoated fibrous web, comprising a belt adapted to circle around guide elements, outside said belt being disposed at least one backing element constituting a contact surface with the belt in such a way that the belt and the backing element establish therebetween a web treatment zone for passing the web to be treated therethrough, in which apparatus at least one section between two successive guide elements in the belt running direction is provided with a belt tension roll internal and/or external of the belt circle, which enables compensating for variation in a lateral and/or longitudinal tension profile of the belt.

One problem in a fibrous web treatment apparatus, provided with a belt circle, is the fact that a tension profile of the belt in a lateral direction of the belt becomes ever steeper as the belt becomes wider, as depicted in figs. 1-3. In figs. 1-3, the determination of a belt tension profile has been conducted in a treatment apparatus in which the thermo roll has a diameter of 1350 mm and the guide rolls have a diameter of 1050 mm, the belt width being 4000 mm, 6000 mm and 9000 mm, respectively. In view of equalizing the belt tension profile, one alternative that has been contemplated is increasing the diameter of guide rolls, figs. 4 and 5 showing that increasing the guide roll diameter to measure 1600 mm enables a correction of the belt tension profile in a 6000 mm wide belt to equal the tension profile of a 4000 mm wide belt that has a smaller guide roll diameter of 1050 mm. Respectively, in the case of a 9000 mm wide belt, the guide roll diameter should be increased to measure 2650 mm in order to reach a tension profile that would match that of a 4000 mm wide belt using a guide roll whose diameter is 1050 mm. Another problem is soiling of the belt.

Accordingly, an objective of the present invention is to provide a relatively simple solution that enables equalizing a tension profile without increasing the diameter of guide rolls and enables effective cleaning of the belt surface.

In order to accomplish this objective, a treatment apparatus of the invention is characterized in that the belt tension roll has its interior in communication with a vacuum source or a source of pressure fluid, and that the roll shell is provided with holes for applying thereby the vacuum or pressure fluid to the belt surface for vacuuming and/or removing dirt particles from the belt surface.

The invention will now be described more closely with reference to the accompanying drawings, in which:

Figs. 1-5 depict belt tension profiles with various belt widths and guide roll diameters,

fig. 6 shows one solution of the invention, and

fig. 7 shows a belt circle cleaning device useful in connection with a treatment apparatus of the invention.

Fig. 6 shows schematically an arrangement according to the invention, wherein a treatment apparatus 1 consists of a belt 2, which is adapted to circle around guide rolls 3 and which can be a metal belt or metal reinforced belt or also a non-rnetallic belt. Outside the belt circle is disposed a thermo roll 5, the treatment zone for a fibrous web to be treated in the treatment apparatus being established in a contact area between the belt 2 and the thermo roll 5. In the embodiment of fig. 6, there is further shown at reference numeral 6 a press roll internal of the belt circle, which enables applying a region of higher pressure to the fibrous web proceeding through the treatment zone. Reference numeral 4 represents belt tension rolls included in the arrangement of the invention, which in the illustrated embodiment are located in each section between two guide elements 3 outside the belt circle, and further in the illustrated embodiment, belt tension rolls are also deployed inside the belt circle in sections between the extra loading roll 6 and the guide rolls 3 on either side thereof. The belt tension roll 4 is preferably implemented as a spreader roll, which consists of a non-rotatably mounted arcuate shaft and a number of shell casings rotatably bearing-mounted on said shaft. The belt tension roll may also be connected to a vacuum source or a source of pressure fluid for cleaning the belt's 2 surface by means of a vacuum action or a blow action applied to the belt surface by way of holes formed in the shell of the belt tension roll 4. Rg. 7 illustrates one separate cleaning device for the belt 2, which is particularly suitable for cleaning a metal belt of miscellaneous dirt particles and metallic dust coming off the metal belt. This cleaning device 20 comprises a pneumatically operated blower, having a compressed air inlet 21 from which the air flows into an annular chamber 22 and thence throttled by way of an annular slot 23 against an end profile 24 of the blower, which deflects the air flow by about 90° and directs it into the blower's blast channel, the flow of high-velocity inlet air by way of the profile effecting a pressure drop which causes a high-volume flow of ambient air 25 into the blast channel and further into an outlet 26 leading it to a filter for the removal of metal particles and other impurities therefrom. Blowers 20 are preferably disposed at intervals of about 500-1000 mm in a cross-belt direction and each of such devices can be controlled individually by means of the pressure of inlet air for providing the most powerful suction wherever there is most dirt.

Claims

1. A treatment apparatus (1) for treating a coated or uncoated fibrous web, comprising a belt (2) adapted to circle around guide elements (3), outside said belt being disposed at least one backing element (5) constituting a contact surface with the belt in such a way that the belt (2) and the backing element (5) establish therebetween a web treatment zone for passing the web to be treated therethrough, in which apparatus at least one section between two successive guide elements (3) in the belt running direction is provided with a belt tension roll (4) internal and/or external of the belt circle, which enables compensating for variation in a lateral and/or longitudinal tension profile of the belt, characterized in that the belt tension roll has its interior in communication with a vacuum source or a source of pressure fluid, and that the roll shell is provided with holes for applying thereby the vacuum or pressure fluid to the belt surface for vacuuming and/or removing dirt particles from the belt surface.

2. A treatment apparatus as set forth in claim 1, characterized in that each section between two successive guide elements (3) is provided with at least one belt tension roll (4).

3. A treatment apparatus as set forth in claim 1 or 2, characterized in that the belt tension roll (4) is implemented as a spreader roll, which consists of a non- rotatably mounted arcuate shaft and a number of shell casings rotatably bearing- mounted on said shaft.

4. A treatment apparatus as set forth in any of the preceding claims, characterized in that the belt (2) comprises a metal belt or a metal reinforced belt.