EP1636417B1

EP1636417B1 - Belt structure

Info

Publication number: EP1636417B1
Application number: EP04728363A
Authority: EP
Inventors: Maria Lepola
Original assignee: Metso Paper Oy
Current assignee: Valmet Technologies Oy
Priority date: 2003-05-30
Filing date: 2004-04-20
Publication date: 2007-11-28
Anticipated expiration: 2024-04-20
Also published as: EP1636417A1; FI113881B; AT502000B1; AT502000A1; FI20030815A0; WO2004106628A1

Abstract

The invention relates to a belt for a processing apparatus intended for treating a fiber web. The processing apparatus comprises a belt run (2) adapted to travel around at least one guide element (3). Outside the belt run is provided at least one counter-element (5) creating a contact surface with the belt, such that between the belt (2) and the counter-element (5) is established a web processing zone (N), the web to be treated being passed therethrough. The belt of the belt run comprises a layered structure, including a metallic outer layer (10), intended for contact with a fiber web (W) to be treated, and at least one backing layer (11) bonded to the metal layer’s inner surface.

Description

The present invention relates to a belt for a processing apparatus intended for treating a fiber web, said processing apparatus comprising a belt run adapted to travel around at least one guide element, outside said belt run being provided at least one counter-element creating a contact surface with the belt, such that between the belt and the counter-element is established a web processing zone, the web to be treated being passed therethrough. The invention further relates to a method for processing or treating a fiber web.
US patent No. 6203307 discloses an elongated continuous belt that may be used in a hot soft nip calender. The belt disclosed in that document may include a substrate formed from, for example, Kevlar (DuPont). A smooth outer layer is provided on the surface of the bale that will contact the paper. The smooth outer layer may comprise metallic materials.
EP-A-1314819 discloses a belt for use in a calender. The belt disclosed in that document may comprise two layers of which one is a metal layer and the other layer that is heat insulating.
WO-A-02/29159 discloses a steel belt that has end sections made of a resilient material such as polymer, rubber or silicone.
It is an object of the present invention to provide an improved belt solution, contributing to treatment performance and web runnability. In order to fulfil this object, a belt of the invention is characterized in that the belt comprises a layered structure, including a metallic outer layer, intended for contact with a fiber web to be treated, and at least one backing layer bonded to the metal layer's inner surface, the metal layer having a thickness in the range of about 0.1-0.3 mm. A method of the invention is in turn characterized by what is set forth in the characterizing clause of claim 6.
Advantages gained by making a single- or multi-component backing layer flexible and/or compressible include e.g. the fact that pressure is transmitted evenly in the nip and vibration of the belt can be dampened, hence improving the stability and, consequently, runnability of the belt. The layer-structured belt is also beneficial in terms of reducing noise caused by scuffing between belts and rolls.
By using a backing layer, it is possible to make the metal layer thinner than when using a purely metallic belt, and this enables enhancing the process regarding the use of a heated metal belt as heat Is able to transfer rapidly from the belt to a presently processed web which has its surface portion converting to a plastic state and then cooling rapidly, the polymers contained in the web converting from a plastic state to a glassy state and the conversion remaining permanent. Heating of the belt's metal layer and a rapid transfer of heat therefrom to the web can be enhanced by making the backing layer from a heat insulating or poorly conducting material. In this case, the heat transfers from the metal layer only towards the web and simultaneously the metal layer cools quickly. Within the web, the heat transfers from the surface layer inwards, whereby the surface layer cools rapidly and this is promoted by the cooled metal belt over the final section of a processing zone. In addition, a thinner metal belt improves bending strength, whereby the diameter of guide rolls can be reduced. In the case of a purely metallic belt, the currently employed thickness Is typically 0,6 mm, while with the inventive belt, provided with a backing layer, the thickness of a metal layer can be less than about 0,3 mm, and preferably it can be less than about 0,1 mm.
The invention will now be described in more detail with reference to the accompanying drawings, in which:

fig. 1: shows schematically one processing apparatus applying a belt of the invention,
fig. 2: shows one embodiment of the belt structure in a schematic partial view, and
fig. 3: shows a second embodiment of the belt structure in an enlarged sectional view.

Fig. 1 shows one processing apparatus applying a belt solution of the invention and designed as a belt calender, comprising a calendering belt 2 which travels around guide rolls 3, at least some of said guide rolls being displaceable for adjusting the belt's 2 tightness and/or the processing zone length as desired. The calendering belt 2 travels around a roll 5 disposed on its outside, establishing a calendering zone between the belt 2 and the roll 5. A material web W to be calendered passes through the calendering zone, being thus exposed to a desired pressure impulse and heat effect as a function of time. Depicted with a dash-and-dot line 9 in fig. 1 is the shape of a pressure effect, when inside the calendering belt 2 is provided a nip roll 4 which functions as a press element and presses the belt against the roll 5 to establish a higher-pressure nip zone within the calendering zone. On the other hand, a dash line 8 depicts the shape of a pressure effect whenever the contact pressure existing in the calendering zone is established solely by means of the belt's 2 tightness as the nip roll 4 is out of contact with the belt 2 (or when there is no nip roll 4 installed inside the belt 2). The roll 5, and likewise the nip roll 4, may or may not be a deflection-compensated roll and can be selected from a group consisting of: a flexible surface roll, such as a polymer-coated roll, a rubber-coated roll or an elastomer-surface roll, a shoe roll, a thermal roll, a metal roll, a fiber roll, and a composite roll. Instead of the roll 4, the press element may comprise some other profilable or fixed-profile press element, which may further consist of several elements successive in a cross-machine direction. The roll-shaped press element 4 may also consist of several elements successive in a cross-machine direction. The press element 4 may have a surface which is designed to be continuous or discontinuous. The press element 4 can also be adapted to be displaceable for varying the processing zone length and/or the belt's tightness.
According to fig. 2, the belt 2 comprises a metallic outer layer 10, intended for contact with a presently treated fiber web W, and a backing layer 11 bonded to the metal layer's inner surface and preferably selected from a group consisting of: rubber, polyurethane, a composite material, felt, aramid (e.g. kevlar®), or combinations thereof. Be selecting the backing layer structure to be flexible and/or compressible, a higher pressure zone established by the nip roll 4 can be widened as compared to what is achieved with a substantially non-compressible belt. In addition, the backing layer dampens vibrations and thus improves the belt's controllability.
Fig. 3 shows a second exemplary embodiment of the belt 2, in which to the backing layer's 11 inner surface is bonded a second metal-belt layer 12, which is preferably thicker than the outer surface layer 10. The outer surface layer 10 has a thickness which is preferably within the range of about 0,1-0,3 mm and the Inner metal layer 12 can be within the range of about 0,3-1 mm. The backing layer 11 is preferably within the range of about 3-10 mm.
In the processing apparatus of fig. 1, the nip roll 4 comprises a deflection-compensated roll. Reference numeral 6 represents heating elements, such as for example an induction heater, an infrared radiator, a gas burner, or a capacitive heater. The inventive belt solution can be provided with elevated temperatures, for example from higher than about 100°C to higher than about 200°C and even to as high as 400°C, depending on a particular application. An elevated temperature, along with a long application time and an extensive pressure regulation range, yields a good calendering result both at high and low speeds, e.g. at speeds of 100 m/min-4000 m/min.

Claims

A belt for a processing apparatus intended for treating a fiber web, said processing apparatus comprising a belt run (2) adapted to travel around at least one guide element (3), at least one counter-element (5) being provided outside the belt run to create a contact surface with the belt, such that between the belt (2) and the counter-element (5), a web processing zone (N) is established, the web to be treated being passed therethrough, the belt of the belt run comprising a layered structure, including a metallic outer layer (10), intended for contact with a fiber web (W) to be treated, and at least one backing layer (11) bonded to the metal layer's inner surface and made of a flexible and/or compressible material, characterized in that the outermost metal layer (10) has its thickness within the range of about 0.1 - 0.3mm.
A belt as set forth in claim 1, characterized in that there are two or more backing layers bonded to each other and to the metal layer's (10) inner surface for an integral belt structure.
A belt as set forth in claim 1 or 2, characterized in that to the inner backing layer's inner surface is bonded a second metal layer (12).
A belt as set forth in any of claims 1-3, characterized in that the backing layer (11) consists of a heat insulating material.
A belt as set forth in any of the preceding claims, characterized in that the backing layer/layers (11) is/are selected from a group: rubber, polyurethane, a composite material, felt, aramid, or combinations thereof.
A method for treating a fiber web with a processing apparatus, comprising a belt run (2) adapted to travel around at least one guide element (3), outside said belt run being provided at least one counter-element (5) creating a contact surface with the belt, such that between the belt (2) and the counter-element (5) is established a web processing zone (N), the web to be treated being passed therethrough, the method comprising the use of a layer-structured belt in the belt run, which comprises a metallic, relatively thin outer layer (10), intended for contact with a fiber web (W) to be treated, and at least one backing layer (11) of a flexible and/or compressible material bonded to the metal layer's inner surface, the method further comprising heating the metallic, relatively thin outer layer for a rapid transfer of heat to the presently treated web, its surface portion converting to a plastic state and then cooling rapidly, whereby the polymers contained in the web convert from a plastic state to a glassy state and the conversion remains permanent, characterized in that the outermost metal layer (10) has its thickness within the range of about 0.1mm - 0.3mm.