Presses – Methods – With heating or cooling
Reexamination Certificate
1999-06-23
2001-02-06
Vo, Peter (Department: 3721)
Presses
Methods
With heating or cooling
C100S156000, C100S153000
Reexamination Certificate
active
06182564
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 198 28 156.0, filed on Jun. 24, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for the smoothing of a material web, e.g., a paper or card web. The apparatus include at least one smoothing zone through which the material web is passed.
2. Discussion of Background Information
A calender of the type generally described above is disclosed, e.g., in EP 0 361 402 A1. In this calender, the smoothing zones are respectively formed between a heated chill-cast roll and an endless band formed with a soft or resilient cover. A smoothing process of this type always occurs at a side of a material web that contacts the respective chill-cast roll. Accordingly, a relatively heavy, heated, chill-cast roll, which requires long heat up and cool down times, must be used. Moreover, the chill-cast roll is only capable of being handled with heavy apparatus.
This known calender is relatively expensive and complicated in its construction. Further, when it becomes necessary to exchange these heavy rolls, and subsequently necessary to heat the new rolls, considerable cost arises in this complex exchange. The use of a heated, chill-cast roll with corresponding bearings involves a series of disadvantages which relate, e.g., to its large mass, the long heating up and cooling down times and to the fact that corresponding handling is only possible with heavy apparatus. Thus, it is apparent that the use of rolls is extremely costly. Moreover, at least one complete replacement roll must be kept available. Further, zonal heating is not practicable due to the considerable cost which is associated with the requisite induction segments.
Finally, correspondingly high pressures and high temperatures are necessary for large rolls.
SUMMARY OF THE INVENTION
The present invention provides an apparatus of the type generally discussed above in which the above-noted disadvantages are overcome and which ensures an ideal treatment of the material web and, e.g, an ideal glazing result. Further, the construction of the apparatus is kept as simple as possible so as not to require the heavy heated hard rolls or the like of the prior art.
Accordingly, the present invention provides at least one smoothing zone formed between a deflection adjustment (controlled or compensation) roll having a soft or elastic surface and a heatable endless band of high thermal conductivity having a hard and smooth surface. The heatable endless band is guided, in the region of the smoothing zone, over a support surface arranged within the band loop, and is heated on an inner side or surface on by a heating medium. In this manner, the endless band can not only be heated, but a liquid film can be created which provides a hydrodynamic lubrication between the support surface and the endless band.
A hot gaseous medium, e.g., steam, may be preferably used as the heating medium, and the liquid film, which brings about hydrodynamic lubrication, can be expediently built up or formed by the heating medium condensing on the endless band.
As a result of this arrangement, a substantially simplified construction of a smoothing apparatus is provided without the previously customary, heavy, heated rolls, while providing ideal smoothness and gloss values. That is, ideal glazing results are ensured despite the simpler construction. While the deflection adjustment roll, which does not need to be heated, has a soft or elastic surface (or an elastic jacket or coating), the heated endless band, which is positioned on the other side of the material web, has a hard and smooth surface, so that the desired smoothing process occurs on the side web facing the heated endless band. The soft or resilient surface of the deflection adjustment roll ensures uniform compression. Through the introduction of a hot gaseous medium, e.g., steam, on the inner side of the endless band, which preferably can have a high thermal conductivity, the endless band is not only heated, but, at the same time, heating medium condensing on the inner surface forms hydrodynamic lubrication between the support surface and the endless band. Through the condensate, which is towed or dragged into the lubrication gap, a corresponding liquid film can be built up. Thus, in accordance with the features of the present invention, the gaseous medium or steam on the inner side of the endless band has a double function. Moreover, any eventually required exchange of a heatable endless band is possible with a minimum of cost and complexity.
With the heatable endless band, only a relatively small mass has to be heated or cooled in comparison with the known heated, chill-cast rolls, and no replacement rolls are required, i.e., only a replacement band, which further reduces the total cost of operation. The heating can occur at favorable cost, e.g., by steam or by another gaseous medium, and additional lubrication is not required because the condensate of the gaseous medium or steam provides such lubrication. Further, the endless band of higher thermal conductivity can be straightforwardly heated both in total, i.e., across its entire width, and also zone-wise. Zone-wise heating in particular can be possible without problems and with a minimum of cost.
While the use of a heatable endless band of high thermal conductivity is admittedly already known from EP 0 370 185 A1, this apparatus is provided with a metal band that is heated from the outside via an inductive heater. Alternatively, a non-metallic band can be acted on by steam or heated air from the outside. Moreover, in this known apparatus, both surfaces bounding a respective smoothing zone are to be heated. thus, a heated roll is required on one side of the web to be smoothed. Instead of a heated roll, a heated adjustable support element can also be used.
In a exemplary embodiment of the apparatus of the instant invention, the heatable endless band can be acted on by the heating medium upstream of the support surface in the web running direction. In this manner, timely condensation provides reliable hydrodynamic lubrication.
With a heating apparatus which is controlled zone-wise over the width of the web, by which the heatable band can be acted on by the heating medium with zone control, a further optimization of web treatment is possible. In this arrangement, the heating device can include, e.g., a zone controlled steam moistener or a steam blowing box.
In order to assist the formation of condensate, the support surface can be formed by at least one support element which is cooled, at least in the region of the support surface. A metal band can be provided, e.g., as the heatable endless band of high thermal conductivity.
In order to ensure smoothness and/or gloss values which are as ideal as possible on the acted on surface of the material web, the support surface can be expediently formed by at least one stationary support element of high rigidity. For example, a support shoe or the like can be provided as the support element.
A condensate removal device can be advantageously provided within the band loop of the heatable endless band and positioned, with respect to a web running direction, downstream of the support device. The condensate removal device can include, e.g., a removal channel with an associated doctor blade. Alternatively, or additionally, at least one suction device can also be provided. The region within the band loop can be expediently kept at ambient pressure, e.g., by a suitable vapor extraction system.
The heatable endless band can be guided over at least one band guiding roll and/or one tensioning roll.
In an expedient embodiment of the apparatus of the present invention, at least one heatable endless band having a hard and smooth surface may be simultaneously associated with a plurality of deflection controlled rolls, each having a soft or elastic surface. In this manner, th
Greenblum & Bernstein P.L.C.
Huynh Louis K.
Vo Peter
Voith Sulzer Papiertechnik Patent GmbH
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