Paper making and fiber liberation – Apparatus – Running or indefinite length product forming and/or treating...
Reexamination Certificate
1998-06-30
2001-06-19
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Apparatus
Running or indefinite length product forming and/or treating...
C162S198000, C162SDIG004, C162S205000, C162S358200, C162S360300, C162S262000, C100S16200R, C100S16300R, C100S16300R, C100S047000, C100S035000, C100S168000, C100S120000
Reexamination Certificate
active
06248215
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 197 29 531.2, filed on Jul. 10, 1997, 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 a calender with a plurality of rolls having axes located in a press plane. The plurality of rolls are arranged such that adjacent rolls form a nip between each other, and the calender includes a control device to open and close the nips.
2. Discussion of Background Information
During the glazing of a paper web, the paper web is guided through a calender and, within the nips (or roll openings) of the calender, is pressed under pressure, and, if necessary, with an increased temperature. This method of pressure treatment in the calender determines the surface characteristics of the processed web. Thus, it is apparent that the quality of the web surface can be improved by increasing the number of the nips.
However, in many cases a high surface quality is not necessary or desired. In other words, a lower number of nips may be utilized to produce a web with adequate surface characteristics.
For example, it is known from EP 0 661 405 A1 to provide a calender with four rolls and three nips, and that the rolls are adjustable so that the calender includes three, two, or even only one nip. When less than three nips are utilized, the bottom nip or nips are closed, while the other, i.e., upper, nips remain open. The line load that effects the paper web can be altered in this arrangement, e.g., utilizing three deflection adjustment rolls. Moreover, the sequence of the nips is fixed, i.e., when both nips are closed, treatment in the third nip must follow treatment in the second nip. In this manner, possibilities of variation are somewhat limited.
Another calender is discussed in German Patent Application No. 196 31 056, in which a roll stack having several nips in a calender is combined with a roll pair having only one nip. Both roll stacks have a common roll and can be driven alternatively. However, in this case, the industrial expenditure is relatively high due to an additional deflection adjustment roll with two operational directions.
SUMMARY OF THE INVENTION
The present invention increases operational flexibility of a calender during the glazing of material webs while maintaining a reasonable cost of operation.
The calender of the present invention, which is similar in general to the calender discussed above, provides positionally adjustable rolls so that at least two opened nips are positioned between two closed nips.
In accordance with this embodiment, the calender may alternatively be operated so that all nips may be closed, i.e., pressure is imparted on the material web in all nips. In this manner, surface quality of the web will be relatively high. Likewise, the calender may be operated so that all nips are not closed. Thus, in contrast to known calenders, the user chooses, e.g., at the beginning of the material web treatment, which nips are unnecessary and should simply be left out, i.e., remain open. Thus, the material web is glazed in one or more closed nips, bypasses the unnecessary nips that remain open, and is further treated in a subsequent closed nip or nips. Since the nips that do not treat the material web remain open, the rolls are conserved here. With soft nips, in particular, in which the nip is formed with a roll having a soft surface layer, it is practically impossible to close the nip without web being guided therethrough, without adversely effecting, and generally, destroying the soft roll surface. That is, the web is utilized as an insulator, and when lacking, inconsistent temperature rises on the elastic coating over time may lead to the undesired destruction of the soft roll surface, e.g., the covering thermally embosses itself and is destroyed. Moreover, contaminations leaking into the roll opening can lead to surface damage on the covering. However, if the nips remain open, this danger does not exist. Thus, it is no longer necessary to be committed to executing a treatment cycle of nips, as determined by the roll cycle in the calender. Because the nips remain open and the web can be redirected, the pattern of the treatments steps of the material web can be selected relatively freely. Thus, in the present invention, the calender combines the ability to perform glazing to attain a high gloss or high smoothness and the ability,to produce a reduced surface quality via a treatment in a lower number of nips. Thus the operational possibilities of the calender are expanded.
In a particular embodiment, the closed nips are formed by the two outer roll pairs to simplify control of the rolls. In many currently available calenders in the art, the rolls are driven apart so that all nips are opened, e.g., to introduce or thread the paper web. However, according to the present invention, when only the two outer roll pairs are utilized to form the closed nips, then it is necessary only to move two rolls to close the nips.
In a particular embodiment, the two end rolls are formed as deflection adjustment rolls. In this manner, the two closed nips may have pressure forces applied that exceed the forces necessary to balance the individual weight of the rolls. Thus, treatment possibilities are expanded.
From the rolls bordering the two closed nips, it may be advantageous if at least one of the rolls is driven. In this way, treatment of the material web is possible in both nips without the material web being exposed to prohibitively high tensile forces. All rolls may advantageously have their own drive and at least the drives of the rolls that border the opened nips may be individually controlled. These drives may be shut off if the nips remain open so that the rolls of an open nip to do not rotate.
It may be advantageous to positionally fix one of the rolls forming the closed nip in a stay. This arrangement will simplify the control for producing the closed nip because the other roll must only be advanced, i.e., guided toward the positionally fixed roll, and, if necessary, pressed by the positionally fixed roll.
It may be particularly advantageous to arrange the top roll as the fixed roll and provide the bottom roll with a lifting drive. Similar construction is known from conventional calenders, in which all nips are closed by the lowest roll being lifted, thereby lifting all the rolls until the second roll from the top forms a closed nip with the top roll. Thus, with two simple modifications in accordance with the present invention, the known calender arrangement may be reconstructed into a more flexible calender. For this, only the second roll from the bottom may be able to be stopped, or be provided with a stop, and the second roll from the top must be provided with its own lifting drive. As noted above, conversion is simple and can also be undertaken with existing calenders.
It is advantageous that at least one roll can be positionally stopped upon closing the at least one nip and that the other roll includes a pressure transducer. In order to close the nips, therefore, only a single roll movement is necessary. The other roll becomes positionally fixed.
In this manner, it is especially advantageous that the pressure transducer works upon one end of a two-armed lever and the other roll is arranged on the other end of the lever. Enough space at the location of the pressure transducer is thus present, and the leverage can be utilized to guarantee a suitable power impingement in the nip.
The other roll is preferably designed as a roll with a press jacket. This is a possibility which can be selected as an alternative or in addition to the use of a pressure transducer on a two-aimed lever. With a roll with a press jacket, the necessary pressure may be created in the nip so that the entire roll jacket is displaced.
It is advantageous that both closed nips are formed as soft nips. In this manner, the calender may be made either as a conventional
Cramer Dirk
Wagner Ulrich
Greenblum & Bernstein P.L.C.
Halpern Mark
Silverman Stanley S.
Voith Sulzer Finishing GmbH
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