Paper making and fiber liberation – Processes and products – Conditioning – preparing or repairing of apparatus
Reexamination Certificate
2001-12-31
2004-04-06
Hug, Eric J. (Department: 1731)
Paper making and fiber liberation
Processes and products
Conditioning, preparing or repairing of apparatus
C162S198000, C162S162000, C162S275000
Reexamination Certificate
active
06716316
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 101 02 199.2, filed Jan. 18, 2001, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for conditioning a circulating felt belt of a machine, in particular a paper machine, used to produce a fibrous material web, in particular a paper or cardboard web.
A corresponding treatment or conditioning of felt belts can serve, for example, to improve the profile quality of felt and paper, to improve the web running properties, and possibly also an increase in the stability of the dewatering and/or the dry matter content, etc.
2. Discussion of Background Information
At least one pressing felt is generally used for pressing the paper web for the purpose of increasing the dry matter content. In order to achieve an even as possible increase of the dry matter content crosswise to the machine direction, i.e., an even moisture cross direction profile, various felt conditioning devices are used. As a rule, these devices comprise a device for drawing water into the felt and a subsequent device that suctions out of the felt the water that has been drawn into it.
In spite of such a felt conditioning, an uneven loading of the felt with contaminants and an uneven compression of the felt occur during the service life of the felt, which leads to an uneven dewatering in the pressing nip. Up to now, a correction of the resulting uneven moisture cross direction profile has been performed by means of a zonal temperature increase in the press nip by applying water steam to the paper web. However, this does not eliminate the causes of the unevenness in the condition of the felt.
In a paper machine known from U.S. Pat. No. 4,378,639, the fibrous material web is constantly monitored for dry streaks in the drying section and the web is correspondingly moistened depending on the results of the monitoring. In a conditioning process known from DE-A-44 19 540, various methods are used for conditioning felt belts. Paper machines are also already known in which the respective state of a felt is monitored in order to be able to perform the conditioning of the felt depending on the detected condition of the felt (cf., for example, EP-A-0 383 486, EP-A-0 024 205). In a paper machine known from DE-A-198 60 567, the conditioning of each transport belt occurs depending on the contamination of this transport belt that is detected.
SUMMARY OF THE INVENTION
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.
One aspect of the invention resides in further developing the process of the type mentioned at the outset in such a way that the moisture cross direction profile can be optimally corrected in order to attain an even moisture cross direction profile, in particular.
In order to attain this goal, a process is recommended according to the invention for conditioning a circulating felt belt of a machine, in particular a paper machine, used to produce a fibrous material web, in particular a paper or cardboard web, in which a conditioning is performed in zones across the felt belt width, in that at least one fibrous material web property cross profile and/or at least one felt belt property cross profile such as, in particular, the water content of the felt belt across the width of the web and/or the belt and/or the permeability of the felt belt across the width of the web and/or the belt is measured and the felt belt is conditioned in each of the various zones depending on the measuring results obtained for the applicable zones.
The zonal conditioning can, for example, occur in addition to a conditioning that is effective across the entire belt width. However, this is not obligatory in any case.
Thus, for example, it is possible in particular to correct deviations in the moisture cross direction profile and to achieve an even moisture cross direction profile by means of a targeted treatment or conditioning of the felt in places where deviations of the felt properties from the desired values occur and, e.g., a particularly high degree of compression or contamination, a deviation from the desired water content and/or the like is present. Here, it is possible, for example, to apply water at compressed places in the felt and/or to suction water off at compressed points in the felt or to blow water out using pressurized air, using a spraying pipe, for example, a high-pressure spraying pipe.
According to a suitable practical design of the process according to the invention, a mean value is calculated from measured values obtained for the various zones and the intensity of the conditioning in a respective zone is selected depending on the deviation of the measured result from the mean value.
It is possible, for example, for the following devices to be used individually or in any desired combination with one another for the purpose of zonal felt conditioning.
Thus, the felt conditioning can occur at least partially, for example, by means of at least one traversing spraying pipe nozzle. Using an appropriate guide, it is thus possible to approach all points across the width of the felt. The nozzle can, e.g., either travel across the felt belt at an even speed, in which case the water pressure can be correspondingly regulated with the cross profile deviation as a correcting variable, or the speed of the nozzle and thus its lag time at various positions can be regulated, at a constant water pressure, with the cross profile deviation as a correcting variable.
Alternatively or additionally, the felt conditioning can at least partially occur also by means of at least one spraying pipe comprising several nozzles, which can be controlled zonally and can also preferably be moved over the width of the zone. For a targeted conditioning of individual felt areas, the individual spraying pipe nozzles can each be controlled by the relevant valves.
Alternatively or additionally, the felt conditioning can at least partially occur also by means of a zonally controllable pipe suction apparatus that is additionally preferably movable over the width of the zone. Using such a pipe suction apparatus, individual regions of the felt can be suctioned in a targeted manner.
A pipe suction apparatus can be used, for example, that has a ceramic body extending at least essentially over the entire width of the felt, which ceramic body is provided with a slotted surface by way of which the felt belt can be subjected to vacuum, with the effective slotted portion of the surface being variably adjustable by zones, in particular using movable tongues, e.g., metal tongues in order to correspondingly vary, in particular, the respective effective time of the vacuum.
However, the felt conditioning can, for example, also occur at least partially by means of at least one traversing short pipe suction apparatus that has a ceramic body that is provided with a slotted surface by way of which the felt belt can be subjected to vacuum, where the effective slotted portion of the surface may be variably adjusted by means of at least one movable tongue, e.g., a metal tongue, in order to correspondingly vary, in particular, the respective effective time of the vacuum.
Further examples of possibilities for treating and/or conditioning the felt are as follows:
Pressurized air for blowing out water, e.g., regulation of the water content
Chemical conditioning additives, profiling by means of amount and/or dosing, e.g., regulation of the permeability
All types of treatment and/or conditioning are possible on the paper side and/or the running side.
The significance of even moisture cross direction profiles after a pressing section is a deciding factor for the degree of effectiveness and the quality of the final product. If, for example, moist areas occur, the strength of the web is reduced at that point, which is connected with a significant
Bamberger Wolfgang
Begemann Ulrich
Grabscheid Joachim
Kleiser Georg
Mayer Wolfgang
Greenblum & Bernstein P.L.C.
Hug Eric
Hug Eric J.
Voith Paper Patent GmbH
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