Press arrangement and process

Details Press arrangement and process Press arrangement and process

2000-01-24

2002-05-07

Silverman, Stanley S. (Department: 1731)

Paper making and fiber liberation

Apparatus

Running or indefinite length product forming and/or treating...

C162S358100, C162S358300, C162S202000, C162S203000, C162S204000, C162S205000

Reexamination Certificate

active

06383340

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 199 04 576.3, filed on Feb. 4, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a press arrangement and process for treating a fibrous material web, e.g., a paper or cardboard web.
SUMMARY OF THE INVENTION
The present invention provides a press arrangement of the type generally discussed above, which also has a simple and compact design, as well as vacuum requirements and drive output that are as small as possible. In addition, closed web guidance system is possible.
Therefore, the present invention provides two shoe press rolls assigned to a central press roll, which acts as a shared counter-roll. In this way, the shoe press rolls, along with the central roll, can be arranged to form press nips that are elongated in the web travel direction. Further, the first elongated press nip, as viewed in the web travel direction, is provided with two felts.
With this design, the conventional, large suction press provided with a thick jacket can be omitted which in turn appreciably reduces the vacuum requirements. Thus, there is an overall appreciably smaller power requirement. In particular, it becomes easy to provide the web with a closed guidance system, so that the corresponding press section is particularly suitable for liners with a “white top.” By using an opposing roll assigned to the two shoe press rolls, the number of needed press rolls is also reduced to the minimum, i.e., a maximum of only three press rolls is required. Accordingly, the number of necessary press felts is also reduced, and this reduced felt consumption lowers operating costs. Operating costs are further reduced by the lower vacuum requirement for tube suction devices and by the lower power requirement.
In particular, an arrangement becomes possible in which the press forces for the most part counterbalance each other. Furthermore, there is a reduced bearing load and a reduced bending load on the roll axle, and it is possible to eliminate an inwardly supported roll, if need be, for all machine widths. The decreased energy consumption is in part due to the fact that, with only one opposing roll assigned to the shoe press rolls, the lower bearing friction lessens the amount of friction created within the press arrangement. The reduction in the number of felts thereby reduces felt reconditioning, which further reduces friction and the vacuum requirement. Losses caused by rolls that are inwardly supported are eliminated, and only a single drive outside of the given paper machine is necessary, which results in improved efficiency. When the number of employed rolls and roll types are reduced to a minimum, the number of reserve rolls needed also becomes low, which in turn has a favorable effect on investment costs. Moreover, a simpler control system becomes possible, which thereby increases operating safety. Compared to conventional multi-roll presses, the line of force is not affected by reciprocal nip forces, and camberings become largely unnecessary. It is also no longer necessary to use soft roll covers, which results in longer tool lives. A varying degree of pull on the paper is practically eliminated. Consequently, it is possible to avoid web tears within the press section. In particular, it is possible to have a simpler, lever-free, and compact support with a closed flow of force. With the elimination of press roll scrapers for paper removal, the investment and operating costs are further diminished.
The two shoe press rolls can preferably be positioned on opposite sides of the central press roll.
In an exemplary embodiment of the press arrangement according to the instant invention, each of the two elongated press nips are provided with two felts. Overall, this provides symmetrical dewatering that also affords a savings in terms of volume. In paper manufacturing, the equal-sidedness of the paper is particularly improved, so that the press arrangement can also be used for graphic papers.
In another exemplary embodiment of the press arrangement according to the invention, a total of at most three felts is provided. A felt can be guided through both elongated press nips. Only three felt treatments are therefore necessary which in turn reduces the creation of friction as well as the vacuum requirement. There is a reduced total felt consumption. Overall, a compact and cost-effective design is possible. Not only can the suction press roll be omitted, but a closed web guidance and relatively short remoistening zones are possible. Good nip dewatering is provided after each nip, which can be achieved by, e.g., centrifugal water removal.
A highly reliably transport of the web can be achieved with a closed web guidance system from the screen to the drier section, and the press arrangement practically eliminates tears in the web. Furthermore, the manual setup of the fibrous material web is eliminated, which results in a higher degree of operating safety and greater machine availability. Moreover, due to the absence of open pulls, it is practically impossible to have paper stretching and/or web tears. There are also no fluctuations in pull on the paper between the presses.
Between the two elongated press nips formed with the central press roll, the fibrous material web, along with a felt, can ideally be guided around a deflection roll preferably designed as a suction roll.
In a useful practical embodiment, a felt guided through the first elongated press nip simultaneously serves as a pick-up felt.
It is also advantageous for the fibrous material web, following the second elongated press nip, to be guided over a deflection roll in the form of a suction roll, e.g., to an adjacent drier section. Here, the fibrous material web can be conducted around the deflection roll, along with an upper felt running through the second elongated press nip, and then be removed from the upper felt by a smooth roll. As an alternative, it is possible, e.g., to guide the fibrous material web, along with a lower felt, out of the second elongated press nip and to remove it from the lower felt in the area of the deflection roll, specifically with a drying screen which wraps around the deflection roll.
The surface of the central press roll and/or the press jacket of at least one shoe press roll can be blind-bored and/or grooved in order to create a certain water storage capability. In this way, the dewatering of one or both elongated press nips can be performed at least in part by centrifuging the water through a given groove. This not only assures the optimal dewatering of the given press nip, but can enable the use of lighter press felts. Finally, improved felt conditioning via tube suction devices and spray tubes may be provided.
In certain cases it may be useful for the support devices assigned to the press shoes of the two shoe press rolls to be able to be subjected to the same pressures. Here, it will be more effective for the length of the first elongated press nip to be greater than the length of the second elongated press nip. In particular, it is possible to have equal line forces. In an alternative embodiment, the supporting device assigned to the press shoe of the first shoe press roll can be subjected to a lower pressure than the supporting device assigned to press shoe of the second shoe press roll. In this case, it will be effective for the two elongated press nips to have the same length. Here in particular, the line force of the second elongated press nip can be greater than that of the first elongated press nip.
For reasons of weight, it may be useful for the central press roll to be an inwardly supported roll and to be provided with the pressures assigned to each of the press nips.
In order to influence the felt tension between the two elongated press nips, it may be advantageous for the deflection roll to have an adjustable drive.
Accordingly, the present invention is di

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