Drying section of a paper machine

Details Drying section of a paper machine Drying section of a paper machine

1996-04-09

1998-06-23

Chin, Peter

Paper making and fiber liberation

Apparatus

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

162206, 162361, 1623602, 34114, 34115, 34117, 34118, 34121, 34122, F26B 1102

Patent

active

057700150

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a drying section of a paper machine with the features set forth in the preamble claim 1. Such a drying section is known from DE 43 28 554 A1. Drying sections of this prior design are suited particularly for paper machines operated at high speeds and intended for the production, e.g., of paper for graphical use. An essential characteristic of the prior drying section is that at least one single-row drying group is available. Such single-row drying group has only a single row of cylinders and between each two cylinders a deflection roll, which may be a suction roll. The paper web being dried is in such a single-row drying group carried constantly by a continuous hold-down belt (e.g., a drying wire) which, for one, forces the paper web on the drying cylinder and, for another, carries it from one drying cylinder across the following deflection roll to the next drying cylinder. This avoids running the paper web freely, i.e., without support, from one cylinder to the following cylinder. The risk of web break is distinctly reduced thereby.
The present invention now addresses the objective of proposing a drying section that is suited primarily for the production of relatively thick paper webs or of cardboard webs where--as compared to conventional drying sections--an increased strength of the finished web is achievable for these web grades.
This objective is accomplished according to the invention by application of the feature set forth in the characterizing part of claim 1. It has been recognized that a considerable compaction of the paper web can be achieved by application of an unusually high longitudinal tension of the hold-down belt (at least 10 kN/m) in a single-row drying group (a so-called "high-pressure group"), i.e., by the combination of the features of a particularly high contact pressure of the web on the cylinder and avoidance of unsupported web trains from cylinder to cylinder.
Such compaction yields an appreciable increase in the strength of the finished paper, and such increase in strength is evidenced, e.g., by the so-called ring crush test. (For comparison: customary so far in drying wires are longitudinal tensions of 3-5 kN/m; refer to Lehrbuch der Papier- Production/Authors' Collective!, 2. edition, Leipzig, VEB Fachbuch-Verlag, 1987, pp. 286 and 287.)
Especially good results in the purport of the above explanations are expected when using in the hold-down belt longitudinal tensions between 10 and 100 kN/m. Such high compaction can be achieved by selection (as compared to heretofore) of relatively small cylinder diameters, for example, of maximally 1 m. Moreover, a further improvement can be achieved by configuring the deflection rolls of the "high-pressure group" as suction rolls and adjusting the vacuum in the suction rolls to at least 0.5 m water column, preferably between 1 and 4 m water column.
In contrast to the single-row drying groups of the initially mentioned prior drying sections for graphical papers, configuring the high-pressure drying group as a single-row drying group is not required primarily for avoiding web breaks but, as explained above, in order to achieve in combination with the high longitudinal tension of the hold-down belt a high compaction of the web. Such web compaction need not take place across the entire length of the drying section but, for reason of space savings, may be restricted to the so-called major shrinking zone. This means that the remaining parts of the drying section can be configured in customary fashion, either entirely with two rows or as mixed single and double rows.
In other words: in a preferred embodiment of the invention, at least one conventional double-row drying group precedes the "high-pressure group" described above; the major task of the double-row group is building up heat in the web entering the drying section. But in drying relatively sensitive paper webs it may be suitable to provide in front of the double-row drying group still a conventional single-row drying group, where a relatively low longitudinal tension

REFERENCES:
patent: 3151953 (1964-10-01), Justus
patent: 3319352 (1967-05-01), Haigh
patent: 3354035 (1967-11-01), Gottwald et al.
patent: 4461095 (1984-07-01), Lehtinen
patent: 4622758 (1986-11-01), Lehtinen et al.
patent: 4692212 (1987-09-01), Swenson et al.
patent: 5291666 (1994-03-01), Babinsky et al.
Lehrbuch der Papier-und Kartonerzeugung/Autorenkollektiv, 2. edition, Leipzig, VEB Fachbuch-Verlag, 1987, pp. 286 and 287.

Affiliated with

Also associated with

Rating

Drying section of a paper machine does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Drying section of a paper machine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drying section of a paper machine will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1391473