FI111859B - A press section of a paper machine where one or more long nipples are applied - Google Patents

Abstract

A press section in a paper machine, which press section comprises at least two separate press nips (NP1, NP2; N1, N2, N10, N20, N30, NP10, NP11, NP20, NP21, NP30). The paper web (W) is passed through these nips as a closed draw. In the press section there is at least one press nip provided with two press felts (31, 41; 32, 42) that receive water, through which press nip the paper web (W) runs between said press felts (31, 41; 32, 42). After the last-mentioned nip the paper web (W) is separated from one of the press felts (31/41; 32/42) and transferred on support of the other press felt (41/31; 42/32) as a closed draw further. The last nip is an extended-nip zone (NP2; NP10; NP20, NP21, NP30), in which one roll is a shoe roll (12) provided with a hose mantle (14) and with a press shoe arrangement (13), and the other roll is a press suction roll (22) provided with a suction zone (23). The paper web (W) is passed through the last extended-nip zone (NP2; NP10; NP20, NP21, NP30) between two press fabrics (32, 42). Directly after the last extended-nip zone (NP2; NP10; NP20, NP21, NP30) the paper web (W) is separated from one of the press fabrics (32/42) and transferred, with the aid of the vacuum present in the suction zone (23) of the press suction roll (22), to follow the press fabric (42/32) placed at the side of the press suction roll (22) without rewetting. The web (W) is passed on the latter press fabric (32; 42) as a closed draw onto a drying wire (51) of the dryer section. Further, a modification of the press section is described in which an extended-nip zone which corresponds to the extended-nip zone mentioned above and placed as the last nip is placed as the first nip in the press section.

Description

5, 111859

Paper machine press section with one or more long nipples pressparti i en pappersmaskin, i glance pressparti et eller flere pressnyp tillämpas

The present invention relates to a press section of a papermaking machine comprising at least two 10 separate press nips through which the pressable paper web is guided essentially closed for export and wherein the press section has at least one press nip having two water-receiving press felts. from the second press felt and moved in the support 15 of the second press felt mainly as a closed export.

One of the most important quality requirements of all paper and board grades is the consistency of the structure in both micro and macro dimensions. The paper, especially printing paper, must also have a symmetrical structure. The good printing properties required of the printing paper imply good smoothness, uniformity and certain absorption properties of each surface. Paper. _. # properties, especially density symmetry, are greatly influenced by the operation of the paper machine, ···, press section, which is also crucial to the smoothness of the paper cross sections and ....: machine direction profiles.

♦ ·: * · *; 25 Increasing the speed of paper machines presents new problems, most often related to machine runnability. Today, machine speeds of up to 1600 m / min are used. At these speeds the so-called. closed press sections comprising a smooth surface::: compact press roll combination fitted around the chassis generally work

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satisfactorily. Examples of these press components include the applicant's SymPress II

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30 and SymPress O press parts.

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Recently, the so-called "spin-offs" have become more common. shoe presses having a second press roll with a shoe roll with a flexible hose diaphragm and a press roll with a counter roll, generally a deflection controlled or compensated roll with a solid sleeve on the surface, such as the applicant SymZL Roll. Said long nip press is marketed by the applicant under the trade mark 5 SymBelt ™ Press. It is, therefore, an object of the present invention to develop new concepts utilizing a long nip press or presses in a new advantageous manner.

Pressurized dewatering is more energy efficient than dewatered 10-bar dewatering. For this reason, it is desirable to remove as much water as possible from the paper web to minimize the amount of water removed by evaporation. However, raising the speed of paper machines up to ~ 2000 m / min poses new problems specifically for dewatering by compression, because the compression pulse and peak pressure of roll presses cannot be raised above a certain limit without breaking the structure of the web and because at high speeds the nip times are not sufficiently short.

The above mentioned problems are partly solved by the aforementioned long nip clamps, such as: •: ·. Applicant, SymBelt ™ Press, supra.

A: 20: Raising Paper Machine Speeds Also Emphasizes Paper Machine Runnability Problems ·: ··· More and more pronounced because the aqueous and weak web does not withstand the dynamic forces of: Y: speed and direction changes, but it causes gears and other malfunctions, which cause downtime. Therefore, the press sections of the papermaking machine are becoming a bottleneck in an attempt to raise the speeds of the papermaking machines to a range of 2000 m / min.

: Y: A particular problem with the known press parts is the so-called. back wetting, »* ·. *: which means that water forced into the press felt in the nip zone is transferred 3111859 back to the web. This is particularly problematic after the last nip, where the final dry matter of the web is determined by the nip, which tends to decrease back wetting. Indeed, in many prior art press sections, it has been a major drawback that the dry matter content of the paper web has been reduced by several percentage points compared to the dry matter content immediately after the last press nip before the web is obtained on the drying section.

In prior art presses, the problem is often that the web, after the nip zone, is followed by a predetermined press fabric or 10 transfer ribbons intended to advance the web under all varying driving conditions and regardless of the type of press fabric or web used. In practice, what the tissue or ribbon after the nip zone follows the web is already determined by the nip zone. As has been known in the art, it has been attempted to ensure the web tracking with a specific press felt 15 by using various felt angles, suction zones and / or transfer suction rolls, the suction zone of which extends beyond the actual press nip zone.

The following describes the operation of known, mainly closed roll presses: ·. and their development needs.

20 • · I ·

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; The first nipple of the SymPress II type press is a double felt and has a ·; · * · suction roll as an upper roller, the vacuum of which follows the web, which is

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::: at the same time pickup felt. This solution worked well with SymPress II. In such a '' 'solution, the depressurized holding zone begins at the first nip and continues to the next nip, and the vacuum level is arranged to be adjustable. In addition,> »# '·: the cover of the lower blanket on the top blanket after the first nip is set so that v: runnability is good and re-wetting is minimized. The disadvantage is that the pickup blanket: passes through two nipples so that there is wear and dirt on the blanket. A roll nipple with a second roll suction roll limits the line load to a maximum of »· · 4 111859 100 - 150 kN / m. With shoe press solutions, the line load can be increased up to 300-400 kN / m (up to 1500-2000 kN / m depending on the back roll) and the nip length can be varied, resulting in a higher dry solids content and better control than the roll nip.

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For the prior art most closely related to the present invention, reference is made to Applicant FI Patent Application 951934 (corresponding to U.S. Patent Nos. 5,650,049 and EP0740,017 A1), Beloit Corporation U.S. Patents 4,483,745, 4,704,192 and Voith Sulzer Papiermaschinen GbmH utility model DE 297 01 948 UI. In addition, various long nip press geometries 10 are shown e.g. Applicant U.S. Patent No. 4,976,820; and European Patent Application Publication No. 0 487 483 A1 (FI Application No. 905798). Reference is also made to Beloit Corporation in WO 91/08339, WO 95/16821 and J.M. U.S. Patent No. 5,178,732 to Yoith GmbH (DE 40 26 021) and DE UI 92 06 340 and DE AI 41 12 355 of Sulzer-Escher Wyss GmbH, however, do not disclose (in combination) the features of the invention which in the present invention are necessary to achieve the intended effects.

*: *. It is an object of the present invention to provide novel press section concepts, v; 20 which can largely avoid the disadvantages discussed above and provide a press section which contributes to increasing the speed of the paper machine when needed * I ·; ··; to ~ 2000 m / min.

It is a particular object of the invention to provide a press section which is particularly suitable for the production of 25 types of printing and writing paper, generally having a basis weight of <100 g / m2.

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v · and which require good symmetry in the z-direction and sufficient smoothness and filler content on both surfaces.

5, 111859

To achieve the foregoing and later objects, the invention is essentially characterized in that the last nip of the press section is a long nip zone, the second roll being a shoe roll with a hose jacket and a press shoe system and a second roll with a suction between the press felt, that immediately after said last long nip zone, the paper web is separated from the second press felt and moved by the vacuum pressure of said press nozzle suction zone to follow the subsequent pressing of to which the web has been transferred by suction roll or the like Sat arrangement.

In the two felt nip or nips preferably used in the invention, water is removed from the web to both felts and, under the effect of the pressure of the press suction roll, the web follows the right felt to which the effect of the vacuum is applied. In this case, immediately after the nip, the press felts can be immediately separated and the web is moved forward on the surface of the right felt. In addition, the suction roll vacuum will: · · # improve the drainage of the nip, thus increasing the dry solids of the web. As the web follows the right blanket just after nip 20, the other felt will follow the nip <* ·, ···. re-wetting will decrease as the web is no longer in contact with the felt.

«· · ....: Also, the re-wetting caused by the felt followed by the web decreases because; Y: the vacuum pressure of the suction roller holds the water better in the felt, and as the web expands (in the z direction): ·: absorbs less water. Since, in the press section of the invention, the web already selects the right felt in the 25 nips, there is no need for a separate transfer suction roll or the like after the nip to::: force the web to follow the right felt. Such a transfer suction roller could cause I · · v · to cause abrasion on the web, since the transfer suction roll may have different felts: Y: speed or tension.

v. 30 6 111859

The long nip itself provides a higher dry matter than the roll nip due to its longer nip and higher line load. If the arrangement of the invention is applied to the first nip, high speed or high basis weight nip has better runnability than the roll nip.

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It is also an advantage of the invention that, since in a two-felt nip arranged according to the invention, the web immediately after the nip zone is separated from the second felt, any difference in velocity of the respective felts does not adversely affect the web.

However, when the arrangement of the invention is used in the long nip zone, particularly when the long nip is the last nip of the press, a sufficiently long residence time at the last nip is obtained using a sufficiently low peak compression pressure. contributes to the fact that the long-nip has a good dewatering capacity in itself, which is further enhanced by the suction roll used as a long-pitch counter roll while avoiding back wetting.

, *: ·. The press section according to the invention is particularly well suited to all types of printing and writing * · 9 * 9 ·. V, 20 for the manufacture of peril species generally having a basis weight of less than 100 g / m. A preferred embodiment of the invention which uses two consecutive long nipples, both of which are particularly suitable for the production of printing and writing papers; Y: bifurcated, giving a particularly symmetrical dewatering and hence printing: the required symmetry in the z direction.

25 »t * v 'When using a press nip roller as a back nip roll hose roll in the invention, it is advantageous to use a sufficiently large suction roll diameter because of the high nip loads; : D »800 - 2000 mm and greater than normal suction roll strength: s« 50 - 120 mm. The bending suction roll can also be used in the invention as

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, y. 30 retracted or adjusted rolls, such as the applicant's trademark SymZ Roll.

IUII <· 7 111859

In contrast to the most commonly used press suction die solutions, the invention extends the suction zone of the press nozzle only substantially to the width of the long nip zone, whereby the extent of the suction sector on the press nozzle will generally be in the range ~ 8 ° to 16 °. This arrangement provides a sufficiently sharp and effective suction effect and saves suction energy, but still ensures that the web follows exactly the felt that is assigned to move the web forward after the nip zone.

In a preferred embodiment of the invention, a completely closed passage from the forming wire to the drying wire is carried through the press section. An exception to this sealed export may be the short free pull, possibly used in the invention, from the smooth surface of the press member to the paper guide roller and further.

In the following, the invention will be described in detail with reference to the various embodiments and variations of the invention shown in the figures of the accompanying drawing 15, however, the details of the invention are by no means narrowly limited.

Fig. 1 schematically illustrates a preferred embodiment of the invention using two:: sequential long nip zones arranged in accordance with the invention and fully enclosed export of the web from the forming fabric to the drying fabric.

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Figures 2A, 2B, 2C, 2D, 2E, 2F, 2G and 2H show various variations of the first press nip arrangement of the press section of the inventive press section.

Figures 3A, 3B, 3C, 3D, 3E and 3F illustrate the arrangements of the second and last nip of the press section of the invention * * · '*' * and export of the web to the drying section, respectively.

Figures 4A, 4B, 4C, 4D, 4E and 4F illustrate arrangement alternatives for the first *: '' 30 closed nip array of the press section of the invention.

111859 8

Figures 5A, 5B, 5C and 5D show the last individual long nipples used in connection with the nip assemblies shown in Figures 4A-4F.

Figures 6A and 6B show two different nip arrangements, the first puris-5 tin roll forming at the same time a pickup point with the forming wire.

Figures 7A and 7B show alternative last nip fittings used in conjunction with Figures 6A-6B.

Figures 8A and 8B illustrate arrangements of a first nip of a press section according to the invention in which, after a closed press roll assembly, the web is further removed from the last press roll by a special transfer belt.

Figures 9A and 9B show separate final nipples of the puris-tin portion applicable in conjunction with Figures 8A and 8B.

·; · # Figures 10A and 10B show a press section in which the first press nip roll of the press forms a pickup point and where the web is taken away from the second. from the press roll with a special transfer belt.

20: Figures 1A and 1B show alternative adaptations of the last separate nip of the press member used in conjunction with Figures 10A and 10B.

:, · Figure 1 illustrates an embodiment of the invention which, according to current knowledge:.:: 25, is most advantageous, particularly in paper machines for the production of printing and writing papers.

> The paper web W is separated from the forming wire 10 at the pickup point P and transferred to the suction zone 35a of the pickup roll 35 on the first upper felt 31 which is in its guide rolls 33.:. directed. Top felt 31 takes web W to first long nip NP1 which is two-

•; · · * The felt and bottom felt is a bottom felt 41 guided by guide rolls 43 which takes the web W

30 still after long nip zone NP1. The web W is applied on the upper surface of the lower felt 41 as a direct run over the blow simulator box 44 to the second upper felt 32, to which it is moved by the suction zone 36a of the transfer suction roll 36. The web W is then passed on the underside of the second top felt 32 over the blowing simulator boxes 34 to another long nip NP2, after which the web W follows a second lower felt 42 guided by the guide rolls 43. At a downward slope of the lower felt 42, the web W is introduced from the second elongated nip2 to the transfer point 5 S, whereby the web W is transferred with the suction zone 50a of the transfer suction roll 50 to a drying fabric 51 which passes through the blowing simulators 52 to the first drying cylinder 53. The purpose of the blowing simulators 34 and 44 between the long nip zones NP1 and NP2 is to hold the web W on the felt 41, 32.

According to the present invention, the long nipples NP1 and NP2 are formed between an upper shoe or hose reel 11 and 12 and a lower press suction roll 21, 22 having a suction zone 23. The structure of the hose reel 11, 12 above the long nipples NP1 and NP2 is known per se, comprising a flexible hose sheath 14 having a press shoe 13 loaded with a hydraulic pressure medium 15a to provide the necessary pressing pressure on the felts 31, 41; 32, 42, so that water is transferred in both nipples ... NP1, NP2 to both felts substantially symmetrically to provide z-I | »· ·. in the direction of a sufficiently symmetrical web having identical surfaces. Such • · * I · ·!.! paper is particularly suitable for writing or printing paper. The vacuum in the suction zone 23 of the press suction rolls 21, 22 20 ensures that after both nipples, v, NP1, NP2, the web W follows the lower felt 41, 42, so that the lower felt 41, 42 can be detached from the upper felt 31, 32 immediately after the nip . The suction zone 23 of the press suction rolls 21, 22 generally has a range of only about 8 ° to 16 °, most preferably ~ 10 ° to 14 °, extending only to or slightly beyond the area of the long nip zone or zones. Because the inventor:. If the press nip roller 21 and / or 22 is used in the long nip zone, the roller in question is ···. 21/22 be dimensioned more heavily than a normal suction roll to withstand long nip large lines »· ·. loads. For this purpose, the diameter of the press suction roll 21/22 is generally selected

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from D ~ 800 to 2000 mm. Also, the thickness of the tear-off diaper 21/22 of the press nip roll and the punching of the t 30 are dimensioned for high nip loads. For this purpose, the thickness s of the sheath roll 21/22 of 10 111859 is generally selected from s = 50 to 120 mm. The proportion of open area, i.e. the percentage of holes R, of the diaper 21/22 diaper is generally selected from R ~ 10-40%. The strength of the diaper 21/22 diaper can also be increased by its material selection. The negative pressure P in the suction zone 23 of the press suction roll 21/22 is generally selected from 5 in the range p <20 - 70 kPa, depending on the application.

Figures 2A-2H show various variations of the implementation of the first press nip according to the invention. Similarly, Figures 3A-3F show various variations for implementing the second and last nip of the press section according to the invention. The first press nipples shown in Figures 2A, 10 2B, 2C and 2D are suitable for use in particular with the last nip of either press member shown in Figures 3A and 3B. Thus, the press sections can preferably be implemented in combinations 2A + 3A, 2A + 3B, 2B + 3A, 2B + 3B, 2C + 3A, 2C + 3B, 2D + 3A, 2D-I-3B. Similarly, combinations of Figures 2E + 3C, 2E + 3D, 2F + 3C, 2F + 3D, 2G + 3E, 2G + 3F, 2H + 3E, 2H + 3F are particularly useful.

In Fig. 2A, the first dual felt 31,41 nip is a roll nipple N1 formed between • · * two, preferably water receiving, surface press rolls 61 and 71.

'· ·. According to Figure 2B, the first nip N1 is a roll nip formed between an overhead press roll 61, preferably an on-surface press roll 61 and an under press press roll 21 having a suction zone 23. In Fig. 2C, the first nip is a long nip NP1 formed between an upper hose reel 11 and a lower press suction roll 21 having a suction zone 23. In Figure 2D, the first nip is the long nip

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, · '.: NP1 formed between the upper hose reel 11 and the lower presser roll 71 having a smooth or hollow surface 72 »i. ·: 25, which is not a suction roll but may be

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:: deflection compensated roll, such as the roll marketed by the applicant under the trademark SymZL Roll.

The second and last nip of the press of Fig. 3A is formed by the upper one. *. between a press suction roll 22 and a hose reel 12 below. 3B, the longitudinal nip NP2 of the press member has hose reels 12 and press nozzle 22 in the reverse order of 30A. The roll nipples N1, the long nip NP1 and the other long nip NP2 shown in Figures 2A to 2D and 3A and 3B are both dual felt 31.41; 32.42.

11 111859

As shown in Fig. 3A, the web is led by the upper felt 32 on the suction roll roll 22 to the drying fabric 51 of the drying section, where it is transferred under the vacuum of the suction zone 50a of the transfer suction roll 50. Similarly, in Fig. 3B, the web W is applied after the last nip NP2 on the upper surface 5 of the lower felt 42 on the side of the press suction roll 22 to a drying wire 51.

In Fig. 2E, the first nip NP1 is a long nip having a lower roll with a hose reel 11 and an upper roll with a press suction roll 21 which allows suction zone 23 to follow web W 31, separating web W from suction zone 45a of transfer suction 45 and transferring it to the nip being roll nip N1 and having a lower roll having a press roll 71 having a smooth or hollow jacket and an upper roll 21 a press suction roll which allows the web W to follow the upper felt 31 from where it is transferred to the transfer roll 45 to the The last nip of the press section shown in 3D is a long nip NP2 formed between the hose reel 12 and the press suction roll 22. In Fig. 3C, the web W follows the press suction roll 22, thanks to the suction zone 23, to the upper felt 32 for transferring it to the drying fabric 51, and in Fig. 3D, the web follows the lower felt 42.

• · · • · · · ·! . In Fig. 2G, the first nip NP1 is a long nip having a top roll of hose roll 11 • · · · · ·, 20 and a lower roll press roll 71 having a smooth surface 72. Instead of a lower felt, a transfer belt 41B which is substantially water-insoluble and thus non-moistened with the web W. After nipple zone NP1 ·: ', web W follows the smooth outer surface of transfer belt 41B from which it is transferred

lan 36 assisted by a suction zone 36a for the upper tissue of the second nip N2. 2H

: V: 25 as the upper fabric in the first long nip NP1 has a smooth transfer belt 3 IB. The nip pin::: NP1 top roll is a hose reel 11 and bottom roll 71 is a press roll with a surface 72.

:. ·. After nip NP1, the web follows the smooth surface of the transfer belt 3BB from which it is moved by another; ; nip for lower felt 42. As shown in Fig. 3E, the second and last nip of the press section, wherein * * ·; , is the long nip NP2, forms the upper press suction roll 22 and the lower hose reel 12 30, and the web follows the nip NP2 from the upper fabric 32, from where it is transferred in closed export 12 111859 to the drying fabric 51. FIG. W follows nip 42 after nip NP2.

Figures 4A and 4B show a closed press roll assembly as an initial part of a press section. Figure 4A shows three successive roll nipples N1, N2 and N3

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SymPress II press section. The first nipple N1 is double felt. The first upper fabric 31a is both a pickup fabric and a press fabric on the first and second roll nipples N1 and N2. The first nip N1 further passes through the lower felt 41a.

The first nip N1 is formed between an on-surface press roll 71a and an overhead press roll 73. After the first nip N1, the web W follows the upper felt 31a, due to the suction zone 73a of the roll 73, moving to the second roll nip N2, after which the web W follows the smooth surface 74 'of the central roll 74. A third roll nipple N3 is formed between the central roll 74 and the press roll 75. After the third roll nip N3, a press felt 76. After the third roll nip N3, the web W follows the smooth surface 15 74 'of the center roll 74, from which it is separated by a short free pull onto the paper guide roll 77 of WP and

to the lower fabric of the next nip 42. The press section shown in Figure 4B differs from that of Figure 4A

shown in that the third nip is the long nip NP10, which is the first ... long nip of the press section. The nip assembly shown in Fig. 4C differs from that shown in Fig. 4A in that only the first lower press roll 71a and the lower felt 41a are missing, so that the first and • ♦, ·· ♦. The other nips N1 and N2 are formed in connection with the center roll 74.

: * ;; Fig. 5A shows a separate final long nip NP21 of the press section, wherein the upper roll: is a press suction roll 22 and a lower roll hose roll 12, the web W follows the upper felt 32 to transfer it to the drying wire 51. the press suction roll 22 is in the reverse order of each other as in Fig. 5A, with the web W following the lower felt 42 following the nip NP21.

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As shown in Figure 4D, the first set of press rolls is the so-called Applicant's. SymPress I: [·. press section having two consecutive roll nipples N1 and N2 followed by web W

»Il ....: 30 is moved from the smooth surface 74 'of the center roll 74 by a short free draw WP on a paper guide roll 77 to the lower felt 42 of the next nip. Fig. 4E shows the applicant's trademark 13 111859.

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A press section marketed by SymPress O, wherein the first roll nipple N1 is formed between an overhead press roll 73 'and a lower press roll 71a and an over press press roll 73'. From the first nip N1, the web is moved over the suction zone 73a of the roll 73 'as an almost vertical draw to the second roll nip N20 formed between the press roll 78 and the central roll 74. A third press nip N30 of the press section is formed in connection with the central roll 74.

Fig. 4F shows a front end of a press section comprising a first long nip NP10 at the N1 position of the first roll nip 10 of Figs. 4A, 4B, 4D and 4E. After the long nip NP10, the web W follows the suction zone of the press suction roll 73 to the second nip N21 formed by the smooth-faced central roll 74. In addition to the center roll 74, there is a second long nip NP11 of the press section formed between the center roll 74 and the upper hose reel 12. The second long nip NP11 passes through a press felt 76. Figure 5C shows a separate last long nip of the press section 15 being the first long nip NP10 of the press section if the nip assembly of Figures 4D or 4E is used or the third long nip NP30 of the press section if two nip assemblies are NP10 and NP11. Fig. 5C shows a long-nip NP10 (NP30) as a top roll press clamp suction roll 22 and a lower roll roll hose roll 12. The rolls 12 and 22 are in the reverse order of Fig. 5D.

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Fig. 6A shows a first nip arrangement of the press section in a so-called. Combi press, wherein the first roll 73b of the press member forms a first press nip • * »* · ';' N1 or transfer nip center roll 74. A second roll nip N2 of the press section is formed in connection with the center roll 74 in connection with the press roll 75. A second nip N2 passes through a purple 25 felt blanket 76, from which web W is separated and further applied to the smooth surface of center roll 74! 6B, the nip assembly shown in Fig. 6B differs from that shown in Fig. 6A in that a substantially water-inert and * t smooth-surface transfer belt 80 is arranged around the center roll 74a. , on the surface of which the web W is introduced after the second nip N2

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• ... • 30 of the press section of the van nip the upper felt 32. Figure 6A shows a press section 14 of the first half 111 859 is suitable for use in both Figure 7A and Figure 7B, the press section in accordance with the second side. Instead, when using the initial portion of the press of Figure 6B, the passage of the fabrics 32 and 42 must be altered to correspond to Figure 6B.

Fig. 7A shows the last separate nip of the press section with the long nip NP10 having a top roll with a press suction roll 22 and a lower roll with a hose roll 12. The rolls 12, 22 mentioned in Fig. 7B are in reverse order to Fig. 7A.

Fig. 8A illustrates a press section 10 of the roller closest to Fig. 4D, with two roll nipples N1 and N2 described above, and a smooth surface, waterproof transfer belt 80 provided around the center roll 74a to provide web W in sealed export to the top felt 32 of the next nip. 8A, in that the first nip is a long nip NP10 with a lower roller having a hose reel 12. Otherwise, the structure is as shown in Figure 8A 15. Figure 9A shows the last separate nip of the press section as the long nip NP20, with the top roll being the press suction roll 22 and the lower roll the hose roll 12. In Figure 9B the press rolls 12, 22 are in the reverse order of Figure 9A.

Fig. 10A shows a so-called Combi press in which the suction roll 73b forms a • 1 ·. Pickup point P with the forming wire 10. The felt 3 passes over the suction zone 73a .... of the suction roll 73b. Ib, the web being supported on a second press roll 74 which forms a first roll nipple N1 with a press suction roll 73b. A transfer belt 80 is arranged around the second press roll 74 to support web 25 for closed export to the upper felt 32 of the next press nip. wherein the first nip nip of the press member is a long nip NP1 formed between the press nip roll 73b and the hose reel 11. A smooth impermeable transfer belt 80 is provided around the hose reel 11 to transfer the web W as a closed export to .

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Figures 11A and 11B show the last nip of the press section being the first nip NP10 of the press section if the first nip N1 of Figure 10A is used or the second long nip NP20 of the press section if NP1 of Figure 10B is used. In Figures 11A and 11B, press suction roll 22 and hose roll 12 5 are in reverse order to each other.

As will be apparent from the attached figures, it is also an essential feature of many embodiments of the invention that the web passes through the entire press section in a very straightforward manner so that there are no large bends in web travel that could expose the web to such high dynamic forces. , such as a press felt or transfer belt. For example, in Fig. 1, the maximum angle of deflection α of the web W is, in the case of the second long-nip NP2, α = 30 ° to 40 °. Generally, said maximum angle of inclination is in the range α <45 °, more preferably α <30 °. In the area of nipples NP1 and NP2, the direction change angle corresponds to the size of the suction sector 23 of the press suction roll 21, 22, which, as noted above, is relatively small, extending only substantially over or slightly beyond the long nip zone NP1 / NP2.

The claims set forth below are defined by the inventive idea. ·. ·. Within the scope of the invention, the various details of the invention may vary and deviate only by way of example. '·'. 20 cinematically presented. 1 · · • I · ·

Claims (10)

A press section of a paper machine comprising at least two separate press nips (NP1, NP2; N1, N2, N10, N20, N30, NP10, NP11, NP20, NP21, NP30), through which a paper web (W) to be pressed has been guided mainly in a closed draft and which press section has at least one press nip provided with two water-receiving press blankets (31, 41; 32, 42) through which the paper web (W) runs between the press blankets (31, 41; 32, 42) and after which the latter the nip paper web (W) is separated from one press blanket (31/41; 32/42) and is further carried by the second press blanket (41/31; 42/32), mainly in a closed draw, characterized in that the last nip of the pressing portion is a longitudinal nip zone (NP2; NP10; NP20, NP21, NP30) in which one roller is provided with a hose cover (12) and a press shoe system (13) and the other roller one with a suction zone (23). ) provided press roll (22), that the paper web (W) has passed through the last longitudinal nip zone (NP2; NP10; NP20; NP21; NP30). or between two water receiving press blankets (32, 42), that the paper web (W) has been separated from one press blanket (32/42) immediately after the last long nip zone (NP2; NP20, NP21, NP30) and continue with the pressure in the suction zone (23) on said press roll (22) to follow the press blank (22/42) against the press roll (22/42) without substantial new wetting: and that the paper web (W) has been brought with the latter press blanket (32; 42) in a closed draw to one: 20 drying wires (51) or the equivalent in a drying portion following the pressing portion, on which the web ·… · (W) has been transferred by suction roll transfer (50, 50a) or with a corresponding arrangement. 2. Press section according to claim 1, characterized in that the first nip in the press section is a longitudinal nip zone (NP1, NP10), in which one roll is one with a hose jacket (14) and a press shoe system (13) provided roller (11) and the second roller one with a suction zone »T (23) press roller (21), that the paper web (W) has been guided through the first longitudinal * · · · * ·· the nip zone (NP1, NP10) between two press tissues (31,41; 3la, 41a), at least one of which is a water-receiving press blanket (31/41), the water-receiving press blanket (30/31/41) being arranged around and in connection with the press roll (21), that the paper web (W) has been separated from the press tissue (41/31) which abuts the shoe roll (11) and is moved by means of the suction zone (23) in the suction roll (21) to follow with the water receiving press blanket (31/41) without substantial new wetting and that the web (W) has continued with the press blanket (31/41 ) in the final pull to a press tissue (32/42) in a subsequent press nip (NP2) in the press section. 5 Press section according to claim 1 or 2, characterized in that the first press nip in the press section is a long nip zone (NP1) according to claim 2 and the second press nip a long nip zone (NP2) according to claim 1 and that the paper web (W) has a closed draw between the long nip zones. (NP1, NP2) and from a forming wire (10) to the first longitudinal nip zone (NP1) and from the last long nip zone (NP2) to the drying portion (Figures 1, 2C + 3A, 2C + 3B, 2E + 3A, 2E + 3B). Press section according to any one of claims 1-3, characterized in that the press section has as a first Upper felt a pickup blanket (31) which is to pass the paper web (W) to the first press nip, which is most preferably a longitudinal nip (NP1). ), the upper roller of which is a shoe roller (11) provided with a hose sheath (14) and a lower roller a press roller (21), arranged around the lower press vacuum roller (21) to run a first lower blanket (41) which the paper web (W) substantially without new wetting on its upper surface to an upper blanket (32) in it: the second longitudinal nip zone (NP2), on which it is transmitted by suction roll transfer (36, 36a); the second longitudinal nip zone (NP2) has been arranged to form a second lower tissue (42), which will move the paper web (W) substantially without new wetting on its upper surface in a final pull to a drying wire (51) in the drying section, on which the paper web (W) has been transmitted by suction roll transfer (50, 50a) (Figure 1). • «· • ♦ · Press section according to any one of claims 1-4, characterized in that the suction zone (23) on the press roller (21, 22) is relatively narrow and extends mainly only over the area of the long nip zone (NP1, NP2) and that the sector width of suction zone (23) in • 1: machine direction is ~ 8 ° - 16 °, most preferably ~ 10 ° - 14 °. • 1 21 111859 Press section according to any of claims 1-5, characterized in that the first press nip in the press is one or more roll nips (N1, N2, N10, N20, N30) and thereafter as the last nip a long nip (NP2; NP20, NP21, NP30). Press section according to any of claims 1 or 4-6, characterized in that the first press nip in the press section is a roll nip (N1), followed by one or two roll nips (N2; N2, N3) and thereafter one or more longitudinal nip. (NP2, NPIO, NP21, NP30). Press section according to claim 7, characterized in that the first nip of the press 10 is formed in connection with a compact roller group having a central roller (74), from whose smooth surface (74 ') the male (W) has been separated in the form of a short free pull (WP) and transmitted with a paper guide roller (77) or equivalent to one of the press tissue (42) in the last separate nip of the press portion, which is most preferably a longitudinal nip (NP10; NP30). Press section according to any of claims 1-6, characterized in that the first nip of the press is a longitudinal nip (NPIO) through which a lower press felt (41a) and an upper press felt (31a), which simultaneously serves as a pickup felt that the first press nip (NPIO) has been formed between a lower shoe roll (11) and an upper press roll V: (73), that the upper blanket (31a) serves as a press tissue even in the second nip in:, V 20 the press portion, which is a roll nip (N21), one roll of which is a smooth surface center roll (74), in connection with which a third nip of the press portion is either a roll nip (N30) or a second long nip (NP11) (Figure 4F). • · • i 10. Press section according to any one of claims 1-9, characterized in that a pressure nip (N1) or roll nip (N1, N2) or a longitudinal nip (NP1) in the pressing section has been guided. * * · * »Substantially non-water-receiving transfer strap (80; 3IB; 41B) supported by which the web (W) has been moved after the latter nip in a final pull to a press tissue (32/42) it»: the following nip . »» • ·: .J 30 »· I * ·»> Φ