FI116400B - Press section in a paper or cardboard machine - Google Patents

Description

116400

The present invention relates to a press or a press machine part of a paper or board machine according to the preamble of claim 1.

The invention relates to a paper or board machine with at least a forming part, a press part and a drying part, in which the press part is provided with separate purifying times. In this application, a separate press nip is meant a press nip in which the opposing press members form only one press nip. The separate press nip may be a roll nip or a long nip. In contrast to a separate press-nip, there is a press with a center roll, where the center roll forms a press nip with at least two other rolls.

15 FI Patent Application 990557 discloses a method and arrangement for treating a paper or paperboard web. Figures 4-6 show the surface characteristics of the web. . mouth control are examples of chemicals and nipples.

In these embodiments, the second and third nip utilize a tandem transfer belt below. The dewatering is not symmetrical, since in the first nip dewatering occurs in both directions, in the other up and in the third, dewatering occurs, but in the ironing and application of the web since the belts are located on both sides of the web. Thus, the third press nip of these applications does not raise the dry matter, although it mimics the surface properties of the web, thereby increasing the overall length of the paper machine.

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Fl-PC Publication 95610 discloses a press section of a paper machine with a balancing press. Through the press section, the paper web has a sealed and supported outlet and the press section comprises at least two successive discrete press nips, at least 30 of which are dewatered from the paper web, preferably between two water-receiving press fabrics. The last press nip of the press section 11 6 4 U ϋ 2 is a separate press nipple separate from the previous nip and does not undergo any significant dewatering. The paper web is led through a balancing press by a nip from a preceding dewatering press nip with a substantially water-inaccessible transfer belt with its substantially straight run which continues after the equalizing nip in a substantially parallel run having a conveyor-compensating nip in the transfer belt.

U.S. Patent No. 6,210,530 discloses a press section and a method of pressing with shoe presses of various lengths. Figure 2 illustrates an embodiment having three shoe press units in which the web is first passed through first and second shoe press units disposed below the counter roll, i.e., below the web, and a third shoe press is disposed above the counter roll, or the web.

15 patent application 981089 discloses a press section of a papermaking machine applying one or more press nips through which the paper web to be pressed is guided substantially closed for export and having at least,. one press nip provided with two water-receiving press felt through which the paper web passes between the press felts and after which the latter nip! The last nip of the press section • ·, · <is the long nip zone, the second roll being a shoe roll with a hose diaphragm and a press shoe system and the second roll a press suction roll with a suction zone. Through the last long nip zone, the paper web is guided between two water-receiving press vents and immediately leads. after our long nip zone, the paper web has been separated from the second press felt and moved, under the pressure of the suction zone of said press suction roll, to follow the press felt on said press suction roll without substantial re-wetting, and the paper web has been by suction roll or similar arrangement.

rtit 11 6 4 ϋ ϋ 3 FI Patent Application 961518 discloses press section geometries in which a press section of a paper or board machine with a closed exit web comprises a first water-receiving upper fabric to which the web is transferred from a pick-up 5 roll suction zone to a pick up roll and then follows a wire drawing roll, from which the wire returns. The press has one or two successive water purge nipples between the web, between which the web has a completely sealed outlet so that it is always profitable for the fabric. The drain nipples are so called. long nipples having a punching zone substantially longer than the sharp roll nip, and each press nip is further provided with two water-receiving press fabrics so that water is discharged substantially symmetrically through both surfaces of the web. Further, the embodiments of Figures 1, 2 and 3 utilize a lightly loaded transfer nip formed by an on-surface press roll fitted with a sil-15 upper fabric, together with a first drying cylinder or the like.

; One problem with press parts known in the art is absorption mismatches. resulting from a change in the thickness composition / structure of the web at each press where less water is removed in both directions due to the leaching of fine and filler material with the water. The fines are enriched, * * in the surface areas of the web where the removal of water has been more intense. The problem may also be affected by the wire section, but the clamp is the last dewatering means that can actually influence the problem. In fine paper, the middle layer 25 is impoverished by the fine material, but the fine layer moves and adheres to the surfaces. t is equal on both sides of the web.

t (<| Surface topography missing marks and absorptions of the top and bottom of the paper, sorption and its asymmetry are a major disadvantage in modern pressed portions; / 30 when applied to printing paper. With speeds greater than 2000 m / min, It is an object of the invention to further develop a closed section press section suitable for speeds above 1800 m / min and preferably above 2000 m / min, which does not have the problems of surface topography and absorption symmetry described above.

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It is an object of the invention to provide a press section of a paper or board machine which is capable of optimizing surface topography and absorption at speeds above 1800 m / min and preferably above 2000 m / min.

In order to achieve the foregoing and further objects, the press section of the invention is essentially characterized by what is set forth in the characterizing section of claim 1.

In a paper or board machine according to the invention, the sealed passage through the press portion 15 in the press portion is effected mainly as a direct flow and the press portion has at least three separate press nipples which do not have common tissue circulation

Ja- •; * In the press section of the invention, the first press nip in the web running direction is a roll nip or press nip roll nip, preferably at lower than 1800. . m / min but with speeds higher than 2000 m / min and water supply. As the peen increases, the long nip becomes an affordable alternative. It is conceivable that with three nips at high speeds, all nips are long nips, and on the other hand, with multiple nips at lower speeds, only telanip 25s can be used. The next two nipples each have only one receiving water. . : a fabric placed on each side of the nipper on the opposite side of • '· · paper in the machine direction. In these sequential nipples, both sides of the web one by one are mechanically smoothed / leveled against a smooth surface which _. the smooth surface may be a smooth roll or transfer belt known from the center roll solution. In this case, • · 30 water is removed from the web in the nip only away from the smooth surface,

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5 on the retrograde tissue side. In such successive nipples, the fines affecting the absorption are applied to both surfaces equally.

The transfer from the press section according to the invention to the drying section is known per se from the transfer belt and in applications where the smooth surface is in the last nip of the press section in the upper position, the transfer from the lower felt is used.

the press section in accordance with the invention, a smooth roller or a transfer belt equipped with siloitus- / tasoitusnipeissä is on the other side of the water-receiving press fabric 10 and a press roll. For lower loading needs, a conventional press roller can be used and for higher loads it is preferable to use a powder metallurgical press roller, whereby the wall thickness of the suction roll need not be increased. For example, the suction of the last iron nipples ensures that the web follows the felt and does not necessarily require heavy loading. Correspondingly, in the initial roll / long nip 15, a powder metallurgical suction roll provides greater dewatering with higher loading. A powder metallurgically manufactured press-suction roll is described, for example, in U.S. Patent No. 100,422. The suction roll ensures that the web is py-: '' on the surface of the porous tissue so that it does not follow the smooth surface of the roll / transfer belt. The smooth surfaces of the press nipples also affect '; · 20 to the web surfaces by mechanically smoothing out the effects of rough press fabrics; 'smoothness reduction. Shoe press may also be used in connection with the invention; . · Mia.

The press member according to the invention provides good web surface properties with respect to printability and also enables high speeds, above 1800 m / min and preferably above 2000 m / min, and good efficiency at high humidity. · · Usprofile.

The press section of the invention also facilitates the subsequent paper machine line. . 30 two-sided adjustment, which can mainly be accomplished by calendering and chemical application. Any sweat lost during compression may

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This can be saved later with lighter calendering which can be optimized for other desired surface properties without the need to correct the absorptivity symmetry. On the other hand, as the press powder rises in more press nips than conventionally, a shorter dry die may possibly be accomplished even though the press member continues.

In a preferred embodiment of the invention, there are three press nipples, a closed passage of the web through the press member, and the first nip has a duplex dewatering to provide a symmetrical web. After the first nip, the web 10 is moved from the surface of the top felt to another press, and in the second nip, the drainage is downward and the top surface of the web either against a smooth roller or against a smooth transfer belt. In the third nip, the dewatering is upward and the underside of the web is against the transfer belt and the web is moved from the lower fabric to the drying section. According to a preferred additional feature, after the first nip, a roll press is placed in a second press, whereby a sufficient material transfer, i.e. a transfer of fines on the underside of the web, is provided in the second nip. At the same time, the smoothness of the upper surface of the web is improved as it is pressed against the smooth surface.

Some embodiments of the invention will now be described with reference to the figures in the accompanying drawings, in which details the invention is not intended to be exclusive; 'restrict.

Figure IA schematically illustrates an embodiment of the invention.

Figure IB schematically illustrates an alternative to the first press nip of the embodiment of the invention of Figure IA.

Figure 2A schematically illustrates another embodiment of the invention.

Figure 2B schematically illustrates an alternative embodiment of the embodiment of the invention of Figure 2A.

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Figure 3 schematically shows a third embodiment of the invention.

In the following figures, like reference numerals 5 are used for like parts.

In FIG. 1A, the web W formed by the forming member is guided to the pick-up point P on the inside of the forming wire loop by the forming wire 10. The pick-up point P is formed between the forming wire 10 and the first water receiving press felt loop 20 wherein the web W passes at the pick-up point P between the forming fabric 10 and the first press felt 20. At the pick-up point P, the web W is detached from the forming wire 10 and transferred to the support of the first press felt 20. Subsequently, the web W is moved in support of the lower surface of the first press felt 20 to a first press nip N1 consisting of two on-press press rolls 22 and 23 into a roll nip N1 or a press nip roll (Fig. IB), the upper roll 22 being a second press suction is on the surface. In this case, felt blanket roll: 25 may be omitted. The web W passes in a first press nip N1 against a first water receiving press felt 20 acting as an upper press fabric and a first water receiving a lower press fabric acting as a lower press fabric; * between retraction press felt 21. Dewatering from the web W takes place in the first press nip N1 to each press felt 20, 21. In applications where a press suction roll is used, water is also discharged through the suction zone to the suction roll.

After the first press nip N1, the passage of the web W with the upper press felt • · 20 is secured through the vacuum of the suction zone 25a of the upper suction roll 25 and the web W is removed from the first press felt 20 below. . 30 by means of vacuum of the suction zone 34a of the transfer suction roll 34 and is gripped to the underside '. A second press fabric 30, which may also be a press felt, on whose upper surface 11 6 4 υ ϋ 8 the web W is transferred to a second press nip N2 formed between a smooth roll 32 and a press suction roll 33 having a suction zone 33a. The suction zone 33a of the suction roll 33 is preferably high sector and high vacuum, ensuring that the web is adhered to the desired felt even before and after the nip, so that the web does not follow the smooth roll. The web W is then moved in the support of the second press fabric 30 and transferred via the suction zone 44a of the transfer suction roll 44 to the support of the next upper press felt 40 and to the third press nip N3 formed between the long nip press roll 42 and the counter roll 43. Below, there is a transfer belt 41 through which the web W is guided to a transfer suction roll 54 through which suction zone 54a is transferred to the drying fabric 50 of the drying section. Dewatering from the web W takes place in the third press nip N3 to the upper press felt 40.

The embodiment shown in Fig. 2A corresponds substantially to the embodiment illustrated in connection with Fig. 1A and its variants, but in the embodiment of Fig. 2A, the second press nip N2 is formed such that the second nip 42 has an upper transfer belt 31 and a lower fabric 30 From the second press nip N2, the web W is guided on the underside of the transfer belt: '* 31 to the transfer fabric 60 on which the web W is transferred to the suction roll of the transfer suction roller 64 ♦: ·:! Through 20 zones 64a and the support of the felt 60, the web W is guided to be moved to the support of the upper fabric 40 of the third press nip N3 through the suction zone 44a of the suction roll 44 '.

The embodiment of the invention shown in Figure 2B corresponds essentially to the embodiment shown in Figure 2A. . 25 rolls except that each nip N1, N2, N3 is formed as a long nip, wherein the second roll is a long nip roll 22; 33; 42 and the second roll thereof 23; 32; 43.

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* ♦ »· ;; Fig. 3 illustrates an embodiment of the invention in which the web W is guided to form; from the tuft forming wire 10 before the pivoting roll 11 to the pick-up position P where the web:. ; 30 W is led to the support of the first water receiving press felt 20: through suction zone 24a of suction roll 24 and web W is led to a first 1 1 6 4 ϋ Li 9 press nip N1 formed between two on-press press rolls 22, 23 or between a press suction roll and on-press press roll ). The lower press felt 21 is also a water-receiving. Retention on the surface of the lower press felt 21 is ensured through the vacuum of the suction zone 5a of the transfer suction roll 26 and the web W is led to the support of the upper press felt 31 of the second press nip N2 via the suction zone 35a of the suction roll 35. The second press nip N2 is formed as a long nip press between the long nip roll 32 and the return roll 33. The lower fabric in this press nip N2 is a water-receiving press felt 30. In its support, the web W is guided to a transfer suction roll 10 44, through which suction zone 44a is pressurized to support between the smooth roller 43. The roll 42 is a press suction roll provided with a suction zone 42a. Dewatering takes place in the suction zone 42a of the suction roll. From the felt 40, the web is led to the next felt 70 via the vacuum of the suction zone 74a of the suction roll 74 and through the felt 70 to the next ironing nip N4 formed between the press suction roll 73 and the smooth roll 72. The suction zones 42a and 73a of suction rolls 42 and 73 are preferably high sector and high vacuum, ensuring that the web: '1 · adheres to the desired felt even before and after the nip, following the felt to prevent the web from following the smooth roll. The web W is then guided • »

* ··· 1 for the dryer section to support the dryer wire 50 as shown in Figures IA and 2A above

* · '·' Explained. The embodiment of Fig. 3 can also be implemented by placing only one press nip in each direction prior to the iron press nipples N3, N4, in which case the first press. N1 may be formed by a shoe roll and a toe-like roll. nipple or nipple • • · ",!, 1 hand and squeegee roll.

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·; · 1 · The invention has been described above only in some preferred embodiments thereof; · With reference to details of which, however, the invention is in no way intended to:.:: 30 narrowly limit.

Claims (18)

1. Press section of a paper or cardboard machine in which the press section drawn by the web (W) is realized as a closed pull through the press section as a substantially straight race and which press section is provided with at least three separate press nips (N1, N2, N3; N4 ), of which the first nip (N1) has two-sided dewatering, and which press nip each has its own tissue circulation (20,21; 30,31; 40,41; 70), and the nip following the first nip (N1) (N2, N3; N4) has a water-receiving tissue (30.40; 70) positioned in the nip (N2, N3) relative to the second opposite side of the web (W) in the running direction of the machine web, characterized therein. that the last two of the nip (N2, N3; N4) following the first nip (N1) are so-called smoothing or smoothing nip, wherein the relative side of the web (W) is relative to the water-receiving tissue. arranged to be smoothed against either a sieve roll (32,43,72) or a transfer belt (31,41). 15 2. Press section according to claim 1, characterized in that the press section is arranged to be used at running speeds above 1800 m / min. ; . Press section according to Claim 1, characterized in that the press section is arranged to be used at running speeds above 2000 m / min. • · · t'_ i 4. Press section according to claim 1 or 2, characterized in that the first * in ·. The press nip (N 1) is a roll nip (22,23) or a press roll nip. • »: 25 5. Press section according to claim 1 or 2, characterized in that the first "nip" (N 1) is a long nip or a long / suction nip. . 6. Press section according to claim 1 or 2, characterized in that all nips (N1, N2, N3) are long nips. , **; 30 Press section according to any one of claims 1 to 6, characterized in that the relative side of the surface of the 1164ϋϋ web (W), relative to the water-receiving tissue (30.40), is arranged to be smoothed against either a slat roller (32) or a transfer band (31, 41) in the nip (N2, N3; N4) following the first nip (N1), the so-called smoothing or smoothing nip. Pressing section according to any of claims 1 to 6, characterized in that after the first nip (N1) in the pressing section follows a longitudinal nip (N2) and two smoothing nips (N3, N4). Press section according to claim 7 or 8, characterized in that at least one of the rolls in the two first nip (N1, N2) is a long nip roll. Press section according to claim 8, characterized in that all nips (N1, N2, N3, N4) in the pressing section are roller nips. Press section according to any of claims 7 - 10, characterized in that the press roll (33, 42,73) in the smoothing / equalizing nip (N 2; N 3; N 4) is a powder metallurgically manufactured press roll. 12. Press section according to any one of claims 1-11, characterized in that the press roll (22) in the press nip (N 1) is a powder metallurgically manufactured press roll. Press section according to any one of claims 1 to 11, characterized in that the cutter one of the rolls in the press nip (N1, N2, N3, N4) is a press roll. Press section according to any of claims 1-9 or 11-12, characterized in that at least one of the nips following the first nip (N1) is a longitudinal nip; 'Nip or a shoe press nip. Il » 15. 'Press portion' according to any of the preceding claims, characterized in that: the web (W) after the first nip (N1) is arranged to be transferred from the surface of the 116400 upper felt (20) in the first nip (N 1) to the next lower tissue / felt (30) in the press. Press section according to any of the preceding claims, characterized in that the dewatering takes place in the second press nip (N2) and the upper surface of the male (W) abuts either a sealed roller (43) or a smooth transfer belt (41). and that the dewatering in the third nip (N3) occurs uptight and the lower surface of the male (W) abuts a transfer belt (41). Press section according to any of the preceding claims, characterized in that the male (W) is arranged to be transferred from the last lower tissue circulation in the press section in a final pull to a drying wire (50) in the drying section. Press section according to any of the preceding claims, characterized in that the smoothing nip provided with a tissue-free counter roll has a large sector press roll, which sector starts before the nip and continues thereafter, on which the male is arranged to follow the press felt before the nip , during the nip process and after that. * 4 · 1 t * I