FI122167B - Arrangements in connection with the press section and the dryer section in a sheet forming machine - Google Patents

Description

ARRANGEMENT ON THE CLAMBER AND DRYING MACHINE

The invention relates to an arrangement in connection with a press section and a drying section of a forming machine comprising first means for conveying a web to be formed on a forming machine, a further means for conveying a web which is provided with a drying fabric. , wherein the arrangement has an open space between the first and second means, over which the web is arranged to be moved from the first means to the drying wire in a vacuum-depressed region of rolls 15, where the web and the drying wire form a closing web.

Even in modern web-forming machines, there are still points where the web is passed over an open space. Such a point is, for example, between the press part of the forming machine and the drying part. In one known problem, from the surface of the press roll included in the press section, the web is guided to a drying wire belonging to the drying section. The drying wire is arranged as a loop, one of which is supported by one of the rolls in the vicinity of the press wire. In practice, the web is guided to a drying wire at the roll. In addition, a closure gap is formed between the web and the dry wire on the surface of the roll. Supported by the drying wire, the web passes through the drying section.

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f-30 At one end of the endless loop of the first dryer wire, the web is transferred to the next dryer wire. Paluukierrolla

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the drying fabric is empty and eventually passes again through a roll fitted in the vicinity of the press roll co. Particularly in the return cycle, co 35 ends up in the closing friction forming the web and the drying wire. Part of the air is discharged from the stake upwards and through the drying wire into the vacuum. However, the amount of air is so g the drying fabric carries with it a layer of air which eventually

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2 that a considerable overpressure is created in the friction, which bulges the web and especially the looser edges of the web onto the bag. The transverse bulging of the web forming machine is vague, which interferes with the web flow. The overpressure also generates transverse currents which cause the web to flutter. Bagging and vague movement stretch the web and reduce its quality. The problem has been avoided by tightening the web by rotating the drying section at a higher speed than the pressing section. However, with the current high speed web-forming machine 10, increasing the speed difference is difficult. In addition, at high speeds, even a small relative change in velocity produces a large absolute change, which causes varying longitudinal forces on the web. In this case, the motion of the web becomes jerky and the bagging problem occurs at least 15 times. At the same time, the breakage sensitivity of the forming machine increases, thereby reducing overall production.

U.S. Patent 5,355,593 discloses a device for transferring a web from a press section to a dry end of a papermaking machine. The web contacts 20 rotating press surfaces, such as a press roll, and passes through a press surface through a press nip against a counter roll, and then passes through a press surface to a web removal point. The web is moved by a suction device across an adjustable gap to a porous transfer belt that conveys the web toward the first 25 drying groups. The first drying group comprises a plurality of drying cylinders and a web support belt which transfers the web from the drying cylinder to the drying cylinder. Either suction device or whatever

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the intermediate transfer roller transfers the drying group from the web transfer belt

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rainantuentahihnalle. The speed control device controls the press surface

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30, use of the transfer belt, and the use of the first drying cylinder group and its web support belt, such that there is a positive speed difference between the press nip pin and the transfer belt and the transfer belt and web support belt.

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It is an object of the invention to provide a novel arrangement which avoids fluttering and bagging of the web. Characteristic features of this 3 invention are apparent from the appended claims. The arrangement according to the invention prevents the air layer from passing into the closing pore. In this case, the pressure is substantially the same on both sides of the web, whereby the web passage 5 remains stable. The arrangement can be assembled from different components, thus avoiding the problem at each position. In addition, the amount and dimensioning of the components can simply be controlled by the amount of air removed.

The invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 is a plan view, side view, of the arrangement of the invention;

Fig. 2a is a plan view of a side view of another embodiment of the arrangement according to the invention,

Figure 2b is a plan view of a third embodiment of the arrangement of the invention, viewed from the side.

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Figure 1 illustrates an arrangement according to the invention in connection with a press section and a drying section of a forming machine. This arrangement includes, by means of a press section, first means 10 for conveying the web 11 to be manufactured on a web forming machine. In Fig. 25, the clamping member and the drying member are only partially shown. By means of a press section, the web 11 is conveyed by a press felt 12 which is guided through a press nail forming two press rolls 13 and 14.

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? pin. The press felt 12 is an endless loop and is co-supported by folding rollers 15 on the structure of the forming machine.

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Correspondingly, the drying section has second means 16 for further conveying the web 11 to be produced by a forming machine, here the other means 16 include a drying wire 17 and

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a roller 18 adapted to support said roller 18 is further provided with a vacuum to maintain the web 11 with the drying wire 35 17. In the arrangement there is an open space 19 between the first and second means 10 and 16, over which the web is arranged. be displaceable. 1, the free space 19 has a web 11 running from the surface of the press roll 14 to a dryer wire 17. Thus, the press 11 from the press roll 14 is guided to the area of the vacuum press 18 where the web 11 and the dryer wire 17 form a closing web 20.

According to the invention, the arrangement further comprises a blocking means 21 in the running direction of the drying wire 17 before the open space 19, which is disposed on the opposite side of the roll 18 18 of the loop formed from the drying wire 17 (Figs. Further, the barrier means is arranged near the dryer wire to limit the air layer carried with the dryer wire and thus prevent the formation of overpressure in said sealing piston. Thus, a substantial part of the air layer carried by the dryer wire is removed or otherwise diverted by the barrier lines. Especially on the outside of the loop, the air layer grows significant in the above positions, causing problems in the clearance.

The amount of air carried by the dryer wire is affected by a number of factors, the most notable of which is the speed and free length of the dryer wire. The air near the surface of the drying wire proceeds at the speed of the drying wire and the boundary layer tends to grow continuously. To achieve a sufficient barrier effect, the barrier means should be spaced a maximum of 25 by 50 mm. However, it is preferable to place the barrier means closer to the drying wire, whereby an increasing proportion of the boundary layer, and in particular its fast-moving portion,

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can be removed. Significant

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their location with respect to the closing kid. In general, it is advantageous to install the x £ 30 barrier means as close as possible to the gap, thereby preventing the formation of a new boundary layer. In other words, the formation length remains advantageously short. According to the invention, the distance of the barrier means between the contact between the roll and the dryer wire

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is less than 3000 mm, more preferably 50 to 1500 mm. 35 In this case, the barrier air bounded by the barrier means can no longer grow again before the friction.

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The air layer can be limited in different ways. In general, according to the invention, the barrier means are arranged to be passive or active. Active blocking means consist of members or airflow devices adapted to move or rotate. In Fig. 15, the barrier means 21 is the aforementioned press felt 12 which advances against the direction of movement of the drying wire 17. The pressing felt proceeds almost at a still high speed, but in the opposite direction to that of the drying wire, whereby the removal of the air layer is very effective. Also shown in Fig. 2b is an active blocking means 21 which here is a rotary auxiliary roll 22. Preferably, the auxiliary roll is rotated against the direction of movement of the drying wire. In practice, the effect of active barrier means has a certain reach. However, efforts are made to place the barrier means as close as possible to the drying wire. According to the invention, the distance between the active barrier means and the drying wire is 1 to 50, more preferably 3 to 12 mm. In this case, the effect of the barrier means extends as far as the drying wire, whereby a substantial part of the air layer can be removed.

Similarly, passive barrier means consist of air guides 20 or scrapers. The passive barrier means lack the reach, so they must be placed closer to the drying wire than the active barrier means. According to the invention, the distance between the passive barrier means and the drying wire is 1 to 50, more preferably 1 to 6 mm. For example, scrapers can even be attached to a drying 25 wire. However, the contact barrier means require maintenance and may wear the dryer wire, even if made, to the shape of the surface that it may touch. Figure

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? 2a illustrates an air deflector 23 for directing a significant portion of the air bed layer away from the surface of the drying wire. Especially passive x £ 30 air deflectors are easy to install in series. The air layer is then removed gradually. The air deflectors can also be combined with, for example, a vacuum to remove air from the co o position. Active and passive barrier means may also be combined or positioned sequentially so as to prevent as much as possible of the boundary air layers 35 from entering the closing friction.

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The dryer fabric also carries some air along its inner surface. This air passes through the closing wire formed by the drying wire and the roll and from there through the drying wire outside the loop. Any excess air causes problems in the 5 clearances, so the arrangement further includes runnability components arranged inside the loop formed by the drying wire. The runnability components are advantageously placed in connection with the roll and are adapted to limit the air layer traveling with the inner surface of the dryer wire. This prevents overpressure 10 from forming in the closing wire formed by the dryer wire and roll and the air penetrating through the dryer wire. In Fig. 2a, the runnability component 24 is a blower box 25 for providing a blast limiting air within the loop. There may also be a second blow in the lower corner of the suction box 15 to provide a vacuum on the inside of the loop which is pulled onto the drying wire on the underside of the dryer wire. The same components can be used on the inside of the loop as on the outside of the loop, although there is limited installation space. On the other hand, passive air deflectors require only 20 small installation spaces.

Figures 1 and 2a show as a roll 18 a conventional suction roll with a suction zone defined by seals 26 formed therein. Through the perforated sheath of the suction roll, the vacuum effect 25 is applied through the drying wire to the web, which is thus made to follow the drying wire. In Fig. 2b, the vacuum zone is delimited by a special suction box 27 which is sealed by the suction roll 18? to the surface. In this case, a larger part of the suction roll diaper co can be vacuumed. At the same time, it is easy to connect the suction box 27 to the airflow limiting blows or air-to-air frosters 28.

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co capacity building. In practice, however, the situation 35 has become impossible. The vacuum must be maintained at a certain level set by the properties of the web. Correspondingly, the diaphragm § In principle, the boundary layer of air could be removed from the suction roll.

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7 openness is already optimized and, on the other hand, it is often impossible to increase the diameter of the diaper due to space constraints. Increasing the suction roll also increases costs. Thus, according to the invention, the air layer or at least a significant part thereof is removed before the open space. The suction roll can then be adjusted to operate according to the web control, and there is still capacity left to remove the remaining excess air. Preferably, the arrangement is set so that air is disrupted in a controlled manner and thus avoids airflow disturbing the passage of the web. The amount of barrier means 10 and their distance from the drying wire and the barb are adjusted on a case-by-case basis. In practice, the amount of air removed by the suction roller depends on these factors. Thus, an effective barrier device placed close to the drying wire and the closing sheath removes the air layer almost completely, thereby preventing the build-up of overpressure in the sheath.

In Figures 2a and 2b, the direction and magnitude of the outer boundary layer of the loop are illustrated by solid arrows. Similarly, the direction and magnitude of the boundary air layer inside the loop are illustrated by dashed arrows. The drying wire is represented by a dashed line and the web by a dotted line. In reality, the web is attached to the drying fabric, but for clarity, the web is shown loose from the drying fabric.

Particular attention must be paid to the placement of active barrier means near the drying fabric. In particular, it is advantageous to make the press felt and the dryer fabric meet at a great angle, whereby the fabric passes a short distance apart. In addition

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it is advantageous to set the tissue support rolls as far as possible

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£ 30 close to each other for low tissue living. Hereby, the barrier means is preferably brought near the drying wire, whereby

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provides effective removal of the boundary layer. Despite the short distances, non-contact barrier devices are wear-resistant

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and can be implemented even at no additional cost with proactive 35 design.

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The arrangement according to the invention is suitable for all types of production and for various positions. The boundary layer can be removed in various ways and sufficient exhaust capacity is obtained in each case. The arrangement is also advantageous to implement and its capacity 5 can simply be increased, for example, as the production rate increases. In addition, the arrangement is effected by known suction rolls when the passage of the boundary air layer is restricted before the friction or completely removed. In this way, the flow of the web is smooth and production and quality problems are avoided.

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Claims (8)

An arrangement adjacent to the press portion and drying portion of a sheet forming machine, comprising: - in the press section, first devices (10) for transporting the web (11) produced by the sheet forming machine, in the drying portion other devices (16) for further transport of the web (11) produced by the sheet forming machine, the second devices (12) including a drying wire (17) and one for supporting this arranged roller (18), within which there has been provided suppression, in which arrangement it is between the first and second devices. (10, 16) is an open space (19) over which the web (11) is arranged to be moved from the first devices 15 (10) to the drying wire (17) in the region of negative pressure of the roller (18), where the web (11) and the drying wire (17) form a closing gap (20) and the arrangement further comprises a loop formed by the drying wire (17) on the opposite side of the roller (18) and barriers (21) before the open space (19). in the drying direction of the drying wire (17), which are arranged near the drying wire (17) for limiting the air layer moving with the drying wire (17) and thereby preventing an overpressure being formed in said closing gap (20), and the arrangement further comprises within the loop formed by the drying wire (17), adjacent to the roll (18), are provided runability components (24) which are arranged to limit the air layer moving with the inner surface of the drying wire (17) and thus prevent the formation of an overpressure. the closing gap formed by the drying wire (17) and the roller (18), characterized in that the distance of the CD obstacle devices (21) from the drying wire (17) is 1 to 12 x 30 mm, and the executability components (24) comprise at least one blow-out device. then (25). LO co o Arrangement according to claim 1, characterized in that the distance of the barrier devices (21) from the contact point of the roller (18) and the drying wire (17) is less than 3000 mm, more preferably 50 - 1500 mm. Arrangement according to claim 1 or 2, characterized in that the obstacle devices (21) are arranged passively or actively. 4. Arrangement according to claim 3, characterized in that 5 active obstacle means (21) consist of means (22) arranged to move or rotate or of air flow devices. 5. Arrangement according to claim 3, characterized in that passive obstacle devices (21) consist of air conductors (23) or ίο of scribes. Arrangement according to claim 3 or 4, characterized in that the distance from the active barrier devices (21) from the drying wire (17) is 3 - 12 mm. 15 Arrangement according to claim 3 or 5, characterized in that the distance of the passive obstacle devices (21) from the drying wire (17) is 1 - 6 mm. Arrangement according to any of claims 1-7, characterized in that suppression devices (26, 27) for providing suppression are provided at least in part of the perforating jacket included in the roll (18) in connection with the roller (18). circumference. δ CM CD O CD X cc CL 00 δ co o o CM