FI126248B - Method and arrangement for head export with the drying section of a fibrous web machine - Google Patents

Description

METHOD AND COMPOSITION IN DRAWING ON THE DRY TYPE OF A FIBER MACHINE

The invention relates to a method of threading a drying section of a fiber web machine, wherein the drying wire is alternately supported by drying cylinders and rotating rolls as a single wire thread, and the pocket space defined by the turning roll and two drying in connection with the blowing, a channel which is sealed at the machine-directional edges to the turning roll is restricted to the swivel roll, and the channel is limited by sealing members which are fitted in contact with the drying wire; The invention also relates to an arrangement for threading the dryer section of a fiber web machine.

In the drying section of fiber web machines, such as paper or board machines, so-called single-wire threading is used. In single-wire delivery, steam-heated drying cylinders and swivel rolls alternate with supporting the drying wire. In the pocket space limited by the drying cylinders and the swivel roller together with the drying wire, a runnability component is also provided for depressurizing the pocket space. The runnability components are used during manufacture to prevent, for example, the web from detaching from the pivot roll and flattening the edge portions of the web. At the start of production, the threading is carried out using a threading strap.

The web to be manufactured in a single wire feeder is located on the surface of the drying wire at the swivel roll. Thus, centrifugal force tends to release the web from the surface of the drying wire. To prevent this, a vacuum roller, also called a vac roller, is used as the roller roller. In addition to the Vac roll, the closing wire formed by the drying wire and the turning roll has been attempted to create a blower-enhanced vacuum. In the known solutions, the vacuum has been insufficient, especially with regard to the headband. In other words, despite the underpressure of the closing kid and the vac roll, the tongue strap loosens at the pivoting roll from the surface of the drying wire, whereby the tapping thread fails. Thus, the speed of the fiber web machine during production and especially during threading has had to be limited. In addition, the blast brings a lot of air into the closing friction, which hinders the function of the runner component, especially in the headstroke. On the other hand, switching to cordless tapping in machine rebuilds has required costly investment in vac rolls and runnability components. Nonetheless, headache is still a critical step and in practice very uncertain.

U.S. Patent No. 4,422,231 discloses an air control box for a drying section of a paper machine. The air control box is located between two successive drying cylinders along an endless support fabric. WO Publication No. 2011/076251 discloses a runnability component.

It is an object of the invention to provide a new method and arrangement for threading the head of a fiber web machine, which is more reliable and enables the operation to be threaded safely. Characteristic features of the method according to the invention are that in the direction of rotation of the swivel roll, a transverse sealing surface is provided at the beginning of the extension against the drying wire, and the sealing members are also arranged in contact with the swivel roll. Correspondingly, the arrangement according to the invention is characterized in that in the direction of rotation of the swivel roll at the beginning of the extension there is a transverse sealing surface against the drying wire, and the sealing members are also arranged in contact with the swivel roll. The sealing members are strips narrower in length, oriented substantially in the longitudinal direction of the fiber web machine. Thanks to the channel, an enhanced vacuum can be formed in the deeper closure pith, whereby the threading strap is sure to follow and remain on the drying wire. Enhanced vacuum is required for a short period of time, while maintaining moderate power consumption. In addition, due to the duct, the required amount of blowing is small. This also reduces the amount of air entering the pocket space, thus keeping the runnability component running smoothly.

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

Figure 1 is a side view of a fiber web machine,

Figure 2a is a schematic drawing of one drying section of a fiber web machine drying section with runnability components,

Fig. 2b shows an arrangement according to the invention during the head insertion,

Figure 3a shows a partial magnification of Figure 2b,

Figure 3b is a schematic drawing showing the main components of an arrangement according to the invention.

Figure 1 is a side view of one fiber web machine 10 known per se. The fiber web machine 10 comprises, in successive subassemblies, a wire section 11, a press section 12, a drying section 13 and a post-treatment section 14. In the fiber web machine of Fig. 1, only the machine reel is included in the post-processing section. The drying section 13 comprises a plurality of successive drying groups 15, which have nine pieces in the fiber web machine of Figure 1.

Fig. 2a shows separately one drying group 15, which are several in succession in the drying section of a fiber web machine, as described above. The drying group consists of drying cylinders 16 and turning rollers 17 through which the drying wire 18 is guided as an endless loop. Nowadays, the use of the single-wire export as described, with only one drying wire per drying group, is increasingly used. In practice, the web runs between the drying wire and the heated drying cylinder. Correspondingly, the roll roll-la web passes over the drying wire. In addition, the runner component uses a runnability component 19, which is placed in a pocket space 20 formed by successive drying cylinders and a pivoting roll. Fig. 2a shows runnable components with obliterated end plates controlling the air flows at the edge portions of the web. In addition, Figure 2a shows only the drying fabric 18 without the threading strap.

In Fig. 2b, the runnability component 19 is shown without the end plate. Here, the runnability component 19 is a blow box. The blower box has blowing nozzles in the transverse direction of the fiber web machine both on the inlet side and on the outlet side. The so-called high vacuum region is delimited with respect to the normal vacuum pocket space by a vacuum divider disposed in a transverse direction of the fiber web machine, and is vacuum-suctioned. The disclosed runnability component is for use during production, wherein the web covers the dryer wire, preventing leakage through the dryer wire into the runner component.

Figure 2b also shows the blowing means 23 provided in the opening kite 21 defined by the drying cylinder 16 and the drying wire 17 for removing the threading strap 22. The release blow is used to blow the end of the threading strip 22 from the drying cylinder 16 and direct it to follow the drying wire 18. The release blows are in use during the threading and in the case of Fig. 2b, the end of the threading strip 22 has Despite detachment blows, headaches have encountered problems, especially with the swivel roller and in-group intervals. In particular, the retention of the thread on the surface of the drying wire at the swivel roll has been uncertain.

The invention thus relates to a method of threading a dryer section of a fiber web machine. In the dryer section, the drying wire 18 is alternately supported by the drying cylinders 16 and the rotating rollers 17 as a single wire export. That is, the dryer section 18 is alternately supported by the drying rollers 16 and the rotating rollers 17 to form a single wire thread. In addition, the pocket la 20 defined by the rotating roll 17 and the two drying cylinders 16 together with the drying wire 18 is vacuumed. To this end, a runnability component 19 is provided in the pocket space 20 defined by the pivoting roller 17 and the two drying cylinders 16. Thus, the arrangement includes blowing means 25 which are provided on the closing flap 26 formed by the drying wire 18 and the turning roll 17 to create an enhanced vacuum in the head passage. In the embodiment shown, the channel 27 (Fig. 3a) is closed against the pivoting roller 26 and the blast 24, which is sealed at the machine-facing edges with the pivoting roller 17. In other words, the arrangement includes a channel blowing means 25 are provided and include machine direction sealing means 29 for sealing the channel 27 at the edges to the pivot roll 17.

The above solution achieves many advantages. Perhaps the most important of these is the remarkably high vacuum effect in a very deeply closed kidney. To achieve this, the channel 27 of the invention formed against the pivoting cylinder 17 contributes. The turning cylinder 17 on the opposite side of the duct 27 is limited by the flow surface 28 on which the blowing 24 is arranged to open. In this case, the blowing creates a venturi effect, which takes the air from the closing gutter as it passes, thereby providing a significant vacuum effect on the front portion of the duct and especially on the front thereof. In addition, the seals at the edges of the channel control the blowing while preventing the vacuum effect from escaping. This further enhances the vacuum in the closing kidney. Figure 2b shows, in principle, an arrangement contained in a channel according to the invention, supported on the runnability component 19.

Figure 3a illustrates in more detail the arrangement according to the invention. In this direction of rotation of the rotating roller 17, an extension 30 (Fig. 3b) is arranged in the channel 27, which is arranged open towards the drying wire 18. In this case, firstly, the vacuum effect extends ever deeper into the closing friction. In addition, the vacuum effect is also exerted on the drying wire 18 and through it to the threading belt 22. This tightly secures the threading belt to the dryer wire as early and as soon as possible at the problematic point, i.e. the junction of the dryer wire and the roller. With the extension in such a deep-closing kid, the vacuum effect no longer escapes anywhere. In this case, the threading strap will be securely held on top of the drying wire for the entire length of the turning roll, whereby the threading is guaranteed to be successful.

The escape of the vacuum effect is also prevented by sealing the channel 27 in the machine direction with its partial travel also against the drying wire 18. Specifically, in the direction of rotation of the swivel roll 17, at the beginning of the extension 30 there is a transverse sealing surface 31 against the drying wire 18. Figure 3b illustrates the arrangement in a simplified manner. Also in this direction of rotation of the rotating roll 17, the channel 27 includes an extension 30 which is open towards the drying wire 18. In practice, the extension consists of edge seals 32, which can and in practice even touch both the swivel roll and the drying wire. Figure 3b also shows the aforementioned sealing surface 31 which extends between the rim seals 32. The sealing surface is thus substantially in the transverse direction of the fiber web machine, but having a longitudinal dimension of the fiber web machine. In Fig. 3b, the edge seal 32 is shown with a dashed line and is shaped according to the curvature of the pivot roll 17.

In the embodiment shown, the flow surface 28 is formed of a plate structure 33 supported on the runnability component 19. Thus, separate support structures are unnecessary and the flow surface is precisely located at the desired location. The board structure is lightweight and requires little installation space. In addition, the sheet material is easy to format. Preferably, the arrangement within the plate structure is supported on one edge, whereby the attachment is at the end of the runner component. This facilitates mounting and possible adjustment. In the embodiment shown, the plate structure is curved and dimensioned so that the distance between the plate structure and the pivoting roll increases slightly in the direction of blowing. In addition, the edges of the sheet structure are bent upwards. The sheet structure then becomes rigid and the edge seals 32 can be secured to the sheet structure 33 to form a compact and sturdy structure.

As the sheet structure and edge seals form the assembly, the sheet structure remains off the surface of the swivel roll. At the same time, the size of the formed channel remains substantially unchanged. Here, the blowing means 25 are arranged to open on the side of the pivot roll 17 of the plate structure 33 and include a blowing chamber 34 which extends over the entire width of the channel 27. The blowing chamber evens out the pressurized air and is provided with openings which open to the pivot roll 17 on the plate structure 33. The resulting blowing 24 then proceeds along the flow surface 28 in the passageway 27 against the rotational movement of the pivot roll 17.

Compressed air is supplied to the blowing chamber 34 via a machine alignment link 35 (dotted line). Similarly, the balancing connection 35 is connected to a larger compressed air connection 36, which is connected to the compressed air system of the fiber web machine. This allows the height of the arrangement to be kept low and the compressed air assembly to be utilized to support the sheet structure and edge seals. As shown in Figure 3b, the blowing chamber 34 is off the surface of the pivot roll 17. In this case, the blowing 24 disposed in the duct 27 draws air with it. This draft extends to the aforementioned extension 30 below the blowing chamber 34. Since the seals prevent the supply of replacement air, a significant vacuum is created at this point. This is represented by the minus circles in Figure 3b. In this case, as the tongue-and-ribbon arrives towards the roller roll, immediately after the sealing surface, it is subjected to a strong vacuum effect which binds the tongue-strap to the drying wire. Regardless of the permeability of the dryer fabric, the vacuum remains inside the dryer fabric while holding the thread strap. Thus, the tuft-strap stays at the pivoting roll on the surface of the dryer wire, without loosening up to the next closing pivot or group gap transfer device, whereby the tapping thread is successful.

Fig. 3a illustrates the blowing 24 which is finally released from the channel 27 towards the runnability component 19. Here, in addition to the boundary layer air on the surface of the pivoting roller 17, 38). The boundary layer air moving on the surface of the swivel roller is prevented by the scraper from entering the duct, whereby the blowing in the duct remains undisturbed and the vacuum effect can be formed with a small amount of air. This contributes to reducing interference with the runnability component. The scraper blade may be preceded by air guides that direct the discharge from the duct to the side if there is a lack of flow across the scraper.

The vacuum effect produced by the arrangement according to the invention is so significant that the cordless tapping is successful even if the swivel roll is smooth or even suction-free. This allows you to switch to cordless tapping without investing in expensive groove or vac rolls. On the other hand, with vac rollers, the arrangement can easily ensure a successful threading and increase the threading speed.

In the embodiment shown, the boosted vacuum is formed by blowing. The ventilation is easy to control and the required components require little installation space. Further, it has been found that significant vacuum can be achieved with surprisingly low overpressure and low flow. This is facilitated by a shallow and compacted channel. In practice, the distance of the channel flow surface from the surface of the swivel roll is, for example, 5-15 mm. The expansion chamber is even closer to the swivel roll. Although the boundary layer air is prevented from entering the closing pith, the blowing is adapted so that the blowing speed is greater than the peripheral speed of the incoming swivel roll. Thus, the blowing can escape from the duct, and the venturi effect occurs. In the invention, the blowing 24 is formed with compressed air having a pressure of 10 to 60 kPa, preferably 10 to 30 kPa. Thus, at a surprisingly low pressure level, significant vacuum is achieved. At the same time, the air consumption is only a few tens of liters per second, which is equivalent to conventional detachment blowing. Based on the measurements, a vacuum of 500 to 6000 Pa is then achieved regardless of whether the pivoting roller is rotating or whether the threading strap is at the channel. Thus, the arrangement works in all circumstances. For example, at a pressure of 30 kPa, a vacuum of about 3000 Pa without the headband and about 4,600 Pa with the headband was achieved under static conditions. With the same blow of 30 kPa, a vacuum pressure of about 2200 Pa and about 675 m / min at a web speed of about 1800 Pa without a headband was achieved. The vacuum levels thus achieved are up to ten times higher than those known. In addition, test measurements showed that the coverage of the headband does not add significantly to the resulting vacuum. In practice, there is so little air passing through the dryer wire that its effect on the vacuum is negligible. In this case, a significant vacuum effect is achieved by blowing, which immediately captures the headband. In addition, even the rotation of the swivel roller has little effect on the resulting vacuum when the boundary layer air is prevented from entering the closing friction. Thus, the arrangement according to the invention provides momentarily significantly higher vacuum for a deeper closure pith, whereby the threading is safe in all situations.

The channel may, for example, have a width of 400 to 500 mm and a margin of about 200 mm, with a thickness of about 10 mm. the length of the enhanced vacuum zone is about 30 mm and the distance between the rounded ends of the beads is less than 200 mm from the point of contact of the drying wire and the roller.

After the head insertion, the blowing can be stopped, but the duct and its seals remain in place. The effective vacuum in the head turn pulls the dryer wire to the edge seals, which at the same time rub the surface of the swivel roll. Thus, Teflon or Teflon-coated seals are preferably used which can withstand wear without wiping the drying wire. When the vacuum is released, the load is relieved and the drying fabric is released from the edge seals. At the same time, the load on the swivel roller is reduced. Thus, the seals remain wear-resistant for extended periods of time and do not wear out the drying fabric, even though the duct is permanently mounted on the runnability component. Preferably, blowing is used only when needed. For example, at the beginning of the headflow, air is directed, for example, to the first two drying groups only. For other drying groups, enhanced vacuum is not yet required as the end of the threading strap is just about to come. As the threading strap progresses, new drying groups are opened for use and, consequently, the blows are closed where the threading strap already covers the drying fabric.

With the method and arrangement of the invention, the threading can surely be carried out even over a suction-free and smooth swivel roll in a single-wire thread. Even with a small amount of air, a significant vacuum is obtained, which is furthermore optimally positioned in the deep-closing friction. It is also surprising that the vacuum is stored in the dryer fabric, whereby the tapping thread remains on the surface of the dryer wire despite the centrifugal forces.

Claims (9)

A method of threading a drying section of a fiber web machine, wherein the drying fabric (18) is alternately supported by drying cylinders (16) and rotating rollers (17) as a single wire thread, and a pocket space defined by the rotating roller (17) and two drying cylinders (16). (20) is vacuum pressed, and in the head insertion, a vacuum-intensified vacuum (24) is formed on the closing wire (26) formed by the drying wire (18) and the turning roll (17), and the channel (17) is restricted against the turning roll (17) 27) which is sealed at the machine-facing edges into a pivoting roll (17), and the passage (27) is limited by sealing members (29) adapted to contact with the drying wire (18), and an extension (30) is arranged in the passage (27) towards the drying wire (18), characterized in that in the direction of rotation of the turning roll (17), The cross-directional sealing surface (31) against the drying wire (18), and sealing means (29) adapted to contact the turning roll (17) and the channel (27) is arranged on the tail (22) of the box the width of the channel (27) is 400 - 500 mm. Method according to Claim 1, characterized in that, in the machine direction, the passage (27) is also sealed in a partial distance against the drying wire (18). Method according to claim 1 or 2, characterized in that the blowing (24) is formed by compressed air having a pressure of 10 to 60 kPa, preferably 10 to 30 kPa. Arrangement for threading in a dryer section of a fiber web machine, wherein the drying fabric (18) is alternately supported on the drying cylinders (16) and the rotating rollers (17) to form a single wire, and wherein the pocket space (20) ) is provided with a runnability component (19) for depressurizing the pocket space (20), and the assembly includes blowing means (25) arranged in a closing web (26) formed by a drying fabric (18) and a swivel roll (17) to provide enhanced vacuum ) formed and formed by a flow channel (27) having a flow surface (28) in which the blowing means (25) is arranged and which comprises machine direction sealing members (29) for sealing the channel (27) at the edges to a pivot roll (17); (18), and in the direction of rotation of the pivoting roll (17) to the channel (27) includes an extension (30) open to the drying wire (18), characterized in that in the direction of rotation of the swivel roll (17) at the beginning of the extension (30) there is a transverse sealing surface (31) against the drying wire (18); a roller (17), and the channel (27) is arranged in the region of the threading strap (22) with a width of the channel (27) of 400 mm to 500 mm. Arrangement according to Claim 4, characterized in that the flow surface (28) is formed by a plate structure (33) supported on the runnability component (19). Arrangement according to Claim 5, characterized in that the blowing means (25) are arranged to open on the pivoting roll (17) side of the plate structure (33). Arrangement according to one of Claims 4 to 6, characterized in that, in the direction of rotation of the swivel roll (17), there is a scraper (37) to prevent boundary layer air on the surface of the swivel roll (17) from entering the closing friction (26). Arrangement according to one of Claims 4 to 7, characterized in that the pivoting roll (17) has a smooth surface. Arrangement according to one of Claims 4 to 8, characterized in that the swivel roll (17) is non-absorbent.