WO2006010795A1

WO2006010795A1 - Roll to be used at a dryer section of a web forming machine

Info

Publication number: WO2006010795A1
Application number: PCT/FI2005/050233
Authority: WO
Inventors: Leo Kurkinen; Rami Vanninen
Original assignee: Metso Paper Oy
Current assignee: Valmet Technologies Oy
Priority date: 2004-07-28
Filing date: 2005-06-22
Publication date: 2006-02-02
Anticipated expiration: 2007-01-28
Also published as: CN1985046B; FI117013B; FI20045282L; CN1985046A; FI20045282A0; DE112005001565T5

Abstract

The invention relates to a roll to be used in the dryer section of a web forming machine. The wire (12) is arranged to travel over the roll (10, 11). The roll (10, 11) includes a shell (16) and end pieces (17) at both ends of it. In addition, means are arranged in connection with the roll (10, 11), for creating a pressure or temperature difference inside the roll (10, 11), relative to its environment. The shell (16) is of a thin-sheet material. A stiffener structure (18) is fitted inside the shell (16).

Description

ROLL TO BE USED AT A DRYER SECTION OF A WEB FORMING MACHINE

The present invention relates to a roll to be used in the dryer section of a web forming machine, where a fabric is arranged to travel over the roll, and which roll includes a shell and end pieces at both ends of it to support the roll rotatably in the web forming machine, and in connection with which roll means are arranged for creating a pressure or temperature difference inside the roll, relative to its environment.

Particularly in the dryer section of a web forming machine, there are numerous hollow rolls, through the slalom route of which the web is carried forwards on a fabric. Despite being located very closely together, the rolls are separate from each other. In other words, these are nip-free positions. In terms of construction, the roll has a cylindrical shell, at the ends of which end pieces are also installed. By means of the end pieces,' the roll is supported rotatably in the web forming machine. In a dryer section, there are mainly two kinds of hollow roll, suction rolls and dryer cylinders. The suction rolls in question are also referred to as suction hitch rolls. In the suction rolls there is a perforated shell, whereas in a dryer cylinder hot steam is led inside. In practice, the dryer cylinders are used to heat the web to dry it while the suction rolls are used to hold the web under control on top of the dryer wire used as the fabric. The term VAC-roll is also used for a large-diameter suction roll in the dryer section and is used mainly in connection with a one-wire draw.

As is known, in both rolls cast shells are used, which are several tens of millimetres thick. Thus the rolls become large, heavy, and expensive. Particularly in a suction roll, drilling the holes in the shell is in addition slow and demands special tools. At the same time, the holes have a deleterious effect of the stiffness of the roll and are liable to become blocked. On the other hand, the thick shell reduces the transmission of heat through the shell to the dryer wire and then to the web. Besides being difficult to manufacture, the heavy rolls demand large bearings and solid foundations . The rotation of the heavy rolls also requires powerful drives. In other ways too, the rolls are problematic in terms of vibration, due to their hollow construction and large mass. On the other hand, it is difficult to make the rolls any larger, due to casting tech¬ nique limitations, even though enlargement would be one way, for example, to increase their drying capacity.

The invention is intended to create a new type of roll to be used in the dryer section of a web forming machine, which is lighter than previously and is dynamically more stable an by means of which the drawbacks of the prior art can be avoided. The characteristic features of the present invention are stated in the accompanying Claim 1. In the roll according to the invention a particularly thin shell is used. This is achieved by using a thin-sheet material, which is stiffened in a new and surprising manner. The sheet construction avoids the difficult casting and drilling of the thick shell. The finished roll is also considerably lighter than conventional rolls. This reduces the power required to rotate it while the roll can be supported on smaller bearings than previously. On the other hand, it is possible to make considerably larger rolls than before, without restrictions of mass or vibration. In addition, due to its construction and manufacturing technique, the roll according to the invention is ready for use without machining. If necessary, a cover can be used, which can be machined to adjust the properties of the surface of the roll as desired. The end piece of the roll is also of a new type and utilizes bodies of revolution and plate structures.

In the following, the invention is examined in detail with reference to the accompanying drawings showing some embodiments of the invention, in which Figure Ia shows a schematic drawing of rolls according to the invention fitted in connection with the dryer section of a paper machine, Figure Ib shows a schematic drawing of one totality formed in the dryer section from rolls according to the invention,

Figure 2a shows an axonometric view of a roll according to the invention, Figure 2b shows a partial cross-section of a shell of the roll according to the invention, Figure 3a shows a partial cross-section of a roll according to the invention, Figure 3b shows a partial cross-section of a third adaptation of the shell of a roll according to the invention, Figure 4 shows a cross-section of a roll according to the invention, Figure 5 shows a partial cross-section of the end piece of the roll, Figure 6a shows a cross-section of an application of the roll according to the invention,

Figure 6b shows a partial cross-section of Figure 6a along the plane A-A.

Figure 1 shows one cylinder group, of which there are several consecutively in the dryer section of a web forming machine.

Known web forming machines are, for example, paper and board machines, and other similar machines. The cylinder group consists of consecutive drying cylinders 10 and suction rolls

11, through which the drying wire 12 being used as the fabric is led in an endless loop. Nowadays, one-wire draws like that shown are often used, in which there is only one drying wire in each cylinder group. In practice, the web is dried by leading it between the drying wire and a heated dryer cylinder. The dryer cylinder is heated by leading hot steam inside it. The construction of a dryer cylinder is examined in greater detail in connection with Figure 4. Correspondingly, at the suction roll, the web travels on top of the drying wire. The web is controlled by using the suction roll, the vacuum effect created by which holds the web on the drying wire. In addition to the suction roll with its vacuum effect, the web is controlled using a blower or suction box 13, which is located in a pocket formed by the consecutive dryer cylinders 10 and the suction roll 11.

Figure Ib shows only the drying wire 12, without the web. Means for creating a pressure or temperature difference inside the roll, relative to the environment, are additionally arranged in connection with the roll. The vacuum line 14 and the steam line 15 are shown schematically in Figure Ia. The vacuum and steam are produced in some known manner and are led to the rolls through the aforementioned lines .

Figure 2a shows an axonometric view of the roll according to the invention. As its basic components, the roll thus includes a shell 16 with end pieces 17 at each end of it, to support the roll rotatably in the web forming machine. One embodiment of the end piece 17 is shown in greater detail in Figure 5. Figure 2a shows a suction roll, in which there is a perforated shell 16. An individual hole is shown with the reference number 26. Externally, the roll according to the invention appears to be largely conventional, but its construction is entirely new and surprising. According to the invention, the shell 16 is actually of a thin-sheet material. In addition, a stiffener structure 18 (Figure 2b) is fitted inside the shell 16. This avoids casting and its consequent restrictions . At the same time, the roll becomes considerably lighter than previously and more advantageous in terms of vibration.

According to the invention, the stiffener structure is also of thin-sheet material, so that both the shell and the stiffener structure can be manufactured using the same means and methods. In practice, the thickness of the thin-sheet material is 1 - 5 mm, preferably 2 - 4 mm. One preferred material is cold-rolled sheet steel that has no residual stresses. Thus during and after cutting the thin-sheet pieces will remain straight and elastic recovery during bending will be small. On the other hand, it is possible to use, for example, composite structures, which are glued to the inner surface of the shell. Composite structures are light, but nevertheless create a good stiffening effect. In addition, complex shapes can be easily made in a composite structure.

Figure 2b shows a partial cross-section of the shell 16 of the roll according to the invention. According to the invention, in the radial direction of the roll, the height of the stiffener structure 18 is about 5 - 30 %, preferably 10 - 20 % of the roll's outer diameter. In that case, the size of the stiffener structure will remain reasonable and simplified structures can be used. The height of the stiffener structure is, however, at least 100 mm, so that the manufacturing methods will remain simple. In practice, the stiffener structure 18 is formed of several stiffener pieces 19, which are fitted at a distance from each other. In addition, the stiffener piece is formed of a stiffener profile, which is attached to the inner surface of the shell. In Figure 2b, hat-shaped stiffener pieces 19 are attached to the inner surface of the thin shell 16. In this case, each stiffener piece 19 is bent from a thin-sheet material and attached to the inner surface of the shell 16, for example, by welding. Though in terms of attachment of the stiffener piece 19 shown is preferred, other shapes of stiff¬ ener piece can also be used. At the left-hand end of the shell 16 of Figure 2b, the stiffener pieces 19 are attached very close to each other. At the right-hand end of the shell 16, however, the stiffener pieces 19 are clearly separate. The shape and size of the stiffener piece and the distance between them are dimensioned as required, taking into account the size of the roll and its operating application and purpose. In this embodiment, the stiffener pieces are also perforated, to ensure the even spread of the vacuum effect. The vacuum is introduced to the suction roll, for example, through a hollow protruding shaft 20 (Figure 2a) . A second embodiment of the roll according to the invention is shown in Figure 3a. In this case, the stiffener piece 19 consists of a circular ring, which is attached to the inner surface of the shell 16. The circular ring is simple to manufacture and it will easily create sufficient stiffness. In addition, it is possible to use unperforated sheet material, without causing the vacuum effect to spread unevenly. In the embodiment in question, there is also a cover 21 on the outer surface of the shell 16, in which there are grooves to spread the vacuum effect over a large area of the drying wire. In other words, the grooves are in the cover, instead of being in the base material of the roll, which will further simplify the manufacture of the roll. On the other hand, the shape of the groove can be selected more freely.

Figure 3 shows a third embodiment of the roll according to the invention. In this case, in the stiffener structure 18 the stiffener pieces 19 are connected to each other in the longitu¬ dinal direction of the roll, by means of an intermediate support 23. The intermediate support prevents the stiffener pieces from bending when the roll is loaded, thus forming an extremely stiff cell structure. At its simplest, the intermedi¬ ate support 23 is formed of a cylindrical support piece 24, which extends from one end piece of the roll to the other, and which is attached to each stiffener piece 19. On the other hand, it is possible to use, for example, longitudinal support pieces, which are attached to the circumference of the shell at specific intervals. In Figure 3b, the cylindrical support piece 24 extends over the entire length of the shell 10 and is attached to a special installation plate 25. Thus the shell can be manufactured separately and finally the end piece can be attached to the installation plate. When using cylinders as support pieces, these must be perforated or have larger openings, to permit the vacuum to spread evenly through the whole area of the shell. Thus, in the stiffener pieces and/or the support piece there is perforation or similar. On the other hand, when using thin-sheet material, the dimensions and location of the holes can be selected more freely than previ¬ ously. In that case, the vacuum effect can be applied differ¬ ently at different points in the shell. For example, at the end parts of the shell, i.e. at the edges of the web, a stronger vacuum can be formed, especially to control the edges of the web. In any event, in the shell of a roll used as a suction roll there is perforation, in order to direct the pressure difference, created inside the roll by means inside or outside the roll, to the wire and from there to the web.

The roll according to the invention can also be used as a dryer cylinder, which is shown in Figure 4. In the embodiment shown, circular rings are used as the stiffener pieces 19, and are additionally connected by a cylindrical support piece 24. In this case, the support piece 24 and the stiffener pieces 19 are perforated, so that hot steam can spread evenly over the entire area of the shell 16. In the lower part of the dryer cylinder there is also a syphon 27, for removing condensation water, which is shown by the broken-line arrow. Instead of the syphon, it is also possible to use other devices and methods to remove condensation water. In the embodiment shown, the support piece 24 extends to a short distance from the installation plate 25, allowing the syphon 27 to be fitted against the inner surface of the shell 16. The solid arrows show the spread of the steam inside the dryer cylinder.

In the embodiments of the rolls shown, it is possible to use end pieces of the same kind, each of which has a cell structure according to the invention. The end piece 17 includes a separate inner piece 28, in which there is an internal hole 30 corresponding to the protruding shaft 20, for the attachment of the protruding shaft 20. In addition, the end plate of the end piece 17 is supported on the inner piece 28 by at least one plate piece 31. Thus the various parts of the end piece can be manufactured separately, thus avoiding the casting and machin¬ ing of large pieces. In addition, the parts can even be made in different ways and from different materials. Thus it is possible to take into account, for example, stresses arising from the loading, or surface roughness requirements. In this case, the end plate is also supported by a second plate piece 32, which further facilitates the manufacture of the end piece. The construction in question is hollow, so that the end piece can be filled with insulation 33. Thus, particularly in large dyer cylinders the escape of heat through the end pieces can be prevented simply. The insulation is, for example, an extruded foam, which will spread evenly in the end piece and solidify in place. The same reference numbers are used for components that are functionally similar.

Figure 6a shows the roll according to the invention as a dryer cylinder 10. In this case too, the shell 16 is of a thin-sheet material. In addition, the end piece 17 is cup-shaped and is welded to the shell 16. This an installation plate is unneces¬ sary. In this embodiment, the stiffener structure 19 includes tensionable stiffener rings and heat strips 34 running in the longitudinal direction of the roll. Thus welding is not essential. The heat strips even and boost the distribution of heat. In addition, they increase the axial and annular stiff¬ ness of the roll. In each stiffener ring there is a tensioning arrangement 35, which includes a tensioner screw 37. There are suitable flanges 36 in the stiffener ring for the tensioner screws 37. At the end of the roll, there is also a steam condensate coupling 40, through which steam is first led into the roll and corresponding condensate is removed from the roll 10, for example, with the aid of a syphon 41.

Using existing casting technology, shells can be created with a maximum diameter of 2500 mm. According to the invention, the roll's diameter is 1000 - 5000 mm, preferably 1500 - 4000 mm. This is achieved by using a thin-sheet material in the manufac¬ ture of the roll. In addition, both the shell and the stiffener pieces are preferably laser-cut and laser-welded thin-sheet pieces. Using laser cutting, thin-sheet pieces with accurate dimensions and shape are created, which can be bent to a precise shape. Using laser welding, the thin-sheet pieces can also be attached to each other without deformations . On the other hand, gluing can be used in the attachments. Besides, or instead of laser methods, other suitable methods can be used. In the cross-sectional direction, the shell is preferably made from a single thin-sheet pieces, which is butt-welded. In the axial direction of the roll, on the other hand, the shell is formed of two or more cylindrical pieces. Thus the manufactur¬ ing process will remain sufficiently simple. In addition, it is easy to make holes in a thin-sheet material while particularly by using laser cutting the holes will be precisely delimited. At the same time, the shape and position of the holes can be selected considerably more freely than when using conventional methods .

The roll according to the invention is considerably lighter than previous rolls. In addition, despite the thin-sheet material, the shell is made sufficiently stiff by using a stiffener structure. In addition, the use of the structure eliminates semi-critical vibration, so that it is possible to manufacture safely smaller or correspondingly larger rolls than before. At the same time, by using sheet structures, the previous limits set by the manufacturing technique can be avoided, without weight problems. It is then possible to manufacture even very large rolls. In addition, the roll is highly corrosion-resistant while the new manufacturing method also shortens the delivery time for rolls . The transmission of heat through the thin shell is also more efficient than previously.

Claims

1. Roll to be used in the dryer section of a web forming machine, where a wire (12) is arranged to travel over the roll

5 (10, 11), and which roll (10, 11) includes a shell (16) and end pieces (17) at both ends of it to support the roll (10, 11) rotatably in the web forming machine, and in connection with which roll (10, 11) means are arranged for creating a pressure or temperature difference inside the roll (10, 11), relative to 10 its environment characterized in that the shell (16) is of a thin-sheet material and a stiffener structure (18) is fitted inside the shell (16) .

2. Roll according to Claim 1, characterized in that the 15 stiffener structure (18) is also of a thin-sheet material.

3. Roll according to Claim 1 or 2, characterized in that the thickness of the thin-sheet material is 1 - 5 mm, prefera¬ bly 2 - 4 mm.

20

4. Roll according to any of Claims 1 - 3, characterized in that the height of the stiffener structure (18) in the direction of the radius of the roll (10, 11) is 5 - 30 %, preferably 10 - 20 % of the outer diameter of the roll (10,

25 11) , the said height being, however, at least 100 mm.

5. Roll according to any of Claims 1 - 4, characterized in that the stiffener structure (18) is formed of several stiffener pieces (19) , which are fitted at a distance from each

30 other.

6. Roll according to Claim 5, characterized in that the stiffener piece (19) is formed of a circular ring, which is attached to the inner surface of the shell (16) .

35

7. Roll according to Claim 5, characterized in that the stiffener piece (19) is formed of a stiffener profile, which is attached to the inner surface of the shell (16) .

5 8. Roll according to any of Claims 5 - 7, characterized in that the in the stiffener structure (18), the stiffener pieces (19) are connected to each other in the longitudinal direction of the roll (10, 11) by an intermediate support (23) .

10 9. Roll according to Claim 8, characterized in that the intermediate support (23) is formed of a cylindrical support piece (24), which extends from one end of the roll (10, 11) to the other, and which is attached to each stiffener piece (19) .

15 10. Roll according to any of Claims 5 - 9, characterized in that there is perforation in the stiffener pieces (19) and/or the support piece (24) .

11. Roll according to Claims 5 - 10, characterized in that 20 both the shell (16) and the stiffener pieces (19) are laser-cut and laser-welded thin-sheet pieces.

12. Roll according to any of Claims 1 - 11, characterized in that the roll is a dryer cylinder (10) or suction roll (11)

25 of the dryer section of a web forming machine.

13. Roll according to any of Claims 1 - 12, characterized in that there is perforation (26) in the shell (16) , in order to direct to the wire (12) the pressure difference created

30 inside the roll (10, 11) by the means (14, 15) .

14. Roll according to any of Claims 1 - 13, characterized in that the end piece (17) has a cellular structure and has insulation (33) inside it.

35

15. Roll according to any of Claims 1 - 14, characterized in that the diameter of the roll (10, 11) is 1000 - 5000 mm, preferably 1500 - 4000 mm.