WO2004074148A2

WO2004074148A2 - Device for guiding a moving web of fibrous material

Info

Publication number: WO2004074148A2
Application number: PCT/EP2004/050148
Authority: WO
Inventors: Werner Buttschardt; Wolfgang Schmitt
Original assignee: Voith Paper Patent Gmbh
Priority date: 2003-02-22
Filing date: 2004-02-18
Publication date: 2004-09-02
Also published as: EP1606205A2; WO2004074148A3

Abstract

The invention relates to a device for guiding a moving strip of fibrous material, especially a strip of paper or card. Said device comprises a guiding element (1) which extends essentially over the total width of the strip of fibrous material (5). According to the invention, a cylinder (1) which rotates in the direction (L) in which the web of fibrous material (2) runs is provided as a guiding element in addition to means which exclusively form a gas film (GF) between the surface (0) thereof and the side (5a, 5b) of the web of fibrous material (5) extending over said surface. The web of fibrous material (2) does not substantially enter into contact with the cylinder (1) and a broad extending effect can be obtained on the web of fibrous material (5) such that longitudinal folds in the web of fibrous material (5) can be removed or prevented.

Description

Device for guiding a running fibrous web

The invention relates to a device for guiding a running fibrous web, in particular paper or cardboard web, with a guide element which extends essentially over the entire width of the fibrous web.

A guide element, which extends over the entire width of the fibrous web, is known from EP-A2-0744 388. The slide strip described here, which acts as a guide element, is fixedly arranged below the running fibrous web. The upper side of the slide strip facing the underside of the fibrous web is convex in shape.

It is also common to guide the fibrous web over a so-called airtum. This enables contactless guidance while the guide element is also stationary. The air emitted by the air turn creates an air cushion, which is however uneven, so that no wrinkle-free web guidance is guaranteed.

A certain amount of web tension is also necessary for perfect web guidance. If this is set too high, longitudinal folds occur, which are called omega folds in terms of their shape.

These omega folds cause considerable losses in quality, for example in the case of a web to be produced and / or refined.

It has been found in practice that the air cushions or cushions produced with all known guiding and deflecting devices for supporting and guiding the fibrous web do not counteract the formation of wrinkles, but rather yield more to the wrinkles.

The known contactless web guiding elements, such as so-called airtums (see US5242095) or floating dryers, do the job of supporting the web or to redirect them, but they are unable to avoid or eliminate wrinkles at the same time. The use of so-called airfoils at the outlet of said airtum was still not fully convincing in this regard.

The applicant has therefore proposed in published DE 10254777 to arrange a web-wide guide element below the running fibrous web. This is designed in the form of an aerodynamic body with a wing-shaped top. This top side faces the fibrous web.

The body thus configured as a known aircraft wing is able to achieve a spreading effect of the moist or freshly coated fibrous web.

A certain disadvantage is its relatively complicated design.

The invention has for its object to develop a device with a more simply designed or to be provided guide element, which enables both a mainly contactless guidance and deflection, as well as elimination and / or avoidance of longitudinal folds of a running fibrous web.

The object of the invention is achieved by a device specified in claim 1.

According to the invention, this device comprises as a guide element a roller rotating in the running direction of the fibrous web. This roller is designed in this way and, in addition, means are provided which make it possible to form a thin gas film or only a gas boundary layer between the surface of the roller and the side of the fibrous web under tension which runs over this surface. The gas film extends continuously over the entire wrapping area (ie that handling area of that of the fibrous web is entwined). Surprisingly, a spreading effect on the fibrous web can thereby be achieved. This thin gas film in conjunction with the set web tension exerts pressure on the web and thus brings about this effect. The dreaded longitudinal folds in the fibrous web can thereby be eliminated or even avoided entirely.

This gas sliding film also causes such a distance of the fibrous web from the roll surface or has such a thickness that the web hovers essentially contactlessly (during the operation of the device) over the roll.

It goes without saying that the web can briefly or locally touch the roller if the operating speed (often up to 2000 m / min) has not yet been reached or if there are particularly strong irregularities and folds in the web. This contact is harmless.

The gas film that can be achieved with the device according to the invention is very thin. It is equal to / less than 10 mm, preferably <5 mm, in particular 0-2 mm, between the fiber web and the roll surface.

In an embodiment of the invention it is provided that the roller runs in a driven manner and has a higher peripheral speed than the running speed of the fibrous web, which, as already mentioned above, is between 1500 and 2000 m / min.

According to the invention it is also provided that the roller has a relatively large outer diameter. This should be at least 450 to 600 mm, but preferably 800 mm. The choice of diameter depends on the web speed, the type of paper or cardboard and also the web width. The latter is often about 10 m and more for reasons of economy.

With both of the mentioned design options, ie high running speed and / or large outside diameter of the roller, the thickness of the gas film is and thus the distance of the web from the roll surface can be influenced. So the faster the roller turns, the thicker the gas film that guides the web. With a larger diameter of the roller, the base area of the gas film is larger and thus optimizes the stability of the guide.

It has been found that, surprisingly, a thin gas film is sufficient to guide the web safely and evenly and, moreover, omega folds can be compensated for and / or avoided.

An expedient embodiment of the invention can consist in the roller being designed as a blowing roller with an integrated gas supply. The gas is supplied by pumping, which is generated by the rotating roller by being driven at a speed different from that of the web. As described above, it is particularly expedient if the speed of the roller is higher than that of the web. However, the roller does not need to be driven in order to form a gas film. The roller rotates when the machine is started up or the device is started up. The entrained air then jams between the roller and the fibrous web during operation.

The blow roller can have a fixed pressure chamber which is open towards its outer circumference and which can be acted upon by a gas, in particular air or steam.

According to the invention, the roller is also provided with an outer jacket rotating about its axis. A large number of through or outlet openings are incorporated in the outer jacket, so that the gas can escape in the form of jets and the roller can thereby act as said blowing roller.

For the targeted formation of the gas film and its stabilization, the gas jets are through the outlet openings, in the direction of the blow roller tapered fibrous web steerable.

It is expedient if the outflow direction and / or the size of the outlet openings can be varied.

As a result, it is possible to exert an influence particularly on that area of the web which exhibits irregularities and / or which can be expected to produce particularly strong wrinkles.

A very advantageous and, above all, structurally less complex solution can consist in that the guide roller is designed as a solid jacket roller instead of the roller described above, which has outlet openings.

To form or increase the air boundary layer which is present anyway with the running web and the fast-running roller, the solid jacket of the roller is assigned a separate blowing nozzle which is acted upon by a gas, such as air, in particular conditioned air or steam. From this blow nozzle, as in the blow roller described above, gas jets which are variable in direction and size can emerge to the desired extent, which are entrained with the roller as an interface and, as said, enlarge and stabilize the gas film between the roller and the fibrous web.

For this purpose, it is most expedient if the blowing nozzle is arranged in the feed area (that is, the area of the roller to which the web runs in its running direction) of the fibrous web.

A possible variant of the design of the blowing nozzle can consist in the fact that it is designed essentially web-wide with a continuous blowing slot.

Another variant can consist of being distributed over the width of the roller arranged individual blowing nozzles are provided. With these individual nozzles, the size and direction of the jets to be ejected can be better adjusted and maintained independently of one another.

A further advantageous embodiment of the roller proposed as a guide element, in particular that with the solid jacket, can consist in that its outer surface is equipped with a surface that corresponds to that of a golf ball. Such a surface consists of a large number of lined up, uniform and circular dents, which improve the flight characteristics of the golf ball in a particularly high degree - namely to be able to fly quickly, thereby far and in a precise line. Transferred to the present fibrous web, this means improved running properties within a manufacturing and / or finishing machine for the fibrous web and also an improvement in its quality.

The guide element according to the invention or the roller described is therefore particularly suitable for use within the said machine.

The roller can be arranged in the immediate vicinity of a contactless deflecting element, for example an air turn or floating dryer.

Alternately, the roller can also be used as an independent web guiding element, as a replacement for an air turn.

The roller according to the invention can be used particularly advantageously in coating systems. The formation of longitudinal folds is particularly critical here with regard to an even application layer. For this reason and to protect the freshly applied layer, it is arranged downstream of a coating unit for coating one or both sides of the fibrous web in the running direction of the fibrous web. Depending on whether the fibrous web is treated on one or both sides, the guide roller is only arranged on one side of the web (for one-sided application) or on both Web sides (for two-sided orders) make sense.

This arrangement and the direction and intensity of the jets emitted by the blow roller with a perforated outer jacket into the inlet area of the fibrous web or the jets emitted by the blow nozzle to the full jacket roller produce the known Coanda effect. It consists in the blowing jet or the blowing jets generating high speed in the region of the convexly curved outer jacket of the roller. This creates a gas layer that is just thick enough that the fibrous web can slide over it almost without contact. In addition, the web is sucked towards the roller, stabilized and smoothed in the transverse direction. Existing web longitudinal folds slide transversely to the web running direction, i.e. to the side and thus away to the outside and thereby disappear. In the most favorable case, these dreaded longitudinal folds do not even occur when the device according to the invention is used.

This device according to the invention on the one hand increases the runtime efficiency with high operational reliability of the manufacturing and / or finishing machine, that is to say the coating machine, and on the other hand improves the product quality, such as that of a coated paper.

An effective adaptation to the respective current conditions, such as flow conditions, web speed and type of fibrous web, is possible at any time.

Measures to increase the train train are no longer necessary. This is all the more important since a web that has not yet dried completely or a freshly painted web is particularly at risk of tearing. Another advantage of the invention is that only small amounts of gas are required to guide the fibrous web largely without contact.

Further advantageous design features of the device according to the invention, Like a cambered or a curved design of the guide element (roller) result from further subclaims.

The invention will be explained in more detail below on the basis of exemplary embodiments:

In a schematic representation:

Figures 1, 2 and 3: a device according to the invention with a guide element in the form of a roller in cross section Figure 4: the top view of the surface profile of the invention

Rolls from Figures 1 to 3 Figures 5 to 8: Installation options within a coating machine.

In the figures, the same or equivalent components are provided with the same reference numerals. Therefore, only the changes compared to the other figures are shown in the descriptions of the individual figures.

The device according to the invention comprises a guide element which is designed as a roller and is generally designated 1 in all figures.

FIG. 1 shows a special embodiment of the roller 1, which acts here as a blowing roller and is designated 1.0.

This blow roller 1.0 essentially consists of a roller core 1.1, a concentric support part 1.2 and an outer jacket 1.3 with a surface O. The support part 1.2 contains a partition walled off by side walls 1.4 and 1.5, but by at least one adjustable side wall (in the example, this is wall 1.4 ) an adjustable pressure chamber 1.6.

This pressure chamber 1.6 is connected to a gas supply line 1.7, in particular a compressed air line, and is open to the outer jacket 1.3. The Pressure chamber 1.6 is designed to be stationary, while the outer casing 1.3, which is provided with a large number of passage or outlet openings 1.8, rotates in the direction of the arrow R around the core 1.1 or the supporting part 1.2. The outlet openings 1.8 are also adjustable in size (for example by arranging slides, not shown) and also in their outflow direction.

Gas jets 3 are thereby very effectively expelled through the openings 1.8, specifically in the direction of the inlet side 4 of a paper web 5 tapering towards the blowing roller 1.0.

The pressure chamber has the cross-sectional shape of a circular sector and, due to its adjustability through the side wall 1.4, regulates the quantity.

The pressure chamber wall 1.4 should be set at an angle of approximately 45 °, in particular in the range from 15 ° to 30 ° to an imaginary vertical roller axis Av, because the pressure chamber 1.6 adjoining it in this area contains the gas selected for the formation of the gas film GF can be optimally fed.

As a result of the high speed (approx. 2000 m / min) of the paper web 5 running in the direction of travel L and the even higher roller speed of the blowing roller 1.0 rotating in the same direction of travel R, the desired gas film GF is formed, which serves to guide and stabilize the paper web 5. A vacuum is also formed in the area of the circular outer surface 1.9 of the blowing roller, which allows the air boundary layer to flow and is known as the "Coanda effect". This air flow can now be used to eliminate or even avoid longitudinal folds or omega folds in the fibrous web, or in a still moist fibrous web 5 treated with a liquid to pasty application medium.

The thickness of the gas film between the roller surface and the fibrous web expediently only needs to be very small. The thickness a is regulated as Control variable by changing the conveyed air volume and / or the set pressure and / or the speed of the roller as a manipulated variable. For example, the wrap angle of the web 5 on the roller 1 and / or surface parameters - such as spring stiffness, coefficient of friction, surface structure of the roller 1 - can also be taken into account in the control. The regulation can also take place as a function of the web tension and / or the running speed of the web 5.

The devices shown in Figures 2 and 3 are based on the same principle as described in Figure 1.

In FIG. 2 there is also a blowing roller 1.0, as in FIG. 1, but with jets 3 directed essentially downwards. The roller 1.0 is only shown with the outer contour (ie without an interior). If the roller 1.0 now rotates faster than the speed of the paper web 5, a particularly stable air boundary layer LG is maintained. For example, the roller speed is increased by 1 m / s compared to the web speed.

Another variant of the roller 1 that is easier to manufacture can be seen in FIG. The roller 1 here has a solid jacket 6 instead of a perforated outer jacket. It also contains no pressure chamber.

To form the air cushion and the gas film GF that achieves the spreading effect, a separate blowing nozzle 7 is arranged in the inlet gusset Z or the web inlet side 4. The outflow direction of the blowing nozzle 7 is aimed at the solid jacket 6.

The blowing nozzle 7 is designed in the present example in the form of a pipe 7.1 adapted to the width of the roller 1 with a plurality of outflow openings 7.2, but could also have a continuous outflow slot with gas feeds which can be acted upon separately. Air or steam can also be used as the medium for the formation of the gas film GF, as in the blow roller according to FIGS.

In a further FIG. 4, a preferred surface profile of the roller 1 or 1.0 can be seen. It is designed in the manner of the surface profile of a golf ball, with a plurality of dents 8 which preferably cover the entire surface O. The dents 8 have a gentle inlet radius to the initial level of the roll surface O or outer jacket 1.3.

Such a surface structure has a particularly positive effect on the running behavior of the paper web 5. A guide roller with such a surface is known from DE-A1 10048305.4.

Depending on the size, that is the diameter and depth of the dents 8 and their number distributed over the roll surface O, the desired flow conditions of the gas sliding layer GF can be influenced.

As a material for the roller types 1, 1.0 or 6 described above, metal or plastic, for example a fiber-reinforced plastic such as glass-fiber reinforced plastic (GRP), can be selected.

FIGS. 5 to 8 show the roller according to the invention in connection with a coating machine 9. The coating machine 9 is arranged downstream of a drying section (not shown in the figures) of a machine for producing and finishing a paper or cardboard web. The roller according to the invention could also be used in other parts of the machine where the paper web 5 tends to wrinkle due to its moisture content or where irregularities in the fibrous web are expected.

In these examples, the coating machine 9 contains the nip-forming application rollers 9.1 and 9.2 and application units 9.3 here for indirect application.

On the detailed representation and description of the special application units, which, of course, can also act directly on the paper web without application rollers, should be dispensed with here, since these are sufficiently known. In FIGS. 6 and 7, the application units 9.3 have not been included for reasons of simplification.

FIG. 5 shows that the guide element or the roller 1 can act as an independent web guide element in a region of a free web tension.

However, this roller 1 can also be used in the immediate vicinity of a contactless deflecting element, for example an air turn 10 and / or a contactless web drying element, a floating dryer 11, as shown in FIGS. 6 to 8.

In these figures, the roller 1 is arranged within a free web train, as said.

In FIGS. 5, 7 and 8, such a roller 1 is assigned to both web sides 5a and 5b. FIG. 6 shows the arrangement of one roller 1 in front of and one behind a floating dryer 11.

However, other configurations are also conceivable.

Thus, the device according to the invention could also be used in a construction which is known in the applicant's company under the name "Module Dryer" and is partially shown in FIG. 8. Here, a roller 1 or 1.0 or 6 is assigned to both the upward and downward paper webs 5 and acts as an air reservoir (ie as a deflection element, which can also be designed as a dryer), whereby it is directly a structural unit with the Schwebetrockπer 11 forms.

As FIGS. 5 to 7 show, there are in principle several rollers 1, 1.0 and 6 used. The outer diameter of each of these rollers should have a minimum diameter of 450 mm in view of the formation of the gas film.

The shape of the roller 0, 1.0 or 6 is not illustrated in the figures.

However, it can have a uniform cross-section over its length, be curved or can also be designed cambered.

It has been shown that the formation of undesired longitudinal folds occurs particularly frequently in the case of higher coating weights and / or greater penetration into the paper web 5 and the device according to the invention described here should preferably be used there. The applied layer of a liquid to pasty application medium, such as coating color, glue or starch, remains undamaged when the device according to the invention is used, but above all the swelling caused by the application of the line with subsequent wrinkling can be successfully ironed out of the web.

Most of the time, the said undesirable folds occur when the paper web is deflected. With the installation of the rollers according to the invention in front of a deflection device, even the folds can be prevented, with the installation after the deflection device, preferably after the first contactless deflection, folds can be compensated for.

Claims

claims

1. Device for guiding a running fibrous web, in particular a paper or cardboard web, with a guiding element (1) extending essentially over the entire width of the fibrous web (5), characterized in that a guiding element in the running direction (L) of the fibrous web (2) rotating roller (1) and means are provided which have only a thin gas film (G) continuously between the surface (O) of the roller (1) and the side (5a, 5b) of the fibrous web running over this surface (O) (5) form, the fibrous web (2) essentially not contacting the roller (1).

2. Device according to claim 1, characterized in that the thickness of the gas film (GF) for substantially contactless guidance of the running fibrous web (2) to ≤ 10 mm, preferably ≤ 5 mm, in particular

0 to 2 mm is adjustable or adjustable.

3. Device according to claim 1 and 2, characterized in that the gas film (G) consists of air, preferably conditioned air.

4. The device according to claim 1 to 3, characterized in that the roller (1) is driven and has a higher running speed than the fibrous web (5), the fibrous web running at about 1500-2000 m / min.

5. The device according to claim 1 to 4, characterized in that the roller (1) has an outer diameter of at least 450 mm, preferably

800 mm.

6. The device according to claim 1 to 5, characterized in that the roller (1) is designed as a blowing roller (1.0) by being exposed to gas, in particular air, and for this purpose a fixed pressure chamber (1.6) open to its outer circumference has an outer jacket (1.3) rotating about its axis (A) and provided with a plurality of outlet openings (1.8).

7. The device according to claim 6, characterized in that the pressure chamber (1.6) can be acted upon by the gas, wherein to strengthen the gas film (GF), gas jets (3), in particular air, through the outlet openings (2.8) in the direction the, the blowing roll (1.0) tapered fibrous web (5) are steerable.

8. The device according to claim 1 to 5, characterized in that the roller (1), instead of being equipped with outlet openings, has a solid jacket (6), the at least one separate blowing nozzle (7) for applying gas jets (3) , in particular air jets, is assigned.

9. The device according to claim 8, characterized in that the blowing nozzle (7) on the inlet side (4) of the fibrous web (5) is arranged.

10. The device according to one or more of claims 6 and 9, characterized in that the outflow direction of the gas jets (3) and / or the size of the outlet openings (1.8) are adjustable.

11. The device according to claim 8 to 10, characterized in that the blowing nozzle (7) substantially web-wide with a continuous outlet opening

(7.2) or in the form of a web-wide tube (7.1), one of which

Branch off a multiplicity of individual nozzles or outlet openings (7.2) or a multiplicity of individual blowing nozzles (7) with individual outflow openings (7.2) distributed over the width of the roller (1) are provided.

12. The device according to one or more of claims 1 to 11, characterized in that the roller (1) on its Außeneπumfaπg (1.9) has a golf ball-like surface profile.

13. The device according to one or more of claims 1 to 12, characterized in that the gas film (GF) can be generated by a combined arrangement of blowing roller (1.0) and separate blowing nozzle (7).

14. The device according to one or more of the preceding claims, characterized in that the roller (1, 1.0, 6) has the same cross section over its entire length.

15. The device according to one or more of the preceding claims, characterized in that the roller (1, 1.0, 6) is convex or is curved around its longitudinal axis.

16. The device according to one or more of the preceding claims, characterized in that the thickness a of the gas film is controllable in such a way that the thickness a is the controlled variable and as a manipulated variable a change in the delivered gas volume and / or the gas pressure and / or the speed of the Roller (1, 1.0, 6) is selectable.

17. The device according to one or more of the preceding claims, characterized in that the guide body or the roller (1, 1.0, 6) within a machine for producing and / or finishing a paper or cardboard web, in particular in the area of coating machine π (9), where the fibrous web has not yet reached the final dry content has, in particular between a first

Application work and the reeling of the fibrous web is used and thereby acts as an independent web guide element or is arranged in the immediate vicinity of a contactlessly known deflecting element, for example an air turn (10) or a web drying element, such as a floating dryer 10 (11).

18. The apparatus according to claim 17, characterized in that the roller (1, 1.0, 6) in the running direction (L) of the fibrous web (5) of an application device (9.1, 9.2, 9.3) for coating one or both sides 15. (5a, 5b) is arranged downstream of the fibrous web (5).

19. The device according to one or more of the preceding claims “characterized in that the roller (1, 1.0, 6) is arranged on one or both web sides (5a, 5b) of the fibrous web (5).