WO2008141890A1

WO2008141890A1 - Device for guiding a material web strip

Info

Publication number: WO2008141890A1
Application number: PCT/EP2008/055069
Authority: WO
Inventors: Philippe Vom Bauer
Original assignee: Voith Patent Gmbh
Priority date: 2007-05-18
Filing date: 2008-04-25
Publication date: 2008-11-27
Also published as: DE502008001169D1; EP2147151A1; DE102007023215A1; CA2687551C; ATE478194T1; CA2687551A1; EP2147151B1

Abstract

The invention relates to a device (1) for guiding a material web strip in a running direction (2), having a housing (3), in which a negative pressure generation system is arranged. It is intended to guide the material web strip safely. To this end, it is provided that a plurality of vacuum chambers (7-10 12) are arranged one after another in the running direction (2) in the housing (3), of which each comprises at least one suction device (20-25).

Description

Device for guiding a material web strip

The invention relates to a device for guiding a material web strip in a running direction with a housing in which a Unterdruckerzeugungseinrich- device is arranged.

The invention will be described below in connection with a paper web as an example of a material web strip. However, it is also applicable to other material webs and cut material web strip.

During its production and processing, a paper web must be guided through various processing devices, including a dryer section, a press section, a calender and optionally a spreading or a sizing device. This is often done in this way that at the edge of the paper web a strip of material web having a width of the order of 200 to 300 mm is cut and this strip first passes through the processing device. As soon as this material strip has reached the point where it can be pulled onto it, the paper web is cut to width so that it can pass through the corresponding processing device in full width.

For guiding the material web strip, in addition to what are known as cable guide arrangements, devices which operate under reduced pressure are also used. Here, an air-permeable belt usually runs around a housing on which the material web lies. The tape is supported on a plate provided with holes or slots. On the side facing away from the tape of the plate, a negative pressure is generated, so that the web strip is sucked on the other side of the tape.

An example of such a device is known from EP 1 127 978 B1. Here, several turbines are arranged in the housing, which suck air through the tape to hold the web strip on the other side of the tape.

Another embodiment is known from EP 1 342 844 A2. Here, several "doctor blades" are arranged in the housing, which ends shortly below the inside of the band and peel off the air layer located there, so to speak. This also causes a negative pressure on the ßenseite the band generated with which the web or at least their web strip can be firmly sucked.

In increasingly faster machines but it is difficult in all cases to ensure that the web strip is guided so stable that it can be easily passed to a subsequent transport device, such as a cable guide assembly or other Unterdrtick conveyor.

The invention has for its object to guide a strip of material safely.

This object is achieved in a device of the type mentioned above in that in the housing in the direction of succession a plurality of vacuum chambers are arranged, each of which has at least one suction device,

With this configuration, the time required to pressurize the web strip with the full vacuum is shortened. The material web strip is guided over the housing and increasingly covers a vacuum chamber. However, as long as the vacuum chamber is not completely covered, "secondary air" can be sucked through the remaining opening, so that the negative pressure in the vacuum chamber is often still too weak to securely hold the material web strip. But as soon as the material web strip has completely covered the vacuum chamber, acts from the suction device to Provided negative pressure in full Urnfang on the web strip. Since a plurality of negative pressure chambers are arranged one behind the other in the running direction, the length of each vacuum chamber is shorter than that of the entire device, so that it is completed earlier at the same speed. If the material web strip is held in the running direction on the first vacuum chamber, then it is already stabilized to a certain extent. However, the holding force, which is composed of surface area and negative pressure, is in many cases still too low to securely hold the material web strip in total. However, this unstable situation only lasts for a short time, because the web of material continues to run and then covers the next or next chambers in the running direction, so that the negative pressure located there also acts on the web of material. The holding force acting on the material web strip is thus constructed in sections.

Preferably, a first vacuum chamber in the direction of travel of the material web strip has a larger number of suction devices than a vacuum chamber arranged behind it in the direction of travel of the material web strip. This makes it possible to generate a higher negative pressure in the first vacuum chamber, as long as the web of material web has not yet completely covered this vacuum chamber. Because of the plurality of suction devices namely more air is conveyed away, so that the web strip already with a high reliability on the screen or another air-permeable band is held when the first vacuum chamber is not completely closed. The highest negative pressure occurs when the first vacuum chamber is completely covered by the material web strip. After the material web strip is stabilized in this way over the first vacuum chamber, a lower negative pressure is sufficient to transport the web strip to the end of the device. Since the vacuum chambers are gradually covered and then act with full negative pressure on the web strip, the holding force on the air-permeable belt at the end of the device is very large. Slippage of the material web strip is reduced or even prevented.

Preferably, the inrichtungenaugeinrichtungen are designed as suction nozzles. Suction nozzles are easy to install. They are supplied with compressed air, so that even the energy required for sucking energy can be provided in a simple manner.

Preferably, a boundary wall is filled with suction in the first vacuum chamber. Thus, it is possible to provide such a large number of suction devices that this wall, for example the bottom of the vacuum chamber, is completely or at least almost completely covered with suction devices. The suction devices here are not only the openings through which the suction air is sucked out of the vacuum chamber, but also the elements that surround the suction openings. By having one accordingly large number of suction devices provides, which are distributed over the boundary wall, the negative pressure can be generated so to speak flat.

The vacuum chambers preferably have a guide side along which the material web strip runs and a bottom opposite the guide side, the suction devices acting through the bottom. This embodiment has the advantage that the contaminants are sucked towards the bottom and can then be removed by the suction devices. In the long term practically no dirt can accumulate in the vacuum chamber. This applies regardless of whether the device is operated so that the web strip is guided in the direction of gravity above or below it. It is important in this context that the air flow can be sucked so to speak straight from the dirt causing side in the opposite side.

Preferably, the guide side and the bottom are parallel to each other. The vacuum chambers thus have a constant height in the direction of travel. This simplifies the production.

It is preferred that the guide side and the bottom have a spacing in the range of 5 to 35 mm, in particular in the range of 10 to 20 mm. Thus, the volume of the vacuum chamber on the one hand kept so small that you with an acceptable cost can generate sufficient negative pressure relatively quickly. On the other hand, there is a sufficient distance between the guide side and the bottom, so that the flow cross-section for the air to be extracted is large enough.

Preferably, the suction means are arranged symmetrically with respect to a central axis which is parallel to the running direction. Thus, the negative pressure relative to the central axis can be generated symmetrically, which also contributes to a stabilization of the material web strip on the air-permeable belt. If you have only one suction device, such as a suction nozzle in the vacuum chamber, then this Ξaugdüse is divided by the central axis. If you have two suction nozzles in the vacuum chamber, then these are arranged symmetrically on both sides of the central axis.

Preferably, at least two adjacent vacuum chambers are separated by a partition, which at least partially encloses an angle to the direction of rotation, which is greater than 95 ° or less than 85 °. In other words, the partition extends at least in sections at an angle ≠ 90 ° to the direction. This has the advantage that the material web strip at least temporarily covers two vacuum chambers. This avoids dead zones, which could possibly lead to instability of the material web strip. If the web strip runs with its beginning over the partition, then he acted simultaneously by the negative pressure in two vacuum chambers, wherein the first negative pressure chamber in the direction of acting on the web strip.

It is preferred that the partition has two legs which are inclined in opposite directions to the running direction. Preferably, these two legs are inclined in the direction of travel. This in turn results in symmetrical conditions, which has a favorable effect on the stabilization of the material web strip.

Preferably, the legs collide in a V-shape. Thus, the partition has two substantially straight sections so that it is easy to manufacture. As soon as the material web strip passes over the top of the "V" with its beginning, it is also subjected to negative pressure by the following vacuum chamber.

Preferably, at least in a vacuum chamber, the partition extends in the direction of both sides of the suction device. The inrichtungaugeinrichtung is thus positioned relatively close behind the partition, so that the negative pressure can act relatively early on the web strip, so almost immediately when the web has been passed over the partition wall. This results in conditions after only a short time, through which the material web strip can be stably guided. If the partition wall is V-shaped, then the suction device is located, as it were, in the gusset of the "V". The housing preferably has an intermediate wall delimiting the vacuum chamber. This makes it possible to keep the volume of the vacuum chambers small. The smaller the volume, the faster the air in it can be sucked off and the negative pressure built up. The amount of negative pressure is thus not appreciably affected. You no longer have to empty the entire housing to create the vacuum.

Preferably, the intermediate wall is formed trough-shaped with inclined side walls. The inclined side walls contribute to a reduction in the volume. On the other hand, they also help to remove dirt particles or water, which penetrate into the vacuum chamber, to the suction devices out.

It is preferred that the side walls are inclined in the direction of gravity to the suction towards.

This also facilitates the removal of dirt.

Preferably, a compressed air supply line for the suction nozzles between the housing and the intermediate wall is arranged. This compressed air supply line is therefore in any case not visible within the device and does not bother. Also, the risk of it being damaged is reduced.

Preferably, a vacuum chamber has a volume of at most 2 1, in particular at most 1 1, on. One such a small volume can be sucked out relatively quickly, so that even webs of material running along the web, which, for example, have a speed of the order of magnitude of 1,800 m / min, can be kept stable very quickly.

Preferably, at least one vacuum chamber is divided into at least two compartments parallel to the running direction. This is preferably the first vacuum chamber in the direction of travel. If the material web strip is cut out of the material web, then it may happen that it does not come to rest exactly in the middle of the vacuum chamber. In this case, there is a risk that it does not completely cover the vacuum chamber, so that side air can still be sucked in, whereby the holding force is reduced. If you divide the vacuum chamber parallel to the running direction in at least two compartments, then the chance is great that at least one of these compartments is completely covered by the material web strip. At least in this compartment of the web strip is then held with full force.

It is preferred that each compartment is limited in the direction of travel by a V-shaped partition wall. This results in the advantages that have been described above in connection with a vacuum chamber in general. The V-shaped partition does not create a dead zone when the web of material passes over the partition. Rather, when crossing the separation wall then acted upon by the negative pressure in two adjacent compartments in the direction.

The invention will be described below with reference to a preferred AusführungsbeiSpiels in conjunction with the drawing. Herein show:

1 is a perspective view of an apparatus for guiding a web strip in the open state,

2 is a plan view of the device of FIG. 1,

Fig. 3 is a section III-III of FIG. 2 and

Fig. 4 is a sectional view through a suction nozzle.

A device 1 for guiding a material web strip not shown in detail in a running direction 2 has a housing 3 which is provided at its front end with a deflection roller 4 and at its rear end with a deflection roller 5. For the guide roller 5 at the rear end a drive pin 6 is provided, to which a drive motor not shown in detail can be connected. About the two pulleys 4, 5, an air-permeable belt is performed, which is not shown for reasons of clarity in the drawing. This band may be formed, for example, as a sieve. The housing 3 has a cover plate, also not shown, which is provided with openings, for example in the form of slots. The cover plate has been omitted in order to be able to present details of the interior of the device 1. In operation, the air-permeable tape lies on the cover plate. On the band is then the web strip, which is acted upon by the cover plate and the air-permeable belt with negative pressure and thus firmly trapped on the outside of the air-permeable belt.

In the housing 3 six vacuum chambers 7-12 are provided. The vacuum chambers are separated by partitions 13-17. Each partition wall 13-17 has in plan view a V-shape, that is, two legs 18, 19, which extend at an angle of approximately 45 ° to the running direction 2.

Each vacuum chamber 7-12 is provided with at least one suction device in the form of a suction nozzle 20a-20e, 21-25. The first suction chamber 7 in the running direction 2 has a larger number of suction nozzles 20a-20e than the vacuum chambers 8-12 located further back in the running direction 2. In the present exemplary embodiment, the first vacuum chamber 7 has five suction nozzles 20a-2oee. But it is also possible to provide the first vacuum chamber 7 only with three or four suction nozzles.

The suction nozzles 20-25 are arranged in a bottom 26 of the vacuum chamber 7-12. The floor 26 is a grenzungswand, which is opposite to a guide side 27, along which the web strip is guided. On the guide side 27 is the air-permeable belt, on which the material web strip is located (not shown). The bottom 26 and the guide side 27 are parallel to each other with a distance in the range of 5 to 35 mm, preferably with a distance in the range of 10 to 20 mm.

As is apparent from Figs. 1 and 2, the Ξaugdüsen

20a-20e arranged in the first direction in the direction of 2 vacuum chamber 7 so that they fill the bottom 26. So there would be no room for another suction nozzle 20a-20e. As a result, it is possible not only to build up a negative pressure relatively quickly in the first vacuum chamber 7 when the web of material web is passed over the vacuum chamber 7, but to allow the negative pressure to act on the web of web material to a sufficient extent, if the mask terialbahnstreifen the vacuum chamber 7 has not yet completed.

In the other vacuum chambers 8-12, however, the respective suction nozzle 21-25 is arranged so that it is relatively close to the partition wall 13-17, so that it is still surmounted in the direction 2 on both sides of the respective partition wall 13-17. The suction nozzle 21-25 is, so to speak, in the "gusset ^{11 of} the" V ".

As can be seen in particular from FIG. 3, the housing 3 has an intermediate wall 28, which delimits the vacuum chambers 7-12. The intermediate wall 28 has two inclined side walls 29, 30 which are inclined in the direction of the suction nozzles 20-25. If the device 1 is arranged as shown in FIG. 3, ie, the material web strip is guided in the direction of gravity above the housing 3, then dirt particles or water droplets entering the vacuum chambers 7 - 12 will pass through Side walls 29, 30 directed towards the suction nozzle 20-25 so that they can be easily removed ^' . The same applies, however, in an operation "overhead", because even then creates an air flow, the dirt particles on the side walls 29, 30 and the bottom 26 abfördert.

Fig. 4 shows schematically a suction nozzle 23 in section. The suction nozzle 23 has a compressed air inlet 31 through which compressed air can be injected. The suction nozzle 23 also has a suction inlet 32. The compressed air entering through the compressed air inlet 31 passes through a gap between the differently hatched parts of the suction nozzle 23 and then flows out through an outlet 33. It tears suction air, which has entered through the suction inlet 32, with. The suction nozzle 23 operates on the venturi principle. Through the intermediate wall 28, the volume of Unterdruckkairanern 7-12 is kept small. It is possible to configure the intermediate wall 28 such that each vacuum chamber 7-12 has a volume of approximately 2 l or less, for example 1 l.

A compressed air supply line 34 is arranged in the housing 3 and between the intermediate wall 28 and the actual housing wall, so that the Druckluftver- sorgungsleitung 34 does not interfere to the outside in appearance. The compressed air supply line 34 is connected in each case via a branch line 35 with the respective suction nozzles 20-25.

A vacuum chamber 7-12 has a length in the direction of 2 of about 300 mm. At a web speed of 1,800 m / min, it takes about 1/100 second until a vacuum chamber 7-12 is covered by the web strip. Depending on the setting, a suction nozzle has a suction power of, for example, 4,500 l / min, so that about 1/5 second of approximately 0,75 l of air can be sucked out of each vacuum chamber 7-12. If the vacuum chamber 7-12 has a volume of 1 to 2 l, then the material web strip is reliably held as soon as it has run over a vacuum chamber 7-12. In order to build up the necessary negative pressure, it is not necessary to remove all the air from the vacuum chamber 7-12.

Since the partitions 13-17 have the illustrated V-shape {other shapes are also possible, as long as they do not run at right angles to the running direction 2), the material web strip is simultaneously acted upon by a negative pressure in two adjacent vacuum chambers 7-12 when it is conveyed in running direction 2, as soon as he starts to cross a partition 13-17. This avoids dead zones. It is also helpful here that the suction nozzles 21 - 25 are arranged relatively close behind the dividing walls 13 - 17 so that the substance produced thereby can be arranged. Pressure can also act relatively quickly on the web strip.

As can be seen from Fig. 3, the suction nozzles 20-25 open at practically the level of the bottom 26. In any case, they are arranged so that air is sucked through the bottom. This has a significant advantage for the self-cleaning effect of the device. When fibers, dust or water accumulate in the vacuum chambers 7-12, these contaminants are sucked by the suction nozzles 20-25 and blown out on the bottom of the device 1.

It is now possible to influence the force with which the material web strip is held and guided by the length of the device. A zone, i. a vacuum chamber 7-12 has a length of the order of 250 to 400 mm. Depending on how long you want to lead the web strip, then you have to switch more or less vacuum chambers 7-12 in a row.

In the first negative pressure chamber 7 in the running direction 2, for example, it is possible to generate a negative pressure of 28 mbar. In the subsequent vacuum chambers 8-12 then a negative pressure of 5 to 20 mbar is sufficient.

The suction nozzles 20-25 are arranged symmetrically with respect to a central axis 36. Thus, if a vacuum chamber 8-12 has only one suction nozzle 21-25, then this suction nozzle 21-25 is divided by the central axis 36. If, as in the first vacuum chamber 7, more

Suction nozzles 20a-20e are provided, then these sym- arranged metric to the central axis 36. As a result, pressure conditions can be realized in the vacuum chambers 7-12, which are also symmetrical to the central axis 36. A displacement of the material web strip by different pressures is virtually ruled out.

However, it may happen that the material web strip is already displaced laterally during cutting. In this case, it may be favorable to subdivide the individual vacuum chambers 7-12 parallel to the running direction 2 into two or three compartments. In a subdivision into two compartments, an intermediate wall would be arranged where the central axis 36 is located. In this case, each compartment is provided with its own suction nozzle 20-25, the first compartment of each row in the direction of running in turn having more suction nozzles than the downstream units.

If one makes the subdivision of the vacuum chambers 7-12 into individual compartments, then it will be expedient to design the partitions 13-17 also between the individual compartments in the direction of V-shaped in order to achieve the advantages mentioned above.

Claims

claims

1. An apparatus for guiding a material web strip in a running direction with a housing in which a vacuum generating device is arranged, characterized in that in the housing (3) in the running direction (2) behind a plurality of vacuum chambers (7-12) are arranged, each of which at least a suction device (20-25).

2. Apparatus according to claim 1, characterized in that in the running direction (2) of the material web strip first vacuum chamber (7) has a larger number of suction devices (20a-20e) than in the running direction (2) of the material web strip behind arranged vacuum chamber (8-12 ) having .

3. Device according to one of claims 1 to 2, characterized in that the suction devices are designed as suction nozzles (20-25).

4. Apparatus according to claim 2 or 3, characterized in that in the first vacuum chamber (7) has a boundary wall with suction means (20a-20e) is filled.

5. Device according to one of claims 1 to 4, characterized in that the vacuum chambers

(7-12) has a guide side (27) along which the material web strip runs and a bottom (26) lying opposite the guide side (27), the suction devices (20-25) acting through the bottom (26).

6. Apparatus according to claim 5, characterized marked, that the guide side (27) and the bottom

(26) extend parallel to each other.

7. The device according to claim 5 or 6, characterized in that the guide side (27) and the bottom (26) has a distance in the range of 5 to

35 mm, in particular in the range of 10 to 20 mm.

8. Device according to one of claims 1 to 7, character- ized in that the suction devices (20-25) with respect to a central axis (36) which is parallel to the running direction (2), are arranged symmetrically.

9. Device according to one of claims 1 to 8, character- ized in that at least two adjacent vacuum chambers (7-12) by a partition wall (13-17) are separated from each other, at least in sections an angle to the direction

(2) which is greater than 95 ° or less than 85 °.

10. The device according to claim 9, characterized in that the partition wall (13-17) has two legs (18, 19) which are inclined in opposite directions to the running direction (2).

11. The device according to claim 10, characterized in that the legs (18, 19) collide in a V-shape.

12. Device according to one of claims 9 to 11, characterized in that at least in a vacuum chamber (8-12), the partition wall (13-17) in the running direction (2) on both sides of the suction device (21-25).

13. Device according to one of claims 1 to 12, characterized in that the housing (3) has a vacuum chamber (7-12) delimiting intermediate wall (28).

14. The apparatus according to claim 13, characterized in that the intermediate wall (28) trough-shaped with inclined side walls (29, 30) is formed.

15. The apparatus according to claim 14, characterized in that the side walls (29, 30) are inclined in the direction of gravity to the suction device (20-25).

16. Device according to one of claims 13 to 15, characterized in that a compressed air supply line (34, 35) for the suction nozzles (20-25) between the housing (3) and the intermediate wall (28) is arranged.

17. Device according to one of claims 1 to 16, characterized in that a vacuum chamber

(7-12) has a volume of not more than 2 1, in particular not more than 1 1.

18. Device according to one of claims 1 to 17, characterized in that at least one vacuum chamber (7-12) is divided parallel to the running direction (2) in at least two compartments.

19. The apparatus according to claim 18, characterized in that each compartment in the direction of travel (2) is delimited by a V-shaped partition.