EP2147151B1 - Device for guiding a material web strip - Google Patents

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

The invention relates to a device for guiding a material web strip in a running direction with a housing in which a vacuum generating device is arranged, wherein in the housing in the direction of succession a plurality of vacuum chambers are arranged, each of which has at least one suction device.

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.

A paper web must be guided through various processing devices during its production and processing, including a dryer section, a press section, a calender and optionally a spreading or a sizing device. For this purpose, one goes in many cases so that one cuts a web strip with a width in the order of 200 to 300 mm at the edge of the paper web and this strip first passes through the processing facility. Once this strip of material has come so far that you can exercise a train on him, the paper web is cut to width, so that they can go through the corresponding processing facility 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 out EP 1 127 978 B1 known. 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 made EP 1 342 844 A2 known. 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 creates a negative pressure on the outside of the belt, with which the web or at least her web strip can be firmly sucked.

In the DE 20 2006 018 216 Ul there is described a vacuum belt conveyor having ejectors as vacuum applying devices arranged in successive suction spaces.

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 vacuum 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 a first vacuum chamber in the running direction of the material web strip has a larger number of suction devices than a arranged in the running direction of the material web strip behind vacuum chamber.

With this configuration, the time required to pressurize the web strip with the full vacuum is shortened. The web strip is guided over the housing and thereby 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 web strip. But as soon as the material web strip has completely covered the vacuum chamber, the negative pressure provided by the suction device acts in full on the vacuum Web strips. 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 some extent. However, the holding force, which is composed of area times negative pressure, in many cases still too low to hold the web strip as a whole safely. 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 vacuum located there also acts on the web of material. The holding force acting on the material web strip is thus constructed in sections.

In this case, a first vacuum chamber in the running direction 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 web strip is stabilized in this way over the first vacuum chamber, a lower negative pressure is sufficient to transport the web 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 suction devices 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 surrounding 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 a 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 one has only a suction device, such as a suction nozzle, in the vacuum chamber, then this suction nozzle 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. The partition thus 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 suction device is thus positioned relatively close behind the partition, so that the negative pressure can act relatively early on the web strip, so almost immediately if 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 is V-shaped, then the suction is, so to speak, 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. So you do not have to suck the entire housing empty to create the negative pressure.

Preferably, the intermediate wall is formed trough-shaped with inclined side walls. The inclined sidewalls contribute to a reduction in 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 device. 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 a maximum of 2 l, in particular a maximum of 1 l. One Such a small volume can be vacuumed relatively quickly, so that even high-speed material web strips, for example, have a speed in the order 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 web strip is cut from the web, then it may happen that it does not come to lie 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 delimited in the direction of travel by a V-shaped partition. 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, it is when crossing the partition then acted upon by the negative pressure in two adjacent compartments in the direction.

Fig. 1

eine perspektivische Darstellung einer Vor- richtung zum Führen eines Materialbahnstrei- fens im geöffneten Zustand,

Fig. 2

eine Draufsicht auf die Vorrichtung nach Fig. 1,

Fig. 3

einen Schnitt III-III nach Fig. 2 und

Fig. 4

eine Schnittansicht durch eine Saugdüse.

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

Fig. 1

3 a perspective view of a device for guiding a web of material web in the opened state,

Fig. 2

a plan view of the device according to Fig. 1 .

Fig. 3

a section III-III after Fig. 2 and

Fig. 4

a sectional view through a suction nozzle.

A device 1 for guiding a material web strip not shown in a running direction 2 has a housing 3, which is provided at its front end with a guide roller 4 and at its rear end with a guide 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 tape then lies the web of material that is acted upon by the cover plate and the air-permeable belt with negative pressure and thus sucked 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-20e. 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 boundary wall, which is opposite a guide side 27, along which the material web strip is guided. On the guide side 27 is the air-permeable belt on which the web strip is applied (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.

How out Fig. 1 and 2 As can be seen, the suction nozzles 20a-20e are arranged in the first vacuum chamber 7 in the running direction 2 so that they fill the bottom 26. So there would be no room for another suction nozzle 20a-20e. This makes it possible not only relatively quickly build a negative pressure in the first vacuum chamber 7 when the web of material is passed over the vacuum chamber 7, but to let the negative pressure already act on the web strip to a sufficient extent, if the web of material web vacuum chamber. 7 not finished yet.

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 located, so to speak, in the "gusset" of the "V".

As in particular from Fig. 3 shows, the housing 3 has an intermediate wall 28 which limits 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. When the device 1 is arranged as shown in FIG Fig. 3 is shown, the web strip is thus guided in the direction of gravity above the housing 3, then dirt particles or water droplets entering the vacuum chambers 7-12, passed through the side walls 29, 30 in the direction of the suction nozzle 20-25, so that they easily can be 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 schematically shows 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 the vacuum chambers 7-12 is kept small. The intermediate wall 28 can be designed 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 compressed air supply line 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 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 web of material web is simultaneously acted upon by a negative pressure in two adjacent vacuum chambers 7-12 when conveyed in running direction 2, as soon as he starts to cross a partition 13-17. This avoids dead zones. It is also helpful that the suction nozzles 21-25 are arranged relatively close behind the partitions 13-17, so that the negative pressure generated thereby can also act relatively quickly on the web strip.

How out Fig. 3 As can be seen, the suction nozzles 20-25 practically open at the level of the floor 26. In any case, they are arranged so that air is sucked through the floor. 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, a plurality of suction nozzles 20a-20e are provided, then they are symmetrical arranged 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 divide 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, wherein the first direction in the first compartment of each row in turn more suction nozzles than the downstream in the direction of the compartments.

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 (18)

1. Apparatus for guiding a material web strip in a running direction having a housing, in which a vacuum generating device is arranged, a plurality of vacuum chambers (7-12) being arranged in the housing (3) behind one another in the running direction (2), of which each has at least one suction device (20-25), characterized in that a first vacuum chamber (7) in the running direction (2) of the material web strip has a greater number of suction devices (20a-20e) than a vacuum chamber (8-12) which is arranged behind it in the running direction (2) of the material web strip.
2. Apparatus according to Claim 1, characterized in that the suction devices are configured as suction nozzles (20-25).
3. Apparatus according to Claim 2, characterized in that a boundary wall is filled with suction devices (20a-20e) in the first vacuum chamber (7).
4. Apparatus according to one of Claims 1 to 3, characterized in that the vacuum chambers (7-12) have a guiding side (27), along which the material web strip runs, and a base (26) which lies opposite the guiding side (27), the suction devices (20-25) acting through the base (26).
5. Apparatus according to Claim 4, characterized in that the guiding side (27) and the base (26) extend parallel to one another.
6. Apparatus according to Claim 4 or 5, characterized in that the guiding side (27) and the base (26) are at a spacing in the range from 5 to 35 mm, in particular in the range from 10 to 20 mm.
7. Apparatus according to one of Claims 1 to 6, characterized in that the suction devices (20-25) are arranged symmetrically in relation to a centre axis (36) which extends parallel to the running direction (2).
8. Apparatus according to one of Claims 1 to 7, characterized in that at least two adjacent vacuum chambers (7-12) are divided from one another by a dividing wall (13-17) which encloses at least in sections an angle with respect to the running direction (2), which angle is greater than 95° or smaller than 85°.
9. Apparatus according to Claim 8, characterized in that the dividing wall (13-17) has two limbs (18, 19) which are inclined in opposite directions with respect to the running direction (2).
10. Apparatus according to Claim 9, characterized in that the limbs (18, 19) abut one another in a V-shape.
11. Apparatus according to one of Claims 8 to 10, characterized in that, at least in the case of one vacuum chamber (8-12), the dividing wall (13-17) extends on both sides of the suction device (21-25) in the running direction (2).
12. Apparatus according to one of Claims 1 to 11, characterized in that the housing (3) has an intermediate wall (28) which delimits the vacuum chamber (7-12).
13. Apparatus according to Claim 12, characterized in that the intermediate wall (28) is configured in the shape of a trough with inclined side walls (29, 30).
14. Apparatus according to Claim 13, characterized in that the side walls (29, 30) are inclined toward the suction device (20-25) in the direction of gravity.
15. Apparatus according to one of Claims 12 to 14, characterized in that a compressed air supply line (34, 35) for the suction nozzles (20-25) is arranged between the housing (3) and the intermediate wall (28).
16. Apparatus according to one of Claims 1 to 15, characterized in that a vacuum chamber (7-12) has a volume of at most 2 l, in particular of at most 1 l.
17. Apparatus according to one of Claims 1 to 16, characterized in that at least one vacuum chamber (7-12) is divided into at least two compartments parallel to the running direction (2).
18. Apparatus according to Claim 17, characterized in that each compartment is delimited in the running direction (2) by a V-shaped dividing wall.

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