EP2233418A2 - Device for guiding a material web strip - Google Patents

Abstract

The device (1) has a housing (3) in which low-pressure chambers (7-10) are consecutively arranged in a running direction (2). The low-pressure chambers comprise suction devices (23) i.e. suction nozzles (20a-20d). One of the chambers is extended to a part in an outlet godet (12) between a deflection roller (4.1) and a circumferential band (17) in the running direction. The suction devices are inclined with a suction direction against the running direction. The suction direction is tangentially fixed towards a circumference of the deflection roller.

Description

The invention relates to a device for guiding a material web strip with a circulating around deflection rollers air-permeable belt and a housing in which a plurality of vacuum chambers are arranged one behind the other in the running direction, 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. In many cases, this is done by cutting a strip of material web having a width of the order of 100 to 300 mm at the edge of the paper web and first guiding this strip through the processing device. Once this strip of material has come so far that you can exercise a train on him in the next processing station, the paper web is cut to width, so that they can pass 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 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.

For this reason, in the DE 10 2007 023 215 A1 already presented a vacuum transfer belt, which is divided into a plurality of vacuum chambers, each vacuum chamber having at least one suction device.

It is particularly difficult to take over the beginning of the material web strip from a delivery surface, which may be a drying cylinder surface, for example, on the tape. The setting of known in this environment blowing nozzles is very complex and the vacuum chambers act only in the direction behind the guide roller through the belt.

Therefore, it has even been suggested that the deflection roller of the belt, in the vicinity of which the beginning of the material web strip should run onto transfer belt, be aspirated. Exemplary in this context is the EP 1440926 B1 called. It is easy to see that the production cost of such an absorbable deflection roller is very large.

The invention has for its object to make a web strip easier from a delivery surface to the receiving position on the tape feasible.

This object is achieved in a device of the type mentioned above in that the first vacuum chamber in the running direction extends to a part in the Auslaufzwickel between a guide roller and the circulating belt and at least one suction device of the first vacuum chamber is inclined with its suction towards the direction, wherein the suction direction is set approximately tangentially to the circumference of the guide roller.

With this embodiment, not only the distance of the web of material web strip is greatly shortened until the acquisition on the tape. The suction effect of the device extends significantly further in the direction of the discharge surface of the material web strip. When a web of material from a drying cylinder (from which it runs for a while in the pulper of the paper machine) should be lifted and transported onto the belt, so in the embodiment of the present invention, a small blast of air from a laterally disposed air nozzle to the web strip in the detection area to bring the first suction zone. The first suction chamber is bring with the inventive design of the device very close to the delivery surface of the material web strip.

For the invention, it is particularly essential that the suction device can develop its suction effect, as it were, across the inlet-side deflection roller. This is not achieved only by the inclination of the suction device (which incidentally already in DE 20 2006 018 215 U1 , Figure 8 is indicated), but only in combination with the fact that the first vacuum chamber in the running direction extends to a part in the Auslaufzwickel between a guide roller and the circulating belt. A fictitious Saugrichtungslinie can therefore tangentially - and optionally deflected against the direction of rotation of the suction - continue past the first guide roller through the perforation of the tape in the direction of discharge surface for the web strip. There, the suction device detects the web strip much earlier than in devices in the state the technology, apart from the elaborate vacuum transfer belts, the guide rollers are already sucked. It is irrelevant if, in addition, a thin separating plate, which is arranged very close to the deflection roller and possibly assumes its curvature, is present in the outlet gusset, as it reduces the suction space only insignificantly.

As already in the DE 10 2007 023 215 A1 described, the realization of several vacuum chambers, the time required to apply the web strip with the full negative pressure, 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. However, as soon as the material web strip has completely covered the vacuum chamber, the negative pressure provided by the suction device acts in its entirety on the material web strip. Since a plurality of vacuum chambers are arranged one behind the other in the running direction, the length of each vacuum chamber is shorter than that of the overall device. If the material web strip is held in the running direction on the first vacuum chamber, then it is already stabilized to some extent. The length of the first vacuum zone is preferably relatively short and limited to less than 80 mm. 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.

Preferably, 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 is already held with a high reliability on a sieve or other air-permeable belt 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. Here are particularly suitable nozzles that operate on the venturi principle.

Advantageously, this is ensured if the air velocity at the inlet in the outlet gusset is still greater than 12 m / s above the strip during the intake process. With such a large suction speed, it is ensured that the material web strip is grasped securely and can be deposited on the belt. In many cases, especially in light paper grades, not even an additional separating element for the transverse cutting of the material web strip is more necessary.

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 run can accumulate practically no dirt 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.

It is advantageous if the suction devices of the vacuum chamber following the first vacuum chamber in the running direction are likewise inclined towards the running direction. And here it is particularly preferred if the inclination angle decreases in the direction of vacuum chamber to vacuum chamber. In order to make the structure of the device as simple as possible, it was sufficient if the suction direction, which is still clearly aligned with the first vacuum chamber in the direction of discharge surface, moves from vacuum chamber to vacuum chamber in the direction perpendicular to the belt. A structure of such a vacuum chamber is easier to accomplish.

Advantageously, the suction devices are arranged symmetrically with respect to a central axis which runs 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.

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 direction. This also facilitates the removal of dirt.

Preferably, a compressed air supply line for the suction device 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 l, in particular at most 1 l. Such a small volume can be sucked up 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.

The device preferably has two deflection rollers for the delivery surface of the material web strip. With the intention of bringing the first negative pressure zone closer to the delivery surface of the material web strip, it is not easy to reduce a single deflection roll since the strains on the belt would be too great due to the large radius of deflection. In addition, this would be lost installation height, which is needed for the suction nozzles. For this reason, two smaller guide rollers are used.

Preferably, the diameter of at least one guide roller is less than 60 mm. Such a diameter makes it possible to bring the first suction zone very close to the discharge surface of the material web strip.

Fig. 1

einen Teillängsschnitt einer Vorrichtung zum Führen eines Materialbahnstreifens,

Fig. 2

eine Schnittansicht durch eine Saugdüse

Fig. 3

einen Querschnitt durch eine Vorrichtung zum Führen eines Materialbahnstreifens

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

Fig. 1

a partial longitudinal section of an apparatus for guiding a material web strip,

Fig. 2

a sectional view through a suction nozzle

Fig. 3

a cross section through an apparatus for guiding a web of material

A device 1 for guiding a material web strip in a running direction 2 comprises a housing 3, which is provided at its front end with two pulleys 4.1 and 4.2 and at its rear end in a manner not shown with a deflection roller. For the guide roller 5 at the rear end is a drive pin 6 ( Fig. 3 ), to which a non-illustrated drive motor can be connected. About the pulleys 4.1, 4.2, 5, an air-permeable belt 17 is guided. This band 17 may be formed, for example, as a sieve.

The housing 3 has a cover plate 18 which is provided with openings, for example in the form of slots. In operation, the air-permeable belt 17 rests on the cover plate 18. On the belt 17 then the web strip 11, which is acted upon by the cover plate 18 and the air-permeable belt 17 with negative pressure and thus firmly sucked on the outside of the air-permeable belt 17.

The web strip 11 is removed from a delivery surface 19. This delivery surface is in the embodiment of Fig. 1 formed by the surface of a drying cylinder 22. From there, the material web strip (dash-dotted line) runs for a while in the pulper 21 until it is sucked in and taken over by the device 1 and forwarded according to reference numeral 11.

Fig. 1 shows in section of the housing 3 four vacuum chambers 7-10. The vacuum chambers are separated by partitions 13-15.

Each vacuum chamber 7-10 is provided with at least one suction device 23 in the form of a suction nozzle 20a-20d. At least in the direction of 2 first suction chamber 7 in this case has a suction nozzle 20a, which is tilted counter to the direction 2. The suction direction runs tangentially to the guide roller 4.1. In this case, the first vacuum chamber 7 is separated only by a closely adjacent to the guide roller plate 16 thereof. The first vacuum chamber 7 thus also extends into the outlet gusset 12 between guide roller 4.1 and belt.

As a result, a very short distance between the discharge surface 19 and the beginning of the first vacuum chamber 7 is created in a simple manner, which greatly facilitates the transfer of the material web strip on the tape. This distance is limited in prototypes to just under 60 mm.

It has been found to be advantageous if the angle of inclination of the suction nozzles 20b-20d of the following vacuum chambers 8-10 is successively reduced until it has arrived at zero. In the rear vacuum chambers in the direction of the suction direction must not be aligned with the discharge surface.

Fig. 1 does not show again that in each vacuum chamber 7-10 and a plurality of suction nozzles 20a-20d side by side, so can be arranged perpendicular to the direction 2. This depends on the width of the device. Often it is favorable, at least in the first vacuum chamber 7 to accommodate a plurality of suction nozzles 20a to increase the suction power.

The suction nozzles 20a-20d are arranged in a bottom 26 of the vacuum chambers 7-10. The bottom 26 is a boundary wall, which is opposite to a guide side 27, on which the web strip is guided along. On the guide side 27 is the air-permeable belt on which the web of material lies. The bottom 26 and the guide side 27 can be 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. The parallelism of the bottom 26 to the guide side 27 is particularly in the region of the vacuum chamber 10 in Fig. 1 recognizable.

Fig. 2 schematically shows a suction device 23 in section. The suction device 23 in the form of a nozzle has a compressed air inlet 31 through which compressed air can be injected. The suction device 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 and then flows out through an outlet 33. It tears suction air, which has entered through the suction inlet 32, with. The suction nozzle works on the venturi principle.

As in particular from Fig. 3 shows, the housing 3 has an intermediate wall 28 which limits the vacuum chambers 7-10. The intermediate wall 28 has two inclined side walls 29, 30, which are inclined in the direction of the suction nozzles 20a-20d. 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 7-10, 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.

Through the intermediate wall 28, the volume of the vacuum chambers 7-10 is kept small. The intermediate wall 28 can be designed so that each vacuum chamber 7-10 has a volume of about 2 l or less, for example 1 l.

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

The first nozzle in the running direction has a maximum length also in the direction of 2 of 80 mm. A following vacuum chamber 8-10 has a length in the direction of 2 from 80 to 300 mm. At a web speed of 1,800 m / min, it takes about 1/100 second until a vacuum chamber 7-10 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 1/75 second of approximately 0,75 l of air can be sucked out of each vacuum chamber 7-10. If the vacuum chamber 7-10 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 7-10. In order to build up the necessary negative pressure, it is not necessary to remove all the air from the vacuum chamber 7-10. 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 following vacuum chambers 8-10 then a negative pressure of 5 to 20 mbar is sufficient.

How out Fig. 3 As can be seen, the suction devices 23 open practically at the level of the bottom 26. In any case, they are arranged so that air is sucked through the ground. This has a significant advantage for the self-cleaning effect of the device. When fibers, dust or water accumulate in the vacuum chambers 7-10, these contaminants are sucked by the suction nozzles 20a-20d and blown out on the bottom of the device 1.

The suction nozzles 20a-20d are arranged symmetrically with respect to a central axis. Thus, if a vacuum chamber 8-10 has only one suction nozzle 20a-20d, then this suction nozzle is divided by the central axis 36. If, as in the first vacuum chamber 7, a plurality of suction nozzles 20a are provided, then these are arranged symmetrically to the central axis. As a result, pressure conditions can be realized in the vacuum chambers 7-10, which are also symmetrical to the central axis are. 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 7-10 parallel to the running direction 2 into two or three compartments. In a subdivision into two compartments, an intermediate wall would be located where the central axis is located. In this case, each compartment is provided with its own suction nozzle 20a-20d.

LIST OF REFERENCE NUMBERS

1

Device for guiding a web strip

2

direction

3

casing

4.1, 4.2

Inlet-side deflection roller

5

deflecting

6

drive journal

7 - 10

Vacuum chamber

11

Web strips

12

outlet pocket

13 - 15

partition wall

16

Divider

17

tape

18

cover plate

19

release area

20a - 20d

suction nozzle

21

pulper

22

drying cylinders

23

suction

26

ground

27

guide side

28

partition

29

Side wall

30

Side wall

31

Compressed air inlet

32

suction inlet

33

output

34

Compressed air supply line

35

branch line

Claims (15)

Device for guiding a material web strip (11) with an air-permeable belt (17) revolving around deflecting rollers (4.1, 4.2, 5) and with a housing (3) in which a plurality of vacuum chambers (7-10) are arranged in succession in the running direction (2) each of which has at least one suction device (23), characterized in that in the running direction (2) first vacuum chamber (7) extends in part into the outlet gusset (12) between a deflection roller (4.1) and the circulating belt (17) and at least one suction device (23) of the first vacuum chamber (7) with its suction direction against the running direction (2) is inclined, wherein the suction direction is set approximately tangentially to the circumference of the guide roller (4.1). Device according to claim 1,
characterized in that
a first vacuum chamber (7) in the running direction (2) has a larger number of suction devices (23) than a vacuum chamber (8) arranged behind it in the running direction (2). Device according to one of claims 1 to 2,
characterized in that
the suction devices are designed as suction nozzles (20a-20d). Device according to one of claims 1 to 3,
characterized in that
the air velocity at the inlet gating, still above the belt, is greater than 12 m / s during the intake process. Device according to one of claims 1 to 4,
characterized in that
the vacuum chambers (7-10) have a guide side (27) along which the web strip runs and a bottom (26) opposite the guide side (27), the suction means (23) acting through the bottom (26). Device according to one of claims 1 to 5,
characterized in that
the suction nozzles (20b-20d) of the first vacuum chamber in the running direction (2) following vacuum chambers (8-10) are also inclined against the direction of rotation 2. Device according to claim 6,
characterized in that
the angle of inclination of the suction nozzles (20a-20d) decreases in the running direction (2) from vacuum chamber to vacuum chamber. Device according to one of claims 1 to 7,
characterized in that
the suction nozzles (20a-20d) are arranged symmetrically with respect to a central axis of the device (1) which is parallel to the running direction (2). Device according to one of claims 1 to 8,
characterized in that
the housing (3) has a negative pressure chamber (7-10) delimiting intermediate wall (28). Device according to claim 9,
characterized in that
the intermediate wall (28) is formed trough-shaped with inclined side walls (29, 30). Device according to claim 10,
characterized in that
the side walls (29, 30) are inclined in the direction of gravity towards the suction device (23). Device according to one of claims 9 to 11,
characterized in that
a compressed air supply line (34, 35) for the suction direction (23) between the housing (3) and the intermediate wall (28) is arranged. Device according to one of claims 1 to 12,
characterized in that
a vacuum chamber (7-10) has a volume of at most 2 l, in particular at most 1 l. Device according to one of claims 1 to 13,
characterized in that
the device (1) to the delivery surface (19) of the web of material strip (11) towards two guide rollers (4.1, 4.2). Device according to claim 14,
characterized in that
the diameter of at least one deflection roller (4.1, 4.2) is less than 60 mm.

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