EP2360314B1 - Transfer belt - Google Patents

Description

The invention relates to a machine for producing a material web, in particular a paper, cardboard or tissue web.

EP1496152 discloses a machine with a roll shell for a shoe press roll. The underside of the roll jacket comes into contact with a press shoe, the underside of the roll jacket sliding over the press shoe. Furthermore, according to the publication, the top of the roll shell comes into contact with a felt.

The DE1155972 shows a machine with a belt (called "follower" there) in the form of a fabric or a perforated film by means of which a paper web is guided through a wet press. This means that the tape disclosed in the publication is permeable.

Paper, cardboard or tissue machines can have central roller presses. In the central roll presses known from the prior art with one roll and several counter rolls assigned to this roll, each of which forms a press nip with the roll, the moist fibrous web is pulled off the smooth roll (central roll) by an open pull. Considerable pull-off forces are exerted on the fibrous web.

DE 100 55 708 A1 discloses a roll cover or press belt for a paper machine. It describes grooves worked into the radially outermost surface of the roll cover or the rotating press belt. These grooves are thus made on the upper side of the roll cover or press belt.

DE 199 57 617 A1 describes storage volumes in the form of knobs on the radial outer surface of a drainage belt.

In order to reduce the pull-off forces, the prior art proposes a transfer belt looping around the central roll, with which the fibrous web is guided through the press nips and from which the fibrous web can be removed by means of a suction suction roll, for example.

If moisture penetrates the wrapping area between the central roller and the transfer belt, slippage occurs between the driven central roller and the moving transfer belt, which leads to aquaplaning. As a result, the drive power of the central roller can only be insufficiently transferred to the transfer belt, which can lead to web breaks or to the transfer belt running away and, associated with this, damage to the machine.

The object of the present invention is to propose a machine for producing a material web, in particular for a paper, cardboard or tissue machine, which comprises an endless belt, in particular a transfer belt, the use of which can prevent or at least reduce the problems described above. The object is achieved by a machine for producing a material web, in particular a paper, cardboard or tissue web, according to independent claim 1.

The known endless belt, in particular transfer belt, has an upper side and an underside arranged opposite the upper side, with the upper side being able to be brought into contact with the material web, in particular with the paper, cardboard or tissue web, and the underside with the machine when the endless belt is to be used is.

In the case of the endless belt according to the invention, it is also provided that the endless belt has a storage volume for receiving fluid which acts on the underside.

As a result of the solution according to the invention, the fluid acting on the underside of the endless belt is at least partially absorbed in the endless belt. As a result, the fluid can be carried away from the contact area between the outer surface of a roller and the underside of the endless belt. Therefore, the fluid acting on the underside of the endless belt, for example water and / or air, cannot or only conditionally build up as a fluid layer between the outer surface of the roller and the underside of the endless belt. In this way, especially in the press nip, the risk of aquaplaning between the endless belt and the roll shell is prevented or at least considerably reduced.

It is possible to provide the storage volume at least partially through an at least partially porous structure of the endless belt. The porous structure can, for example, comprise a fleece and / or a woven fabric and / or a foamed structure which extends at least in the area of the underside of the endless belt.

If a porous structure is exposed to the changing pressure load in the press nip over a longer period of time, it is increasingly compacted, as a result of which its fluid storage volume is progressively reduced. In order to circumvent this problem, the invention provides that the storage volume is at least partially provided by the surface structure of the underside.

Since the fluid storage volume of the endless belt according to the invention is limited, a preferred embodiment of the invention provides that the surface structure is designed such that fluid can be carried away from the press nip when it passes through a press nip. In this way, the risk of aquaplaning on the underside can be further reduced, in particular when passing through a press nip and when a large amount of fluid is exposed. The surface structure can form a regular or an irregular pattern.

In this case, the surface structure is preferably designed in such a way that the storage volume is essentially retained in a press nip when subjected to pressure.

It is also conceivable that the endless belt has a storage volume that changes transversely to the direction of travel. In this way, for example, drag effects in the edge area of the endless belt can be compensated for. In this context, it is, for example, conceivable that the surface structure forms a regular pattern in sections and an irregular pattern in sections on the underside.

According to a specific configuration of the embodiment mentioned above, the surface structure comprises a grooving. A grooving in the underside provides a good storage effect and a good water drainage capacity.

The effect of the grooving is particularly effective when it extends at least in sections along the running direction of the endless belt. The best results are achieved when the scoring extends essentially longitudinally to the direction of travel of the endless belt.

Tests have shown that sufficient stability coupled with good fluid storage volume and good fluid discharge capacity is provided when the ratio of land width to groove width is between 0.5 and 10.

The grooves in this case preferably have a width between 0.2 and 10 mm, preferably between 1 and 5 mm, the depth of the grooves advantageously being less than 50% of the total thickness of the endless belt.

An irregular surface structure can be provided, for example, in that the distance and / or the cross-sectional area and / or the shape of at least two adjacent grooves is different.

The underside is preferably formed by a permeable or impermeable polymeric layer, the surface structure being produced during the production of the polymeric layer and / or after the production of the polymeric layer.

The surface structure can be produced, for example, during the production of the polymer layer by casting or molding. Furthermore, after the production of the polymer layer, the surface structure can be produced by mechanical and / or thermal and / or chemical processing of the polymer layer.

Tests have shown that the aquaplaning effect, in particular when using the endless belt in a press arrangement, can be particularly reduced if the storage volume is between 5 and 1000 milliliters per m ^{2 of} surface area of the underside, preferably between 50 and 500 milliliters per m ^{2 of} area of the underside amounts to.

According to the invention, a machine for producing a material web, in particular a paper, cardboard or tissue web, with a roller with a jacket surface and with an endless belt, in particular a transfer belt, wrapping around the jacket surface in sections is proposed. The endless belt has an underside which can be brought into contact with the lateral surface in the wraparound area, with a through the endless belt and / or the roller Storage volume is provided which is suitable to at least partially absorb fluid which penetrates in the wraparound area between the underside and the lateral surface.

The machine according to the invention prevents a fluid film from building up in the contact area between the underside of the endless belt and the outer surface of the roller. In this way, the risk of aquaplaning between the endless belt and the roller can be effectively minimized, if not prevented at all.

According to the invention, the underside has a surface structure to form the storage volume and the outer surface is smooth. Alternatively, both the underside and the jacket surface each have a surface structure to form the storage volume.

According to the invention, the surface structure of the lateral surface comprises, alone or in combination, a grooving or a roughness of the lateral surface or a regular or irregular structure.

Such a structure is achieved by embossing.

Different materials, alone or in combination, are conceivable for forming the outer surface of the roller, such as, for example, metal or plastic or rubber. Plastic can be, for example, a thermoplastic or a thermosetting plastic.

In order to provide, in addition to the fluid storage volume, the ability to discharge fluid from the contact area between the underside of the endless belt and the outer surface of the roller, a preferred embodiment of the invention provides that the grooves run essentially in the circumferential direction of the outer surface.

Tests have shown that the aquaplaning effect, especially when using the roller in a press arrangement, can be particularly reduced if the storage volume of the jacket surface is up to 2000 milliliters per m ^{2 of} surface area, preferably between 500 and 1500 milliliters per m ^{2 of} surface area Lateral surface is.

Furthermore, tests have shown that sufficient stability coupled with good fluid storage volume and good fluid discharge capacity can be provided if the ratio of the web width to the groove width of the grooves on the lateral surface is between 0.5 and 10.

The grooves of the lateral surface preferably have a width between 0.2 and 10 mm, preferably between 1 and 5 mm. The ratio of groove depth to groove width is preferably between 10 and 0.2.

In the machine according to the invention, the roller preferably forms a press nip with a counter roller, the endless belt and a fibrous web being guided through the press nip and the endless belt being brought into contact with the roller when passing through the press nip.

Of course, the roller can also be a shoe press roller with a circumferential jacket. In this case, the claim should be understood to mean that the endless belt is brought into contact with the circumferential jacket of the shoe press roll when it is passed through the press nip.

According to a particularly preferred embodiment of the invention, the roller is assigned at least two counter-rollers, the counter-rollers each forming a press nip with the roller, through which the endless belt and a fibrous web are passed, and the endless belt with the roller in each case when passing through each of the press nips Contact is brought. Such a press arrangement is called a central roller press. Here, the above-mentioned roller forms the central roller.

The underside of the endless belt is preferably scraped and / or cleaned outside of the wrapping area. As a result of the doctoring, a noticeable proportion of the fluid, water and / or air, carried along on the underside of the endless belt can be scraped off. In this way, the risk of aquaplaning can also be effectively reduced in the case of a surface structure on the underside that is, for example, only formed by a roughness. Since impurities often form adhesion points for fluid and thus more fluid is carried along on a contaminated underside, the risk of aquaplaning can also be reduced by cleaning the underside.

In order to increase the service life of the endless belt, it makes sense if at least one scraper assigned to the underside is a soft scraper, i.e. a plastic scraper that is not fiber-reinforced, in particular not reinforced with glass and / or carbon fiber. In this context, a non-fiber-reinforced PE scraper with a thickness of, for example, 6mm should be mentioned specifically. Such a scraper is sold under the name Clouth AS, for example.

Good wiping results are achieved, for example, if at least one scraper assigned to the underside is a scraper that can be blown out at the scraper tip. Such a scraper is also called a blow scraper.

A gentle treatment and an associated increase in the service life of the endless belt coupled with a very good scraping effect is achieved if at least one scraper assigned to the underside has an angle of incidence relative to the underside of less than 25 °, in particular between 5 ° and 15 °.

In addition or as an alternative to conditioning the underside of the endless belt, at least one scraper for wiping off fluid and / or at least one spray tube for cleaning it can be assigned to the outer surface of the roller outside of the wraparound area. The advantages previously described in the conditioning of the underside also apply to this embodiment of the invention.

Fiber-reinforced plastic blades are particularly suitable for doctoring the roller. Such doctor blades are sold, for example, under the name Clouth C2 or C100.

Fig. 1

eine erfindungsgemäße Maschine mit einer Zentralwalzenpresse,

Fig. 2

ein erfindungsgemäßes Endlosband in Draufsicht,

Fig. 3

verschiedene Varianten von Rillungen für erfindungsgemäße Endlosbänder oder Walzenmäntel im Querschnitt,

Fig. 4

verschiedene Varianten von Oberflächenstrukturen für erfindungsgemäße Endlosbänder oder Walzenmäntel in Draufsicht auf die Unterseite bzw. auf die Mantelfläche.

The invention will be explained in more detail below with reference to the following schematic drawings. Show it:

Fig. 1

a machine according to the invention with a central roller press,

Fig. 2

an endless belt according to the invention in plan view,

Fig. 3

different variants of grooves for endless belts or roller shells according to the invention in cross section,

Fig. 4

different variants of surface structures for endless belts or roller shells according to the invention in a plan view of the underside or of the outer surface.

The Figure 1 shows a machine 1 according to the invention with a central roller press 2. The central roller press 2 comprises a roller 3, also called a central roller 3. The central roller 3 has a smooth lateral surface 4.

The central roller 3 is assigned two counter-rollers 5 and 6, each of which forms a press nip 7 and 8 with the central roller 3. The central roll 3 is also wrapped in sections by a transfer belt 9 in such a way that the transfer belt 9 is guided through the two press nips 7 and 8.

The transfer belt 9 has an upper side 11 which can be brought into contact with a fibrous web 10, as well as an underside 12 which contacts the lateral surface 4 of the roller 3 in the entire wrapping area.

The fibrous web 10 and the transfer belt 9 are guided together through the two press nips 7 and 8, the transfer belt 9 being in contact with the roller 3. In the present embodiment, a surface structure of the underside 12 provides a storage volume which is suitable for at least partially absorbing water and / or air that penetrates into the wraparound area between the underside 12 and the lateral surface 4.

In the present embodiment, the underside 12 of the transfer tape 9 is formed by a polymer layer, such as, for example, polyurethane, the surface structure being formed by a grooving with grooves 15, these form depressions in the underside 12, and webs 16 arranged between them during the manufacture of the lower side 12, for example by casting (see Figure 2 ).

The grooves 15 extend here essentially along the running direction (MD direction) of the endless belt 9, whereby fluid can be taken up and carried away from the press nip as it passes through a press nip. The underside 12 is designed in such a way that the storage volume is essentially retained in a press nip when pressure is applied.

The ratio of land width to groove width is two, with the grooves being 3mm wide. The surface structure of the underside 12 provides a storage volume of 400 milliliters per m ^{2 of} area of the underside 12.

Furthermore, a scraper 13 for wiping off fluid and a spray tube 14 for cleaning the underside 12 are assigned to the underside 12 of the endless belt 9 outside the wraparound area.

The scraper 13 is a soft scraper, plastic scraper without fiber reinforcement. The setting angle of the scraper 13 is approx. 10 ° relative to the underside 12.

In addition, scrapers 17 and 18 for wiping off fluid and spray tubes 19 and 20 for cleaning the jacket surface 4 are assigned to the jacket surface 4 of the roller 3 outside the wraparound area.

Before the fibrous web 10 runs through the central roll press 2, it runs between two press felts 23 and 24 through a press nip 22 formed between the counter roll 5 and another roll 21, the press felt 23 also being guided through the press nip 7 formed between the central roll 3 and counter roll 5 , so that the fibrous material 10 contacts the press felt 23 on one side and the transfer belt 9 on its other side as it passes through the press nip 7.

When passing through the press nip 8 formed between the central roller 3 and the counter roller 6, the fibrous material 10 also contacts a press felt 25 on one side and the transfer belt 9 on its other side.

After the fibrous web 10 has passed through the central roller press 2, the fibrous web 2 is removed from the transfer belt 9 by means of a vacuum pick-up roller 26 and transferred to a covering 27.

The Fig. 3 shows various variants of grooves for endless belts or roller shells according to the invention in cross section.

When displaying the Figure 3a the grooves 15 have a semicircular cross-section.

When displaying the Figure 3b the grooves 15 have a trapezoidal cross-section.

When displaying the Figure 3c the grooves 15 have a triangular cross-section.

The Fig. 4 shows different variants of surface structures for endless belts or roller shells according to the invention in a plan view of the underside 12 or the lateral surface 4.

When displaying the Figure 4a the surface structure has irregularly formed grooves 15 which form depressions.

When displaying the Figure 4b the surface structure has grooves 15 which extend diagonally to the running direction (MD direction) and form depressions.

When displaying the Figure 4c the surface structure has diamond-shaped elevations 28.

Claims (14)

1. Machine (1) for producing a material web, in particular a paper web, cardboard web, or tissue web, having a roller (3) having a shell face (4) and having a continuous belt, in particular a transfer belt (9), which in portions wraps the shell face (4) of the roller (3) and which has a lower side (12) which in the wrapping region is brought into contact with the shell face (4), wherein a storage volume which is suitable for at least in part receiving fluid which in the wrapping region enters between the lower side (12) and the shell face (4) is provided by the continuous belt, wherein the lower side (12) for forming the storage volume has a surface structure, and the shell face (4) is smooth, or the lower side (12) and the shell face (4) for forming the storage volume have in each case a surface structure, characterized in that the surface structure comprises a groove structure, a roughness of the shell face (4), or an embossed structure.
2. Machine (1) according to Claim 1,
   characterized in that
   the shell face (4) is formed solely by or in combination with metal, plastics material, rubber.
3. Machine (1) according to Claim 1 or 2,
   characterized in that
   the groove structure runs substantially in the circumferential direction of the shell face (4).
4. Machine (1) according to one of Claims 1 to 3,
   characterized in that
   the storage volume of the shell face (4) is up to 2000 millilitres per m² of area of the shell face (4), preferably between 500 and 1500 millilitres per m² of area of the lower side (12).
5. Machine (1) according to one of Claims 1 to 4,
   characterized in that
   the ratio of web width to groove width is between 0.5 and 10.
6. Machine (1) according to one of Claims 1 to 5,
   characterized in that
   the grooves have a width between 0.2 and 10 mm, preferably between 1 and 5 mm.
7. Machine (1) according to one of Claims 1 to 6,
   characterized in that
   the ratio of groove depth to groove width is between 10 and 0.2.
8. Machine (1) according to one of Claims 1 to 7,
   characterized in that
   the roller (3) conjointly with a counter roller forms a press nip through which the continuous belt and a fibrous web (10) are guided, wherein the continuous belt is in contact with the roller (3).
9. Machine (1) according to one of Claims 1 to 8,
   characterized in that
   the roller (3) is assigned at least two counter rollers which conjointly with the roller (3) form in each case one press nip and through which the continuous belt and a fibrous web (10) are in each case guided, wherein the continuous belt is in each case in contact with the roller (3).
10. Machine (1) according to one of Claims 1 to 9,
    characterized in that
    the lower side (12) of the continuous belt outside the wrapping region is assigned at least one doctor (13) for wiping fluid and/or at least one spray pipe for cleaning said lower side (12).
11. Machine (1) according to Claim 10,
    characterized in that
    at least one doctor (13) assigned to the lower side (12) is a plastics-material doctor which is not fibre-reinforced, in particular not reinforced with glass fibre and/or carbon fibre.
12. Machine (1) according to Claim 10 or 11,
    characterized in that
    at least one doctor (13) assigned to the lower side (12) is a ventilating doctor.
13. Machine (1) according to one of Claims 10 to 12,
    characterized in that
    at least one doctor (13) assigned to the lower side has an approach angle relative to the lower side (12) of less than 25°, in particular between 5° and 15°.
14. Machine (1) according to one of Claims 1 to 13,
    characterized in that
    the shell face (4) of the roller (3) outside the wrapping region is assigned at least one doctor (17, 18) for wiping fluid and/or at least one spray pipe for cleaning said shell face (4).

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