DE102019124680A1 - Device and method for producing a fibrous web - Google Patents

Abstract

The invention relates to a device (10) for producing a fibrous web (FB), in particular a tissue paper web, comprising a forming section (12) for forming the fibrous web (FB), the forming section (12) having a gap former with a headbox (18), a comprises a first covering (20) and a second covering (22); a press section (14) for pressing the formed fibrous web (FB), the press section (14) comprising a first press element (26) and a second press element (28) which together form a press nip through which, when the device (10 ) the first covering (20), a third covering (34) and the fibrous web (FB) between them are guided; and a dryer section (16) for further drying the pressed fibrous web (FB), wherein the dryer section (16) comprises a drying cylinder (50) to which the fibrous web (FB) transported on the third clothing (34) is transferred The transfer device (48) together with the drying cylinder (50) forms a transfer nip through which the fibrous web (FB) and the third covering (34) are guided when the device (10) is used as intended, the first pressing element (26) being a suction roll ( 26) with an evacuated circumferential section (36) over which the first covering (20) and the fibrous web (FB) transported on the first covering (20) are guided before reaching the press nip. The invention also relates to a method for producing a fibrous web (FB) using such a device (10).

Description

The present invention relates to a device for producing a fibrous web, in particular a tissue paper web, comprising a forming section for forming the fibrous web, the forming section comprising a gap former with a headbox, a first covering and a second covering; a press section for pressing the formed fibrous web, the press section comprising a first press element and a second press element which together form a press nip through which, when the device is used as intended, the first covering, a third covering and, in between, the fibrous web; and a drying section for further drying the pressed fibrous web, the drying section comprising a drying cylinder to which the fibrous web transported on the third clothing is transferred, a transfer device for this purpose together with the drying cylinder forming a transfer nip through which the fibrous web can be used when the device is used as intended and the third covering can be guided. The present invention also relates to a method for producing a fibrous web, in particular a tissue paper web, using such a device.

Such a device and such a method are for example from the document US 8,414,741 B2 known. However, this known device has some disadvantages. For example, it is necessary to exert a very high compressive force on the fibrous web locally between the two pressing elements of the press section in order to achieve the desired dry content of the fibrous web after it has passed through the press section. However, a high compressive force has a negative effect on the bulk, ie on the thickness of the fibrous web in relation to the amount of fibrous material used. Although this undesirable effect can be counteracted by using press elements that together form an extended press nip, this makes the press section significantly more complex and therefore more expensive, especially if a very sophisticated technology, for example with variable pressure zones, is available for provision the extended press gap must be used. Alternatively or additionally, the device can have means upstream of the press section in order to predewater the fibrous web, but these also make the device complex in terms of construction and thus expensive.

It is therefore the object of the present invention to develop the device known from the prior art and the corresponding method described at the outset in such a way that the disadvantages mentioned are at least reduced. In particular, a device is to be provided which ensures a high or desired dry content after the fibrous web has passed through the press section without great structural additional expenditure, while at the same time the bulk of the fibrous web should be as large as possible.

This object is achieved by a device and a method according to the independent claims. The dependent claims represent advantageous developments of the invention.

According to claim 1, the generic device described at the outset is developed in such a way that the first press element is a suction roll with a suctioned circumferential section over which the first covering and the fibrous web transported on the first covering are guided before reaching the press nip. By designing the first press element as a suction roll, the fibrous web is pre-dewatered by the suction system before it passes through the press nip, so that it enters the press nip with a higher dry content compared to a variant in which the fibrous web has not previously been suctioned. This makes it possible to exert a lower pressing force on the fibrous web in the press nip of the press section in order to achieve the desired dry content at the end of the press nip. In this way, a relatively large bulk of the fibrous web can be achieved with the simultaneous use of relatively inexpensive technology for the two pressing elements of the press section.

It is true that in the publication mentioned at the beginning US 8,414,741 B2 also proposed that the fibrous web be pre-dewatered by means of a suction roll before it passes through the press nip, but this suction roll is designed separately and not as one of the two pressing elements, which leads to additional costs for the device.

The dry content of the fibrous web can be increased even further in a technically relatively simple manner before passing through the press nip of the press section if the device is designed to be operated in a first operating mode in which the third clothing is also guided over the evacuated circumferential section of the suction roll is, in such a way that the first covering radially inside, the third covering radially outside and in between the fibrous web are guided over the suctioned circumferential section of the suction roll, the third covering preferably with a tension of at least 10kN / m over the suctioned circumferential section of the suction roll to be led. In this way, the fibrous web is different than in the publication mentioned at the beginning US 8,414,741 B2 described, not only dewatered by the negative pressure of the suction roll acting on the fibrous web, but also by the belt tension of the third covering. The fibrous web is already pressed between the first covering and the third covering before it reaches the press nip of the press section, with the squeezed out water being sucked off by the suction roll. The first covering, the third covering and the fibrous web arranged in between are preferably guided over a circumferential section of the suction roll with suction, which is at least 45 °, more preferably between 60 ° and 100 °.

In a further development of the invention, it is also proposed that the device is designed to be operated in a second operating mode in which the third covering is not or only slightly guided over the suctioned circumferential section of the suction roll. “Slightly” in this context means that the third covering is guided over a circumferential section of the suction roll that is suctioned and which is smaller than 30 °, preferably smaller than 15 °. Advantages of being able to switch the device back and forth between the first operating mode and the second operating mode arise in particular when different characteristics are used for the first operating mode and the second operating mode as the third covering, as will be explained in more detail below. Switching between the two operating modes can be achieved, for example, in that a guide roller arranged in the wire loop of the third clothing, preferably the guide roll immediately upstream of the press nip of the press section, is arranged in the wire loop so that it can be displaced, in particular pivoted.

With regard to the first covering, it is proposed that it be a felt. “Felt” can be understood to mean a covering which has at least one layer of staple fibers. The staple fibers behave like a sponge in the press section, which is first squeezed out in the press nip and then relaxes again immediately after the press nip, with water being withdrawn from the fibrous web by capillary forces during the relaxation and being absorbed in the felt.

In contrast to this, it is preferred if the third covering, which is guided through the press nip of the press section together with the first covering and the fibrous web arranged in between, can absorb as little water as possible. In particular, it is proposed in a further development of the invention that the third covering consists essentially of an extruded plastic film, which can have one or more layers. For example, the third covering can consist of four individually extruded, stretched and then laminated plastic layers, each individual layer being, for example, 250 μm thick. The third covering can consist of the plastic film over the entire width and only have a single seam, in particular a transverse seam, in order to make the covering endless. Alternatively, the third covering can also consist of several parts of the plastic film, the parts being connected to one another at corresponding seams, or the third covering can be formed by a helically wound film strip, the finished covering then generally only having a single seam, in particular Has longitudinal seam.

In a further development of the invention, it is proposed that the third covering, in a first form, have a top side facing the fibrous web, an underside facing away from the fibrous web and, for contouring the fibrous web, a multiplicity of through openings which extend from the top to the bottom. The through openings can be made in the third covering in any known manner. In particular if the third covering consists essentially of an extruded plastic film, as described above, the through-openings can be made, for example, by laser drilling or etching. However, since the through-bores should have the property, with regard to their dimensions, of contouring the fibrous web when used as intended in the device according to the invention, it is preferred if the through-openings are made in the third covering by punching. Tests have shown that very satisfactory results can be achieved if the open area on the top and / or bottom (in the case of through openings in the form of straight circular cylinders, the open area of the top corresponds to the open area of the underside) is less than 20%, preferably between 5% and 15%. Other tests with covers that have a larger open area, for example an open area of 40%, turned out to be significantly worse.

It has also proven to be beneficial if some or all of the through openings have a clear opening of an area that corresponds to a circle with a diameter between 1 mm and 5 mm, some or all of the through openings preferably being essentially the shape of a cylinder, more preferably the Have the shape of a straight circular cylinder. However, the shape of the openings does not necessarily have to be that of a straight circular cylinder. The size of the area of the passage opening is of primary importance in order to achieve good contouring of the fibrous web. The area of a circle between 1 mm and 5 mm can easily be calculated using ^{the formula A = π * D 2/4.}

In this context, the person skilled in the art understands the term “contouring” to mean that the finished fibrous web has a pattern or embossing that can be clearly recognized with the naked eye even from a distance. The third covering differs noticeably from the corresponding covering in the publication mentioned at the beginning due to the passage openings proposed here, which outlines the fibrous web when the device according to the invention is used as intended US 8,414,741 B2 , in which this covering is smooth and preferably impermeable.

In a first variant, the closed surface on the top and / or bottom of the third covering can be designed to be essentially smooth. The term “closed area” here means the area of the third covering that remains between the passage openings. Alternatively, however, according to a second variant, it is possible for the closed surface to be structured on the upper side of the third covering. It is thus possible not only to contour the fibrous web through the through openings, but also to structure it, at least to a certain extent, in the area in between. The structuring of the closed surface can be achieved, for example, by etching shapes.

As an alternative to the previously described covering according to the first embodiment, ie with through openings, it is also possible that the third covering in a second embodiment has an upper side facing the fibrous web and an underside facing away from the fibrous web, the upper side being essentially smooth, so as not to contour the fibrous web. In particular, if the third covering according to the first expression and the third covering according to the second expression are optionally used in the device according to the invention, very different fibrous webs, in particular tissue products, can be produced on the same device, namely in particular contoured and non-contoured fibrous webs. Contoured fibrous webs usually have more bulk, which has a beneficial effect on their absorption capacity and perceived softness. This is particularly important for hygiene products that are intended for use on the skin. These are often so-called premium products. Non-contoured fibrous webs generally do not have this high quality. In return, however, they can be produced with less energy expenditure and thus more cost-effectively. A machine that can produce both types of fibrous webs without major retooling efforts can serve a significantly larger market.

In the press section, the second press element can advantageously have a surface that faces the press nip and is smooth. In this context, “smooth” means in particular that this surface does not have any grooves, bores or the like. Due to the smooth surface, the fibrous web follows the third covering more easily and is no longer guided with the first covering after the press nip. This is particularly true when the third covering is used according to the first form, because then a negative pressure acting through the through bores of the third covering can develop on the fibrous web, at least as long as the second pressing element is in contact with the third covering.

It is also advantageous if the second press element is designed to form an extended press nip together with the first press element. For example, the first and the second press element can jointly form a shoe press unit, the second press element comprising the so-called press shoe and a press cover rotating over it, while the first press element is designed according to the invention as a suction roll. The press shoe can have a concave shape which is adapted to the shape of the roller opposite it. By lengthening the press nip, it is possible to achieve good dewatering performance even with relatively low press forces, which has a positive effect on the bulk of the fibrous web.

At this point it should be noted that the suctioned circumferential section of the suction roll either ends in front of the extended press nip or, what is more preferred, in the extended press nip, but in any case does not go beyond the end of the press nip, so that the fibrous web after leaving the press nip is continued with the third covering and does not stick to the first covering, which is to separate from the fibrous web after the press nip.

Similar to the second press element of the press section, the transfer device can also have a surface facing the transfer nip, which is preferably designed to provide an extended transfer nip. Here, however, it is advantageous if this surface is uneven, preferably grooved, in order not to exert a suction effect on the fibrous web in the transfer nip through the passage openings of the third covering, so that the fibrous web simply follows the surface of the drying cylinder after the transfer nip.

About the dry content of the fibrous web even before it reaches the press nip To increase this further, means can also be provided for heating the fibrous web before it reaches the press nip, the means preferably acting on the fibrous web in the circumferential section of the suction roll that is evacuated. The means for heating the fibrous web can be, for example, a device that applies steam to the fibrous web. The steam can come from a reboiler which is connected to the drying cylinder and / or a steam hood arranged above the drying cylinder. Alternatively, however, a conventional steam hood or hot air can also be used as a means for heating the fibrous web.

Another aspect of the present invention relates to a method for producing a fibrous web, in particular a tissue paper web, using a device described above.

It is advantageous if the device is operated in the first operating mode described above with the third clothing also described above in the first form, and in the second operating mode described above with the third clothing also described above in the second form, the Device can be switched back and forth between the first operating mode and the second operating mode or is. In this way, the device can produce different qualities of fibrous webs, namely, in particular, a contoured fibrous web and a non-contoured fibrous web, without major retooling. Since the third covering in the second form has no through openings and is therefore essentially impermeable, it is advantageous not to guide the third covering, or only slightly over the suctioned peripheral section of the suction roll, in accordance with the second operating mode, so that the fibrous web during suctioning air can flow through it through the suction roll. When using the third covering according to the first expression, on the other hand, the air can flow through the passage openings of the covering. The first covering, which is preferably designed as a felt, is basically permeable in order to allow the suction effect of the suction roll to act on the fibrous web.

It should be noted at this point that the first covering, which is preferably designed as a felt, can optionally have a smooth surface facing the fibrous web, i.e. a surface that does not contour the fibrous web, or a surface that is suitable for contouring the fibrous web. In the latter case, one could also speak of a molding fabric. Since, in a molding fabric, contours are introduced into the fibrous web during the forming process, they are anchored in the finished fibrous web in a very stable manner. In this context, it is also said that the fibrous web has an intrinsic memory effect. The use of a molding fabric as the first covering should be possible regardless of whether the third covering is used according to the first or second version.

• 1 eine beispielhafte Ausführungsform der erfindungsgemäßen Vorrichtung in einem ersten Betriebsmodus;
• 2 eine beispielhafte Ausführungsform der erfindungsgemäßen Vorrichtung in einem zweiten Betriebsmodus; und
• 3 eine beispielhafte Ausführungsform der dritten Bespannung in einer ersten Ausprägung mit Durchgangsöffnungen zum Konturieren der Faserstoffbahn.

The invention is explained in more detail below with the aid of exemplary embodiments and schematic figures. Show it:

• 1 an exemplary embodiment of the device according to the invention in a first operating mode;
• 2 an exemplary embodiment of the device according to the invention in a second operating mode; and
• 3 an exemplary embodiment of the third covering in a first form with through openings for contouring the fibrous web.

1 shows an exemplary embodiment of the device according to the invention 10 in a first operating mode. The device 10 includes a forming section 12th for forming a fibrous web FB , one to the forming section 12th subsequent press section 14th for pressing the formed fibrous web FB and one to the press section 14th subsequent dryer section 16 for further drying of the pressed fibrous web FB . The fibrous web FB is in 1 shown as a dashed line.

To form the fibrous web FB First, a fiber suspension, which consists mainly of water and only has a small proportion of fibers, is passed through a headbox 18th in a gap between a first covering 20th and a second covering 22nd a so-called gap former. In this embodiment, the first covering 20th be a felt, i.e. a covering which has at least one layer of staple fibers, whereas the second covering 22nd can be a woven forming fabric. The first covering 20th , the second covering 22nd and the fibrous web disposed therebetween FB are together with a certain tension over a forming roll 24 out, which is preferably vacuumed in order to at least partially suck off the water pressed from the pulp suspension. After leaving the gap in the forming section 12th the formed fibrous web follows FB the first covering 20th to the press section 14th .

The press section 14th comprises a first pressing element 26th , which according to the invention as a Suction roll is formed, and a second pressing element 28 , which, as in this embodiment, is preferably designed as a shoe press and thus a stationary shoe 30th and one around the shoe 30th rotating press jacket 32 having. The shoe 30th has a concave curved surface which is the convex surface of the first pressing member 26th or the suction roll 26th facing and adapted to this. The first pressing element 26th and the second pressing member 28 together form an extended press nip through which the first covering 20th , a third covering 34 and the fibrous web disposed therebetween FB be run together.

The suction roll 26th comprises an evacuated peripheral portion 36 , which is only indicated schematically here. In this embodiment, the evacuated peripheral portion 36 for example over about 90 ° of the circumference of the suction roll 26th extend. It ends either in front of or, as here, preferably within the extended press nip, that of the first press element 26th and the second pressing member 28 is trained. The first covering 20th , the third covering 34 and the fibrous web disposed therebetween FB are in 1 illustrated first operating mode of the device according to the invention together over at least a large part, ie over at least 45 °, preferably over at least 60 °, of the evacuated circumferential section 36 guided. By the tension of the third covering 34 , which should be at least 10kN, experiences the fibrous web FB in addition to the suction through the suction roll 26th before reaching the press nip of the press section 14th an efficient pre-drainage. Thus, the dry content of the fibrous web is FB in comparison to the embodiment in the document mentioned at the beginning US 8,414,741 B2 is described, already relatively high before reaching the press nip. On the one hand, this has the consequence that the actual press, in particular the shoe press, can be designed to be simpler and therefore more cost-effective. On the other hand, the higher dry content of the fibrous web has an effect FB in front of the press nip also has a positive effect on the contouring of the fibrous web FB out. Because of the higher dry content, the material of the fibrous web has FB In particular in the more densely compressed areas in the press nip, a higher resistance force and thus a larger bulk at the end.

After leaving the press nip of the press section 14th the first covering separate 20th and the third covering 34 from each other, the fibrous web FB continue on the third covering 34 to be led. In order to reliably achieve this separation, it is advantageous if the evacuated peripheral section 36 the suction roll 26th ends before the end of the extended press nip. It is also advantageous if the around the shoe 30th rotating press jacket 32 one of the third covering 34 and the fibrous web FB Has facing surface which is essentially smooth, in particular free of grooves or the like, is formed. This allows through the third covering 34 therethrough, at least if the same is made permeable, a negative pressure on the fibrous web FB act, which the fibrous web FB on the third covering 34 holds.

In the in 1 illustrated first mode of operation of the device according to the invention 10 is the third covering 34 made permeable. Preferably the third covering is 34 an extruded plastic film, which can have one or more layers. For example, the third covering 34 consist of four individual plastic layers that have been separately extruded, stretched and then laminated together. Thinner layers can be stretched more than thicker ones, so that laminates formed accordingly can have high tensile strengths. The main stretching direction of the individual layers preferably points in the machine direction or MD direction of the finished third clothing 34 .

As in 3 can be seen, has the third covering in the present embodiment 34 according to a first expression, a plurality of relatively large through openings 40 on which one of the fibrous web FB facing top 42 with one of the fibrous web FB Connect facing away bottom. The through openings 40 can have the shape of a right circular cylinder, the cylinder axis being orthogonal to the top 42 or to the underside of the third covering 34 is oriented. The through openings are preferably 40 by punching into the third covering 34 brought in. The through openings 40 are dimensioned in such a way that they are able to use the fibrous web FB in the device according to the invention 10 to contour. Good results could be achieved with diameters between 1mm and 5mm, for example with 1.3mm or 3.0mm.

Tests have also shown that the third covering has a large open area 34 , such as an open area of about 40%, gives far less satisfactory results compared to a smaller open area, especially an open area of no more than 20%. Good results have been achieved with an open area of the order of 8% -11%. This means that the through openings 40 preferably only 8% -11% of the top 42 or the underside of the third covering 34 turn off. The good test results are mainly explained by the fact that the remaining 89% -92%, which as a closed area through the remaining film material are defined, a good contact of the fibrous web FB to a drying cylinder described in more detail later 50 allow. On the one hand, this good contact enables the fibrous web to adhere easily FB to the drying cylinder 50 without this too great pressure forces in a transfer device also described in more detail below 48 to have to apply, and on the other hand a good heat transfer from the drying cylinder 50 into the fibrous web FB . As a result of the lower contact pressure in the transfer device 48 can the drying cylinder 50 be made thinner-walled, which on the one hand reduces the manufacturing costs and on the other hand improves the heat transfer even further.

On the fibrous web FB facing top 42 the closed surface can optionally be designed to be essentially smooth or slightly structured in order to create finer structures in the fibrous web FB memorize. Such structuring 44 can for example by etching in the top 42 to be engraved.

The contouring and possibly finer structuring of the fibrous web FB through the third covering 34 according to the first embodiment, in the in 1 illustrated first mode of operation of the device according to the invention 10 not only in the press nip between the first press element 26th and the second pressing member 28 , but to a lesser extent beforehand in the section of the evacuated circumferential section 36 the suction roll 26th over which the first covering 20th , the third covering 34 and the fibrous web disposed therebetween FB in between are conducted together about it.

After leaving the press nip, the fibrous web follows FB the third covering 34 and is carried out with this via a deflection roller 46 which can be vacuumed to ensure a secure hold of the fibrous web FB on the third covering 34 to ensure when deflecting, to the dryer section 16 guided. The dryer section 16 includes the aforementioned transfer device 48 , by means of which the fibrous web FB from the third covering 34 to the drying cylinder also mentioned above 50 is passed. From the drying cylinder 50 is in 1 only one section shown. It can be designed as a so-called Yankee cylinder and have a steam hood or Yankee hood, not shown here. After further drying of the fibrous web FB on the surface of the drying cylinder 50 can the fibrous web FB by means of a creping doctor from the surface of the drying cylinder 50 and then either further processed or refined or wound up directly.

The transfer device 48 preferably comprises just like the second pressing element 28 the press section 14th a fixed shoe 52 , which one to the drying cylinder 50 has facing and adapted to this concave surface, and one around the shoe 52 rotating press jacket 54 . In contrast to the rotating press jacket 32 of the second pressing element 28 shows the press jacket 54 the transfer device 48 does not have a substantially smooth surface, but preferably comprises a multiplicity of grooves or the like, in particular circumferential grooves, in order to pass over the through openings 40 the third covering 34 the fibrous web FB in a transfer gap between the transfer device 48 and drying cylinders 50 to ventilate, so that there is no suction between the third covering 34 and the fibrous web FB can arise and the fibrous web FB the smooth surface of the drying cylinder 50 after leaving the transfer gap reliably continues. This enables the reliable transfer of the fibrous web FB from the third covering 34 onto the surface of the drying cylinder 50 can be achieved without particularly large pressing forces on the fibrous web FB by means of the transfer device 48 having to exercise. As a result, not only can the transfer device be made technically simpler and thus more cost-effective, but the outer wall of the drying cylinder can also be 50 be made thinner, as this only has to withstand lower compressive forces. A thinner version of the wall of the drying cylinder 50 However, in addition to material and thus cost savings, it also means better heat transfer from the interior of the drying cylinder 50 through its wall into the fibrous web 50 . Thus, the device according to the invention 10 can be operated in a very energy-efficient and thus cost-efficient manner.

In comparison to this, such an energy-efficient operation is in the case of a device as described in the publication mentioned at the beginning US 8,414,741 B2 is not possible, since here the third covering should be made smooth and preferably impermeable. Because of the lack of the possibility of rear ventilation of the fibrous web in the transfer nip, the transfer of the fibrous web from the third clothing to the surface of the drying cylinder is extremely difficult in practice with this known device. This not only means that higher pressure forces and thus a more stable design of the drying cylinder are necessary in the transfer nip, but also larger quantities of chemicals have to be used with which the third covering is sprayed to make it easier to detach the fibrous web from it. In addition, there is the need to thoroughly clean the third clothing before it is passed through the press nip of the press section. The distance or the length of the Third covering between the press nip of the dryer section and the transfer nip of the transfer device should be made relatively long so that the fibrous web has enough time to soak up the moisture film that forms after the press nip between the fibrous web and the smooth and impermeable third covering, so that it can pass through its suction effect does not prevent the fibrous web from detaching from the third covering. However, a large length of the third covering between the press nip and the transfer nip leads to higher costs. In addition, re-moistening of the fibrous web after the press nip is energetically counterproductive, since this water that has been absorbed again has to be removed from the fibrous web again by more power in the dryer section. All of these disadvantages from the prior art can be eliminated with the device according to the invention, at least with the one in 1 shown device in the first operating mode, avoided or at least reduced.

To use one and the same device 10 fiber webs without major retooling efforts FB to be able to produce different quality, in particular a contoured fibrous web FB and a non-contoured fibrous web FB , the device can 10 preferably also be operated in a second operating mode. The device 10 in the second operating mode is in 2 shown schematically. In the following, only the differences between the second operating mode and the first operating mode will be discussed, so that otherwise the above explanations regarding the first operating mode, taking into account the 1 is referred. A guide roller is in the second operating mode 56 , which are in the wire loop of the third covering 34 arranged and immediately in front of the press nip of the press section 14th is stored, positioned differently than in the first operating mode, namely so that the third covering 34 not or only slightly over the evacuated circumferential section 36 the suction roll 26th to be led. The guide roller is used for this purpose 56 preferably pivotable in the device 10 stored in accordance with in a simple manner between the position in the first operating mode 1 and the position in the second operating mode according to 2 to be adjusted. The positioning of the deflection roller in the second operating mode allows the fibrous web FB even then efficiently along the evacuated peripheral portion 36 the suction roll 26th to drain when the third covering 34 is not or only slightly permeable. By the third covering 34 the fibrous web FB namely in the evacuated circumferential section 36 the suction roll 26th not or only slightly covers, air can freely pass through the fibrous web and the first covering from the suction roll 26th be sucked.

Another difference to the in 1 The first operating mode shown in FIG 2 illustrated second operating mode, preferably a third covering 34 used according to a second expression, which is characterized in that its the fibrous web FB facing top 42 is designed essentially smooth, so that it is the fibrous web FB not contoured. In particular, the third covering 34 according to the second expression, not the relatively large through openings 40 like the third covering 34 according to the first expression. At most, much smaller connections from the top 42 and the underside of the third covering according to the second expression are possible in order to give the third covering a certain, but significantly lower, permeability. However, because of their small size, these connections are not suitable for the fibrous web FB to contour. This allows the fibrous web FB over the entire area in the press nip of the press section 14th are pressed, which on the one hand makes the production of the fibrous web more energy-efficient on the one hand, but on the other hand results in a lower bulk and thus a lower absorption capacity and perceived softness of the finished fibrous web FB , in particular tissue web, leads.

Finally, it should be noted that there are optional funds 58 for heating the fibrous web FB can be provided which are suitable, the fibrous web FB before reaching the press nip in the press section 14th to heat. The means 58 are preferably arranged so that they are on the fibrous web FB in the area of the evacuated peripheral section 36 the suction roll 26th Act. The means 58 can, for example, apply steam to the fibrous web. The steam can come from a reboiler from the drying cylinder 50 and / or a steam hood arranged above it. The steam can move the fibrous web FB also through the third covering 34 Reach through, provided that they have the relatively large through openings 40 having. By heating the fibrous web FB before passing through the press nip of the press section 14th can be the dry content of the fibrous web FB increased even further and the contouring of the fibrous web FB can be carried out even more easily in the press nip.

List of reference symbols

10

contraption

12th

Forming section

14th

Press section

16

Dryer section

18th

Headbox

20th

first covering (forming fabric)

22nd

second covering (felt)

24

Forming roll

26th

first press element (suction roll)

28

second press element (shoe press)

30th

Shoe (fixed)

32

Press jacket (rotating)

34

third covering (plastic film)

36

evacuated circumferential section (of the suction roll 26th )

38

Deflection roller

40

Through opening

42

Top (of the third covering 34 )

44

Structures (on the top 42 the covering 34 )

46

Deflection roller

48

Transfer device

50

Drying cylinder (Yankee cylinder)

52

Shoe (fixed)

54

Press jacket (rotating)

56

Deflection roller

58

Means (for heating the fibrous web FB )

FB

Fibrous web

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 8414741 B2 [0002, 0006, 0007, 0013, 0028, 0037]

Claims (15)

Device (10) for producing a fibrous web (FB), in particular a tissue paper web, comprising: - a forming section (12) for forming the fibrous web (FB), the forming section (12) being a gap former with a headbox (18) and a first covering (20) and a second covering (22); - A press section (14) for pressing the formed fibrous web (FB), the press section (14) comprising a first pressing element (26) and a second pressing element (28) which together form a press nip through which, when the device is used as intended ( 10) the first covering (20), a third covering (34) and the fibrous web (FB) between them are guided; and - a drying section (16) for further drying the pressed fibrous web (FB), the drying section (16) comprising a drying cylinder (50) to which the fibrous web (FB) transported on the third clothing (34) is transferred, for this purpose a transfer device (48) together with the drying cylinder (50) forms a transfer nip through which the fibrous web (FB) and the third covering (34) are guided when the device (10) is used as intended, characterized in that the first pressing element (26 ) is a suction roll (26) with a circumferential section (36) with suction, over which the first covering (20) and the fibrous web (FB) transported on the first covering (20) are guided before reaching the press nip. Device (10) according to Claim 1 , characterized in that the device (10) is designed to be operated in a first operating mode, in which the third covering (34) is also guided over the evacuated peripheral section (36) of the suction roll (26) in such a way that radially inside the first covering (20), radially outside the third covering (34) and in between the fibrous web (FB) over the evacuated peripheral section (36) of the suction roll (26), the third covering (34) preferably with a tension of at least 10kN / m over the evacuated peripheral section (36) of the suction roll (26). Device (10) according to Claim 1 or 2 , characterized in that the device (10) is designed to be operated in a second operating mode in which the third covering (34) is not or only slightly guided over the evacuated peripheral section (36) of the suction roll (26). Device (10) according to one of the preceding claims, characterized in that the first covering (20) is a felt. Device (10) according to one of the preceding claims, characterized in that the third covering (34) consists essentially of an extruded plastic film which has one or more layers. Device (10) according to one of the preceding claims, characterized in that the third covering (34) in a first form has an upper side (42) facing the fibrous web (FB), an underside facing away from the fibrous web (FB) and for contouring the fibrous web ( FB) has a plurality of through openings (40) which extend from the top (42) to the bottom, the open area on the top (42) and / or the bottom of the third covering (34) being less than 20% , preferably between 5% and 15%. Device (10) according to Claim 6 , characterized in that some or all of the through openings (40) have a clear opening of an area which corresponds to a circle with a diameter between 1mm and 5mm, some or all of the through openings (40) preferably essentially in the form of a cylinder, more preferably have the shape of a right circular cylinder. Device (10) according to Claim 6 or 7th , characterized in that the closed surface on the top (42) and / or bottom of the third covering (34) is essentially smooth. Device (10) according to Claim 6 or 7th , characterized in that the closed surface is structured on the upper side (42) of the third covering (34). Device (10) according to one of the Claims 1 to 5 , characterized in that the third covering (34) in a second expression has a top side (42) facing the fibrous web (FB) and an underside facing away from the fibrous web (FB), the top side (42) being essentially smooth, around the Fibrous web (FB) not to be contoured. Device (10) according to one of the preceding claims, characterized in that the second press element (28) has a smooth surface facing the press nip, and is preferably designed to provide an extended press nip. Device (10) according to one of the preceding claims, characterized in that the transfer device (48) has an uneven, preferably grooved, surface facing the transfer gap, and is preferably designed to provide an elongated transfer gap. Device (10) according to one of the preceding claims, characterized in that means for heating (58) the fibrous web (FB) are provided before reaching the press nip, the means (58) preferably in the evacuated peripheral section (36) of the suction roll (26) ) act on the fibrous web (FB). Method for producing a fibrous web (FB), in particular a tissue paper web, using a device (10) according to one of the preceding claims. Procedure according to Claim 14 , characterized in that the device (10) in the first operating mode according to Claim 2 with the third covering (34) in the first expression according to one of the Claims 6 - 9 is operated, and in the second operating mode according to Claim 3 with the third covering (34) according to the second expression Claim 10 is operated, wherein the device (10) can or will be switched back and forth between the first operating mode and the second operating mode.

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