EP3623525A1 - Method and machine for manufacturing a sheet of fibrous material - Google Patents

Abstract

The invention relates to a machine (1) for producing a fibrous web (2), having a forming area, comprising a forming roller (5) and a permeable inner band (4) that at least partially wraps it together with an outer band (3) to form the fibrous web (2), with a pressing device (7) directly following the forming area, for further dewatering of the fibrous web (2) in a press nip, and with a subsequent drying cylinder (14), the fibrous web (2) from the forming area to the transfer to the heated one Surface of the drying cylinder (14) is guided lying on the inner belt (4). The machine (1) according to the invention is characterized in that the inner belt (4) for structuring the fibrous web (2) is structured and the transfer roller (13) is designed to form an extended transfer nipple (12) as a shoe roller.

Description

The invention relates to a machine for producing a fibrous web, in particular a tissue web, with a forming area, comprising a forming roll and a permeable inner belt, which at least partially wraps around this together with an outer band, for forming the fibrous web, with a pressing device directly following the forming area, comprising a a press nip formed by a press roll and a counter roll for further dewatering of the fibrous web, the press nip being the first press nip of the pressing device, the fibrous web being guided through the press nip lying between the inner band and a lower press band, and with a drying cylinder following the press device, wherein the fibrous web is guided from the forming area to the transfer, in a transfer nip formed between a transfer roller and the drying cylinder, from the inner belt to the heated surface of the drying cylinder on the inner belt .

The invention also relates to a method for producing a fibrous web, in particular a tissue web.

Machines of this type are known. The document EP2796617 B1 discloses a crescent former paper machine for making tissue paper. The tissue web is formed in a forming area between an outer sieve and a felt and, in a first configuration, lies on the felt together with another felt through a shoe press and then transferred in a roller nip to the surface of the subsequent drying cylinder. With this configuration, heavy tissue papers with high specific volumes are to be produced in an energy-efficient manner. In a proposed second configuration, the tissue web is not passed through the shoe press nip, but is passed directly from the forming area to the surface of the subsequent drying cylinder. In addition, the arrangement of a suction felt guide roller for conditioning the felt in front of the shoe press is proposed. The disadvantage of this arrangement is one limited increase in quality, especially the specific volume of the tissue web.

In the document US 6,547,924 B2 a similar crescent former paper machine is disclosed. However, instead of the felt in the former, an impermeable structured belt is provided, on which the tissue web is guided to the drying cylinder through a simply felted shoe press. The disadvantage is inadequate drainage in the shoe press. Only a low dry matter content of the tissue web in front of the drying cylinder can be achieved. The result is a high expenditure of energy due to the thermal drying of the web in the area of the drying cylinder. It also limits production speed and production.

The object of the invention is therefore to propose a machine and a method for improving the quality of the tissue web produced, in particular the specific volume, with good runability at high production speed, with efficient use of energy, and simple construction.

The object is achieved by features of claims 1 and 14. A machine for producing a fibrous web, in particular a tissue web, is proposed, comprising a forming area, comprising a forming roll and a permeable inner band, which at least partially wraps around this together with an outer band, for forming the fibrous web, with a pressing device directly following the forming area a press nip formed by a press roll and a counter roll for further dewatering of the fibrous web, the press nip being the first press nip of the press device, the fibrous web being guided through the press nip lying between the inner band and a lower press band, and with a drying cylinder following the press device , wherein the fibrous web from the forming area to the transfer, formed in a between a transfer roller and the drying cylinder Transfer nip, from the inner belt to the heated surface of the drying cylinder lying on the inner belt. It is essential to the invention that the inner band for structuring the fibrous web is structured and the transfer roller is designed as a shoe roller to form an extended transfer nip.

This machine is characterized by a simple structure with which a fibrous web, in particular a tissue web with a high specific volume and at the same time a high achievable dry content in the pressing device can be reliably produced at high speed. The formation of the fibrous web on the structured inner band gives it a structure which leads to a high specific volume. This essentially remains even after the press nipple has passed through, since the structure of the inner band protects the structure of the fibrous web during the pressing process. The compressibility of the inner band is preferably less than that of the lower press band.

The inner band is permeable, that means permeable to air and water. This enables two-sided dewatering of the fibrous web in the press nip, the squeezed water being partially, that is to a small extent, taken up by the inner band and the lower press band. The lower press belt, which is in contact with the fibrous web, can be optimized with regard to the quality, for example the specific volume, the fibrous web produced and a coordinated water absorption. This enables gentle drainage without damaging and crushing the fibrous web. As a result, higher line forces can be driven in the press nip. The web guide without transfer between two fabrics enables reliable and stable operation of the machine, even with high production and speed. The formation of the transfer roller as a shoe roller has an advantageous effect on the transfer of the fibrous web from the inner belt to the heated surface of the drying cylinder. Because of the fibrous web embossed structure of the inner band, the web is only pressed selectively in the transfer nip, which is only driven with a low line load or a low pressure. Therefore, the increased dwell time of the fibrous web in the press nip has a positive effect on the transfer to the drying cylinder.

Another advantage of the solution is the compact design with regard to the small space requirement with regard to the overall height of the machine. The length of the lower press belt can be made short. The felt guide of the lower press belt can therefore only extend above the machine floor. This eliminates the need for a basement. This means that this machine can also be installed in existing machine halls without a basement for the production of high-quality tissue webs with a high specific volume, for example kitchen towels.

The inner, structured band can be woven. It can also be designed as a permeable membrane or film structured at least on the fibrous web side.

The drying cylinder can be designed as a Yankee drying cylinder, in particular in the production of tissue fibrous webs. The construction of Yankee drying cylinders is known. For example, they have a large diameter of over 6 m and are steam-heated.

This machine can be easily and inexpensively converted for the production of certain types of tissue with lower demands on the specific volume and higher demands on the production output. For this, the inner, structured belt can be replaced by a conventional press felt and the press device deactivated. This means that the press device either bypasses the guide of this press felt or this press felt is guided through the opened press nip. This arrangement thus corresponds to a known crescent former machine.

In an advantageous embodiment, the lower press belt is designed as a water-absorbing press belt, in particular as a press felt.

The press roller can be arranged within the loop formed by the inner belt and the counter roll within the loop formed by the lower press belt. It is also possible to arrange the press roll within the loop formed by the lower press belt and the counter roll within the loop formed by the inner belt.

Furthermore, the press nip can be designed as a separate press nip, that is to say as an individually standing press nip. This results in a simple construction of the machine.

The press roll can be designed as a shoe roll to form an extended press nip. As a result, higher line forces can be driven in the press nip. The extended press nip of this shoe press at the beginning of the press device, i.e. directly after the forming area, enables gentle dewatering without damaging and crushing the fibrous web. At the same time, a higher dry content of the fibrous web can be achieved than is the case with a belt press, for example.

In certain cases it is also possible to run the press roll full jacket roll.

The counter roll can be designed as a suction roll. This allows the drainage, in particular the direction of drainage, to be influenced.

In order to increase the temperature and to improve the dewatering ability of the fibrous web, a steam blower box can be assigned to the fibrous web before the press nip to apply steam to the fibrous web.

In one possible practical embodiment, a suction device is arranged upstream of the press nip, viewed in the machine running direction, within the loop formed by the inner band. As a result, the structure of the fibrous web produced by the inner, structured band can be stabilized and maintained. Vacuum is applied to the suction device.

A blower hood can be assigned to the suction device for direct application of steam and / or hot dry air and / or hot moist air to the fibrous web.

In one possible development, a suction deflecting roller which is partially wrapped around the inner belt is arranged within the loop formed by the inner belt and between the press nip and the transfer roller. The suction deflection roller can be subjected to negative pressure. The web guide can thereby be stabilized and the dry content for certain types of fibrous web in front of the drying cylinder can be increased. This arrangement is particularly advantageous when the transfer roller, in accordance with the invention, is designed as a shoe press roller. As a result, the fiber web is reliably transferred to the drying cylinder even when the dry content is high.

Furthermore, the suction deflecting roller can be partially wrapped by a permeable press belt in direct contact with the fibrous web. The press belt can have an increased belt tension of, for example, more than 20 kN / m, preferably more than 30 kN / m. As a result, the dry content of the fibrous web can be increased even further for certain types of fibrous web before it is transferred to the drying cylinder.

In a further possible embodiment, a hood can be provided within the loop formed by the press belt and in the area of the wrap for indirectly applying steam and / or hot dry air and / or hot moist air to the fibrous web his. As a result, the dry content of the fibrous web can be increased further for certain types of fibrous web before it is transferred to the drying cylinder.

The object is also achieved by a method for producing a fibrous web, in particular a tissue web, according to claim 13. The lower press belt is preferably designed as a water-absorbing press belt, in particular as a press felt.

Further features, configurations and advantages of the method result from the above description of the machine according to the invention and from the following description of preferred exemplary embodiments with reference to the drawings.

Figur 1

eine erste Ausführungsform einer erfindungsgemäßen Maschine in vereinfachter, schematischer Darstellung;

Figur 2

eine zweite Ausführungsform einer erfindungsgemäßen Maschine in vereinfachter, schematischer Darstellung;

Figur 3

eine dritte Ausführungsform einer erfindungsgemäßen Maschine in vereinfachter, schematischer Darstellung;

Show it

Figure 1

a first embodiment of a machine according to the invention in a simplified, schematic representation;

Figure 2

a second embodiment of a machine according to the invention in a simplified, schematic representation;

Figure 3

a third embodiment of a machine according to the invention in a simplified, schematic representation;

Figure 1 shows a first embodiment of a machine 1 according to the invention in a simplified, schematic representation. The machine 1 for producing a fibrous web 2, in this example a tissue web 2, comprises a forming area with a forming roller 5 and an inner belt 4 which at least partially wraps around this together with an outer belt 3. A headbox 6 brings a belt between these belts 3, 4 Fiber suspension. This is mainly dewatered in the common looping area of the belts 3, 4 in the area of the forming roller 5 to form the tissue web 2, and on the inner band 4 lying to and guided by a directly following pressing device 7. In this example, the press device 7 comprises a press roll 8 arranged at the top and a counter roll 9 arranged below which, in cooperation, form a press nip 24 for further dewatering of the tissue web 2. The counter roll 9 and the press roll 8 can also be arranged upside down. The counter roller 9 is designed as a suction roller with an applied vacuum. This press nip 24 of the press device 7 is the first press nip 24 after the forming area. In front of the press nip 24, seen in the machine running direction 22, a suction device 21, in this case a suction box 21, which is acted upon by vacuum, is arranged upstream of the loop formed by the inner band 4. A suction hood 21 is assigned to a blow hood 20 for direct application of steam and / or hot dry air and / or hot humid air to the tissue web 2. Through the press nip 24, in addition to the tissue web 2 and the inner band 4, there is also a lower press band 11 which directly contacts the tissue web 2. The lower press belt 11 is designed as a water-absorbing press felt. After further dewatering of the tissue web 2 in the pressing device 7, the tissue web 2 is guided lying on the inner belt around a transfer roller 13, which is designed as a shoe roller. This forms together with a drying cylinder 14, which in this case is designed as a Yankee drying cylinder 14 , a transfer nip 12 in which the tissue web 2 is transferred from the inner belt 4 to the heated surface of the Yankee drying cylinder 14 and is further thermally dried. In addition, the tissue web 2 is exposed to hot air and / or superheated steam via a drying hood 15 arranged in the region of the Yankee drying cylinder 14. The tissue web 2 is then creped on a scraper 16 and removed from the surface of the Yankee drying cylinder and is led directly or indirectly to a roll-up station, not shown. The tissue web 2 is thus guided by a single belt 4 from the forming area to the Yankee drying cylinder 14. A transfer to an intermediate belt is not necessary to produce high-quality tissue webs with a high specific volume according to the invention. This promotes good machine runnability. The inner band 4 is permeable, that is called permeable to air and water, and it has a structure for structuring the tissue web 2 at least on the side touching the tissue web 2. This structuring of the tissue web 2 causes a high specific volume, which is also referred to as bulk. The inner, structured band 4 is a woven band in this example. It can also be designed as a permeable membrane or film structured at least on the tissue web side. The compressibility of the inner, structured belt is less than that of the lower press belt. As a result, the structure of the tissue web 2 is well protected and not crushed when it passes through the press nip 24. The machine 1 according to the invention enables two-sided dewatering of the tissue web 2 in the press nip 24, the squeezed water being partially absorbed by the inner belt 4 and mainly by the lower press belt 11. The lower press belt 11, which is in contact with the tissue web 2, is optimized with regard to the quality, for example the specific volume, the tissue web 2 produced and with regard to the dewatering capacity. The transfer roller 13 is designed as a shoe press roller to form an extended transfer nip 12 together with the Yankee drying cylinder 14.

The machine 1 is very compact in terms of overall height. The length of the lower press belt 11 is short. The felt guide of the lower press belt 11 is arranged exclusively above the machine base 23. This eliminates the requirement for the presence of a cellar, which is required in known machines for the production of tissue webs with a high bulk. This machine can therefore also be installed in existing machine halls without a basement for the production of high-quality tissue webs 2 with a high specific volume, for example kitchen towels.

Figure 2 shows a second embodiment of a machine 1 according to the invention in a simplified, schematic representation. It differs from the embodiment Figure 1 by an inside of the loop formed by the inner band 4 and between the press nip 24 and the transfer roller 13 and from the inner Volume 4 partially wrapped suction deflecting roller 17. The suction deflecting roller 17 can be subjected to negative pressure. As a result, the web guidance can be stabilized and the dry content for certain types of tissue web in front of the drying cylinder 14 can be increased. This arrangement has a particularly advantageous effect together with a transfer roller 13, which is designed according to the invention as a shoe press roller.

The Figure 3 shows a third embodiment of a machine 1 according to the invention in a simplified, schematic representation. It differs from the embodiment Figure 2 , characterized in that the suction deflecting roller 17 is partially wrapped in a permeable press belt 18 and is in direct contact with the tissue web 2. The press belt exerts pressure on the tissue web to increase the dry content. The press belt 18 has an increased belt tension of more than 20 kN / m, preferably more than 30 kN / m. As a result, the dry content of the tissue web 2 can be increased for certain types of tissue web before being transferred to the drying cylinder 14. A hood is provided within the loop formed by the press belt 18 and in the area of the wrap for indirectly applying steam and / or hot dry air and / or hot moist air to the fibrous web. As a result, the dry content of the fibrous web can be increased even further for certain types of tissue web before transfer to the drying cylinder.

Corresponding elements of the exemplary embodiments in the figures are provided with the same reference symbols. The functions of such elements in the individual figures correspond to one another, unless otherwise described and it does not lead to contradictions. A repeated description is therefore omitted. It is also pointed out that the different features of the exemplary embodiments shown can be interchanged and combined with one another. The invention is therefore not based on the Characteristic combinations shown of the exemplary embodiments shown are limited.

Reference list

1

machine

2nd

Fibrous web

3rd

Outer band

4th

Inner band

5

Forming roller

6

Headbox

7

Pressing device

8th

Press roll

9

Counter roll

11

Lower press belt

12th

Transfer nip

13

Transfer roller

14

Drying cylinder

15

Drying hood

16

scraper

17th

Suction deflection roller

18th

Press belt

19th

Hood

20th

Blow hood

21

Suction device

22

Machine direction

23

Machine floor

24th

Press nip

Claims (14)

Machine (1) for producing a fibrous web (2), in particular a tissue web, with a forming area, comprising a forming roller (5) and a permeable inner band (4) which at least partially wraps around this together with an outer band (3) to form the fibrous web (2), with a press device (7) directly following the forming area, comprising a press nip (24) formed by a press roll (8) and a counter roll (9) for further dewatering of the fibrous web (2), the press nip (24) of the is the first press nip (24) of the press device (7), the fibrous web (2) lying between the inner band (4) and a lower press band (11) lying through the press nip (24), and with one of the press device (7) subsequent drying cylinder (14), the fibrous web (2) from the forming area to the transfer, in a transfer nip (12) formed between a transfer roller (13) and the drying cylinder (14), from the inner belt (4) to the be heated surface of the drying cylinder (14) is guided lying on the inner belt (4),
characterized in that
the inner band (4) for structuring the fibrous web (2) is structured and the transfer roller (13) is designed as a shoe roller to form an extended transfer nip (12). Machine according to claim 1,
characterized in that
the lower press belt (11) is designed as a water-absorbing press belt, in particular as a press felt. Machine according to one of the preceding claims,
characterized in that
the press nipple (24) is designed as a separate press nipple. Machine according to one of the preceding claims,
characterized in that.
the press roll (8) is designed as a shoe roll to form an extended press nip (24). Machine according to one of the preceding claims,
characterized in that
the press roller (8) is arranged within the loop formed by the inner belt (4) and the counter-roller (9) within the loop formed by the lower press belt (11) or the press roller (8) within the loop formed by the lower press belt (11) formed loop and the counter roller (9) is arranged within the loop formed by the inner band (4) .. Machine according to one of the preceding claims,
characterized in that.
The counter roller (9) is designed as a suction roller. Machine according to one of the preceding claims,
characterized in that
the fibrous web (2) in front of the press nip (24) is assigned a steam blower box to apply steam to the fibrous web (2). Machine according to one of the preceding claims,
characterized in that
A suction device (21) is arranged upstream of the press nip (24), seen in the machine running direction (22), within the loop formed by the inner band (4). Machine according to claim 8,
characterized in that
the suction device (21) is assigned a blowing hood (20) for direct application of steam and / or hot dry air and / or hot moist air to the fibrous web (2). Machine according to one of the preceding claims,
characterized in that
Within the loop formed by the inner band (4) and between the press nip (24) and the transfer roller (13) a suction deflection roller (17) partially wrapped by the inner band (4) is arranged. Machine according to claim 10,
characterized in that
the suction deflecting roller (17) is partially wrapped by a permeable press belt (18) in direct contact with the fibrous web (2). Machine according to claim 11,
characterized in that
a hood (19) is provided within the loop formed by the press belt (18) and in the area of the wrap for indirectly applying steam and / or hot dry air and / or hot moist air to the fibrous web (2). Method for producing a fibrous web (2), in particular a tissue web, in which the fibrous web (2) is formed in a forming area, comprising a forming roller (5) and a permeable inner band wrapping it around at least partially together with an outer band (3) (4), and is further dewatered in a press device (7) directly following the forming area, comprising a press nip (24) formed by a press roll (8) and a counter roll (9) and the fibrous web (2) between the inner belt (4) and a lower press belt (11) is guided lying through the press nip (24), the press nip (24) being the first press nip (24) of the press device (7) through which the fibrous web (2) is guided and through one of the press device (7) subsequent drying cylinder (14) is dried, the fibrous web (2) in a transfer nip (12) formed between a transfer roller (13) and the drying cylinder (14) from the inner belt (4) is delivered to the heated surface of the drying cylinder (14), and the fibrous web (2) is guided from the forming area to the transfer, lying on the inner belt (4),
characterized in that
the inner band (4) is structured so that the fibrous web (2) is structured and the fibrous web (2) is guided between the inner band (4) and a lower press band (11) through the press nip (24). A method according to claim 13,
characterized in that
the lower press belt (11) is designed as a water-absorbing press belt, in particular as a press felt.

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