EP2090691A1 - Device for manufacturing sheets of tissue - Google Patents

Abstract

The device has a dewatering device (101) with an endless, permeable structure belt (6) i.e. felt belt, for guiding a tissue web (T) over a pressure applying device (12) that applies pressure on the tissue web, to a drying device (4). The pressure applying device is formed from a suction roll (13) and an opposite surface, where the suction roll is arranged within the endless permeable structure belt, and functions as a suction press roll. The opposite surface forms a press split (17) with the suction roll, and an endless, permeable dewatering belt (19) is guided by the press split.

Description

The invention relates to a device for producing tissue webs, comprising a device for dewatering with an endless, permeable structured band for guiding the tissue web via a device for applying a pressure to a drying device.

Devices for draining tissue webs are known in a variety of prior art designs. In general, in the wet pressing process, the fibrous web is compressed in a press nip in such a way that water is pressed out of the fibrous web by the hydraulic pressure. In this case, only a small part of the roll circumference is used for the Kompressiervorgang the fibrous web in conventional press equipment, which is why the drainage time and place is severely limited. To overcome this drawback, efforts have been made to use a solid impermeable belt to form an elongated press nip for applying pressure to and dewatering the fibrous web. However, the non-permeable belt prevents the flow of drying fluid, such as air, through the fibrous web.

It is also known from the prior art to use a so-called "through air drying process" (TAD) for drying a fibrous web, in particular tissue web, in order to reduce the required mechanical pressing fraction. However, suitable cylinders or honeycombs are necessary for this process, as well as a complex air supply and heating system. The use of TAD systems is therefore very complicated and expensive. Furthermore, the operating costs are also very high, since it is necessary, the fibrous web to a higher degree of drying to dry. The reason for this is the poorer cross-moisture profile achieved by the TAD system at lower degrees of drying.

From the publication WO 2005/075736 There is previously known a device for dewatering a fibrous web which comprises a permeable structured strip which guides the fibrous web over a suction roll, a permeable dewatering belt which contacts the fibrous web and also passes over the suction roll and a mechanism for applying a pressure to the web permeable structured band, the fibrous web and the permeable dewatering band. In this case, the permeable structured band is preferably used simultaneously as the fibrous suspension receiving band by this is an endlessly circulating belt part of a former, which adjoins a headbox. The pulp suspension is introduced into a gap, which is formed by the endless circulating permeable and structured band and another endless circulating band in the form of a forming screen, wherein the permeable structured band wraps around a forming roller and the pulp suspension at least in the wrap of the permeable structured band with the Forming roller is guided between the permeable structured band and the forming fabric. In this area, a very strong retention takes place, wherein following the forming roller, the two bands are separated from each other and the fibrous web is guided with the structured permeable belt to a mechanical screen press. The mechanism for applying pressure to the permeable belt, fibrous web and permeable dewatering belt in the area of the suction roll comprises an endlessly circulating belt, in particular a belt, which presses against the inside of the permeable structured belt in the area of the suction roll. The contact pressure is set by the size of the belt tension, whereby the maximum achievable pressure is relatively small. In order to achieve correspondingly high compression pressures, a correspondingly high tension of the press belt is required, which in turn leads to an increase in the cost of the belts.

Furthermore, additional pressing means acting on the press belt can be provided, which locally increase the contact pressure in the effective region of the press belt. Due to the high loads on the press nip area and due to the high suction and the desired residence time, a very large suction roll is required. Furthermore, a correspondingly high negative pressure and hot air quantities are required because of the triple covering a very high heat loss occurs. The pressure generating band is exposed to very high temperatures, which must be considered in the design of the band. The high temperatures also lead to a reduction in the lifetime. Since the pressure generating band is within the loop of the endlessly circulating permeable structured band, the risk of a band break is very high. The investment and operating costs are very high. A required replacement or change of the pressure applying band is very expensive and costly.

Due to the required large contact surface and the construction of the pressing device and their extension in the vertical direction, this is arranged in the machine direction between the forming unit and drying device, whereby a large machine length is generated.

The invention is therefore based on the object, a device for dewatering fibrous webs, in particular tissue webs of the type mentioned by a mechanical pressing device further develop such that the disadvantages mentioned are avoided. In particular, the operating and investment costs must be reduced, the space required to reduce and it should also be the known operations for tissue production as previously possible.

The solution according to the invention is characterized by the features of claim 1. Advantageous embodiments are described in the subclaims. The inventive device for producing a A tissue web comprising a device for dewatering with an endless, permeable structured band for guiding the tissue web via a device for applying a pressure to a drying device is characterized in that the device is formed by a suction press roll within the endless permeable structured strip Loop arranged suction roll and one with this one press nip forming counter surface is formed and at least one guided through the press nip endless permeable dewatering belt is provided. The structured permeable tape and the permeable drainage tape are passed through the press nip.

The solution according to the invention makes it possible to create a particularly space-saving press concept by displacing the suction roll acting as a suction press roll into the loop formed by the permeable structured strip. As a result, in particular, the space requirement for the management of the permeable drainage tape can be reduced.

In an advantageous embodiment, the device for applying the pressure in the direction of passage of the tissue web is viewed in the region of the extension of the drying device and arranged in the vertical direction offset therefrom. According to a particularly advantageous embodiment, the arrangement takes place below the drying device. The device is thereby free from a pressing pressure applying press belt, i. without screen press.

The solution according to the invention is characterized by the displacement of the device for applying the pressure in the already available and mostly unused space below the drying device by a very short and compact design. The mechanical drainage is thereby moved in the immediate vicinity of the drying device, resulting in very short guide paths for the tissue web between this and the device for applying a pressure, which greatly reduce the Rückbefeuchtungsvermögen and the cooling of the web, which in addition to the lower Investment costs for the leading tissue web bands due to their shorter lengths also in a reduction of the power requirement for the drying device.

The permeable structured band is guided along a partial area of the outer circumference of a suction roll, comprising at least one suction zone. The device for applying a pressure is designed and arranged such that it is suitable, as viewed in the direction of passage of the tissue web, to apply a localized pressure to the permeable structured strip and the tissue web guided thereon. In an advantageous embodiment, the device is designed and arranged such that it is suitable, in the direction of passage of the tissue web viewed in the inlet region in the suction zone or within the suction locally limited pressure on the permeable structured tape and applied to this tissue web. The device is to increase the functional concentration of the suction roller acting as a suction roll and formed with this one press nip forming pressure roller. According to the invention, the proportion of mechanically generated dewatering in the inlet region of the tissue web is thus increased in the dewatering section formed by the suction roll with the respective strip or strips. The press nip is positioned so that it is preferably at the beginning or within the suction zone. Because of the mechanical drainage laid at the beginning or in the suction zone and the moisture reduction on the tissue web achieved as a result, a through-flow drying device subsequently arranged in the device can become more effective. An additional heating of the bands is eliminated and the open flow area is considerably increased, since the entire, the press nip downstream Umschlingungsbereich the suction roller can be used to flow through.

According to a particularly advantageous embodiment, a flow-through drying device is arranged directly downstream of the press nip. This preferably comprises at least one hot air blowing device, which on Outer perimeter of the permeable structured band in the wrap on the suction roll or one of the device subsequently arranged Durchströmungstrocknungseinrichtung is effective. Preferably, the wrap area is identical at least to the theoretically possible suction zone or the suction zone is effective in the entire wrap area. Due to the upstream mechanical dewatering due to the arrangement of the pressure roller relative to the suction press roll, a reduction of the required length of the throughflow drying in the direction of passage is possible with the same drying result.

Since the highly stressed pressure belt is dispensed with in comparison with the prior art embodiments, the mechanical load on the suction roller and the air flow rate can be reduced overall. This is only looped by the structured band and the application of the contact pressure is limited to a short range. The suction roll can thereby be made considerably smaller in terms of their dimensions. This leads to a saving of space, which can be used in an optimal way to a shift of the entire device below the drying device. Furthermore, it is possible to design the suction roll of the same design and dimensions as other suction rolls in the system, so that only one single roll type has to be reserved for the reserve, which can be used in different areas in the device.

With regard to the configuration of the pressure roller there are a variety of possibilities. Preferably, however, a roller is selected which produces a soft press nip, that is to say a press nip, which is not only characterized by a line force but is slightly widened in the direction of passage. According to a first embodiment, this may be a conventional roller with a rigid shell, which is covered on the outer circumference with a correspondingly soft cover, which behaves elastically when acted upon or when the press nip is formed.

According to a further embodiment, it is conceivable to use a roll with deflection compensation. In this, a central support member is provided which is fixedly mounted and is guided rotatably about a jacket. The jacket is preferably highly elastic.

According to a further third embodiment, the pressure roller can also be designed as a shoe press roll. This is characterized by a flexible endless revolving roll shell, on the inner circumference of a stationary shoe can be pressed.

The design of the pressing element according to one of the possibilities offers the advantage that it can be used here on standardized pressure rollers. The slightly extended press nip leads overall to lower specific forces due to the increased contact surface.

The contact pressure by the pressure roller is controlled depending on the type of construction in a simple manner. The controllability can take place both transversely to the tissue web travel direction across the width and in the direction of passage, wherein the control is preferably carried out at least zonewise, most preferably continuously over the entire width. This makes it possible to influence the moisture cross profile over the tissue web width.

If the pressure roller is designed as a suction roller acting as a suction roller, it comprises at least one suction zone. In the direction of passage of the tissue web, the suction zone of the pressure roller of the suction zone can then be arranged upstream of the suction roller free of an overlap or else the suction zone of the pressure roller extends into the effective region of the suction zone on the suction roller. In the first case, there is definitely a rear ventilation before entry into the press nip, so that the effect of the contact force can be improved. In the second case, dewatering is forced in both directions within the press nip.

For the guidance of the permeable structured band arise in dependence on the configuration of the pressure roller and its surroundings a plurality of possibilities. According to a first embodiment, the permeable structured band wraps around the pressure roller at an angle in the range of 5 ° to 60 °, preferably between 35 ° and 45 °, before entering the press nip. As a result, due to the belt tension in the area of the pressure roller, the drainage is forced and furthermore a gentle pre-dewatering is achieved. In this case, the permeable structured band can be performed together with the permeable drainage tape in this wrap. According to a further embodiment, the permeable structured band wraps around the suction roll at an angle in the range of 0 ° to 60 °, preferably between 1 ° and 20 °, before entering the press nip. Again, a gentle pre-drainage is initiated by the applied vacuum before entering the press nip.

The support of the permeable structured band on its side opposite the tissue web supporting side opposite takes place at least indirectly on the outer circumference of the suction roll, ie directly or indirectly. In the first case, the suction roll is wrapped directly by the permeable structured band, ie free from arranged between the outer periphery of the suction roll and the inner periphery of the permeable structured band bands. In the second case, a permeable dewatering band is disposed within the loop formed by the permeable structured band. The permeable structured band is guided with its side supporting the tissue web opposite side over at least a portion of the Umschlingungsbereiches the permeable dewatering belt with the suction roll together with this on the outer circumference of the suction roll. The pressure roller is wrapped in the first case by a permeable drainage tape, in the second case only optional. The second arrangement is characterized by a particularly low remoistening capability.

The permeable structured band can be guided over a portion of its circulation path together with the permeable dewatering belt, wherein preferably at the exit from the press nip separation takes place from each other.

The individual rolls designed as suction rolls each comprise at least one suction zone, which is arranged at least partially in the looping area of a strip with the respective suction roll. The suction roller looped around by the permeable structured strip advantageously comprises a plurality of suction zones arranged one after the other in the direction of passage of the tissue web and differently loadable with respect to their effect in order to intensify the functions in the individual regions, for example throughflow drying.

The permeable dewatering belt which is guided through the press nip may be arranged either separately from the loop of the permeable structured belt or within it. In the first case, the dewatering belt contacts the tissue web as it passes through the press nip, i. the tissue web is passed between the permeable ribbon and the dewatering belt through the press nip. In the second case, the dewatering belt is disposed on the side away from the tissue web supporting side and wraps around the suction roll directly, whereby the rewet ability of the tissue web is greatly reduced. According to a particularly advantageous embodiment, both cases are used in combination.

The device is followed by a drying device, comprising at least one heatable drying cylinder or a throughflow drying device, in particular in the form of a flow-through cylinder. In order to form a further press nip acting as a transfer nip in the case of a drying cylinder, in the permeable structured strip, it is possible to set a workable on the outer circumference of the drying cylinder Pressure roller or suction roll arranged. The pressure roller forming the further press nip can be formed by a separate roller or else with an increased functional concentration of the suction roller. In the first case, the further pressure roller may be formed as a deflection compensating roller, conventional roller, shoe press roller.

According to a particularly advantageous embodiment, the guide rollers are arranged such that readily the pressing device can be removed from the web pass and a simple conversion and pivoting to form a normal Crescentformers is possible.

Figur 1a

verdeutlicht anhand einer Ansicht von Rechts den Grundaufbau einer erfindungsgemäßen Vorrichtung zur Herstellung von Tissuebahnen gemäß einer ersten besonders vorteilhaften Ausführung;

Figur 1 b

verdeutlicht anhand eines Ausschnittes aus Figur 1a eine Ausführung der Einrichtung zum Aufbringen eines Anpressdruckes;

Figuren 2 bis 2c

verdeutlichen beispielhaft mögliche Ausführungen der Anpresswalzen;

Figur 3

verdeutlicht anhand einer Ansicht von Rechts eine Weiterentwicklung einer Ausführung gemäß Figur 1a;

Figur 4

verdeutlicht anhand einer Ansicht von Rechts den Grundaufbau einer erfindungsgemäßen Vorrichtung zur Herstellung von Tissuebahnen gemäß einer zweiten Ausführung;

Figur 5

verdeutlicht anhand einer Ansicht von Rechts den Grundaufbau einer erfindungsgemäßen Vorrichtung zur Herstellung von Tissuebahnen gemäß einer Weiterentwicklung einer Ausführung aus Figur 1a sowie die mögliche zusätzliche Anordnung eines innenliegenden Entwässerungsbandes;

Figur 6

verdeutlicht eine besonders vorteilhafte Ausführung der Saugwalzen.

The solution according to the invention is explained below with reference to figures. The following is shown in detail:

FIG. 1a

illustrates on the basis of a view from the right the basic structure of an apparatus according to the invention for the production of tissue webs according to a first particularly advantageous embodiment;

Figure 1 b

illustrated by a section from FIG. 1a an embodiment of the device for applying a contact pressure;

FIGS. 2 to 2c

exemplify possible embodiments of the pressure rollers;

FIG. 3

illustrates a further development of an embodiment according to a view from the right FIG. 1a ;

FIG. 4

illustrated by a view from the right the basic structure of an apparatus according to the invention for the production of tissue webs according to a second embodiment;

FIG. 5

illustrated by a view from the right the basic structure of a device according to the invention for the production of tissue webs according to a further development of an embodiment out FIG. 1a as well as the possible additional arrangement of an internal dewatering belt;

FIG. 6

illustrates a particularly advantageous embodiment of the suction rolls.

The FIG. 1a illustrates in a schematic simplified representation based on a view from the right the basic structure of an inventively designed device 101 for dewatering fibrous webs, especially tissue webs T in a machine 100 for producing such fibrous webs, especially tissue webs T. In a coordinate system applied to the machine 100 describes the X- Direction of the machine direction MD, which corresponds to the transport direction of the fibrous web by the machine 100. The Y direction characterizes the width direction. For this purpose, the machine 100 comprises a headbox 1, which is arranged upstream of a forming unit 2, a press device 3 arranged downstream of the forming unit 2 and a drying device 4. The forming unit 2 comprises two endlessly circulating belts, in particular sieve belts. A first screen belt is here designated 5 and forms the forming fabric. The second band is designed as a permeable structured band 6. This is a sieve belt, which, however, contains pockets for substance storage. The permeable structured band 6 is guided over a plurality of individual guide rollers 7.1 to 7.n, of which at least one is drivable. In the region of the forming unit 2, the screen belt 5 and the permeable structured belt 6 are guided over a portion of their circulation path to form an inlet gap 9 for the pulp suspension S together. The guide is via a forming roller 8, which may be evacuated or formed without aspiration. The two screen belts, in particular the screen belt 5 and the permeable structured belt 6, form a first dewatering section in the wrapping area 10 with the forming roller 8, in which the pulp suspension S is dewatered on the forming roller 8 due to the belt tension. The screen belts 5, 6 are separated from each other after the wrapping region 10, wherein the resulting from the pulp suspension S Tissuebahn T on permeable structured band 6 on the device 101 to the drying device 4, in particular a heated drying cylinder 11 or to a flow-through drying device is performed. The drying cylinder is also referred to as Yankee cylinder. For this purpose, the device 101 comprises a device 12 for applying a contact pressure, in particular a locally limited pressure in the form of a press device 3, viewed through the tissue web T, through which the tissue web T between the permeable structured belt 6 and a permeable dewatering belt 19, preferably in the form a felt belt is guided. Downstream of the press device 3, the tissue web T is transferred from the permeable structured belt 6 to the drying cylinder 11. In an embodiment not shown here, the drying cylinder 11 can also be replaced by a flow-through cylinder. This is associated with a blast hood, for example.

The mechanical press device 3 is formed by a suction roller 13 designed and functioning as a suction press roll, which is arranged within the permeable structured belt 6 or around which the permeable structured belt 6 is guided over a partial region of its circulation path along the outer circumference 15 of the suction roller 13, as well as a Pressure roller 16. The suction roller 13 on the inner circumference 14 of the permeable structured belt 6 has at least one stationary suction zone 21 around which a roll shell 23 is rotatably and drivably mounted. The suction zone 21 preferably extends over the entire wrap area 24 of the permeable structured band 6 on the suction roll 13. The pressure roll 16 forms a press nip 17 with the suction roll 13. By means of this, the tissue web T to be dewaxed is formed between the outer periphery 18 of the permeable structured band 6 and the permeable drainage tape 19. The pressure roller 16 is arranged for this purpose within the permeable dewatering belt 19. The permeable dewatering belt 19 wraps around a portion of the outer periphery 20 of the pressure roller 16. The press nip 17 is formed such that it is formed in the suction roller 13 Suction zone 21 is arranged upstream or in the region of the inlet into the suction zone 21. The inlet region into the suction zone 21 is designated here by 22. The permeable dewatering belt 19 is in the simplest case a felt belt. Other versions are conceivable depending on the mode of operation. The permeable structured band 6 and the permeable drainage band 19 are for this purpose performed at least through the press nip 17, but preferably also over a partial region of their circulation path. The region of the common guidance takes place here on the pressure roller 16, whereby the separation of the permeable structured belt 6 and the permeable drainage belt 19 takes place downstream of the press nip 17. The area of the common guidance can be generated before or just exactly in the press nip 17. After passing through the press nip 17 and the separation between permeable structured belt 6 and the permeable dewatering belt 19, the tissue web T is guided on the outer circumference 18 of the permeable structured belt 6 to the drying device 4, in particular the drying cylinder 11. The guide takes place along the outer circumference of the suction roll 13. Downstream of the press nip 17, preferably in the region of the suction zone 21, is a through-flow drying device 25, which acts on the wrapping region 24 formed by the permeable structured band 6 and the suction roll 13. In the simplest case, the flow-through drying device 25 is a so-called steam blower box 26 or another heating element, which acts on the tissue web T in the looping area 24. In this flow-through drying, application and penetration of a drying fluid takes place on the tissue web T, wherein, due to the arrangement of the suction zone 21 directly opposite the drying action region, removal of the drying fluid takes place. The press nip 17 is positioned such that it lies in the inlet region of the device 101 and preferably within the vacuum zone or in the inlet region 22 of the suction zone 21. Due to the mechanical dewatering of the tissue web T laid in the inlet region 22 of the suction zone 21, the subsequent throughflow drying device 25 can be more effective be and at the same drying effect can be made smaller. The heating takes place directly, that is free from an intermediate covering on the tissue web T.

Due to the formation of a contact force by the force in the press nip 17 free of a press belt, the burden of these supporting in the prior art suction roller 13 can be reduced, whereby the suction roller 13 can be dimensioned smaller overall. The arrangement of the press device 3 takes place in the axial extent of the drying device 4, in particular the drying cylinder 11 relative to the machine direction MD, but at least partially offset in the vertical direction, preferably completely below this, whereby a very compact construction of the entire device 101 and thus the Machine 100 can be realized.

The transfer to the drying cylinder 11 can be done either directly from the suction roller 13. Otherwise, a further pressure roller 27 is preferably provided, which performs the function of pressing the permeable structured belt 6 to form a press nip 28 with the drying cylinder 11 and also the function of Guide in the manner of a guide roller. The distance formed in the direction of rotation of the structured permeable belt 6 between the press nip 17 and the press nip 28 formed on the drying cylinder 11 by the press roll 27 is very short. The guided on the fabric, in particular the permeable structured band 6 tissue web T is thereby cooled lower.

By the solution according to the invention, on the one hand, the proportion of mechanical dewatering is intensified and advanced to the beginning, that is, the inlet of the dewatering section formed by the press device 3.

The press nip 17 forming the pressure roller 16 may be designed in various ways. The FIG. 1b illustrated by a section according to FIG. 1a a particularly advantageous embodiment with the formation of a pressure roller 16 in the form of a suction roller acting as a suction roller 30. These and the suction roller 13 are preferably carried out to reduce the storage equal. The suction roll 30 here also comprises at least one suction zone 31 which extends in the circumferential direction and extends at least partially in the wrap area 32, preferably completely in the wrap area 32 of the permeable drainage belt 19 with the pressure roller 16. This area simultaneously forms a region 33 in which the two belts, the permeable structured belt 6 and the permeable dewatering belt 19, are guided together around the outer circumference 20 of the pressure roller 16 to the press nip 17. This formed by the common leadership of the two bands 6 and 16 area 33 describes a drainage section. By the pre-looping of the suction roll 30 with the tissue web T leading permeable structured band 6, wherein the 33 describing wrap angle in the range of 5 ° to 60 °, preferably 40 °, a gentle pre-dewatering is realized by the effective suction zone 31. Further recognizable in FIG. 1b is the after taking place through the press nip 17 on the suction roll 13 taking place separation between the permeable structured band 6 and the permeable drainage tape 16, wherein the tissue web T is continued with the permeable structured band 6. The in the FIG. 1b illustrated suction zone 21 is characterized by two in the direction of passage of the tissue web T in the circumferential direction on the suction roller 13 connected in series formed suction zones 21I and 21II, which are differently acted upon by a suction force. Furthermore, the suction zones 21 and 31 of the suction roll 13 and pressure roll 16 can advantageously be superimposed, at least in the press nip 17, to support dewatering on both sides.

According to a particularly advantageous embodiment, both suction rolls 13, 30 on a soft roll cover, which in addition to the suction holes, such as in FIG. 6 based on a section of FIG. 1b shown formed grooved.

The in the FIGS. 1a and 1b reproduced embodiment represents a particularly advantageous embodiment, in which the press nip 17 of two suction rolls, a first suction roll 13 and formed as a pressure roller 16 suction roll 30, are formed.

Each of the belts, in particular the permeable structured belt 6 and the permeable drainage belt 19, preferably have their own conditioning device, comprising pipe suction and / or spray pipes.

The FIGS. 2a to 2c illustrate possible embodiments of the pressure roller 16 and optionally also 27 for use in an arrangement according to FIG. 1 , According to FIG. 2a the pressure roller 16 is formed as a roller with a rigid roll shell or roller body 34 which is provided on the outer periphery 35 with an elastic cover 36 which may be grooved and / or blind drilled. As a result, the press nip 17 is designed to be softer, that is to say in the direction of passage of the tissue web T, as a result of elastic deformation of the extended press nip, thereby avoiding high line forces.

According to another embodiment in FIG. 2b It is conceivable to carry out the pressure roller 16 as a deflection compensating roller 37, for example with a rotatably mounted and drivable elastic sheath 38, which is supported by means 39 for deflection compensation, in particular pressing elements 40, on a central carrier element 41. For controlling the contact force in and / or transversely to the machine direction MD, a corresponding adjusting device 42 is preferably provided.

The Figure 2c illustrates another possible embodiment of the pressure roller 16 in the form of a shoe press roll 43. This includes a flexible rotatable roll shell 44, which is about an acting on the inner circumference 45 expectant Press shoe 46 to the suction roller 13 with the formation of the press nip 17 can be pressed.

These in the FIGS. 2a to 2c shown theoretically possible versions in addition to the FIG. 1a In the same way, the embodiment of the suction roll 16 also applies to the pressure roll 27 for forming the press nip 28 for transferring the tissue web T to the drying cylinder 11. However, it is also conceivable to provide only a conventional roll with a rigid roll shell.

The FIG. 3 clarifies a further development according to FIG. 1a in which the pressure roller 16 is formed as a rigid roller and on the suction roller 13 designed as a suction roller 13 of the formation of the press nip 17 and in the region of the inlet 22 of the suction zone 21 is effective at this. In this case, eliminates a common guide region of the two bands, in particular the permeable structured band 6 and the permeable drainage tape 19. The pressure roller 16 is formed as a conventional press roll, deflection compensating roll or shoe press roll. The suction roller 13 is pre-looped by the tissuebahnführenden structured permeable belt 6 in front of the press nip 17 at an angle in the range of 0 - 30 °, preferably 5 ° to 15 °, so that the most gentle pre-dewatering takes place. The suction roller 13 is surrounded for this purpose by a water collecting channel.

The FIG. 4 illustrates another embodiment of an inventively designed dewatering apparatus 101 in a machine 100 for dewatering a tissue web, in which a further permeable dewatering belt 47 is disposed within the structured permeable belt 6 and the suction roller acting as a suction roll 13 directly on the outer circumference 15 wraps over a portion of its outer periphery , wherein the guide of the permeable structured band 6 takes place together with the dewatering belt 47 along the outer periphery 15 of the suction roll 13. The tissue web T is at the outer periphery 18 of the permeable structured band 6 out. The press nip 17 is also formed here by a pressure roller 16 in cooperation with the suction roll 13, wherein this is effective in the looping of the suction press roll 13 with both bands 6 and 47 at this. The pressure roller 16 may also be a conventional pressure roller, a deflection compensating roller or a shoe press roller. Since the nip roller 16 is arranged and formed in contact with the tissue web T, it is preferably provided with a smooth delivery-friendly cover and with a device for removing fibers, fines and stickies from the surface, in particular a scraper. After the area of through-flow drying, the dewatering belt 47 is led away from the permeable structured belt 6 leading the tissue web T. The fact that a dewatering belt 47 is located under the tissue-web-guiding permeable structured belt 6 and that suction through the tissue web T, the permeable structured belt 6 and the permeable dewatering belt 19, in particular in the form of a felt belt to the suction roller 13, can result in particularly low-moisture drainage occur. The arrangement of the dewatering belt 19 in the FIG. 4 can be optional. The permeable dewatering belts 19 and 47 are preferably formed as felt belts.

The FIG. 5 illustrates an advantageous development with a combination of the versions of FIG. 1a and FIG. 4 , In this, the upper, acting as a suction press roll suction roll 13 simultaneously forms the pressure roller 27 with the drying cylinder 11 and thus the so-called transfer gap 28 to the Yankee cylinder. In this case, the suction roll 13 may optionally be looped around by a dewatering belt 47, in particular a felt belt, arranged within the permeable structured belt 6 in order to achieve a particularly low remoistening. However, this is not mandatory. The pressure roller 27 is formed here by the suction roller 13 in a particularly advantageous manner and with a high functional concentration.

All in the FIGS. 1 to 5 illustrated embodiments with respect to the arrangement of the guide rollers for the guidance of the permeable structured band designed and arranged so that their leadership can also be used to guide a Crescentfilzes as in a Crescentformer by the permeable structured band 6 replaced by such a band, in particular a Crescentfilzband is, which then already cooperates with the forming fabric 5 in the forming area 2. For this purpose, it may further be provided to make the individual rollers, in particular suction roller 13 and / or pressure roller 16, pivotable or at least reversible or deactivatable in their effect, so that they still act as a guide roller, but ineffective in terms of their effect as a press nip are.

LIST OF REFERENCE NUMBERS

1

headbox

2

forming unit

3

press means

4

dryer

5

screen belt

6

permeable structured belt or in conventional driving felt belt

7

guide roll

8th

forming roll

9

inlet gap

10

wrap region

11

Drying cylinder or throughflow drying unit

12

Facility

13

suction roll

14

inner circumference

15

Outer circumference of the suction roll

16

pressure roller

17

press nip

18

Outer circumference of the permeable structured band

19

permeable drainage tape

20

Outer circumference of the pressure roller

21

suction zone

22

intake area

21.I

first suction zone

21.II

second suction zone

23

roll shell

24

Wrap around the suction roll

25

Flow drying device

26

steam blow

27

pressure roller

28

press nip

30

suction roll

31

stationary suction zone

32

wrap region

33

Area

34

roll shell

35

outer periphery

36

elastic cover

37

Deflection roll

38

roll shell

39

Means for deflection compensation

40

presser

41

central carrier element

42

setting device

43

Shoe press roll

44

roll shell

45

inner circumference

46

press shoe

47

permeable drainage tape

T

tissue web

S

Fibrous suspension

MD

machine direction

100

Machine for producing a fibrous web, in particular tissue web

101

Device for dewatering fibrous webs

Claims (39)

Apparatus (100) for the production of tissue webs (T), comprising a device (101) for dewatering with an endless, permeable structured band (6) for guiding the tissue web (T) via a device (12) for applying a pressure to the tissue web (T) to a drying device (4)
characterized,
in that the device (12) is formed by a suction roll (13) which acts as a suction press roll and is arranged within the loop formed by the endless permeable structured strip (6) and a counter surface forming a press nip (17), and which is pressed through the press nip (17). guided endless permeable drainage tape (19, 47) is provided. Device (100) according to claim 1,
characterized,
is that the device (12) in the passage direction of the tissue web (T) is considered in the region of the extent of the drying apparatus (4) and arranged offset in the vertical direction to this. Device (100) according to claim 2,
characterized,
in that the device (12) for applying the pressure in the direction of passage of the tissue web (T) is arranged in the region of the extension of the drying device (4) in the machine direction (MD) and below it. Device (100) according to one of claims 1 to 3 "
characterized,
in that the permeable structured strip (6) is guided along a partial area of the outer circumference (15) of a suction roll (13) comprising at least one suction zone (21) and the device (12) is designed and arranged such that it is suitable in the direction of passage the tissue web (T) in the inlet region (22) into the suction zone (21) or within the suction zone (21) of the suction roll (13) localizes a pressure on the permeable structured strip (6) and the tissue web (T) guided thereon applied. Device (100) according to one of claims 1 to 4,
characterized,
that the press nip (17) with the suction roll (13) forming the counter-surface (12) of a pressure roller (16) is formed. Device (100) according to claim 5,
characterized,
in that the press nip (19) formed between the pressure roller (16) and the suction roller (13) is designed as a soft press nip. Device (100) according to claim 5,
characterized,
in that the pressure roller (16) comprises a rigid roller shell (34) or roller body which has an elastic cover (36) on the outer circumference (35). Device (100) according to claim 5,
characterized,
in that the pressure roller (16) is designed as a deflection compensating roller (37), comprising a central carrier element, in particular a stationary carrier body (41) and an elastic roller shell (38) rotatable about the carrier body (41) and Roll jacket (38) arranged and controllable by means of at least one adjusting device (42) controllable means (39, 40) for deflection compensation on the support body (41). Device (100) according to claim 5,
characterized,
in that the pressure roller (16) is designed as a shoe press roll (43), comprising a flexible rotatable roll shell (44) and a stationary press shoe (46) which can be pressed against the inner circumference (45) of the flexible, rotatable roll shell (44). Device (100) according to claim 5,
characterized,
in that the pressure roller (16) is designed as a suction roller (30) acting as a suction pressure roller, comprising at least one suction zone (31). Device (100) according to claim 10,
characterized,
that in the travel direction of the tissue web (T) the suction zone (31) of the pressure roller (16) is arranged upstream of the suction zone (21) of the suction roll (13). Device (100) according to claim 10 or 11,
characterized,
that in the travel direction of the tissue web (T) the suction zone (31) of the pressure roller (16) extends into the active region of the suction zone (21) of the suction roll (13). Device (100) according to one of claims 5 to 12,
characterized,
that the pressing force of the pressure roller (16) over the width of the press nip (19) perpendicular to the running direction of the web of tissue (T) and / or is considered to be controlled in the direction of passage. Device (100) according to one of claims 5 to 13,
characterized,
in that the permeable structured band (6) wraps around the pressure roller (16) at an angle in the range of 5 ° to 65 °, preferably between 35 ° and 45 °, before entering the press nip (17). Device (100) according to one of claims 1 to 14,
characterized,
in that the permeable structured strip (6) wraps around the suction roll (13) at an angle in the range of 0 ° to 60 °, preferably between 1 ° and 20 °, before entering the press nip (17). Device (100) according to one of claims 1 to 15,
characterized,
in that the permeable structured band (6), with its side opposite the tissue web (T) (18), is supported at least indirectly on the outer circumference of the suction roll (13). Device (100) according to claim 16,
characterized,
that the suction roll (13) directly from the permeable structured belt (6) is looped. Device (100) according to claim 16,
characterized,
in that a permeable dewatering band (47) is arranged within the loop formed by the permeable structured band (6) and the permeable structured band (6) is arranged with its to the tissue web (T). supporting side (18) opposite side at least over a portion of the Umschlingungsbereiches the permeable dewatering belt (47) with the suction roller (13) is guided together with this by the press nip (17). Device (100) according to one of claims 5 to 18,
characterized,
that the pressure roller (16) by a permeable dewatering belt (19) is looped. Device (100) according to claim 18,
characterized,
that the pressure roller (16) is free from a loop through a permeable dewatering belt. Device (100) according to claim 19,
characterized,
in that the permeable structured band (6) is guided over a partial region of its circulation path together with the permeable drainage band (19) and both are guided separately from one another at the exit from the press nip (17). Device (100) according to one of claims 1 to 21,
characterized,
in that the device (12) is arranged downstream of a throughflow drying device (25) in the direction of passage of the tissue web (T). Device (100) according to one of claims 1 to 22,
characterized,
that viewed in the direction of passage of the tissue web (T), the through-flow drying device (25) is immediately downstream of the press nip (17). Device (100) according to claim 22 or 23,
characterized,
in that the flow-through drying device (25) comprises at least one hot air blowing device (26) which is arranged on the suction roll (13) on the suction roll (13) on the outer circumference (18) of the permeable structured strip (6) in the wrapping region (24). Device (100) according to one of claims 1 to 24,
characterized,
in that the individual suction roll (13, 30) comprises at least one suction zone (21, 31) and the suction zone (21, 31) is arranged at least partially in the looping area of a band with the respective suction roll (13, 30). Device (100) according to claim 25,
characterized,
different from that the permeable structured belt (6) looped around the suction roll (13) has a plurality in the direction of passage of the tissue web (T) arranged behind one another viewed acted upon suction zones (21I, 21II) comprising. Device (100) according to claim 26,
characterized,
that the press nip (17) is disposed between the pressure roller (16) and the suction roll (13) in the area of the first suction zone (21I). Device (100) according to claim 27,
characterized,
in that the flow-through drying device (25) is assigned to the second zone (21II) and can be flowed through by a liquid or gaseous medium. Device (100) according to one of claims 1 to 28,
characterized,
that the drying apparatus (4) comprises at least one heatable drying cylinder (11). Device (100) according to one of claims 1 to 28,
characterized,
that the drying apparatus (4) at least one through-flow drying unit, in particular comprising a flow-through drying cylinder. Device (100) according to one of claims 29 to 30,
characterized,
in that the drying device (4) is associated with a pressure roller (27) or suction roller arranged in the permeable structured belt (6) to form a further press nip (28) acting as a transfer nip for the tissue web (T). Device (100) according to claim 31,
characterized,
that the suction roll forming the further press nip (28) is constructed by the suction roll with regard to its design and dimensions identical to the suction roll (13) in the permeable structured strip (6). Device (100) according to one of claims 31 or 32,
characterized,
in that the further suction roll is formed by the suction roll (13) of the device (12) on the inner circumference of the permeable structured strip (6). Device (100) according to claim 31,
characterized,
that the further pressure roller (27) is designed as a rolling of the following: - Shoe press roller - Deflection compensation roll - Press roll Device (100) according to one of claims 1 to 34,
characterized,
in that it comprises a headbox (1) and a forming fabric (5), which is guided together to form a gap (9) over a partial region of the circulation path with the permeable structured band (6). Device (100) according to one of claims 1 to 35,
characterized,
in that the permeable structured band (6) is designed as a screen belt with pockets. Device (100) according to one of claims 1 to 36,
characterized,
in that the permeable dewatering belt (19, 47) is designed as a felt belt. Device (100) according to claim 37,
characterized,
that the felt is formed multi-layered. Device (100) according to one of claims 1 to 38,
characterized,
in that the arrangement of the guide rolls (7.1 to 7.n) for the permeable structured strip (6) and optionally the permeable drainage strip (9) is designed so as to be suitable for guiding a crescent felt bypassing the device (36).

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