Method and machine for producing a fibrous web stretchable in the transverse direction

Abstract

In a method for producing a transversely stretchable fibrous web, particularly a transversely stretchable paper or board web, a fibrous web from a predrying section of a relevant production machine is brought into contact with a heated, vapor-impermeable, and smooth rotating cylinder. Together with a vapor-impermeable, circumferential elastic band, the fibrous web is guided transversely over the heated cylinder at a predetermined or predeterminable wrap angle between the elastic band and the heated cylinder and pressed against the heated cylinder by the elastic band. Prior to contact with the fibrous web, the elastic band is subjected to a variably adjustable and / or controllable prestressing force in the transverse direction. After a vapor cushion is formed between the fibrous web and the heated cylinder, the prestressing force of the elastic band in the transverse direction is reduced again, so that the fibrous web slides on the heated cylinder along with the elastic band in the transverse direction. A machine for carrying out the method is also provided.

Description

[0001] The invention relates to a method for producing a fibrous web that can be stretched in the transverse direction. The invention also relates to a machine for producing a fibrous web that can be stretched in the transverse direction, which is particularly suitable for carrying out this method.

[0002] Until now, there have been no tools for directly controlling or regulating the transverse strain properties (CD elasticity) of paper. The shrinkage curve occurring in the cross direction (CD = cross direction) or CD shrinkage characteristic has been explicitly attributed to the drying of the paper. Consequently, paper manufacturers have previously been able to influence the CD elasticity or CD shrinkage characteristic only at the expense of stabilizing the web with web stabilization boxes, an unsatisfactory approach. Specifically, machine manufacturers can roughly influence the CD shrinkage characteristic through drying concepts, such as single-lane or double-lane drying sections. However, compromises are also necessary here.

[0003] Reduced strain resistance or excessively low elasticity has a particularly negative impact on corrugated cardboard. Consequently, the cardboard can break at the grooves, rendering it unusable as a defective product. Brittle corrugated cardboard boxes break under impact because the energy of the impact cannot be absorbed. Furthermore, when corrugating a corrugated web, if the elasticity is too low, the web can break during the fluting process. Excessive brittleness is also disadvantageous here.

[0004] To specifically adjust the longitudinal stretch of the paper (MD elasticity; MD = machine direction) or to produce longitudinally oriented micro-folds (micro-folds), the known Clupak system is used. Here, the still-damp web is run through a nip together with the rubber cloth, whereby the web and the rubber cloth are stretched. After the nip, the rubber cloth is shortened again, producing the desired micro-folds in the web.

[0005] The technical problem addressed by the present invention is to provide a method and a machine of the type mentioned in the introduction, by which the aforementioned disadvantages can be overcome. In particular, the goal is to achieve targeted control, regulation, or improvement of the elasticity or transverse strain characteristics of the fibrous web in the transverse direction and the energy consumption in the transverse direction. Furthermore, a feasible solution for counteracting the deterioration of the quality of the waste paper raw material should be created.

[0006] According to the invention, this object is achieved by a method having the features of claim 1 and a machine having the features of claim 13. Preferred embodiments of the method according to the invention and preferred embodiments of the machine according to the invention are derived from the dependent claims, the present description and the drawings.

[0007] The method according to the invention for producing a fibrous web stretchable in the transverse direction, in particular a paper or board web stretchable in the transverse direction, is characterized in that the fibrous web coming from the predrying section of the relevant production machine is brought into contact with a heated, water vapor-impermeable, and smooth rotating cylinder and, together with a surrounding, water vapor-impermeable elastic band, is guided transversely over the heated cylinder at a predetermined or predeterminable wrap angle between the elastic band and the heated cylinder, i.e., the cylinder surface, and is pressed against the heated cylinder by the elastic band. Before coming into contact with the fibrous web, the elastic band is loaded in the transverse direction with a preload force that can be variably adjusted and / or controlled. After a steam cushion has formed between the fibrous web and the heated cylinder, the preload force of the elastic band generated in the transverse direction is reduced again, so that the fibrous web slides on the heated cylinder via the steam cushion together with the elastic band in the transverse direction, in particular shrinks in a controlled, intensified manner.

[0008] This embodiment of the method according to the invention allows for targeted control, regulation, or improvement of the transverse elasticity or transverse strain characteristics of the fibrous web and its transverse energy absorption. Furthermore, it creates a solution for counteracting the deterioration of the quality of the waste paper raw material. The fibrous web emerging from the predrying section collides with a transversely prestressed elastic band. After the steam cushion is formed between the fibrous web and the heated cylinder, the prestressing force of the elastic band is reduced again. This allows the fibrous web to slide on the heated cylinder via the steam cushion and contract in the transverse direction together with the elastic band, thereby generating micro-wrinkles.

[0009] As the heated cylinder, a steel cylinder, in particular a chromium-plated steel cylinder, is preferably used. By means of this, in particular a chromium-plated steel cylinder, it is ensured that the fibrous web can slide optimally on the steel cylinder after the steam cushion has been formed.

[0010] Advantageously, the elastic band is pretensioned in the transverse direction by at least one variably adjustable tensioning roller arranged within its loop.

[0011] By means of the variably adjustable transverse preload using the tensioning roller, the transverse contraction occurring after the preload is reduced can be controlled or regulated accordingly.

[0012] The prestressing force of the elastic band generated in the transverse direction is advantageously reduced again, viewed in the web running direction, between a variably adjustable tensioning roller arranged within the loop of the elastic band and a guide roller arranged within the loop of the elastic band.

[0013] After the spring band running over the guide roller is subjected to minimal or no prestressing in the region of the guide roller, the prestressing of the spring band between the tensioning roller and the guide roller can still be continuously reduced.

[0014] According to a preferred practical embodiment of the method according to the invention, which is intended for relatively low machine or web running speeds, preferably for machine or web running speeds of <1000 m / min, a steam cushion is generated between the fibrous web and the heated cylinder in a nip, which is arranged in the initial region of the zone of the heated cylinder surrounded by the fibrous web and the elastic band, as viewed in the web running direction, and is formed between the heated cylinder and a squeeze roller arranged within the loop of the elastic band, which squeeze roller is simultaneously designed as a variably adjustable tensioning roller, by which the elastic band is pretensioned in the transverse direction.

[0015] By simultaneously designing the initial squeezing roller, which is provided for forming the steam cushion between the fibrous web and the heated cylinder, as a variably adjustable tensioning roller, the elastic band can be subjected to the respectively desired prestressing force in the transverse direction.

[0016] It is particularly advantageous here that a guide roller for holding the elastic belt and the fibrous web on the heated cylinder is arranged in the rear area of ​​the area of ​​the heated cylinder surrounded by the fibrous web and the elastic belt as viewed in the web running direction, within the loop of the elastic belt, so that the preload force generated in the transverse direction of the elastic belt is reduced again between the pressing zone and the guide roller for generating the transverse contraction of the fibrous web, the pressing zone being arranged in the initial area of ​​the area of ​​the heated cylinder surrounded by the fibrous web and the elastic belt as viewed in the web running direction, and the guide roller being arranged in the rear area of ​​the area of ​​the heated cylinder surrounded by the fibrous web and the elastic belt as viewed in the web running direction.

[0017] The elastic band is expediently removed from the heated cylinder by guide rollers, which are arranged in the rear region of the heated cylinder's area surrounded by the fibrous web and the elastic band, as viewed in the web running direction, and the fibrous web is separated from the elastic band again.

[0018] According to a preferred practical embodiment of the method according to the invention, which is intended for relatively high machine or web speeds, preferably for machine or web speeds of >1000 m / min, the fibrous web is first guided together with the pre-tensioned elastic band along a pretreatment or heating zone past a heated cylinder, so that a steam cushion is formed between the fibrous web and the heated cylinder while the elastic band is held in a pre-tensioned manner.

[0019] In this case, a vapor cushion is formed in the pre-treatment or heating zone.

[0020] It is particularly advantageous here if the elastic band is supplied to the fibrous web in contact with the heated cylinder by means of a variably adjustable tensioning roller which pre-tensions the fibrous web, and a nip is provided at the end of the pre-treatment or heating zone to improve the adhesion of the fibrous web to the elastic band, said nip being formed between the heated cylinder and a squeeze roller arranged within the loop of the elastic band, said squeeze roller being simultaneously designed as a variably adjustable tensioning roller for maintaining the pre-tensioning force of the elastic band in the preceding pre-treatment or heating zone, and after the nip provided at the end of the pre-treatment or heating zone, the fibrous web is further guided together with the elastic band through the heated cylinder along a contraction zone, along which the pre-tensioning force of the elastic band for producing the transverse contraction of the fibrous web is reduced again.

[0021] The nip provided at the end of the pretreatment or heating zone thus creates a good adhesion between the fibrous web and the prestressed elastic band. While the fibrous web adheres securely to the elastic band, the presence of the steam cushion further ensures full mobility of the fibrous web relative to the heated cylinder.

[0022] In this case, the fibrous web is advantageously fed together with the elastic band after the shrinking zone to guide rollers, by means of which the fibrous web and the elastic band are removed again from the heated cylinder and separated from one another.

[0023] The elastic band can nevertheless be loaded via corresponding guide rollers with a basic stress that is less than the preload force by a defined amount.

[0024] The fibrous web contracted in the transverse direction is preferably fed to a post-drying section of the production machine, wherein the transverse contraction is fixed there.

[0025] The machine according to the invention for producing a fibrous web that can be stretched in the transverse direction, in particular a paper or cardboard web that can be stretched in the transverse direction, which is particularly suitable for carrying out the method according to the invention, is characterized in that the machine comprises a heated, water vapor-impermeable and smooth rotating cylinder and a water vapor-impermeable, surrounding elastic belt, wherein the fibrous web and the elastic belt are guided together transversely through the heated cylinder at a predetermined or predeterminable wrap angle between the elastic belt and the heated cylinder and are pressed against the heated cylinder by the elastic belt, and before contact with the fibrous web, the elastic belt can be loaded in the transverse direction with a preload that can be variably adjusted and / or controlled, and after a steam cushion has been formed between the fibrous web and the heated cylinder, the preload of the elastic belt generated in the transverse direction can be reduced again, so that the fibrous web slides on the heated cylinder in the transverse direction together with the elastic belt via the steam cushion.

[0026] In this case, a steel cylinder, in particular a chromium-plated steel cylinder, is preferably provided as the heated cylinder.

[0027] The elastic band can expediently be pretensioned in the transverse direction by means of at least one variably adjustable tensioning roller arranged within its loop.

[0028] It is particularly advantageous here that the prestressing force of the elastic band generated in the transverse direction can be reduced again between a variably adjustable tensioning roller arranged within the loop of the elastic band and a guide roller arranged within the loop of the elastic band, viewed in the web running direction.

[0029] According to a preferred embodiment of the machine according to the invention, which is intended for relatively low machine or web running speeds, preferably for machine or web running speeds of <1000 m / min, a steam cushion is generated between the fibrous web and the heated cylinder in a nip, which is arranged in the initial region of the zone of the heated cylinder surrounded by the fibrous web and the elastic band, as viewed in the web running direction, and is formed between the heated cylinder and a squeeze roller arranged within the loop of the elastic band, the squeeze roller being simultaneously designed as a variably adjustable tensioning roller, by means of which the elastic band is pretensioned in the transverse direction.

[0030] Here, it is preferred that, in an area of ​​the heated cylinder surrounded by the fibrous web and the elastic band, which is located at the rear as viewed in the web running direction, a guide roller for holding the elastic band and the fibrous web on the heated cylinder is arranged within the loop of the elastic band, so that the preload force generated in the transverse direction of the elastic band is reduced again between the pressing zone and the guide roller for generating the transverse contraction of the fibrous web, the pressing zone being arranged in an initial area of ​​the heated cylinder surrounded by the fibrous web and the elastic band, as viewed in the web running direction, and the guide roller being arranged in an area of ​​the heated cylinder surrounded by the fibrous web and the elastic band, which is located at the rear as viewed in the web running direction.

[0031] The elastic band is advantageously removed from the heated cylinder by guide rollers which are arranged in the rear region of the region of the heated cylinder surrounded by the fibrous web and the elastic band, viewed in the web running direction, and separated from the elastic band again.

[0032] According to a preferred embodiment of the machine according to the invention, which is intended for relatively high machine or web running speeds, preferably for machine or web running speeds of >1000 m / min, the fibrous web is first guided together with the pre-tensioned elastic band along a pretreatment or heating zone past a heated cylinder, so that a steam cushion is formed between the fibrous web and the heated cylinder while the elastic band is held in a pre-tensioned manner.

[0033] It is particularly advantageous here that the elastic band can be supplied to the fibrous web in contact with the heated cylinder by means of a variably adjustable tensioning roller which pre-tensions the fibrous web, and a nip is provided at the end of the pre-treatment or heating zone to improve the adhesion of the fibrous web to the elastic band, the nip being formed between the heated cylinder and a squeeze roller arranged within the loop of the elastic band, the squeeze roller in turn being designed as a variably adjustable tensioning roller for maintaining the pre-tensioning force of the elastic band in the preceding pre-treatment or heating zone, and the fibrous web being guided further through the heated cylinder together with the elastic band along a contraction zone after the nip provided at the end of the pre-treatment or heating zone, along which the pre-tensioning force of the elastic band for producing the transverse contraction of the fibrous web can be reduced again.

[0034] In this case, the fibrous web is expediently fed together with the elastic band after the shrinking zone to a guide roller, by means of which the fibrous web and the elastic band are removed again from the heated cylinder and separated from one another.

[0035] The elastic band can nevertheless be loaded via corresponding guide rollers with a basic stress that is less than the preload force by a defined amount.

[0036] The prestressing force of the elastic band can advantageously be adjusted by means of a tensioning body which is arranged laterally on the roller body of the respective tensioning roller and which can be variably adjusted relative to the roller body in the transverse direction of the machine.

[0037] According to a preferred practical embodiment of the machine according to the invention, the elastic belt is provided with reinforcing threads extending at least essentially in the transverse direction and having a correspondingly adapted modulus of elasticity or, in particular, with a correspondingly adapted thread layer with regard to its thread density, so that the transverse straining of the fibrous web is influenced symmetrically with respect to a central longitudinal axis of the elastic belt parallel to the machine running direction.

[0038] It is also particularly advantageous here if the reinforcing threads or thread layers of the elastic band extending in the transverse direction are adapted accordingly to compensate for the trough-shaped shrinkage curve that usually occurs in the transverse direction during drying of the fibrous web.

[0039] Furthermore, the elastic band can also be provided with reinforcing threads which extend at least substantially in the machine direction.

[0040] The elastic band expediently consists at least substantially of rubber.

[0041] The elastic band preferably has a hardness in the range of 55 + / - 10 Shore A (107 P&J).

[0042] Furthermore, it is advantageous if the elastic band has a strength of approximately 1.2 kg / dm 3 About 1.5kg / dm 3 density in the range of .

[0043] The elastic band advantageously has a thickness in the range of approximately 20 mm to approximately 30 mm, wherein the elastic band preferably has a thickness of approximately 25 mm.

[0044] Another advantageous embodiment of the machine according to the invention is characterized in that

[0045] - the dry weight content of the fibrous web supplied to the heated cylinder is in the range of about 50% to about 65% and / or

[0046] The heatable cylinder has a diameter in the range of approximately 900 mm to approximately 1500 mm and / or

[0047] The surface temperature of the heated cylinder is >110° C. and in particular in the range of 110° to approximately 125°, and / or

[0048] - the pre-treatment or heating zone extends over a range of approximately 30° and / or

[0049] - the constriction extends over a range of approximately 20°, and / or

[0050] - an average linear force of a maximum of 50 kN / m in the nip, which is arranged in the initial region of the zone of the heated cylinder surrounded by the fibrous web and the elastic band, viewed in the running direction of the web, and / or

[0051] The residence time of the fibrous web in the nip, which is arranged in the initial region of the zone of the heated cylinder surrounded by the fibrous web and the elastic band, as viewed in the running direction of the web, is approximately 0.1 seconds, and / or

[0052] The average linear force in the nip provided at the end of the pre-treatment or heating zone is a maximum of 50 kN / m.

[0053] The present invention will be described in more detail below based on embodiments with reference to the accompanying drawings; in the accompanying drawings:

[0054] Figure 1 A schematic diagram shows an exemplary embodiment of the machine according to the invention, which is particularly suitable for relatively low machine or web running speeds, preferably for machine or web running speeds of <1000 m / sec,

[0055] Figure 2 A schematic diagram shows a further exemplary embodiment of the machine according to the invention, which is suitable in particular for relatively high machine or web running speeds, preferably for machine or web running speeds of >1000 m / sec,

[0056] Figure 3 A schematic partial view of an exemplary tensioning roller of a machine according to the invention is shown in cross section.

[0057] Figure 4 A schematic partial view of an exemplary guide roller of a machine according to the invention is shown in cross section,

[0058] Figure 5 A schematic partial view shows an exemplary embodiment of an elastic band of a machine according to the invention, the elastic band having reinforcing threads extending in the transverse direction and reinforcing threads extending in the longitudinal direction,

[0059] Figure 6 Shows the relative Figure 5 exemplary course of the modulus of elasticity of the reinforcing threads arranged symmetrically along the central longitudinal axis of the belt,

[0060] Figure 7 A schematic partial view of an exemplary embodiment of an elastic belt with a thread layer of a machine according to the invention is shown,

[0061] Figure 8 The schematic course of the trough-shaped shrinkage curve of the fibrous web, which is usually produced in the transverse direction, is shown with a solid line and the schematic course of the shrinkage curve according to Figure 5 or Figure 7 The exemplary schematic extension direction of the stress characteristics or strain characteristics of the elastic band in the transverse direction, and

[0062] Figure 9 The dried fiber web or paper web or cardboard web is shown in the transverse direction through the Figure 5 or Figure 7 Schematic representation of the resulting shrinkage curve or strain characteristics.

[0063] Figure 1 or Figure 2 In each case, an exemplary embodiment of a machine 10 according to the invention is shown for producing a fibrous web 12 that can be stretched in the transverse direction, which can in particular be a paper or cardboard web that can be stretched in the transverse direction.

[0064] The machine 10 comprises a heated, water vapor-impermeable and smooth rotating cylinder 14 and a water vapor-impermeable, surrounding elastic belt 16 .

[0065] The fibrous web 12 is hereby respectively guided together with an elastic band 16 transversely past the heated cylinder 14 at a predetermined or predeterminable wrap angle between the elastic band 16 and the heated cylinder 14 and is pressed against the heated cylinder by the elastic band 16 .

[0066] The elastic bands 16 can be loaded with a variably adjustable and / or controllable preload in the transverse direction before coming into contact with the fibrous web 12. After the steam cushion is formed between the fibrous web 12 and the heated cylinder 14, the preload of the elastic bands 16 generated in the transverse direction can be reduced again, so that the fibrous web 12 slides on the heated cylinder 14 via the steam cushion and contracts in the transverse direction together with the elastic bands.

[0067] exist Figure 1 In the machine 10 shown, which is particularly designed for relatively low machine or web running speeds, preferably for machine or web running speeds of <1000 m / min, a steam cushion is generated between the fibrous web 12 and the heated cylinder 14 in a pressure zone 18, which is arranged in the starting area of ​​the area of ​​the heated cylinder 14 surrounded by the fibrous web 12 and the elastic band 16 as viewed in the web running direction I, and is formed between the heated cylinder 14 and a squeezing roller 20 arranged within the loop of the elastic band 16, which is simultaneously designed as a variably adjustable tensioning roller, by which the elastic band 16 can be pretensioned in the transverse direction.

[0068] In the rear region of the area of ​​the heated cylinder 14 surrounded by the fibrous web 12 and the elastic band 16 as viewed in the web running direction I, a guide roller 22 is provided within the loop of the elastic band 16 for holding the elastic band 16 and the fibrous web 12 on the heated cylinder 14, so that the preload force of the elastic band 16 generated in the transverse direction is reduced again between the pressing area 18 and the guide roller 22 for generating the transverse contraction of the fibrous web. The pressing area is provided in the initial region of the area of ​​the heated cylinder 14 surrounded by the fibrous web 12 and the elastic band 16 as viewed in the web running direction I, and the guide roller is provided in the rear region of the area of ​​the heated cylinder 14 surrounded by the fibrous web 12 and the elastic band 16 as viewed in the web running direction I.

[0069] The elastic band 16 is removed from the heated cylinder 14 again by guide rollers 22 and separated from the elastic band 16 , which are arranged in the rear region of the region of the heated cylinder 14 surrounded by the fibrous web 12 and the elastic band 16 as viewed in the web running direction I.

[0070] In accordance with Figure 2 In a machine 10 designed for relatively high machine or web running speeds, preferably for machine or web running speeds of >1000 m / min, the fibrous web 12 is first guided together with the pre-tensioned elastic band 16 along a pretreatment or heating zone α past a heated cylinder 14, so that a steam cushion is formed between the fibrous web 12 and the heated cylinder 14 when the elastic band 16 is held in a pre-tensioned manner.

[0071] Here, the elastic band 16 is fed to the fibrous web 12, which is brought into contact with the heated cylinder 14, via a variably adjustable tensioning roller 24 that preloads the fibrous web 12. A nip 26 is provided at the end of the pretreatment or heating zone α to improve the adhesion of the fibrous web 12 to the elastic band 16. This nip is formed between the heated cylinder 14 and a squeeze roller 28 arranged within the loop of the elastic band 16, which is also designed as a variably adjustable tensioning roller to maintain the preload of the elastic band 16 in the previous pretreatment or heating zone α. Following the nip 26 at the end of the pretreatment or heating zone α, the fibrous web 12 is guided further through the heated cylinder 14 together with the elastic band 16 along a contraction zone β, where the preload of the elastic band 16, which produces the transverse contraction of the fibrous web 12, is reduced again.

[0072] After the shrinkage zone β, the fibrous web 12 is fed together with the elastic band 16 to a guide roller 30 , by means of which the fibrous web 12 and the elastic band 16 are removed from the heated cylinder 14 again and separated from one another.

[0073] In accordance with Figure 1 and Figure 2 In both exemplary embodiments, the elastic band 16 can nevertheless be loaded by the corresponding guide rollers 22 , 30 with a basic stress that is less by a defined amount than the preload force.

[0074] Figure 3 The schematic partial view shows an exemplary embodiment of a tensioning roller A, which can also be used, for example, according to Figure 1 The roller 20, the tension roller 24 and the roller 20 designed as the squeeze roller are Figure 2 The squeeze roller 28 is also designed at the same time as a tensioning roller.

[0075] Depend on Figure 3 It is clear that, with such a tensioning roller A, the preload of the elastic band 16 can be adjusted by means of a tensioning body arranged laterally on the roller body and variably adjustable relative to the roller body 32 in the transverse direction of the machine.

[0076] and Figure 4 The schematic partial view shows a schematic embodiment of a guide roller B, which can be used, for example, according to Figure 1 The guide roller 22 and the Figure 2 Guide roller 30. According to Figure 4 It can be seen that for such a guide roller B, the elastic band 16 can still be loaded with a basic stress that is smaller than the preload force by a defined amount ΔL.

[0077] exist Figure 3 and Figure 4 The corresponding support structure 36 of the respective roller A or B can also be seen in FIG.

[0078] Figure 5 In a schematic partial view, an exemplary embodiment of an elastic band 16 of a machine according to the invention is shown, which has reinforcing threads 38 extending in the transverse direction CD and reinforcing threads 40 extending in the longitudinal direction MD. The reinforcing threads 38 extending in the transverse direction CD and arranged symmetrically with respect to the central longitudinal axis L are provided with a correspondingly adapted modulus of elasticity E in order to selectively influence the transverse strain of the fibrous web 12. The reinforcing threads 38 extending in the transverse direction CD of the elastic band 16 can be adapted accordingly in order to compensate, in particular, for the trough-shaped shrinkage curve 42 (cf. FIG. 4 ) that typically occurs in the transverse direction when the fibrous web 12 is dried. Figure 8 solid line in the figure).

[0079] Figure 6 Shows the relative Figure 5 Schematic progression of the modulus of elasticity E of the reinforcing threads extending in the transverse direction, arranged along the central longitudinal axis L of the elastic band 16 .

[0080] Figure 7 The schematic partial view shows an exemplary embodiment of an elastic band 16 of a machine 10 according to the invention having a thread layer 44 in which a desired profile can be achieved by means of a variable thread density for targeted influence of the transverse strain of the fibrous web. Figure 7 The thread density is high in the left part, medium in the middle, and Figure 7 The right part of the thread density is relatively low. This thread layer 44 can also be adapted accordingly to compensate for the trough-shaped shrinkage curve 42 that usually occurs in the transverse direction when drying the fibrous web 12, which is achieved in the present case in particular by a variable thread density.

[0081] As already mentioned, Figure 8 The schematic progression of the trough-shaped shrinkage curve 42 of the fibrous web 12, which is generally produced in the cross direction CD, is shown as a solid line. Figure 8 The dotted lines show the Figure 5 and Figure 7 In particular, the extension of the transverse strain ε of a conventionally dried fiber web 12 (see solid line 42) and the extension of the transverse strain ε of the elastic band in the transverse direction CD are shown. Figure 5 Hetong Figure 7 The extension direction of the transverse strain ε of the elastic band 16 (dash-dotted line 46).

[0082] Figure 9 It shows that the dried fiber web or paper web or cardboard web 12 can be processed according to Figure 5 and Figure 7The elastic band 16 realizes a compensating shrinkage curve 48 or strain behavior. The previously common trough-shaped structure is avoided here.

[0083] List of Reference Numerals

[0084] 10 Machine

[0085] 12 Fiber web

[0086] 14 Heated Column

[0087] 16 elastic bands

[0088] 18 Nip

[0089] 20 squeeze rollers

[0090] 22 guide rollers

[0091] 24 tension rollers

[0092] 26 Nip

[0093] 28 squeeze rollers

[0094] 30 guide rollers

[0095] 32 Roller

[0096] 34 tensioning head

[0097] 36 Support structure

[0098] 38 Reinforcement threads extending in the transverse direction

[0099] 40 Reinforcement threads extending longitudinally

[0100] 42 Contraction Curve

[0101] 44 silk thread layers

[0102] 46 CD strain of elastic band

[0103] 48 Contraction Curve

[0104] I Web running direction

[0105] A Tension roller

[0106] B guide roller

[0107] CD landscape

[0108] E elastic modulus

[0109] MD (longitudinal direction)

[0110] L Center longitudinal axis

[0111] Δ stress difference

[0112] α Pretreatment or heating zone

[0113] β contraction zone

[0114] ε Transverse strain

Claims

1. A method for producing a fiber web (12) that can be stretched in the transverse direction, in which method a fiber web (12) coming from a predrying section of an associated production machine (10) is brought into contact with a water vapor-impermeable and smoothly rotating heated cylinder (14) and, together with a water vapor-impermeable, surrounding elastic band (16), is guided transversely over the heated cylinder (14) at a predetermined or predeterminable wrap angle between the elastic band (16) and the heated cylinder (14) and is passed through the elastic band. (16) is pressed onto the heated cylinder, and before coming into contact with the fibrous web (12), the elastic band (16) is loaded with a preload force that can be variably adjusted and / or controlled in the transverse direction, and after a steam cushion is formed between the fibrous web (12) and the heated cylinder (14), the preload force of the elastic band (16) generated in the transverse direction is reduced again, so that the fibrous web (12) slides on the heated cylinder (14) through the steam cushion and shrinks in the transverse direction together with the elastic band (16).

2. The method according to claim 1, characterized in that The fibrous web is a paper web or a cardboard web.

3. The method according to claim 1, characterized in that A steel cylinder was used as the heated cylinder (14).

4. The method according to claim 3, characterized in that The steel cylinder is a chrome-plated steel cylinder.

5. The method according to any one of claims 1 to 4, characterized in that The elastic band (16) is pretensioned in the transverse direction by at least one variably adjustable tensioning roller (A, 20, 24, 28) arranged within the loop of the elastic band.

6. The method according to claim 5, characterized in that The prestressing force of the elastic belt (16) generated in the transverse direction is reduced again between a variably adjustable tensioning roller arranged within the loop of the elastic belt (16) and a guide roller (B, 22, 30) arranged within the loop of the elastic belt (16) as viewed in the web running direction (I).

7. The method according to any one of claims 1 to 4, characterized in that For relatively low machine running speeds or web running speeds of less than 1000 m / min, a steam cushion is generated between the fibrous web (12) and the heated cylinder (14) in a first pressure zone (18), the first pressure zone being arranged in the starting area of ​​the area of ​​the heated cylinder (14) surrounded by the fibrous web (12) and the elastic band (16) as viewed in the web running direction (I), the first pressure zone being formed between the heated cylinder (14) and a first squeezing roller (20) arranged within the loop of the elastic band (16), the first squeezing roller being simultaneously designed as a variably adjustable tensioning roller, by which the elastic band (16) is pre-tensioned in the transverse direction.

8. The method according to claim 7, characterized in that In the rear region of the heated cylinder (14) surrounded by the fibrous web (12) and the elastic band (16) as viewed in the web running direction (I), guide rollers (B, 22) are provided within the loop of the elastic band (16) for holding the elastic band (16) and the fibrous web (12) on the heated cylinder (14), so that the preload force of the elastic band (16) generated in the transverse direction is reduced again between a first pressing area (18) and the guide rollers (B, 22) for generating transverse contraction of the fibrous web (12), the first pressing area being provided in the initial region of the heated cylinder (14) surrounded by the fibrous web (12) and the elastic band (16) as viewed in the web running direction (I), and the guide rollers being provided in the rear region of the heated cylinder (14) surrounded by the fibrous web (12) and the elastic band (16) as viewed in the web running direction (I).

9. The method according to claim 8, characterized in that The elastic band (16) is removed from the heated cylinder (14) again by means of guide rollers (B, 22) and the fibrous web (12) is separated from the elastic band (16) again. The guide rollers are arranged in a rear region of the heated cylinder (14) of the area surrounded by the fibrous web (12) and the elastic band (16) as viewed in the web running direction (I).

10. The method according to any one of claims 1 to 4, characterized in that At relatively high machine or web speeds of >1000 m / min, the fibrous web (12) is first guided together with the pre-tensioned elastic band (16) through the heated cylinder (14) along a pretreatment or heating zone (α), so that a steam cushion is formed between the fibrous web (12) and the heated cylinder (14) while the elastic band (16) is held pre-tensioned.

11. The method according to claim 10, characterized in that The elastic band (16) is supplied to the fibrous web (12) in contact with the heated cylinder (14) by means of a variably adjustable tensioning roller which pre-tensions the fibrous web (12) and a second pressing zone (26) is provided at the end of the pre-treatment or heating zone (α) to improve the adhesion of the fibrous web (12) to the elastic band (16), the second pressing zone being formed between the heated cylinder (14) and a second squeezing roller (28) arranged in the loop of the elastic band (16), the second squeezing roller At the same time, a variably adjustable tensioning roller is designed to maintain the preload of the elastic band (16) in the preceding pretreatment or heating zone (α), and the fibrous web (12) is guided together with the elastic band (16) along the contraction zone (β) through the heated cylinder (14) after a second pressing zone (26) arranged at the end of the pretreatment or heating zone (α), and the preload of the elastic band (16) for producing the transverse contraction of the fibrous web (12) is reduced again along the contraction zone.

12. The method according to claim 11, characterized in that After the shrinkage zone (β), the fibrous web (12) is fed together with the elastic band (16) to a guide roller (B, 30), by which the fibrous web (12) and the elastic band (16) are removed from the heated cylinder (14) and separated from each other.

13. The method according to any one of claims 1 to 4, characterized in that The elastic band (16) is still loaded via corresponding guide rollers (B, 22, 30) with a basic stress which is smaller by a defined amount (ΔL) than the preload force.

14. A machine (10) for producing a fibrous web (12) stretchable in the transverse direction, the machine being adapted to carry out the method according to one of the preceding claims, comprising a water vapor-impermeable and smooth rotating heated cylinder (14) and a water vapor-impermeable, surrounding elastic belt (16), wherein: The fibrous web (12) and the elastic band (16) are jointly guided transversely through the heated cylinder (14) at a predetermined or predeterminable wrap angle between the elastic band (16) and the heated cylinder (14) and are pressed onto the heated cylinder (14) by the elastic band (16); before contacting the fibrous web (12), the elastic band (16) can be loaded with a preload force that can be variably adjusted and / or controlled in the transverse direction; and after a steam cushion is formed between the fibrous web (12) and the heated cylinder (14), the preload force of the elastic band (16) generated in the transverse direction can be reduced again, so that the fibrous web (12) slides on the heated cylinder (14) through the steam cushion and contracts in the transverse direction together with the elastic band (16).

15. The machine according to claim 14, characterized in that The fibrous web is a paper web or a cardboard web.

16. Machine according to claim 14 or 15, characterized in that For relatively low machine or web running speeds of <1000 m / min, a steam cushion is generated between the fibrous web (12) and the heated cylinder (14) in a first pressure zone (18), the first pressure zone being arranged in a starting area of ​​the heated cylinder (14) surrounded by the fibrous web (12) and the elastic band (16) as viewed in the web running direction (I), the first pressure zone being formed between the heated cylinder (14) and a first squeezing roller (20) arranged within the loop of the elastic band (16), the first squeezing roller being simultaneously designed as a variably adjustable tensioning roller, by which the elastic band (16) can be pre-tensioned in the transverse direction.

17. The machine according to claim 14 or 15, characterized in that For relatively high machine or web running speeds of >1000 m / min, the fibrous web (12) is first guided together with the pre-tensioned elastic band (16) through the heated cylinder (14) along a pre-treatment or heating zone (α), so that a steam cushion is formed between the fibrous web (12) and the heated cylinder (14) when the elastic band (16) is held pre-tensioned, and / or the elastic band (16) can be fed to the fibrous web (12) in contact with the heated cylinder (14) by means of a variably adjustable tensioning roller which pre-tensions the fibrous web (12), and a second pressing zone (26) is provided at the end of the pre-treatment or heating zone (α) to increase the pressure of the fibrous web (12) in the pre-treatment or heating zone (α). The elastic band (16) is attached to the elastic band (16), the second pressure zone is formed between the heated cylinder (14) and a second squeezing roller (28) arranged in the loop of the elastic band (16), the second squeezing roller is also designed as a variably adjustable tensioning roller for maintaining the preload of the elastic band (16) in the preceding pretreatment or heating zone (α), and the fiber web (12) is continued to be guided through the heated cylinder (14) together with the elastic band (16) along the contraction zone (β) after the second pressure zone (26) arranged at the end of the pretreatment or heating zone (α), and the preload of the elastic band (16) for producing the transverse contraction of the fiber web (12) is reduced again along the contraction zone.

18. Machine according to claim 14 or 15, characterized in that The elastic band (16) is provided with reinforcing threads (38) or thread layers (44) extending in the transverse direction (CD) and having a correspondingly adapted modulus of elasticity (E), thereby influencing the transverse stretching of the fibrous web (12) symmetrically with respect to a central longitudinal axis (L) of the elastic band (16) parallel to the machine direction (MD).

19. The machine according to claim 18, characterized in that The thread layers are thread layers that are adapted accordingly with regard to their thread density.

20. Machine according to claim 14 or 15, characterized in that The dry weight content of the fibrous web (12) supplied to the heated cylinder (14) is in the range of 50% to 65%, and / or The heatable cylinder (14) has a diameter in the range of 900 mm to 1500 mm, and / or The surface temperature of the heated column (14) is greater than 110°C, and / or The pre-treatment or heating zone (α) extends over 30° and / or The contraction zone (β) extends over 20°, and / or The average linear force in the first pressing zone (18) is at most 50 kN / m, the first pressing zone being arranged in the starting area of ​​the zone of the heated cylinder (14) surrounded by the fibrous web (12) and the elastic band (16), viewed in the web running direction (I), and / or The residence time of the fibrous web (12) in the first pressing zone (18) is 0.1 seconds, the first pressing zone being arranged in the starting area of ​​the zone of the heated cylinder (14) surrounded by the fibrous web (12) and the elastic band (16) as viewed in the web running direction (I), and / or The average linear force in the second nip (26) arranged at the end of the pre-treatment or heating zone (α) is a maximum of 50 kN / m.

21. Machine according to the preceding claim 20, characterised in that The surface temperature of the heated cylinder (14) is in the range of 110° to 125°.

Images