Roll arrangement for compressing a fibrous-material web

Abstract

The present invention relates to a roll arrangement for producing a compressed fibrous-material web (12) using a compression press (10) which comprises at least a compression roll (14) and a mating roll (16) and a feed roll (30) and which is designed to compress the fibrous-material web in a direction transverse to a conveying direction (CD) and / or in the conveying direction (MD) of the fibrous-material web (12), wherein a resilient tensioning web (18) that receives the fibrous-material web (12) is provided and is guided through a nip (17) between the compression roll (14) and the mating roll (16) and over the compression roll (14). The resilient tensioning web (18) is also guided through a nip (31) between the feed roll (30) and the mating roll (16) and over the feed roll (30), wherein the nip between the feed roll (30) and the mating roll (16), viewed in the circumferential direction of the mating roll (16), is arranged upstream of the nip (17) formed by the compression roll (14) and the mating roll (16), viewed in the conveying direction (MD). The present invention also relates to a corresponding production method. According to the invention, the feed roll (30) has a resilient lateral surface (36) over its circumference.

Description

[0001] Roller arrangement for compressing a fibrous web

[0002] The invention relates to a roller arrangement for producing a compressed fibrous web using a compression press. The compression press comprises at least one compression roller, a counter roller, and a feed roller and is designed to compress the fibrous web in a direction transverse to a conveying direction and / or in a conveying direction of the fibrous web.

[0003] Such a roll arrangement is used in a paper machine to generate controlled transverse shrinkage in a plane spanned by the fibrous web in a direction transverse to the conveying direction of the fibrous web using the compression press. Controlling the transverse shrinkage of the fibrous web is particularly desirable because, while previously known processes allow for the desired longitudinal shrinkage of the fibrous web or a change in length in the conveying direction of the fibrous web to be specifically influenced by suitable measures or processes (e.g., the Clupak process), the transverse shrinkage or change in width of the fibrous web is always a rather random and thus hardly or even not at all controllable consequence of the subsequent drying process.With the current processes, a longitudinal shrinkage of 15 to 17% is possible at a dry content of 60 to 70%, whereby these processes are mainly used for fibrous webs with a basis weight of 60 to 70 g / m. 2 or slightly above are applicable.

[0004] To transversely shrink the fibrous web in the compression press, axial forces directed inward in opposite directions act in a nip formed by the compression roller and the counterroller, parallel to the longitudinal axes of the compression roller and counterroller. These axial forces are transferred to the fibrous web to compress the fibrous web in the plane of the fibrous web, transverse to the conveying direction. The longitudinal axes of the compression roller and the counterroller, as well as the longitudinal extent of the nip, are aligned parallel to the plane of the fibrous web and transverse to the conveying direction of the fibrous web. In principle, with a suitable press design, outward "shrinkage" and / or local transverse shrinkage are also possible. For example, one possible embodiment of such a compression roller is disclosed in WO 2021 / 254 732 A1.

[0005] During transverse shrinkage of the fibrous web, the fibrous web is compressed across its width, i.e., across its longitudinal extent in the conveying direction, in the plane of the fibrous web, preferably without creping the fibrous web. At the same time, the compressed fibrous web remains stretchable across its width.

[0006] Stretchable fiber materials, especially fiber materials that can be stretched both longitudinally and transversely, such as stretchable paper or cardboard, serve, for example, as starting materials for the production of shaped articles, such as plates produced by a pressing and / or deep-drawing process or the like. Furthermore, stretchable fiber materials are used in fiber packaging where elastic properties are desired, such as sack paper for use in sacks. For such products, paper or cardboard made from a stretchable fiber web with the highest possible elongation at break is of great importance.

[0007] While the methods known to date already offer suitable solutions for producing a fibrous web with satisfactory longitudinal extensibility and the highest possible elongation at break, producing a fibrous web with sufficient lateral extensibility, in particular accompanied by the highest possible elongation at break in the transverse direction CD, still represents a major challenge. A roller arrangement for compressing a fibrous web with an elastic tensioning web is disclosed, for example, in document DE 10 2021 118 165 A1 or document DE 10 2020 114 602 A1, whereby the production of a fibrous web that is stretchable both in the conveying direction and transversely thereto in the plane of the fibrous web can be enabled. With the roller arrangements, the focus is on compression transverse to the conveying direction, and uniform compression both in the conveying direction and transversely thereto should also be enabled.

[0008] The disadvantage of the proposed roller arrangements is that a uniform compression in both directions is only possible at low compression values, for example less than 5%, and at higher compression values ​​in the transverse direction CD, too little compression is achieved in the conveying direction MD in the fibrous web, and thus a uniform high compression cannot be achieved.

[0009] In some cases, it is possible to compensate for the under-compression values ​​with a separate, upstream, known compression device in the MD conveying direction. However, this has the disadvantage that coordinating the two separate compression devices is complex, and the operating and investment costs for a more complex arrangement are higher. A particularly disadvantageous aspect, however, is that the quality of the compressed fibrous web in terms of uniformity is still not sufficient in a split compression device, and unwanted web breaks and / or further wrinkles can occur during the transfer between the separate compression devices.

[0010] One object of the invention is to provide an improved roller arrangement for producing a fibrous web that is uniformly stretchable or compressible in the conveying or longitudinal direction (MD) and the transverse direction (CD) of the fibrous web plane. Furthermore, an improved, compact roller arrangement is to be created that simultaneously enables a uniformly high compression in the conveying direction MD while achieving high compression values ​​in the transverse direction CD in the fibrous web plane.

[0011] The objects are achieved with a roller arrangement for producing a compressed fibrous web with a compression press which comprises at least one compression roller and one counter roller and one feed roller and which is designed to produce a compression of the fibrous web in a direction transverse to a conveying direction and / or in a conveying direction of the fibrous web, wherein an elastic tensioning web receiving the fibrous web is provided, and wherein the elastic tensioning web is guided through a nip, preferably compression nip, between the compression roller and the counter roller and over the compression roller, and wherein the elastic tensioning web is guided through a nip, preferably feed nip, between the feed roller and the counter roller, and wherein the nip, preferably feed nip, between the feed roller and the counter roller, viewed in the circumferential direction of the counter roller, corresponds to the nip, preferably compression nip, formed by the compression roller and the counter roller.viewed in the conveying direction, wherein according to the invention the feed roller comprises an elastic outer surface over its circumference.

[0012] The inventors have discovered through tests that the shrinkage or compression introduced into the fibrous web by the known roller arrangement in the conveying direction as well as the transverse direction, or MD and CD directions, can be improved or further increased if the feed roller arranged within the elastic tensioning web is designed with an elastic outer surface, whereby a further increase in the controlled compression in the conveying direction MD can be achieved in the fibrous web by the soft, elastic outer surface. To define an "elastic outer surface", in particular of an elastic roller cover, a modulus of elasticity (E-modulus) can be specified. However, a hardness, e.g. in ShoreA, is usually specified as equivalent to elasticity instead of a modulus of elasticity (E-modulus).

[0013] An “elastic surface” or an elastic material is usually considered to have a hardness of less than or equal to 100 ShA, in particular 95 ShA, preferably less than 90 ShA.

[0014] The combination of the elastic tensioning layer and the elastic surface in the feed nip has a particularly beneficial effect on compression in the MD conveying direction. This combination allows the maximum acceleration of the fibrous web in the feed nip to be further increased and the thickness of the elastic layer to be increased beyond the previously implemented variants.

[0015] The roller arrangement modified according to the invention can specifically introduce the high compression values ​​into the fibrous web in the transverse (CD) and conveying direction (MD); further advantageously, the roller arrangement according to the invention is compactly combined in a single roller arrangement.

[0016] Advantageously, the quality can be further increased with regard to the uniformity of the applied compression in MD and CD.

[0017] Another advantage is that a second, separate upsetting device can be dispensed with, which can have the advantage of reducing complexity and costs.

[0018] Furthermore, the combination of both compression directions in a single, compact roller arrangement can advantageously achieve an increased maximum compression of the fibrous web, particularly compared to a variant divided into two separate compression devices. The shrinkage values ​​or compression values ​​achievable in the conveying and transverse directions are preferably in a range of 6 to 40%, particularly preferably in a range of 20 to 30%. The elastic outer surface advantageously results in a second control means for adjusting the compression in the conveying direction, wherein the elastic tensioning web also makes an important contribution to compression in the conveying direction, but can be optimized for compression in the transverse direction CD in the following compression nip.

[0019] In an alternative embodiment, the roller arrangement is characterized in that the elastic outer surface is designed as an elastic coating or a replaceable, elastic roller cover.

[0020] Furthermore, the elastic coating or the replaceable, elastic roller cover can consist essentially of a plastic or a polymer. The plastic is preferably an elastomer, particularly preferably a rubber or polyurethane.

[0021] The feed roller can be constructed in two parts, with the feed roller consisting of a hard roller core and an elastic coating or elastic roller cover. A hard roller core can be formed, for example, from a metal, stone, or fiber composite material.

[0022] An elastic coating is defined as a firmly bonded elastic material to the core. The elastic material is softer than the core material and is bonded to the core material, for example, with an adhesive. Alternatively, the elastic material of the elastic coating can also be bonded to the core material using an additive manufacturing process, a casting process, or another application process. The coating can wear out, in which case the feed roller with the elastic coating in the roller assembly is replaced, and the feed roller can be recoated using downstream processes.Advantageously, a replaceable, elastic roller cover can be replaced in the event of wear on the elastic surface of the feed roller in a cost- and time-optimized manner compared to an elastic coating, since the elastic roller cover can be exchangeably connected to the roller core of the feed roller, thus a roller cover in or on the machine can be replaced very easily.

[0023] In an alternative embodiment, the roller arrangement is characterized in that the elastic outer surface of the feed roller has a hardness of 20 to 65 ShA, preferably of 25 to 60 ShA and for example of 30 to 55 ShA.

[0024] Advantageously, the compression of the fibrous web is further improved with a softer elastic surface below 65 ShA, but the elastic surface must not become too soft, as this can have negative effects on the fibrous web guidance and a reduction in the compression values.

[0025] In an alternative embodiment, the roller arrangement is characterized in that the elastic outer surface has a thickness of greater than or equal to 4 mm, in particular greater than or equal to 10 mm, preferably greater than or equal to 20 mm, and less than or equal to 60 mm, in particular less than or equal to 40 mm, preferably less than or equal to 30 mm.

[0026] Advantageously, the compression of the fibrous web can be positively influenced by an increased thickness of the elastic surface, but the thickness must not be chosen too thick, as this can have negative effects on the fibrous web guidance and a reduction in the compression values.

[0027] In an alternative embodiment, the roller arrangement is characterized in that the elastic outer surface of the feed roller has a thickness of greater than or equal to 10 mm, preferably greater than or equal to 20 mm, and less than or equal to 40 mm, preferably less than or equal to 30 mm, and in that the elastic tensioning web guided over the feed roller has a thickness of greater than or equal to 4 mm, preferably greater than or equal to 10 mm, and less than or equal to 30 mm, preferably less than or equal to 20 mm.

[0028] Advantageously, the thickness of the elastic shell surface and the thickness of the elastic tensioning web are matched to each other for optimal compression in the conveying direction MD in the feed nip and can thus result in increased compression of the fibrous web.

[0029] It is advantageous if the thickness of the elastic surface is equal to or greater than the thickness of the elastic tensioning strip. For example, a combination of a surface thickness of 10 mm and a tensioning strip thickness of 4 mm (total 14 mm) up to a surface thickness of 40 mm and a tensioning strip thickness of 30 mm (total 70 mm) is conceivable. This combination of tensioning strip thickness and surface thickness has a positive influence on compression in the conveying direction MD.

[0030] In an alternative embodiment, the roller arrangement is characterized in that the elastic outer surface has a structuring, in particular on a side facing the fibrous web to be conveyed.

[0031] Advantageously, the force transmission into the elastic tensioning track can be increased by structuring the elastic shell surface; this has a particularly positive effect on moments to be transmitted, as can occur with an actively driven feed roller.

[0032] In addition, the structuring due to the moment transferred to the compression web also affects the fibrous web and results in increased compression in the conveying direction.

[0033] In an alternative embodiment, the roller arrangement is characterized in that the feed roller is arranged immediately upstream of the nip formed by the compression roller and the counter roller, in particular less than or equal to 90°, preferably less than or equal to 60°, and in particular greater than or equal to 15°. Advantageously, in the proposed roller arrangement, two usually separate units for compression in the conveying direction MD and the transverse direction CD can be combined into a single unit or roller arrangement. For a very compact design and the lowest possible loss of compression introduced in the feed nip in the conveying direction MD, it is advantageous to arrange the feed roller immediately upstream of the subsequent compression nip, so that the transfer distance of the fibrous web between the feed nip and the compression nip is set as short as possible.

[0034] In an alternative embodiment, the roller arrangement is characterized in that the feed roller comprises a controllable drive, wherein the drive is suitable for driving and / or braking the feed roller.

[0035] Preferably, the feed roller can be connected to a controllable drive, which advantageously makes it possible to control the rotational speed of the feed roller, in particular the compression in the conveying direction MD can be influenced by adjusting the rotational speed.

[0036] The difference in the surface speeds between the preferably driven counter roll, the elastic tensioning track and the feed roll with elastic jacket has an effect on the compression introduced in the conveying direction MD. Surprisingly, it has been shown that a slight increase or decrease in comparison to the surface speed of the counter roll can have a positive effect on the compression in the conveying direction MD.

[0037] In an alternative embodiment, the roller arrangement is characterized in that the feed roller is arranged between at least one spreader roller or at least one spreader element and the counter roller, in particular immediately after the spreader roller, and in that the spreader roller has a crown of greater than or equal to 1% and less than or equal to 5% of its extension transverse to the conveying direction.In an alternative embodiment, the roller arrangement is characterized in that the compression roller has a rotationally symmetrical base body which is rotatable about a longitudinal axis and has a lateral surface on which at least two elastically deformable and / or deflectable annular lamellae are arranged, which extend in the radial direction away from the lateral surface and which surround the base body in the circumferential direction, in particular wherein the lamellae are inclined in pairs in a mirror-symmetrical manner in the direction of the center plane of the compression roller, forming an angle of inclination obliquely to a center plane of the compression roller which is oriented perpendicular to the longitudinal axis of the compression roller.

[0038] In an alternative embodiment, the roller arrangement is characterized in that several compression rollers are assigned to the counter roller and each form a nip with the counter roller.

[0039] The invention is based on the general idea of ​​uniformly supporting a fibrous web during its conveyance through the nip between the compression roll and the counter roll by means of a tensioning web. This support transfers part of the web tension generated by the roll arrangement or the paper machine to the tensioning web, thus reducing the proportion of web tension acting on the fibrous web. Reducing the web tension acting on the fibrous web has the advantage of increasing the elongation at break of the fibrous web, resulting in greater extensibility.

[0040] Furthermore, by guiding the tensioning web over the compression roller, the tensioning web separates the fibrous web to be conveyed from the compression roller, preventing the fibrous web from coming into direct contact with the compression roller. The additional support of the fibrous web has the advantage that the transverse forces generated by the compression roller, in particular in the compression nip, do not act directly on the fibrous web, but indirectly via the tensioning web. As a result, the forces acting in the compression nip are gently transferred to the fibrous web by means of the tensioning web, thus preventing undesirable wrinkling in the fibrous web or, in the worst case, damage to the fibrous web.

[0041] A further advantage of the invention is that the roller arrangement, by supporting the fibrous web, can be used for heavier fibrous webs than previously possible. It has been demonstrated that, for example, a controlled transverse shrinkage of 10 to 30% relative to the initial width of the fibrous web before the roller arrangement is possible for fibrous webs with a basis weight of 70 to 200 g / m 2 and have a dry matter content of 55 to 90%.

[0042] Advantageous embodiments of the invention can be found in the dependent claims, the description and the accompanying drawings.

[0043] Preferred dry contents of the fibrous web at which the roller arrangement can be used can be between 55 and 58%, between 60 and 65% or between 66 and 70%.

[0044] In order for the tensioning web to be able to stretch transversely to the conveying direction, preferably essentially only in a plane of the tensioning web spanned by the tensioning web, it is advantageous if the tensioning web is more elastic in the tensioning web plane in the direction transverse to the conveying direction, i.e. has a lower modulus of elasticity, than in the conveying direction. For this purpose, the tensioning web can have at least one reinforcing means extending in the conveying direction, which has a lower elasticity, i.e. a higher modulus of elasticity, than the tensioning band. The reinforcing means serves in particular to prevent undesired distortions of the fibrous web to be conveyed. The reinforcing means is preferably in the form of a reinforcing band. The reinforcing band can, for example, be flat or have a round cross-section.

[0045] Adequate support of the fibrous web combined with good stretchability of the tensioning web can be achieved for tensioning web widths of less than or equal to 1 m if the tensioning web has a hardness of 20 to 65 ShA, preferably 25 to 60 ShA, and particularly preferably 30 to 55 ShA. For tensioning webs with a tensioning web width of greater than or equal to 1 m, a hardness of 30 to 65 ShA, preferably 35 to 60 ShA, and particularly preferably 40 to 55 ShA has proven advantageous.

[0046] To increase the adhesion between the tensioning web and the fibrous web and / or to influence or shape the surface of the fibrous web, the tensioning web can have a structure. The structure is preferably formed on a side facing the fibrous web to be conveyed.

[0047] To stretch the tensioning web in the tensioning web plane in a direction transverse to the conveying direction, at least one, in particular two, preferably three, preferably four, spreader roller(s) can be provided, by means of which the tensioning web can be pre-tensioned in a direction transverse to the conveying direction of the tensioning web against a restoring force of the tensioning web before the fibrous web is taken up. In other words, the spreader roller serves to pre-tension the tensioning web in the tensioning web plane in a direction transverse to the conveying direction before the fibrous web is taken up by expanding the width of the tensioning web in the tensioning web plane in a direction transverse to the conveying direction. Preferably, a pre-stretch of the tensioning web of 10 to 15% relative to its relaxed initial width can be achieved with just one spreader roller. Such pre-stretching can be achieved, for example, with a cambered spreader roller.In an alternative embodiment of the invention, it is conceivable that another spreading element, such as a spreading brush or a spreading bar, is used instead of the spreading roller. Preferably, two, three, or four spreading elements can also be provided.

[0048] Advantageously, a spreader brush is a very simple design and at the same time has a positive effect on the surface of the tensioning track.

[0049] Advantageously, a spreader bar is a very cost-effective version of a spreader element.

[0050] For an even greater pre-stretching of the tensioning web, several spreader rollers, for example two, three or four spreader rollers, can be arranged one behind the other to form a so-called spreader system.

[0051] Advantageously, several, in particular two, in particular three, or in particular four, spreading elements, for example a spreading brush or a spreading bar, can also form a spreading device.

[0052] A feed roller is provided which, together with the counter roller, forms a nip which, viewed in the circumferential direction of the counter roller, is positioned upstream of the nip formed by the compression roller and the counter roller in the conveying direction. According to a particularly preferred embodiment of the roller arrangement, the feed nip is positioned upstream of the compression nip by at least 15° - viewed in the circumferential direction of the counter roller - in the conveying direction. According to one embodiment, the tensioning web and the fibrous web come into contact with one another here. The line load in the feed nip can be adjusted as needed to achieve the desired adhesion between the tensioning web and the fibrous web. Analogous to the situation in the compression nip, the distance between the feed roller and the counter roller narrows down to the middle of the feed nip, where the distance between the feed roller and the counter roller reaches a minimum.Due to the constriction between the rollers, the Venturi effect occurs, so that the tensioning web and ultimately the fiber web conveyed by the tensioning web are initially accelerated due to the constriction and then decelerated due to the widening behind the center of the feed nip. This ultimately compresses the fiber web in the conveying direction. Such compression in the conveying direction leads to an increase in the elongation at break in the conveying direction of 6 to 8%.

[0053] In other words, the nip between the feed roller and the counter roller additionally enables the use of the Venturi effect to achieve additional compression of the fiber web in the conveying direction.

[0054] In order to ensure that the acceleration of the tensioning web or the fiber web to be conveyed in the constriction of the nip is not too great, it is advantageous if the tensioning web has a thickness between 2 and 30 mm and preferably between 4 and 26 mm.

[0055] Preferably, the thickness of the tensioning membrane for tensioning membranes with tensioning membrane widths of less than or equal to 1 m is between 4 and 6 mm, whereas for tensioning membranes with tensioning membrane widths of greater than or equal to 1 m, the thickness of the tensioning membrane can be between 4 and 26 mm.

[0056] By advancing the contact between the fibrous web and the tensioning web by means of the feed roller, it is possible for the tensioning web and the fibrous web to be conveyed along the counter roller for a certain time before the tensioning web and the fibrous web reach the compression nip. If one, two, three or four spreader rollers or such a rolling mill are provided, the feed roller can be arranged between the spreader roller and the counter roller in such a way that the pre-stretching of the tensioning web is essentially maintained. A particularly low loss of pre-stretching can be achieved by arranging the feed roller immediately or shortly after the, preferably last, spreader roller. In this context, "immediately" means that any pre-stretching of the tensioning web generated by the spreader roller does not decrease or does not decrease significantly upon reaching the feed roller.

[0057] To separate the fibrous web and the tensioning web after the compression nip, a deflection roller can be provided which is located downstream of the compression press as seen in the conveying direction of the tensioning web and which guides the tensioning web away from the fibrous web to be conveyed.

[0058] According to an advantageous embodiment, the deflection roller is arranged such that the tensioning web is guided over an angular section that is parallel to the counter roller. At high fibrous web speeds, it may be advantageous to increase the contact time between the tensioning web and the fibrous web, as this also leads to an increase in compression.

[0059] However, it is also possible for the deflection roller to be arranged in such a way that the tensioning web is not guided over the counter roller, but rather over an angled section of the compression roller. This allows the fibrous web to leave the tensioning web directly or relatively shortly after the compression nip, which is particularly advantageous at relatively low conveying speeds.

[0060] The deflection roller can be designed to be movable, allowing the guidance of the fibrous web along a partial circumference of the compression roller and / or the counter roller to be selectively changed. By changing the position of the deflection roller, for example, the angular range in which the tensioning web rests against the corresponding roller can be adjusted as needed.

[0061] To adjust a suitable pre-tension of the tensioning track in the conveying direction, a movable tensioning roller is preferably provided.

[0062] To facilitate the sliding of the fibrous web on the counter roll, the counter roll can have a smooth and / or perforated outer surface. Alternatively or additionally, the counter roll can also have a porous outer surface. If the counter roll has an perforated or porous outer surface, compressed air or steam can be passed, in particular pressed, through the openings or the porous outer surface, which facilitates the sliding of the fibrous web along the counter roll. A non-stick coating can be provided - additionally or alternatively. This also applies to, among other things, the feed and / or deflection roller(s).

[0063] According to a particularly preferred embodiment, the compression roller has a rotationally symmetrical base body rotatable about a longitudinal axis with a lateral surface on which at least two elastically deformable and / or deflectable annular lamellae are arranged, which extend radially away from the lateral surface and which surround the base body in the circumferential direction. For particularly uniform compression of the fibrous web in the direction transverse to the conveying direction in the fibrous web plane, the lamellae can be inclined in pairs in a mirror-symmetrical manner towards the center plane of the compression roller, forming an angle of inclination obliquely to a center plane of the compression roller oriented perpendicular to the longitudinal axis of the compression roller. The lamellae can be formed on a roller cover which is drawn over the base body of the compression roller. Other embodiments of the compression roller or the corresponding roller cover are possible.Preferably, a distance between the compression roller and the counter roller is adjustable. By varying the distance between the compression roller and the counter roller, different levels of pressure can be exerted on the lamellae of the compression roller in the compression nip. The greater the pressure acting on the lamellae in the nip, i.e., the smaller the distance between the longitudinal axes of the compression roller and the counter roller, the greater the deflection of the lamellae. A greater deflection of the lamellae in the nip toward the center plane is equivalent to a greater compression of the fibrous web in the fibrous plane in the direction transverse to the conveying direction.

[0064] Furthermore, the deflection of the slats also depends on their angle of inclination and the material properties of the slat material. The more inclined the slats are, the easier they are to deflect toward the center plane. Furthermore, easier deflection of the slats is achieved with softer materials.

[0065] For a particularly efficient compression of the fibrous web in the fibrous material plane in the direction transverse to the conveying direction, it is advantageously achieved that several compression rollers are assigned to the counter roller, which each form a compression nip with the counter roller.

[0066] The invention also relates to a method for producing a compressed fibrous web, in particular using a roller arrangement as described above. It comprises at least the following steps:

[0067] Combining a fibrous web with a tensioning web, which receives the fibrous web for conveying the fibrous web in a conveying direction; conveying the tensioning web together with the fibrous web to a compression press, which comprises at least one compression roller, a counter roller and a feed roller and which is designed to produce compression of the fibrous web in a direction transverse to the conveying direction and / or in the conveying direction in a fibrous web plane; and

[0068] Guiding the tensioning web together with the fibrous web through a nip formed between a feed roller and the counter roller, preferably a feed nip, and over the feed roller in order to compress the fibrous web in the conveying direction in the fibrous web plane; and

[0069] Guiding the tensioning web together with the fibrous web through a nip formed between the compression roller and the counter roller and over the compression roller in order to compress the fibrous web transversely to the conveying direction in the fibrous web plane.

[0070] The method according to the invention is characterized in that the feed roller comprises an elastic outer surface such that the compression of the fibrous web in the conveying direction is essentially generated by the elastic outer surface and the elastic compression path in the nip between the feed roller and the counter roller.

[0071] The invention is explained below purely by way of example using advantageous embodiments with reference to the accompanying drawings. They show:

[0072] Fig. 1 is a schematic view of a roller arrangement with a spreader roller;

[0073] Fig. 2 shows a detail of the schematic view of the roller arrangement of Fig. 1 with several, preferably three, spreader rollers;

[0074] Fig. 3 shows an upsetting roller of the roller arrangement of Fig. 1;

[0075] Fig. 4a is a plan view of a section of a tensioning track of a roller arrangement of Fig. 1; and Fig. 4b is a perspective view of a section of the tensioning track of Fig. 4a;

[0076] Fig. 5a shows a detail of the roller arrangement of Fig. 1 with a deflection roller in a first position;

[0077] Fig. 5b the deflection roller of Fig. 5a in a second position;

[0078] Fig. 6 is a schematic detailed view of a further development of the roller arrangement of Fig. 1; and

[0079] Fig. 7 is a further schematic detailed view of a further development of the roller arrangement of Fig. 1 .

[0080] The drawings illustrate various aspects of a roller arrangement for producing a compressed fibrous web. Specifically, Fig. 1 shows a roller arrangement that forms a basic embodiment for the further embodiments illustrated in Figs. 2, 5b, 6, and 7. Figs. 3, 4a and 4b, and 5a and 5b each show detailed aspects of the roller arrangement that can be used in all of the illustrated embodiments.

[0081] In the following, a roller arrangement will be explained in more detail with reference to the first embodiment shown in Fig. 1, with reference also being made to the remaining drawings.

[0082] The roller arrangement comprises an upsetting press 10 for producing an upsetting of a fibrous web 12 in a fibrous web plane in a direction transverse to the conveying direction of the fibrous web 12. In the drawings, the conveying direction is marked with the arrow MD and the transverse direction with the arrow CD (see in particular Fig. 4a and 4b).

[0083] The compression press 10 comprises a compression roll 14 and a counter roll 16 assigned to the compression roll 14. The compression roll 14 and the counter roll 16 together form a nip 17 (compression nip 17), through which an elastic tensioning web 18 receiving the fibrous web 12 is guided over the compression roll 14 in order to effect a transverse compression of the fibrous web 12 in the fibrous web plane in the direction transverse to the conveying direction MD in the compression nip 17. The tensioning web 18 serves to evenly support the fibrous web 12 during compression of the fibrous web 12. The support of the fibrous web 12 by the tensioning web 18 ensures that only a small part of the web tension generated by the roll arrangement or the paper machine is transferred to the fibrous web 12, since the other part of the web tension is transferred to the tensioning web 18. This allows the elongation at break and thus also the extensibility of the fibrous web 12 to be increased.

[0084] The compression roller 14 has a rotationally symmetrical base body 20 rotatable about a longitudinal axis L, having a lateral surface 22 on which at least two elastically deformable and / or deflectable annular lamellae 24 are arranged, which extend radially away from the lateral surface 22 and surround the base body 20 in the circumferential direction (Fig. 3). In the exemplary embodiment shown in Fig. 3, several lamellae 24 are inclined in pairs in a mirror-symmetrical manner in the direction of a central plane E of the compression roller 14, forming an angle of inclination, wherein the central plane E is oriented perpendicular to the longitudinal axis L of the compression roller 14.

[0085] By exerting pressure on the slats 24 (generated by the counter roll 16), the slats 24 are deflected in the direction of the center plane E of the compression roll 14. If the distance between the compression roll 14 and the counter roll 16 is adjustable, in particular by changing the distance between the respective longitudinal axes L of the compression roll 14 and the counter roll 16, the pressure acting on the slats 24 can also be varied. The smaller the distance between the compression roll 14 and the counter roll 16, the more the slats 24 are deflected in the compression nip 17. The slats 24 are compressed in the compression nip 17, i.e. deflected in the direction of the center plane E of the compression roll 14, and then move back to their original position. When the slats 24 are compressed due to their design, they generate inwardly directed transverse forces, by which the tensioning track 18 is directly or indirectly compressed.The fibrous web 12 conveyed by the tensioning web 18 is indirectly compressed in the transverse direction during its feed to the compression nip 17. For an even greater compression of the tensioning web 18 or the fibrous web 12 conveyed by the tensioning web 18, several compression rollers 14 can be assigned to the counter roller 16, each of which forms a compression nip 17 with the counter roller 16 (Figs. 6 and 7).

[0086] The tensioning web 18 separates the fibrous web 12 to be conveyed from the compression roller 14, so that the fibrous web 12 does not come into direct contact with the lamellae 24 of the compression roller 14. As a result, transverse forces occurring in the compression nip 17 are not transferred directly to the fibrous web 12, but rather to the tensioning web 18, thereby preventing undesired wrinkling in the fibrous web 12 or, in the worst case, damage to the fibrous web 12.

[0087] So that the tensioning web 18 can transmit the movement of the lamellae 24 in the compression nip 17 to the fibrous web 12, the tensioning web 18 is more elastic in the transverse direction CD, i.e., in the direction transverse to the conveying direction MD, than in the conveying direction MD. This can be achieved by the tensioning web 18 having at least one reinforcing means 26 extending in the conveying direction MD, wherein the elasticity of the reinforcing means 26 is less than the elasticity of the tensioning web 18. In the present exemplary embodiments, the reinforcing means 26 is configured by a plurality of reinforcing bands with a round cross-section that run essentially parallel to one another in the MD direction (Figs. 4a and 4b).

[0088] To ensure sufficient support of the fibrous web 12 while maintaining good extensibility of the tensioning web 18, the tensioning web 18 has a hardness of 20 to 65 ShA and preferably of 25 to 60 ShA for tensioning web widths of less than or equal to 1 m. In the exemplary embodiments, the hardness of the tensioning web 18 is between 30 and 55 ShA for tensioning web widths of less than or equal to 1 m. For tensioning webs with a tensioning web width of greater than or equal to 1 m, on the other hand, a hardness in a range of 30 to 65 ShA and preferably of 35 to 60 ShA is advantageous. In the exemplary embodiments, the hardness of the tensioning web 18 is between 40 and 55 ShA for tensioning web widths of greater than or equal to 1 m.

[0089] For a better transmission of the transverse forces acting in the compression nip 17 on the fibrous web 12, the tensioning web 18 can have a structuring on a side facing the fibrous web 12 to be conveyed, which increases the adhesion between the tensioning web 18 and the fibrous web 12.

[0090] The counter roll 16 can have a smooth surface (optionally with a non-stick coating) to facilitate the sliding of the fibrous web 12 along the counter roll. Additionally or alternatively, the counter roll 16 can have a surface provided with openings for the same purpose, through which compressed air or steam can be passed, so that the fibrous web 12 slides along the counter roll 16 on an air cushion or a steam cushion. The compressed air or steam can also exit from a porous surface of the counter roll 16 with the same effect.

[0091] Before the tensioning web 18 can be compressed together with the fibrous web 12 in the compression nip 17 in the transverse direction CD, at least one spreader roller 28 serves to pre-tension the tensioning web 18 in the transverse direction CD against the restoring force of the tensioning web 18 before the fibrous web 12 is taken up in the tensioning web plane. In the process, the tensioning web 18 is stretched in width. As can be seen from the embodiment shown in Fig. 2, several spreader rollers 28 can be combined to form a spreader unit 29 in order to enable an even greater width expansion of the tensioning web 18. In the embodiment shown in Fig. 2, the spreader unit 29 specifically comprises three spreader rollers 28. However, the number of spreader rollers 28 can also deviate from three and comprise, for example, two, four or five spreader rollers 28. For example, two spreader rollers 28 may be sufficient for certain applications.A spreader 29 with more than three spreader rollers 28 is also possible, for example with four, five or more spreader rollers 28. The spreader rollers can have the same or different settings, such as sheet height and / or wrap angle.

[0092] Between the spreader roller 28 or the last spreader roller 28 of the spreader unit 29, a feed roller 30 with an elastic outer surface 36 is provided, which, together with the counter roller 16, forms a nip 31 (feed nip 31). As shown in Figs. 1 and 2, the feed roller 30 with an elastic outer surface 36 is arranged directly behind the spreader roller 28 or the last spreader roller 28 of a spreader unit 29 in order to thereby minimize the loss of width extension of the tensioning web 18. However, it can also be provided that the feed roller 30 is arranged with an elastic outer surface 36 at a distance from the spreader roller 28 or the last spreader roller 28 of a spreader device 29 as seen in the conveying direction, as long as a pre-stretching of the tensioning web 18 sufficient for the specific application can be maintained (Fig. 5).

[0093] Relaxation of the tensioning web 18 supports the compression of the fibrous web 12, so that in many cases a more uniform and / or greater transverse compression is produced than in applications where no pre-tensioning of the fibrous web 12 is provided before the compression nip 17. The feed nip 31 between the feed roller 30 and the counter roller 16 is connected to the compression nip

[0094] 17, as seen in the conveying direction. In the illustrated embodiments, the feed nip 31 is positioned at least 15° upstream of the compression nip 17 (Figs. 1, 2, and 5a and 5b) or the first compression nip 17', as seen in the conveying direction (Figs. 6 and 7). As a result, the fibrous web 12 and the tensioning web 18 are already in contact with each other for a certain time before the compression nip 17, which contributes to the stabilization of the fibrous web 12 and thus ultimately to the achievement of a higher-quality end product.

[0095] The feed nip 31 between the feed roller 30 with an elastic outer surface 36 and the counter roller 16 also serves for the longitudinal compression of the fibrous web 12, as described below.

[0096] Viewed in the conveying direction, the distance between the feed roller 30 with an elastic surface 36 and the counter roller 16 narrows down to the center of the feed nip 31. Subsequently, the distance between the feed roller 30 and the counter roller 16 increases again. When the tensioning web is conveyed

[0097] 18 and the fibrous web 12 along the feed nip 31, the tensioning web 18 and the elastic surface 36, and ultimately also the fibrous web 12 conveyed by the tensioning web 18, are initially accelerated due to the constriction due to the Venturi effect and then decelerated due to the widening behind the center of the feed nip 31. As a result, the tensioning web 18 and the elastic surface 36, as well as the fibrous web 12 to be conveyed, are compressed in the conveying direction MD or longitudinal direction.

[0098] In order to prevent the tensioning web 18 or the fibrous web 12 to be conveyed from being accelerated too strongly in the constriction of the feed nip 31, it is advantageous if the tensioning web 18 consists of an at least approximately incompressible material in a direction perpendicular to the tensioning web plane and has a thickness of between 4 and 26 mm.

[0099] In the illustrated embodiments, the thickness of the tensioning sheet for tensioning sheets with tensioning sheet widths of less than or equal to 1 m is between 4 and 6 mm, whereas for tensioning sheets with tensioning sheet widths of greater than or equal to 1 m, the thickness of the tensioning sheet is between 4 and 26 mm.

[0100] Furthermore, a deflection roller 32 is provided which, viewed in the conveying direction MD of the tensioning web 18, is arranged downstream of the compression press 10 and which guides the tensioning web 18 away from the fibrous web 12 to be conveyed.

[0101] The deflection roller 32 can, for example, be arranged in a first position (Fig. 5a) or a second position (Fig. 5b). It is possible for the deflection roller 32 to be designed to be displaceable, specifically in such a way that the guidance of the fibrous web 12 along a partial circumference of the compression roller 14 and / or the counter roller 16 can be selectively changed. It can also be provided to move the roller between the two positions, for example, to accommodate different web speeds.

[0102] In the first position of the deflection roller 32 shown in Fig. 5a, the roller arrangement is designed for lower conveying speeds, such as less than 400 m / min. As can be seen from Fig. 5a, the tensioning web 18 is guided sectionally along the compression roller 14 behind the compression nip 17 before it is guided away from the compression roller 14 by the deflection roller 32. As a result, the lamellae 24 cannot immediately return to their undeflected original position after the compression nip 17, which is advantageous at low conveying speeds because the compression of the fibrous web 12 generated in the compression nip 17 is not disturbed again by a possible (partial) erection of the lamellae 24. In this embodiment, the fibrous web 12 is detached from the tensioning web 18 directly after the compression nip 17.

[0103] In the second position of the deflection roller 32 shown in Fig. 5b, the roller arrangement is particularly suitable for higher conveying speeds, such as greater than 400 m / min. In the second position of the deflection roller 32, the tensioning web 18, together with the fibrous web 12, is guided in sections along the counter roller 16. This increases the residence time of the fibrous web 12 on the tensioning web 18, so that at higher conveying speeds, there is sufficient time to transfer the transverse compression from the tensioning web 18 to the fibrous web 12.

[0104] Furthermore, the roller arrangement 10 has a tensioning roller 34, which serves to adjust the pretension of the tensioning web 18 in the conveying direction (see Fig. 1). The tensioning roller 34 can, for example, be arranged on an inner side of the tensioning web 18, so that the tensioning web 18 can be tensioned outwardly by displacing the tensioning roller 34 as needed. Alternatively or additionally, the tensioning roller 34 can be arranged on an outer side of the tensioning web 18, so that the tensioning web 18 can be tensioned inwardly by displacing the tensioning roller 34.

[0105] The basic functionality of the roller arrangement is explained again in summary below.

[0106] Before the tensioning web 18 is brought together with the fibrous web 12, the spreader roller 28 or the spreader rollers 18 of the spreader system serve to stretch the tensioning web 18 in the tensioning web plane in a direction transverse to the conveying direction MD, i.e., in its width. The thus stretched tensioning web 18 is then guided over the feed roller 30 with an elastic outer surface 36, and the tensioning web 18 and the fibrous web 12 are brought together in front of the feed nip 31 between the feed roller 30 with an elastic outer surface 36 and the counter roller 16. Due to the effect of the feed nip 31, the fibrous web 12, the tensioning web 18, and the elastic outer surface 36 are compressed in the conveying direction MD due to the Venturi effect.

[0107] After the feed nip 31, the fibrous web 12 together with the tensioning web 18 is guided in sections along the counter roll 16 to the compression nip 17 of the compression press 10. In this section, the fibrous web 12 is

[0108] - namely by the tensioning track 18 on the one hand and the counter roller 16 on the other hand

[0109] - reliably stabilized. In the compression press 10, the tensioning web 18 and the fibrous web 12 are then compressed in a controlled manner in their respective planes in a direction transverse to the conveying direction MD. Here, too, the tensioning web 12 exerts a stabilizing effect, particularly since it ensures a uniformity of the transverse forces acting on the fibrous web 12 in the compression nip 17.

[0110] After the tensioning web 18 and the fibrous web 12 have left the compression nip 17 of the compression press 10, the tensioning web 18 and the fibrous web 12 are separated from each other by guiding the tensioning web 18 away from the fibrous web 12 by means of the deflection roller 32. This separation can

[0111] - depending on the application - immediately after the compression nip 17 or at a later time (see Fig. 5a or 5b).

[0112] As a result, the roller arrangement produces a fibrous web 12 that is compressed evenly both longitudinally and transversely. Investigations have surprisingly shown that the inventive concept is suitable for web speeds exceeding 1000 m / min. It should also be mentioned that the tensioning web 18 can be made of rubber or can comprise rubber. Instead of rubber, another suitable elastic material can also be used. The tensioning web can have a single-, double-, or multi-layer structure. It is also conceivable, in principle, for the tensioning web to have properties that vary in the transverse direction.

[0113]

[0114] 10 upsetting press

[0115] 12 Fibrous web

[0116] 14 Upsetting roller

[0117] 16 Counter roller

[0118] 17, 17',

[0119] 17", 17'" compression nip

[0120] 18 tension track

[0121] 20 basic bodies

[0122] 22 lateral surface

[0123] 24 slats

[0124] 26 reinforcing agents

[0125] 28 Spreader roller

[0126] 29 Spreading system

[0127] 30 feed roller

[0128] 31 Feed nip

[0129] 32 Deflection roller

[0130] 34 tension roller

[0131] 36 Surface of the feed roller

[0132] MD conveying direction

[0133] CD transverse direction

[0134] L Longitudinal axis

[0135] E Center plane

Claims

Claims 1 . A roller arrangement for producing a compressed fibrous web (12) with a compression press (10) which comprises at least one compression roller (14) and a counter roller (16) and a feed roller (30) and which is designed to produce a compression of the fibrous web (12) in a direction transverse to a conveying direction (CD) and / or in a conveying direction (MD) of the fibrous web (12), wherein an elastic tensioning web (18) receiving the fibrous web (12) is provided, and wherein the elastic tensioning web (18) is guided through a nip (17), preferably a compression nip (17), between the compression roller (14) and the counter roller (16) and over the compression roller (14), and wherein the elastic tensioning web (18) is guided through a nip (31), preferably a feed nip (31), between the feed roller (30) and the counter roller (16), and wherein the nip (31), preferably a feed nip (31),between the feed roller (30) and the counter roller (16) in the circumferential direction of the counter roller (16) is arranged upstream of the nip (17) formed by the compression roller (14) and the counter roller (16), preferably the compression nip (17), seen in the conveying direction (MD), characterized in that the feed roller (30) comprises an elastic outer surface (36) over its circumference.

2. Roller arrangement according to claim 1, characterized in that the elastic outer surface (36) of the feed roller (30) has a hardness of 20 to 65 ShA, preferably of 25 to 60 ShA and for example of 30 to 55 ShA.

3. Roller arrangement according to claim 1 or 2, characterized in that the elastic outer surface (36) is designed as an elastic coating (36) or a replaceable, elastic roller cover (36), in particular the elastic coating or the replaceable, elastic roller cover consists essentially of a plastic, preferably an elastomer, particularly preferably a rubber or a polyurethane.

4. Roller arrangement according to one of the preceding claims, characterized in that the elastic outer surface (36) has a thickness of greater than or equal to 4 mm, in particular greater than or equal to 10 mm, preferably greater than or equal to 20 mm, and less than or equal to 60 mm, in particular less than or equal to 40 mm, preferably less than or equal to 30 mm.

5. Roller arrangement according to one of the preceding claims, characterized in that the elastic outer surface (36) of the feed roller (30) has a thickness of greater than or equal to 10 mm, preferably greater than or equal to 20 mm, and less than or equal to 40 mm, preferably less than or equal to 30 mm, and in that the elastic tensioning web (18) guided over the feed roller (30) has a thickness of greater than or equal to 4 mm, preferably greater than or equal to 10 mm, and less than or equal to 30 mm, preferably less than or equal to 20 mm.

6. Roller arrangement according to one of the preceding claims, characterized in that the elastic outer surface (36), in particular on a side facing the fibrous web (12) to be conveyed, has a structuring.

7. Roller arrangement according to one of the preceding claims, characterized in that the feed roller (30) is arranged immediately in front of the nip (17) formed by the compression roller (14) and the counter roller (16), in particular less than or equal to 90°, preferably less than or equal to 60°, and in particular greater than or equal to 15°.

8. Roller arrangement according to one of the preceding claims, characterized in that the feed roller (30) comprises a controllable drive, wherein the drive is suitable for driving and / or braking the feed roller (30).

9. Roller arrangement according to at least one of the preceding claims, characterized in that the feed roller (30) is arranged between at least one spreader roller (28) or at least one spreader element (28) and the counter roller (16), in particular immediately after the spreader roller (28), and in that the spreader roller (28) has a crown of greater than or equal to 1% and less than or equal to 5% of its extension transverse to the conveying direction (MD).

10. Roller arrangement according to at least one of the preceding claims, characterized in that the compression roller (14) has a rotationally symmetrical base body (20) which is rotatable about a longitudinal axis (L) and has a lateral surface (22) on which at least two elastically deformable and / or deflectable annular lamellae (24) are arranged, which extend in the radial direction away from the lateral surface (24) and which surround the base body (20) in the circumferential direction, in particular wherein the lamellae (24) are inclined in pairs in a mirror-symmetrical manner in the direction of the central plane (E) of the compression roller (14) to form an angle of inclination obliquely to a central plane (E) of the compression roller (14) which is oriented perpendicular to the longitudinal axis (L) of the compression roller (14). 11 . Roller arrangement according to at least one of the preceding claims, characterized in that several compression rollers (14) are assigned to the counter roller (16) and each form a nip (17', 17", 17'") with the counter roller (16).

12. A method for producing a fibrous web (12) compressed in the conveying direction (MD) and transversely to the conveying direction (CD), in particular using a roller arrangement according to one of the preceding claims 1 to 11, the method comprising the following steps: Bringing together a fibrous web (12) with a tensioning web (18) which receives the fibrous web (12) for conveying the fibrous web (12) in a conveying direction (MD); Conveying the tensioning web (18) together with the fibrous web (12) to an upsetting press (10) which comprises at least one upsetting roller (14) and one counter roller (16) and one feed roller (30) and which is used to produce an upsetting of the fibrous web (12) in a Direction transverse to the conveying direction (MD) and in the conveying direction (MD) in a fibrous web plane; and Guiding the tensioning web (18) together with the fibrous web (12) through a nip (31), preferably a feed nip (31), formed between a feed roller (30) and the counter roller (16), and over the feed roller (30); and Guiding the tensioning web (18) together with the fibrous web (12) through a nip (17) formed between the compression roller (14) and the counter roller (16), preferably compression nip (17), and over the compression roller (14) in order to guide the fibrous web (12) transversely to the conveying direction (MD) in the plane of the fibrous web; characterized in that the feed roller (30) comprises an elastic lateral surface (36) such that the fibrous web (12) is compressed by a nip (31), preferably a feed nip (31), formed between a feed roller (30) and the counter roller (16), in conveying direction (MD) is compressed by the elastic jacket surface (36) and the elastic tensioning track (18).

Images