Covering made of plastic film material with a seam element and manufacturing process

Abstract

Covering made of plastic film material for a machine for the production and / or finishing of a material web with at least one seam element that has improved strength and does not include parts made of bent film material.

Description

The present invention relates to a screen, in particular a drying screen or a structuring screen, made of plastic film material for a machine for the production and / or finishing of a material web, in particular a fibrous web such as paper, cardboard, or tissue, with a material web contact side and a machine contact side opposite the material web contact side. The screen comprises at least one seam element which joins two separate areas of the screen together. The seam element can be used both for producing the screen from individual plastic film sections and for closing a finished screen, so that the screen forms an endless band after closing. The longitudinal direction of the seam element can be oriented in the machine direction (MD), in the machine transverse direction (CD), or obliquely to these directions.The invention further relates to a method for producing such a seam element. The plastic film material can consist of a single layer, i.e., be monolithic, or be composed of several laminated layers. The layers lie flat against each other and are bonded together flat, so that no complex structures with gaps between the layers exist, such as those shown, for example, in WO2015 / 081417 A1. The covering disclosed in WO2015 / 081417 A is not a covering made of plastic film material as defined in the present document. The present invention also relates to a method for producing such a covering with at least one such seam element. Seam elements suitable for coverings made of plastic film material are known from the prior art. For example, DE 10 2017 114 964 A1, DE 10 2020 113 073 A1 and DE 10 2021 128 525 A1 disclose suitable seam elements. The seam elements disclosed in these documents each comprise parts made of curved film material. The inventors recognized that seam elements with parts made of curved film material can exhibit reduced strength under cyclic bending loads because the curved parts can have "frozen" stresses. The object of the invention is to provide a covering made of plastic film material with at least one seam element that has improved strength. The problem is solved according to the invention by an embodiment according to the independent claims. Further advantageous embodiments of the present invention are found in the dependent claims. The invention is explained below with reference to the figures. The figures show in detail: Fig. 1: Covering with a seam element; Fig. 2: Seam element according to the invention in top view; Fig. 3: Cross-section through a seam element according to the invention at AA and BB; Fig. 4: Cross-sections through a recessed area according to the invention in various embodiments; Fig. 5: Butt edge profile according to the invention in a further embodiment; Fig. 6: Butt edge profile according to the invention in two further embodiments; Fig. 7: State after step S1A / B in top view and cross-section; Fig. 8: State after step S2A / B in top view and cross-section; Fig. 9: State after step S3A / B in top view and cross-section; Fig. 10: State after step S4A / B in top view and cross-section; Fig. 11: State after step S5 in top view and cross-section; Fig. 12: State after step S6 in top view and cross-section.Fig. 13: Seam element according to the invention in a further embodiment in cross-section with auxiliary elements for joining the two seam element sections. Fig. 14: State after step S3A / B in cross-section of further embodiments. Fig. 15: States after steps S1A / B, S2A / B and S3A / B in cross-section of a further embodiment. Fig. 16: State after step S3A / B in cross-section of further embodiments. Fig. 1 shows a highly schematic representation of a covering with a seam element, so that no specific details of the present invention are visible. The covering is designated 1 and the seam element 2. The seam element 2 extends between a first covering section, designated 3, and a second covering section, designated 4. The covering sections 3 and 4 consist of plastic film material. The seam element 2 has a longitudinal direction that defines the x-axis of a Cartesian coordinate system. The first covering section 3 is arranged in the positive y-direction with respect to the seam element 2, and the second covering section 4 is arranged in the negative y-direction with respect to the seam element 2. The length of the seam element 2, measured in the x-direction, is designated L. The dimension of the seam element 2, measured in the y-direction, is also referred to as its width and is designated B.The z-direction corresponds to the surface normals of the covering sections 3 and 4 when they are arranged flat. The seam element 2 connects the two covering sections 3 and 4. A seam element 2 according to the invention can join any fabric sections together, i.e., the longitudinal direction x can be oriented both in the machine direction MD and perpendicular to MD, i.e., in the machine transverse direction CD. The longitudinal direction x of the seam element can also run at any angle obliquely to the machine direction MD. A seam element 2 according to the invention can also join a finished fabric to form an endless strip. In this case, the x-direction can be arranged in the machine transverse direction CD or run obliquely to it. In each case, the seam element extends over the entire width of the fabric, i.e., the width of the fabric corresponds to the length L of the seam element if the longitudinal direction x is exactly aligned with CD. If the seam element runs obliquely, the length L of the seam element is greater than the width of the fabric.It is also possible that a covering consisting of only a single section is joined to form an endless band by a seam element 2 according to the invention. In this case, in the terminology of this document, the first covering section 3 transitions into the second covering section 4. In Fig. 1, the two lateral boundary lines must be disregarded, so that the now open lateral ends of the covering sections 3 and 4 merge into one another in a plane lying behind the drawing surface in the z-direction. Fig. 2 shows a top view of a seam element 2 according to the invention. The seam element 2 comprises a first seam element section, which is designated 5, and a second seam element section, which is designated 6. The seam element sections 5 and 6 are separated from each other in Fig. 2 by an undulating line, which is designated 7 and extends the entire length of the seam element 2. The term "undulating" is used here in a very broad sense and means that the line oscillates back and forth in the y-direction as it propagates in the x-direction. The propagation in the x-direction can decrease to zero section by section, as with the finger-like line in Fig. 2 or in Fig. 5, or even reverse itself section by section, as with the lines in Fig. 6. The undulating line marks the position of the edges of the seam element sections 5 and 6 where they abut each other. These edges are therefore referred to as butt edges.Only a narrow gap is arranged between the two butt edges 7, the width of which is essentially determined by the manufacturing tolerances of the butt edges 7. When installed, the covering is under tension, which also acts on the seam elements, potentially causing the gap width to increase slightly. The undulating shape of the butt edges 7 can be configured in various ways. In any case, the undulating shape of the butt edges 7 has a multitude of points where the edges reverse from the positive y-direction to the negative y-direction (and vice versa) as they propagate in the x-direction. Figure 2 shows a dimension U measured in the x-direction, which illustrates the so-called undulation width. The undulation width U indicates the distance between two mutually inverse reversal points in the x-direction. Generally, the undulation width is less than or equal to the width B of the seam element. In Figure 2, the undulation width is shown in the x-direction.Figure 2 shows two section lines labeled AA and BB, to which the sections shown in Figure 3 refer. Figure 2 clearly shows that many other locations can be found that have equivalent sections to the selected sections AA and BB. Fig. 3 shows the two sections AA (top) and BB (bottom) according to Fig. 2 through a seam element according to the invention. The first seam element section 5 comprises a countersink, which is designated 5.1, and a cover element, which is designated 5.2. The second seam element section 6 comprises a countersink, which is designated 6.1, and a cover element, which is designated 6.2. At the position of section AA, a cavity extends between the countersink 5.1 and the cover element 5.2, which is provided for receiving a connecting element. At the position of section BB, a cavity also extends between the countersink 6.1 and the cover element 6.2, which is provided for receiving a connecting element. The connecting element is designated 8. The connecting element 8 extends in the x-direction, i.e., into the plane of the drawing, over substantially the entire length L of the seam element.Since sections AA and BB each represent a multitude of other similar sections, there are numerous such cavities. All these cavities align in the x-direction between the respective recessed areas and the associated cover elements to form a channel in which the connecting element is located. In this process, one cavity alternates with the first, and the following cavity with the second, seam element section. Cover elements 5.2 and 6.2 each consist of a film-like plastic material. Figure 3 shows that the first covering section 3 and the recess 5.1 of the first seam section 5 form a single piece, i.e., they are formed in one piece. The same applies to the second covering section 4 and the recess 6.1 of the second seam section 6. Alternatively, the first seam section 5 can be described as comprising parts of the first covering section 3, and the recess 5.1 is located within these parts of the first covering section 3. The same applies to the second covering section 4, the second seam section 6, and the recess 6.1. If the covering sections consist of multi-layered film material, the indentation areas may not form a single unit with all layers. For example, with a two-layer film, an indentation area might only form a single unit with one of the two layers (see the embodiment according to Fig. 15 and, in particular, the embodiments according to Fig. 16). Due to this one-piece construction, a seam element according to the invention exhibits high strength in every case. Fig. 3 shows that the cover element is connected in the y-direction on both sides of the cavity to the associated recess area and thus to the associated covering section. It is advantageous if the surface of the cover elements, oriented in the z-direction, is flush with the surface of the corresponding fabric sections, also oriented in the z-direction, so that there is no step or only a very small step between these elements. An excessively large step can lead to stress on the seam element if the cover elements are located on the machine side of the fabric. If the cover elements are located on the fiber web side, an excessively large step can cause indentations in the fiber web. To avoid such a loss of quality in the fiber web under all circumstances, the cover elements are preferably located on the machine side of the fabric. In the embodiment shown in Fig. 3, the height of the indentation area measured in the z-direction, and thus the strength of the weld element, can be increased by choosing a smaller height of the cover element in the z-direction. However, there are also embodiments, described below, in which the cover elements can also contribute more to the strength of the weld element (see the embodiment according to Fig. 15). The deck elements are connected to the parts of the corresponding recessed area that lie laterally to cavity 8. These parts, lying laterally to the cavity, belong to the respective covering section. This connection can be made by gluing or welding / laminating. Fig. 4 shows in the upper part the general structure of a countersink area using the first countersink area 5.1 as an example. The second countersink area 6.1 is structured accordingly. In general, a countersink area comprises N countersink sections, where N is an odd number and N ≥ 3. The countersink sections arranged next to each other in the y-direction are designated 5.1.1, 5.1.2, ... 5.1.N-1 and 5.1.N. The countersink sections with an odd last digit have a smaller countersink depth than the countersink sections with an even last digit. Countersink sections with an even last digit form the cavities for receiving the connecting element 8. The countersink sections with an odd last digit serve for connection with the associated cover element. For N > 3, a seam element according to the invention comprises more than one connecting element 8. This allows the strength of a seam element according to the invention to be further increased. The insertion depth of the insertion sections is measured in the z-direction, with the upper edge of the corresponding covering section 3 or 4 serving as the reference line. This dimensioning definition assumes that the seam element rests on a flat surface, with the cover elements positioned on top. The undulation area U overlaps with the recessed sections. It is possible that the undulation area U only partially overlaps the first recessed section 5.1.1 or 6.1.1, as shown, for example, in Fig. 3. In this case, U < B. The undulation area U could also completely overlap the first recessed section 5.1.1 or 6.1.1. In the limiting case, U = B. In any case, the undulation area completely overlaps all other recessed sections (5.1.M or 6.1.M for M > 1). It is also conceivable that the undulation area U extends beyond the recessed section in the y-direction, i.e., includes parts that have the same thickness in the z-direction as the covering sections arranged laterally from the seam element and are not covered by a cover element. In this case too, U = B, since the width B of the seam element is then defined by the width U of the undulation area. Fig. 14 shows such embodiments. Fig. 4 shows, in the lower part, an exemplary embodiment of a recessed area 5.1, which belongs to a seam element with two connecting elements. The connecting elements have a round cross-section. These connecting elements could be conventional plug-in wires. To ensure that the cavities for the connecting elements have a suitable shape, the base of the recessed sections 5.1.2 and 5.1.4 has the form of a fillet. In contrast, the base of the recessed sections 5.1.1, 5.1.3, and 5.1.5 is flat to allow for a large-area connection with the associated cover element. This is advantageous, for example, when the connection between the cover element and the odd-numbered recessed sections is made by welding / lamination. However, the base of the odd-numbered recessed sections could also be designed differently.The base of the odd-numbered recessed sections could, for example, have several fine grooves or ridges. This can be advantageous if the connection between the cover element and the odd-numbered recessed sections is made by gluing. The same applies to the underside of the cover element. Fig. 5 shows a further embodiment of a seam element according to the invention in a top view. In contrast to the embodiment shown in Fig. 2, the course of the butt edges in the x-direction exhibits a variation in period length. As a result, the number of "fingers" per unit length in the x-direction, with which the two sides of the seam element interlock, is greater at both ends of the seam element, and thus at the edge of the covering, than in the center of the covering. Consequently, the seam element shown exhibits greater strength at the edge of the covering than in the center. This can be advantageous, since a covering is typically subjected to greater stress at its lateral edges than in its center. The inverse shaping of the two butt edges of the seam element sections 5 and 6, as shown in Figures 3 and 5, results in a positive fit similar to a tongue and groove joint. In principle, the "fingers" could also be shaped with 90° angles, as in a tongue and groove joint. However, films tend to crack at sharp angles. Therefore, it is advantageous if the "fingers" have a rounded contour. After removing the connecting element(s), the positive fit of the seam element sections 5 and 6 can be released by moving them relative to each other in the y or z direction. The butt edges of a seam element according to the invention can also be designed such that the connection exhibits a force-fit. In this case, the connection of the seam element sections 5 and 6 can only be released after the removal of the connecting element(s) by a relative movement in the z-direction. That is, the seam element can absorb a force in the y-direction when the butt and joining edges of the seam elements are in contact, even if no connecting element is located in the seam element. Figure 6 shows the contour of the butt edges in two exemplary embodiments with frictional connection. In the upper part of Figure 6, the contour of the butt edges, which in embodiments with frictional connection are more accurately described as joining edges, has a shape that results in a hammerhead-like connection. In the lower part of Figure 6, the contour of the joining edges has a shape that results in a dovetail-like connection. In both embodiments, the contours have a smooth, rounded shape to prevent cracking. The vertical dashed lines indicate the contour of the connecting elements. Both embodiments include two connecting elements. The hammerhead-like embodiment is characterized by a shorter extension of the weld element in the y-direction. The use of plug-in wires as connecting elements is well suited to this. The dovetail-like embodiment extends over a greater distance in the y-direction.The connecting elements are also wider in this direction and are advantageously designed as foil strips. It is also conceivable that the connecting elements are designed as fabric strips. Fabric strips can be particularly advantageous in embodiments with frictional connection, as the frictional connection relieves the connecting elements of shear forces. Overall, the frictional connection gives the seam element greater strength against tensile forces acting in the y-direction. Furthermore, the frictional connection can significantly facilitate the joining of the seam element sections and the insertion of the connecting elements, especially if these actions are carried out after the covering has been installed in the machine. The aforementioned embodiments of the connecting elements, i.e. plug-in wires, foil strips and fabric strips, can be used in all embodiments of a seam element according to the invention and can also be combined with each other in seam elements with more than one connecting element. The inventive method for producing a covering with at least one seam element according to the invention is described in more detail below. This is done with reference to Figures 7, 8, 9, 10, 11 to 12, each of which represents the state after carrying out certain steps of the inventive method. The inventive method for producing a covering with at least one seam element comprises the following steps, wherein a longitudinal direction of the seam element defines an x-direction and a surface normal of the covering defines the z-direction of a Cartesian coordinate system: S1A: Providing a first covering section with an edge extending substantially straight in the x-direction, wherein the first covering section consists of a film-like plastic material; S2A: Removing material along the edge of the first covering section, so that a depression area is formed in the first covering section;S3A: Attaching a cover element made of a film-like plastic material such that at least one cavity is formed between a base of the recessed area and the cover element, wherein the at least one cavity extends at a distance along the edge of the first covering section, and wherein the cover element is connected to the first covering section in the y-direction on both sides of the cavity by gluing or welding / laminating; S4A: Trimming the first covering section so that a butt or joining edge is formed with a profile which, viewed in the z-direction, has an undulating shape, wherein the profile intersects the at least one cavity at a plurality of points; S1B: Providing a second covering section with an edge extending straight in the x-direction, wherein the second covering section consists of a film-like plastic material;S2B: Removal of material along the edge of the second covering section, such that a recess is formed in the first covering section; S3B: Attachment of a cover element made of a film-like plastic material, such that at least one cavity is formed between a base of the recess and the cover element, wherein the at least one cavity extends at a distance along the edge of the second covering section, and wherein the cover element is connected to the second covering section in the y-direction on both sides of the cavity by gluing or welding / laminating;S4B: Trimming the second covering section so that a butt or joining edge with a profile is created which, viewed in the z-direction, has an undulating shape, wherein the profile intersects the at least one cavity at a plurality of points, and wherein the profile of the second covering section is the inverse of the profile of the first covering section; S5: Joining the two covering sections together so that the butt or joining edges of the two covering sections lie directly next to each other, and the cavities of the two covering sections form at least one continuous channel extending in the x-direction; S6: Providing at least one connecting element which is suitable for being inserted into the at least one continuous channel. The steps can be executed in the specified order. Likewise, steps S1B-S4B can be executed in any temporal relation to steps S1AS4A, provided that steps S1A-S4A and steps S1B-S4B are executed in the specified order. For example, the steps could also be executed in the following sequences: S1A, S1B, S2A, S2B, S3A, S3B, S4A, S4B or S1A, S1B, S2B, S2A, S3A, S3B, S4B, S4A. Steps S5 and S6 would then follow in this order. Steps S5 and S6 are optional, since the joining of the seam element does not necessarily have to be carried out during the production of a covering according to the invention, but can also take place during installation in the machine, and since in certain embodiments standard connecting elements can be used which are not specific to a covering according to the invention and which customers can also obtain elsewhere. Figures 7, 8, 9, 10, 11 to 12 assume that the steps are carried out in the sequence S1A, S1B, S2A, S2B, S3A, S3B, S4A, S4B, S5 and S6. These figures each show the state achieved after specific steps, with the top view showing the state and the cross-sectional view showing the state in the lower part. Fig. 7 shows the state after step S1B, i.e., after the two fabric sections have been prepared. The fabric sections are shown arranged side by side in the y-direction. This arrangement serves only for the clarity and comparability of the following figures and is not essential for carrying out the method according to the invention. In principle, it is possible that the edges of the fabric sections are not perfectly straight, since the actual edges of the subsequent seam element sections, i.e., the butt or joining edges, are only formed by steps S4A and S4B. An excessively large deviation from a straight edge will, in any case, lead to increased waste, as significantly more material must be cut off in these steps if the edges are not reasonably straight. Fig. 8 shows the state after step S2B. Material removal has created a recessed area along the edges. This material removal can be carried out, for example, by milling or grinding, with milling being preferred. Laser removal is also possible. In the illustrated embodiment, each recessed area comprises three recessed sections. These three recessed sections can be formed in three sequential removal steps. Alternatively, in a first removal step, the recess can be reduced to the level of the two outer recessed sections, and then the middle recessed section can be further reduced. Fig. 9 shows the state after step S3B, i.e., after the cover elements have been attached over the recessed areas. Attachment can be achieved by gluing or welding / laminating. This has resulted in cavities forming at the locations of the central recessed sections. If the edges are not straight, the distance between the edge and the cavity is not constant in the x-direction. Fig. 10 shows the state after step S4B. The term "cutting through" indicates that the undulating profile, coming from one side of the cavity, not only intersects the cavity but penetrates it from one side to the other and continues on the other side. The term "inverse" indicates that the two profiles fit together. Ideally, the butt or joining edges of the two fabric sections run exactly parallel to each other when the fabric sections are arranged as shown in Fig. 10. However, deviations from parallelism can occur due to manufacturing tolerances. Trimming can be carried out, for example, by milling, punching, laser cutting, or with suitable blades, with laser cutting offering the greatest flexibility and accuracy. Fig. 11 shows the state after step S5. Due to manufacturing tolerances, a narrow gap may occur between the two butt or joining edges. Fig. 12 shows the state after step S6, where the connecting element is already arranged in the channel. The connecting element, arranged in the continuous channel, prevents the seam from coming loose. Steps S5 and S6 are easiest to perform if a flat surface is available, allowing both weld element sections to be placed completely on the surface when they butt together. Before step S6, it is advantageous to place a weighted plate on top of the two joined weld elements to prevent any offset in the z-direction. If steps S5 and S6 are to be carried out only after the fabric has already been installed in a machine for producing a fiber web, then these steps can be more difficult to perform. Without a suitable support, the seam element sections tend to move apart again after step S5, preventing step S6 from being carried out. A first solution is to select a seam element with a force-fit shape for the joining edges, thus preventing separation in the y-direction. A further solution is to cut the joining edges not perpendicularly, i.e., parallel to the z-direction, but slightly obliquely to the z-direction. Fig. 13 shows such an embodiment in the installed position after step S5.The seam element on the left side is held from below by a support element labeled 9. On the right side, the seam element is pressed downwards by a weighting element labeled 10. Due to the angled joining edges, the right-hand seam element section cannot slip in the negative z-direction and is also held in position in the y-direction by the positive locking mechanism, allowing step S6 to be carried out without major problems. Fig. 14 shows two further embodiments, each with three connecting elements. The embodiments are shown after step S3A. The variant shown above comprises one, and the variant shown below comprises three cover elements. A narrow web is arranged between the three cover elements. This web could also be omitted, so that the three cover elements are arranged directly next to each other. The undulation area is designated with the letter U. It is evident that this extends beyond the recessed area and the cover element(s) on both sides in the y-direction. As a result, the cover element(s) is cut into a multitude of separate parts in the subsequent step S4A or S4B. The same applies to the recessed area(s). In the terminology of this document, this multitude of individual parts is still referred to collectively as a cover element or a recessed area. Figure 14 shows that after step S4A or S4B, each part of the cover element is connected to the corresponding covering section on both sides of all cavities in the y-direction. Fig. 15 shows an embodiment of a covering, which by way of example consists of two laminated layers. Fig. 15 shows the embodiment for three states, with the different states shown superimposed. The uppermost subfigure shows the embodiment after step S1A or S1B. This embodiment comprises a thick layer, which is arranged at the bottom. A comparatively thin layer is laminated onto the thick layer, with the lamination not extending to the right-hand edge shown, so that the thin layer is not bonded to the thick layer on this side. The middle subfigure of Fig. 15 shows the embodiment after step S2A or S2B. To allow the material to be removed from the recessed area, the thin layer was bent upwards and backwards to the side. To prevent plastic deformation of the thin layer, it is advantageous to choose a large bending radius.For this to work, the unlaminated area must be sufficiently wide in the y-direction. The lower part of Fig. 15 shows the embodiment after step 3A. The thin layer was placed back onto the thick layer and laminated with it. The lamination takes place on a portion of the covering section and the associated seam element section. In this embodiment, part of the thin layer forms the top element, giving such a seam element particularly high strength, since there is no separate connection with the corresponding parts of the covering section, either in the recessed area or the top element; instead, these parts each form a single unit. For a layer of a covering section to function as a top element, the layer in question must be on the outside; for example, in a three-layer covering, the middle layer cannot function as a top element. A modification of the embodiment shown in Fig. 15 consists in the fact that, initially, the thin upper layer is not laminated to the covering section at all. This means that it does not need to be bent away for step S2A or S2B. Finally, in step S3A or S3B, it is laminated onto the entire covering section and the seam element section. The end result of this modification is no different from the embodiment shown in Fig. 15. Figure 16 shows, in sub-figures (a) to (d), four embodiments particularly well suited for coverings consisting of multiple laminated layers. The horizontal lines indicate the individual layers of the depicted covering section. The diagonally hatched areas each belong to the top element, which is made of monolithic material. Each top element has a projection positioned to absorb the tensile forces acting on the seam element. For this purpose, the projection is located in the recess adjacent to the butt edge of the seam element section. In the illustrated embodiments, this is the third recess. The monolithic material is preferably joined to the multi-layered material by welding.These embodiments are characterized by particularly high strength, since the projection made of monolithic material, which absorbs the tensile forces, is also particularly resistant to cutting into the connecting element. The embodiments according to partial figures (b) and (d) are particularly advantageous in this respect. In partial figure (a), the cover element is formed in one piece, i.e., the projection forms a single unit with the rest of the cover element. In the first recessed section, only the uppermost layer has been removed, while in the second and third recessed sections, the removal extends over more than the two uppermost layers and is of the same magnitude. The embodiment shown in partial figure (b) differs from the embodiment according to partial figure (a) in that the removal in the third recessed section is greater than in the second recessed section. As a result, the projection extends into the second-lowest layer of the covering section. Preferably, the projection extends to the lowest layer of the covering section (see partial figure (d)). In the embodiments shown in partial figures (c) and (d), the cover element is composed of two pieces.The monolithic sections of the cover element are preferably joined together by welding. The embodiment shown in partial figure (c) corresponds to the embodiment shown in partial figure (a) with respect to the depth of the material removal in the recessed sections. The embodiment shown in partial figure (d) comprises one more layer than the other embodiments. The material removal in the first and second recessed sections extends over part of the second-highest layer. The projection extends downwards to the lowest layer and is recessed at the top into a step in the remaining cover element. The embodiments shown in Fig. 16 are merely examples of further embodiments of the invention, which a person skilled in the art can find without inventive effort. Conventional coverings made of plastic film material are usually perforated. In a covering according to the invention, the components required for production can be pre-perforated. This applies to the covering sections, the cover elements, and the connecting elements, provided they are formed from a single strip of film. It is advantageous if the perforation of the individual parts matches and they are arranged accordingly, resulting in very homogeneous permeability across the entire covering, including the seam element. An equally good result can be achieved by starting with non-perforated material in the production process and then perforating the entire covering after it has been manufactured.If plug wires are used as connecting elements, they should either be arranged so that they cannot conflict with the perforation, or removed before the perforation. Finally, it should be mentioned that for a seam element as defined in this document, it is irrelevant whether it is in the assembled state, i.e., whether the butt and joining edges are aligned and the connecting element(s) are located in the designated cavities, or whether it is in a separated state. In the latter case, a connecting element need not even be present. The seam element according to the invention is then simply formed by the two seam element sections with their associated covering sections, regardless of how the seam element sections are arranged relative to each other. This means that a separate xyz coordinate system must then be used for each seam element section. The same applies to the method according to the invention. Reference symbol list 1 Covering 2 Seam element 3 First covering section 4 Second covering section 5 First seam element section 5.1 Recess area in the first seam element section 5.1.1 First recess area in the first seam element section 5.1.2 Second recess area in the first seam element section 5.1.3 Third recess area in the first seam element section 5.1.4 Fourth recess area in the first seam element section 5.1.5 Fifth recess area in the first seam element section 5.1.N Nth recess area in the first seam element section 5.2 Cover element in the first seam element section 6 Second seam element section 6.1 Recess area in the second seam element section 6.2 Cover element in the second seam element section 7 Butt edge or joining edge 8 Connecting element 9 Support element 10 Weighting element B Width of the seam element L Length of the seam element U Undulation area or width of the undulation area QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature WO 2015 / 081417 A1

[0001] WO 2015 / 081417 A

[0001] DE 10 2017 114 964 A1

[0002] DE 10 2020 113 073 A1

[0002] DE 10 2021 128 525 A1

[0002]

Claims

A covering (1) for a machine for the production and / or finishing of a material web, comprising at least one first covering section (3), at least one second covering section (4), and at least one seam element (2), wherein the covering sections (3, 4) consist of a plastic film material and the seam element (2) has a longitudinal direction, and wherein the longitudinal direction defines an x-direction of a Cartesian coordinate system and a surface normal of a covering section (3, 4) defines a z-direction of the Cartesian coordinate system, and wherein the seam element (2) comprises a first seam element section (5) and a second seam element section (6), and wherein the first seam element section (5) comprises parts of the first covering section (3) and the second seam element section (6) comprises parts of the second covering section (4), characterized in that each seam element section (5, 6) has a butt or joining edge (7), a cover element (5.2, 6.2) made of plastic film material and comprising a recessed area (5.1, 5.2), wherein the butt or joining edges (7) extend in the x-direction over the entire seam element (2) and, viewed in the z-direction, follow an undulating line, and wherein each recessed area (5.1, 5.2) is recessed into the parts of the covering sections (3, 4) belonging to the associated seam element section (5, 6), such that a plurality of cavities extends between the recessed area (5.1, 5.2) and the associated cover element (6.1, 6.2), wherein the respective cover element (6.1, 6.2) is connected in the y-direction on each side of each cavity to the parts of the covering sections (3, 4) belonging to the associated seam element section (5, 6) by gluing or welding / laminating, and wherein the butt- orThe joining edges (7) of the seam element sections (5, 6) can be placed next to each other in such a way that the cavities form at least one continuous channel which is provided for receiving a connecting element (8). Covering (1) according to claim 1, wherein the undulating line is shaped such that the seam element (2) can absorb a force acting in the y-direction when the butt or joining edges (7) of the seam element sections (5, 6) are placed next to each other such that the cavities form at least one continuous channel, even if there is no connecting element (8) in the at least one channel. Covering (1) according to claim 2, wherein the butt or joining edges (7) are inclined towards the z-direction. Covering (1) according to one of the preceding claims, wherein the covering sections (3, 4) and the seam element sections (5, 6) are perforated. Covering (1) according to one of claims 1 to 4, wherein at least one connecting element (8) is designed in a strip shape and consists of plastic film material. Covering (1) according to claim 5, wherein the connecting element (8) is perforated. Covering (1) according to one of claims 1 to 4, wherein at least one connecting element (8) is designed in a strip shape and consists of woven material. Covering (1) according to one of the preceding claims, wherein the plastic film material of at least one covering section (3, 4) is formed in multiple layers, and wherein the cover element (5.2, 6.2) belonging to this covering section is formed from a layer of the multi-layered plastic film material. Covering (1) according to one of claims 1 to 7, wherein the plastic film material of at least one covering section (3, 4) is multilayered, and wherein the cover element (5.2, 6.2) belonging to this covering section is made of monolithic material and has a projection which is arranged in such a way that it can absorb tensile forces acting on the seam element (2). A method for producing a covering (1) with a seam element (2) for a machine for producing and / or finishing a web of material comprises the following steps, wherein a longitudinal direction of the seam element (2) defines an x-direction and a surface normal of the covering (1) defines the z-direction of a Cartesian coordinate system: S1A: Providing a first covering section (3) with an edge extending substantially straight in the x-direction, wherein the first covering section (3) consists of a film-like plastic material; S2A: Removing material along the edge of the first covering section (3) such that a recess (5.1) is formed in the first covering section (3); S3A: Attaching a cover element (5.2) made of a film-like plastic material such that at least one cavity exists between a base of the recess (5.1) and the cover element (5.2).2) is formed, wherein the at least one cavity extends at a distance along the edge of the first covering section, and wherein the cover element (5.2) is connected to the first covering section (3) in the y-direction on both sides of the cavity by gluing or welding / laminating; S4A: Trimming the first covering section (3) so that a butt or joining edge (7) is formed with a profile which, viewed in the z-direction, has an undulating shape, wherein the profile intersects the at least one cavity at a plurality of places; S1B: Providing a second covering section (4) with an edge extending substantially straight in the x-direction, wherein the second covering section (4) consists of a film-like plastic material; S2B: Removing material along the edge of the second covering section (4) so ​​that a recessed area (6.1) is formed in the second covering section (4); S3B: Attachment of a cover element (6.2) made of a film-like plastic material, such that at least one cavity is formed between a base of the recessed area (6.1) and the cover element (6.2), wherein the at least one cavity extends at a distance along the edge of the second covering section (4), and wherein the cover element (6.2) is connected to the second covering section (4) in the y-direction on both sides of the cavity by gluing or welding / laminating; S4B: Trimming of the second covering section (4) such that a butt or joining edge (7) is formed with a profile which, viewed in the z-direction, has an undulating shape, wherein the profile intersects the at least one cavity at a plurality of places, and wherein the profile of the second covering section (4) is inversely formed to the profile of the first covering section (3). Method according to claim 10, wherein the method additionally comprises the following step, which is carried out after the other steps: S5: Joining the two covering sections (3, 4) together, such that the butt or joining edges (7) of the two covering sections (3, 4) are directly adjacent to each other, and the cavities of the two covering sections (3, 4) form at least one continuous channel extending in the x-direction.

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