BASIC STRUCTURE OF A STRINGING FOR A MACHINE FOR THE MANUFACTURING OR PROCESSING OF A FIBER PLATFORM AND METHOD FOR ITS MANUFACTURING

Description

[0001] The invention relates to the basic structure of a covering for a machine for the production or processing of a fibrous web, a covering, and a method for producing a basic structure.

[0002] Fabrics for paper machines or similar equipment often have a basic structure that provides stability and absorbs forces, particularly tensile forces, acting on the fabric during operation. Most of the basic structures used today consist entirely or partially of woven fabrics.

[0003] A classic method for producing the required endless fabric loops is circular weaving. In this process, the endless structure is created directly on the loom itself and has no seams. However, circular weaving is a very slow and labor-intensive manufacturing method. Furthermore, the exact length of the desired warp must be known during the weaving process. Since each position in a paper machine requires a very specific warp loop length, the production of such basic structures is only possible for a specific order.

[0004] As an alternative that overcomes these two difficulties, it was proposed some time ago to produce seam coverings based on flat woven fabrics. These are described, for example, in EP 0 425 523 or EP 2 788 546. With a flat woven fabric, the ends are folded over each other, creating a two-layered structure. The folds can be formed into seam loops by removing CD threads – which correspond to weft threads on a loom. The two end faces of the double-layered structure can be joined by interlocking the seam loops and connecting them with a wire.

[0005] This concept has proven very successful in recent years, as it allows for the rapid production of the flat fabric and its storage on rolls. Upon receipt of an order, the desired length can then be cut from these rolls and also trimmed to the required width.

[0006] However, for some applications, the relative inflexibility of this concept has proven to be a disadvantage. Both layers of the two-layer structure consist of the same fabric. This leads, firstly, to so-called moiré effects due to the overlapping. Secondly, the different requirements for the running side and the paper side cannot be met.

[0007] To avoid these problems, DE102016111769 proposes changing the weave pattern of the flat fabric during the weaving process so that the two layers of the two-layered structure each have a different weave pattern. This can reduce moiré effects. However, the change in weave pattern must occur at the fold point, meaning that the length of the fabric must again be known during the production of the basic structure.

[0008] It is therefore the object of the present invention to overcome the problems of the prior art.

[0009] In particular, it is an object of the present invention to propose a basic structure and its manufacturing process which allows both great flexibility in the design of the covering and whose components can nevertheless be manufactured largely independently of the dimensions of the covering.

[0010] The problems are completely solved by a basic structure according to claim 1 and a method for producing a basic structure according to claim 10.

[0011] Advantageous embodiments are described in the dependent claims.

[0012] With regard to the basic structure, the problem is solved by a basic structure of a covering for a machine for the production or processing of a fibrous web, in particular a paper, cardboard or tissue web according to claim 1.

[0013] The basic structure therefore comprises at least four elements. The first and second flat fabrics typically constitute the largest part of the basic structure. They are essentially manufactured as homogeneous fabrics and can advantageously be produced as roll goods, independent of the dimensions of the subsequent covering, and cut from the roll as needed during the covering process.

[0014] The change between fabric type A and fabric type B in the basic structure occurs, as in DE102016111769, at the folding point. In contrast to this prior art, the basic structure of the present invention comprises a separate loop element in which the folding takes place. These loop elements are essentially independent of the length of the subsequent covering and can be produced and stocked in standardized formats.

[0015] Thus, the basic structure can be manufactured from elements that can be pre-produced either as roll stock or as standardized loop elements. Nevertheless, the invention allows the flexibility to realize the two layers of the two-layer structure with different fabric types. This allows moiré effects to be avoided or at least reduced, and accommodates the different requirements of the paper side and the running side.

[0016] As described, a piece of flat fabric is folded to form a loop element. This creates a fold at one end of the loop element. At the other end of the loop element, the two end edges of the original piece of flat fabric come to rest. One end edge is of fabric type A and the other is of fabric type B.

[0017] The first and second sections can be of the same length. However, it is often advantageous for these two sections to have different lengths. Preferably, the length ratio is between 40% / 60% and 30% / 70%. For example, in a flat woven fabric piece with a length of 2 m, the first section can be 1.20 m long and the second section 0.80 m long.

[0018] The different lengths have the advantage that when folding later, the front edges do not lie directly on top of each other, but are offset.

[0019] The flat woven fabrics and flat woven pieces used are typically woven from threads that consist entirely or partially of a polymer material. Common materials include polyamides, polyesters, and polyethylenes.

[0020] It is particularly advantageous if, in the first loop element and / or the second loop element, the front edge of the fabric type A is connected to the first flat fabric, and the front edge of the fabric type B is connected to the second flat fabric, in particular welded.

[0021] Connecting the loop elements to the first and second flat fabrics creates a cohesive basic structure. This makes it easier to process into a covering. Furthermore, such a basic structure not only provides lateral stability but can also absorb tensile forces.

[0022] With this type of connection, it is very advantageous that one side of the basic structure consists exclusively of tissue type A, and the other side exclusively of tissue type B.

[0023] Such a connection is also called a 'join'. To achieve a basic structure and a covering with the most homogeneous properties possible, it is usually helpful if properties such as permeability or thickness in the join area are largely aligned with the properties outside this joint zone, so that they lie, in particular, between 80% and 120% of the corresponding values ​​outside the joint zone. Methods for implementing such joins are described, for example, in document WO 2019 / 063518.

[0024] Furthermore, it can be advantageously provided that CD threads are removed in the area of ​​the fold points of the loop elements, forming seam loops, with in particular 3 to 8 CD threads being removed per fold point.

[0025] If such seam loops are formed on both sides of the two-layer structure, they can be guided into each other and connected using a plug wire, making the basic structure or the entire covering endless.

[0026] To allow for easy threading of the plug wire, a large inner diameter of the seam loops is desirable.

[0027] To determine the inner diameter of a seam loop, the largest circle that can be completely inserted into the seam loop is identified. The diameter of this circle is then considered the inner diameter of the seam loop.

[0028] However, an excessively large diameter results in very thick seam loops, which can potentially create marks in the fiber web. It has proven advantageous for the inner diameter of the seam loops to be between 0.8 mm and 2.2 mm, preferably between 1 mm and 1.6 mm.

[0029] The inner diameter of the seam loop is strongly influenced by the number of CD threads removed to form the loop. The desired inner diameters described are usually quite easy to achieve by removing 3-8 CD threads. Removing only one or two CD threads will result in smaller diameter seam loops in many applications. Removing more than eight threads risks making the seam loop diameter too large.

[0030] The loop inner diameter also depends on the yarn diameter of the MD threads. The range [0.8–2.2 mm] is particularly relevant for MD threads with diameters between 0.3 mm and 0.6 mm. Such MD threads are typical for the base fabric of paper machine coverings. With different yarn diameters, loop inner diameters outside the specified range are also possible.

[0031] Furthermore, it can be advantageous to include CD threads (special threads) in the immediate vicinity of the seam loops, threads that are not present in either fabric type A or fabric type B. These special threads can either be woven into the flat woven piece already or added subsequently during the formation of the seam loops. Since the position of the seam loop in the final loop element—namely, at the transition between fabric type A and fabric type B—is already determined when creating the flat woven piece for the loop elements, weaving in the special threads during the production of the flat woven piece is easily accomplished. Examples of possible special threads include yarns, multifilaments, or threads with a non-round cross-section, such as flat threads. Special threads can also be provided in the form of absorbent threads.In particular, the special threads can correspond to the other CD threads of the same fabric type in material and shape, but through appropriate measures such as the addition of an absorber additive for light in a specific wavelength range—especially in a section of the NIR range between 780 nm and 1200 nm. Such absorbing CD threads can be welded to the MD threads using laser transmission welding. This gives the seam loops a certain degree of stability. Since MD threads—especially if they are made of polyamide—do not absorb the laser light, they are only heated during welding through contact with the CD threads. Therefore, their strength is not significantly affected.

[0032] Alternatively or additionally, such special threads can also be used at other points on the flat woven fabric pieces or the loop elements. Particularly at or in the immediate vicinity of the end-face edges, such special threads, in the form of absorbent threads, can be very advantageous. This simplifies the joining of the loop elements to the flat woven fabric pieces by welding. Here, too, it proves advantageous that the location of the join is already known when weaving the flat woven fabric pieces for the seam loops. Thus, the special threads—which are usually more expensive—only need to be woven in where they are actually required.

[0033] A fabric which is modified by weaving or otherwise providing individual marker threads or other special threads - in particular fewer than 10 - into a fabric of type A (or B) shall continue to be regarded as a fabric of type A (or B).

[0034] Advantageously, fabric types A and B can differ in at least one parameter, in particular having a different weave pattern or a different CD thread density. This allows for particularly high flexibility in the design of the covering. However, this is not mandatory. In alternative embodiments, fabric type A can also be identical to fabric type B. Such basic structures are also possible according to one aspect of the present invention.

[0035] In some designs, it can be advantageous for the basic structure to comprise several flat fabrics of fabric type A and / or several flat fabrics of fabric type B. In particular, a basic structure can be built from six elements: two flat fabrics each of fabric types A and B, and two loop elements.

[0036] Preferably, the fabric type A and / or the fabric type B may have an MD thread density between 30% and 45%, in particular between 34% and 42%, specifically between 36% and 40%.

[0037] It is particularly advantageous for both fabric types to have the same MD thread density, either entirely or to a large extent. This is beneficial from a production standpoint. The flat fabrics for the loop elements can be produced on a single loom, and both fabric types utilize the same warp threads, which then provide the MD threads in the basic structure. At the transition point between the two fabric types, the weave pattern or the weft thread material can be changed relatively easily. Changing the warp threads, however, is very difficult. Furthermore, this also makes it easier to interlock the seam loops formed by the MD threads at the folds, thus facilitating the creation of a continuous basic structure.

[0038] The (MD) thread density indicates what proportion of the width of the fabric is occupied by (MD) threads.

[0039] For example, if 8 threads per cm are planned and one thread has a diameter of 0.4 mm, then the thread density is (8*0.4) / 10 = 32%.

[0040] The specified range of MD thread density allows for relatively easy interlocking of the seam loops. It's important to remember that in the area of ​​this seam, the MD threads of both seam loops create a loop density that is twice the MD thread density. With an MD thread density of 45%, this results in a loop density of 90%. This is already close to the theoretical maximum density of 100%. Loop densities even higher than 90% are very difficult to manage and therefore not advantageous. On the other hand, an MD thread density below 30% is not critical from the perspective of loop density. However, the fabric's properties, such as tensile strength, typically suffer so significantly that this value should generally not be undercut without risking other disadvantages.

[0041] Fabrics for paper and pulp machines, as well as their base structures, are frequently subjected to thermal treatment in a so-called "heatsetting" process. Typically, the warp thread density in the finished fabric or base structure is higher than before heatsetting due to the resulting shrinkage. The specified ranges for MD thread density are advantageous for fabrics both before and after heatsetting. With regard to the fabric, the problem is solved by a fabric, in particular a seam felt, for a machine for the production or processing of a fibrous web, especially a paper, board, or tissue web, wherein the fabric comprises at least one base structure according to an aspect of the invention.

[0042] The covering may also include other components.

[0043] The covering is often further enhanced with additional elements, such as non-woven overlays, additional fabric elements, films, or foam elements. This depends on the intended use of the resulting covering. In particular, one or more layers of non-woven fibers may be incorporated on the side of the covering that contacts the fiber web. Non-woven fibers may also be incorporated on the running side.

[0044] The nonwoven fibers are typically bonded to the base structure by needling. This is particularly advantageous because it also bonds the individual components of the base structure together, further increasing the strength of the covering.

[0045] With regard to the method, the problem is solved by a method according to claim 10.

[0046] In advantageous embodiments, the method may also include the step: d) connecting the loop elements to the first and second flat fabric, such that the end-face edge of the fabric type A of the first loop element and the second loop element is connected, in particular welded, to the first flat fabric, and the end-face edge of the fabric type B is connected to the second flat fabric.

[0047] When carrying out the process, it should be noted that the order of the process steps can be reversed if necessary. For example, connecting the loop elements or the flat fabric pieces to the first / second flat fabric is possible both before and after folding and shaping the loop elements.

[0048] Furthermore, advantageous embodiments of the process may include one or more heat-setting steps. Numerous variations are conceivable here.

[0049] The first flat fabric can thus be subjected to heat setting before and / or after being prepared in step a).

[0050] Alternatively or additionally, the second flat fabric can be subjected to heat setting before and / or after being provided in step a).

[0051] Alternatively or additionally, the flat woven pieces from which the loop elements are formed can also be subjected to heat setting before and / or after being prepared in step b). For example, it may be advantageous if the fabric of the flat woven pieces is pre-produced in the form of a roll of material, and this woolen material is already subjected to heat setting before the individual flat woven pieces are cut off.

[0052] Further advantageous features of the invention are explained using exemplary embodiments with reference to the schematic drawings. Figure 1a and 1bshow a flat fabric piece or a loop element according to one aspect of the invention. Figure 2 shows a basic structure according to one aspect of the invention Figure 2a shows a basic structure according to another aspect of the invention Figure 3 shows a fabric for use in a process according to a further aspect of the invention

[0053] Figure 1aFigure 6 shows a flat woven fabric piece 6 that can serve as the basis for manufacturing a loop element 2. The flat woven fabric piece 6 consists of a first section 6a, which is of fabric type A, and a second section 6b, which is of fabric type B. It may be advantageous for fabric type A and fabric type B to differ in at least one parameter, in particular a different weave pattern or a different CD thread density. From a manufacturing perspective, it is very advantageous if both fabric types have the same MD thread density. It may also sometimes be possible for fabric type A to be identical to fabric type B.

[0054] To ensure high flexibility in the production of basic structures 1 or coverings, the flat fabric piece should have a short length in MD compared to the basic structure. In particular, the flat fabric piece 6 can be shorter than 5 m, preferably 2 m or shorter.

[0055] The first section 6a and the second section 6b can be of the same length. However, it is often advantageous for these two sections 6a and 6b to have different lengths. Preferably, the length ratio is between 40% / 60% and 30% / 70%. For example, in a flat woven fabric piece 6 with a length of 2 m, the first section 6a can be 1.20 m long, and the second section 6b 0.80 m long.

[0056] The different lengths have the advantage that, when folding later, the end edges 3a, 3b do not lie directly on top of each other, but are offset.

[0057] To form a loop element 2 from a piece of flat fabric 6, the piece of flat fabric can be folded and laid on top of itself. This is shown in Figure 1bshown. The fold point 4 is located in the area of ​​the transition point 60, specifically at the transition point 60. To form seam loops 5, which serve to later make the basic structure 1 or the covering continuous, CD threads can be removed at the fold point. Often it is sufficient to remove between 3 and 8 CD threads. The CD threads can be removed from fabric type A and fabric type B. However, if, for example, removal from one fabric type is more complicated than from the other, CD threads can be removed from only one fabric type. If, as in Figure 1b As shown, the two sections 6a, 6b have different lengths, so the end-face edges 3a, 3b do not lie on top of each other, which can be advantageous for later processing.

[0058] The two layers of the loop element 2 can advantageously be joined together. Such a connection can be made, for example, by one or more stitched joints 7. Such joining or sewing is advantageous, among other reasons, because the two layers of the loop element 2 cannot be displaced relative to each other during further processing.

[0059] A connection in the area of ​​the seam loop 5, for example at a distance of less than 2 cm from the seam loop 5, can also be advantageous to fix the seam loop 5 and later to make it easier to interlock two seam loops 5 to make the basic structure 1 endless.

[0060] Figure 2Figure 1 shows a basic structure 1 according to one aspect of the invention. This basic structure is formed from a first flat fabric 10 of fabric type A and a second flat fabric 20 of fabric type B, as well as two loop elements 2a, 2b. The loop elements 2a, 2b can be configured in particular as shown in Figure 1. Figure 1a , or as described in 1b.

[0061] The first flat fabric 10 and the second flat fabric 20 are arranged one above the other. Similar to the loop elements 2, 2a, 2b, these two layers 10, 20 can also be connected to each other, in particular sewn together. The sewn connections 7 are in Figure 2 They are not explicitly shown, but may still be present.

[0062] To form a coherent basic structure 1, the four components in Figure 1 are connected to each other.

[0063] In the loop elements 2a and 2b, the end edge 3a of fabric type A is connected to the first flat fabric 10, and the end edge 3b of fabric type B is connected to the second flat fabric 20. This connection 8 can be made, in particular, by means of a weld 8. The welding can be carried out, for example, by laser welding, in particular by laser transmission welding, or by ultrasonic welding. Alternatively or additionally, the connection 8 can also be made by means of an adhesive bond or a stitched connection.

[0064] The resulting basic structure 1 has two seam loops 5a, 5b. By joining these seam loops 5a, 5b together and subsequently inserting a connecting wire, the basic structure 1 can be made endless. Often, the basic structure 1 is further modified before (or even after) being made endless, with additional elements such as non-woven fabric overlays, additional woven fabric elements, films, or foam elements. This depends on the intended use of the resulting covering.

[0065] While a basic structure consists of four woven elements, as in Figure 2 Although depicted as generally advantageous, it is nevertheless possible and intended that the basic structure be built from more elements. An example of this is in Figure 2a shown. The basic structure 1 shown there differs from the basic structure 1 from Figure 2by having, in addition to the first flat fabric 10 and the second flat fabric 20, a further first flat fabric 11 and a further second flat fabric 21. The two flat fabrics of the same fabric type can also be joined together in a suitable manner, for example with a weld seam 8a. This can be advantageous, for example, if the flat fabrics are not available as virtually endless rolls, but as pre-fabricated pieces of fabric of a fixed length. In such a case, it may also be necessary, in addition to the first (second) flat fabric 10 (20) and the further first (second) flat fabric 11 (21), to construct the basic structure in an analogous manner.

[0066] Using the example of Figure 3One of the advantages of the coverings according to one aspect of the invention will be explained again. By separating the loop elements 2, 2a, 2b from the flat fabrics 10, 20, it is possible to produce these woven parts of the basic structure 1 without needing to know the dimensions of the subsequent covering. Figure 3 The diagram shows a fabric where the weft direction of the loom corresponds to the CD direction of the later warp, and the warp direction to the MD direction. In the CD direction, the fabric can be produced at the maximum width of the available loom to meet as many width requirements as possible for the future warp. If narrower warps are desired, this can be achieved by appropriate cutting. The resulting waste also occurs with modern manufacturing methods and does not represent a specific disadvantage of the present idea.

[0067] In the MD direction, fabric types A and B alternate in a regular pattern. This is based on the length of the flat woven pieces 6 required later for the loop elements, along with the desired length ratio of fabric types A and B. For example, the flat woven pieces 6 may be 2 m long, with the first section 6a being 1.2 m long and the second section 6b being 80 cm long. The flat woven pieces 6, as well as sections 6a and 6b, can also be longer or shorter. In any case, the fabric can be... Figure 3The fabric types A and B are pre-produced as roll goods with regular alternation. To produce a basic structure 1, two flat fabric pieces 6 can be taken from this roll and loop elements 2, 2a, 2b formed from them. The length required for the specific order, or the basic structure 1, can then be adjusted independently of the loop elements by selecting a suitable length for the first flat fabric 10 and the second flat fabric 20. Reference symbol list

[0068] 1 Basic structure 2, 2a, 2b Loop element 3a, 3b Front edge 4 Fold point 5 Seam loop 6 Flat fabric piece 6a First section 6b Second section 7 Sewn joint 8 Weld seam 10, 11 First flat fabric 20, 21 Second flat fabric 60 Transition point

Claims

1. Basic structure (1) of a fabric for a machine for producing or processing a fibrous web, comprising at least a first flat fabric (10, 11) of fabric type A and a second flat fabric (20, 21) of fabric type B, wherein the basic structure further comprises two loop elements (2, 2a, 2b), wherein the loop elements are each formed from a piece of flat fabric (6) having a first section (6a) of fabric type A and a second section (6b) of fabric type B, and the flat fabric piece (6) is folded to form a loop element, forming a fold (4), wherein, in the event that the fabric types A and B differ in at least one parameter, the first section (6a) is placed on the second section (6b) such that the fold (4) is formed at a distance of less than 5 cm, in particular less than 1 cm, from the transition point (60) between fabric type A and fabric type B, and wherein the first (10, 11) and second flat fabrics (20, 21) are arranged one above the other and the two loop elements (2, 2a, 2b) are each arranged at one end face.

2. Basic structure according to claim 1, characterised in that, in the first loop element (2a) and / or the second loop element (2b), the front edge (3a, 3b) of fabric type A is connected to the first flat fabric (10, 11) and the front edge (3a, 3b) of fabric type B is connected to the second flat fabric (20, 21), in particular via a weld seam (8).

3. Basic structure according to one of the previous claims, characterised in that CD threads are removed in the area of the fold points (4) of the loop elements (2, 2a, 2b), forming seam loops (5).

4. Basic structure according to claim 3, characterised in that CD threads are provided in the immediate vicinity of the seam loops (5), which do not occur in either fabric type A or fabric type B.

5. Basic structure according to one of the previous claims, characterised in that fabric type A is the same as fabric type B.

6. Basic structure according to one of claims 1 to 4, characterised in that fabric types A and B differ in at least one parameter, in particular in that they have a different weave pattern or a different CD thread density.

7. Basic structure according to one of the previous claims, characterised in that the basic structure comprises several flat fabrics of fabric type A and / or several flat fabrics of fabric type B.

8. Basic structure according to one of the previous claims, characterised in that fabric type A and / or fabric type B has an MD thread density between 30% and 45%, in particular between 34% and 42%.

9. Fabric comprising at least one base structure (1) according to one of the preceding claims.

10. Method for producing a base structure (1) according to one of claims 1 to 8, wherein the method comprises the steps of: a) providing a first flat fabric (10, 11) of fabric type A and a second flat fabric (20, 21) of fabric type B, b) providing two pieces of flat fabric (6) which have a first section (6a) of fabric type A and a second section (6b) of fabric type B, and forming loop elements (2, 2a, 2b) by placing the first section (6a) on top of the second section (6b) to form a fold (4), wherein - in the event that fabric types A and B differ in at least one parameter - the fold (4) is formed at a distance of less than 5 cm, in particular less than 1 cm, from the transition point (60) between fabric type A and fabric type B; c) arranging the first (10, 11) and second flat fabrics (20, 21) on top of each other and the two loop elements (2, 2a, 2b) at each end face.

11. Method according to claim 10, characterised in that the method also comprises the step of: d) connecting the loop elements (2, 2a, 2b) to the first flat fabric (10, 11) and the second flat fabric (20, 21) by means of a sewing connection (7) or weld seam (8).

12. Method according to one of claims 10 or 11, wherein in method step b) CD threads are additionally removed in the area of the fold points (4) of the loop elements (2, 2a, 2b) to form seam loops (5), wherein in particular 3 to 8 CD threads are removed per fold point.