Method, base structure and structure

Abstract

The invention relates to a method for thermally fixing a seam loop of a base structure of a stretched web, in particular of a seam mat of a paper machine, comprising the following steps: a. Providing a flat fabric comprising longitudinal threads and transverse threads, in particular subjected to a first thermal fixing process, b. Folding the flat fabric into a two-layer structure at at least one folding point, the invention relates to a method for thermally fixing a joint loop, in which the joint loop is formed at a respective folding point, c. A plug wire is introduced into the joint loop, characterized in that d. The plug wire is designed as an electrically conductive plug wire and the electrically conductive plug wire is heated by applying a voltage in order to thermally fix the joint loop.

Description

Technical Field

[0001] The invention relates to a method for producing a basic structure of a fabric, in particular a seaming felt, for a paper machine. The invention also relates to the resulting basic structure and to a fabric having such a basic structure. Background Art

[0002] Woven structures are usually used in the wires of paper machines. Thus, press felts, for example, usually comprise a woven base structure (base fabric) on which one or more layers of nonwoven fibers are arranged.

[0003] Here, for a long time, it was necessary to produce circularly woven, annular fabric loops, which was associated with a complex and long weaving process. In order to avoid annular weaving, Sudre proposed a method in EP0425523, in which, in a flat fabric, two ends are placed on each other, thereby forming a two-layer fabric piece. The edges of the two end sides of the fabric piece are usually appropriately connected to each other. Seam loops are produced at the folding position, which can be staggered with each other and connected by means of plug wire. In this way, a fabric loop with a plug wire seam is produced, which can be used as the basic structure of the seam felt.

[0004] As an improvement of this method, it is proposed in EP2788546 B1 to remove some transverse yarns from the fabric at the folding position. This produces a larger seam loop, which significantly promotes the formation of the plug-in thread seam.

[0005] A further development is known from patent document DE 10 2019 121 485. Here, the basic structure is built up from a plurality of modules, wherein two seaming loop modules are each generated by a single folding of a flat fabric. These seaming loop modules are then usually connected to further flat fabric pieces to form a two-layer fabric piece. In this way, more economical production is possible, since the fabric and the seaming elements can be produced independently of the size of the subsequent web.

[0006] Nowadays, in the production of the above-mentioned structures, the flat fabric is usually already thermally pre-fixed on a fixing device arranged downstream of the weaving machine. As a result, the stresses in the fabric yarns caused by weaving are relieved and the yarns are also deformed. The fabric yarns taken out of the fabric after pre-fixing are no longer straight, but have a wavy shape.

[0007] If a seam mat is to be made of these fabrics, the fabrics are first connected to form an endless belt and the weft or transverse threads are usually removed at two locations of the fabric belt. Seam loops are formed at these locations for inserting the thread seam. In this case, the seam area is usually fixed by sewing the seam. However, the seam loops formed by the yarns / monofilaments extending in the machine direction still have waves or warps caused by the fixing of the fabric structure. This only conditionally allows the formation of an effective patch wire seam. In practice, the patch wire seam of the fabric is closed with the patch wire provided for this purpose, and the entire fabric is thermally fixed again in a second fixing process. In this process, the deformation caused by the warping of the fabric can be eliminated and cleanly formed seam loops are obtained, which are adapted to the cross section of the patch wire. Therefore, a relatively simple opening and closing of the patch wire seam is possible.

[0008] This re-fixing process is carried out under stress with rollers on the stretching system and requires a long heating of at least one oil-heated roller to a temperature of up to 140-170° C. The process time for weaving is about 30-60 minutes plus a preparation time of about 30 minutes. High energy consumption and occupation of the heat fixing equipment are associated with this process.

[0009] Furthermore, during this process, the region of the seam loop is exposed to different thermal conditions depending on whether it is arranged on the side facing or facing away from the heated roller. This leads to inhomogeneities in the material properties of the seam loop. Summary of the invention

[0010] The object of the present invention is to further improve the production process known from the prior art.

[0011] It is an object of the present invention, in particular, to reduce the energy required for production.

[0012] A further object of the invention is to increase the productivity of existing machine shops in the production of the described structures.

[0013] Finally, it is an object of the invention to improve the quality of the seam loops.

[0014] These objects are achieved according to the invention by a method according to independent claim 1 and by a base structure produced thereby and a fabric using such a base structure.

[0015] Further advantageous embodiments of the invention are found in the dependent claims.

[0016] With regard to the method, the object is achieved by a method for thermally fixing seam loops of a basic structure of a web, in particular a seam felt of a paper machine, the method comprising the following steps:

[0017] a. providing a flat fabric comprising longitudinal yarns and transverse yarns, wherein the flat fabric has undergone a first heat fixing process,

[0018] b. folding the flat fabric into a two-layer structure at at least one folding location to form a seam loop at each folding location,

[0019] c.Introduce the plug wire into the joint circle,

[0020] According to the present invention, it is also provided that

[0021] d. The plug wire is designed as an electrically conductive plug wire, and the electrically conductive plug wire is heated by applying a voltage in order to thermally fix the seam loop.

[0022] The inventors have recognized that the thermal fixing of the fabric in the second fixing step has no significant significance for the function of the basic structure. The second fixing step is only used to improve the structure of the seam or the seam loop. Therefore, the heating of the basic structure can also be limited to the area of ​​the seam loop. This can achieve a fundamental change in the heating process. Instead of introducing energy into the seam loop from the outside via heated rollers as has been done so far, in the method according to the invention, energy is introduced into the seam loop from the inside. This occurs with the aid of an electrically conductive plug wire, which is introduced into the seam loop. By applying a voltage, an electric current flows through the plug wire, whereby the plug wire heats up and, in turn, the yarn of the seam loop or loops surrounding the plug wire heats up.

[0023] The heat generated here spreads largely uniformly in the seam loop, since the patch cord runs centrally in the seam loop. Since the current through the conductor is constant at all locations, the same electrical heat loss occurs at every location of the entire patch cord with a constant resistance over the entire length of the cord. This in principle enables a very locally limited uniform heat distribution in the seam loop and uniform and synchronous heating of all seam loops of the patch cord seam.

[0024] Thus, deformations produced by warping of the fabric can be removed and cleanly shaped seam loops are obtained, which are adapted to the cross section of the plug wire.

[0025] In contrast to the prior art, the prolonged heating of at least one oil-heated roller to a temperature of up to 140-170° C. is omitted. The process time for weaving is reduced from 30-60 minutes plus a preparation time of about 30 minutes to a few minutes. Thus, in the method according to the invention, the time of the heat treatment is usually between 90 seconds and 10 minutes, in particular between 2 minutes and 5 minutes. In addition, only a small amount of energy is required for the process proposed within the scope of the invention, since the heating of the hot rollers can be omitted.

[0026] The described process is also advantageous in particular when using fabrics with two different fabric types, wherein the transition of fabric types is achieved in the region of the plug-in wire seam. Such a structure is described, for example, in US 2009 / 0090425. In this case, the heat fixing process used so far must be spliced ​​into an endless belt in advance and heat fixed with a closed plug-in wire seam. With two different fabric types in the belt, this leads to the problem that the heat fixing process cannot be optimized for both fabric types at the same time.

[0027] The method according to several aspects of the invention can be performed both for individual seaming modules as described in DE 10 2019 121485 and for an integral two-layer fabric loop as known, for example, from EP 2 788 546 B1. In the second case, it is advantageous to implement steps b. and c. as follows:

[0028] b. folding the flat fabric into a two-layer structure at two folding locations to form two seam loops at the respective folding locations, and connecting the edges of the two end sides of the flat fabric to each other,

[0029] c. The two seam loops are staggered with each other and connected by introducing a plug wire to form a two-layer fabric loop;

[0030] In this case, two seam loops can be heat-fixed simultaneously.

[0031] Advantageously, the closed plug wire seam can be slightly tensilely stressed in the longitudinal direction (=machine direction) during the heat treatment. This improves the contact of the seam loop with the conductive plug wire.

[0032] It is sometimes also advantageous to widen the fabric in the seam area during heat fixing and this can be achieved by clamping the fabric edges.

[0033] Alternatively, however, the respective fabric ends equipped with seam loops can also be treated individually in principle by introducing a conductive plug wire into the seam loops present at the fabric ends and carrying out a heat treatment of the seam loops when the seams are not closed.

[0034] It is often advantageous if the method further comprises the following steps:

[0035] a2. Removing multiple adjacent transverse yarns in the area of ​​the folded portion

[0036] In particular, step a2. can be carried out between steps a. and b.

[0037] By removing the transverse threads, the position of the fold is clearly defined and visible on the one hand, which simplifies the subsequent folding.

[0038] The resulting window also results in a larger seam loop, which further simplifies the introduction of the plug wire.

[0039] By adjusting the voltage, the current and thus the heat loss and thus the temperature of the plug wire can be adjusted very easily and in a targeted manner.

[0040] However, for most conductive plug wires, the resistance increases with increasing temperature. If these plug wires are used, the temperature of the plug wire or the seam ring can be controlled by means of a temperature-controlled voltage regulation and thus a temperature control program can be achieved during the heat treatment.

[0041] It can therefore be advantageous to provide at least one sensor for detecting the temperature of the electrically conductive plug wire and / or the seam loop, wherein the detected temperature value is used in particular for regulating the voltage.

[0042] For example, contactless infrared sensors are suitable.

[0043] With the method according to an aspect of the invention, defined temperature heating ramps and cooling ramps can also be implemented before and after the heat treatment at the target temperature. This is not possible or only conditionally possible with the methods known from the prior art. In the prior art, the hot rollers can also be moved with a preset temperature curve, limited by the inertia of the roller temperature. However, the base fabric must be moved on the hot rollers and therefore cools down in each cycle and heats up again when it comes into contact with the hot rollers again. If the heat treatment is carried out in a belt cycle, the heating ramps and cooling ramps are also fixedly preset, and the fabric cools down after leaving the hot rollers under the influence of the ambient temperature.

[0044] Firstly, the cooling rate has a strong influence on the morphology of the material after heat treatment, and targeted control of the cooling ramp allows the optimization of the material parameters in the joint ring.

[0045] In the method according to various aspects of the invention, cooling can be achieved in a very targeted manner (optionally monitored by temperature measurement) by reducing the voltage.

[0046] Alternatively, plug wires with a largely temperature-independent resistance, such as constantan wires or stranded or braided wires containing constantan wires, can be used. Temperature monitoring can possibly be omitted here.

[0047] In the context of this application, the term "wire" or "plug wire" is to be understood very broadly. As is common in the context of paper machine wires, the term is also used for "plastic wires", ie thicker plastic filaments, in addition to metal wires.

[0048] In the methods according to different aspects of the invention, the electrically conductive plug wire can be realized in different ways.

[0049] So for example it is possible that

[0050] i. The electrically conductive plug wire is embodied as a metallic plug wire.

[0051] ii. The electrically conductive plug wire is embodied as a metal plug wire with a polymer coating.

[0052] iii. The electrically conductive plug wire is embodied as a polymer wire coated with a conductive material, in particular a metal.

[0053] iv. The electrically conductive plug wire is implemented as a polymer wire comprising conductive particles.

[0054] v. The electrically conductive plug wire is embodied as a polymer wire which comprises an electrically conductive polymer or consists of an electrically conductive polymer.

[0055] Suitable metals for the plug wire or the coating are, for example, copper, silver, gold or alloys, in particular alloys such as (Constantan), (Manganese Copper) or The resistance varies only slightly with temperature.

[0056] Suitable polymers for the polymer wire are, for example, polyamide or PET. Ideally, the melting point of such a polymer is much higher than the temperature used in the heat treatment of the seam loop.

[0057] Independent of the choice of material for the plug wire, the construction is identical. For example, it is possible that

[0058] I. The electrically conductive plug wire is a single wire which has, in particular, a perfectly circular cross section.

[0059] II. The electrically conductive plug wire is embodied as a strand of a plurality of yarns, wherein the strand may in particular consist exclusively of electrically conductive yarns or may consist of a combination of electrically conductive yarns and non-conductive yarns.

[0060] III. The electrically conductive plug wire is embodied as a braided structure, in particular as a braided wire or a cord, wherein the braided structure may in particular be formed exclusively from electrically conductive yarns or may be composed of a combination of electrically conductive yarns and non-conductive yarns.

[0061] IV. The electrically conductive plug wire is embodied as a stranded wire or a braided structure, wherein the individual threads are not electrically conductive, but the stranded wire or the braided structure as a whole is coated with a conductive material, in particular a metal.

[0062] The electrically conductive plug wire can be constructed from only conductive single wires, or can also be constructed from already twisted yarns. However, it is also possible to include non-conductive single wires in the twisted wire or braided wire.

[0063] Likewise, the conductive individual wires can consist completely of an electrically conductive material or contain a certain proportion of a polymer. Thus, the individual wires can consist, for example, of a polymer, wherein the conductive material is added inside or in the form of a coating, or they can consist of a metal yarn coated with a polymer.

[0064] By making part of the patch wire cross section from non-conductive material, the effective cross section of the conductive material in the patch wire and thus the resistance of the patch wire can be adjusted. This avoids too low a resistance and the associated high current flow in the case of larger patch wire diameters.

[0065] Whether the electrically conductive plug wire is made completely of conductive material can also be selected depending on the diameter of the seam loop to be achieved and thus on the required diameter of the plug wire. Typical plug wire diameters are between 0.2 mm and 2.5 mm, preferably between 0.5 mm and 2.0 mm.

[0066] When selecting the best electrically conductive plug wire, many aspects play an important role, of which preferably at least some, and ideally all, should be satisfied.

[0067] i. The diameter of the plug wire should be close to the diameter of the seam ring. Usually, the diameter of the seam ring and thus the plug wire is between 1.1mm and 1.8mm; especially 1.55mm

[0068] ii. The resistance of the plug wire should be between 0.5Ω / m and 200Ω / m at room temperature, especially between 1Ω / m and 50Ω / m.

[0069] iii. The patch cord should be able to withstand bending stresses without plastic deformation. This is important in order to avoid buckling in the joint.

[0070] iv. Integrity of the patch cord. The patch cord should function as a unit, even when the patch cord is composed of multiple individual yarns. A known problem is the formation of "wire nests," where individual yarns from the patch cord become twisted or entangled and form a nest or knot. As a result, it is difficult to pull in and remove the patch cord.

[0071] v. The tensile strength of the patch wire should be greater than 50 N, in particular greater than 100 N. This is also advantageous because the patch wire can be simply pulled out again after the heat treatment of the seam loop without the risk of the patch wire tearing in the process and not having parts remaining in the seam loop and then having to be removed in a complex manner.

[0072] vi. The material should remain stable over a wide temperature range, thus for example between room temperature (20° C.) and 190° C. In this context, “stable” means that properties such as deformation, dimensional stability, conductivity or aggregation state do not change or change only within a small range.

[0073] These properties cannot be achieved using a simple single wire.

[0074] For example, a simple metal wire made of NiCr with a diameter of 1.55 mm satisfies i. and ii., but does not satisfy iii. (buckling!)

[0075] In contrast, monofilaments made of polymers cannot easily provide conductive properties.

[0076] Therefore, a more complex design of the patch cord often makes sense.

[0077] For example, the improvement of the metal single wire can be to use a metal stranded wire or metal rope-like patch cord made of a plurality of thinner metal yarns. This increases the flexibility of the patch cord produced. For the sake of simple readability, within the scope of this application, unless otherwise specified, the term "stranded wire" always also refers to a formation with multiple levels of twisting, such as a rope-like formation.

[0078] Possible wire-like patch cords are:

[0079] 34×7+FC(fiber core)

[0080] 34×7+IWS (“Independent Wire Core”)

[0081] 36×7+FC

[0082] 36×7+IWS

[0083] The individual metal wires of the ropes can in particular have a diameter of between 0.05 mm and 0.1 mm.

[0084] Alternatively, the patch cord may have a polymer core around which the metal yarn or braided wire is arranged.

[0085] Alternatively, it can be provided that the patch cord has a metal core (wire, braid, strand, in particular a rope), wherein the core is surrounded by a sheath made of a polymer material. Ideally, the polymer material is a good thermal conductor. The polymer sheath protects the metal core, prevents buckling, and facilitates pulling the patch cord in or out.

[0086] Depending on the required resistance, graphene, specific carbon filaments or sputtered / sprayed yarns are possible. Sputtered or sprayed polymer yarns have a metal coating, and the typical size of such yarns is usually very small (e.g. 0.1 mm), because the coating process for yarns with larger diameters and good electrical properties is inefficient. Therefore, a combination of sputtered / sprayed yarns is required to achieve the required patch cord diameter. The integrity of the patch cord requires that the combination of small coated yarns function as a unit, so the patch cord with coated polymer yarns can be composed of braids, ropes, braids made of multiple braids, cables, etc.:

[0087] An improvement in the conductive yarn may be a solid polymer core which may also be coated or remain uncoated. The solid polymer core may act as a tensile load carrier, but the stiffness of the outer braid or yarn may also be increased and the overall cost of the patch cord may be reduced.

[0088] The polymers used in the patch cord can be composed of polyamide, PET, PEEK and other materials within the preset temperature characteristics.

[0089] Using a polymer yarn system as a plug wire has surprising advantages for the heat fixing process. During the thermal cycle and depending on the temperature, the polymer yarn length is shortened and its diameter increases slightly. The increase in diameter can help to form a rounded, uniform seam loop. Ideally, the diameter increases during the thermal cycle and returns to the original diameter after cooling.

[0090] The process of thermally fixing the coil when using conductive plug wires can advantageously be regulated. The regulation can be either temperature-controlled or current-controlled via thermocouples. The thermocouples serve as a control feedback loop in order to regulate the current intensity of the circuit. The time-controlled thermal regulation can also be automated.

[0091] If the resistivity of the pins is known, the thermocouple can be omitted. The resistance of most conductive yarns is very stable over the specified temperature range (room temperature to 190C).

[0092] The following example shall illustrate the present invention in detail. However, the present invention is not limited to this example.

[0093] • Base fabric: a plain woven flat fabric with longitudinal and transverse yarns consisting of PA6.

[0094] · Diameter of MD yarn: 0.4 mm.

[0095] Diameter of conductive plug wire: 1.4 mm.

[0096] · The plug wire is implemented as Made of twisted wire.

[0097] The voltage is increased until the temperature of the plug wire reaches 150°C.

[0098] Duration of heat treatment: 2 minutes to 10 minutes, for example 5 minutes.

[0099] Then, the voltage is slowly reduced to zero (e.g. over 60 seconds)

[0100] Heat-fixing methods for textile fabrics have been described so far, in which the seaming loops are formed by folding the flat textile fabric.

[0101] In the classic production of seam fabrics, seam loops have hitherto been produced directly in the weaving machine. To this end, weaving threads ("weaving pintles") are pulled in on both sides of the weaving machine in the MD direction. The CD yarns are then woven around each of these weaving threads. After the weaving threads are removed, seam loops are formed, which can be interlaced with one another in a manner similar to the above-described method. These seam loops can also be thermally fixed using electrically conductive plug-in threads.

[0102] In particular, it is also possible here for the weaving pin to be embodied as an electrically conductive plug wire according to one of the above-mentioned aspects.

[0103] The method described above can be used for a variety of applications. Thus, for example, the method can be used to produce base fabrics for paper machine fabrics, such as base fabrics for seam felts, but also other fabric belts with plug-in wire seams, such as base fabrics for conveyor belts, transport belts, functional belts, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] The invention will be described in detail below with reference to the accompanying drawings. The invention is not limited to the variants shown in the accompanying drawings. These drawings show in detail:

[0105] Figures 1a to 1d The steps of a method according to one aspect of the invention are explained,

[0106] Figures 2a to 2d 1d explains the steps of a method according to a further aspect of the invention,

[0107] Figure 3 and Figure 4 A seam loop with a plug-in wire for carrying out the method steps according to different aspects of the invention is shown, DETAILED DESCRIPTION

[0108] Figures 1a to 1d The steps of the method according to one aspect of the invention are explained. First, a flat fabric 3 woven from longitudinal threads 4 and transverse threads 5 is provided. Unlike round fabrics, such a flat fabric 3 can be produced very quickly. After weaving, the flat fabric 3 is subjected to a heat setting process (“heat-setting”). As a result, the stress in the woven threads 4, 5 is removed, but these woven threads 4, 5 are also deformed.

[0109] For the method according to various aspects of the invention, a flat woven fabric can be used as the flat fabric 3. It is also conceivable that one or more parameters of the weaving pattern of the flat fabric 3 are changed. Such changes are usefully arranged at the future folding location.

[0110] exist Figure 1b In the example shown in FIG. 1 , transverse threads 5 have been removed around the folding point. Typically, 3 to 7 transverse threads 5 are removed. By removing the transverse threads 5, a so-called window 6 is formed in the flat fabric 3, in which the flat fabric 3 only has longitudinal threads 4. After the preparation of this window 6, the flat fabric 3 can be folded and formed into a two-layer structure by laying onto itself. This is done in Figure 1c As shown in FIG. Thus, a seam loop 2 is formed at the folded portion. By removing the transverse yarn 5 and forming the window 6, the seam loop 2 is essentially formed by the longitudinal yarn 4. This facilitates the introduction of the plug-in wire 1.

[0111] However, the longitudinal threads 4 are still deformed by the heat setting process. However, the rounded seam loops oriented in the plane are the basis for good seam tension. The deformation should be removed again by further heat treatment (if necessary in combination with a certain tension in the longitudinal direction).

[0112] In a method according to one aspect of the present invention, Figure 1dAs shown, for this purpose, an electrically conductive plug wire 1 is introduced into the seam loop 2. A voltage source 11 can then be connected to the electrically conductive plug wire 2. As a result, current flows through the electrically conductive plug wire 1. The plug wire becomes a resistor and heats up. The heated plug wire 1 heats up the longitudinal yarns 4 of the seam loop 2. Deformations in the longitudinal yarns 4 can thus be eliminated. In order to optimize the method, it is possible to use a temperature sensor, not explicitly shown in the drawing, which monitors the temperature of the seam loop 2. Based on the temperature value determined, the intensity of the voltage 11 can be adjusted. This can be done manually or in the form of an automatic control loop. In the method, energy is introduced in a targeted manner only in the area of ​​the seam loop 2. As a result, on the one hand, energy can be saved compared to conventional processes. On the other hand, by utilizing the Figures 1a to 1d The method described in EP 4010528 also makes it possible in particular to heat fix the seam loops of loop elements described in EP 4010528, which are present only as short loop elements with seam loops 2 and cannot be connected to form a closed endless belt.

[0113] Although in Figures 1a to 1d The method described in is suitable for heat fixing a single seam loop, but Figures 2a to 2d An alternative embodiment of the method is shown, in which the two seam loops 2 can be heat-fixed simultaneously (similar to conventional processes). Figure 2a In, as in Figure 1a As in the example, a flat fabric 3 is provided again, which comprises longitudinal threads 4 and transverse threads 5, wherein the flat fabric 3 has in particular undergone a first heat fixing process. In this case, in particular, the length of the flat fabric 3 is twice that of the later basic structure. Figure 2b As shown, by removing the transverse threads 5, windows 6 are now formed at two locations. These windows 6 have a distance in the longitudinal direction of the flat fabric 3 that corresponds to the length of the later basic structure. By folding the flat fabric 3 at two folding locations in the region of the two windows 6, a two-layer structure is produced, with two seam loops 2 being formed at the respective folding locations. The previous end edges of the flat fabric 3 are usually connected to each other, in particular welded.

[0114] like Figure 2c As shown, two seam loops 3 can be interlaced with each other and connected by means of plug wires. Thus, a closed two-layer endless belt is obtained.

[0115] like Figure 2d As shown, the plug wire can be implemented as an electrically conductive plug wire 1 in the method according to one aspect of the present invention. It is also provided that the electrically conductive plug wire 1 is heated by applying a voltage source 11 to thermally fix the two seam loops 2. Figure 2dAs can be seen in the figure, the two seam loops 2 are connected to the electrically conductive plug wire 1 and are thermally fixed simultaneously by heating the electrically conductive plug wire 1. A temperature sensor can be provided here again, and the voltage 11 can be adjusted by means of the measured temperature.

[0116] The heat fixation of the seam loop 2 in the form of a closed endless belt may be advantageous, because the desired preload can be applied to the seam loop very simply, for example. Therefore, within certain limits, the shaping of the seam loop 2 may be influenced.

[0117] There are various possible options for designing the electrically conductive plug wire 1. In principle, it is possible to implement the plug wire as a simple metal single wire 1, in particular with a perfectly circular cross section. However, this has the disadvantage that in electrical conductors, the electrical resistance decreases with increasing wire diameter, so that the wire heats up less. This is generally disadvantageous, in particular, in the case of seam loops 2 with larger loop diameters. As a possible alternative, Figure 3 The figure shows an electrically conductive plug wire 1 which is designed as a stranded wire 7. The stranded wire 7 is Figure 3 , which is composed of four yarns 8, wherein all four yarns are designed as electrically conductive yarns 8. The yarns shown here are plastic filaments which are covered with a conductive coating, in particular a metal coating. This has the advantage that the strands 7 themselves are electrically conductive, but the electrical resistance of the strands 7 is only slightly reduced even with a larger diameter, since the individual conductive yarns 8 have a non-conductive plastic core.

[0118] Another possible embodiment of the electrically conductive plug wire 1 is Figure 4 Here, the electrically conductive plug wire 1 is again implemented as a stranded wire 7 consisting of four individual yarns. However, the stranded wire 7 is here composed of a combination of a conductive yarn 8 and a non-conductive yarn 9. Figure 4 In the example of , there are two conductive yarns 7 and two non-conductive yarns 9. In general, however, other ratios and other numbers of yarns 8, 9 in the strand 7 are also possible. In this way, it can also be prevented that the electrical resistance of the conductive plug wire 1 decreases too much when the diameter increases. In this case, Figure 3 The metal-coated plastic filaments shown can again be used as electrically conductive yarns 8. However, alternatively or additionally, other electrically conductive yarns 8, for example metal individual wires, can also be used.

[0119] Reference numerals

[0120] 1 Conductive plug wire

[0121] 2 Seam loops

[0122] 3 Flat fabric

[0123] 4 Longitudinal yarn

[0124] 5 Transverse yarn

[0125] 6 Windows

[0126] 7 strands

[0127] 8 Conductive yarn

[0128] 9. Non-conductive yarn

[0129] 11 Voltage Source

Claims

1. A method for thermally fixing seam loops (2) of a basic structure of a web, in particular a seam felt for a paper machine, comprising the following steps: a. providing a flat fabric (3) comprising longitudinal yarns (4) and transverse yarns (5), wherein the flat fabric (3) has in particular undergone a first heat fixing process, b. folding the flat fabric (3) into a two-layer structure at at least one folding position to form a seam loop (2) at each folding position, c. introducing the plug wire (1) into the seam ring (2), It is characterized in that d. The plug wire (1) is implemented as an electrically conductive plug wire (1), and the electrically conductive plug wire (1) is heated by applying a voltage (11) to thermally fix the seam loop (2).

2. The method according to claim 1, characterized in that Steps b. and c. are carried out as follows: d. folding the flat fabric (1) into a two-layer structure at two folding locations to form two seam loops (2) at the respective folding locations, and connecting the two end edges of the flat fabric (3) to each other, e. The two seam loops (2) are interlaced with each other and connected by introducing a plug wire (1) to form a two-layer fabric loop, wherein the two seam loops (2) are heat-fixed at the same time.

3. The method according to any one of the preceding claims, characterized in that The method further comprises the following steps: a2. removing a plurality of adjacent transverse yarns (5) in the region of the folded portion, In particular, step a2. is performed between steps a. and b.

4. The method according to any one of the preceding claims, characterized in that The electrically conductive plug wire (1) is a single wire which in particular has a perfectly circular cross section.

5. The method according to any one of claims 1 to 3, characterized in that The electrically conductive plug wire (1) is designed as a braided structure or a twisted wire (7) consisting of a plurality of yarns (8, 9).

6. The method according to claim 5, characterized in that The twisted wire (7) or the braided structure is formed only by the electrically conductive yarn (8), or the twisted wire (7) or the braided structure is formed by a combination of the electrically conductive yarn (8) and the non-conductive yarn (9).

7. The method according to any one of the preceding claims, characterized in that The electrically conductive plug wire (1) is embodied as a metal plug wire (1).

8. The method according to any one of claims 1 to 6, characterized in that The electrically conductive plug wire (1) comprises or consists of a polymer wire which is made conductive by the introduction of particles or by coating.

9. The method according to any one of the preceding claims, characterized in that At least one sensor is provided for detecting the temperature of the electrically conductive plug wire and / or the seam ring (2), wherein the detected temperature value is used in particular for regulating the voltage (11).

10. Basic structure of a stretched fabric, in particular a seam felt for a paper machine, which basic structure is produced by a method according to any of the preceding claims.

11. A fabric, in particular a seaming felt for a paper machine, comprising at least one base structure according to claim 10.

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