METHOD, BASIC STRUCTURE, AND PAPER MACHINE CLOTHING

Abstract

A method for thermally fixing a seam loop of a basic structure for a paper machine clothing, such as a seam felt of a paper machine. A flat fabric is provided with longitudinal threads and transverse threads. The flat fabric may have passed through a first thermal fixing process. The flat fabric is folded at at least one folding point to form a two-ply structure and to form a seam loop at the folding point. An electrically conductive pintle wire is inserted into the seam loop and the electrically conductive wire is heated by applying a voltage for thermally fixing the seam loop and for improving a structure of the seam loop.

Description

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a method for producing a basic structure for a clothing of a paper machine, in particular for a seam felt. Moreover, the invention relates to the basic structure produced and a clothing having such a basic structure.

Woven structures are often used in clothings for paper machines. Pressed felts thus typically comprise, for example, a woven basic structure (basic fabric), on which one or more plies of nonwoven fibers are attached.

For a long time, it was necessary for this purpose to produce a circular-woven, endless fabric loop, which is linked to a complex and long weaving process. In order to avoid the endless weaving, a method was presented in European Patent EP 0 425 523 B1 (P. L. Sudre), in which in a flat fabric, the two ends are placed on themselves, due to which a two-ply fabric piece results. The two end edges of the fabric piece are typically suitably connected to one another. Seam loops arise at the folding points, which can be led one inside another and connected by means of a pintle wire. The result is a fabric tube having pintle wire seam, which can be used as the basic structure for a seam felt.

As an improvement of that method, removing several transverse threads from the fabric at the folding points was proposed in European Patent EP 2 788 546 B1. Larger seam loops thus result, which significantly facilitate the formation of the pintle wire seam.

European Patent EP 0 932 775 B1 discloses a pintle wire for a seam felt.

A refinement is known from U.S. Patent No. U.S. Pat. No. 11,952,717 B2 and its German counterpart DE 10 2019 121 485. In that case, the basic structure is constructed from multiple modules, wherein the two seam loop modules are each created by folding a flat fabric once. These seam loop modules are then generally connected to further flat fabric pieces to form the two-ply fabric piece. In this way, more economic production is possible, since the fabric and seam elements can be produced independently of the dimension of the later clothing.

During the production of the above-described structures, in general the flat fabric presently already undergoes preliminary heat setting on a fixing device downstream from the loom. Tensions in the fabric thread arising due to the weaving are thus resolved and the threads are also deformed. A fabric thread which is removed from the fabric after the preliminary heat setting is then no longer straight, but rather has a wavy shape.

If seam felts are to be produced from this fabric, the fabric is additionally connected to form an endless band and weft threads or transverse threads are typically removed at two points of the fabric band. The seam loops for the pintle wire seam are formed at this point. The seam area is often secured in this case by a sewn seam. The seam loops thus formed from the threads/monofilament extending in the machine direction do not yet have the waves or kinks induced by the setting of the fabric structure, however, which only permit the formation of a functioning pintle wire seam to a limited extent. In practice, the pintle wire seam of the fabric is closed using a pintle wire intended for this purpose and the entire fabric is heat set again in a second setting process. The deformations arising due to the fabric kinking can be removed and cleanly shaped seam loops are obtained, which have adapted themselves to the cross-section of the pintle wire. Comparatively simple opening and closing of the pintle wire is therefore possible.

This renewed setting process is carried out on a stretching system using rollers under tension and requires the lengthy heating of at least one oil-heated roller to temperatures up to 140-170° C. The process duration for a fabric is approximately 30-60 minutes plus approximately 30 minutes equipping time. A higher energy consumption and an occupancy of the heat setting facilities is linked to this process.

Moreover, in this process areas of the seam loops are subject to different thermal conditions, depending on whether they are arranged on the side of the heated roller facing toward or away. This results in inhomogeneities of the material properties of the seam loops.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a process, a basic structure, and a clothing which overcome the above-mentioned and other disadvantages of the heretofore-known devices and methods of this general type and which provides for an improvement of the prior art production processes. It is a particular object of the invention to reduce the energy required for production. It is a further object of the invention to increase the efficiency and productivity of an existing machine park during the production of the described structures. Finally, it is an object of the invention to improve the quality of the seam loops.

With the above and other objects in view there is provided, in accordance with the invention, a method for heat setting a seam loop for a basic structure of a clothing, such as a seam felt for a paper machine. The method comprises the following steps:

• • a) providing a flat fabric formed with longitudinal threads and transverse threads, the flat fabric having passed through a first heat setting process;
  • b) folding the flat fabric at at least one folding point to form a two-ply structure and to form a seam loop at the at least one folding point;
  • c) inserting a pintle wire into the seam loop, the pintle wire being an electrically conductive pintle wire; and
  • d) heating the electrically conductive pintle wire by applying an electrical voltage and thereby heat-setting and improving a structure of the seam loop.

In other words, the above and other objects are achieved by the novel method for heat setting a seam loop of a basic structure for a clothing, in particular for a seam felt of a paper machine. The method comprising the following steps:

• • providing a flat fabric comprising longitudinal threads and transverse threads, wherein the flat fabric has in particular passed through a first heat setting process;
  • folding the flat fabric to form a two-ply structure at at least one folding point with formation of a seam loop at the respective folding point;
  • inserting a pintle wire into the seam loop; and
  • the pintle wire is embodied as an electrically conductive inserted wire and the electrically conductive wire is heated by applying an electrical voltage for the heat setting of the seam loop in order to improve the structure of the seam loops.

The inventors have recognized that the heat setting of the fabric in the second setting step has no significant impact on the functionality of the basic structure. The second setting step is solely used to improve the structure of the seam or the seam loops. The heating of the basic structure can therefore also be restricted to the area of the seam loops. This enables the process of the heating to be fundamentally changed. Instead of bringing the energy to the seam loops from the outside via heated rollers, as in the prior art, in the method according to the present invention, the energy is introduced from the inside into the seam loop. This takes place by means of an electrically conductive pintle wire, which is inserted into the seam loop. By applying a voltage, a current flows through this pintle wire, due to which the pintle wire heats up and therefore the threads of the seam loop or seam loops surrounding it do as well.

The heat generated in this case propagates substantially homogeneously in the seam loops, since the pintle wire extends centrally in the seam loops. Since the current flow through the conductor is constant at all points, with a resistance constant over the wire length, the same electrical waste heat is generated at every point of the entire pintle wire. In principle, this enables a locally very limited homogeneous distribution in the seam loops and a uniform and simultaneous heating of all seam loops of the pintle wire seam.

The deformations arising due to the fabric kinking can thus be removed and cleanly shaped seam loops are obtained, which have adapted to the cross section of the pintle wire.

In contrast to the prior art, the prolonged heating of at least one oil-heated roller to temperatures up to 140-170° C. is eliminated. The process duration for a fabric is shortened from 30-60 minutes plus approximately 30 minutes equipping time to a few minutes. The time for the thermal treatment in methods according to the present invention is thus usually between 90 seconds and 10 minutes, in particular between 2 minutes and 5 minutes. Moreover, only a fraction of the energy is necessary for the process proposed in the scope of the invention, since the heating of the heated rollers can be dispensed with.

The described process is also advantageous in particular upon the use of fabrics having two different fabric types, wherein the transition of the fabric types takes place in the area of the pintle wire seam. Such structures are described, for example, in published patent application US 2009/0090425 A1. With the heat setting processes used up to this point, in such cases it would therefore have to be joined together to form an endless band and heat set with closed pintle wire seam. With two different fabric types within a band, this results in the problem that the heat setting process cannot be run with simultaneous optimization for both fabric types.

Methods according to aspects of the present invention can be carried out both for individual seam modules as described in the above-mentioned Patent U.S. Pat. No. 11,952,717 B2 (DE 10 2019 121 485), and also for an entire two-ply fabric loop, as known, for example, from the above-mentioned European Patent EP 2 788 546 B1. In the second case, it is then advantageous if steps b) and c) are carried out as follows:

Folding the flat fabric to form a two-ply structure at two folding points while forming two seam loops at the respective folding points, and connecting the two end edges of the flat fabric to one another. Inserting the two seam loops one into the other and connecting them by inserting a pintle wire while forming a two-ply fabric loop.

The two seam loops can be heat set simultaneously in this case.

The closed pintle wire seam can advantageously be set under slight tensile stress in the longitudinal direction (=machine direction, MD) during the thermal treatment. This improves the contact of the seam loops with the conductive pintle wire.

Keeping the fabric spread in the seam area during the heat setting is also sometimes advantageous and can be achieved by clamping the fabric edges.

Alternatively, the separate treatment of the respective fabric cans equipped with seam loops is also possible in principle, in that the conductive pintle wire is inserted into each of the seam loops present at the fabric end and the thermal treatment of the seam loops is carried out with the seam not closed.

In general, it is advantageous if the method furthermore comprises the following step:

• • a2) Removing a majority of adjacent transverse threads in the area of the folding points.

Step a2) may advantageously be carried out between the above-noted steps a) and b).

On the one hand, the position of the folding point is clearly defined and made visible by the removal of the transverse threads, which simplifies the subsequent folding.

Larger seam loops are also formed by the resulting window, which, among other things, simplifies the insertion of the pintle wire.

By adapting the electrical voltage, the current and therefore the heat loss and as a result the temperature of the pintle wire can be set very easily and deliberately.

For most conductive pintle wire materials, however, the electrical resistance will increase with rising temperature. If such pintle wires are used, the temperature of the pintle wire or the seam loops can be implemented by means of temperature-monitored regulation of the voltage and therefore a temperature program can be implemented during the thermal treatment.

It can therefore be advantageous that at least one sensor is provided for determining the temperature of the electrically conductive pintle wire and/or the seam loops, wherein determined temperature values are used in particular for regulating the electrical voltage.

Contactless infrared sensors are suitable for this purpose, for example.

With a method according to one aspect of the invention, a defined temperature heating and cooling ramp before and after the thermal treatment at target temperature is also possible. This is not possible or is only possible conditionally in the method known from the prior art. The heating rollers—limited by the inertia of the roller temperature—can also be run with predetermined temperature profiles in the prior art. However, the basic fabric has to be moved over the hot roller and thus cools upon each revolution and heats up again upon renewed contact with the heating roller. If the thermal treatment is implemented in a band circulation, the heating and cooling ramp is also fixedly specified, the fabric cools down after leaving the hot roller due to influence from the ambient temperature.

Above all the cooling rate has a strong influence on the morphology of the material after the thermal treatment and a targeted control of the cooling ramp enables the material parameters in the seam loops to be optimized.

In methods according to aspects of the invention, the cooling can be achieved very deliberately by reducing the voltage—possibly monitored by a temperature measurement.

Alternatively, pintle wires having substantially temperature-independent resistance can be used, such as constantan wires or twines or leads which contain constantan wires. Temperature monitoring can possibly be omitted in this case.

In the scope of the present application, the term “wire” or “pintle wire” is to be understood very broadly. As is typical in the context of paper machine clothings, in addition to metallic wires, the term is also used for “plastic wires,” thus thicker plastic filaments.

In methods according to various aspects of the invention, the electrically conductive pintle wires can be implemented in different ways.

It is thus possible, for example, that:

• • The electrically conductive pintle wire is embodied as a metallic pintle wire.
  • The electrically conductive pintle wire is embodied as a metallic pintle wire which has a polymer coating.
  • The electrically conductive pintle wire is embodied as a polymer wire which is coated with conductive material, in particular metal.
  • The electrically conductive pintle wire is embodied as a polymer wire which comprises conductive particles.
  • The electrically conductive pintle wire is embodied as a polymer wire which comprises or consists of electrically conductive polymers.

Suitable models for a pintle wire or a coating are, for example, copper, silver, gold, or also alloys, in particular alloys such as constantan (CoNi), Manganin®, or Isotan®, in which the electrical resistance only changes slightly with the temperature.

Suitable polymers for a polymer wire are, for example, polyamides or PET (polyester, polyethylene terephthalate). Such polymers ideally have a melting point significantly above the temperature used during the thermal treatment of the seam loops.

Independently of the selection of the material of the pintle wire, the structure is the same. It is possible here, for example, that

• • The electrically conductive pintle wire is a monowire, which in particular has a circular cross-section.
  • The electrically conductive pintle wire is embodied as a twine made of multiple yarns, wherein the twine can in particular be formed exclusively from electrically conductive yarns, but can also consist of a combination of electrically conductive yarns and non-electrically conductive yarns.
  • The electrically conductive pintle wire is embodied as a woven structure, in particular as a lead or cord, wherein the woven structure can be formed in particular exclusively from electrically conductive yarns, but can also consist of a combination of electrically conductive yarns and non-electrically conductive yarns.
  • The electrically conductive pintle wire is embodied as a twine or woven structure, wherein the individual yarns are not electrically conductive, but the twine or the woven structure as a whole is coated with a conductive material, in particular a metal.

The electrically conductive pintle wire can be constructed only from conductive individual threads or also already threaded yarns. However, nonconductive individual threads can also be contained in the twine or the lead.

Conductive individual threads can also consist completely of electrically conductive material, or can comprise a proportion of a polymer. The individual threads can thus be constructed, for example, from a polymer, wherein conductive material is added in the interior or in the form of a coating, or can consist of a metal thread which is coated with a polymer.

In that a part of the pintle wire cross section consists of nonconductive material, the effective cross section of the conductive material in the pintle wire and therefore the electrical resistance of the pintle wire can be set. This avoids an excessively low resistance with larger pintle wire diameters and a high current flow connected thereto.

Whether or not the electrically conductive pintle wire consists completely of conductive material can also be selected in dependence on the diameter to be achieved of the seam loops and therefore in dependence on the required diameter of the pintle wire. Typical pintle wire diameters are between 0.2 and 2.5 mm, preferably 0.5 and 2.0 mm.

Many aspects play a role in the selection of an optimal electrically conductive pintle wire, of which preferably at least some, optimally all are to be met:

• • i. The diameter of the pintle wire is to be close to the diameter of the seam loops. These diameters of the seam loops—and therefore also of the pintle wires—are typically between 1.1 mm and 1.8 mm, in particular 1.55 mm.
  • ii. The resistance of the pintle wire at room temperature is to be between 0.5 Ω/m and 200 Ω/m, in particular between 1 Ω/m and 50 Ω/m.
  • iii. The pintle wire is supposed to be capable of withstanding bending tensions without plastically deforming. This is important to avoid buckling in the seam.
  • iv. Integrity of the pintle wire. The pintle wire is to act as a unit, even if it is composed of a plurality of individual yarns. One known problem is the formation of wire nests. Individual threads from the pintle wire twist or tangle and form nests or knots. The pulling in and removal of the pintle wire is thus made more difficult.
  • v. The tensile strength of the pintle wire is to be greater than 50 N, in particular greater than 100 N. This is advantageous, among other things, because then the pintle wire can simply be pulled out again after the thermal treatment of the seam loops, without the risk that the pintle wire will tear and parts will remain in the seam loop, which would then have to be removed in a complex manner.
  • vi. The material is supposed to remain stable in a broad temperature range, thus, for example, between room temperature (20° C.) and 190° C. “Stable” in this context means that properties such as deformation, dimensional stability, conductivity, or phase do not change or only change to a minor extent.

These properties cannot be achieved using single monowires.

A single metallic wire made of NiCr having, for example, 1.55 mm diameter does meet i. and ii., but not iii. (buckling!)

A monofilament made of polymer, in contrast, cannot readily supply the electrical conductivity properties.

A more complex structure of the pintle wire is therefore generally reasonable.

One improvement of a metallic monowire could be, for example, to use a metallic twine-like or rope-like pintle wire made of a plurality of thin or metal threads. This increases the flexibility of the resulting pintle wire. For the sake of easy readability, in the scope of this application, if not indicated otherwise, the term “twine” always also means formations having multistep plying, as cable-like formations are referred to.

Possible rope-like pintle wires made of metal filaments are

• • 34×7+FC (fiber core)
  • 34×7+IWS (“independent wire strand core”)
  • 36×7+FC
  • 36×7+IWS

The individual metal wires of these ropes can in particular have diameters between 0.05 mm and 0.1 mm.

As an alternative, the pintle wire can have a polymer core, around which metallic threads or leads are arranged.

Furthermore, it can alternatively be provided that the pintle wire has a metallic core (a wire, a braid, a twine, in particular a rope), wherein this core is surrounded with a jacket made of polymer material. The polymer material is ideally a good thermal conductor. The polymer jacket protects the metallic core, prevents buckling, and facilitates the pulling and/or withdrawal of the pintle wire.

Graphene, certain carbon filaments, or sputtered/clad yarns are possible, depending on which resistance is required. Sputtered or clad polymer yarns have a metallic coating, and the typical size of such yarns is often very small (for example, 0.1 mm), since the coating process is inefficient for yarns having larger diameter and good electrical properties. A combination of sputtered/clad yarns is therefore necessary in order to achieve the required pintle wire diameter. The integrity of the pintle wire requires the combination of small coated yarns to act as a unit. A pintle wire having coated polymer yarns can therefore consist of a braid, a rope, a braid of braids, a cable, etc.:

An improvement of the conductive yarns can be a solid polymer core which can also be coated or remains uncoated. The solid polymer core can be used as a tensile load carrier, but can also increase the stiffness of the outer braid or yarn and reduce the total costs of the pintle wire.

Polymers for use in pintle wires can consist of polyamides, PET, PEEK, and other materials within the specified temperature specifications.

The use of polymer yarns systems as a pintle wire has a surprising advantage for the heat setting process. During the heat cycle and depending on the temperature, the polymer yarn shrinks in length and its diameter increases slightly. An enlargement of the diameter can contribute to a round, uniform seam loop formation. In the ideal case, the diameter increases during the heat cycle and returns to the original diameter after the cooling.

The process of the heat setting of loops using a conductive pintle wire can advantageously be regulated. The regulation can either be temperature controlled via thermocouples or current control. Thermocouples are used as a feedback loop for the control in order to regulate the amperage of the circuit. The time-controlled heat setting can also be automated.

Thermocouples can be omitted if the specific resistance of the pins is known. The resistance of most conductive yarns is quite stable within the specified temperature range (room temperature—190° C.).

The following example is to explain the invention in more detail. However, the invention is not restricted to this example.

• • Basic fabric: flat fabric in plain weave having longitudinal and transverse threads made of PA6.
  • Diameter of the MD threads 0.4 mm
  • Diameter of the electrically conductive pintle wire: 1.4 mm
  • The pintle wire is embodied as a twine made of constantan®.
  • The voltage is increased until the temperature of the pintle wire is 150° C.
  • Duration of the thermal treatment: 2 minutes to 10 minutes, for example, 5 minutes.
  • The voltage is then slowly returned to zero (for example, over 60 seconds).

Up to this point, the methods of heat setting have been described for fabric in which the seam loops result by folding a flat fabric.

In the classic production of seam fabrics, up to this point, the seam loops have been created directly in the loom. For this purpose, weaving wires (“weaving pintle”) are drawn in in the MD direction on both sides of the loom. The CD threads are then each woven around these weaving wires. After removal of the weaving wires, the seam loops then result, which can be led one inside another analogously to the above-described method. Such seam loops can also be heat set using an electrically conductive pintle wire.

It is also possible in particular here that the weaving wire (“weaving pintle”) is embodied as an electrically conductive pintle wire according to one of the above-described aspects.

The above-described methods can be used for a variety of applications. Thus, for example, basic fabric for paper machine clothings, such as seam felts, can thus be produced, but also for other fabric bands having pintle wire seam, such as transport bands, conveyor bands, function bands, etc.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a method, basic structure, and paper machine clothing, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A to 1D are plan views explaining steps of the method according to one aspect of the invention;

FIGS. 2A to 2D are similar views explaining steps of a method according to a further aspect of the invention;

FIGS. 3 and 4 are sectional side views showing seam loops with pintle wires for carrying out method steps according to various aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first, in particular, to FIGS. 1A to 1D thereof, there are illustrated steps of a method according to one aspect of the invention. First, a flat fabric 3 is provided here, which is woven from longitudinal threads 4 and transverse threads 5. Such flat fabrics 3 can be produced very rapidly, in contrast to circular weaving. The flat fabric 3 was subjected to a thermal fixing process (“heat setting”) after the weaving. The tensions in the fabric threads 4, 5 are thus removed, but these fabric threads 4, 5 are also deformed.

For methods according to diverse aspects of the present invention, fabrics in plain weave can be used as the flat fabric 3. It is also conceivable that one or more parameters of the weaving pattern change at a point of the flat fabric 3. Such a change is reasonably provided at the future folding point.

In FIG. 1B, several transverse threads 5 have been removed in the surrounding of the folding point or fold. Typically, 3 to 7 transverse threads 5 are removed. Due to the removal of the transverse threads 5, a so-called window 6 forms in the flat fabric 3, in which the flat fabric 3 only has longitudinal threads 4. After the preparation of such a window 6, the flat fabric 3 can be folded, and can be formed into a two-ply structure by laying it on itself. This is shown in FIG. 1c. A seam loop 2 thus forms at the folding point. Due to the removal of the transverse threads 5 and formation of a window 6, the seam loop 2 is essentially formed by longitudinal threads 4. This facilitates the insertion of an insertion wire 1.

However, the longitudinal threads 4 are still deformed by the heat setting process. Round seam loops aligned in a plane are the basis for good seam tensions, however. These deformations are to be removed again by a further thermal treatment—possibly in combination with a certain tension in the longitudinal direction.

In a method according to one aspect of the invention, an electrically conductive pintle wire 1 is inserted into the seam loop 2 for this purpose, as shown in FIG. 1D. An electrical voltage source 11 can then be connected to this electrically conductive pintle wire 2. A current thus flows through the electrically conductive pintle wire 1. The wire 1 acts as a resistance and heats up. The longitudinal threads 4 of the seam loop 2 are heated by the heated pintle wire 1. Deformations in the longitudinal threads 4 can thus be resolved. To optimize the method, it is possible to use a temperature sensor (not explicitly shown in the figure), which monitors the temperature of the seam loop 2. The strength of the electrical voltage 11 can be set on the basis of the determined temperature values. This can take place manually or also in the form of an automated control loop. In this method, the energy is deliberately only introduced in the area of the seam loops 2. On the one hand, energy can thus be saved in comparison to the conventional process. On the other hand, it is especially also possible using the method described in FIGS. 1A to 1D to heat set the seam loops of the loop elements described in U.S. Pat. No. 11,952,717 B2 and its counterpart EP 4010528 A1, which are only present as a short loop element having a seam loop 2, and cannot be connected to form a closed endless band.

While the method described in FIGS. 1A to 1D is suitable for heat setting a single seam loop, FIGS. 2A to 2D show an alternative embodiment of the method, in which two seam loops 2—similarly to the conventional process—can be heat set simultaneously. In FIG. 2A, as in FIG. 1A, a flat fabric 3 is again provided, comprising longitudinal threads 4 and transverse threads 5, wherein the flat fabric 3 in particular has run through a first heat setting process. The flat fabric 3 in particular has twice the length of the later basic structure here. As shown in FIG. 2B, windows 6 are now formed at two points by removing transverse threads 5. These windows 6 have a spacing in the longitudinal direction of the flat fabric 3 which corresponds to the length of the later basic structure. By folding the flat fabric 3 at two folding points in the area of the two windows 6, a two-ply structure results with formation of two seam loops 2 at the respective folding points. The previous end edges of the flat fabric 3 are typically connected to one another, in particular welded.

As shown in FIG. 2C, the two seam loops 3 can be led one inside the other and connected by means of a pintle wire. A closed, two-ply endless band is thus obtained.

As shown in FIG. 2D, in methods according to aspects of the invention, the pintle wire can be embodied as an electrically conductive pintle wire 1. It is again provided here that the electrically conductive pintle wire 1 is heated up by applying an electrical voltage source 11 for the heat setting of the two seam loops 2. As can be seen in FIG. 2D, both seam loops 2 are connected here to the electrically conductive pintle wire 1, and are simultaneously heat set by the heating of the electrically conductive pintle wire 1. A temperature sensor can also again be provided here, and the voltage 11 can be regulated on the basis of the measured temperatures.

The heat setting of the seam loops 2 in the form of a closed endless band can be advantageous, since, for example, desired pre-tension can thus be applied very easily to the seam loops. The formation of the seam loops 2 can thus be influenced within certain limits.

Various possibilities are available for the design of the electrically conductive pintle wire 1. In principle, it is possible to embody it as a simple metallic monowire 1, in particular having circular cross section. However, this has the disadvantage that in electrical conductors, the resistance decreases with an increasing diameter of the wire, due to which the wire heats up less. This is often disadvantageous, in particular in seam loops 2 having larger loop diameter.

FIG. 3 shows as a possible alternative an electrically conductive pintle wire 1 which is embodied as a twine 7. The twine 7 consists by way of example of four yarns 8 in FIG. 3, wherein all four yarns 8 are embodied as electrically conductive yarns 8. The yarns shown here are plastic filaments, which are coated with a conductive layer, in particular a metallic layer. This has the advantage that the twine 7 as such is electrically conductive, but the resistance of the twine 7 only decreases insignificantly even at larger diameters, since the individual conductive yarns 8 have an electrically nonconductive plastic core.

A further possible embodiment of the electrically conductive pintle wire 1 is shown in FIG. 4. In this case, the electrically conductive pintle wire 1 is again embodied as a twine 7 made of four individual yarns. However, the twine 7 consists here of a combination of conductive yarns 8 and non-electrically conductive yarns 9. In the example of FIG. 4, there are two conductive yarns 7 and two nonconductive yarns 9. In general, however, other ratios and also other numbers of yarns 8, 9 are also possible in the twine 7. In this way, it is possible to prevent the resistance of the electrically conductive pintle wire 1 from dropping excessively strongly with increasing diameter. The metallically coated plastic filaments shown in FIG. 3 can again be used here as the electrically conductive yarns 8. Alternatively or additionally, however, other conductive yarns 8 such as, for example, metallic monowires can also be used.

The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention:

• • 1 electrically conductive pintle wire
  • 2 seam loop
  • 3 flat fabric
  • 4 longitudinal thread
  • 5 transverse thread
  • 6 window
  • 7 twine
  • 8 electrically conductive yarn
  • 9 non-electrically conductive yarn
  • 11 voltage source

Claims

1. A method for heat setting a seam loop for a basic structure of a clothing, the method comprising the following steps: a) providing a flat fabric formed with longitudinal threads and transverse threads, the flat fabric having passed through a first heat setting process;b) folding the flat fabric at at least one folding point to form a two-ply structure and to form a seam loop at the at least one folding point;c) inserting a pintle wire into the seam loop, the pintle wire being an electrically conductive pintle wire; andd) heating the electrically conductive pintle wire by applying an electrical voltage and thereby heat-setting and improving a structure of the seam loop.

2. The method according to claim 1, wherein steps b) to d) comprise: folding the flat fabric at two folding points to form a two-ply structure and forming two seam loops at the two folding points, and connecting two end edges of the flat fabric to one another;guiding the two seam loops one inside another and connecting the seam loops by inserting a pintle wire while forming a two-ply fabric loop, and simultaneously heat setting the two seam loops.

3. The method according to claim 1, which comprises forming the at least one folding point by removing a majority of mutually adjacent transverse threads in an area of the folding point.

4. The method according to claim 3, which comprises carrying out the step of removing the mutually adjacent transverse threads between step a) and step b).

5. The method according to claim 1, wherein the electrically conductive pintle wire is a monowire.

6. The method according to claim 5, wherein the monowire has a circular cross section.

7. The method according to claim 1, wherein the electrically conductive pintle wire is a twine or a woven structure made up of multiple yarns.

8. The method according to claim 7, wherein said twine or said woven structure is exclusively formed from electrically conductive yarns.

9. The method according to claim 7, wherein said twine or said woven structure consists of a combination of electrically conductive yarns and non-electrically conductive yarns.

10. The method according to claim 1, wherein the electrically conductive pintle wire is a metallic pintle wire.

11. The method according to claim 1, wherein the electrically conductive pintle wire is a polymer wire, which is made conductive by introducing particles or by coating.

12. The method according to claim 1, which comprises determining a temperature of at least one of the electrically conductive pintle wire or the seam loops with at least one sensor.

13. The method according to claim 12, which comprises using temperature values determined by the at least one sensor for regulating an electrical voltage across the pintle wire.

14. The method according to claim 1, which comprises producing a seam felt of a paper machine.

15. A basic structure for a clothing, wherein the basic structure has been produced by the method according to claim 1.

16. The basic structure according to claim 15, wherein the clothing is a seam felt of a paper machine.

17. A clothing, comprising a basic structure produced by the method according to claim 1.

18. The clothing according to claim 17, configured as a seam felt for a paper machine.