DE102022121769A1 - Process, basic structure and covering - Google Patents

Abstract

Method for thermally fixing a seam loop of a basic structure for a covering, in particular for a seam felt of a paper machine, comprising stepsa. Providing a flat fabric comprising longitudinal threads and transverse threads, wherein the flat fabric has in particular undergone a first thermal fixing process, b. Folding the flat fabric into a two-layer structure at at least one fold point, forming a seam loop at the respective fold point, c. Insertion of a plug wire into the seam loop characterized in that d. the plug-in wire is designed as an electrically conductive plug-in wire, and the electrically conductive plug-in wire is heated by applying an electrical voltage to thermally fix the night loop.

Description

The invention relates to a method for producing a basic structure for a covering of a paper machine, in particular for a seam felt. The invention also relates to the basic structure produced and a covering with such a basic structure.

Woven structures are often used in coverings for paper machines. For example, press felts usually comprise a woven base structure (ground weave) on which one or more layers of nonwoven fibers are attached.

For a long time it was necessary to produce a circular, endless loop of fabric, which involved a complex and long weaving process. In order to avoid endless weaving, Sudre in EP0425523 presented a process in which the two ends of a flat fabric are placed on themselves, creating a two-layer piece of fabric. The two front edges of the piece of fabric are usually connected to one another in a suitable manner. Seam loops are created at the folds, which can be guided into one another and connected using a pin wire. In this way, a fabric loop with a pin-wire seam is created, which can serve as a basic structure for a seam felt.

As an improvement to this process, EP2788546 B1 suggested removing some cross threads from the fabric at the folds. This creates larger seam loops, which make forming the pin wire seam much easier.

A further development of this is from the patent specification DE 10 2019 121 485 known. The basic structure is made up of several modules, with the two seam loop modules each being created by folding a flat fabric once. These seam loop modules are then usually connected to other pieces of flat fabric to form the two-layer piece of fabric. In this way, more economical production is possible because the fabrics and seam elements can be manufactured independently of the dimensions of the later covering.

When producing the structures described above, the flat fabrics are generally pre-fixed thermally on a fixing device downstream of the loom. This releases tension in the fabric threads caused by weaving and also deforms the threads. A fabric thread that is removed from the fabric after pre-fixing is then no longer straight, but has a wavy shape.

If seam felts are to be made from these fabrics, the fabric is first connected to form an endless belt and weft threads or cross threads are usually removed at two points on the fabric tape. The seam loops for the pin wire seam are formed at these points. The seam area is often secured with a sewn seam. However, the seam loops formed from the threads/monofilaments running in the machine direction still have the waves or bends caused by the fixing of the fabric structure, which only allow the formation of a functioning pin-wire seam to a limited extent. In practice, the pin-wire seam of the fabric is closed with a pin-wire provided for this purpose and the entire fabric is heat-fixed again in a second fixation process. The deformations caused by the twisting of the fabric can be removed and cleanly formed seam loops are obtained that have adapted to the cross section of the plug-in wire. This makes it possible to open and close the plug-wire seam comparatively easily.

This re-fixation process is carried out on a stretching system with rollers under tension and requires the lengthy heating of at least one oil-heated roller to temperatures of up to 140-170°C. The process time for a fabric is approx. 30-60 minutes plus approx. 30 minutes of setup time. This process is associated with high energy consumption and high occupancy of the heat fixing systems.

In addition, during this process, areas of the seam loops are subject to different thermal conditions, depending on whether they are arranged on the side facing or away from the heated roller. This leads to inhomogeneities in the material properties of the seam loops.

The object of the invention is to further improve the manufacturing process known from the prior art.

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 productivity of an existing machine park when producing the structures described.

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

These tasks are achieved according to the invention by a method according to independent claim 1, as well as by the resulting basic structure and a covering using such a basic structure.

Further advantageous embodiments of the present invention can be found in the subclaims.

1. a. Bereitstellen eines Flachgewebes umfassend Längsfäden und Querfäden, wobei das Flachgewebe insbesondere einen ersten thermischen Fixierprozess durchlaufen hat,
2. b. Falten des Flachgewebes zu einer zweilagigen Struktur an zumindest einer Faltstelle unter Ausbildung einer Nahtschlaufe an der jeweiligen Faltstelle,
3. c. Einführen eines Steckdrahts in die Nahtschlaufe Erfindungsgemäß ist weiterhin vorgesehen, dass
4. d. der Steckdraht als elektrisch leitfähiger Steckdraht ausgeführt ist, und der elektrisch leitfähige Steckdraht durch Anlegen einer elektrischen Spannung zum thermischen Fixieren der Nachtschlaufe aufgeheizt wird.

With regard to the method, the object is achieved by a method for thermally fixing a seam loop of a basic structure for a covering, in particular for a seam felt of a paper machine, comprising the steps

1. a. Providing a flat fabric comprising longitudinal threads and transverse threads, the flat fabric having in particular undergone a first thermal fixing process,
2. b. folding the flat fabric into a two-layer structure at at least one fold point, forming a seam loop at the respective fold point,
3. c. Insertion of a plug wire into the seam loop According to the invention it is further provided that
4. d. the plug-in wire is designed as an electrically conductive plug-in wire, and the electrically conductive plug-in wire is heated by applying an electrical voltage to thermally fix the night loop.

The inventors have recognized that the thermal fixing of the fabric in the second fixing step is of no significant importance for the functionality of the basic structure. The second fixing step only serves to improve the structure of the seam or the seam loops. This means that the heating of the basic structure can also be limited to the area of the seam loops. This makes it possible to fundamentally change the process of heating. Instead of bringing the energy to the seam loops from the outside via heated rollers, as was previously the case, in methods according to the present invention the energy is introduced into the seam loop from the inside. This is done using an electrically conductive plug-in wire that is inserted into the suture loop. By applying a voltage, a current flows through this pin wire, causing the pin wire to heat up, and thus also the threads of the seam loop or loops surrounding it.

The heat generated here spreads largely homogeneously in the seam loops because the pin wire runs centrally in the seam loops. Since the current flow through the conductor is constant at all points, if the resistance is constant over the length of the wire, the same electrical heat loss is generated at every point on the entire plug-in wire. In principle, this enables a locally very limited, homogeneous heat distribution in the seam loops as well as uniform and simultaneous heating of all seam loops of the pin wire seam.

This means that the deformations caused by the twisting of the fabric can be removed and cleanly formed seam loops are obtained that have adapted to the cross section of the plug-in wire.

In contrast to the prior art, the lengthy heating of at least one oil-heated roller to temperatures of up to 140-170 ° C is no longer necessary. The process time for a fabric is reduced from 30-60 minutes plus approx. 30 minutes of setup time to just a few minutes. The time for the thermal treatment in processes according to the present invention is usually between 90 seconds and 10 minutes, in particular between 2 minutes and 5 minutes. In addition, only a fraction of the energy is required for the process proposed in the context of the invention, since heating the heating rollers can be dispensed with.

The process described is particularly advantageous when using fabrics with two different fabric types, with the transition of the fabric types taking place in the area of the pin wire seam. Such structures are, for example, in the US 2009/0090425 described. In such cases, with the heat fixing processes used to date, it would have to be assembled into an endless belt beforehand and heat fixed with a closed pin wire seam. With two different types of fabric within one belt, this leads to the problem that the heat setting process cannot be optimized for both types of fabric at the same time.

• b. Falten des Flachgewebes zu einer zweilagigen Struktur an zwei Faltstellen unter Ausbildung von zwei Nahtschlaufen an den jeweiligen Faltstellen, sowie Verbinden der beiden stirnseitigen Kanten des Flachgewebes miteinander.
• c. Ineinanderführen der beiden Nahtschlaufen und Verbinden durch Einführen eines Steckdrahts unter Ausbildung einer zweilagigen Gewebeschlaufe,

Methods according to aspects of the present invention can be carried out for individual seam modules as described in the DE 10 2019 121 485 are described, as well as for an entire two-layer fabric loop, such as from EP2788546 B1 known. In the second case, it is advantageous if steps b. and c. be carried out as follows:

• b. Folding the flat fabric into a two-layer structure at two fold points, forming two seam loops at the respective fold points, and connecting the two front edges of the flat fabric together.
• c. Bringing the two seam loops together and connecting them by inserting a pin wire to form a two-layer fabric loop,

Both seam loops can be thermally fixed at the same time.

Advantageously, the closed pin wire seam can be placed under slight tension in the longitudinal direction (=machine direction) during the thermal treatment. This improves the contact of the seam loops with the conductive pin wire.

Keeping the fabric wide in the seam area during thermal fixing is sometimes advantageous and can be achieved by clamping the fabric edges.

Alternatively, in principle it is also possible to separately treat the respective fabric ends equipped with seam loops by inserting the conductive pin wire into the seam loops present at the fabric end and carrying out the thermal treatment of the seam loops with the seam not closed.

• a2. Entfernen einer Mehrzahl benachbarter Querfäden im Bereich der Faltstellen

In general, it is advantageous if the method further includes the step

• a2. Removing a plurality of adjacent transverse threads in the area of the folds

Step a2. can in particular between steps a. and b. be performed.

By removing the cross threads, the position of the fold is clearly defined and made visible, which simplifies the subsequent folding.

The resulting window also creates larger seam loops, which, among other things, simplifies the insertion of the pin wire.

By adjusting the electrical voltage, the current and thus the heat loss and consequently the temperature of the plug-in wire can be adjusted very easily and specifically.

However, for most conductive plug wire materials, electrical resistance will increase with increasing temperature. If such plug wires are used, the temperature of the plug wire or the seam loops can be achieved by means of temperature-monitored regulation of the voltage and thus 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 plug-in wire and/or the seam loops, with determined temperature values being used in particular to regulate the electrical voltage.

Non-contact infrared sensors, for example, are suitable for this.

With a method according to one aspect of the present invention, a defined temperature heating and cooling ramp before and after the thermal treatment at the target temperature is also possible. This is not possible or only possible to a limited extent with the methods known from the prior art. Even in the prior art, the heating rollers can be operated with predetermined temperature curves - limited by the inertia of the roller temperature. However, the base fabric must be moved over the hot roller and thus cools down with each cycle and heats up again when it comes into contact with the heating roller again. If the thermal treatment is carried out in a belt circulation, the heating and cooling ramp is also fixed; the fabric cools down after leaving the hot roller, influenced by the ambient temperature.

The cooling rate in particular has a strong influence on the morphology of the material after thermal treatment and 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, cooling can be achieved in a very targeted manner by reducing the voltage - if necessary, monitored by a temperature measurement.

Alternatively, plug-in wires with largely temperature-independent resistance can be used, such as constant wires, or twists or strands that contain constant wires. Temperature monitoring may be unnecessary here.

In the context of the present application, the term “wire” or “wire” is intended to be understood very broadly. As is common in the area of paper machine clothing, the term is used not only for metallic wires but also for “plastic wires”, i.e. stronger plastic filaments.

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

1. i. der elektrisch leitfähige Steckdraht als metallischer Steckdraht ausgeführt ist.
2. ii. der elektrisch leitfähige Steckdraht als metallischer Steckdraht ausgeführt ist, der eine Polymerbeschichtung aufweist.
3. iii. der elektrisch leitfähige Steckdraht als Polymerdraht ausgeführt ist, der mit leitendem Material, insbesondere Metall beschichtet ist.
4. iv. der elektrisch leitfähige Steckdraht als Polymerdraht ausgeführt ist, der leitende Partikel umfasst
5. v. der elektrisch leitfähige Steckdraht als Polymerdraht ausgeführt ist, der elektrisch leitfähige Polymere umfasst oder daraus besteht.

For example, it is possible that

1. i. the electrically conductive plug-in wire is designed as a metallic plug-in wire.
2. ii. the electrically conductive plug-in wire is designed as a metallic plug-in wire that has a polymer coating.
3. iii. the electrically conductive plug-in wire is designed as a polymer wire that is coated with conductive material, in particular metal.
4. iv. the electrically conductive plug-in wire is designed as a polymer wire that includes conductive particles
5. v. the electrically conductive plug-in wire is designed as a polymer wire which comprises or consists of electrically conductive polymers.

Suitable metals for a plug wire or a coating are, for example, copper, silver, gold or alloys, in particular alloys such as Konstanten®, Manganin® or Isotan®, in which the electrical resistance changes only slightly with temperature.

Suitable polymers for a polymer wire are, for example, polyamides or PET. Ideally, such polymers have a melting point well above the temperature used when thermally treating the seam loops.

1. I. der elektrisch leitfähige Steckdraht ein Monodraht ist, der insbesondere einen kreisrunden Querschnitt aufweist
2. II. der elektrisch leitfähige Steckdraht als Zwirn aus mehreren Garnen ausgeführt ist, wobei der Zwirn insbesondere ausschließlich aus elektrisch leitfähigen Garnen gebildet sein kann, aus einer Kombination von elektrisch leitfähigen Garnen und nicht elektrisch leitfähigen Garnen bestehen kann.
3. III. Der elektrisch leitfähige Steckdraht als geflochtene Struktur ausgeführt ist, insbesondere als Litze oder Schnur, wobei die geflochtene Struktur insbesondere ausschließlich aus elektrisch leitfähigen Garnen gebildet sein kann, aus einer Kombination von elektrisch leitfähigen Garnen und nicht elektrisch leitfähigen Garnen bestehen kann.
4. IV. Der elektrisch leitfähige Steckdraht als Zwirn oder geflochtene Struktur ausgeführt ist, wobei die einzelnen Garne nicht elektrisch leitfähig sind, jedoch der Zwirn bzw. die geflochtene Struktur als Ganzes mit einem leitfähigen Material, insbesondere einem Metall beschichtet ist.

Regardless of the choice of material of the plug-in wire, the structure of the same is different. It is possible, for example, that

1. I. the electrically conductive plug-in wire is a monowire, which in particular has a circular cross section
2. II. the electrically conductive plug wire is designed as a thread made of several yarns, whereby the thread can in particular be formed exclusively from electrically conductive yarns, or can consist of a combination of electrically conductive yarns and non-electrically conductive yarns.
3. III. The electrically conductive plug-in wire is designed as a braided structure, in particular as a strand or cord, wherein the braided structure can in particular be formed exclusively from electrically conductive yarns, can consist of a combination of electrically conductive yarns and non-electrically conductive yarns.
4. IV. The electrically conductive plug wire is designed as a thread or braided structure, the individual threads being not electrically conductive, but the thread or the braided structure as a whole is coated with a conductive material, in particular a metal.

The electrically conductive plug-in wire can only be made from conductive individual threads or already twisted yarns. However, non-conductive individual threads can also be contained in the thread or strand.

Conductive individual threads can also consist entirely of electrically conductive material or include a portion of a polymer. For example, the individual threads can be made of a polymer, with conductive material added inside or in the form of a coating, or can consist of a metal thread that is coated with a polymer.

By making part of the plug-in wire cross-section made of non-conductive material, the effective cross-section of the conductive material in the plug-in wire and thus the electrical resistance of the plug-in wire can be adjusted. With larger plug-in wire diameters, this avoids a resistance that is too low and the associated high current flow.

Whether the electrically conductive plug wire consists entirely of conductive material or not can also be selected depending on the diameter of the seam loop to be achieved, and thus depending on the required diameter of the plug wire. Usual plug wire diameters are between 0.2 and 2.5 mm, preferably 0.5 and 2.0 mm.

1. i. Der Durchmesser des Steckdrahts sollte nahe an dem Durchmesser der Nahtschlaufe liegen. Üblicherweise liegen diese Durchmesser der Nahtschlaufen -und damit auch der Steckdrähte - zwischen 1.1mm und1.8mm; insbesondere bei 1.55 mm
2. ii. Der Widerstand des Steckdrahts sollte bei Raumtemperatur zwischen 0.5 Ω/m und 200 Ω/m insbesondere zwischen 1 Ω/m und 50 Ω/m liegen
3. iii. Der Steckdraht sollte in der Lage sein, Biegespannungen auszuhalten, ohne sich plastisch zu verformen. Dies ist wichtig, um Knicke in der Naht zu vermeiden.
4. iv. Integrität des Steckdrahts. Der Steckdraht soll als Einheit wirken, auch wenn er aus einer Vielzahl von einzelnen Garnen zusammengesetzt ist. Ein bekanntes Problem ist die Bildung von Garnnestern („wire nests“). Dabei verwinden oder verwickeln sich einzelne Garne aus dem Steckdraht und bilden Nester oder Knötchen. Dadurch wird das Einziehen und Entfernen des Steckdrahts erschwert.
5. v. Die Zugfestigkeit des Steckdrahts solle größer sein als 50N, insbesondere größer als 100N. Dies ist unter anderem deshalb vorteilhaft, da sich dann der Steckdraht nach der thermischen Behandlung der Nahtschlaufe einfach wieder herausziehen lässt, ohne Gefahr, dass der Steckdraht dabei reißt, und Teile in der Nahtschlaufe verbleiben, welche dann aufwändig entfernt werden müssten.
6. vi. Das Material sollte in einem weiten Temperaturbereich stabil bleiben, so z.B. zwischen Raumtemperatur (20°C) und 190°C. „Stabil“ heißt in dem Zusammenhang, dass sich Eigenschaften wie Deformation, Dimensionsstabilität, Leitfähigkeit oder Aggregatzustand nicht oder nur in geringem Umfang ändern.

When choosing an optimal electrically conductive plug-in wire, many aspects play a role, at least some of which should preferably be fulfilled, and ideally all of them.

1. i. The diameter of the pin wire should be close to the diameter of the suture loop. Usually these diameters of the seam loops - and therefore also the plug wires - are between 1.1mm and 1.8mm; especially at 1.55 mm
2. ii. The resistance of the plug wire should be between 0.5 Ω/m and 200 Ω/m, in particular between 1 Ω/m and 50 Ω/m, at room temperature
3. iii. The pin wire should be able to withstand bending stresses without plastically deforming. This is important to avoid kinks in the seam.
4. iv. Integrity of the plug wire. The pin wire should act as a unit, even if it is made up of a large number of individual yarns. A well-known problem is the formation of wire nests. Individual yarns from the wire twist or become entangled and form nests or knots. This makes it difficult to pull in and remove the pin wire.
5. v. The tensile strength of the plug wire should be greater than 50N, especially greater than 100N. This is advantageous, among other things, because the plug-in wire then moves after the thermal After treatment, the seam loop can simply be pulled out again, without the risk of the pin wire breaking and parts remaining in the seam loop, which would then have to be laboriously removed.
6. vi. The material should remain stable over a wide temperature range, for example between room temperature (20°C) and 190°C. In this context, “stable” means that properties such as deformation, dimensional stability, conductivity or physical state do not change or only change to a small extent.

• • Ein einfacher metallischer Draht aus NiCr mit z.B. 1.55mm Durchmesser erfüllt zwar i. und ii., jedoch nicht iii. (Knicke!)
• • Ein Monofilament aus Polymer dagegen kann die elektrischen Leitfähigkeitseigenschaften nicht ohne weiteres liefern

Achieving these properties cannot be achieved with simple mono wires.

• • A simple metallic wire made of NiCr with a diameter of 1.55mm, for example, generally satisfies. and ii., but not iii. (kinks!)
• • A polymer monofilament, on the other hand, cannot easily provide the electrical conductivity properties

Therefore, a more complex structure of the plug-in wire usually makes sense.

An improvement to a metallic monowire could, for example, be to use a metallic twist or rope-like pin wire made of a large number of thinner metal threads. This increases the flexibility of the resulting pin wire. For ease of reading, in the context of this application, unless otherwise stated, the term “twine” is always used to refer to structures with multi-stage twisting, such as rope-like structures.

• 34x7 + FC (Faserkern)
• 34x7 + IWS („Independent wire strand core“)
• 36x7 + FC
• 36x7 +IWS

Possible rope-like plug wires made of metal filaments are

• 34x7 + FC (fiber core)
• 34x7 + IWS (“Independent wire strand core”)
• 36x7 + FC
• 36x7 +IWS

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

As an alternative, the plug-in wire can have a polymer core around which metallic threads or strands are arranged.

Alternatively, it can be provided that the plug-in wire has a metallic core (a wire, a braid, a twine, in particular a rope), this core being surrounded by a sheath made of polymer material. Ideally, the polymer material is a good conductor of heat. The polymer jacket protects the metallic core, prevents kinks and makes it easier to insert or remove the plug-in wire.

• Eine Verbesserung der leitfähigen Garne kann ein fester Polymerkern sein, der ebenfalls beschichtet werden kann oder unbeschichtet bleibt. Der feste Polymerkern kann als Zuglastträger dienen, aber auch die Steifigkeit der äußeren Geflechte oder Garne erhöhen und die Gesamtkosten des Steckdrahts senken.

Graphene, certain carbon filaments, or sputtered/plated yarns are possible, depending on the resistance required. Sputtered or plated polymeric yarns have a metallic coating, and the typical size of such yarns is often very small (e.g. 0.1 mm) because the coating process is inefficient for larger diameter yarns with good electrical properties. Therefore, a combination of sputtered/plated yarns is required to achieve the required pin wire diameters. The integrity of the pinwire requires that the combination of small coated yarns act as a unit. Therefore, a pin wire with coated polymeric yarns can consist of a braid, a rope, a braid of braids, a cable, etc.:

• An improvement to the conductive yarns can be a solid polymer core, which can also be coated or left uncoated. The solid polymer core can serve as a tensile load support, but can also increase the stiffness of the outer braids or yarns and reduce the overall cost of the pinwire.

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

The use of polymer yarn systems as pin 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 slightly increases in diameter. Increasing the diameter can contribute to a round, even seam loop formation. Ideally, the diameter increases during the heat cycle and returns to the original diameter after cooling.

The process of thermally fixing loops using a conductive pin wire can advantageously be regulated. The control can be either temperature-controlled via thermocouples or current-controlled. Thermocouples are used as a control feedback loop to regulate the current strength of the circuit. The timed heat setting can also be automated.

Thermocouples can be omitted if the resistivity of the pins is known. The resistance of most conductive Yarn is quite stable within the specified temperature range (room temperature - 190C).

• • Grundgewebe: Flachgewebe in Leinwandbindung mit Längs- und Querfäden aus PA6
• • Durchmesser der MD-Fäden 0.4 mm
• • Durchmesser des elektrisch leitfähigen Steckdrahts: 1,4mm
• • Der Steckdraht ist als Zwirn aus Konstantan ® ausgeführt.
• • Die Spannung wurde so weit erhöht, bis die Temperatur des Steckdrahts 150°C beträgt.
• • Dauer der thermischen Behandlung: 2 Minuten bis 10 Minuten, z.B. 5 Minuten.
• • Anschließend wird die Spannung langsam auf null zurückgefahren (z.B. über 60 Sekunden)

The following example is intended to explain the invention in more detail. However, the invention is not limited to these examples.

• • Base fabric: Flat weave plain weave with longitudinal and transverse threads made of PA6
• • Diameter of MD threads 0.4 mm
• • Diameter of the electrically conductive plug wire: 1.4mm
• • The plug-in wire is made from Konstantan ® thread.
• • The voltage was increased until the temperature of the plug wire was 150°C.
• • Duration of thermal treatment: 2 minutes to 10 minutes, eg 5 minutes.
• • The voltage is then slowly reduced to zero (e.g. over 60 seconds)

So far, the methods of thermal fixation have been described for fabrics in which the seam loops are created by folding a flat fabric.

In the classic production of seam fabrics, the seam loops have so far been created directly in the loom. To do this, weaving pintles are pulled in on both sides of the loom in the MD direction. The CD threads are then woven around these weaving wires. After removing the weaving wires, the seam loops are created, which can be guided into one another analogously to the process described above. Such seam loops can also be thermally fixed using an electrically conductive pin wire.

In particular, it is also possible for the weaving pintle to be designed as an electrically conductive pintle wire according to one of the aspects described above.

The methods described above can be used for a variety of applications. For example, it can be used to produce base fabrics for paper machine clothing, e.g. seam felts, but also for other fabric belts with pin-wire seams, such as conveyor belts, conveyor belts, functional belts, etc.

• 1 a bis 1d erläutern Schritte eines Verfahrens gemäß einem Aspekt der Erfindung
• 2a bis 2d 1 d erläutern Schritte eines Verfahrens gemäß einem weiteren Aspekt der Erfindung
• 3 und 4 zeigen Nahtschlaufen mit Steckdrähten zur Durchführung von Verfahrensschritten gemäß verschiedenen Aspekten der Erfindung.

The invention is explained in more detail below with reference to figures. The invention is not limited to the variants shown in the figures. The figures show in detail:

• 1a to 1d explain steps of a method according to one aspect of the invention
• 2a to 2d 1 d explain steps of a method according to a further aspect of the invention
• 3 and 4 show seam loops with plug-in wires for carrying out method steps according to various aspects of the invention.

1a to 1d explain steps of a method according to one aspect of the invention. First, a flat fabric 3 is provided, which is woven from longitudinal threads 4 and transverse threads 5. In contrast to round fabrics, such flat fabrics 3 can be produced very quickly. After weaving, the flat fabric 3 was subjected to a thermal fixation process (“heat setting”). This removes the tension in the fabric threads 4.5, but also deforms these fabric threads 4.5.

For processes according to various aspects of the present invention, 3 plain weave fabrics can be used as flat fabrics. It is also conceivable that one or more parameters of the weaving pattern change at one point on the flat fabric 3. Such a change is sensibly planned at the future folding point.

In 1b Some transverse threads 5 have been removed from the area surrounding this fold. Typically 3 to 7 transverse threads 5 will be 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 preparing such a window 6, the flat fabric 3 can be folded and formed into a two-layer structure by laying it on itself. This is in 1c shown. This creates a seam loop 2 at the fold point. By removing the transverse threads 5 and forming a window 6, the seam loop 2 is essentially formed by longitudinal threads 4. This makes it easier to insert a plug-in wire 1.

However, the longitudinal threads 4 are still deformed by the thermal fixation process. However, round seam loops aligned in one plane are the basis for good seam coverings. These deformations should be removed again by further thermal treatment - possibly in combination with a certain tension in the longitudinal direction.

In a method according to one aspect of the invention, this is done as in 1d shown, an electrically conductive plug-in wire 1 is inserted into the seam loop 2. To this electrically conductive plug Wire 2 can then be connected to an electrical voltage source 11. A current therefore flows through the electrically conductive plug-in wire 1. This acts as a resistance and heats up. The longitudinal threads 4 of the seam loop 2 are heated by the heated plug wire 1. This allows the deformations in the longitudinal wires 4 to be solved. 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. Based on the temperature values determined, the strength of the electrical voltage 11 can be adjusted. This can be done manually or in the form of an automated control loop. In this process, the energy is specifically applied only to the area of the seam loops 2. On the one hand, this allows energy to be saved compared to the conventional process. On the other hand, it is special with the one in the 1a to 1d The method described is also possible, the seam loops in the EP4010528 to thermally fix the loop elements described, which are only present as a short loop element with a seam loop 2 and cannot be connected to form a closed endless band.

While that's in the 1a to 1d The method described is suitable for thermally fixing a single seam loop 2a to 2d an alternative embodiment of the method in which two seam loops 2 - similar to the conventional process - can be thermally fixed simultaneously. This is done in 2a as in 1a again a flat fabric 3 is provided, comprising longitudinal threads 4 and transverse threads 5, the flat fabric 3 in particular having undergone a first thermal fixing process. The flat fabric 3 in particular has twice the length of the later basic structure. As in 2 B shown, 5 windows 6 are now formed in two places by removing transverse threads. 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 fold points in the area of the two windows 6, a two-layer structure is created with the formation of two seam loops 2 at the respective fold points. The previous front edges of the flat fabric 3 are usually connected to one another, in particular welded.

As in 2c shown, the two seam loops 3 can be guided into one another and connected using a plug-in wire. This results in a closed, two-layer endless belt.

As in 2d shown, in methods according to aspects of the invention, the plug wire can be designed as an electrically conductive plug wire 1. It is again provided that the electrically conductive plug-in wire 1 is heated by applying an electrical voltage source 11 to thermally fix the two night loops 2. As in 2d As can be seen, both seam loops 2 are connected to the electrically conductive plug-in wire 1 and are simultaneously thermally fixed by heating the electrically conductive plug-in wire 1. Here too, a temperature sensor can be provided and the voltage 11 can be regulated based on the measured temperatures.

The thermal fixation of the seam loops 2 in the form of a closed endless band can be advantageous because, for example, a desired pre-tension can be applied to the seam loops very easily. This means that the shape of the seam loops 2 can be influenced within certain limits.

Various options are available for the design of the electrically conductive plug-in wire 1. In principle, it is possible to design this as a simple metallic monowire 1, in particular with a circular cross section. However, this has the disadvantage that the resistance of electrical conductors decreases as the diameter of the wire increases, which means that the wire heats up less. This is often disadvantageous, particularly in the case of seam loops 2 with a larger loop diameter. 3 shows as a possible alternative an electrically conductive plug-in wire 1, which is designed as twine 7. The thread 7 consists of 3 exemplarily from four yarns 8, with all four yarns 8 being designed 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 thread 7 as such is electrically conductive, but the resistance of the thread 7 is only slightly reduced even with larger diameters, since the individual conductive threads 8 have an electrically non-conductive plastic core.

Another possible embodiment of the electrically conductive plug-in wire 1 is in 4 shown. The electrically conductive plug wire 1 is again designed as a thread 7 made of four individual yarns. However, the thread 7 here consists of a combination of conductive yarns 8 and non-electrically conductive yarns 9. In the example 4 These are two conductive 7 and non-conductive 9 yarns. In general, however, other ratios and other numbers of yarns 8, 9 in thread 7 are also possible. In this way, too, it can be prevented that the resistance of the electrically conductive plug-in wire 1 drops too much as the diameter increases. As electrically conductive yarns 8, the in 3 shown, metallic coated plastic filaments are used. Alternatively or additionally, other conductive yarns 8, for example metallic monowires, can also be used.

Reference symbol list

1

electrically conductive plug wire

2

Seam loop

3

Flat weave

4

Longitudinal thread

5

Cross thread

6

Window

7

Twine

8th

electrically conductive yarn

9

non-electrically conductive yarn

11

voltage source

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0425523 [0003]
• EP 2788546 B1 [0004, 0022]
• DE 102019121485 [0005, 0022]
• US 2009/0090425 [0021]
• EP 4010528 [0072]

Claims (11)

Method for thermally fixing a seam loop (2) for a basic structure for a covering, in particular for a seam felt of a paper machine, comprising steps a. Providing a flat fabric (3) comprising longitudinal threads (4) and transverse threads (5), wherein the flat fabric (3) has in particular undergone a first thermal fixing process, b. Folding the flat fabric (3) into a two-layer structure at at least one fold point, forming a seam loop (2) at the respective fold point, c. Insertion of a plug-in wire (1) into the seam loop (2), characterized in that d. the plug-in wire (1) is designed as an electrically conductive plug-in wire (1), and the electrically conductive plug-in wire (1) is heated by applying an electrical voltage (11) to thermally fix the night loop (2). Procedure according to Claim 1 , characterized in that steps b. and c. be carried out as follows: d. Folding the flat fabric (1) into a two-layer structure at two fold points, forming two seam loops (2) at the respective fold points, and connecting the two front edges of the flat fabric (3) to one another. e. Bring the two seam loops (2) into each other and connect them by inserting a pin wire (1) to form a two-layer fabric loop, with both seam loops (2) being thermally fixed at the same time. Method according to one of the preceding claims, characterized in that the method further comprises step a2. Removing a plurality of adjacent transverse threads (5) in the area of the folds, step a2. Especially between steps a. and b. is carried out. Method according to one of the preceding claims, characterized in that the electrically conductive plug-in wire (1) is a monowire which in particular has a circular cross section Procedure according to one of the Claims 1 until 3 , characterized in that the electrically conductive plug wire (1) is designed as a thread (7) or as a braided structure made of several yarns (8, 9). Procedure according to Claim 5 , characterized in that the thread (7) or the braided structure is formed exclusively from electrically conductive yarns (8), or that the thread (7) or the braided structure consists of a combination of electrically conductive yarns (8) and not electrically conductive yarns (9). Method according to one of the preceding claims, characterized in that the electrically conductive plug-in wire (1) is designed as a metallic plug-in wire (1). Procedure according to one of the Claims 1 until 6 , characterized in that the electrically conductive plug-in wire (1) comprises or consists of a polymer wire which is made conductive by introducing particles or by coating. Method according to one of the preceding claims, characterized in that at least one sensor is provided for determining the temperature of the electrically conductive plug-in wire and/or the seam loops (2), with determined temperature values being used in particular to regulate the electrical voltage (11). Basic structure for a covering, in particular for a seam felt of a paper machine, which has been produced by a method according to one of the preceding claims. Covering, in particular seam felt for a paper machine, comprising at least one basic structure according to Claim 10 .

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