DE102021133505A1 - Basic structure, covering and manufacturing process - Google Patents

Abstract

Basic structure and clothing for a machine for producing or processing a fibrous web, the basic structure having an endless basic fabric, the endless basic fabric being designed as a flat fabric which is made endless by connecting its two front edges by means of a joint, the joint in particular being either transverse runs to the running direction of the subsequent clothing or deviates from this transverse direction (CD) by a maximum of 20°, in particular a maximum of 10°. It is provided that the basic structure also has a layer of threads, which is made up of a group of threads that are arranged in a spiral on the endless base fabric and are fixed to it, with the threads orienting the layer of threads essentially in the running direction (MD) of the later covering are and deviate from this direction by a maximum of 20°, preferably by a maximum of 10°. In addition, methods for their production.

Description

The invention relates to a basic structure for a clothing for a machine for producing or processing a fibrous web according to the preamble of claim 1, an associated clothing according to the preamble of claim 9 and a method for producing a basic structure according to claim 13.

The base fabrics of papermachine clothing, such as press felts, are typically woven structures. Traditionally, circular-woven base fabrics were used for this. However, the production of such circular fabric is very expensive. In addition, when weaving the base fabric, the exact length of the later covering must already be known.

To avoid this limitation is from the prior art, for example EP 1 579 066 , Known to replace the round fabric with a flat fabric. To produce an endless basic structure, the end faces are connected to one another.
For the connection of the front edges proposes EP 1 579 066 for example welding. From the EP 3 687 774 other methods for welding the front edges are known.

Such a production of basic structures or coverings is very advantageous from an economic point of view. The base fabric can be pre-produced on a loom in maximum width on a roll. For the production of a covering, the desired length can then be cut off the roll and made endless and the width can be adjusted. At the time of weaving, the dimension of the covering does not have to be known. Also, the process of flat weaving is faster than that of circular weaving.

However, such coverings have a number of disadvantages, particularly when used as a press felt.

The connection point can represent a weak point in the fabric, especially in challenging applications where the fabric is subjected to high tensile loads.

In addition, the connection point can also produce markings in the fibrous web, since its structure differs from the structure of the rest of the fabric, and these structures can also be transferred to the fibrous web through the fleece layers that are usually applied.

The object of the invention is to overcome the disadvantages of the prior art while maintaining the desirable economic advantages.

The object is achieved according to the invention by a basic structure for a covering according to independent claim 1, a covering according to claim 9 and a method for producing a basic structure according to claim 13.

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

A basic structure for a clothing for a machine for producing or processing a fibrous web is proposed, the basic structure having an endless basic fabric, the endless basic fabric being designed as a flat fabric which is made endless by connecting its two front edges by means of a joint.

According to the invention, the basic structure also has a layer of threads, which is made up of a group of threads that are arranged in a spiral on the endless base fabric and are fixed to it, the threads of the layer of threads being oriented essentially in the running direction (MD) of the later covering and from in this direction by a maximum of 20°, preferably by a maximum of 10°.

The joint connection advantageously either runs transversely to the running direction of the later covering or deviates from this transverse direction (CD) by a maximum of 20°, in particular a maximum of 10°.

It can be provided that the joint connection is designed as a welded connection and/or an adhesive connection.

The fibrous web can be, in particular, a paper or cardboard web, a tissue web, a cellulosic web or a nonwoven web.

The basic structure proposed here can also be manufactured very easily and quickly. It uses the flat fabric known from the prior art, which is made endless by joining the front edges. As a result, even with basic structures according to aspects of the present invention, the economic and production-related advantages compared to traditional round fabrics are retained.

The winding of the scrim onto the endless base fabric is also possible with modern winding machines, such as those manufactured by M&A Dieterle, can be done very quickly and cheaply.

The scrim threads can be fixed to the endless base fabric by gluing or welding, for example. Both types of fixation can also be done quickly and possibly in one operation with the winding.
Therefore, a basic structure according to aspects of the present invention offers largely the same production-related advantages as those from FIG EP 1 579 066 known.

However, these basic structures have a significantly increased tensile strength due to the scrim threads. The scrim threads oriented wholly or essentially—with a deviation of max. 20°, preferably max. 10°) in the machine direction can absorb the tensile load; the connection point with the joint connection no longer represents a noticeable weak point in the basic structure in the finished covering, even under heavy loads.

It is therefore also conceivable to design the joint connection in such a way that it is no longer or no longer fully active in a finished covering. This can happen, for example, as a result of damage during the needling of a fleece layer. While such damage can be fatal to prior art fabric, fabric in accordance with aspects of this invention is minimally affected at best.

The marking tendency due to the joint connection can also be reduced or prevented by a connection according to the invention. This can be the case in particular when the basic structure is used in a clothing in such a way that the scrim is arranged on the side of the endless basic fabric that faces the upper side of the clothing in contact with the web. The scrim not only dampens possible markings caused by the joint. A surface that is comparatively smooth towards the fibrous web also avoids or reduces the markings that can be transferred to the paper through the crimps in the fabric, especially in the case of sensitive types of paper.

By suitably adapting the flat fabric and the layer of threads, further properties of the basic structure and the covering produced with it can be easily and efficiently optimized.

Thus, it can be advantageous if the thread count of the scrim is greater than 75% of the MD thread count of the endless base fabric, in particular greater than the MD thread count of the endless base fabric.

The thread density is given as usual in threads per 10 cm.

The permeability of the scrim can be influenced very easily via the thread density of the scrim. As a result, a permeability gradient (in the direction of thickness) can be generated within the basic structure.

The permeability gradient is often chosen in such a way that the side facing the surface in contact with the web (usually the scrim) has a more closed structure than the side facing away (usually the flat fabric).

Frequently, the thread count of the scrim will be up to 125% or 150% of the MD thread count of the endless base fabric.

Thread counts in the scrim of 200% or more of the MD thread count of the endless base fabric are uncommon.

The threads of the scrim can all or at least partially have a diameter between 0.15mm and 1.5mm. The permeability of the scrim and thus the permeability gradient of the basic structure can also be influenced by means of the thread diameter, in combination with the thread density.

The coverage Q of the scrim is advantageously between 40% and 80%, preferably between 50% and 70%. In this area, the fabric provides a sufficiently covered surface and still has sufficient permeability.

Q is the product of the thread density (# threads per 100mm) with the thread diameter (mm)

Example

For example, if there is a scrim made of quadruple thread 2x2x0.2mm with a diameter of 0.5mm for an MD thread density in the wound layer of 115 threads/10cm, the fabric layer has a coverage of Q=57.5%. $$\text{Q}=\left(115*0.5\text{mm}\right)/100mm=0.575-57.5\%$$

→ Die Fadendichte des Fadengeleges beträgt 147% der MD-Fadendichte des FlachgewebesWhen using a flat weave with MD threads made from monofilaments with a diameter of 0.4mm and an MD yarn count of 78 threads/10cm, the result is: $$\text{P}=115/78=1.47$$

→ The thread count of the scrim is 147% of the MD thread count of the flat fabric

In preferred embodiments, the tensile strength of the scrim is at least 75%, in particular at least 100%, particularly preferably at least 125% of the fabric.

Advantageously, it can be provided that at least some, in particular all threads of the scrim comprise or consist of a polyamide, a copolyamide, a polyamide copolyether, a polyurethane or a combination thereof.

When using elastomers such as polyurethanes for the laid threads, it is also very easy to create elasticity in the basic structure. After compression, e.g. in a press nip, this enables rapid expansion of the basic structure or a covering. This can reduce rewetting effects.

The flat fabric for the endless base fabric can be designed in a comparatively simple manner, in particular as a canvas fabric. Both monofilaments and threads can be used.

It has proven to be particularly advantageous if the endless base fabric has a combination of monofilaments and threads in the transverse direction, which can in particular be arranged in an alternating manner. The yarn sequence 1 monofilament - 2x twine is also conceivable. The advantage here is the combination of increased transverse stability of the fabric due to the monofilament cross-direction (CD) yarns and the improved fiber anchoring of an applied fleece layer due to the threads in the CD of the fabric.

With regard to the clothing, the object is achieved by a clothing for a machine for producing or processing a fibrous web, the clothing having at least one basic structure according to one aspect of the invention.

In particularly preferred applications, the fabric is a press felt.

In particular, it can be provided that the covering has at least one layer of non-woven fibers, which is attached to the base structure, in particular by means of needling, and which provides the upper side of the covering that touches the web.

In addition, at least one further layer of fleece fibers can also be provided, which is attached to the basic structure, in particular by means of needling, and which makes the machine-contacting running side of the clothing available.

As known to those skilled in the art, each of these layers of nonwoven fibers can comprise different types of nonwoven fibers and can also be composed of several layers of nonwoven fibers.

In a particularly preferred embodiment, it can be provided that the scrim is arranged on the side of the endless basic fabric that faces the upper side of the clothing that touches the web.

As already described, the marking tendency can be reduced or prevented by the joint connection, which no longer comes into direct contact with the nonwoven overlay, but is largely dampened by the scrim. The scrim not only dampens possible markings caused by the joint. It also avoids or reduces the markings that can be transferred to the paper due to the crimps in the fabric, especially in the case of sensitive paper types.

In addition, as described, the permeability of the scrim can be influenced very easily via the thread density of the scrim. As a result, a permeability gradient can be created within the basic structure.

It is usually desirable if the permeability within the basic structure increases with increasing distance from the surface in contact with the web. In this case, the permeability of the scrim can be reduced very easily—by increasing the thread density and/or the thread diameter.

In addition to the basic structure, it can also be provided that the clothing comprises a further fabric layer, the further fabric layer being arranged in particular on the side of the endless basic fabric facing away from the upper side of the clothing in contact with the web.

1. a) Bereitstellen eines Flachgewebes
2. b) Verbinden der beiden stirnseitigen Kanten des Flachgewebes mittels einer Fügeverbindung unter Ausbildung eines endlosen Grundgewebes
3. c) Spiralförmiges wickeln einer Fadenschar auf das endlose Grundgewebe unter Ausbildung eines Fadengeleges
4. d) Fixieren des Fadengeleges auf dem Grundgewebe

With regard to the method, the object is achieved by a method for producing a basic structure for a cover for a machine for producing or processing a fibrous web, comprising the steps:

1. a) Providing a flat weave
2. b) Connecting the two front edges of the flat fabric by means of a joint to form an endless base fabric
3. c) Spiral winding of a sheet of threads onto the endless base fabric, forming a scrim
4. d) Fixing the scrim on the base fabric

For steps c) and d), it is expedient if the endless base fabric is guided over at least two rotatable roller elements and, if necessary, is tensioned.

This provides a stable and defined area for laying down the group of threads.

The group of threads usually consists of a plurality of threads which are arranged next to one another and are wound spirally at the same time in step c). In principle, it is also possible to produce the scrim from a single thread by spiraling. With the widths of the current clothing of 10m or more, and with the desired high thread densities of the thread scrim of 100 threads/10cm or more, this would lead to a very long winding process. Advantageously, therefore, bundles of threads consisting of several threads are wound up. Thread sheets of 2, 10, 50, 100 or more threads are possible.

The wider the group of threads, the fewer turns are required to produce the scrim. However, if the group of threads is too wide, the oblique, spiral winding at the edges of the basic structure results in a large amount of rejects, which should be avoided.

In addition, if the number of threads is too wide, a larger spiraling angle must be selected for the spiraling, as a result of which the threads of the scrim deviate further from the MD direction, which can also be undesirable in terms of tensile strength.

It has therefore turned out to be advantageous if the bundle of threads is wound onto the endless base fabric with a width of between 1 cm and 25 cm, in particular between 2 cm and 15 cm.

With a width of 15 cm and an exemplary thread count of 110 threads/10 cm, this results in a group of threads with around 165 threads.

The front edges of the flat fabric can be connected in various ways. It is known from the prior art, for example, to connect the edges by welding, for example by ultrasonic welding or else (laser) transmission welding. In this case, connection elements can also be used, such as threads or tapes, in particular also absorbent connection elements, which are then connected to the front edges by welding.

Alternatively, it is also possible to connect the front edges to one another by gluing.

In principle, it is also possible to connect the two edges by means of a woven seam, as is known from the field of forming fabrics. However, since such a woven seam is very complex to produce and the advantage of the higher tensile strength is not necessary in embodiments according to various aspects of the invention, a woven seam is rarely used.

The threads of the scrim can also be fixed in place on the endless base fabric in various ways. Here too, for example, the options of gluing and (laser) transmission welding are available. In particular, the same method can be used for fixing the scrim threads as for connecting the front edges.

In advantageous embodiments of the method, steps c) and d) can take place in a common process.

For example, the fixation can take place by means of spray adhesive application to the endless base fabric in the range of 15-100 g/m 2 , preferably 25-50 g/m 2 spray adhesive.

Such a spray adhesive can preferably be sprayed onto the endless base fabric during the winding process, just before the threads are wound onto it. If necessary, a pressure element can then be provided, in particular in the form of a pressure roller, which presses the scrim threads onto the endless base fabric.

A reactive hot-melt adhesive with a melting point <200° C., preferably <180° C., can preferably be used. In particular, it can be advantageous if the hardened hot-melt adhesive still has an elastic component.

Due to the fabric structure, the wound yarns are usually only bonded to the fabric in sections or at certain points, i.e. small sections along the wound yarns are not bonded to the fabric layer.

The bond is also to be regarded as temporary, since the bond can be partially or even predominantly or completely detached in the subsequent production steps such as needling the felt structure or at the latest during the run in the paper machine.

Alternatively, a fixing process using transmission welding, e.g. using NIR transmission welding, is also possible. Either the MD yarns of the scrim or some or all (MD/CD) yarns of the flat fabric tape can be NIR absorbent. This can be done, for example, by adding absorber additives such as carbon black.

The connection of the MD yarns is usually preferably not carried out over the entire surface, but materially bonded connection points of the MD yarns of the scrim with the fabric are created at distances of e.g. >5mm, preferably >10mm, but <50mm. This is possible, for example, with a laser beam in the form of a point that travels over the sheet of threads and fabric during winding (e.g. from left to right) and creates a sinusoidal weld line in the area of the sheet of threads with the fabric layer.

The invention is explained below with reference to figures. The invention is not limited to the embodiments shown here.

• 1 zeigt schematisch die Herstellung einer Grundstruktur gemäß einem Aspekt der vorliegenden Erfindung
• 2a zeigt einen Ausschnitt einer Bespannung gemäß dem Stand der Technik
• 2b zeigt einen Ausschnitt einer Bespannung gemäß einem Aspekt der vorliegenden Erfindung.

The figures show in detail:

• 1 FIG. 12 shows schematically the manufacture of a basic structure according to an aspect of the present invention
• 2a shows a detail of a covering according to the prior art
• 2 B shows a section of a covering according to one aspect of the present invention.

1 shows an endless base fabric 1 which is formed from a flat fabric in which the front edges are connected by means of a joint 7 . This joint connection can be a welded or glued connection 7, for example. The flat weave can advantageously be in the form of a plain weave.

The endless base fabric 1 is guided around two rollers 10 . The endless base fabric 1 can also be stretched over these rollers 10 in order to ensure a stable surface for laying down the group of threads 3a.

A sheet of threads 3a is deposited on the endless base fabric 1 with a winding head 4, while the endless base fabric 1 moves away underneath. The winding head 4 can be moved transversely to the running direction than in the CD direction. The CD offset can be controlled in such a way that the winding head 4 moves on by exactly the width of the sheet of threads 3a during a full revolution of the endless base fabric 1. In this way, the group of threads 3 are wound spirally onto the endless base fabric 1 by forming a scrim 2 by rotating them several times.

in the in 1 In the example shown, a gluing device 5 is provided for fixing the threads 3 of the group of threads 3a. The gluing device 5 sprays or pours an adhesive 6 onto the endless base fabric 1 before the threads 3 of the scrim 3 are deposited on it. For better fixation, the threads 3 can also be pressed onto the endless base fabric 1 after they have been deposited by a pressure element (not shown in the figure), for example a pressure roller.

Alternatively or additionally, a welding process can also be used to fix the threads 3 of the thread structure 2 . For example, after the threads 3 have been laid down, an NIR laser can be provided. With this, the threads 3 of the scrim 2 are connected to the fabric threads of the base fabric 1 by means of transmission welding. The connection can be carried out selectively.

2a shows a covering known from the prior art in the form of a press felt. A flat fabric is joined together to form an endless base fabric 1 by means of a joint 7 . The joint 7 was realized in that the two front edges of the flat fabric are welded to a connecting element 9 . This connecting element 9 can be a connecting thread 9, for example, which is made absorbing by adding a suitable additive for light in a wavelength range of the NIR spectrum. If the fabric threads are made of a polyamide, they are largely transparent to NIR rays. The front edges can then be welded using NR transmission welding. A layer of non-woven fibers 8 is attached to the base fabric 1, which provides the paper-contacting top side. It is easy to see that the base fabric 1 has a different structure in the area of the joint 7 . Since the base fabric 1 is in direct contact with the layer of fleece fibers 8, there is a risk that these structural differences in the base fabric 1 will push through the soft fleece layer 8 onto the paper to be produced.

the inside 2 B Felt shown according to one aspect of the invention develops the fabric of 2a further. She inserts between the endless Base fabric 1 and the layer of fleece fibers 8 a scrim 2 of spiral scrim threads 3 a. The scrim threads 3 are connected to the endless base fabric 1 at discrete fixing points 11 . This connection at the fixing points 11 can take place, for example, by gluing or welding. Since the joint connection 7 is no longer in direct contact with the soft fleece layer 8, the joint connection 7 is prevented from being pressed through onto the paper web. The tensile strength of the covering is also significantly increased by aligning the scrim threads 3 in the MD direction. This significantly reduces the requirements for the strength of the joint.

Reference List

1

Endless ground fabric

2

scrim

3

thread

3a

sheet of threads

4

winding head

5

gluing device

6

adhesive

7

joint connection

8th

Layer of fleece fibers

9

fastener

10

roller

11

fixation point

CD

transverse direction

md

machine direction

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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.

Patent Literature Cited

• EP 1579066 [0003, 0018]
• EP 3687774 [0003]

Claims (15)

Basic structure for a cover for a machine for producing or processing a fibrous web, the basic structure having an endless basic fabric (1), the endless basic fabric (1) being designed as a flat fabric which, by connecting its two front edges by means of a joint (7), is made endless, with the joint connection (7) in particular either running transversely to the running direction of the later covering or deviating from this transverse direction (CD) by a maximum of 20°, in particular a maximum of 10°, characterized in that the basic structure also has a scrim (2). , which is made up of a group (3a) of threads (3) which are arranged in a spiral on the endless base fabric (1) and are fixed to it, the threads (3) forming the thread structure (2) essentially in the running direction (MD) are oriented towards the later covering and deviate from this direction by a maximum of 20°, preferably by a maximum of 10° basic structure according to claim 1 , characterized in that the joint (7) is a welded joint and/or an adhesive joint. Basic structure according to one of the preceding claims, characterized in that the scrim (2) is fixed to the endless base fabric (1) by gluing or welding. Basic structure according to one of the preceding claims, characterized in that the thread count of the scrim (2) is greater than 75% of the MD thread count of the endless base fabric (1), in particular greater than the MD thread count of the endless base fabric (1), wherein the Thread density is rated in threads per 10cm. Basic structure according to one of the preceding claims, characterized in that at least some, in particular all threads (3) of the scrim (2) are designed as multifilament yarns and/or twisted threads made from monofilaments and/or twisted threads made from monofilaments and multifilaments. Basic structure according to one of the preceding claims, characterized in that at least some, in particular all threads (3) of the thread structure (2) have a diameter of between 0.15mm and 1.5mm. Basic structure according to one of the preceding claims, characterized in that at least some, in particular all threads (3) of the thread structure (2) comprise or consist of a polyamide, a copolyamide, a polyamide copolyether, a polyurethane or a combination thereof. Basic structure according to one of the preceding claims, characterized in that the endless basic fabric (1) has a combination of monofilaments and threads in the transverse direction, which are in particular arranged alternately. Covering, in particular press felt, for a machine for producing or processing a fibrous web, characterized in that the covering has at least one basic structure according to one of the preceding claims. Covering according to claim 9 , characterized in that the covering has at least one layer of non-woven fibers (8) which is attached to the base structure, in particular by means of needling, and which provides the upper side of the covering that is in contact with the web. Covering according to one of claims 9 or 10 , characterized in that the scrim (2) is arranged on the side of the endless base fabric (1) facing the upper side of the clothing in contact with the web. Covering according to one of claims 9 until 11 characterized in that the covering comprises a further fabric layer, the further fabric layer being arranged in particular on the side of the endless basic fabric (1) facing away from the upper side of the covering in contact with the web. Method for producing a basic structure for a fabric for a machine for producing or processing a fibrous web, comprising the steps a) Providing a flat weave b) joining the two front edges of the flat fabric by means of a joint (7) to form an endless base fabric (1) c) spiral winding of a group of threads (3b) onto the endless base fabric (1) to form a scrim (2) d) Fixing the scrim (2) on the base fabric procedure according to Claim 13 , characterized in that steps c) and d) take place in a common process Method according to one of Claims 13 or 14 , characterized in that the A sheet of threads (3b) is wound onto the endless base fabric (1) with a width of between 1 cm and 25 cm, in particular between 2 cm and 15 cm.

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