CN114026285A

CN114026285A - Twined and made net blanket

Info

Publication number: CN114026285A
Application number: CN202080046534.1A
Authority: CN
Inventors: R.霍尔; C.菲策尔
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2019-06-26
Filing date: 2020-06-19
Publication date: 2022-02-08
Also published as: DE102019117172A1; EP3990695A1; WO2020260153A1; US20220259804A1

Abstract

The invention relates to a clothing (10) for a machine for producing a fibrous web, in particular a paper, cardboard or tissue web, comprising a first layer (12) and a second layer (22), the first layer (12) being formed by first strip-shaped structures (14) oriented parallel to one another, the second layer being arranged on the first layer (12) and connected to the first layer (12), and the second layer being formed by second strip-shaped structures (24) oriented parallel to one another, wherein not only adjacent first strip-shaped structures (14) are spaced apart from one another, but also adjacent second strip-shaped structures (24) are spaced apart from one another, so that a connection formed by the first layer (12) and the second layer (22) has a plurality of openings (20) for dewatering the fibrous web. The invention also relates to a method for producing such a clothing.

Description

Twined and made net blanket

Technical Field

The invention relates to a clothing for a machine for producing a fibrous web, in particular a paper, cardboard or tissue web, comprising a first layer, which is formed by first strip-shaped structures oriented parallel to one another, and a second layer, which is arranged on and connected to the first layer and which is formed by second strip-shaped structures oriented parallel to one another. The invention also relates to a method for producing such a clothing.

Background

In a machine for producing a fibrous web, in particular a paper, paperboard or tissue web, a fibrous suspension is first applied to a forming wire in a forming section. By removing water from the suspension initially mainly comprising water, a true fibrous web is formed on the forming wire. In the machine, the forming section is followed by other sections, i.e. usually at least one press section and a drying section, where additional moisture is removed from the fibrous web by mechanical pressure and/or heat, and the manufactured product can then be rolled up at the end of the machine. In all these sections, a continuously circulating clothing is provided here, which carries the fibrous web and is permeable for the purpose of dehumidifying it.

Nowadays, clothing is mostly made of thermoplastic monofilaments by weaving, but other manufacturing methods are also known. The clothing can be configured, for example, as a spiral screen or as a perforated, in particular laser-perforated, film. Furthermore, the clothing can also be produced in that a thread or strip-like structure is wound in a spiral on two rolls with parallel longitudinal axes, wherein the lateral edges of the thread or strip-like structure are fixedly connected to each other in order to stabilize the structure and/or at least one further layer of the spirally wound thread or strip-like structure is applied to the first layer and connected thereto. Such a clothing is known, for example, from document EP 1354094B 1.

Such a clothing has the disadvantage that the production process is rather complicated, since finally a large number of perforations must also be introduced into the clothing in order to impart the necessary permeability to the clothing.

Disclosure of Invention

The technical problem underlying the present invention is therefore to provide a clothing which overcomes or at least reduces the disadvantages of the prior art. In particular, the production of the corresponding clothing should be simpler to implement.

The above-mentioned technical problem is solved by the features of the independent claims. The dependent claims have advantageous further developments of the invention.

The above-mentioned technical problem is therefore solved according to a first aspect of the present invention by a clothing of the kind mentioned at the outset, which has, inter alia, the following features: not only are adjacent first strip-like structures spaced apart from each other, but also adjacent second strip-like structures are spaced apart from each other, so that the connection body formed by the first layer and the second layer has a plurality of openings for dewatering the fibrous web.

In this way, it is no longer necessary to introduce perforations into the clothing as a separate method step in order to impart the required permeability to the clothing, since the through-openings are already produced during the winding. Even if perforations are still introduced next, these need not be as many as in the prior art in order to achieve the same permeability. The production effort can thus be reduced in a simple manner. Also, the amount of raw material required to manufacture the clothing is reduced.

In principle, it is conceivable to use the clothing according to the invention also in the machine as a forming wire or as a press felt. The advantages of the invention are particularly well utilized if the clothing according to the invention is used as a drying screen. In this case, it can be provided that the drying screen is essentially composed of only the first and second layer, i.e. without further layers or surface layers. The seaming element is also eliminated by the winding process, since the clothing already has a continuous shape during production. However, if necessary, the wound-up clothing can also be separated and subsequently provided with seam elements, for example to make it easier to introduce the clothing into the machine. What is also needed is reinforcement in the edge area of the clothing. In the case of use as press felts, however, the wound structure must be provided with at least one further layer or surface layer, in particular a felt surface layer, in order for the press felt to fulfill its intended function. Further precautions are to be taken against the forming wire, since the only entangled structure would otherwise carry the risk of undesired marking in the fibrous web.

Preferably, it is provided that the first strip-like structure has a first angle with respect to the cross-machine direction or cross-machine direction of the clothing, the first angle being greater than 0 ° and less than 90 °, preferably between 45 ° and 80 °, and the second strip-like structure has a second angle with respect to the cross-machine direction of the clothing, the second angle being greater than 90 ° and less than 180 °, preferably between 100 ° and 135 °. The machine direction of the clothing or the machine direction of the paper pattern corresponds here to the machine direction of the clothing, i.e. the direction in which the clothing moves in the machine during regular use. Conversely, the cross-machine direction refers to a direction oriented orthogonal to the machine direction in the plane of the clothing.

It can be provided here that the second angle corresponds substantially to 180 ° minus the first angle. In other words, the first strip-like structure extends mirror-symmetrically with respect to the second strip-like structure with reference to the machine direction in the plane of the clothing. The first strip-like structure and the second strip-like structure are thereby able to absorb tensile forces acting on the clothing in the machine direction to the same extent.

It is furthermore preferred that the first strip-like structure has a substantially rectangular cross-sectional shape with a first thickness and a first width, and that the second strip-like structure has a substantially rectangular cross-sectional shape with a second thickness and a second width. Here, the width is measured in the plane of the clothing and the thickness is measured orthogonally with respect to the width. On the one hand, a good contact surface between the first strip-like structure and the second strip-like structure can be provided by this flat cross-sectional shape, so that a stable connection of the two layers can be ensured. On the other hand, when a clothing is used as a drying screen, good heat transfer can be ensured, since the contact surface between one side and the fibrous web and the contact surface between the other side and the heated drying cylinder are large. The term "substantially rectangular" means that the cross-sectional shape may also deviate somewhat, for example with rounded corners or with a slight convexity on the sides.

The first thickness may be different from the second thickness. In particular, for the purpose of undesired marking, it is advantageous if, in the case of regular use, the layer of the first and second layers facing the fibrous web has a strip-like structure with a smaller thickness than the strip-like knots of the layer facing away from the fibrous web in the case of regular use. The layer facing away from the fibrous web is therefore used primarily for structural stability because of its greater thickness, while the layer facing the fibrous web is provided with only minor irregularities on the contact surface with the fibrous web because of its smaller thickness.

It can be provided that the first width is substantially equal to the second width, wherein the first width and the second width preferably have a value between 1mm and 30mm, further preferably between 1mm and 15 mm. These widths have proven to be particularly advantageous when the clothing according to the invention is used as a drying screen.

The openings may have a substantially rectangular, preferably diamond-shaped form, wherein preferably all openings formed therewith have substantially the same form. By "shape of the through opening" is herein understood the shape seen when the clothing is viewed orthogonally to the plane of the clothing.

The first strip-like structure and the second strip-like structure can be connected to one another in a material-fit manner, in particular welded to one another. Thereby constituting a secure hold between the strip-like structures of the two layers. The weld may be achieved, for example, by hot air, hot wedge, ultrasonic, or hot extrusion. Additionally or alternatively, the material-to-material connection can be formed by an adhesive.

In particular, the first strip-like structure and the second strip-like structure can be connected to one another by laser welding, for example by an NIR laser. For this purpose, it is advantageous for the first strip-like structure to have a property of absorbing radiation of laser light, in particular of NIR laser light, which is different from the second strip-like structure. The laser can thereby be irradiated through one of the two layers without being significantly absorbed, while the other layer absorbs the laser, melts and, when cooled under suitable pressure, constitutes a material-fitting weld. Of course, alternatively or additionally, an auxiliary material may be introduced between the first and second strip-like structures at the crossing position thereof before irradiation with laser light, such as

In order to generate the laser absorption effect locally in this case. If the laser beam is directed into the gap between the first strip-shaped structure and the second strip-shaped structure to be connected to it, the two strip-shaped structures can also have the same laser absorption properties, which can be colored black in particular.

These strip-like structures are preferably made substantially of plastic, in particular of meltable thermoplastic. However, it is also possible in principle to use unstretched material here. In order to achieve the necessary strength of the strip-like structures, however, it is provided in a further development of the invention that the first strip-like structures and/or the second strip-like structures consist of a uniaxially stretched plastic or a biaxially stretched plastic, wherein preferably the biaxially stretched film is cut to the shape of the strip-like structures, or that the first strip-like structures and/or the second strip-like structures consist of a plastic which is provided with fillers and/or reinforcing fibers for increasing the strength. "uniaxial stretching" here means that the polymer chains of the plastic have already acquired a preferential direction by means of tensile forces, in the extreme case all oriented in the same direction. The stronger the material is uniaxially stretched, the greater its modulus of elasticity in the direction of stretching and the less the material will elongate further in that direction under the force. Uniaxial stretching typically already occurs when the material is extruded through a die in a heated state during the extrusion process. Shear forces acting on the material in the die result in a preferential orientation of the polymer chains in the material. "biaxially stretched" as used herein means that the material is stretched in two mutually orthogonal directions to essentially the same extent, and therefore there is no definite preferential direction of the polymer chains. In contrast, the material has substantially the same modulus of elasticity in both directions in which it is stretched, which is greater than that of an unstretched material. In addition to or as an alternative to stretching, the strip-like structure may be provided with fillers and/or reinforcing fibers to increase the strength. The filler and/or reinforcing fibers can be introduced into the strand-like structure or co-extruded with the material, for example, as it is extruded. Aramid fibers or glass fibers, for example, are conceivable here.

As already mentioned above, in order to further increase the permeability of the clothing, it is advantageous if the first strip-like structure and/or the second strip-like structure additionally has perforations, in particular laser-drilled perforations, wherein these perforations are preferably smaller than the through openings.

According to another aspect, the invention also relates to a method for manufacturing the previously described clothing according to the invention, comprising the steps of: a) producing a first layer by spirally winding a first strip-like structure on two rolls having longitudinal axes parallel to each other, wherein gaps are formed between turns of the first layer such that the side edges of the first strip-like structure do not contact each other; and b) producing a second layer on the first layer by spirally winding a second strip-like structure on the two rollers, wherein gaps are formed between turns of the second layer such that the side edges of the second strip-like structure do not contact each other, wherein the strip-like structures of the two layers cross such that the connection formed by the first layer and the second layer has a plurality of openings for dewatering the fibrous web. Since the finished clothing requires two defined side edges extending in the machine direction, the clothing formed in this way finally requires post-treatment, such as cutting and, if necessary, reinforcement of the side edges. By cutting, each layer has a structure consisting of a plurality of individual strip-like structures, depending on the length of the clothing and the selected winding angle, although the manufacture of each layer can be carried out from only one strip-like structure.

In the method, it can be provided that the first layer is connected to the second layer material in a form-fitting manner, preferably by welding, more preferably by laser welding, wherein the connection is optionally carried out during the production of the second layer in step b) or as a separate step c) after step b). In the first case, the robot arm that winds the second strip-like structure around the first strip-like structure may, for example, simultaneously irradiate the crossing position with laser light to produce the weld. Preferably welded to a base, such as a larger drum or roller. Similar techniques are known from the manufacture of larger pressure vessels.

As already mentioned above, it can be provided that the side edges of the clothing are subsequently post-treated, in particular cut and/or reinforced.

Drawings

An exemplary embodiment of a clothing according to the invention and a manufacturing method for such a clothing according to the invention are explained in more detail below with reference to fig. 1 to 3. Wherein:

fig. 1 shows a top view of an imaginary part illustrating the structural design in a line of sight orthogonal to the plane of the clothing;

FIG. 2 shows a cross-sectional view of a first strip-like structure;

FIG. 3 shows a cross-sectional view of a second stripe-like structure;

fig. 4 shows a schematic representation of a manufacturing process, wherein the manufacture of the first layer is shown here by spiral winding on two rolls; and is

Fig. 5 shows a schematic view similar to fig. 4, however from a different perspective.

Detailed Description

In fig. 1, an imaginary part of a clothing 10 according to the invention, in particular of a drying screen, is schematically shown, wherein the line of sight direction is oriented orthogonally to the plane in which the clothing 10 lies. In fig. 1, the machine direction MD of the clothing 10 is directed upwards or in the vertical direction, whereas the cross-machine direction CD of the clothing 10 in fig. 1 is directed to the right or in the horizontal direction. The clothing 10 is substantially formed by a first layer 12 and a second layer 22 arranged on the first layer 12 and fixedly connected thereto, the first layer 12 being intended to face away from the fibrous web in the intended use of the clothing 10 in a paper machine, the second layer 22 facing towards the fibrous web in the intended use of the clothing 10 in a paper machine. The first layer 12 is formed from a plurality of first strip-like structures 14, which are all oriented parallel to one another, wherein directly adjacent first strip-like structures 14 are spaced apart from one another in such a way that their side edges 16, 18 do not touch one another. The first strip-like structure 14 is oriented at an angle α with respect to the cross-machine direction CD, which may be 70 ° here, for example. The second layer 22 is formed by a plurality of second strip-like structures 24, which are likewise all oriented parallel to one another, wherein directly adjacent second strip-like structures 24 are spaced apart from one another in such a way that their side edges 26, 28 do not touch one another. The second strip-like structure 24 is oriented at an angle of 180 deg. -alpha, i.e. here, for example, 180 deg. -70 deg. -110 deg., with respect to the cross-machine direction CD, so that the first strip-like structure 14 and the second strip-like structure 24 extend mirror-symmetrically to each other with respect to an imaginary plane oriented in the MD direction, which is orthogonal to the plane of the drawing or the plane of the fabric.

As can be seen in fig. 2, the first stripe structures 14 have a substantially rectangular cross-sectional shape with a first thickness d1 and a first width b 1. Likewise, the second strip-like structure 24 has a substantially rectangular cross-sectional shape with a second thickness d2 and a second width b2, as can be seen in fig. 3. In this example, the first width b1 may be, for example, 2.2mm, which is comparable to the second width b 2. However, the first thickness d1 may be, for example, 0.5mm, which is slightly larger than the second thickness d2, and the second thickness d2 may be, for example, 0.3 mm. The first width b1 and the second width b2 are smaller than a distance a between two adjacent first stripe structures 14 or two adjacent second stripe structures 24 (see fig. 1). The gap or distance a thus formed between two directly adjacent strip-

like structures

14, 24 of the

respective layer

12, 22 may be, for example, 1 mm.

The diamond-shaped openings 20 formed in the clothing 10 by the two

layers

12, 22 can be clearly seen in fig. 1. These openings 20 serve for dewatering the fibrous web transported on the clothing 10. At the same time, the clothing 1O according to the invention, when used in a regulated manner, provides a large, substantially flat contact surface both on the side facing away from the fibrous web and towards the drying cylinder, and on the side facing away from the fibrous web, which contact surface allows good heat transfer and thus effective drying of the fibrous web.

The first strip-like structure 14 and the second strip-like structure 24 can be manufactured as monoaxially highly drawn monofilaments from a thermoplastic material by an extrusion process, wherein the dies of the extruder have a corresponding rectangular shape. Furthermore, the first strip-like structure 14 and the second strip-like structure 24 are preferably welded to each other at their respective intersection points with an NIR laser. For this purpose, the first stripe structures 14 and/or the second stripe structures 24 may have laser light absorbing properties, which may be colored black, among others.

Fig. 4 and 5 schematically show a possible manufacturing process for the clothing 10 according to the invention from two different perspectives, wherein in both figures only the first layer 12 of the clothing 10 is shown. The first strip-like structure 14 is wound in a spiral on two spaced-apart

rollers

30, 32 having parallel longitudinal axes. Here, the winding is carried out such that the side edges 16, 18 of two directly adjacent turns of the first strip-like structure 14 do not touch but have a distance a from one another. Thus, the respective outer surfaces O of the two

rollers

30, 32 are well visible even in their wrapped areas.

The second strip-like structure 24 is then wound spirally on two

rollers

30, 32 and on the first strip-like structure 14 of the first layer 12 so as to form the second layer 22. The winding angle is selected here such that the diamond-shaped openings 20 shown in fig. 1 are formed. Finally, the side edges of the clothing 10 are cut and reinforced in the machine direction MD to secure the free ends of the first and second strip-

like structures

14, 24. Optionally, the first strip-like structure 14 and/or the second strip-like structure 24 may additionally be perforated, preferably by means of a corresponding high-power laser light source.

List of reference numerals:

10-mesh blanket

12 first layer

14 first strip structure

16 side edge

18 side edge

20 through opening

22 second layer

24 second stripe structure

26 side edge

28 side edge

30 rollers

32 rollers

Angle alpha

CD cross machine direction

b1 first width

b2 second width

d1 first thickness

d2 second thickness

MD machine direction

O outer surface

Claims

1. Blanket (10) for a machine for producing a fibrous web, in particular a paper, paperboard or tissue web, comprising a first layer (12) and a second layer (22), the first layer (12) being composed of first strip-like structures (14) oriented parallel to one another, the second layer being arranged on the first layer and connected to the first layer (12), the second layer being composed of second strip-like structures (24) oriented parallel to one another,

characterized in that not only adjacent first strip-like structures (14) are spaced apart from each other, but also adjacent second strip-like structures (24) are spaced apart from each other, so that the connection body formed by the first layer (12) and the second layer (22) has a plurality of through openings (20) for dewatering the fibrous web.

2. Blanket (10) according to claim 1,

characterized in that the clothing (10) is a drying screen, which preferably consists only of the first layer (12) and the second layer (22).

3. Blanket (10) according to claim 1 or 2,

characterized in that said first strip-like structure (14) has a first angle (a) with respect to the cross-machine direction (CD) of the clothing (10) which is greater than 0 ° and less than 90 °, preferably between 45 ° and 80 °, and said second strip-like structure (24) has a second angle with respect to the cross-machine direction (CD) of the clothing (10) which is greater than 90 ° and less than 180 °, preferably between 100 ° and 135 °.

4. Blanket (10) according to claim 3,

characterized in that said second angle substantially corresponds to 180 minus the first angle (alpha).

5. Clothing (10) according to one of the previous claims,

characterized in that the first strip-like structure (14) has a substantially rectangular cross-sectional shape with a first thickness (d1) and a first width (b1), and the second strip-like structure (24) has a substantially rectangular cross-sectional shape with a second thickness (d2) and a second width (b 2).

6. Blanket (10) according to claim 5,

characterized in that the first thickness (d1) differs from the second thickness (d2), wherein preferably the layers (22) of the first layer (12) and the second layer (22) facing the fibrous web have a stripe-like structure (24) with a smaller thickness (d2) than the stripe-like structure of the layers (12) facing away from the fibrous web in the intended use.

7. Blanket (10) according to claim 5 or 6,

characterized in that said first width (b1) is substantially equal to said second width (b2), wherein said first width (b1) and said second width (b2) preferably have a value between 1mm and 30mm, further preferably between 1mm and 15 mm.

8. Clothing (10) according to one of the previous claims,

characterized in that the through openings (20) have a substantially rectangular, preferably diamond-shaped form, wherein preferably all through openings (20) formed in this way have substantially the same form.

9. Clothing (10) according to one of the previous claims,

characterized in that the first strip-like structure (14) and the second strip-like structure (24) are connected to each other in a material-fit manner, in particular welded to each other.

10. Clothing (10) according to one of the previous claims,

characterized in that the first strip-like structure (14) has a property of absorbing radiation of laser light, in particular of NIR laser light, which is different from the second strip-like structure (24).

11. Clothing (10) according to one of the previous claims,

characterized in that the first strip-like structure (14) and/or the second strip-like structure (24) consist of a monoaxially or biaxially stretched plastic, wherein preferably a biaxially stretched film is cut in the shape of the strip-like structure (14, 24), or the first strip-like structure and/or the second strip-like structure consist of a plastic which is provided with fillers and/or reinforcing fibers for increasing the strength.

12. Clothing (10) according to one of the previous claims,

characterized in that the first strip-like structure (14) and/or the second strip-like structure (24) additionally have perforations, in particular laser-perforated perforations, for increasing the permeability of the clothing (10), wherein the perforations are preferably smaller than the through openings (20).

13. A method for manufacturing a clothing (10) according to one of the preceding claims, comprising the following steps:

a) -manufacturing said first layer (12) by spirally winding a first strip-like structure (14) on two rollers (30, 32) having longitudinal axes parallel to each other, wherein gaps are formed between turns of the first layer (12) such that the side edges (16, 18) of said first strip-like structure (14) do not touch each other,

b) -manufacturing the second layer (22) on the first layer (12) by spirally winding a second strip-like structure (24) on the two rollers (30, 32), wherein gaps are formed between turns of the second layer (22) such that the side edges (26, 28) of the second strip-like structure (24) do not touch each other,

wherein the strip-like structures (14, 24) of the two layers (12, 22) intersect in such a way that the connection body formed by the first layer (12) and the second layer (22) has a plurality of openings (20) for dewatering the fibrous web.

14. The method of claim 13, wherein the first and second optical elements are selected from the group consisting of,

characterized in that the first layer (12) is connected to the second layer (22) in a material-fit manner, preferably by welding, more preferably by laser welding, wherein the connection is optionally carried out during the production of the second layer (22) in step b) or as a separate step c) following step b).

15. The method according to claim 13 or 14,

characterized in that the side edges of the clothing (10) are subsequently post-treated, in particular cut and/or reinforced.