WO2014001217A1

WO2014001217A1 - Method for introducing through-holes with the aid of different laser beams into a sheet-like substrate, in particular a band-like sheet; fabric for a papermaking machine having different holes

Info

Publication number: WO2014001217A1
Application number: PCT/EP2013/063009
Authority: WO
Inventors: Michael Straub
Original assignee: Voith Patent Gmbh
Priority date: 2012-06-25
Filing date: 2013-06-21
Publication date: 2014-01-03
Also published as: DE102012210768A1

Abstract

The invention relates to a method for introducing through-holes (2, 3) with the aid of laser beams into a sheet-like substrate, in particular into a band-like sheet (1), which is intended for use as fabric in a papermaking machine, wherein the through-holes (2, 3) are introduced in the thickness direction (d) of the substrate or sheet (1). Provision is furthermore made for a particular number of through-holes (2) to be produced with the aid of a CO₂ laser and for a particular number of through-holes (3) to be produced with the aid of a UV laser, wherein any desired defined shapes and sizes of through-holes (3.1, 3.2, 3.n) are produced and introduced in combination with one another into the substrate or sheet (1). The invention also relates to a fabric for papermaking machines having different holes (2, 3, 3.1, 3.n).

Description

METHOD OF INTRODUCING CONTINUOUS DRILLING THROUGH DIFFERENT LASER RADIATION INTO A SURFACE-SHAPED SUBSTRATE, IN PARTICULAR A TAPE-FOIL; TENSION FOR A PAPER MACHINE

MI DIFFERENT HOLES

5 The invention relates to a method for introducing through-holes with

Help of laser beams in a flat substrate, in particular in a band-shaped film, which is intended for use as a covering in a paper machine, wherein the through holes in the thickness direction of the substrate or

the film are introduced.

0

At present, in a paper machine, mainly in the former, flatwoven structures are used as the sheet forming release medium.

It has already been thought of ways in which flat substrates, such as

5 sheets of plastic are used. In these band-shaped films can

Perforations using laser technology or mechanically working tools are introduced. Thus, the films can be very well used as a fabric in a paper machine, for example as dewatering belts. In DE A1 10 2010 040 089 it is disclosed, for example, that in a polymeric

Material or substrate pores or passages are preferably introduced by means of a laser. The polymeric material is formed as a band and serves as a covering, in particular forming fabric for supporting and supporting a pulp mixture from which later the finished fibrous web or paper web

5 arises within a paper machine.

In practice, laser drilling is currently preferred with CO2 lasers. These lasers are relatively inexpensive, work fast and provide sufficient power.

However, the cylindrical holes drilled therewith have a bad one

0 Reproducibility of hole size and hole shape, especially along the

Axial direction of the holes. In addition, crater-shaped melt edges form around the holes, which must be removed consuming. Other laser types, such as UV lasers, short pulse lasers or lasers with green light are conceivable in principle, but currently not or only partially able to provide the required speeds for drilling. Their application would lead to extremely long drilling times.

The object of the invention is to specify a method for laser drilling, with which the drilling times for a band-shaped film intended for use as a covering in a paper machine can be shortened. In addition, various hole geometries should be produced. It is a further object of the invention to provide a papermachine fabric in the form of a sheet-like substrate, in particular a laser-drilled film with various hole geometries.

The object of the invention is achieved with the features of claims 1 and 16.

According to claim 1 it is provided that a certain number of through holes are made by means of a first laser, in particular a CO2 laser, and a certain number of through holes by means of a second laser, in particular a UV laser, wherein the first laser at a longer operating wavelength than the second laser works.

With the method according to the invention one proposes at the same time "two birds with one stone". On the one hand, the drilling times are shortened considerably. By combining the use of a first laser operating at a longer working wavelength with a second laser operating at a shorter operating wavelength than the first laser, a certain proportion of the holes or through-holes can, in a very short time, by the first laser, so to speak "shot" and by means of the second laser, which works more precisely and / or reproducible and / or controllable with respect to the producible size and / or geometry of the holes generated or through holes as the first laser, another portion of the holes or through holes produced become. This makes it possible with the aid of the first laser, a so-called pre-perforation of the substrate for "coarse" setting a desired permeability and / or a desired dewatering characteristic and fine tuning to the desired permeability and / or the desired dewatering characteristic of the laser by means of the second precise laser working Substrate to make.

Advantageous embodiments of the method emerge from the subclaims. By means of the solution according to the invention, it is possible, in particular, for the forms and sizes of through-bores to be defined as desired by means of the second laser and to be introduced into the substrate or the film in combination with one another. Preferably, the fabric has a useful area which is bingbar in their intended use with a fibrous web in contact, wherein the substrate is provided in the region of the useful area with the first laser and the second laser. As a result of this measure, the usable area which can be brought into contact with the fibrous web is processed.

Preferably, the first laser is a CO2 laser and the second laser is a UV laser. CO2 lasers are very good as they can generate a large number of holes in a very short time. UV lasers can be used very flexibly for the stated purpose and can easily reproduce any hole sizes and hole shapes, in particular along the axial direction.

It has proved to be advantageous if the ratio of the number of bores is produced as follows:

The number of through holes drilled with the second laser are in the ratio of 1: 1 to 1:10, preferably 1: 4, to the number of through holes drilled with the first laser. In order to obtain a good mixing of the through holes made with the two lasers, it is preferably provided that through bores which are produced with the aid of the first laser are arranged through bores which are produced with the aid of the second laser and / or that between through bores are formed by means of the through holes second laser produced through holes are arranged, which are produced by means of the first laser. As a result, a concentration of the through holes made with the first laser, which causes hydraulic markings, is avoided.

Preferably, the through holes made with the first laser have a larger diameter than the through holes made with the second laser.

It is very useful if cylindrical through holes with diameters between 80 and 100 μm are introduced into the substrate or the film by means of the CO2 laser and the remaining through holes are made with the aid of the UV laser. It is possible to produce the through holes to be introduced with the UV laser in any desired geometries, for example in the form of elongated holes, star-shaped, cross-shaped, rectangular and other conceivable embodiments, as well as in smaller cross-sectional areas than the cylindrical bores drilled with CO2 laser , The ratio between holes drilled with the first laser and with the second laser is controllable and dependent on the product being dewatered.

By combining the mentioned types of laser and the associated design options of the holes or the through holes extremely many holes per m ² can be incorporated into the sheet-like film. This can be achieved with relatively short drilling times. The said plurality of holes later leads to drainage technical advantages in the paper machine. In addition, the method can be configured expediently by first processing the substrate by means of the first laser for producing the larger through-holes and subsequently processing the substrate by means of the second laser to produce the smaller, in particular between the larger through-holes, through-holes.

Another expedient solution is that the through holes introduced with the second laser are not drilled in a cylindrically shaped manner, like the holes made with the first laser, but are inserted in such a way that seen in the thickness or depth direction of the substrate or the film, ie in the Inside the substrate or the film, there is a bottleneck of the through hole.

To form the constriction funnel-shaped holes are introduced into the substrate or the film. Each through-bore consists of two coaxial funnel-shaped bores, the first with its inlet opening on one side of the substrate or the film and a second bore with its outlet opening on the opposite side of the substrate. Both funnel-shaped holes meet at their end to each other and thus form the said bottleneck in the interior of the substrate. This means that from the inlet opening, the bore tapers to said constriction and the bore widens again from the constriction, which is meant by the above-mentioned term "funnel-shaped." In addition, the inlet and outlet openings each have a larger one Cross-sectional area as the bottleneck, as the name "bottleneck" suggests.

Up to bottleneck first finds a certain deceleration and from the bottleneck takes place in the flow direction an acceleration of the substrate or the film flowing through medium instead. Thus, as already stated, the effect of dewatering the fibrous web during its production in the paper machine is further improved. It is considered to be very advantageous that each constriction is incorporated at a distance to one side of the substrate or the film at a distance and this distance corresponds to approximately 1/3 of the thickness of the substrate or the film. The subsequently widening section is then logically 2/3 of the thickness of the substrate or the film.

The advantage of this is that the acceleration path is thus longer than the existing deceleration path. The extension of the through-hole to the machine side increases, the drainage performance. The extension to the fibrous web or paper side allows that can be sucked from a larger surface. As a result, fewer blockages of the pores occur.

The subsequent dewatering performance can also be further increased if the through-hole is made so that the outlet opening has a larger cross-sectional area than that of the inlet opening.

In the context of the method according to the invention, it is provided that the UV laser device is equipped with mirror scanners. This makes it possible to produce above all the manifold bore geometries described above.

The second laser used for drilling, in particular UV laser has a beam, which preferably has a diameter of only 50 μιτι or less. Furthermore, the UV laser can be tracked so that the mentioned various bore geometries can be produced. Optionally, several drilling operations are necessary for this.

In addition to the permeability, the elongation property of the substrate or of the film can also be controlled with the bores produced according to the invention.

If the slots are introduced in the longitudinal direction, the tensile strength increases compared to such substrates with only large round holes. Will the Slotted holes incorporated in the transverse direction increase the fiber support property.

It has been found that the greater overall total cross-sectional area of the through-holes or passage openings or boreholes, the lower the continuous smooth surface of the substrate or of the film in its property as a covering on which the fibrous web rests within the paper machine. Due to the overall lower coherent smooth surface, reduced adhesion forces occur, whereby the adhesion of the fibrous web, so the produced paper is reduced. The runability (running shanks) of the produced pulp or paper web within the paper machine is thereby improved.

The object of the invention is also achieved according to claim 16 with a covering for a paper machine. The covering is a film which is designed in the form of an endless belt with a useful area which can be brought into contact with a fibrous web, which has a multiplicity of through holes in the machine direction and in the transverse direction of the machine for dewatering a paper, board or tissue web ,

According to the invention, the useful area of the covering or film has a combination of through holes, of which one part has a larger diameter and / or different geometry than another part.

It is preferably provided that the through-holes are produced by a method which has been described above. To avoid repetition, it will not be discussed in detail here.

This clothing according to the invention is characterized by an optimal flow of the boreholes, whereby a high drainage performance is achieved becomes. In addition, in the fabric thus produced, adhesion of paper fibers in their use in the papermaking machine is minimized and the release of the formed web is facilitated. The invention will be explained in more detail by means of exemplary embodiments.

In a schematic greatly enlarged representation show:

FIG. 1 shows a plan view of part of the substrate or film drilled according to the invention with a first variant of the drill pattern,

FIG. 2 shows a plan view of part of the substrate or film drilled according to the invention with a second variant of the drill pattern, FIG. 3 shows a cross section through part of a substrate drilled in accordance with the invention in FIG.

In the figures, like parts are provided with the same reference numerals. Shown in Figure 1 is a sheet substrate 1, in the form of a band-like film consisting of a polymeric material in the form of plastic. The substrate or the film 1 (hereinafter referred to as film) extends in the machine direction MD and in the transverse direction QD. The film is to serve in the example as a forming fabric for dewatering a fibrous web in a papermaking machine. Therefore, a certain number of through-holes are introduced into the film by means of a CO2 laser, designated 2, and a certain number of through-holes, made with the aid of a UV laser and designated 3.

In the figure 1 a hole pattern is exemplified, which consists of large and small holes. The large holes or through holes 2 are with Help of a CO2 laser and the small through holes 3 made with the help of a UV laser.

With the UV laser one is able to create arbitrarily defined shapes and sizes of through holes. In FIG. 1, circular holes 3.1 can be seen, whereas in FIG. 2 rectangular holes 3.2 oriented in the transverse direction are shown. There are no limits to the variety of forms. It is also possible to choose other geometric shapes 3.n, for example star-shaped, cross-shaped, oval shapes etc. The individual geometric shapes can all combine with each other or in a specific selection combined to form a drill pattern.

Also their orientation within a row of holes or with respect to an adjacent row can be chosen arbitrarily. In the example chosen in FIGS. 1 and 2, the row spacings between two adjacent rows of holes in the transverse direction QR and in the machine direction MD are the same in each case. If desired, variations are also conceivable here.

FIG. 3 shows a section of a film drilled as in FIG. 1 in cross-section. In FIG. 1, the section line is indicated by A-A.

The film 1 has a thickness d.

In the thickness direction, the film 1 is provided with a plurality of different through-holes. In FIG. 3, only two adjacent bores (see section line A-A from FIG. 1) are shown for clarification.

These through holes are introduced both with the aid of a CO2 laser and with the aid of a UV laser. On the left is the UV hole 3 and to the right of it the CO2 hole 2. Both are circular through holes. The CO2 bore 2 has a maximum diameter of 100 μιτι, whereas the UV bore 3 has a significantly smaller diameter. It can be seen in FIG. 3 that a through hole 3 made with the UV laser thus consists of funnel-shaped or frustoconical bores 3a and 3b arranged one above the other. The through hole 3 is thus not continuously bored cylindrical.

Each through hole 3 thus consists of the first bore 3a with a located on the film side 1 a inlet opening 3c and a second bore 3b with a located on the opposite side of the film 1 b outlet opening 3d. Both openings 3c and 3d each have a larger cross-sectional area A3c (cross-sectional area of the inlet opening 3c) and A3d (cross-sectional area of the outlet opening 3d) than an existing constriction 3f of the through-hole 3 at which the two funnel-shaped bores 3a and 3b adjoin one another. On the film side 1 a is, as I said, the dewatered fibrous web F, which is indicated only by dashed lines, whereas the opposite other side of the film 1 b facing the machine side. The said constriction 3f has a nominal diameter of 25 μιτι and also has the film side 1 a at a distance a. The distance a, in which the upper, i. The first hole 3a is located and tapers to the constriction 3f, corresponds to about 1/3 of the thickness d of the film 1, so that the downwardly widening bore 3b extends over about 2/3 of the thickness d of the film 1 and is denoted by b.

It is also clear from the figure that the area A3d is larger than the upper area A3c. This produces a better flow-through effect from the inlet opening 3c to the outlet opening 3d.

It should be added that the number of through holes 3 bored with UV lasers is 1: 1 to 1:10, preferably 1: 4, relative to the number of through holes 2 drilled with CO2 lasers.

LIST OF REFERENCE NUMBERS

1 substrate or foil

1 a a film side

1 b other side of the film

2 CO ₂ - laser drilling

3 UV laser drilling

3a funnel-shaped bore

3b funnel-shaped bore

3c inlet

3d outlet

3f bottleneck

3.1 circular bore

3.2 rectangular bore

A3c cross-sectional area of the inlet opening

A3d cross-sectional area of the outlet opening a distance

b distance

d thickness

F fibrous web

MD machine direction

QD transverse direction

Claims

Patent claims

1 . Method for introducing through holes (2,3) with the aid of laser beams into a flat substrate, in particular into a strip-shaped film (1), which is intended for use as a covering or in a covering in a paper machine, the through holes (2, 3) are introduced in the thickness direction (d) of the substrate or film (1), characterized in that a certain number of through holes (2) are made with the aid of a first laser, in particular a CO2 laser, and a certain number of through holes ( 3) are produced with the aid of a second laser, in particular a UV laser, and the first laser operates at a longer working wavelength than the second laser.

2. The method according to claim 1, characterized in that arbitrarily defined shapes and sizes of through holes (3.1, 3.2, 3.n) are created and introduced in combination with one another into the substrate or the film (1).

3. The method according to any one of the preceding claims, characterized in that the covering has a useful area which can be brought into contact with a fibrous web when used as intended, the substrate in the area which provides the useful area with the first laser and with the second Laser treatment is carried out.

4. Method according to one of the preceding claims, characterized in that through-holes (3) are arranged between through-holes (2) which are produced with the aid of the first laser and/or in that between through-holes (3) which with the help of second laser through holes (2) are arranged, which are made with the help of the first laser.

Method according to one of the preceding claims, characterized in that the through holes (2) produced with the first laser have a larger diameter than the through holes (3) produced with the second laser.

Method according to one of the preceding claims, characterized in that cylindrical through-holes (2) with diameters between 80 and 100 μιτι are produced with the help of the first laser and the remaining through-holes (3, 3.1, 3.2, 3.n) with the help of the second laser are introduced into the substrate or the film (1), the through-holes (3, 3.1, 3.2, 3.n) made with the second laser having various geometric shapes and/or smaller cross-sectional areas than the cylindrical through-holes made with the first laser (2).

Method according to one of the preceding claims 5 or 6, characterized in that the substrate is first processed using the first laser to produce the larger through-holes and then the substrate is processed using the second laser to produce the smaller through-holes arranged between the larger through-holes.

Method according to one of the preceding claims, characterized in that the through holes (3, 3.1, 3.2, 3.n) made with the second laser are not cylindrical, but are made in such a way that in the thickness direction (d) of the substrate or film ( 1), that is, inside the substrate or film (1) there is a constriction (3f) of the through hole (3, 3.1, 3.2, 3.n).

9. The method according to claim 8, characterized in that to form the constriction (3f), coaxially opposite funnel-shaped bores (3a, 3b) are introduced into the substrate or the film (1), one bore (3a) being on the one side (1a) of the substrate or film (1) located inlet opening (3c) and the other hole (3b) an outlet opening (3d) located on the opposite side (1b) of the substrate or film (1). and wherein the inlet opening (3c) and the outlet opening (3d) each have a larger cross-sectional area (A3c, A3d) than the constriction (3f) of the through hole (3, 3.1, 3.2, 3.n).

10. The method according to claim 8 or 9, characterized in that each constriction (3f) to one web side (1a) of the substrate or the film (1) is incorporated at a distance (a), this distance (a) being approx .1/3 of the thickness (d) of the substrate or film (1).

1 1 . Method according to claims 8 to 10, characterized in that the through hole (3, 3.1, 3.2, 3.n) is produced such that the outlet opening (3d) has a larger cross-sectional area (A3d) than that of the inlet opening (A3c).

12. Method according to one of the preceding claims, characterized in that the second laser is equipped with mirror scanners.

13. The method according to any one of the preceding claims, characterized in that the second laser used for drilling has a beam with a diameter of νοηδθ μιτι or less.

14. The method according to any one of the preceding claims, characterized in that any geometric shapes and sizes of through holes (3, 3.1, 3.2, 3.n) are produced by tracking the second laser beam and / or by several drilling processes.

15. The method according to any one of the preceding claims, characterized in that the number of through holes that are drilled with the second laser compared to the number of through holes that are drilled with the first laser is in a ratio of 1:1 to 1:10, preferably 1:4 stand.

16. Covering for a paper machine, wherein the covering is a film (1) which is designed in the form of an endless belt, with a usable area which can be brought into contact with a fibrous web and which is in the machine direction (MD) and in the transverse direction (CD) of the machine Has a large number of through holes (2,3) for draining a paper, cardboard or tissue web, characterized in that the usable area of the covering or film (1) has a combination of through holes (2, 3, 3.1, 3.2, 3.n ), part of which has a larger diameter than another part.