EP3477002A1 - Rotary screen and method of manufacturing the same - Google Patents

Abstract

The invention relates to a method for producing a round screen (10) for a paper machine, in which a round screen body (12) which can be assembled statically in the paper machine is provided and coated with a production screen jacket (14) for the production of watermarked paper. According to the invention, it is provided that the production mesh jacket (14) is produced with a uniform lateral surface (32), raised and / or recessed watermark regions (16) and drainage perforations (26), wherein at least the lateral surface (32) of the production mesh jacket (14) additive manufacturing process as a layer sequence of a plurality of firmly interconnected material layers (28) is formed. The invention also relates to a correspondingly produced round screen.

Description

The invention relates to a method for producing a round screen for a paper machine, in which a round screen body which can be assembled statically in the paper machine is provided and coated with a production screen jacket for the production of watermarked paper. The invention also relates to a correspondingly produced round screen.

In papermaking on rotary screening machines, a round-screen cylinder with a clamped, rigid production screen jacket usually rotates in a trough with fiber suspension and draws paper. Within the Rundsiebzylinders a negative pressure is generated, which leads to a lowering of the liquid level in the interior of the cylinder. The fiber suspension therefore runs from the outside against the cylinder jacket and it store continuously fabric fibers on the production screen. The accumulated paper pulp is solidified so far that it can be removed as a moist paper web for further processing of the production screen.

Round screens for paper production with watermarks require a complex production. They consist of many, interconnected parts, which must be assembled with a large amount of manual labor. Such a production inherently carries a high potential for error. In addition, by assembling joints, welds and seams, which are usually visible later in the paper produced on the round screen.

Based on this, the present invention seeks to provide a round screen of the type mentioned, which avoids the disadvantages of the prior art and in particular is easier to manufacture and has advantageous properties in papermaking. The invention is intended also provide an advantageous manufacturing method for such a round screen.

This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

According to the invention, it is provided in a generic method that the production fabric sheath is produced with a uniform lateral surface, raised and / or recessed watermark regions and drainage perforations, wherein at least the lateral surface of the production sieve sheath is formed by an additive manufacturing process as a layer sequence of a plurality of firmly interconnected material layers.

In an advantageous embodiment, the jacket surface of the production screen jacket is first formed imperforate by the additive manufacturing process and then, preferably by laser perforation, drainage perforations are produced in the unperforated lateral surface of the production screen jacket.

In an alternative, likewise advantageous embodiment, it is provided that the jacket surface of the production screen jacket is formed together with the drainage perforations by the additive manufacturing method.

In a further advantageous embodiment, the jacket surface of the production screen jacket is formed together with the watermark areas by the additive manufacturing method.

• entweder die Mantelfläche des Produktionssiebmantels mit den Wasserzeichenbereichen entsprechenden Wasserzeichenaussparungen durch das additive Fertigungsverfahren erzeugt wird,
  oder die Mantelfläche des Produktionssiebmantels durch das additive Fertigungsverfahren ohne Wasserzeichenaussparungen erzeugt wird und die den Wasserzeichenbereichen entsprechenden Wasserzeichenaussparungen nachträglich, beispielsweise durch Laserschneiden, in die Mantelfläche eingebracht werden, und dann
• Wasserzeicheneinsätze in die Wasserzeichenaussparungen eingebracht werden, um die Wasserzeichenbereiche des Produktionssiebmantels zu bilden.

Alternatively and also with advantage, it is provided in the production that initially

• either the lateral surface of the production screen jacket with the watermark areas corresponding watermark recesses is produced by the additive manufacturing process,
  or the jacket surface of the production screen jacket is produced by the additive manufacturing method without watermark recesses and the watermark recesses corresponding to the watermark areas are subsequently introduced into the jacket surface, for example by laser cutting, and then
• Watermark inserts are inserted into the watermark recesses to form the watermark areas of the production screen.

In this production variant, the watermark inserts are preferably injected directly into the watermark recesses of the jacket surface in order to form injection-molded watermark regions in the production screen jacket. Alternatively, external watermark inserts can be arranged in the watermark recesses and connected in the edge region with the lateral surface.

The surface structure of the lateral surface outside the watermark regions advantageously forms a screen structure with one or more warp thread systems and one or more weft thread systems. Particularly preferably, the surface structure of the lateral surface forms a single-layer sieve structure.

In one development of the invention, the production screen jacket has two or more web areas, which are formed separately by the additive manufacturing method and subsequently assembled to form the production screen jacket.

The production screen jacket is advantageously formed from a wire-shaped, powdered or film-shaped starting material, a photosensitive paste or a liquid. Particularly advantageously, the production screen sheath is formed from a plastic. In particular, selective laser sintering, selective laser melting, electron beam melting, 3D printing with powder, melt stratification, laser deposition welding, multi-jet modeling, a PolyJet process, stereolithography, laminated object modeling, film transfer imaging or digital light processing are considered as additive manufacturing processes.

The invention also includes a round screen for a paper machine having a lathe screen body statically mountable in the paper machine and a production screen jacket for the production of watermarked paper. According to the invention, it is provided that the production mesh jacket has a uniform lateral surface, raised and / or recessed watermark regions and drainage perforations, and at least the jacket surface of the production mesh jacket is formed from a layer sequence of a plurality of material layers firmly bonded together in an additive manufacturing process.

The watermark regions are preferably formed integrally with the jacket surface of the production screen jacket from a layer sequence of a plurality of material layers firmly connected to one another in the additive manufacturing method.

Furthermore, the jacket surface of the production screen jacket is advantageously formed, together with the drainage perforations contained therein, from a layer sequence of a plurality of material layers firmly connected to one another in the additive manufacturing method.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

Fig. 1

in schematischer Ansicht ein Rundsieb für eine Papiermaschine für die Herstellung von Sicherheitspapier,

Fig. 2

einen Ausschnitt des Produktionssiebmantels in der Umgebung eines Wasserzeichenbereichs im Querschnitt entlang der Linie II-II von Fig. 1,

Fig. 3

in (a) und (b) Zwischenschritte bei der Herstellung eines Produktionssiebmantels nach einem anderen Ausführungsbeispiel der Erfindung,

Fig. 4

in (a) und (b) Zwischenschritte bei der Herstellung eines Produktionssiebmantels nach einem weiteren Ausführungsbeispiel der Erfindung, und

Fig. 5

mehrere rohrförmige Teilstücke, die jeweils separat durch ein additives Fertigungsverfahren hergestellt und dann zu einem gewünschten Produktionssiebmantel zusammengesetzt werden.

Show it:

Fig. 1

in a schematic view a round screen for a paper machine for the production of security paper,

Fig. 2

a section of the production screen jacket in the vicinity of a watermark area in cross section along the line II-II of Fig. 1 .

Fig. 3

in (a) and (b) intermediate steps in the production of a production screen jacket according to another embodiment of the invention,

Fig. 4

in (a) and (b) intermediate steps in the manufacture of a production screen jacket according to a further embodiment of the invention, and

Fig. 5

a plurality of tubular sections, each made separately by an additive manufacturing process and then assembled into a desired production screen shell.

FIG. 1 shows a schematic view of a round screen 10 for a paper machine for the production of security paper. The round screen 10 includes an inner round screen body 12 which is statically mountable in a paper machine. The round screen body 12 is coated with an exchangeable production screen 14, which is designed according to the invention for the production of security paper with watermarks

For this purpose, the production screen casing 14 has a multiplicity of raised and / or recessed watermark regions 16 in a lateral surface 32 with an otherwise uniform surface. In the watermark regions 16 paper pulp accumulates locally in paper production with a greater or smaller paper thickness than in the surrounding vellum region and therefore produces darker or lighter areas in the finished paper web. As a rule, a production screen jacket 14 contains a plurality of web regions 18 for parallel production of a plurality of individual uses on the formed paper web.

FIG. 2 shows a section 20 of the production screen 14 in the vicinity of a watermark area 16 in cross section along the line II-II of Fig. 1 , The watermark area 16 has a high-resolution multi-level relief 22 which, in addition, can have very sharp edges at approximately right angles in partial areas 24. Because of the multi-level relief 22, the watermark regions 16 are suitable on the one hand for generating watermark characters with soft, continuous brightness transitions, can create with subregions 24 but at the same time sharply demarcated, fine details with high contrast.

In order to ensure dewatering in papermaking, the outer surface 32 of the production screen 14 is provided with a plurality of dewatering perforations 26, the diameter of which is so small that fibers do not adhere to them during papermaking. Typical perforation diameters are between 50 μm and several 100 μm, for example about 500 μm.

As a special feature, the entire production screen casing 14 including the watermark regions 16 and the drainage perforations 26 contained in the lateral surface 32 are formed by an additive manufacturing process as a layer sequence of a plurality of firmly bonded material layers 28, as shown in detail section 34 of FIG Fig. 2 illustrated.

In particular, selective laser sintering, selective laser melting, electron beam melting, 3D printing with powder, melt stratification, laser deposition welding, multi-jet modeling, a polyjet process, stereolithography, laminated object modeling, film transfer imaging or digital light processing are considered as additive manufacturing processes , Depending on the manufacturing process, the starting material may be in the form of wire, powder, foil, paste or liquid. Particularly advantageous production screen 14 is formed by a plastic.

For this purpose, for example, the method of Selective Laser Melting (SLM) can be used. In this method, the powdery plastic building material is completely melted and hardened by a cooling process. The production screen 14 is thereby successively Lowering a building platform layer by layer with the desired structure along the longitudinal axis 30 of the screen shell constructed. This can be done, for example, with the aid of a 3D printhead, which in a continuous process layer by layer, the material layers 28 of the production screen 14 as a stationary tube ( Fig. 1 ). As a building platform, a rotary table with a vertical axis of rotation serve as a work surface on which the print head deposits the material layers 28 revolution for rotation during rotation of the rotary table.

As a result of the production by means of an additive manufacturing method, the production screen jacket 14 can be produced with watermark regions 16 integrated seamlessly into the jacket surface 32. The watermark regions 16 can be produced in particular as high-resolution multilevel watermark regions with reliefs having sharp edges of a marginal width of 0.4 mm or less. The sharply bordered elevations or depressions in the watermark areas in turn produce watermarks with sharply edged bright or dark motif structures in paper production. The watermark areas may have a high average spatial frequency of 2-3 Lp / mm or more, which allows the representation of finest image details and high image sharpness in the watermark regardless of the actual image content.

At the same time, the manufacture of the production screen 14 by the additive manufacturing process is greatly simplified and avoids sources of error by the costly assembly of many interconnected items required in conventional methods. The integral production completely eliminates seams, joints and welds that are often visible in the paper when using conventional round screens. The paper surface can therefore be optimally utilized. Finally, the production screen is 14 also mechanically very resistant due to its integral structure.

The surface structure of the lateral surface 32 of the production screen jacket 14 can be selected largely freely outside the watermark regions 16 by the use of additive manufacturing methods. For example, the surface structure of the lateral surface 32 can simulate a conventional screen structure with one or more Kettfadensytemen and one or more weft systems. Particularly advantageous is a single-layer sieve layer is modeled.

FIG. 3 FIG. 12 illustrates an alternative design of a production screen jacket 40 initially formed with watermark recesses 42 and drainage perforations 26 by an additive manufacturing process as a layer sequence of a plurality of firmly bonded material layers 28, as in FIG Fig. 3 (a) shown. In a further step, watermark inserts 44 in the region of the watermark recesses 42 are injected directly into the jacket surface 32 of the production screen jacket 40 and the production screen jacket 40 is thereby provided with injection-molded watermark inserts 44, as in FIG Fig. 3 (b) shown. In this way, watermark inserts 44 with a particularly high spatial resolution or with special material properties can be introduced into the production screen casing 40. In order to ensure drainage in the watermark areas 16, the watermark inserts 44 are also provided with drainage perforations 26.

Instead of injecting the watermark inserts 44 directly into the recesses 42, external watermark inserts may also be inserted into watermark recesses 42, for example, glued. Continue For example, the lateral surface 32 of the production screen jacket 40 may also initially be produced without watermark recesses 42 and then subsequently introduced, for example by laser cutting.

In the further embodiment of the Fig. 4 For example, the production screen jacket 50, including the watermark areas 16, but initially without drainage perforations, is formed by an additive manufacturing process as a layer sequence of a plurality of firmly bonded material layers 28, as in FIG Fig. 4 (a) shown. Subsequently, the production screen jacket 50 is exposed to laser radiation 52 in order to generate by laser perforation drainage perforations 26 in the lateral surface 32, as in the intermediate step of Fig. 4 (b) shown. The separate laser perforation can possibly achieve a speed advantage in the production of the production screen 50.

It is also possible the embodiments of Figures 3 and 4 to combine and first to form a production screen coat with watermark recesses and initially without drainage perforations by an additive manufacturing process as a layer sequence of a plurality of firmly interconnected material layers, and to subsequently produce the drainage perforations by laser perforation of the jacket surface of the production screen. The watermark areas may be generated, for example, by directly injecting watermark inserts or by introducing external watermark inserts, as associated with Fig. 3 already described.

Another way of speeding up the production of a production screen jacket is to separate the production screen jacket 60 into a plurality of tubular sections 62, 64, 66 separately by an additive manufacturing process to produce, as in Fig. 5 shown schematically. The tubular sections 62, 64, 66 may for example be printed in parallel by means of 3D printing and in particular the in Fig. 1 shown web areas 18 correspond to a production screen 14. After being manufactured separately, the tubular sections 62, 64, 66 are assembled into the desired production screen jacket 60.

LIST OF REFERENCE NUMBERS

10

Round Screen

12

Rundsiebkörper

14

Produktionssiebmantel

16

Watermark areas

18

track regions

20

neckline

22

high-resolution multi-level relief

24

subregions

26

Entwässerungsperforationen

28

material layers

30

longitudinal axis

32

lateral surface

34

callout

40

Produktionssiebmantel

42

Watermark recesses

44

Watermark inserts

50

Produktionssiebmantel

52

laser radiation

60

Produktionssiebmantel

62, 64, 66

sections

Claims (15)

Method for producing a round screen for a paper machine, in which a round screen body which can be assembled statically in the paper machine is provided and coated with a production screen jacket for the production of watermarked paper, characterized in that the production screen jacket has a uniform lateral surface, raised and / or recessed watermark areas and drainage perforations is produced, wherein at least the lateral surface of the production screen jacket is formed by an additive manufacturing process as a layer sequence of a plurality of firmly interconnected material layers. A method according to claim 1, characterized in that the lateral surface of the production screen shell is initially formed by the additive manufacturing process unperforated, and then, preferably by laser perforation, drainage perforations in the unperforated lateral surface of the production screen shell are generated. A method according to claim 1, characterized in that the lateral surface of the production screen shell is formed together with the dewatering perforations by the additive manufacturing process. Method according to at least one of claims 1 to 3, characterized in that the jacket surface of the production screen jacket is formed together with the watermark areas by the additive manufacturing method. Method according to at least one of claims 1 to 3, characterized in that either the lateral surface of the production screen with the watermark areas corresponding watermark recesses is generated by the additive manufacturing process, or the lateral surface of the production screen is produced by the additive manufacturing process without watermark recesses and the watermark areas corresponding watermark recesses are subsequently introduced, for example by laser cutting in the lateral surface, and - Watermark inserts are inserted into the watermark recesses to form the watermark areas of the production screen jacket. A method according to claim 5, characterized in that the watermark inserts are injected directly into the watermark recesses of the lateral surface to form injection-molded watermark regions in the production screen coat. A method according to claim 5, characterized in that external watermark inserts are arranged in the watermark recesses and connected in the edge region with the lateral surface. Method according to at least one of claims 1 to 7, characterized in that the surface structure of the lateral surface outside the watermark areas simulates a screen structure with one or more Kettfadensytemen and one or more weft thread systems. Method according to at least one of claims 1 to 8, characterized in that the production screen jacket has two or more web portions which are formed separately by the additive manufacturing method and subsequently assembled into the production screen jacket. Method according to at least one of Claims 1 to 9, characterized in that the production screen jacket is formed from a wire-shaped, powdery or film-shaped starting material, from a photosensitive paste or a liquid. Method according to at least one of claims 1 to 10, characterized in that the production screen jacket is formed from a plastic. Method according to at least one of claims 1 to 11, characterized in that as additive manufacturing methods Selective laser sintering, Selective laser melting, Electron beam melting, 3D printing with powder, melt stratification, laser deposition welding, multi-jet modeling, a Polyjet method, stereolithography, Laminated Object Modeling, Film Transfer Imaging or Digital Light Processing A round screen for a paper machine with a round screen body that can be statically mounted in the paper machine and a production screen jacket for the production of paper with watermark, characterized in that the production screen jacket has a uniform lateral surface, raised and / or recessed watermark areas and drainage perforations and at least the lateral surface of the production screen jacket a layer sequence of a plurality of material layers firmly connected to each other in an additive manufacturing process is formed. A round screen according to claim 13, characterized in that the watermark areas are formed integrally with the jacket surface of the production screen jacket from a layer sequence of a plurality of material layers firmly connected to one another in the additive manufacturing method. A round screen according to claim 13 or 14, characterized in that the jacket surface of the production screen jacket, together with the drainage perforations contained therein, is formed from a layer sequence of a plurality of material layers firmly joined together in the additive manufacturing method.

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