WO2021063556A1

WO2021063556A1 - Lamella for a headbox, and method for producing a lamella

Info

Publication number: WO2021063556A1
Application number: PCT/EP2020/069835
Authority: WO
Inventors: Wolfgang Ruf; Helga KRIEGER
Original assignee: Voith Patent Gmbh
Priority date: 2019-09-30
Filing date: 2020-07-14
Publication date: 2021-04-08
Also published as: CN114555882B; CN114555882A; DE102019126296A1; EP4038234A1

Abstract

The invention relates to a lamella (1) which is suitable for installing into a nozzle (17) of a headbox (16) of a paper machine for separating two suspension flows flowing through the nozzle (17), comprising a lamella body (3) which has a lamella body width, a lamella body length (4), and a lamella body thickness (5) and which has a downstream end (8). The lamella body length (4) and the lamella body width define a first flow surface (6) and a second flow surface (7) opposite the first flow surface (6), and a film (13) which protrudes beyond the downstream end (8) of the lamella body (3) is fixed to the downstream end (8) on the first flow surface (6) or on the second flow surface (6). The lamella (1) according to the invention is characterized in that the film (13) protrudes beyond the downstream end (8) of the lamella body (3) by a projection (14) which is greater than 0.5 mm, in particular greater than 1 mm, preferably greater than 1.5 mm, more preferably greater than 2 mm.

Description

Lamella for a headbox and method for making one

Lamella

The invention relates to a lamella which is suitable for installation in a nozzle of a headbox of a paper machine for separating two suspension streams flowing through the nozzle, with a lamella body which has a lamella body width, a lamella body length and a lamella body thickness and a downstream end, and the lamella body length and the lamellar body width spans a first flow surface and a second flow surface opposite the first flow surface and a film projecting beyond the downstream end of the lamellar body is attached at the downstream end on the first flow surface or on the second flow surface.

Devices of this type are known. The document DE4329810 A1 discloses a lamella of a headbox of a paper machine with an end area. To avoid or reduce periodic vortex shedding, various embodiments of the end region of the lamella are proposed. In one example, the end of the lamella is provided with a film which protrudes beyond the end of the lamella. The film is attached to the top or bottom of the lamella.

With the known solutions, the effects of the vortex shedding on the quality of the paper web produced can only be reduced in a certain operating window, for example a small speed range. In addition, the structure of the lamella is not satisfactory in terms of cost and function.

The object of the invention is therefore to improve the structure and function of a lamella of a headbox of a paper machine, as well as to specify a method for producing a lamella and to propose a headbox for a good jet quality with at least one lamella. The object is achieved by the features of claim 1. A lamella is proposed which is suitable for installation in a nozzle of a headbox of a paper machine for separating two suspension streams flowing through the nozzle. The lamella comprises a lamella body which has a lamella body width, a lamella body length and a lamella body thickness and a downstream end, and the lamella body length and the lamella body width span a first flow surface and a second flow surface opposite the first flow surface and at the downstream end on the first flow surface or on the second flow surface a protruding over the downstream end of the lamellar film is attached. The invention is characterized in that the film protrudes by an overhang over the downstream end of the lamellar body and the overhang is greater than 0.5 mm, in particular greater than 1 mm, preferably greater than 1.5, very particularly preferably greater than 2 mm .

The lamellar body length extends in the direction of the flowing suspension streams and the lamellar body width extends transversely thereto.

The film preferably extends over the entire width of the lamella body.

The solution according to the invention has the advantage that the vortices shedding at the downstream end of the lamellar body do not have an effect beyond the film area. As a result, on the one hand, a good paper quality can be achieved without disturbances caused by hydraulics and, on the other hand, in the case of a multi-layer headbox, a good layer separation of the different layers can be achieved.

It is also advantageous if the film protrudes by a protrusion beyond the downstream end of the lamellar body and the protrusion is smaller than 50 mm, in particular smaller than 30 mm, preferably smaller than 20, very particularly preferably smaller than 10 mm. If the overhang is chosen to be larger, there is a risk that, under certain operating conditions, the film itself will cause disturbances in the flow and flutters. In addition, the mechanical stress on the connection between the film and the lamellar body increases. This can lead to loosening of the connection.

The lamellar body thickness is preferably in the range from 3 mm to 6 mm, preferably in the range from 3.5 mm to 4.5 mm.

The lamellar body thickness can be reduced at the downstream end by a bevel on the first flow surface and / or on the second flow surface to a final thickness between 0.2 mm and 2 mm, in particular between 0.5 mm and 1 mm. The first flow surface and the second flow surface thereby form a point at the downstream end of the lamellar body with a point angle. This reduces the formation of eddies and increases the operating window.

It is particularly advantageous if the bevel has a first bevel angle to the first flow surface and / or a second bevel angle to the second flow surface. The point angle has values in the range from 1 ° to 9 °, in particular in the range from 1.5 ° to 6 °, preferably in the range from 2 ° to 5 °. With a bevel on one side, the bevel angle corresponds to the tip angle of the lamellar body.

In the case of a double-sided bevel, the sum of the two bevel angles corresponds to the tip angle of the lamellar body. The lamellar body is preferably beveled symmetrically, so that the first bevel angle is equal to the second bevel angle. Here, too, the point angle has values in the range from 1 ° to 9 °, in particular in the range from 1.5 ° to 6 °, preferably in the range from 2 ° to 5 °.

The film can be attached over the entire length of the lamellar body or only on part of the length of the lamellar body. If the film is only connected to the lamellar body in the area of the downstream end, the film can be arranged sunk in the corresponding flow surface.

The foil is preferably connected to the lamellar body by gluing or welding.

It is particularly advantageous if the film has a film thickness between 0.05 mm and 0.3 mm, in particular between 0.1 mm and 0.2 mm.

Furthermore, it is possible for the lamella to be designed in such a way that the film material differs from the lamella body material or that the film material differs in terms of mechanical properties from the lamella body material as a result of mechanical or thermal treatment. As a result, the components, such as the lamella body and the film of the lamella, can be optimized in terms of construction according to the specific requirements and with regard to costs. The lamellar body must have a minimum rigidity in order to maintain the geometry of the flow channels in the nozzle. The film, on the other hand, has to be just so soft that no eddies are induced in the flow and the eddies that arise at the end of the lamella body are dampened.

In the event that the lamellar body material and the foil material are the same, the foil material can be treated mechanically by monoaxial or biaxial stretching, for example in the direction of the lamellar body length or additionally in the direction of the lamellar body width, before being connected to the lamellar body. Optionally, heat can also be used. By stretching, the flexural rigidity can be optimized with otherwise unchanged geometry parameters.

The lamellar body material can be selected from the following group of materials: plastic, CFRP (carbon fiber reinforced plastic), PPSU (polyphenyl sulfone), PC (polycarbonate), PET (polyethylene terephthalate), PE (polyethylene), metal. CFRP as a material is particularly advantageous in terms of dimensional stability, thermal and chemical properties and weight and due to the structural options in terms of structure.

The film material can be selected from the following group of materials: plastic, PET (polyethylene terephthalate), PC (polycarbonate), PE (polyethylene), metal.

The material PET is particularly suitable for monoaxial or biaxial stretching to optimize flexural rigidity.

The object is also achieved by a headbox with a turbulence generator and a nozzle, at least one lamella according to the invention being used in the nozzle.

The nozzle of the headbox has a nozzle length. The lamella length of the at least one lamella can be shorter or longer than the nozzle length. This means that the lamella can on the one hand end inside the nozzle and on the other hand can end outside the nozzle.

If several lamellas are used in a headbox nozzle, part of the lamellae can end inside and the remaining part outside the nozzle.

The length of the lamellas can be different.

The lamella can be used in a single-layer headbox operated with just one fiber suspension. However, it is also possible to use the lamella in a multi-layer headbox that is fed with at least two different pulp suspensions. The at least two different fiber suspensions are kept separate by the lamella in order to produce a multi-layer fiber web in the subsequent forming section. The object is also achieved by a method for producing a lamella for installation in a nozzle of a headbox of a paper machine for separating two suspension streams flowing through the nozzle. The lamella comprises a lamella body which has a lamella body width, a lamella body length and a lamella body thickness and a downstream end, and the lamella body length and the lamella body width span a first flow surface and a second flow surface opposite the first flow surface and at the downstream end on the first flow surface or on the second flow surface, a film projecting beyond the downstream end of the lamellar body is attached. According to the invention it is provided that the film protrudes by an overhang over the downstream end of the lamellar body and the overhang is selected to be greater than 0.5 mm, in particular greater than 1 mm, preferably greater than 1.5, very particularly preferably greater than 2 mm.

It is also advantageous if the film material comprises a plastic that is stretched monoaxially, preferably in the direction of the protrusion, or biaxially.

Further features and advantages of the invention emerge from the following description of preferred exemplary embodiments with reference to the drawings.

Show it

Figure 1 shows a first embodiment of a lamella according to the invention in a schematic and simplified representation;

FIG. 2 shows a second embodiment of a lamella according to the invention in a schematic and simplified representation;

Figure 3 shows a third embodiment of an inventive

Lamella in a schematic and simplified representation; Figure 4 shows a fourth embodiment of an inventive

Lamella in a schematic and simplified representation;

FIG. 5 shows an embodiment of a headbox with lamellae according to the invention in a schematic and simplified representation;

In the figures 1 to 4 different embodiments of a lamella 1 according to the invention are shown in a schematic and simplified representation. In these examples, the lamellae 1 are shown greatly shortened in their length relative to the thickness in order to be able to better recognize the details. The lamella 1 according to the invention is intended for installation in a nozzle 17 of a headbox 16 of a paper machine. It is used there to separate two suspension streams flowing through the nozzle 17, as shown in FIG. The lamella 1 can be used in a single-layer headbox that is operated with only one fiber suspension. However, it is also possible to use the lamella 1 in a multi-layer headbox which is fed with at least two different pulp suspensions. The at least two different fiber suspensions are kept separate by the lamella 1 in order to produce a multi-layer fiber web in the subsequent forming section.

The lamella 1 according to FIG. 1 comprises a lamella body 3, which has a lamella body width, a lamella body length 4 and a lamella body thickness 5 and a downstream end 8. The lamellar body length 4 and the lamellar body width, which is directed into the plane of the drawing and perpendicular to the lamellar body length 4, span a first flow surface 6 and a second flow surface 7 opposite the first flow surface 6. At the downstream end 8, a film 13 projecting beyond the downstream end 8 of the lamellar body 3 is fastened on the first flow surface 6 or on the second flow surface 7. The film material is plastic, preferably PET, and in this example differs from the lamellar body material, which is designed as CFRP. Before being connected to the lamellar body 3, the film is stretched biaxially or monoaxially, preferably in the direction of the protrusion 14. As a result, the mechanical properties of the film 13 are optimized, that is to say changed with regard to the function of avoiding or damping flow vortices. A required flexural rigidity can be achieved with a small film thickness. The film 13 protrudes by an overhang 14 beyond the downstream end 8 of the lamellar body 3 and the overhang 14 is greater than 0.5 mm, in particular greater than 1 mm, preferably greater than 1.5, very particularly greater than 2 mm. The protrusion 14 of the film 13 is preferably smaller than 50 mm, in particular smaller than 30 mm, preferably smaller than 20 mm, very particularly preferably smaller than 10 mm. The lamellar body thickness 5 is in the range from 3mm to 6mm, preferably in the range from 3.5mm to 4.5mm. The lamellar body thickness 5 is reduced in Figure 1 at the downstream end 8 by a bevel on the first flow surface 6 to a final thickness 9 between 0.2 mm and 2 mm, in particular between 0.5 mm and 1 mm. The first flow surface 6 and the second flow surface 7 form a point at the downstream end 8 of the lamellar body 3 with a point angle 2. The bevel in the embodiment of FIG. 1 has a first bevel angle 10 to the first flow surface 6 in the range from 1 ° to 9 °, in particular in the range from 1.5 ° to 6 °, preferably in the range from 2 ° to 5 °. The value of the bevel angle 10 corresponds to the point angle 12. The film 13 is only attached to part of the lamellar body length 4, in this example by gluing, and rests on the second flow surface 7. The film 13 has a film thickness 15 between 0.05 mm and 0.3 mm, in particular between 0.1 mm and 0.2 mm.

The second embodiment of a lamella 1 according to the invention according to FIG. 2 differs from the embodiment according to FIG. 1 only in that the film 13 is arranged sunk in the second flow surface 7. The advantage of this embodiment is that the film 13 does not form an abutting edge. In the third embodiment of a lamella 1 according to the invention in FIG. 3, the film 13 is placed on the bevel of the first flow surface 6 and fastened by gluing.

FIG. 4 shows a further embodiment of the lamella 1 in which the bevel was carried out on both sides of the lamella 1. With this two-sided bevel, the sum of the two bevel angles 10, 11 corresponds to the tip angle 12 of the lamellar body. In this example too, the values of the tip angle 12 are in the range from 1 ° to 9 °, in particular in the range from 1.5 ° to 6 °, preferably in the range from 2 ° to 5 °. The lamellar body 3 is preferably beveled symmetrically so that the first bevel angle 10 is equal to the second bevel angle 11. The film 13 is placed on the bevel of the first flow surface 6 and fastened by gluing.

FIG. 5 shows an embodiment of a headbox 16 with two lamellae 1 according to the invention in a schematic and simplified representation. The headbox 16 comprises a turbulence generator 19 and a nozzle 17. This headbox 16 is suitable as a multi-layer headbox or as a single-layer headbox. The fiber suspension flows through the turbulence generator 19 comprising a tube bundle and then flows in the flow direction 20 through the nozzle. In the case of a single-layer headbox, on the one hand, the lamellae 1 reduce coarse eddies in the flow of the pulp suspension and, on the other hand, they avoid the formation of eddies at the end of the lamellae 1. In the case of a multi-layer headbox, the lamellae 1 keep the different pulp suspensions separate and lead the different fiber suspension layers on End of the lamellae 1 gently, that is, without vortex formation, together, so that a layer separation is maintained even after the lamellae end. The first flow surfaces 6 of the lamellae 1 are formed by the upper side of the lamellae 1 and correspondingly the second flow areas 7 are formed by the lower side of the lamellae 1. The first flow surfaces 6 of the lamellae 1 can also be formed by the underside of the lamellae 1 and correspondingly the second flow surfaces 7 can be formed through the upper side the lamellae 1 be formed. It is also possible that the first flow surface 6 of the upper lamella 1 is formed by the underside of the lamella 1 and the first flow surface 6 of the lower lamella 1 is formed by the upper side of the lower lamella 1. The orientation of the position of the lamellae in the nozzle 17 can therefore be freely selected. In this example, the lamella lengths 2 are shorter than the nozzle length 18. They therefore end inside the nozzle.

Corresponding elements of the exemplary embodiments in the figures are provided with the same reference symbols. The functions of such elements in the individual figures correspond to one another, unless otherwise described and it does not lead to contradictions. A repeated description is therefore dispensed with. It is also pointed out that the distinguishing features of the exemplary embodiments shown can be exchanged for one another and combined with one another. The invention is therefore not limited to the combinations of features shown in the exemplary embodiments shown.

List of reference symbols

Lamella lamella length lamella body lamella body length lamella body thickness first flow area second flow area downstream end final thickness first bevel angle second bevel angle point angle foil

Got over

Film thickness

Headbox

jet

Nozzle length

Turbulence generator

Direction of flow

Claims

Slat for a headbox and method of making a slat

1. Lamella (1) suitable for installation in a nozzle (17) of a headbox (16) of a paper machine for separating two suspension streams flowing through the nozzle (17), with a lamella body (3) which is one lamella body width, one lamella body length (4) and has a lamellar body thickness (5) and a downstream end (8), and the lamellar body length (4) and the lamellar body width span a first flow surface (6) and a second flow surface (7) opposite the first flow surface (6) and at the downstream end ( 8) on the first flow surface (6) or on the second flow surface (7) a film (13) protruding beyond the downstream end (8) of the lamellar body (3) is attached, characterized in that the film (13) protrudes around a protrusion (14) protrudes beyond the downstream end (8) of the lamellar body (3) and the protrusion (14) is greater than 0.5 mm, in particular greater than 1 mm, preferably greater than 1.5, very particularly preferably greater he is than 2mm.

2. Lamella according to one of the preceding claims, characterized in that the film (13) protrudes by a protrusion (14) beyond the downstream end (8) of the lamella body (3) and the protrusion (14) is smaller than 50 mm, in particular smaller than 30 mm, preferably smaller than 20 mm, very particularly preferably smaller than 10 mm.

3. Slat according to one of the preceding claims, characterized in that the slat body thickness (5) in the range of 3mm to 6mm, is preferably in the range from 3.5mm to 4.5mm.

4. Lamella according to one of the preceding claims, characterized in that the lamella body thickness (5) at the downstream end (8) by a bevel on the first flow surface (6) and / or on the second flow surface (7) to a final thickness (9) between 0.2mm and 2mm, in particular between 0.5mm and 1mm, and the first flow surface and the second flow surface form a point at the downstream end (8) of the lamellar body (3) with a point angle (12).

5. Lamella according to claim 4, characterized in that the tip angle (12) has values in the range from 1 ° to 9 °, in particular in the range from 1.5 ° to 6 °, preferably in the range from 2 ° to 5 °.

6. Lamella according to one of the preceding claims, characterized in that the film (13) is attached to the entire length of the lamella body (4) or is attached to only part of the length of the lamella body (4).

7. Slat according to one of the preceding claims, characterized in that the film (13) is arranged sunk in the corresponding flow surface (6, 7).

8. Slat according to one of the preceding claims, characterized in that the film (13) has a film thickness (15) between 0.05 mm and 0.3 mm, in particular between 0.1 mm and 0.2 mm.

9. Slat according to one of the preceding claims, characterized in that the film material differs from the slat body material and / or that the film material has mechanical properties as a result of mechanical or thermal treatment differs from the lamellar body material.

10. Slat according to one of the preceding claims, characterized in that the slat body material is selected from the following group of materials: plastic, CFRP (carbon fiber reinforced plastic), PPSU (polyphenylsulfone), PC (polycarbonate), PET (polyethylene terephthalate), PE (polyethylene) , Metal.

11. Slat according to one of the preceding claims, characterized in that the film material is selected from the following group of materials: plastic, PET (polyethylene terephthalate), PC (polycarbonate), PPSU (polyphenyl sulfone), PE (polyethylene), metal.

12. Headbox (16) of a paper machine with a turbulence generator (19) and a nozzle (17), characterized in that at least one lamella (1) according to one of the preceding claims for the separation of through the nozzle (17) in the nozzle (17) ) flowing suspension streams is used.

13. Headbox according to claim 12, characterized in that the nozzle (17) has a nozzle length (18) and the lamella length (2) is shorter or longer than the nozzle length (18).

14. A method for producing a lamella (1) for installation in a nozzle (17) of a headbox (16) of a paper machine for separating two suspension streams flowing through the nozzle, with a lamellar body having a lamellar body width, a lamellar body length (4) and a lamellar body thickness (5) and a downstream end (8), and the lamellar body length (4) and the lamellar body width span a first flow surface (6) and a second flow surface (7) opposite the first flow surface (6) and at the downstream end (8) a film (13) projecting beyond the downstream end (8) of the lamellar body (3) is attached to the first flow surface (6) or on the second flow surface (7), characterized in that the film (13) protrudes by an overhang (14) over the downstream end (8) of the lamellar body (3) and the overhang (14) is greater than 0.5 mm, in particular greater than 1 mm, preferably greater than 1.5, very particularly preferably greater than

2mm is chosen.

15. The device according to claim 14, characterized in that the film material comprises a plastic which is stretched biaxially or monoaxially, preferably in the direction of the protrusion (14).