EP1811081A2 - Headbox of a machine for manufacturing a fibrous web - Google Patents

Abstract

A paper mill has a headbox dispensing a flat flow of fiber suspension via duct incorporating vortex generators in channels that then merge into a single wide transport and drainage conveyer. Each channel has a series of polygonal vortex generators located immediately prior to the channel outlet.

Description

The invention relates to a headbox of a machine for producing a fibrous web, in particular paper or board web, from at least one pulp suspension, with at least one feed device feeding the at least one pulp suspension and at least one turbulence generating means in which the at least one pulp suspension by a Variety of one inlet side and one outlet side having flow channels flows, thereby divided into turbulent pulp suspension partial flows and is merged after exiting the turbulence generating means in a preferably machine-width chamber, wherein the respective outlet side has a flat, formed by the end of the respective flow channel outlet surface.

Such a headbox is for example from the German Offenlegungsschrift DE 31 42 292 A1 known. The flow channels of the turbulence generating means have either circular or polygonal cross-sectional areas. The polygonal cross-sectional areas may assume a rectangular, in particular a square, or a hexagonal shape. All of the forms presented here have at least one same property: they have vertical webs or portions of vertical walls. It has now been shown in practice that this property generates a lattice tracking flow in the at least one pulp suspension, which has a negative effect on the properties of the fibrous web to be produced. In addition, the aforementioned causes Property also demixing effects in the at least one pulp suspension. The demixing effects occur here in particular in a Unterlastsituation in the headbox in appearance.

It is therefore an object of the invention to improve a headbox of the type mentioned in such a way that the said disadvantages of the prior art as far as possible, preferably completely avoided and thus a homogeneous flow as possible immediately downstream of the turbulence generating means is generated. In particular, the lattice tracking flow and any segregation effects should be kept to a minimum.

This object is achieved in that the outlet surfaces of the flow channels are each formed of a polygon sides having a plurality of polygon having at least two inner angle, which are smaller than 90 °, in particular less than 75 °, and that all polygon sides of the respective polygon of the Perpendicular to the turbulence generating means are aligned differently. The vertical of the turbulence generating means is aligned by definition orthogonal to the cross machine direction (CD direction); it thus corresponds to the so-called z-axis when viewed locally in or against the machine direction (MD direction). The deviating orientation indicates a non-parallel orientation of the polygon sides to the perpendicular of the turbulence generating means.

The object of the invention is completely solved in this way.

By this measure according to the invention, in particular by the requirement of at least two internal angles which are smaller than 90 °, in particular smaller than 75 °, and the property that all polygon sides of the respective polygon are oriented differently from the vertical of the turbulence generating means, both vertical webs as well as shares in vertical Walls in the region of the turbulence generating means completely avoided. In addition, the land areas located between the outlet surfaces are significantly reduced compared to the prior art. As a result, the previous problems with lattice tracking flow and possible segregation effects are noticeably reduced.

In a first preferred embodiment, at least some of the polygons are formed of triangles, preferably of equilateral triangles. In this case, one side of the triangle is aligned along the baseline, ie transversely to the flow direction of the at least one pulp suspension. The triangles have the not negligible advantage that the land areas are reduced to a minimum. Of course, all flow channels may have triangular outlet surfaces.

The headbox may also have flow channels arranged in several rows. In this case, the flow channels of at least two adjacent rows can be arranged mirror-inverted or rectified to one another. In addition, they can also be offset, preferably arranged in half offset from one another. Thus, an optimal arrangement possibility can be selected for a selected operating mode of the headbox.

So that a minimum of microturbulence is maintained or generated in the at least one pulp suspension, a lamella is arranged at least between two, preferably between all adjacent rows, which is connected in an articulated manner to the turbulence generating means by means of a preferably hinge-like lamella holder.

In two further preferred embodiments, at least some of the polygons are formed of diamonds or kites. The flow channels of at least two adjacent lines can in turn be mirror-inverted and half offset from each other. Here too, the advantages already mentioned arise.

Furthermore, the flow channels preferably have flow cross-sections which expand continuously and / or in steps in the direction of flow of the at least one fibrous suspension. As a result, it is possible to influence the turbulence in the at least one pulp suspension in a targeted manner.

With regard to optimal flow conditions in the turbulence generating means, the flow channels on the inlet side preferably have round, ie rotationally symmetrical inlet surfaces.

The turbulence generating means is in a preferred embodiment a turbulence generator or a tube bank.

In the case of its design as a turbulence generator, it is preceded by a preferably machine-wide intermediate chamber in the direction of flow of the at least one pulp suspension and downstream of a machine-wide headbox nozzle in the direction of flow of the at least one pulp suspension. By contrast, in the case of its execution as a tube bank, the feeding device is arranged directly upstream of the latter in the direction of flow of the at least one fibrous suspension and downstream of the at least one fibrous suspension in the flow direction is a preferably machine-wide intermediate chamber.

The flow channels are preferably formed from a multiplicity of turbulence tubes and / or turbulence tube inserts. These components are preferably at least partially welded to the contact surfaces to the adjacent components with these, soldered and / or glued.

The headbox according to the invention is outstandingly suitable for use in a machine for producing a fibrous web, in particular paper or board web.

In this case, the headbox may be provided in a further embodiment with a well-known from a variety of publications dilution water control. The fibrous web produced in the machine with a headbox according to the invention thus has consistently excellent properties, since, inter alia, the control of both its fiber orientation transverse profile and its basis weight cross-section is possible.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings.

Figuren 1a und 1b

zwei vertikale Längsschnitte durch bekannte Stoffaufläufe einer Maschine zur Herstellung einer Faserstoffbahn; und

Figuren 2 bis 6

schematische Ansichten des mindestens einen Turbulenzerzeugungsmittels des Stoffauflaufs der Figur 1 entgegen der Strömungsrichtung der Faserstoffsuspension.

Show it

FIGS. 1a and 1b

two vertical longitudinal sections through known headboxes of a machine for producing a fibrous web; and

FIGS. 2 to 6

schematic views of the at least one turbulence generating means of the headbox of Figure 1 against the flow direction of the pulp suspension.

FIGS. 1a and 1b show vertical longitudinal sections through headboxes 1 of a machine for producing a fibrous web, in particular a paper or board web, from a pulp suspension 2. The illustrated headboxes 1 can of course also be configured as multilayer headboxes comprising at least two different pulp suspensions for producing a fibrous web use. The fibrous web may in particular be a paper, board or tissue web.

The headbox 1 shown in FIG. 1a has a feed device 3 which feeds the pulp suspension 2, for example in the embodiment of an illustrated transverse distributor tube 4 or a rotary distributor (not illustrated) with a large number of tubes.

Furthermore, the headbox 1 has a turbulence generator 5 (turbulence generating means) arranged downstream of the feeder 3 in the flow direction R (arrow) of the pulp suspension 2. This turbulence generator 5 has a plurality of preferably in rows Z.1 to Z.4 and in columns S (Figure 2) arranged and only schematically shown flow channels 6 (Figure 2). The flow channels 6 are preferably formed in a known manner as thin-walled turbulence tubes and / or turbulence tube inserts with at least partially constant, at least partially diverging, at least partially converging and / or discontinuous flow cross sections.

During operation of the headbox 1, the flow channels 6 are traversed by the pulp suspension 2, wherein they divided into turbulent pulp suspension partial streams 7 (Figure 2) and after emerging from the turbulence generator 5 in a turbulence generator 5 in the flow direction R (arrow) of the pulp suspension 2 downstream headbox 8 is brought together again to allow the formation of a machine-wide fibrous web. The headbox 8 can be considered as a machine-wide chamber.

The headbox 1 shown in FIG. 1b corresponds at least in the second part of the flow path of the pulp suspension 2 to the headbox shown in FIG. 1a. Thus, reference is hereby made to its description.

In extension to the headbox 1 shown in FIG. 1a, the headbox 1 of FIG. 1b has both a tube bank 9 (further turbulence generating means) as a feed device 3 feeding the pulp suspension 2 and the turbulence generator 5 and in the flow direction R (arrow) of the pulp suspension 2 preferably machine-width chamber 10. The chamber 10, which is also referred to as the intermediate chamber, may in a further embodiment have a plurality of partition walls, which at least in sections subdivide it into a plurality of sectioned partial chambers.

The tube bank 9 has a plurality of preferably in lines Z.1 to Z.4 and in columns S (Figure 2) arranged and only schematically shown flow channels 6 (Figure 2). The flow channels 6 are preferably formed in a known manner as thin-walled turbulence tubes and / or turbulence tube inserts with at least partially constant, at least partially diverging, at least partially converging and / or discontinuous flow cross sections.

During operation of the headbox 1, the flow channels 6 are flowed through by the pulp suspension 2, being divided into turbulent pulp suspension partial streams 7 (FIG. 2) and brought together again after leaving the tube bank 9 in the preferably machine-wide chamber 10.

The turbulence generator 5 arranged downstream of the preferably machine-width chamber 10 in the flow direction R (arrow) of the pulp suspension 2 may be similar or even identical to the turbulence generator 5 shown in FIG. 1a.

The respective headbox 1 illustrated in both FIGS. 1a and 1b can have both a straight base contour (FIG. 1a) and a curved base contour (FIG. 1b).

The flow channels 6 of the turbulence generating means 5, 9 shown in both FIGS. 1a and 1b each have an inlet side 11 and an outlet side 12. The respective outlet side 12 has a flat outlet surface 13 formed by the end of the respective flow channel 6. On the inlet side 11, the flow channels 6 have round inlet surfaces 14.

FIGS. 2 to 6 show schematic views of the at least one turbulence generating means 5, 9 of the headbox 1 of FIGS. 1 a and 1 b against the flow direction R (arrow) of the pulp suspension 2.

In this case, the outlet sides 12 of the flow channels 6 arranged in rows Z and columns S can be seen clearly with their outlet surfaces 13. In the illustrations, the flow channels 6 are arranged only in one row Z or in two rows Z. These arrangements are merely exemplary, of course, the flow channels 6 can be arranged in each case in a plurality of rows Z. In addition, each turbulence generating means 5, 9 a vertical A (double arrow), which is aligned by definition orthogonal to the cross-machine direction (CD direction), so the so-called z-axis when viewed locally in or against the machine direction (MD direction) corresponds , The cross machine direction (CD direction) is identical to the orientation of the at least one row Z.

The outlet surfaces 13 of the flow channels 6 are each formed of a polygon 15.1 to 15.3 (Figures 2 to 4 and 6), 15.1 to 15.4 (Figure 5) having polygon 15 having at least two internal angles α, β, which is smaller than 90 ° , in particular less than 75 °. The interior angles α, β are given for the sake of clarity only for an outlet surface 13 of a flow channel 6. Of course, all outlet surfaces 13 of all flow channels 6 have such internal angles α, β.

Furthermore, the polygon sides 15.1 to 15.3 (FIGS. 2 to 4 and 6), 15.1 to 15.4 (FIG. 5) of the respective polygon 15 are oriented differently from the perpendicular A (double arrow) of the turbulence generating means 5, 9. The polygon sides 15.1 to 15.3 (FIGS. 2 to 4 and 6), 15.1 to 15.4 (FIG. 5) of the respective polygon 15 are indicated for the sake of clarity only for a corresponding outlet surface 13 of at least one flow channel 6.

In the embodiments of FIGS. 2, 3 and 6, all the polygons 15 are formed from the same triangles 16. The triangles 16 are here equilateral triangles, so that they have three internal angles α, β, γ, which are smaller than 90 °, in particular smaller than 75 °. In the present case, the three internal angles α, β, γ are each exactly 60 °.

The triangles 16 are generally at least as isosceles, preferably formed and even formed as equilateral triangles.

In the embodiment of FIG. 2, the flow channels 6 of at least two adjacent rows Z are arranged mirror-inverted relative to one another. The mirror axis 17 is formed by a line. Alternatively, they are rectified and offset, preferably arranged in half offset from one another.

By contrast, in the embodiment of FIG. 3, the flow channels 6 of at least two adjacent rows Z are arranged rectilinearly relative to one another.

In a further embodiment according to FIG. 4, at least some of the polygons 15 of the row Z are formed from diamonds 18. The free spaces 19 present between the adjacent diamonds 18 of a row Z can in turn be provided, as indicated, with flow channels 6, whose outlet surfaces 13 can be formed from at least isosceles, preferably equilateral triangles 20.

As already mentioned, each rhombus 18 has at least two internal angles α, β which are smaller than 90 °, in particular smaller than 75 °. The same applies of course to the triangles 20. The triangles 20 are here equilateral triangles, so that they have three internal angles α, β, γ, which are smaller than 90 °, in particular smaller than 75 °. In the present case, the three internal angles α, β, γ are each exactly 60 °.

In the embodiment of FIG. 5, at least some of the polygons 15 of a row Z are formed of kite quadrilaterals 21. The free spaces 22 present between the adjacent kite quadrilaterals 21 of a row Z can, in turn, in turn be provided with flow channels 6 of the adjacent, mirror-inverted and half-displaced ones, or be provided with the same row Z. The mirror axis 17 is formed by a line. Depending on the arrangement and position, the outlet surfaces 13 of the flow channels 6 can be formed of kite quadrilaterals 21 or of at least isosceles, preferably equilateral triangles 23.

Again, as already mentioned, each kite quadrilateral 21 at least two internal angles α, β, which are smaller than 90 °, in particular smaller than 75 °. Of course, the same also applies to the isosceles triangles 23, which each have two internal angles α, β, which are smaller than 90 °, in particular smaller than 75 °.

6 shows another possible embodiment of the turbulence generating means of the headbox 1 in the form of a turbulence generator 5. In this case, at least between two adjacent rows Z is a known to those skilled blade 24 (Figures 1a and 1b). Preferably, a lamella 24 is arranged between all adjacent rows Z in each case. The blade 24 is known by a person skilled in the art and, for example in the German Offenlegungsschrift DE 199 62 709 A1 disclosed and preferably hinge-like blade holder 25 hingedly connected to the turbulence generating means 5, 9. The content of this document is hereby made the subject of the present description.

The illustrated embodiment of flow channels 6 corresponds to the embodiment of Figure 2. It is understood that the embodiments of Figures 3 and 4 can find their appropriate use.

The features of the embodiments of the flow channels 6 of the headbox 1 shown in FIGS. 2 to 6 can also be at least partially combined with one another by the person skilled in the art.

The headbox 1 shown in the figures, in particular in Figures 2 to 6 is particularly suitable for use in a machine for producing a fibrous web, in particular paper or board web.

In summary, it should be noted that the present invention provides a headbox of the type mentioned in the introduction, which avoids the disadvantages of the prior art as far as possible, preferably completely, and thus generates a flow which is as homogeneous as possible immediately downstream of the turbulence generating means. In particular, the lattice tracking flow and any segregation effects are minimized.

LIST OF REFERENCE NUMBERS

1

headbox

2

Fibrous suspension

3

feeder

4

transverse distribution

5

turbulence generator

6

flow channel

7

Fibrous suspension partial flow

8th

headbox

9

tube bank

10

chamber

11

inlet side

12

outlet side

13

outdoor area

14

inlet surface

15

polygon

15.1 to 15.3

polygon side

15.1 to 15.4

polygon side

16

triangle

17

mirror axis

18

diamond

19

free space

20

triangle

21

dragon square

22

free space

23

triangle

24

lamella

25

Blade support

A

Vertical (double arrow)

R

Flow direction (arrow)

S

column

Z, Z.1 to Z.4

row

α

interior angle

β

interior angle

γ

interior angle

Claims (15)

Headbox (1) of a machine for producing a fibrous web, in particular paper or board web, from at least one pulp suspension (2), with at least one feed device (3) feeding the at least one pulp suspension (2) and with at least one turbulence generating means (5, 9) in which, during operation of the head box (1), the at least one pulp suspension (2) flows through a plurality of flow channels (6) each having an inlet side (11) and an outlet side (12), thereby divided into turbulent pulp suspension partial streams (7) and downstream the exit from the turbulence generating means (5; 9) is brought together again in a preferably machine-width chamber (8; 10), wherein the respective outlet side (12) has a flat, formed by the end of the respective flow channel (6) outlet surface (13),
characterized,
in that the outlet surfaces (13) of the flow channels (6) are each formed from a polygon (15) having a plurality of polygon sides (15.1 to 15.3; 15.1 to 15.4) and having at least two internal angles (α, β; α, β, γ), which are smaller than 90 °, in particular smaller than 75 °, and
in that all the polygon sides (15.1 to 15.3; 15.1 to 15.4) of the respective polygon (15) are oriented differently from the vertical (A) of the turbulence generating means (5; 9). Headbox (1) according to claim 1,
characterized,
in that at least some of the polygons (15) are formed by triangles (16; 20; 23), preferably by equilateral triangles (16; 20; 23). Headbox (1) according to claim 2,
characterized,
that the flow channels (6) in a plurality of rows are disposed (Z Z.1 to Z.4). Headbox (1) according to claim 3,
characterized,
that the flow channels (6) at least two adjacent rows (Z; Z.1 to Z.4) are arranged in mirror image to one another. Headbox (1) according to claim 3,
characterized,
that the flow channels (6) at least two adjacent rows (Z; Z.1 to Z.4) are arranged in the same direction to each other. Headbox (1) according to claim 4 or 5,
characterized,
that the flow channels (6) at least two adjacent rows (Z; Z.1 to Z.4) are added, preferably in half are staggered each other. Headbox (1) according to one of claims 3 to 6,
characterized,
in that at least between two, preferably between all adjacent rows (Z; Z.1 to Z.4) a lamella (24) is arranged, which is articulated to the turbulence generating means (5; 9) by means of a preferably hinge-like lamella holder (25). Headbox (1) according to claim 1,
characterized,
that at least some of the polygons (15) of diamonds (18) are formed. Headbox (1) according to claim 1,
characterized,
that at least some of the polygons (15) of dragon four corners (21) are formed. Headbox (1) according to claim 8 or 9,
characterized,
that the flow channels (6) at least two adjacent rows (Z; Z.1 to Z.4) are arranged in mirror image in half and added to each other. Headbox (1) according to one of the preceding claims,
characterized,
that the flow channels (6) have flow cross sections that extend in the flow direction (R) of at least one fibrous suspension (2) continuously and / or stepwise. Headbox (1) according to one of the preceding claims,
characterized,
that the flow channels (6) on the inlet side (11) have round inlet areas (14). Headbox (1) according to one of the preceding claims,
characterized,
that the turbulence generating means is a turbulence generator (5), in the flow direction (R) of the at least one pulp suspension (2) upstream of a preferably machine-wide intermediate chamber (10), and
that the turbulence generator (5) in the flow direction (R) of the at least one pulp suspension (2) is arranged downstream of a machine-wide headbox nozzle (8). Headbox (1) according to one of claims 1 to 12,
characterized,
that the turbulence generating means is a tube bank (9), in the flow direction (R) of the at least one pulp suspension (2), the feed device (3) is directly upstream, and
that the tube bank (9) in the flow direction (R) of the at least one pulp suspension (2) is arranged downstream of a preferably machine-wide intermediate chamber (10). Machine for producing a fibrous web, in particular paper or board web, with a headbox (1) according to one of claims 1 to 14.

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