EP1403423A1 - Head box with swirl inducer - Google Patents

Abstract

The stock inlet (12) to deliver a fiber suspension pulp to a papermaking or cardboard production machine, with a turbulence generator (16) and an outflow jet opening (20), has a deflector blade (14) and a vane (28) to give a flow component across the machine running line (L). This gives a spiral twist to the pulp flow within the jet zone (10) without forming any build-up points. The deflector has a blade, with blades for each turbulence channel line.

Description

The invention relates to a headbox with a turbulence generator and a nozzle.

Such a headbox serves to generate a machine-wide suspension jet in a machine used to produce a material web. The material web formed from the suspension can in particular be a paper or cardboard web. A corresponding headbox is described, for example, in the publications EP 0 211 607 A2 and DE 43 29 810 A1.

The headroom of the headboxes can a. for example, be divided by slats. The slats currently used are essentially designed as flat plates.

The quality of the paper or cardboard is significantly influenced by relative movements between the fiber suspension and the sieve (s). The formation and the burst pressure improve to an optimum with increasing difference between jet and sieve speed (| v | = | v _jet - v _sieve |). Other characteristic values such as SCT _quer have their maximum at around v = 0 m / min. This applies regardless of the particular former concept.

Shaking trestles are sometimes used in paper machines for graphic papers in order to improve the formation by additional shear stress. However, this now has the disadvantage that the formation changes periodically at twice the shaking frequency. Is the shaking frequency f For example, 300 1 / min and the machine speed v, for example 900 m / min, the screen moves between maximum and minimum lateral acceleration by 0.75 m.

The invention has for its object to provide a headbox of the type mentioned, with the properties of the fibrous web produced, in particular paper or cardboard, which require increased fiber orientation in the cross-machine direction, can be improved without noticeably affecting the properties of benefit from greater shear stress on the fiber suspension during sheet formation.

This object is achieved according to the invention by a swirl-generating device for introducing rotary currents having a flow component extending transversely to the machine direction into the fiber suspension within the nozzle space.

Due to this design, flow components pointing transversely to the machine direction are generated in the fiber suspension, as a result of which an increased fiber alignment in the machine cross direction is achieved. The transverse strengths in the fiber suspension relative to the sieve (s) increase. These cross currents expose the fiber suspension to additional shear stresses, which tear open existing fiber flakes and result in a stronger fiber orientation in the cross machine direction.

In a preferred practical embodiment of the headbox according to the invention, the swirl-generating device is installed and / or designed such that that there is no stowage point for the fiber suspension within the nozzle area.

The swirl-generating device can thus in particular be installed and / or designed in such a way that stagnation points at which fibers, filler, fine material, dirt and / or the like can accumulate or accumulate can be avoided.

The swirl-generating device can in particular comprise at least one lamella and / or at least one, in particular, fixed separating element, which, at least in regions, serves to generate the swirl.

The lamella or the separating element is preferably arranged between turbulence channel rows and / or gaps in the turbulence generator. Stagnation points at which fibers, filler, fine material, dirt and / or the like can accumulate or deposit are thus avoided again.

In contrast, the designs described in EP 0 211 607 A2 have stagnation points which entail the risk of dirt accumulating or the formation of fabric specks. In these known headboxes, the twist-producing internals are attached either to the side walls of the headbox or by means of tabs in the tubes of the flow grid. In addition, spacers are described in this publication, which again also have stagnation points and, if attached to the side walls, may also cause problems with regard to possible deformations due to thermal changes in length.
The lamella or the separating element can extend in particular from the turbulence generator into the nozzle space. The number of lamellae or separating elements can be selected, for example, as a function of the number of turbulence channel rows and / or gaps in the turbulence generator.

A preferred practical embodiment of the headbox according to the invention is characterized in that the lamella or the separating element is provided with incisions on its or its rear edge, as viewed in the direction of flow, and the resulting lamella or separating element ends serve to generate swirl.

The ends of the lamellae or separating elements can be limited, in particular with the formation of swirl blades.

In principle, however, such an embodiment is also conceivable in which the lamella or the separating element is provided with attached and / or attached swirl vanes.

The swirl blades can be restricted in the same direction, for example.

In principle, however, such an embodiment is also conceivable in which the swirl blades are at least partially restricted in different directions. The swirl blades can, for example, be alternately set in opposite directions.

If several slats and / or several separating elements are provided, only a part of the slats or separating elements or all the slats or all separating elements can be used to generate the swirl.

The angle at which a respective swirl vane is set with respect to the non-set lamella or separating element part is advantageously in a range from 0 ° to a multiple of 360 ° (several complete revolutions) and preferably in a range from 30 ° to five times 360 ° (five full rotations).

The pitch of a respective swirl blade can vary in the machine direction. The gradient of a respective swirl blade in the machine running direction can, for example, increase steadily.

The slope and / or the length of a respective swirl vane measured in the machine running direction can be selected in particular as a function of the respectively desired intensity of the rotary flow.

According to a further advantageous embodiment of the headbox according to the invention, the lamella or the separating element is provided with at least one non-restricted swirl-producing guide element.

The division of the swirl blades or swirl-producing guide elements is preferably selected as a function of the division of the turbulence channels of the turbulence generator. The division of the swirl blades or swirl-producing guide elements can in particular be an integer multiple or an integer fraction, e.g. B .... 3, 2, 1, 1/2, 1/3, 1/4, ..., correspond to the division of the turbulence channels of the turbulence generator. The division of the swirl blades or swirl-producing guide elements can, for example, also be the same as the division of the turbulence channels of the turbulence generator.

When viewed in the machine running direction, the swirl vanes or swirl-producing guide elements can be aligned with the turbulence channels of the turbulence generator. In principle, however, such an embodiment is also conceivable in which the swirl blades or swirl-producing guide elements, viewed in the transverse direction, are offset relative to the turbulence channels of the turbulence generator. The offset can correspond to half the division, for example.

The division of the swirl blades or swirl-producing guide elements can, however, in principle also be selected independently of the division of the turbulence channels of the turbulence generator.

In a further preferred practical embodiment of the headbox according to the invention, the swirl blades or swirl-producing guide elements are designed so differently that there are different natural frequencies for them, so that vibrations are damped. The swirl vanes or swirl-producing guide elements can at least partially also consist of vibration-damping material.

It is also particularly advantageous if a respective lamella or a respective separating element is designed in such a way that forces introduced by the swirl vanes or the swirl-producing guide elements are absorbed and applied to holding elements of the headbox, such as e.g. the turbulence generator, a side wall delimiting the nozzle space, a separate support and / or the like are released.

The headbox can in principle be designed as a single-layer headbox or as a multi-layer headbox.

The number of fins used in the headbox depends on the number of turbulence channel lines of the turbulence generator or blocks.

The lateral edges of a respective lamella can have a respective distance from the relevant nozzle side wall. For example, an asymmetry with respect to the driver side and the drive side is also conceivable.

The slat ends can have any tip contour, e.g. B. have any conventional tip contour. There are any slat suspensions and in particular any conventional slat suspensions are conceivable. For the rest, a combination of the slat design according to the invention with the previously customary slat designs, for example a joint within the slat etc., is also conceivable.

Figur 1

eine schematische Draufsicht eines Teils einer im Düsenraum eines Stoffauflaufs angeordneten, bereichsweise der Drallerzeugung dienenden Lamelle,

Figur 2

beispielhafte Formen der Drallschaufeln, wobei jeweils die Drallschaufelform vor dem Schränken dargestellt ist,

Figur 3

eine schematische perspektivische Darstellung einer weiteren Ausführungsform einer der Drallerzeugung dienenden Lamelle,

Figur 4

eine schematische Darstellung einer weiteren Ausführungsform einer Lamelle mit angesetzten und/oder aufgesetzten Drallschaufeln,

Figur 5

eine schematische Vorderansicht einer weiteren Ausführungsform einer Lamelle mit nicht geschränkten Drall erzeugenden Leitelementen,

Figur 6

eine schematische Seitenansicht eines nicht geschränkten Drall erzeugenden Leitelements der Ausführung gemäß Fig. 5 und

Figur 7

eine schematische geschnittene Teildarstellung eines Mehrschicht-Stoffauflaufs mit der Drallerzeugung dienenden Lamellen.

The invention is described below with reference to exemplary embodiments with reference to the drawing; in this show:

Figure 1

2 shows a schematic top view of part of a lamella arranged in the nozzle area of a headbox and serving in part to generate the swirl,

Figure 2

Exemplary shapes of the swirl blades, wherein the swirl blade shape is shown before the cabinet,

Figure 3

2 shows a schematic perspective illustration of a further embodiment of a lamella which serves to generate swirl

Figure 4

1 shows a schematic representation of a further embodiment of a lamella with attached and / or attached swirl blades,

Figure 5

2 shows a schematic front view of a further embodiment of a lamella with guide elements which do not produce a twisted swirl,

Figure 6

is a schematic side view of a non-twist-producing guide element of the embodiment according to FIGS. 5 and

Figure 7

is a schematic sectional partial view of a multi-layer headbox with the swirl serving slats.

FIG. 1 shows a schematic plan view of part of a lamella 14 which is arranged in the nozzle space 10 of a headbox 12 and which serves in part to generate the swirl.

The lamella 14 extends from the last turbulence block of a turbulence generator 16 of the headbox 12 into the nozzle chamber 10, which is laterally delimited by nozzle walls 18, of which only one can be seen in FIG. 1. An aperture 22 is provided in the area of the outlet gap of the relevant nozzle 20 of this headbox 12.

L₀ =

Düsenlänge

L₁ =

Lamellenlänge

I₂ =

Länge des Lamellengrundkörpers

I₃ =

ungeschränkte Länge der Drallschaufel

I₄ =

geschränkte Länge der Drallschaufel

B₀ =

lichte Kastenweite des Stoffauflaufs

b_s =

Randspalt zwischen Düsenwand und Lamelle

b_ra =

Randabstand eines jeweiligen äußeren Lamellenendes zur betreffenden seitlichen Düsenwand, wobei beispielsweise auch eine Unsymmetrie zwischen der Führerseite und der Triebseite möglich ist

b_L =

Lamellenbreite

b₁ =

Breite der Drallschaufel an der Wurzel

b₂ =

gegenseitiger Abstand der Drallschaufeln

In this FIG. 1, certain quantities are designated with the following abbreviations:

L ₀ =

nozzle length

L ₁ =

lamellar length

I ₂ =

Length of the basic slat body

I ₃ =

unlimited length of the swirl vane

I ₄ =

limited length of the swirl vane

B ₀ =

Clear box width of the headbox

b _s =

Edge gap between the nozzle wall and lamella

b _ra =

Edge distance of a respective outer slat end to the relevant lateral nozzle wall, an asymmetry between the driver side and the drive side being possible, for example

b _L =

slat width

b ₁ =

Width of the swirl vane at the root

b ₂ =

mutual spacing of the swirl blades

The direction of flow of the fiber suspension is indicated by "S". It corresponds to the machine direction L.

The headbox 12 comprises a swirl-generating device, here at least one lamella 14 serving at least in regions to generate the swirl, for introducing rotary flows into the fiber suspension within the nozzle space 10 having a flow component extending transversely to the machine direction L.

The swirl-producing lamella 14 is provided with incisions 24 on its rear edge, as viewed in the direction of flow L, which results in a plurality of lamella ends 26, which in the present case are set at least in regions to produce swirl, with the formation of swirl vanes 28. "I ₄ " in FIG. 1 thus indicates the length of a respective swirl blade 28.

The lamella ends 26 can, for example, all be mutually limited in the same direction or alternately. If a plurality of lamellae 14 are installed in the headbox 12, then all, part of them or only one can be designed in the manner specified for generating swirl.

• L₀ (Düsenlänge) =300 bis 1200 mm, vorzugsweise 400 bis 1000 mm
• l₁ (Lamellenlänge)= von einem Wert nahe 0 bis zum 1,2-fachen der Düsenlänge L₀, wobei im Fall L₁ > L₀ vorzugsweise aufgesetzte Drallelemente oder-schaufeln im Düsenraum vorgesehen sein können (siehe weiter unten)
• l₂ (Länge Lamellengrundkörper) = 0,01 bis 0,95 · L₀, vorzugsweise 0,02 bis 0,5 · L₀
• l₃ (ungeschränkte Länge der Drallschaufel) = 0,00 bis 0,95 · L₂
• l₄ (geschränkte Länge der Drallschaufel) = 1,00 bis 0,05 · L₂
• b_s (Randspalt zwischen Düsenwand und Lamelle) = z.B. 0,5 bis 10 mm
• b_L (Lamellenbreite): Maximum = entsprechend dem bisher üblichen Wert, Minimum = B₀ - 2 · (b₂ + b₂)
• b₁ (Breite der Drallschaufel an der Wurzel) = 3 bis 100 mm, vorzugsweise 5 bis 50 mm
• b₂ (Abstand der Drallschaufeln bzw. Drallelemente) = 0 bis b₁
• t (Teilung) = 0 bis 100 mm, vorzugsweise 5 bis 50 mm

For example, the sizes specified above can have the following values:

• L ₀ (nozzle length) = 300 to 1200 mm, preferably 400 to 1000 mm
• l ₁ (lamella length) = from a value close to 0 to 1.2 times the nozzle length L ₀ , where in the case of L ₁ > L ₀ preferably twist elements or blades attached can be provided in the nozzle space (see further below)
• l ₂ (length of lamella base body) = 0.01 to 0.95 · L ₀ , preferably 0.02 to 0.5 · L ₀
• l ₃ (unrestricted length of the swirl blade) = 0.00 to 0.95L ₂
• l ₄ (restricted length of the swirl blade) = 1.00 to 0.05 · L ₂
• b _s (edge gap between nozzle wall and lamella) = e.g. 0.5 to 10 mm
• b _L (slat width): maximum = according to the usual value, minimum = B ₀ - 2 · (b ₂ + b ₂ )
• b ₁ (width of the swirl vane at the root) = 3 to 100 mm, preferably 5 to 50 mm
• b ₂ (distance of the swirl blades or swirl elements) = 0 to b ₁
• t (division) = 0 to 100 mm, preferably 5 to 50 mm

FIG. 2 shows exemplary shapes of the swirl vanes 28, the swirl vane shape in each case being shown before the cabinets. The respective setting directions are indicated below the respective swirl vane shape.

The lamella ends 28 can thus, for example, have a triangular shape (see FIGS. 2a, d, e with a triangle tapering in the machine direction L (see FIGS. 2a, d) or a triangle that widens in the machine direction L (see FIG. 2e), have a rectangular shape (cf. FIG. 2b), the shape of a truncated cone (cf. FIG. 2c) or a shape shown in FIG. 2f in which the initially generally strip-shaped lamella end 28 is provided with a semicircular recess 30 at the free end. According to FIG. 2g, a respective lamella end 28 can also be jagged on its rear edge in the machine running direction L, for example.

As can be seen in particular from FIG. 2h, the lamellae 14 can also have structured tips, for example.

FIG. 3 shows a schematic perspective illustration of a further embodiment of a lamella 14 used to generate the swirl.

B₁ =

Breite des nicht geschränkten Lamellenabschnitts

B₂ =

Breite des freien Endes des geschränkten Bereichs bzw. der Drallschaufel 28

L₁ =

Länge des nicht geschränkten Lamellenabschnitts

L₂ =

Länge des geschränkten Bereichs bzw. der Drallschaufel 28

L₃ =

Länge eines Beruhigungsbereichs

In this figure 3 certain sizes are given the following designations:

B ₁ =

Width of the non-set slat section

B ₂ =

Width of the free end of the restricted area or of the swirl vane 28

L ₁ =

Length of the non-set slat section

L ₂ =

Length of the restricted area or of the swirl vane 28

L ₃ =

Length of a calming area

The width B _{1 of} the non-restricted lamella section can, for example, be equal to the division of the turbulence channels of the turbulence generator 16. In addition, this width B _{1 of} the non-set slat section can be, for example, the same, larger or smaller than the width B _{2 of} the free end of the set area or of the swirl vane 28.

The length L _{1 of} the non-restricted slat section can be ≥ 0. The respective swirl strength can be specified via the length L _{2 of} the restricted area or the swirl vane 28. The length L _{3 of} the calming area is decisive for the calming that arises.

The free end of the restricted area or of the swirl vane 28 can be provided at a distance from the screen 22 (cf. FIG. 1).

The set row or swirl vanes 28 of the lamella 14 can be offset in the transverse direction to the turbulence channels of the turbulence generator 16, wherein the offset can correspond in particular to half the division of the turbulence channels of the turbulence generator 16.

In FIG. 3, various possible directions of rotation for the restricted areas or swirl vanes 28 are given purely by way of example, wherein “+” means a right turn and “-” each means a left turn or vice versa.

FIG. 4 shows a schematic representation of another embodiment of a lamella 14, in which this lamella 14 is provided with attached and / or attached twist scoops 28 '.

For the rest, the headbox in question can in particular at least essentially be designed as described in connection with FIG. 1. This means, inter alia, that in particular the swirl vane 28 'attached or attached can in principle, for example, at least essentially be designed in the same way as was described in connection with the swirl vane 28 by way of example with reference to FIG. 1.

Figure 5 shows a schematic front view of a further embodiment of a lamella 14, which in the present case, however, has a "straight", i.e. is not provided twist-generating guide elements 32 is provided. FIG. 6 shows a schematic side view of a guide element 32 of the design according to FIG. 5 which does not form a swirl. In both FIGS. 5 and 6, the machine direction is in each case "MD", the transverse direction is in each case "CD" and the vertical direction is in each case "VD". indicated.

FIG. 7 shows a schematic sectional partial view of a multi-layer headbox 12 with at least one separating element 34 and several swirl-producing lamellae 14.

In principle, a respective separating element 34 can also be designed as a swirl-generating element in the manner described above in connection with the lamellae or can be provided with swirl blades.

LIST OF REFERENCE NUMBERS

10

nozzle chamber

12

headbox

14

lamella

16

turbulence generator

18

nozzle wall

20

jet

22

cover

24

incision

26

lamella end

28

swirl blade

28 '

swirl blade

30

recess

32

unrestricted guide element

34

separating element

L

Machine running direction, flow direction

S

flow direction

Claims (31)

Headbox (12) with a turbulence generator (16) and a nozzle (20),
marked by
a swirl generating device (14, 28, 32, 34) for introducing rotary currents having a flow component extending transversely to the machine direction (L) into the fiber suspension within the nozzle space (10). Headbox according to claim 1,
characterized,
that the swirl generating device (14, 28, 32, 34) is installed and / or designed in such a way that there is no stowage point for the fiber suspension within the nozzle space (10). Headbox according to claim 1 or 2,
characterized,
that the swirl-generating device comprises at least one lamella (14) and / or at least one, in particular fixed, separating element (34) which, at least in regions, is used to generate the swirl. Headbox according to claim 3,
characterized,
that the lamella (14) or the separating element (34) is arranged between turbulence channel rows and / or gaps of the turbulence generator (16). Headbox according to one of the preceding claims,
characterized,
that the lamella (14) or the separating element (34) extends from the turbulence generator (16) into the nozzle chamber (10). Headbox according to one of the preceding claims,
characterized,
that the number of fins (14) or separating elements (34) is selected as a function of the number of turbulence channel rows and / or gaps of the turbulence generator (16). Headbox according to one of the preceding claims,
characterized,
that the lamella (14) or the separating element (34) is provided with incisions (24) on its or its rear edge when viewed in the direction of flow (L) and the resulting lamella or separating element ends (26) serve to generate swirl. Headbox according to claim 7,
characterized,
that the lamella or separating element ends (26) are set to form swirl blades (28). Headbox according to one of claims 1 to 6,
characterized,
that the lamella (14) or the separating element (34) is provided with attached and / or attached swirl vanes (28 '). Headbox according to claim 9,
characterized,
that the swirl blades (28, 28 ') are set in the same direction. Headbox according to claim 9,
characterized,
that the swirl blades (28, 28 ') are at least partially set in different directions. Headbox according to claim 11,
characterized,
that the swirl blades (28, 28 ') are alternately set in opposite directions. Headbox according to one of the preceding claims,
characterized,
that a plurality of lamellae (14) and / or a plurality of separating elements (34) are provided and only part of the lamellae (14) or separating elements (34) is used to generate the swirl. Headbox according to claim 1 to 13,
characterized,
that a plurality of fins (14) and / or a plurality of separating elements (34) are provided and all the fins (14) or all separating elements (34) serve to generate swirl. Headbox according to one of the preceding claims,
characterized,
that the angle over which a respective swirl vane (28, 28 ') is set in relation to the non-set slat or separating element part in is in a range from 0 ° to a multiple of 360 ° and preferably in a range from 30 ° to five times 360 °. Headbox according to one of the preceding claims,
characterized,
that the pitch of a respective swirl blade (28, 28 ') varies in the machine direction (L). Headbox according to claim 16,
characterized,
that the gradient of a respective swirl blade (28, 28 ') increases continuously in the machine direction (L). Headbox according to one of the preceding claims,
characterized,
that the slope and / or the length of a respective swirl blade (28, 28 ') measured in the machine direction L is selected as a function of the respectively desired intensity of the rotary flow. Headbox according to one of the preceding claims,
characterized,
that the lamella (14) or the separating element (34) is provided with at least one swirl-producing guide element (32). Headbox according to one of the preceding claims,
characterized,
that the division of the swirl blades (28, 28 ') or swirl-producing guide elements (32) is selected as a function of the division of the turbulence channels of the turbulence generator (16). Headbox according to claim 20,
characterized,
that the division of the swirl blades (28, 28 ') or swirl-producing guide elements (32) corresponds to an integral multiple or an integral fraction of the division of the turbulence channels of the turbulence generator (16). Headbox according to one of the preceding claims,
characterized,
that the division of the swirl blades (28, 28 ') or swirl-producing guide elements (32) is equal to the division of the turbulence channels of the turbulence generator (16). Headbox according to claim 22,
characterized,
that the swirl blades (28, 28 ') or swirl-producing guide elements (32), viewed in the machine running direction L, are aligned with the turbulence channels of the turbulence generator (16). Headbox according to claim 22,
characterized,
that the swirl blades (28, 28 ') or swirl-producing guide elements (32), viewed in the transverse direction, are offset with respect to the turbulence channels of the turbulence generator (16). Headbox according to claim 24,
characterized,
that the offset corresponds to half the division. Headbox according to one of the preceding claims,
characterized,
that the division of the swirl blades (28, 28 ') or swirl-producing guide elements (32) is selected independently of the division of the turbulence channels of the turbulence generator (16). Headbox according to one of the preceding claims,
characterized,
that the swirl vanes (28, 28 ') or swirl-producing guide elements (32) are designed so differently that there are different natural frequencies for them. Headbox according to one of the preceding claims,
characterized,
that the swirl blades (28, 28 ') or swirl-producing guide elements consist at least partially of vibration-damping material. Headbox according to one of the preceding claims,
characterized,
that a respective lamella (14) or a respective separating element (34) is designed such that forces introduced by the swirl vanes (28, 28 ') or the swirl-producing guide elements (32) are absorbed and held on holding elements of the headbox (12) , such as the turbulence generator (16), a side wall (18) delimiting the nozzle space (10), a separate support and / or the like Headbox according to one of the preceding claims,
characterized,
that it is designed as a single-layer headbox. Headbox according to one of claims 1 to 29,
characterized,
that it is designed as a multi-layer headbox.

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