DE102005010628A1 - Jet outlet for papermaking headbox has series of roughly horizontal lamella guiding fiber discharge - Google Patents

Abstract

In a paper manufacturing process a cellulose fiber suspension is released from a headbox through a wide outlet jet in a gap between a breast roller and a forming drum. The jet zone (2) has a series of horizontal parallel guide vanes (6) forming horizontal suspension layers. The unrestricted distance (L) between the jet release point at the horizontal outlet blade (7) is 400 mm or more. The distance (L) is preferably 600 mm or more. The thickness of the suspension outlet is 0.5 mm or less. One or more of the lamella has a structured tip.

Description

The The present invention relates to a headbox with a nozzle, from which exits the pulp suspension and after a free jet length on a guide, in particular a forming device with forming roll and forming fabric, meets, in particular with at least one arranged in the nozzle Lamella.

Such a headbox serves to produce a machine-wide suspension jet in a machine used to manufacture the material web. The material web formed from the suspension may in particular be a paper or board web. A corresponding headbox is for example in the document DE 101 50 951 A1 described.

The surface The free jet of previous headboxes is very rough and uneven. this leads to for larger free jet lengths for fan out of the jet and to air inclusions in sheet formation, causing a general deterioration the formation leads to massive formation disorders. It will therefore be possible small free jet lengths sought.

Of the Invention is based on the object, a headbox of the beginning to improve the type mentioned.

These Task is solved by that the headbox is designed so that the free jet length more than 400 mm.

The Training the headbox so that the free jet length more than 400 mm, has the advantage that annoying turbulences in the free jet decay better can. As a result, the sheet formation is improved over known headboxes.

Advantageous can the beam lengths 500 mm or more or 600 mm or more. The sheet formation can be further improved.

The roughness of the surface of the surface caused by the long free jet Free jet can be reduced by having at least one Slat has a sharp point. Preferably, the thickness is the tip is 0.8 mm or less, especially 0.5 mm or less. Hereby can good results are achieved.

To a further embodiment of the invention has at least one Slat on a structured tip, especially all slats with more than 0.8 times the nozzle length. By suitable structuring can so-called Karman's vortex can be avoided. The smoothness of surface of the free jet can be further increased thereby.

The Length of Slats in the nozzle can basically bigger or be smaller than the nozzle length. This means, the slats can inside the nozzle end or over the nozzle end protrude. When the slats over the nozzle end protrude, it is preferred that the fins no more than 100 mm, in particular not more than 50 mm protrude beyond the nozzle end.

Especially it is also preferable if at least one lamella has a roughness Ra of 1.5 μm or less, in particular 0.5 microns or less. This can reduce the roughness and unevenness the free-jet surface be further reduced.

Prefers it is also when the flow channels, formed are symmetrically formed by the slats, so if in particular the lamellae are arranged mirror-symmetrically to the nozzle center plane. The shape of the free jet can be further improved.

Further Benefits arise when the nozzle in the end to effect a strong beam convergence is formed. This can be achieved be that acceleration of the suspension especially in the end the nozzle takes place. Also, this can be a smoother surface of the Free jet can be achieved.

Especially suitable for achieving such end convergence is the arrangement at least one aperture at the nozzle outlet, where the board of the aperture is large. A symmetrical Training can be achieved through two apertures.

Of the Headbox according to the invention is particularly advantageous for use with dilution water-regulated headboxes, since no diaphragm deformation is required to control the suspension jet is. Furthermore The headbox can be used both as a single-layer and multi-layer casserole be educated.

embodiments The invention is illustrated in the drawings and will be described below. They show, in each case in a schematic representation,

1 a partially cut sides view of a headbox according to the invention,

2 a variant to 1 and

3 a fin end.

The in 1 Headbox shown comprises a nozzle 1 from which a pulp suspension 2 exits and after a free jet length L on a former with forming roller 3 and forming screens 4 . 5 meets. The free jet length L is more than 400 mm. It can also be more than 500 mm or more than 600 mm. In the nozzle 1 are slats 6 arranged. Also, at the top of the nozzle 1 a panel 7 available.

As in 2 can also have two apertures 7 be provided. The slats 6 are here symmetrical to the nozzle center plane 8th arranged. Other than shown, the slats 6 also about the end 9 the nozzle 1 protrude, in particular by a maximum of 100 mm or a maximum of 50 mm.

The slats 6 are pointed at their ends, as in 3 is shown. In particular, the thickness dS of the slats 6 at its end 10 maximum 0.8 mm, in particular maximum 0.5 mm.

The tips of the slats 6 can also be structured. The surfaces of the slats 6 have a roughness Ra of 1.5 μm or less, in particular 0.5 μm or less. The board of the blinds 7 , that is, the amount by which these in the jet of the pulp suspension 2 protrude, is chosen particularly large, to a strong beam convergence at the nozzle exit 9 to reach. The headbox may be designed, in particular, as a dilution-water-regulated headbox.

1

jet

2

Fibrous suspension

3

forming roll

4

forming fabric

5

forming fabric

6

lamella

7

cover

8th

Median plane of 1

9

End of 1

10

End of 6

L

Free jet length

dS

Density of 10

Claims (12)

Headbox with a nozzle ( 1 ) from which the pulp suspension ( 2 ) and after a free jet length (L) on a guide, in particular a forming device with Formierwalze ( 3 ) and forming fabric ( 4 . 5 ), in particular with at least one in the nozzle ( 1 ) arranged lamella ( 6 ), characterized in that the head box is formed so that the free jet length (L) is more than 400 mm. Headbox according to claim 1, characterized that the free jet length (L) is 500 mm or more. Headbox according to claim 1, characterized that the free jet length (L) is 600 mm or more. Headbox with a nozzle ( 1 ) from which the pulp suspension ( 2 ) and after a free jet length (L) on a guide, in particular a forming device with Formierwalze ( 3 ) and forming fabric ( 4 . 5 ), in particular with at least one in the nozzle ( 1 ) arranged lamella ( 6 ), in particular according to one of the preceding claims, characterized in that at least one lamella ( 6 ) a sharp point ( 10 ) having. Headbox according to claim 4, characterized in that the thickness of the tip ( 10 ) Is 0.8 mm or less, especially 0.5 mm or less. Headbox according to one of the preceding claims, characterized in that at least one lamella ( 6 ) a structured tip ( 10 ) having. Headbox according to one of the preceding claims, characterized in that the lamellae ( 6 ) by a maximum of 100 mm, in particular a maximum of 50 mm above the end ( 9 ) of the nozzle ( 1 ) stand out. Headbox according to one of the preceding claims, characterized characterized in that the roughness Ra of the fin surface is 1.5 μm or less, in particular 0.5 microns or less. Headbox according to one of the preceding claims, characterized in that the nozzle ( 1 ) to its median plane ( 8th ) is mirror-symmetrical. Headbox with a nozzle ( 1 ) from which the pulp suspension ( 2 ) and after a free jet length (L) on a guide, in particular a forming device with Formierwalze ( 3 ) and forming fabric ( 4 . 5 ), in particular with at least one in the nozzle ( 1 ) arranged lamella ( 6 ), in particular according to one of the preceding claims, characterized in that the nozzle ( 1 ) in the End area, ( 9 ) is designed to effect a strong beam convergence. Headbox according to claim 10, characterized in that at the nozzle outlet ( 9 ) at least one aperture ( 7 ) is arranged with a large board. Headbox according to one of the preceding claims, characterized characterized in that it is a dilution water-regulated headbox.