EP0899376A2 - Deckle frame arrangement for a forming section - Google Patents

Abstract

The side shield (9) structure of the peripheral sieve (10), at the pulp entry end of a fourdrinier, has a shape and/or dimensions to give an adjustable gap between them and the center line of the fourdrinier, at least over part of their length. At least one side shield (9) has an adjustment system (18.1-18.3) to set its angular alignment round an axis parallel to the lateral line of the machine. At least one side shield (9) has an adjustment (19) to set the gap between them, pref. parallel to the lower fourdrinier. The side shields (9) are elastic, for at least part of their length along the machine line. The shields (9) have at least one linkage, on an axis at right angles to the fourdrinier plane. The side shields (9) have at least one mechanism (16.1,16.2) for distortion, at least along the machine line, through the application of a pull and/or push pressure, with at least one direction component aligned across the machine line. One distortion unit (16.1,16.2) engages a lifting arm at one side of the shields, to exert a pull and/or push force along the machine line. Preferred Features: The restraint surfaces at the sides of the wet pulp have an adjustable gap between them, to set the web width. The side shields (9) are positioned, in relation to the surface of the fourdrinier, so that the lateral impulses in the pulp flow can be dissipated through the gap between the fourdrinier and the side shields (9). The available width of the surface for the fiber suspension, along the machine line, is set according to the laws for the continuity equation for incompressible liquids, increased according to a variable flow speed, to maintain a constant layer height at the edge zones.

Description

The invention relates to a sheet formation system Fourdrinier paper machine or Fourdrinier paperboard machine according to the preamble of claim 1 and a Process for the reduction of edge waves according to the Preamble of claim 9.

Draw the sheet forming systems of Fourdrinier machines through an endless sieve to form Paper webs or cardboard webs, which over a open, flat table surface. A strong with Water-diluted paper pulp, the Fibrous suspension, becomes a headbox admitted, the one with a machine width Nozzle a machine-wide stock suspension jet generated and puts this on the running sieve. The aqueous medium is then passed through the sieve dewatered and there is a fibrous web, which in further course of the machine to the finished paper or Cardboard web is processed.

After the point of impact of the fabric suspension jet the sieve shows the material suspension at the edges of the Siebes the tendency to run sideways. For this Basically in the border area of the sieves after the nozzle of the headbox so-called format plates attached, the lateral run of the Stock suspension and thus a dilution of ultimately emerging paper web in this area should prevent.

Such a format label is for example from the German published application DE 43 34 641 A1 known, the content of which is hereby fully disclosed in this registration is included. The task of this invention shown there is a constant accumulation of fiber layers, which can be found in the Edge areas of the flowing pulp suspension by drying and then bonded into the peel fresh fiber suspension, to avoid. For this it is proposed in the area of Spray spray fountain format plates to provide the Surfaces of the format plates with a flowing Cover water film so that such Drying of fiber accumulations is avoided. The format label itself consists of a flat one Ledge by hollow profiles in their Directional stability is stiffened and their Alignment points exactly in the machine direction.

A major problem with this known Format signs in the sheet formation system consist of that in the area of the marginal boundary layers flowing material suspension secondary flows form that lead to edge waves in the stock suspension lead towards the center of the machine.

It is the object of the invention, the known Sheet forming system of a Fourdrinier machine, especially the format plates of the sheet formation system to develop further in such a way that the formation of Edge waves reduced, or as far as is avoided as possible.

It is also an object of the invention to provide a method to reduce edge waves in a Sheet formation system of a paper or board machine to be described in the area of the stock suspension task.

The first task to improve the Sheet formation system is characterized by the characteristics of the Claim 1 solved. The second task for Description of a method for reducing Edge waves is characterized by the features of claim 9 solved.

The inventors recognized the following:

The marginal problem in the sheet formation system is one Problem at the interface between headbox and Wire section. It includes the guidance of the free jet and the associated reflection waves and a part the format limit for sheet formation. Due to the Improvement of the transverse profiles of the paper web through the recent developments in the field of headbox, which allow a sectioned material density regulation, marginal problems have a significantly more negative effect than so far. The causes of these edge waves or Reflection waves can have different causes.

Generally the edge waves are caused by edge effects, which is in the form of an arc at the top Express the format sign of the secondary currents. Due to the large wetted areas, the flow in the Edge area braked considerably and decreases due to the Continuity conditions a larger space in Claim. This way, the slower blocks Edge flow of the main flow, which emerges at the nozzle outlet approximately with outlet width, on the length of the Format label increasingly the desired Flow direction. The consequence is necessarily a local one Beam deflection towards the center of the machine, which as Reflection wave appears.

This problem is particularly slow-moving Machines affected with large stomata operate. The reflection waves have enough here Time to sit on the Fourdrinier in the to expand the production-relevant area of the railway. The different effects are with fast machines a little weaker, but basically the same available.

The secondary flows can be different Effects arise:

For design reasons, the bezel must have a certain undersize, which creates a gap between the cover and the format label. This should ideally be about 0.15 mm, but 0.25 mm do not exceed. The groove of the panel seal cannot be brought up to the tip of the panel. A Self-sealing in this area by fibers, especially with faster machines, is due to the prevailing high pressure there difficult. In addition to the Secondary flow on the format label can cause problems such as Spraying, contamination of the wire section and Braids appear. This can be significant Cause disturbances, especially if the gap, for example, by a not centered Aperture position, too large.

Another way of creating Secondary flows can be caused by wall friction be. Due to the wall friction in the headbox and on Format label creates a boundary layer, the Flow velocity versus Flow rate of the central main flow is reduced. Without a format label, the beam would have it Strive to expand sideways and through that slower flow speeds required larger ones To create volume. As this is due to the format limitation is prevented, builds an arc on the format label a secondary flow.

Another way of creating Secondary flows is that on Beam impact point the beam through the Change of direction at the edge is usually a strong one Receives momentum in the transverse direction because the beam The effort has to expand to the side. Of the Cross pulse leads to an additional, arcuate Secondary flow on the format label. This effect is strongly depends on the angle of incidence, which is very different individually from the geometry of the wire section and Headbox position results.

Another way to create Secondary flows can be caused by shaking the sieve be given. By shaking the sieve Stock suspension speed components in Imprinted transverse direction, with a Format limitation the impulses arising here be reflected and in the form of an edge wave Run in the middle of the web.

The essential element of the invention is that the inventors recognized that the Reflection waves or edge waves reduced can be if the secondary flow has room for one lateral expansion is given.

This is the case with the known, not flexible Format labels possible by placing between sieve and Shape a gap is set as required, through which an essential part of the impulse is from the side is "released". This reduces the Edge wave essential. However, building Avoid spray fabric in this area become. A solution to this problem that then arises is described in DE 43 34 641 A1 cited above been.

Another option is to use the unwanted secondary flow through the To give space to the format label contour and thus the Main flow not to narrow or not to redirect towards the center of the machine. This can for example with an adjustable format label will be realized. With this version, the Flow shortly after exiting the nozzle to be influenced. The secondary flows, which are previously arched upwards on the format label trained, are discharged laterally, Reflection waves are reduced respectively purposefully steered closer to the edge without the goal the format limit is abandoned. Here, the Adjust the format label so that with increasing distance from the headbox Change, preferably a broadening of for the area available for the stock suspension arises.

Such a new format label can consist of several parts, preferably be carried out in two parts, from The format limit from one end of the table plate component that can be specifically bent by clamping elements, preferably a plastic element. By the maximum adjustability also perpendicular to Sieve surface can the format label very close to that Sieve (preferably about 0.5 mm) are placed.

According to the basic idea of the invention and to the solution the task is therefore proposed, a known one Sheet forming system of a fourdrinier paper machine or Fourdrinier board machine with a headbox, at least one rotating sieve and at least two, attached to the edge of the sieve Further develop format signs in such a way that the Side shields are designed or attached in such a way that the clear distance of the side shields at least over a substantial part of their length in Machine direction can increase.

In addition, the side shields can be advantageous seen at least in sections in the machine direction train elastic. The elastic training of the Format label can for example by perpendicular to Weakening of the material thickness of the Format label or by a replacement in places of the material through a particularly elastic material such as plastic or rubber. The format label can also move can be achieved if it has at least one joint is provided, the axis of which is substantially perpendicular or is also slightly inclined to the sieve level.

Another advanced training can be included exist that at least on the side shields a device for deforming the side shields is provided at least in the machine direction. This Embodiment can be further developed by that at least one of the devices for deformation the side shields with a tensile and / or compressive force at least one directional component transverse to Exercises machine direction and / or that at least one of the devices for deforming the format plates a lever arm arranged on the side of the format label attacks and a tensile and / or compressive force with at least one directional component in Machine direction.

According to the inventive concept, a method is also used to reduce edge waves in a Sheet forming system of a fourdrinier paper machine or Fourdrinier board machine in the field of Material suspension application on a rotating sieve proposed, in order to limit the sheet forming a mechanical side boundary is used, the area available for the stock suspension increasing in the machine direction, continuously changed, preferably widened.

In a development of this The process of enlarging the area in essentially according to the rules of Continuity equation for incompressible liquids, according to the changing flow rate of the edge area enlarged by the layer height of the Keep material suspension constant in the edge area.

It is understood that the above and Features of the invention to be explained below not only in the specified combination, but also in other combinations or in USP can be used without the scope of Leaving invention.

Further features and advantages of the invention result from the following description of a preferred embodiment with reference to the painting.

The invention will now be described in more detail using a Embodiment and the drawings closer are explained.

Figur 1:

Längsschnitt im Bereich des Strahlauftreffpunktes des Blattbildungsbereiches;

Figur 2:

Schnitt A aus Figur 1;

Figur 3:

Draufsicht auf ein erfindungsgemäßes Formatschild;

Figur 4:

Seitenansicht des erfindungsgemäßen Formatschildes;

Figur 5:

Schnitt A-A aus Figur 4.

Show it:

Figure 1:

Longitudinal section in the area of the beam impact point of the sheet formation area;

Figure 2:

Section A from Figure 1;

Figure 3:

Top view of a format label according to the invention;

Figure 4:

Side view of the format label according to the invention;

Figure 5:

Section AA from FIG. 4.

In Figure 1 is a partial view of a Sheet formation system shown in longitudinal section. On on the left is the nozzle area of the Headbox 1 with the lower lip 2 and the aperture 3 shown above. By the Nozzle gap between the aperture 3 and the lower lip 2 the stock suspension is pushed through and hits in Beam impact point 6 on the sieve 10 below on. The screen 10 runs over a breast roll 12 a horizontally running sieve table 11. over the fabric suspension layer is characterized by a variety of Arrows the secondary flow 5, which is in this Area builds up, shown. In addition, the Figure the format label 9 attached to the side his wall area over a dried one Fabric area 7 and a wet area underneath 8 has.

The cross section A indicated in FIG. 1 is in FIG Figure 2 shown. This Figure 2 shows a section through the sieve 10 below, the format label 9, that is adjusted at a distance 14 from the running sieve 10 is. To the left of the format label is Material suspension layer 4 can be seen that the Side of the format label through the secondary flow 5 builds up and shows the tendency on the side wall of the Crawl upwards. By a appropriate adjustment of the format label 9 is this tendency of the current to creep up reduced. This happens because of the gap 14 a derivative of the pressure pulse that normally runs against the format label 9 and is reflected there is avoided. The pressure pulse, respectively a substantial part of the pressure pulse can be due to this Escape way between sieve 10 and 9 format label.

Another improvement to reduce the Secondary flow and the resulting edge waves is shown in Figure 3. Figure 3 shows the Area of Figure 1 in plan view. Coming from above the nozzle area of the headbox 1 can be seen, which has a side wall 15 on which the inventive format label 9 with a Adjustment device 20 is attached. The format label 9 is in this example of two connected Segments 9.1 and 9.2 built up, each over one relatively thick-walled main area and a thinner one and thus have elastic transition region 26. In the continuously drawn representation is that Format label aligned essentially in a straight line shown. The thick-walled main areas themselves have side arms 9.3 and 9.4 that again in the machine direction on adjusting rods 16.1 and 16.2 are attached.

By changing the length accordingly Adjustment rods result in elastic deformation the format label in the area of the thinner version (lower section modulus). The format label moves slightly to the direction of the paper web and can thus be used for the undisturbed flow of the Provide material suspension necessary space, without changing the suspension height.

A possible, but exaggerated front line the format label is dashed by lines 17 shown. This format label can preferably be made from Made of plastic or stainless steel become. Here, the elastic regions 26 can Gain elasticity by weakening the Material thickness is generated in this area 26.

For clarification, there is one in the bottom left of FIG Magnifying glass of such an exemplary weakening of the Area 26 shown. This weakening of Material thickness causes the material to be elastic and mobility of the format label around an axis perpendicular to the screen plane through which the format label in can be aligned as desired. The Alignment can be done so that the Layer of the format label in contact with the material suspension, such as by the curved arrows 27 on both sides indicated an angle to either side of the Screen direction can assume. In special cases it may even be advantageous that these angles in upstream part of the format label 9.1 from Point away the center line of the sieve and in the downstream part 9.2 on the center line of the sieve to assign or vice versa.

Figure 4 shows a side view of this Embodiment of a format label according to the invention, the longitudinal adjustment of the format label over the Adjustment rods 16.1 and 16.2 can be clearly seen. The Format label itself is with a screw connection the adjusting screws 18.1, 18.2 and 18.3 on the Side wall 15 of the headbox attached. By a Adjustment of one or both adjusting screws 18.1, 18.2 and 18.3 can be the angle of the format label to Sieve level can be set (swivel angle 24). In addition to this adjustment option, the Adjusting screw 19 the distance of the format label 9 from sieve 10 below it can be adjusted (Distance adjustment 25). That way it is possible with the illustrated embodiment Gap 14 between format label 9 and sieve 10 in adjust in any way, whereby by the Angle adjustment also different gap heights 14 over the length of the format label can. Furthermore, 16.1 and 16.2 the bend of the format label in Machine direction set in the desired way become. The section A-A of Figure 4 is in Figure 5, using the same reference numerals, shown.

Thus, with the embodiment shown, one format label according to the invention compared to the stand technology a significant reduction in the edge waves reached at the beginning of the sheet formation system and thus produces an overall improved paper quality become.

Reference list

1

Headbox

2nd

bottom lip

3rd

cover

4th

Fabric suspension layer

5

Secondary flow

6

Pressure pulse at the jet impact point

7

dried fabric area

8th

wet area

9

Format label

9.1, 9.2

Segments

9.3, 9.4

boom

10th

Sieve

11

Sieve table

12th

Breast roll

14

gap

15

Side wall

16.1, 16.2

Adjustment rods

17th

line

18.1, 18.2, 18.3

Adjusting screws for Angle adjustment

19th

Adjusting screw for Distance adjustment

20th

Adjustment device

21

"released" pressure pulse

22

reflected pressure pulse

23

poetry

24th

Swivel angle

25th

Distance adjustment

26

Weakening area

Claims (11)

Sheet forming system of a Fourdrinier paper or Fourdrinier cardboard machine with a headbox (1), at least one peripheral sieve (10) and at least two format plates (9), each in the edge area of the sieve (10), the headbox (1) passing a machine-wide stock suspension jet via a nozzle generated and placed between the format plates (9) on a sieve (10),
characterized in that
the format plates (9) are designed and / or fastened in such a way that the clear distance between the format plates and the center line of the sieve can be adjusted at least over a substantial part of their length in the machine direction. Sheet formation system according to the preamble of claim 1 or according to claim 1, characterized in that at least one of the format plates (9) has means (18.1, 18.2, 18.3) which allow an angular adjustment about an axis parallel to the transverse direction of the machine. Sheet formation system according to the preamble of claim 1 or according to one of claims 1-2, characterized in that at least one of the format plates (9) has means (19) which allow a distance adjustment, preferably parallel, to the screen running underneath. Sheet formation system according to the preamble of claim 1 or according to one of claims 1-3, characterized in that the format plates (9) are elastic at least in sections in the machine direction. Sheet formation system according to the preamble of claim 1 or according to one of claims 1-4, characterized in that the format plates (9) have at least one joint, the axis of which is substantially perpendicular to the screen plane. Sheet formation system according to one of Claims 1-5, characterized in that at least one device for deforming (16.1, 16.2, 9.3, 9.4) the format labels (9) is provided on the format labels (9) at least in the machine direction. Sheet forming system according to claim 6, characterized in that at least one of the devices for deforming (16.1, 16.2, 9.3, 9.4) the tensile plates exerts a tensile and / or compressive force with at least one directional component transverse to the machine direction. Sheet formation system according to one of claims 6-7, characterized in that at least one of the devices for deforming (16.1, 16.2, 9.3, 9.4) acts on a lever arm arranged on the side of the format label and a tensile and / or compressive force with at least one directional component in the machine direction. Method for reducing edge waves in a sheet formation system of a Fourdrinier paper or Fourdrinier cardboard machine in the area of the material suspension application to a rotating screen, in which a mechanical side limitation is used to limit the edge of the sheet which forms, characterized in that in the edge area of the sheet formation the available for the stock suspension standing area is changed in the machine direction. Method according to the preamble of claim 9 or according to claim 9, characterized in that the distance of the format label (9) from the screen surface is set such that a substantial part of the transverse impulses occurring through the gap (14) between the screen (10) and format label (9) can escape. Method according to one of claims 9-10, characterized in that the broadening of the area available for the stock suspension in the machine direction, essentially in accordance with the rules of the continuity equation for incompressible liquids, is increased in accordance with the changing flow rate by the layer height of the Keep material suspension constant in the edge area.

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