FI81849B - Headbox in a paper machine containing a mixing device for the pulp suspension stream - Google Patents

Description

81 849 1 Paper machine headbox with pulp suspension flow mixer

Insulating sheet in a paper machine with a blending body for mass suspensions 5

The invention relates to a stern-10 box for a paper machine, in particular a fine paper machine, with a pulp suspension flow mixer.

Fine papers aim for essentially the same tensile strength in both the machine direction and the cross direction, i.e. the tensile strength ratio of the fine paper should be close to 1. The implementation of this has slowed down the application of some of the inherent headbox and wire section combinations to fine paper machines.

The tensile strength of the paper is strongly influenced by the fiber orientation of the pulp suspension. Fiber orientation refers to the distribution of the longitudinal directions of the fibers in the pulp suspension and the paper fiber network, respectively. With planar wire and hybrid formers, it is possible to adjust the fiber orientation by the speed differences between the pulp suspension jet and the wire. In Kitaformer solutions, however, this does not result in a so-called the combing effect on the pulp suspension, because the wires meeting in the forming ladder kind of freeze the pulp layer in the state of fiber orientation in which it was when it discharged from the lip opening of the headboard.

It is an object of the present invention to provide a device which can influence the tensile strength ratio of paper, in particular fine paper. In particular, the aim is to provide a concept that brings the tensile strength ratio of paper close to one (1).

It is a further object of the invention to reduce the cross-stripe of the paper to be produced.

In order to achieve the above and later objects, a paper machine headbox according to the invention with a pulp suspension flow mixer «mainly characterized» is characterized in that the headbox flow mixer consists of a headbox mouthpiece (s) profiling 5 on the outlet side of the flow, and that the profiling of the mixing plate (s) causes transverse flows to the pulp suspension flow.

In addition, other advantageous features of the invention are set out in claims 2-10.

10

The pulp suspension flow mixer of the paper machine headbox according to the invention causes the fibers to turn more transversely, whereby the tensile strength ratio of the paper decreases. In addition, the flow mixer according to the invention achieves a reduction in the cross streak of the paper.

In the following, the invention will be described in detail with reference to some preferred embodiments of the invention shown in the figures of the accompanying drawing, to the details of which the invention is not narrowly limited.

Figure 1 shows a machine direction vertical section of a headbox structure, in connection with which it is advantageous to apply a pulp suspension flow mixer according to the invention.

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Fig. 2 schematically shows the lip channel part of the headbox according to Fig. 1 provided with a flow mixer according to the invention.

Figure 3 schematically shows an application example of a flow mixer according to the invention.

Figure 4 schematically shows another embodiment of a flow mixer according to the invention.

Figures 5A-5B schematically show a possibility for connecting a flow mixer according to the invention to a synchronous tube with a turbulence generator.

Fig. 3 81849 1 Figs. 6A-6B schematically show another solution for setting a flow mixer according to the invention with the tubes of a synchronous turbulence generator.

The headbox structure shown in Fig. 1 is mainly known from the prior art, and in the following its structure will be described as a background of the invention. The headbox pulp suspension jet J is fed to a forming wire 11 passing over the breast roll 10. The headbox comprises a base structure 12 with a lower frame beam 13. Attached to the front wall of the beam 13 is a lower lip beam 14 24 is bounded by an upper lip wall 14b associated with protective structures 28. Through the lip opening 25, the pulp suspension jet J is fed to the wire 11 or to the gap between the wires. The lip opening 25 is limited and adjusted by the upper lip-15 plate 26.

- - The pulp suspension is introduced into the headbox by means of a transverse manifold 15 which is divided into a plurality of streams machine direction of the distribution pipes 16 the pulp suspension distribution tubes 16 will equalizing chamber 17, which on the output side 20 has a channel 18 which opens above the equalizing chamber. The equalization chamber has an air space V, which acts as a damper for pressure fluctuations. In connection with the channel 18 there is a dam 18a, followed by an overflow 19a. The dam 18a sets the height C of the pulp suspension.

After the equalization chamber 17, a turbulence generator 20 follows, first in the flow direction, a perforated plate 21 with three overlapping rows of flow holes 21a. Each hole 21a opens into the turbulence tube 22 of the turbulence generator 20, which begins coaxially with its relay 21a. discharged from the turbulence generator 20 flows from the outlet side 23 of the lip 30, the channel 24, which continues to flow in the direction of the arrow F the slice opening 25.

In the embodiment of the flow mixer according to the invention shown in Figure 2, the flow mixer is located in the headbox lip channel 24. The mixer consists of two mixing plates 30a, 35 30b attached to the lower lip wall 14a and the upper lip wall 14b of the lip channel 24, respectively. Mixing plates 30a, 30b are located in a slice channel of the turbulence tubes in the turbulence generator 22 slots «81,849 the immediate vicinity of one side. The operation of the mixer of the mass suspension flow F of the headbox according to the invention is based on the phenomenon that the corrugation in the lip surfaces 14a, 14b causes differences in the transverse velocity profile of the raw suspension flow F.

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In the application example shown in Fig. 2, the mixing plate 30a, 30b according to the invention is fixed to the lower lip wall 14a and the upper lip wall 14b, respectively. It is also possible to attach the mixing plate 30a, 30b only to one of the two lip walls 14a, 14b, most preferably to the upper lip wall wall 14b ·

Figure 3 shows a mixing plate 30a, 30b forming a headbox mass suspension flow mixer according to the invention. A profiling 34 is formed in the mixing plate 30a, 30b at the edge of the plate 30a, 30b on the outlet side of the flow 15F. The profiling 34 is saw-shaped and the shape of the profiling 34 is corrugated in a plane perpendicular to the plane parallel to the mass flow. Profiling 34 is formed by removing a portion of the material thickness of the sheet. When the height H of the mixing plate 30a, 30b is 0-10 mm, preferably 2-4 mm, the material has been removed from the edge of the plate 34 for profiling 34 by a maximum height h, which height h is 0-10 mm, preferably 0-2 mm. The depth d of the profiling 34 in the direction of the flow level is 0-200 mm, preferably 20-50 mm. The profiling 34 is also intermittent in the cross-machine direction and the length 1 of the section is 5-100 mm, preferably 15-50 mm.

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The sawtooth-shaped profiling 34 of the mixing plate 30a, 30b consists in a way of alternating substantially triangular non-effluent planar region 35 and intermediate flow-extending recesses 36 between them.

As the pulp suspension flow F enters along the surface of the mixing plate 30a, 30b, at the profiling 34, transverse flows FN> are formed which extend from the plane area 35 of the material to be removed to the triangular recesses 36. Thus a partial inversion of the fiber orientation is achieved.

In the application example of the mixing plate 30a, 30b shown in Fig. 4, the profiling of the plate 34 is achieved by removing the entire thickness H of the plate 30a, 30b. The length of the section of profiling 34 is 5-100 mm in the transverse direction, preferably 15-50 mm. Thus, a tooth-like profiling 34 is provided with an alternating level area 35 of non-removable material and a recess 36. The shape of the profiling 34 is corrugated in a plane parallel to the mass flow. The depth of profiling in the direction of the flow level is 0-10 mm, preferably 0-2 mm.

JO The shape of the profiling 34 is not limited to the examples given above but can be of other shapes, e.g. rectangular. The prerequisite for the form of profiling 34 is to achieve the desired flow mixing. The ratio of the length 1; 19 of the profiling period 34 to the depth d; d £ of the profiling 34 is 0-1000, preferably 0-10.

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Mass flow mixing will not work as desired if the flow mixing is not synchronized with the turbogenerator tubes 22. Figures 5A-5B show a solution in which the flow between the mixing plate 30a, 30b and the tubes 22 of the turbulence generator is obtained synchronously. The tip of the triangular recesses 36 in the profiling 34 of the mixing plate 30a, 30b is arranged in the middle of the tube 22 of the turbulence generator.

In the solution shown in Figures 6A-6B, in order to achieve synchronism between the turbulence generator tube 22 and the flow mixer according to the invention, the tips 35 of the triangular non-removable regions 35 of the profiling plate 30a, 30b are arranged in the center of the turbulence generator tube 22.

The invention has been described above with reference only to some of its preferred application examples. However, this is in no way intended to limit the invention to these examples only, but many modifications and variations are possible within the scope of the inventive idea defined by the following claims.

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Claims (10)

1. A paper machine inlet carriage, in particular a fine paper machine, in which an inlet carriage has a pulp suspension stream mixing element (F), characterized in that the mixing means for the stream (F) of the inlet pipe consists of a mixing board (30b, 30a). to the upper lip wall (14b) and / or the lower lip wall (14a) of the lip channel (24) / channels of the inlet carriage, in which there is a disc transverse profile (34) in the transverse direction on the output side of the stream (F) , and with the profiling (34) of the mixing disc (s) (30a, 30b), transverse currents (FN) are obtained in the pulp suspension stream (F). 2. An inlet carriage according to claim 1, characterized in that the mixing disc (s) (30a, 30b) of the mixing means for the current in the inlet carriage are placed (e) in the beginning portion of the lip passage (24) in the immediate vicinity of the exit side of the tubes (22). the turbulence generator (20). 3. An inlet carriage according to claim 1 or 2, characterized in that in the mixing disc (30a, 30b) of the mixing means for the flow of the inlet carriage there are alternating substantially triangular planar areas (35) for unpainted material and of recesses (36) therebetween. extending in the direction of flow, formed a saw-shaped or corresponding profiling (34) (Figure 3). 4. An inlet carriage according to any one of claims 1-3, characterized in that the shape of the profiling (34) of the mixing means for the current in the inlet carriage is road-shaped in a plane perpendicular to the plane in accordance with the direction of the mass flow. An inlet carriage according to any one of claims 1-4, characterized in that the sawtooth-shaped profiling (34) of the mixing disc of the mixing means for the current in the inlet carriage is formed by removing material from the edge of the mixing disc (30a, 30b) over a height (h ) which is 0-10 mm, most preferably 0-2 mm. 9 81849 6. Inlet housing according to claim 1 or 2, characterized in that a tooth-shaped profiling (34) (Fig. 4) is formed in the mixing plate (30a, 30b) of the mixing means for the current in the inlet housing. An inlet drawer according to any one of claims 1-3, characterized in that the shape of the profiling (34) of the mixing means for the stream in the inlet drawer is wall-shaped in a tab directed according to the mass flow (Figure 4). An inlet tray according to any one of claims 1-7, characterized in that the profiling (34) of the mixing plate (s) (30a, 30b) of the mixing means for the flow of the inlet tray is placed in a transverse direction synchronously with the tubes (22) of the turbulence generator. (20) and equally distributed. 9. Inlet according to any one of claims 1-7, characterized in that the ratio between the length (1; 12) of the period of profiling (34) of the mixing plate (30a, 30b) of the mixing means and the depth (d; d2) of the profiling ( 34) in the direction of the flow piano is 0-1000, most preferably 0-10. 10. Inlet according to any one of claims 1-9, characterized in that the height (H) of the mixing plate (30a, 30b) of the mixing means for the flow in the inlet in a perpendicular direction in relation to the direction plane of the flow is 0-10. mm, most preferably 2-4 mm. :: 30