FI120654B - Method in connection with an outlet box of a paper or cardboard machine and slats in an outlet box of a paper or cardboard machine - Google Patents

Description

Method in connection with a headbox of a paper or board machine and a lamella of a headbox of a paper or board machine 5

The invention relates to a method according to the preamble of claim 1 in connection with a headbox of a paper or board machine.

The invention also relates to a headbox section of a paper or board machine according to the preamble of claim 6.

As is known in the art, lamellae, or lamellae, are used in the lip ducts of the headboxes to increase the tensile strength ratio of the paper or board web due to increased turbulence yield. The lamellae also reduce the scale of the resulting turbulence, since the lamellae provide: a small duct height because the lip duct is divided into layers vertically; increased boundary layer turbulence as the flat Uit increases the wall area; and a thin leaving end because a small area change over the lamella tip and 20 small vortices caused by the lamella leaving end is obtained; and further, the lamellae prevent the mixing of currents from different rows of the turbulence generator. The blades used in headbox sizes vibrate somewhat in use as a result of headbox flow under certain conditions. One problem with lamella technology is that the vibration of the lamina forms a standing wave at the tip of the lamina, which causes a very regular transverse or CD locked aging, which occurs in the finished structure of the paper and board web, e.g. The intensity of this phenomenon depends on the structure of the fins and the driving parameters. The old / striped structure in the web switches directly to the transverse periodicity observed in water measurements in the mean velocity profile. This, in turn, has been shown to be due to the flow structure interaction where turbulence and periodic vortex release from the lamella ejection edge generate, under appropriate conditions, an excitation that causes the structure to oscillate. As a result of the resulting oscillation mode, the flow separation is further enhanced in certain transverse positions and attenuated in others, resulting in a secondary flow structure after 5 lamellae forming old fibers in the flow.

This problem has not been satisfactorily solved by prior art solutions, but has had to compromise between the old-fashioned nature of the final product and some other feature, which has not been able to improve as much as possible in principle. Efforts have been made to solve the problem, for example, by making structural changes to the lamellae, for example by moving to a more rigid wedge-like structure. In addition, special materials such as titanium and carbon fiber have been introduced. However, this phenomenon has not been completely eliminated and, among other things, carbon fiber lamellae have been found to oscillate at high speeds, causing problems with fiber quality.

In addition, efforts have been made to solve the problem by using passive or active attenuation. One known arrangement for implementing passive damping is the lamination of the visco-elastic film on the surface of the lamella, which has been shown by measurements to strongly reduce the secondary flow structure in the van. However, one disadvantage of this arrangement is that the damping material is then exposed to the process conditions, whereby additional requirements are applied to the coating used. In turn, tracking active damping along the lamella is rather complicated and expensive.

The cause of the problem, i.e., the resonance of the lamellae, is also influenced not only by the lamella geometry and the material of the lamellae, but also by the flow space around the lamellae. However, this problem cannot be solved either, because in practice, changing the current state so much that the resonance of the lamella would be lost is limited, since at the same time the properties of the end product would change too much.

With respect to the prior art, reference may be made to WO Application Publication 03/062527, which discloses an arrangement for controlling a mass flow through a film matrix in connection with a paper machine headbox by supplying a film to the matrix with a voltage / amplitude controlled signal. Through the membrane matrix, turbulence or oscillation is obtained in the mass flow, which oscillation suppresses the mass flow pressure variation. This known arrangement is problematic in that the film matrix is worn by the mass suspension flow and the arrangement is complicated and expensive.

Reference may also be made, in the prior art, to DE-A-10249820 15, which discloses an arrangement for use with a headbox of a paper or board machine in which at least one geometry change is provided to influence the fiber orientation of the pulp suspension. However, the disadvantage of this known arrangement is that this does not prevent the lamella tip from vibrating.

20

The object of the invention is to provide a method in connection with a headbox of a paper or board machine and a headbox lamella in which the problems associated with the vibration of the lamina are eliminated or at least minimized.

In order to achieve the foregoing and further objects, the method according to the invention is essentially characterized by what is stated in the characterizing part of claim 1.

The headbox lamella of the invention, in turn, is essentially characterized by what is set forth in the characterizing part of claim 6.

4

According to the invention, in the headbox of a paper or board machine, the vibration of the lamella and the resulting ripple are damped by providing passive damping with the lamella, using a layer of media inside the lamella to dampen the vibration of the tip. In accordance with the invention, the structure of the lamella 5 according to the preferred embodiment is implemented with a vibration energy absorbing portion and, in accordance with a further advantageous feature, also another structure preventing the harmful vibration mode which is laminated or otherwise mounted inside the lamella structure.

10

According to a preferred embodiment of the invention, a vibration energy absorbing medium layer, preferably a visco-elastic layer, is laminated inside the lamella. The damping material used is, for example, Kevlar, which is suitable for laminating inside a lamella and has damping properties and can be laminated inside a carbon fiber structure. In addition, for example, heat-resistant rubber can be used. Preferably, furthermore, the damping material is made from the damping material of the lamella core to extend over the entire length of the lamella to the tip of the lamella.

According to a further advantageous feature of the invention, the structure of the lamella tip is modified such that a standing wave near the tip is not produced or at least minimized, and the harmful vibration mode does not occur despite the potential for excitation from the flow. Thus, the material of the cushion is transversely inhomogeneous, whereby the material properties, for example stiffness, are cured to be inhomogeneous. In this case, the damping material is laminated transversely to form an inhomogeneous structure within the structure, for example by laminating separate inserts or inserts to the lamella tip. The structure is determined by the material used and the vibration mode generated in the homogeneous cone.

30 5

The invention can be applied to various types of lamella / wedge structures, for example, to hinged and fixedly attached lamella structures. Preferably, the lamella / wedge has a wedge-tapered shape in the flow direction.

The invention will now be described with reference to some preferred embodiments of the invention shown in the figures of the accompanying drawings, in which, however, the invention is not intended to be narrowly limited.

Figure 1 schematically illustrates a headbox structure in which the invention is applicable.

Figure 2 schematically illustrates an embodiment of the invention.

Figure 3 schematically illustrates another embodiment of the invention.

15

Fig. 1 schematically illustrates a headbox 10 comprising a mass distributor stop 11, followed by a pulley 12 in a downstream direction, comprising flow tubes from which flow is directed to the intermediate chamber 13. The flow from the intermediate chamber 13 is further directed to the turbulence generator 14 and (not shown). According to Figure 1, the mass flow from the manifold supports 11 is led through the inlet plate 11A to the bellows 12. After the Si inlet plate 1Aa there is a manifold 19. Both the inlet plate 11A and the manifold 19 comprise vertical and horizontal channels 22. The channels 22 of the manifold 19 A dilution stream, preferably of pure or fibrous water, is introduced into the pulp stream 25 from the manifold fluid manifolds 20 through channel 24 of the inlet plate 1A to valves 25 at various width positions of the paper machine / board machine headbox. A dilution flow from each valve 25 is diverted to a passage 22 in the plate 19. The mass flow is further directed 30 to the intermediate chamber 13. The mass flow from the intermediate chamber 13 is directed to the turbulence generator 14 and further to the headbox lip channel 15. 15 widths. According to the invention, the lamellas 16 comprise a vibration energy absorbing medium layer 30 imaged within the lamina 16, preferably extending along the entire flow direction of the lamina 16 to the tip of the lamina, thereby absorbing the vibration energy of the structure and thereby reducing the vibration of the structure.

Fig. 2 illustrates an embodiment of the invention showing a lamella 16 located in the lip passageway 15 of the headbox 10, for example arranged by laminating according to the invention to dampen the vibrations of the lamina 16 inside the lamina 16, e.g. layer. The media layer 30 extends substantially along the flow length of the lamina 16, preferably to the entire length up to the tip of the lamina 16. The media layer 30 is disposed beneath both the upper surface 31 and the lower surface 32 of the lamella 16 and is made of, for example, Kevlar or heat-resistant rubber 15.

The embodiment of the invention shown in Figure 3 corresponds substantially to the above and the like reference numerals denote corresponding parts. In the embodiment of the invention illustrated in this figure, the material of the media layer 30 is non-homogeneous in the cross-flow direction, whereby another material, for example a rigid or resilient material 35, is preferably laminated to the inside of the lamella 16. Preferably, the media layer is located closer to the lamella tip than the hinge portion. The fluid layer 30 is of a non-homogeneous cross-sectional structure and is implemented by inserting into the lamella 25 another material whose vibrationally significant material properties, such as stiffness or elasticity, differ significantly from those of the lamellar material. In the example shown in Fig. 3, inserts 35, i.e. pieces of other material, are placed in the media layer so as to prevent the creation of a harmful vibration mode.

30 7

Although the invention has been described above in relation to a hinged lamella / wedge, the invention is also applicable to various types of lamella structures, for example also to fixedly attached lamella structures. In addition, paper or board machine also refers to tissue machines.

5

The invention has been described above with reference only to some preferred embodiments thereof, the details of which, however, are not to be construed as being limited in any way.

10

Claims (10)

A method in connection with an inlet carriage of a paper or cardboard machine, in which method at least one slat (16) is used in a lip channel (15) of the inlet carriage (10) to create / maintain turbulence in the pulp suspension, in which method vibrations in the slat (16) and a resultant road formation are attenuated by a medium layer (30) disposed within the slat (16) which absorbs vibrational energy, characterized in that the vibrations in the slat (16) are attenuated in the method by a medium layer (30) which is non-homogeneous to the transverse structure in such a way that within the lamella has been placed as inserts (35) another material whose material properties with respect to vibration differ significantly from the properties of the lamellar material. 2. A method according to claim 1, characterized in that the vibrations in the lamella (16) are attenuated in the method with a medium layer (30) of a viscoelastic film in the lamella (16). Method according to claim 1 or 2, characterized in that the vibrations in the lamella (16) are attenuated in the method by a medium layer (30) extending substantially over the entire length of the lamella. Method according to any of the preceding claims, characterized in that the vibrations in the lamella (16) are attenuated in the process with a viscoelastic film (30) laminated on an inner upper and lower surface of the lamella. 25 Process according to any of the preceding claims, characterized in that the material of the medium layer (30) used in the process is kevlar or thermoset rubber. 6. A slat in an inlet carriage of a paper or cardboard machine, said slat being placed in a lip channel (15) of the inlet carriage (10), in which the slat (16) is provided with an inner medium layer (30) for damping vibrations in the slat ( 16) and as a result of these road formation, characterized in that the medium layer (30) is of a non-homogeneous material in the transverse direction in such a way that another inside the lamella is placed as inserts (35), which with respect to vibration 5 significant material properties differ significantly from the properties of the slat material. 7. A lamella according to claim 6, characterized in that the medium layer (30) is made of a viscoelastic film. 10 8. A slab according to claim 6 or 7, characterized in that the medium layer (30) extends over the flow-directed length of the slab all the way to the tip of the slab (16). 9. Slat according to any of claims 6-8, characterized in that the medium layer (30) is located on the inner Upper and lower surfaces of the slat (16). 10. A lamella according to any one of claims 6-9, characterized in that the medium layer (30) is of kevlar or heat-resistant rubber. 20