JPS6256279B2 - - Google Patents

Description

[Detailed description of the invention]

FIG. 1 is a sectional view showing an example of a conventional paper machine headbox. In the figure, the paper stock liquid passes through a rectangular header 1 that tapers in the width direction of the paper machine (perpendicular to the plane of the paper), changes direction by 90 degrees, branches into tapered tubes 2 that are lined up in the width direction, and then branches into a top plate 3. and enters a widthwise passageway 5 defined by a bottom plate 4. This paper stock liquid is given acceleration and deceleration as it passes through the flow path 5, and the fiber flocs in the paper stock liquid apply a stretching force in the direction of the flow in the acceleration region, and in a direction perpendicular to the flow in the deceleration region. The fibers are fragmented under the force of pushing and stretching, and after being uniformly dispersed in the paper raw material liquid, the fibers are ejected from the opening at the tip of the slice lip 6. Therefore, paper made by dehydrating this with a wire has good texture and strong paper strength. However, the conventional headbox shown in FIG. 1 has the following drawbacks. That is, the channel walls of the top plate 3 and the bottom plate 4, which are provided to apply acceleration and deceleration to the paper raw material liquid to perform fiber dispersion, have the disadvantage that the processing surface increases with each acceleration and deceleration, which increases the manufacturing cost. . In order to eliminate the above-mentioned conventional drawbacks, the present invention aims to reduce the manufacturing cost by improving the shape of the acceleration and deceleration flow paths. Both the upper and lower walls have planes that approach or separate from the other wall surface, but the upper and lower walls do not approach or separate at the same time at a certain position in the flow direction. When changing the cross section from increasing to decreasing or from decreasing to increasing, it is possible to arbitrarily bend the upper wall or the lower wall, and by selecting this, the average flow path It is an object of the present invention to provide a headbox for a paper machine which allows the paper machine to move in any direction. Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a paper machine headbox showing an embodiment of the present invention. In Fig. 2, the paper stock liquid is fed into a rectangular header 7 that tapers in the width direction.
The hole 9 changes direction by 90 degrees and branches into a plurality of holes 9 lined up in the width direction of the perforated plate 8. A slit channel 12 connected in the width direction formed by a portion 10a of the top plate 10 and a portion 11a of the bottom plate 11 is directly connected to the outlet of the hole 9, giving a large throttling effect to the flow. In addition to improving the distribution property in the width direction, when the paper stock liquid exits the hole 9 and enters the slit flow path 12, it becomes a flow that rapidly expands in the width direction, and flows into the flow path 13 divided by the top plate 10 and the bottom plate 11. enter. The paper stock liquid advances while repeatedly accelerating and decelerating as it passes through the flow path 13, and is ejected from the opening at the tip of the slice lip 14. Now, on the surfaces of the upper and lower walls of the flow path 13, a plurality of planes 10b and 11b extending in the width direction are inclined to each other and are connected in the flow direction of the paper stock liquid. The part of the lower wall where the upper wall faces the plane 10b has two planes 11b and 11c facing each other that approach or separate from the upper wall, and the lower wall faces the plane 11b. The upper wall portion has two planes 10b and 10c that move toward and away from the lower wall.
are arranged in series and facing each other, so that the cross-sectional area of the flow path 13, which is composed of the upper wall and the lower wall, can repeatedly increase and decrease. FIG. 3 is a sectional view of another type of paper machine headbox in accordance with an embodiment of the present invention. This type of headbox is called a secondary headbox, and is a headbox for further spouting paper stock liquid onto the paper stock liquid that is spouted from the primary headbox and is being dewatered on the wire. It is. In the figure, droplets of paper stock liquid tend to adhere to the lower surface of the secondary head box installed on the wire, and if this adhered material gradually accumulates and falls onto the wire again, problems will occur. Therefore, in such a secondary head box, it is preferable to separate the rectangular header 15 from the wire 17 as shown in FIG. In this case, the average direction of flow can also be bent by 90 degrees, as in the flow path 16 shown in FIG. In this manner, in the flow path of the present invention, the average direction of flow can be made into an arbitrary curve. FIG. 4 is a sectional view of a paper machine headbox showing another embodiment of the present invention. In the figure, perforated plate 1
At the exit portions of multiple rows of holes 19 lined up in the width direction of 8,
A portion 20a of the top plate 20 and a portion 2 of the current suppressing element 22
A slit flow path 23 connected in the width direction formed by 2a is directly connected, giving a large throttling effect to the flow and improving distribution in the width direction.
When the paper stock liquid exits the hole 19 and enters the slit channel 23, it becomes a flow that rapidly expands in the width direction, and enters the channel 24 defined by the top plate 20 and the flow suppressing element 22. The flow path 25 is also formed similarly to the flow path 24. The paper stock liquid advances while repeatedly accelerating and decelerating as it passes through the channels 24 and 25, and then merges in the channel 26, and then repeats acceleration and deceleration as it advances toward the tip of the slice lip 27. It flows towards the enemy and is ejected from the opening. The current suppressing element 22 is a protrusion 2 provided on the perforated plate 18.
8 from the direction perpendicular to the page and can be freely attached and detached. As the paper stock liquid flows through the headbox, the flow restraining elements 22 are held apart from each other by the hydrodynamic effects of the flow. As described above, the flow path of the present invention is as shown in FIG.
It can be formed by the wall surfaces of the top plate 20 and the current restraining element 22. Furthermore, it is also possible to place a plurality of current suppressing elements in a portion defined by the top plate 20 and the bottom plate 21, and form the flow path of the present invention with the wall surfaces of the current suppressing elements and other current suppressing elements. In the present invention, as in the embodiments, the local direction of movement of the flow path composed of the upper wall and the lower wall is upward or downward, but generally toward the opening at the tip of the slice lip. Since the paper stock liquid flows while being accelerated and decelerated, the fibers in the paper stock liquid are dispersed by the above action. Therefore, paper made by dehydrating this with a wire has good texture and strong paper strength. In the conventional flow path that accelerates and decelerates the paper stock liquid, the upper wall and the lower wall are simultaneously approached and separated at a certain position in the flow direction, as shown in flow path 5 in Fig. 1, and the flow path is interrupted. The area was decreased or increased. In the flow path of the present invention, as shown in the flow path 13 in the embodiment of FIG. 2, at a certain position in the flow direction,
The cross-sectional area of the flow path is decreased or increased by moving either the upper wall or the lower wall toward or away from the other plane. Therefore, according to the present invention, the number of planes to be machined on the surfaces of the upper and lower walls can be halved compared to conventional ones, and manufacturing costs can be reduced. In the conventional flow path, it was necessary to precisely machine the dimensions and heights of the unevenness in the flow direction of the upper and lower walls, and to assemble the relative positions of the upper and lower walls in the flow direction with high precision. In the flow path of the present invention, even if there is some error in the dimensions of the unevenness of the upper and lower walls in the flow direction, it has little effect on the shape of the flow path, so the processing accuracy and assembly accuracy of the upper and lower walls can be improved. It is not too strict, and production costs can be reduced from this point of view as well. Generally, head boxes are operated at a high concentration where the fibers in the water flow while interfering with each other, so in a turbulent flow, the fibers move in groups depending on the size of the turbulence. ing. In addition, if a clump of fibers that are tightly entangled due to collisions between fibers or eddies has already been formed, disturbances in the flow of water within the clump will be suppressed.
Therefore, it can be said that the size of the fiber mass represents the amount of turbulence in the flow. From this, even if it is possible to obtain a flow with good fiber dispersion, if there is turbulence in the flow, the turbulence may cause the fibers to collide with each other and form lumps again, or The vortices cause the fibers to become tangled and disrupt fiber dispersion. In order to avoid such defects, the present invention places limits on changes in the cross-sectional shape of the flow path in order to prevent turbulence from occurring in the flow. That is, in order to prevent the flow from separating due to a change in the cross-sectional area of the flow path, the deceleration region is set as shown in Table 1 below.

【table】

[Table] As described in detail above, according to the present invention, by changing the cross section of the flow restriction channel, the flow of the paper stock liquid flowing therethrough is accelerated and decelerated. When the flocs in the paper stock liquid are in the acceleration region, the upstream flow velocity is low and the downstream flow velocity is high, so the flocs are torn off and dispersed. In the deceleration region, the flow velocity is reversed, so the flocs are stretched in a direction perpendicular to the average direction of travel, that is, in the width direction and the thickness direction. By repeating this process, the floc becomes finely divided and the fibers are uniformly dispersed in the paper raw material liquid. In addition, by changing the cross-sectional area of the flow path as described above, the flow of paper stock liquid flowing through this path is accelerated and decelerated, and the flocs in the paper stock liquid receive force from the flow of water and accelerate and decelerate. However, since the fiber density in the center of the flock is high and the density is low in the peripheral area, the force that the fibers receive from the water flow differs depending on the area. Because the fibers overlap in the center, the force received from water during acceleration and deceleration is weak.
Large in the periphery. Therefore, when the floc is in the acceleration region, the periphery expands in the direction of flow, while when it is in the deceleration region, the periphery expands in the upstream direction of the flow. By repeating this process, the flocs will be dispersed from the periphery, and the fibers will be uniformly dispersed in the paper stock liquid. Even in the center of the flock, if there is a density difference or a weak bond, division is performed from there for the reasons mentioned above. During acceleration and deceleration, the fibers are oriented in the average traveling direction, but in the deceleration region, the fibers are pushed further backwards, so their directions become scattered. Therefore, the dispersed fibers have no direction, and the undispersed flocs also have different orientations unless they are spherical due to fluid resistance. Therefore, a dispersion force acting at a different angle will act on the undispersed flocs.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a conventional paper machine headbox, and FIGS. 2, 3, and 4 are side sectional views of a paper machine headbox showing different embodiments of the present invention. Explanation of main parts of the figure, 10, 20...Top plate, 1
1, 21... Bottom plate, 13, 26... Channel, 10b, 1
1b...plane, 10b, 10c...2 plane, 11b,
11c...2 planes.

Claims (1)

[Claims] 1. A plurality of flat surfaces extending in the width direction are arranged in series in the flow direction with an inclination to each other, and the upper wall and the lower wall face each other to form a long and narrow channel, and the lower wall faces the flat part. The part of the wall has a plane that approaches the lower wall and a plane that separates it from the lower wall, and conversely, the part of the lower wall where the upper wall faces the flat part has a plane that approaches the upper wall and is separated from it. A headbox for a paper machine, characterized in that the cross-sectional area of a long and narrow channel formed by an upper wall and a lower wall repeatedly increases and decreases by connecting flat surfaces.