JPS6256278B2 - - Google Patents

Description

[Detailed Description of the Invention] A conventional paper machine headbox is shown in Fig. 1. In order to distribute the flow rate in the width direction, this headbox provided resistance to the flow by means of a tapered pipe 1 and a perforated plate 2. However, in the flow that exits the hole in the tapered pipe or perforated plate, turbulence and a large number of vortices 3 and 4 are created in the flow due to agitation due to the difference in flow velocity. When turbulence or eddies are created in the flow, flocs are generated for reasons explained later.

The flow suppressing element 5 in the slicing chamber has the feature of attenuating the turbulence at the outlet of the perforated plate 2 and ejecting a stable jet in the width direction, but the dispersion of fibers is not sufficient and paper with flocs is produced. It was hot. Therefore, in order to improve the dispersion of the fibers in the raw material liquid, it was necessary to lower the fiber concentration to a level (usually 0.3 to 0.8%) that would not cause the fibers to form flocs even if turbulence was created in the flow.

In addition, the opening degree of the slice lip 6 is usually 10 mm to 20 mm.
mm, but in order to uniformly adjust the opening degree in the width direction, and to adjust the basis weight and thickness of the paper in the width direction, a slice lip 6 is placed at the spout part and the width is adjusted in the width direction. He was making fine adjustments to the opening of the slice lip by moving the adjustment sticks lined up. However, because the flow was suddenly accelerated at the slice lip 6, turbulence occurred in the flow in the portion 7 of the flow path where the top plate and the slice lip were in contact, which caused floes to be generated and jet turbulence to occur. was.

In conventional paper machine headboxes, it was not possible to increase the concentration of the raw material liquid because increasing the concentration of the raw material liquid would result in poor paper texture when viewed through the paper. Furthermore, even if the concentration was low, the fibers were not sufficiently dispersed, and when the paper was looked through, the resulting paper was mottled.

Furthermore, in the past, when the papermaking speed was increased or the thickness of the jet was reduced, striped patterns (streaks) extending in the machine direction became more visible on the surface of the jet, which was a problem in paper manufacturing. On the other hand, when making paper of the same basis weight, increasing the raw material concentration will result in a thinner jet. Therefore, in order to produce paper with a high concentration, it was necessary to obtain a smooth jet without roughening the surface of the jet even if the jet was made thinner, or without the above-mentioned streaks.

When turbulence is created in the flow, vortices are also generated. When a vortex is created in the flow of paper stock liquid, the centrifugal force causes the fibers to move outside the vortex, resulting in a concentration difference, and the fibers also form clumps due to twisting. Disturbing the flow has the effect of destroying the flocs, but the turbulence of the flow also causes the fibers to collide with each other, and the vortices create new flocs, so the concentration cannot be increased. Ta. Furthermore, when stirring is stopped, small disturbances decay quickly, but large disturbances remain, resulting in large flocs. Large disturbances are slow to attenuate, causing jet disturbances and large flocs on the wire.

Conventionally, the mechanism of floc formation described above was not fully understood, and it was thought that it was necessary to cause turbulence to the flow in order to disperse the fibers. To this end, various methods have been used in the past, such as rapidly changing the cross-sectional area of the flow path, rapidly changing the direction of the flow, lining up rods in the flow, adding steps to the wall, making the wall wavy, and adding protrusions to the wall. The flow was disrupted by means of

The present invention was proposed in order to eliminate the above-mentioned conventional drawbacks, and includes a distributor that distributes the flow rate in the width direction without disturbing the flow;
a slicing chamber that increases fiber dispersion by repeatedly accelerating and decelerating the flow without causing disturbance to the flow;
Another object of the present invention is to provide a headbox for a paper machine comprising a slicing lip that can adjust the opening degree of the slicing lip without disturbing the flow.

More specifically, the present invention is characterized in that the largest constriction portion is formed at the joint surface between the slit portions, and the dimension in the flow direction is eliminated (directly connected), thereby eliminating the difference in flow velocity at the downstream slit portion. A slicing chamber with a distributor that creates a trickling flow and eliminates stirring, and a flow path that gradually narrows or widens in a straight line without causing even the slightest disturbance in the flow. There is a low-rigidity neck part between the tip of the slice lip and the attachment part, and by bending that part, the lip opening degree can be adjusted, and the tip can also be bent in the width direction, preventing turbulence in the flow. It is characterized by being composed of a slice lip that does not give any

An embodiment of the present invention will be explained below with reference to the drawings. Fig. 2 shows a head box of a paper machine showing an embodiment of the present invention. First, the distributor section has a slit 8 extending widthwise on the downstream side of the flow.
It is constructed by directly connecting to the upstream side of this slit 8 and arranging drill holes 9 having a diameter b larger than the gap a of the slit 8 at appropriate pitches in the width direction (drill, slit structure).

Next, the slicing chamber is divided by a top plate 10 and a bottom plate 11, and is configured so that the flow path is repeatedly narrowed and widened linearly.

Furthermore, the slice lip 12 has a low-rigidity neck portion 15 in the middle between the tip portion 13 and the attachment portion 14.
Further, the tip portion is designed to be able to bend in the direction perpendicular to the flow in the width direction, so that the joint portion 38 on the liquid contact side of the top portion 10 is flush with the liquid, and the slice lip is fixed.

Next, the operation will be described. At the connection between the drill hole 9 and the slit 8, the flow is greatly accelerated to provide flow resistance (restriction) and macroscopic distribution in the width direction is achieved. Furthermore, in FIG. 3, flows 16 and 17 that are rapidly accelerated just before slit 8 collide with each other when they flow into slit 8, but immediately enter the slit that extends in the width direction, resulting in flows 18 and 19 that spread in the width direction. The flow is rapidly decelerated and merges with the flow from the adjacent drill holes 9' and 9'' to form a film-like flow, resulting in microscopic distribution (uniform velocity in the width direction).

Further, the distributor section may have another embodiment structure shown in FIG. 4. In FIG. 4, a slit 8 is provided on the downstream side of the flow and extends in the width direction, and a slit 22 is directly connected to the upstream plate of this slit 8 and intersects with the slit 8 having a length c larger than the gap a of the slit 8. They are arranged at appropriate pitches in the width direction. The slits and slit structure shown in Fig. 4 have a widthwise flow of 2 at the slit on the downstream side.
3 and 24 spread well and have excellent microscopic distribution performance.

Next, FIG. 5 shows still another embodiment, in which the distributor part has a slit 26 that crosses the slit 25 on the upstream side and extends in the width direction on the downstream side, and the wall surface 27 and the surface of the current suppressing element. 28 or current suppression element 30
It is composed of similar surfaces.

The slicing chamber is partitioned by a top plate 32 and a bottom plate 33 that move toward the slicing lip 31.
Detachable flow suppressing element 3 held by protrusion 34 of 9
0, a plurality of widthwise passages 35 are formed.

The flow path 35 repeatedly becomes gradually narrower and wider in a straight line, and after the three flow paths merge, the flow path 36 gradually becomes narrower and wider in a straight line. repeat. The slicing chamber shown in FIG. 5 has a small head loss even when a large flow rate is passed, and fiber dispersion can be achieved by applying acceleration/deceleration to the flow.

In addition, as another embodiment of the distributor, the slit in the upstream plate can be made by carving out a plate that passes through the width direction, or by stacking a plurality of plates 37 as shown in FIG. A slit 25 can also be formed. Further, the protrusion 34 is connected to the current suppressing element 3.
This is to hold 0. On the other hand, in a drill or slit type distributor, the upstream drill may be a pipe.

Since the present invention is constructed as described in detail above, the distributor performs macroscopic flow distribution in the width direction and then performs agitation as in the conventional method, so that the flow is not disturbed. I can't.

Also, as the flow passes through the distributor, greater accelerations and decelerations are imparted to the flow, thereby improving fiber dispersion for reasons discussed below. Furthermore, a film-like flow is obtained at the outlet of the downstream slit,
There is little turbulence in the flow, and the speed difference in the width direction is also small.

Next, in the slicing chamber, fiber dispersion is enhanced by repeating acceleration and deceleration without disturbing the flow. Since flocs are generated when the flow is disturbed, the flow path is gradually narrowed or widened to prevent the flow from being disturbed.

Furthermore, it is best to avoid peeling that occurs locally and randomly in the widened portion, and the widening angle and expansion ratio (channel size after widening/channel size before widening) are appropriately selected.

The reason why the fibers are dispersed by the acceleration and deceleration is as follows.

That is, by changing the cross section of the flow restriction channel, the flow of 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.

In the acceleration region, the fibers are oriented in the average traveling direction, but in the deceleration region, the fibers are pushed from behind, so the 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.

Furthermore, since the slicing chamber has several stages of through-holes lined up in the width direction, an extremely uniform flow velocity in the width direction can be obtained, and turbulence in the flow can be rapidly attenuated.

On the other hand, the slicing lip also does not disturb the flow, does not destroy the excellent fiber dispersion obtained in the slicing chamber, and accelerates or decelerates the flow at the slicing lip, improving fiber dispersion.

Therefore, according to the present invention, the formation is improved, high-density papermaking is possible, a jet with a smooth surface can be obtained even if the thickness is thin, and a jet with a uniform speed in the width direction can be obtained. can be made smaller.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing an example of a conventional paper machine headbox, Fig. 2 is a side sectional view of a paper machine headbox showing an embodiment of the present invention, and Fig. 3A shows the main parts in Fig. 2. An enlarged view, FIG. 3B is the same front view, FIG. 4A is a side sectional view of the slit portion of a different embodiment from FIG. 3A, FIG. FIG. 6 is a side sectional view of a headbox of a paper machine showing another embodiment of the present invention, and FIG. 6 is a perspective view of a distributor section, which is different from FIG. 5. Explanation of main parts of the figure, 8...Slit, 9...Drill hole of large diameter, 10...Top plate, 11...Bottom plate, 12
...Slice lip, 13...Tip part, 14...Mounting part, 15...Neck part.

Claims (1)

[Claims] 1. A slit that runs through the width direction is arranged on the downstream side, and a distributor is arranged on the upstream side that has a plurality of holes with a diameter larger than the slit gap directly connected, and the flow path is made straight without disturbing the flow. It has a slicing chamber that repeatedly narrows and widens, and a neck part with low bending rigidity in the direction perpendicular to the flow between the tip and the mounting part, and the opening of the lip tip can be adjusted in the width direction. A headbox for a paper machine comprising a slice lip to be adjusted.