JPH07113194B2 - Paper machine and method for improving stock forming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to initial paper forming by a machine that deposits an aqueous slurry, known as paper stock, on a continuously moving paper fabric.

In this type of machine, a stock containing both fibers and other substances, weighing about 0.1% to about 1.5%, is fed from a headbox slice onto a moving textile fabric. When the stock passes through various dewatering elements, the moisture is gradually discharged from the stock through the paper-making fabric, and at the exit of the forming section, the stock finally contains about 2% to 4% by weight of solid substances. . The distribution and orientation of the fibers and other solids in the still fairly moist stock is largely determined at this stage and therefore does not change much in the subsequent papermaking stages. Therefore, the molding of the paper is almost completed at the exit of the molding section.

Generally, the forming section of a conventional paper machine comprises a paper woven fabric supported at the ends of the headbox slices by breast rolls, with a forming plate immediately after this breast roll,
After this forming plate is a series of dewatering devices which are the final part of the forming section. There are various types and arrangements of the dehydrator, but a normal open-type paper forming unit, twin wire, or
Whether or not one of the gap formers is used, it is determined to some extent at least.

As is well known, jets of stock ejected from headbox slices onto paper fabrics are often far from uniform. When the stock is uniform, the various components in the stock are all evenly distributed from corner to corner. Similarly, the stock jet ejected from the headbox slice has a constant density and linear velocity over the entire width of the headbox slice, and there is no undulation or other disturbance, but such an ideal state is actually It is rarely realized. Also, within the stock itself, the distribution of various substances in the stock varies considerably from point to point in both the vertical and horizontal directions. It is desirable that such deficiencies in the stock be removed, or at least controlled to prevent deterioration, before it is transferred to the web due to dehydration of the stock in the molding station. If the dewatering rate is high and uncontrolled in the first part of the forming section, the stock defects described above tend to occur in the paper forming, in which case any correction is almost impossible.

What is currently recognized is that the ability to reduce such high dehydration rates in the early stages of the molding process will improve the overall papermaking process. Naturally, the remaining dewatering elements of the molding part must be able to cope with the increased dewatering burden caused by such a procedure.

The idea of the invention applies equally to both the twin-wire machine and the conventional open surface forming section, ie to improve the stock forming in the area of the forming section immediately adjacent to the headbox slice. be able to.

Reducing the rate of dewatering with a conventional molded plate design only requires reducing the available dewatering range by enlarging each support surface and / or moving the support surfaces closer together. It would seem as simple as that. Experiments have shown that this is not the case and the dehydration rate is not significantly reduced. Furthermore, the web is clearly marked with multiple streaks, and the weight of this fiber varies across the width of the paper. In other words, such fluctuations are
This may cause considerable deterioration of the paper quality.

What has now been revealed is that the above difficulties can be solved and that the forming plate is modified so that a low value of atmospheric pressure (above ambient pressure) can be fed to the machine side of the paper-making fabric. The result is a significantly reduced dehydration rate. In addition, the new design of the forming plate can be provided with means to induce a certain beneficial stirring in the stock.

Therefore, in the first embodiment, an aqueous stock is deposited on the paper fabric from the headbox slice, and a forming section provided with at least one continuously running paper fabric passing through a breast roll adjacent to the headbox slice is provided. In a paper machine having it, the present invention provides an apparatus for improving stock forming, characterized by the following. That is, (a) a perforated molding plate surface supporting the paper-made woven fabric, (b) a dehydration box supporting the molding plate surface, (c) an air supply means including a positive atmospheric pressure source, and the water content of the paper material perforated A barometric pressure control means for maintaining a positive atmospheric pressure in the dehydration box that can be prevented from discharging through the forming plate surface but that cannot prevent stock forming with the paper fabric on the forming plate surface; and (d) ) Dehydration means for a dehydration box capable of closing the applied positive atmospheric pressure and allowing the discharged white water to flow indefinitely, that is, (i) the molding plate surface is a seal strip between the papermaking fabric and the dehydration box. (Ii) The surface of the perforated forming plate is provided with passages through which the paper-making fabric moves, and uniform agitation around the periphery is induced in the stock material at an adjusted level, and (iii) the dehydration box Is extended over the width of the paper-woven fabric, and Standing the pressure control means and having a dehydration means comprises at least one partition.

Normally, it is desirable that the positive pressure be reduced from a high value near the headbox slice to a value close to the ambient atmospheric pressure at the end of the forming plate.

The air supply means is about 0.1 kPa (1 cm water level gauge) to about 2.5 kPa (25 c
It is desirable that a positive pressure higher than the ambient atmospheric pressure, such as a water level meter, can be obtained.

The surface of the forming plate is composed of a large number of plate-shaped and thin blades having a small width and extending over the entire width of the paper-woven fabric, and these blades function to agitate the stock on the paper-woven fabric while controlling it. It is desirable that they are arranged so that

It is further desirable to provide at least a portion of the aforementioned thin, elongated blades with a contoured upper surface that induces controlled agitation in the stock on the paper fabric.

In a second embodiment, a papermaking stock having a forming section with at least one continuously running papermaking fabric where aqueous stock is deposited from the headbox slice onto the papermaking fabric and passing through breast rolls adjacent to the headbox slice. In a machine, the present invention provides a method for improving stock forming characterized by: That is, (i) the aqueous paper stock is discharged onto the above-mentioned moving paper fabric, and (ii) the pressure at a predetermined level that can prevent dehydration but not paper stock formation on the paper fabric is applied. Passing the papermaking fabric through a dewatering device forming a pressurized dewatering box with at least one chamber fed in and a sealing strip between the papermaking fabric and the dewatering box, the perforated upper support surface of the papermaking fabric, and (Iii) Stirring with equal intervals and a uniform period is induced at a predetermined level of pressure in the paper stock on the paper-making fabric on the forming plate.

The atmospheric pressure is higher than the ambient atmospheric pressure, approximately 0.1 kPa (1 cm water gauge)
To about 2.5 kPa (25 cm water gauge) is desirable.

Agitation consistent with a given level of pressure is preferably generated and controlled in the stock by adjusting the spacing of the support surfaces forming the forming plate. It is further desirable to generate an agitation in the stock that matches the above predetermined level of pressure by a contoured support surface of the upper surface that induces a controlled agitation in the stock on the paper fabric. Is.

In each of the above embodiments, the dehydration box is a single box divided into separate partitions by lateral pressure sealing partitions,
Alternatively, it is desirable to have a large number of independent boxes adjacent to each other that can send different levels of pressure to each box.

Hereinafter, the present invention will be described in more detail based on the conventional open-type surface molding part. It is understood that the present invention is not so limited and may be used in combination with another paper machine such as a two-wire type, a twin-wire type or a gap former type. The attached drawings are as follows.

1 is a schematic view of the first part of a paper machine, FIG. 2 is a schematic view of a forming plate of the present invention, FIG. 3 is a possible supporting surface view of the forming plate of FIG. 2, and FIG. Schematic view of another forming plate, in which the related parts such as parts are numbered the same.

FIG. 1 shows a paper woven fabric 1 moving in the directions of arrows 1A and 1B.
Represents the first part of a paper machine incorporating. Paper fabric is
It passes through the breast roll 2, various tension rollers, and the low speed roller 3. The stock is deposited on the paper fabric 1 from a head box indicated by 4 through a slicing opening 5 extending laterally to the paper fabric 1.

Adjacent to the breast roll 2 and the headbox slice 5 is a forming plate, behind which is the first of a number of dewatering units forming the forming part,
In this case, the foil unit 7 is shown based on what was first described by the list of US Pat. No. 2,928,465.

The forming plate unit is provided with a number of bearing surfaces, indicated generally at 12, 13 and 14, of which the bearing surface 12 closest to the headbox slice is usually wider than the remaining bearing surfaces. Each of the above supporting surfaces has a T of 10
It is attached to the bar. As shown in the drawing, the dehydration box 6 simply performs gravity dehydration with the bottom open.

FIG. 2 shows one embodiment of the shaped plate of the present invention. Two differences are obvious with respect to the details of the conventional molding plate of FIG. That is, the molding plate unit is a closed box 20 which is a dehydration box provided with a pressurized air supply pipe 28 here, and is provided with a pressure leg of an integral structure for sealing the pressure applied to the drainage pipe 32. Each supporting surface of the forming plate again comprises a T-bar 10 on which is mounted an elongated blade 17 which extends over the width of the paper fabric. Seal strips S are inserted on both sides of the paper woven fabric on the upper surface of the closed box 20 between the group of blades to substantially seal the paper woven fabric. That is, they are arranged between a group of blades on both sides of the paper-made fabric. The shape of the top surface and its lateral spacing will be described in more detail below.

The first blade 18 needs to react to the impact of the jet of stock as it is discharged from the slicing openings 5 onto the paper fabric 1. Usually, this first blade 18
As shown in FIG. 2, it is much wider than the other blades, often twice the width of subsequent blades.
Presently, in most cases, blades of about the same width as other blades are used. Also, typically, the upper surface of this first blade 18 is flat. This blade 18, like all blades described above, is mounted on a conventional array of T-bars.

The placement and shape of the remaining blades 19 are important. Almost any of the surfaces used to support papermaking fabrics
It is not known to affect the behavior of the stock on the paper fabric. The surface properties can be chosen to cause agitation in the stock, while at the same time the agitation is about lifting the stock from the papermaking fabric almost entirely, so that it can be used for photography, including visible microscopic agitation. It is observable only with the careful use of strobe flash (ie, if the surface is a simple planar blade, such as the first blade 18 described above), through fine agitation. Furthermore, it is not known that arranging the blades along the papermaking fabric is important, especially in the case of a fixed dehydrator. Although the hydraulic phenomena that cause agitation are not completely understood, it is known that harmonized properties appear. This theory can be effectively utilized in the formed plate of the present invention. As a first measure, the blades 19 can be arranged such that the fine agitation induced by the blades 19 is evenly spaced along the length of the forming plate. Therefore, the degree of stirring of the stock material can be controlled by adjusting the stirring amount generated by any one blade.

The amount of agitation produced by each blade is largely determined by the shape of the support surface. A simple flat blade can generate a certain amount of agitation in the range of fine agitation and serve a certain purpose. Generally, for blades used to cause fine agitation in the stock, the amount of dewatering is reduced or even zero. A suitable blade type is
It is described by Johnson in US Pat. No. 3,874,998 and Sudd in US Pat. No. 4,420,370. Such blades can be made using current standard T-bar support theory. The present invention does not preclude the use of a device that produces a constant amount of dewatering in addition to providing the proper amount of agitation.

3A and 3B show a blade that stirs without dehydration, as described by Johnson in US Pat. No. 3,874,998. The blades 37 or 38 in each case rest on the T-bar 10. First, refer to FIG. 3A. On the upper surface of the blade 37 there is a central depression 39, so that a cutting intersection gap in the form of a flat triangle of depth x is created below the plane of the paper fabric. Alternatively, the depression may be recessed with a shallower bottom than the triangle, as shown in FIG. 3B.
In each case, as shown in FIG. 3A, water enters this depression from the stock on the paper fabric 1 and re-enters the stock as represented by arrow 40 in FIG. 3A. Therefore, the distances x, y ₁ ,
By carefully selecting y ₂ and z, the amount of agitation that occurs in the stock is adjusted. The amount of agitation required in this initial stage of paper forming is small in the range of the above-mentioned fine agitation, and therefore even a flat surface blade produces constant agitation as described above, so that all blades are It is possible that it does not have even one dimple.

When used to generate fine agitation, typical dimensions for blades such as those shown in FIGS. 3A and 3B are:

(I) Full width (ie y ₁ + y ₂ : 25mm to 75mm (ii) Flat plane width: Usually y ₁ and y ₂ are almost the same, but not necessarily the same. The minimum is about 5 mm.

(Iii) Indentation width z: 15 mm to 65 mm (iv) Indentation depth x: 0.25 mm to 2.5 mm for both triangular and curved indentations A suitable value for the indentation width z is about half the total width of the blade. Is. Therefore, in the above range, the front flat surface portion and the rear flat surface portion (y ₁ and y ₂ ) suitable for bringing the water seal together with the paper-making fabric into contact with the blade are secured. Further, since the depth influences the amount of stirring, a wider blade does not necessarily require a deeper recess. It will be seen that in many cases, as the blade is enlarged, the width z increases to maintain about half the overall width of the blade, but the depth x does not need to be changed. Some care must be taken when choosing the right blade for a particular environment. It is necessary to use the thinnest blades that provide adequate support, and thus the shaped plate according to the invention will typically use more supporting blades than conventional plates. Furthermore, the blades used are all
It can have the same width. Similarly, the use of the shallowest depressions is sufficient to produce the proper amount of agitation. If the manufactured blade is too wide or the recess is too deep, the degree of agitation greatly exceeds the fine agitation necessary for the paper fabric in this range, and the paper fabric loaded with paper rises away from the blade. And therefore does not lead to the production of good quality paper. While it is relatively easy to use a blade with a single depression, it has been recognized that in certain circumstances a wider blade with two or more depressions is desired. When using such a blade, the central flat portion between the depressions should be approximately the same width as the flat front and rear surfaces.

FIG. 4 shows the preferred embodiment. The dehydration box, generally designated 6, is divided by lateral walls 24, 25, 26 into a series of relatively small pressure-sealing partitions 20, 21, 22, 23. Four partitions are shown, but this number is not important. Also, a series of separation boxes could be used, with each side wall adjacent. Each of the partitions 20 to 23 extends over the entire width of the paper fabric. The blades, indicated at 27, are in each case arranged on each lateral wall. Each of the partitions has a pressurized air supply pipe 28, 29, 3 which is a part of a pressure control means (not shown).
0, 31 are also provided, and also drain legs 32, 33, 34, 35 provided with means suitable for sealing the pressure in the partition while allowing free drainage. This arrangement allows each box to be fed with a critical pressure above the ambient pressure, which is different for each box.

Normally, the pressure applied is gradually reduced from the box on the partition 20 side adjacent to the head box slice to the box on the partition 23 side, and the pressure sent to the box on the partition 26 side is
Low pressure or no pressure. It is also conceivable that such a grading may lead to an unfavorable state, for example, as may be seen in the box on the side of the partition 21 where maximum pressure is desirable.

Front Page Continuation (72) Inventor Pitt, Richard Edwards, Canada, K7C3W3, 18 Braun Street, Carlton Place, Ontario (56) References US Patent 3060668 (US, A)

Claims (11)

[Claims] 1. At least one continuous run of the paper stock, wherein aqueous stock is deposited from the headbox slices onto the papermaking fabric and passing through a breast roll adjacent to the headbox slice, and supporting and forming the paper fabric. A paper machine having a forming part provided with a seal strip between a woven fabric and a dehydration box and having a surface of a perforated molding plate supported by the dehydration box, wherein: (a) the dehydration box includes a positive pressure source. And a positive pressure that can prevent moisture of the stock from draining through the perforated forming surface, but that does not prevent the stock forming of the paper fabric on the forming plate surface is maintained in the dehydration box. (B) The dehydration box seals the applied positive pressure higher than the ambient atmospheric pressure in the dehydration box and discharges the white water discharged from the dehydration box. Comprising a dehydration means capable Succoth, (c) the dehydration box extends across the width of the papermaking fabric, and has a dewatering means an independent pressure control means,
A paper machine comprising at least one partition. 2. The surface of the forming plate is composed of a large number of blades arranged at equal intervals extending over the entire width of the paper-made fabric, and a seal strip is interposed between the blade ends. The paper machine according to Item 1. 3. The paper machine according to claim 2, wherein the first elongated blade adjacent to the headbox slice is wider than the remaining blades. 4. At least one of the elongated blades comprises:
3. Paper machine according to claim 2, characterized in that it has an upper surface contour designed to cause stirring of the stock on the paper fabric. 5. A flat surface having a front portion and a rear portion in the direction of travel of the paper fabric, wherein the contour of the upper surface is separated by at least one shallow indentation extending along the blade in the width of the paper fabric. And, each of the front portion and the rear portion, and any flat portion interposed in each recess of the bottom has a width sufficient to provide a water seal on the machine side of the paper-making fabric, The paper machine according to claim 4, wherein the degree of agitation is controlled by adjusting the depth and / or the shape of the shallow depression. 6. The dehydration box comprises a number of lateral pressure-sealed partitions (a positive pressure adjusted between the partitions can be fed separately from the vicinity of the head box slice, and independent dehydration means is provided for each partition. A single box that extends to the edge of the forming plate with a) or extend from near the headbox slice and feed adjusted positive pressure to each box separately, each box being independent A paper machine as claimed in claim 1, characterized in that it comprises a number of adjacent boxes with dewatering means. 7. The dehydration box comprises a number of lateral pressure-sealed partitions (a positive pressure adjusted between the partitions can be fed separately from the vicinity of the headbox slice, and independent dehydration means is provided for each partition. A single box that extends to the edge of the forming plate with a) or extend from near the headbox slice and feed adjusted positive pressure to each box separately, each box being independent A plurality of adjacent boxes with dewatering means, in addition, elongated blades are placed on the first lateral pressure-tight partition in the dewatering box and on any intervening pressure-tight partitions. The paper machine according to claim 2, characterized in that 8. An aqueous paper stock is deposited from a headbox slice onto a paper fabric and at least one continuous run of the paper fabric through a breast roll adjacent to the headbox slice, and supporting and forming the paper fabric. A paper machine having a sealing strip between the fabric and the dehydration box, supported by said dehydration box, and having a forming part with a forming plate surface adjacent to the headbox slice, moving the aqueous stock from the headbox slice as described above. In the method of discharging onto a paper fabric, which is (i) a predetermined level of pressure that can prevent the stock on the paper fabric from being dehydrated but cannot prevent the formation of the stock on the paper fabric is applied. Passing the paper fabric on a perforated forming surface having a pressurized dehydration box with at least one chamber to be fed, and Stirring uniform period with ii) at regular intervals, at a pressure of a predetermined level, a method for improving stock shaping for causing induced in the stock on the perforated mold plate. 9. The stock molding according to claim 8, wherein the perforated surface is provided with a passage through which the paper-making fabric moves to induce agitation in the stock corresponding to a predetermined level of pressure. How to improve. 10. A porous strip comprising a large number of blades arranged at equal intervals extending over the entire width of the paper-making fabric, and a seal strip interposed between the blade ends. Item 10. A method for improving stock molding according to Item 9. 11. The dehydration box comprises a number of lateral pressure-sealing partitions (near the headbox slice, a positive adjusted atmospheric pressure can be separately fed between the partitions, and each partition can be independently dehydrated). A single box extending up to the edge of the forming plate with a means) and elongate blades on top of the first and last lateral pressure-sealing partitions in the dehydration box and any intervening pressure between them. 11. Method for improving stock forming according to claim 10, characterized in that it is arranged on a closed partition.