RU2334035C2 - Open moulding element, intended for double-grid papermaking machine - Google Patents

Abstract

FIELD: soft wares, paper.

SUBSTANCE: invention concerns pulp and paper industry. Open moulding element, intended for double-grid papermaking machine, outfitted by pipeline and supporting moulding grids. Grids are supported by reference element set, which are supported by aspirate boxes tandem. Aspirate boxes has spun supporting surfaces and outfitted by separated areas of water drainage. Aspirate boxes are outfitted by, at least, four separated detached decompression sections. Spun surfaces radius of curvature reduce gradually along-running direction or reduce at consistent supporting surfaces along-running direction. Pitch of grids reference elements within every of decompression section remains steady and reduces in consistent decompression sections, or reduces along-running direction within every of decompression section. Aspirate boxes are located thereby grid reference elements are placed alternate relative to both sides of moulding grids.

EFFECT: improving of manufactured paper products quality.

7 cl, 10 dwg, 1 tbl

Description

The invention relates to a two-mesh forming part with gaps, intended for use in a paper machine, in which the source material is injected from the outlet slit of the headbox directly into the gap between two moving forming nets. The molding part of the present invention thus does not contain a portion of a previously exposed surface using only one molding mesh. The present invention relates to that section of the forming part, which is located between the location at which the forming grids meet and between which the source material is placed, and the location at which the two forming grids are separated, with the source material remaining on one of the grids. This invention is suitable for use both for rebuilding existing dual-mesh forming parts, and for new forming parts with gaps.

In the forming part of the paper machine, the two forming grids do not move in a straight line. The nets together run along a sequence of shafts and suction boxes that are located on opposite sides of the two nets and thus define the winding path of the two nets. Each suction box has a curved surface on which there is a group of supporting elements of the mesh, such as blades, which are in contact with the machine sides of the forming nets. Each suction box can also be connected to a controlled vacuum source. These curved surfaces cause the moving forming nets to move along the desired winding path. The effect of the controlled level of rarefaction on the suction boxes has two effects: this leads to the removal of water from the source material located between two moving forming nets, and this deviates the path of two moving forming nets into the gaps between the supporting elements of the nets. This deviation of two moving forming grids leads to the formation of pressure pulsation in the layer of the source material sandwiched between the grids, which leads to the occurrence of fluid movement inside the source material in the direction of movement; this gives rise to a shear action inside the starting material, which serves to shred fiber fragments.

The actual amplitude of each of the pulsating pressure fluctuations generated by the deflection angle of the moving forming nets at the edges of each supporting element of the nets is of great importance for the quality of the manufactured product. The strength of the pulsating pressure fluctuations generated by each supporting element of the grids should be selected so as to correspond to the state and properties of the starting material for this supporting element of the grids. Therefore, there is a need to be able to modify the strength and / or amplitude of the pulsating pressure fluctuations with more water discharged from the starting material and with the formation of the resulting paper web.

It is recognized that poor control of the deflection of the mesh in the forming part has an adverse effect on the molding process, which in turn has a negative effect on the quality of paper products.

It was found that the actual angle of deviation of the mesh at the edge of each supporting element of the mesh in the working two-mesh forming part depends on several factors.

They include:

1) the geometric layout of the physical components used in the design of the forming zone, including the step between the supporting elements of the grids, the width of the supporting elements of the grids in the direction of movement and the radius of curvature of the surfaces to which the supporting elements of the grids are attached;

2) the level of sparseness in the suction boxes, which controls the degree of deviation of the moving forming nets in the gaps between the supporting elements of the nets;

3) the amount of tension in the direction of movement, which acts on two moving forming mesh.

The following terms used here have the following meanings:

(1) the term "direction of movement" or "ND" means a direction usually parallel to the direction of movement of the two forming nets from the outlet slit of the headbox;

(2) the term "step" means the distance between the centers of adjacent support elements of the grids in the direction of movement;

(3) the terms "support element of the mesh" and "support elements of the mesh" mean:

or moving surfaces, such as shafts over which the forming mesh rolls,

or static surfaces, such as blades, hydroplanes, or the like, on which a forming mesh slides.

At the initial stages of sheet formation, when the level of sparseness acting on the side of the forming grid and, therefore, on the forming paper web is low, the geometry of the forming part and the tension acting on both forming grids are the predominant factors that control the deviation of the forming grids. Moreover, although the tension acting on both forming grids is usually the same, two different levels of tension can be used. Two tension values are set within the framework of the general model of adjustments in order to obtain the desired level of pulsating pressure fluctuations inside the source material located between two moving forming grids.

From the point at which the starting material is first placed between two moving forming nets, to the point at which the two forming nets are separated, the density of the starting material is continuously increasing as water is removed from the forming paper web. At the same time, when the density of the starting material increases, the mobility of each individual fiber within the starting material also decreases accordingly. These changes require stronger pulsating pressure fluctuations to provide beneficial fiber movement, which improves the properties of the sheet in the forming paper web. However, the resulting paper web eventually reaches a density at which no further fiber movement occurs. From this point until the two moving forming nets are separated, the force of the pulsating pressure oscillations must be controlled by carefully selecting the desired vacuum level so that water continues to flow, and by carefully selecting the radius, step of the grid support element and the width of the support element mesh, so that the force of the pulsating pressure fluctuations does not reach the level at which the formed paper web is damaged.

During the initial sheet formation, when the useful movement of the fibers can still continue, the need for stronger pulsating pressure fluctuations can increase at a faster rate than can be obtained by controlling the vacuum level, acting only on the forming grids. This is because the vacuum level should be limited to a value that will not cause excessive water drainage, which, on the one hand, will reduce the mobility of the fibers, and on the other hand, set the properties of the sheet before the necessary beneficial properties are obtained. Thus, it is important to obtain a greater pressure pulsation in order to achieve a greater deviation of the forming grids at the edges of the supporting elements of the grids by using a wider step between these elements and / or using a larger radius of curvature of the structure to which the supporting elements of the grids in contact with the grids are attached, and / or by using supporting mesh elements, such as blades, arranged so as to increase the deviation of the mesh into the gaps between the supporting mesh elements.

Thus, it is clear that there is a matrix of variables that must be taken into account when optimizing the quality of sheet products. The present invention is based on an understanding of what factors should be considered in the criteria for improving a two-mesh forming part with gaps for a paper machine:

(a) the step of the supporting elements of the grids should decrease gradually in the direction of movement;

(b) the level of vacuum acting on the forming mesh by means of suction boxes should increase in the direction of movement;

(c) two forming grids together with the source material placed between them, as they move in the direction of movement, must pass through at least four separate separate rarefaction zones located in the forming part;

(d) the rarefaction level acting on the last of at least four separate separate rarefaction zones should be higher than the vacuum level acting on the first of the data of separate separate rarefaction zones;

(e) a rarefaction level acting on at least four separate separate rarefaction zones must correspond to a predetermined circuit;

(e) the suction boxes carrying the supporting elements of the nets should be arranged so that the supporting elements of the nets are staggered relative to the sides of both forming nets.

Thus, in the first main embodiment of the present invention, there is provided a double-mesh forming portion with gaps for a paper machine having a conveyor forming mesh and supporting a forming mesh such that:

(1) each of the forming grids has a side facing the paper and a machine side;

(2) forming grids move together, being located close to each other, in the direction of movement, and between them there is a layer of source material;

(3) the forming nets are supported by sets of supporting mesh elements, the forming nets being in contact with the machine side of these elements, the supporting mesh elements are supported by suction boxes arranged in series, each of these suction boxes has a curved supporting surface consisting of supporting mesh elements;

(4) the suction boxes are equipped with separate zones of water drainage, at least some of them are connected to a vacuum source in order to create separate vacuum zones, where:

(a) the forming zone contains that part of the forming part, which is located between the point at which the forming nets meet and clamping the source material from two sides, and the point at which the two forming nets are separated and the starting material continues to move on one of them;

(b) the suction boxes are equipped with at least four separate separate rarefaction zones located inside the forming part;

(c) or the radii of curvature of the curved surfaces supporting the supporting elements of the meshes decrease progressively in the direction of movement,

or the radii of curvature of the curved surfaces supporting the supporting elements of the meshes are reduced on successively running supporting surfaces in the direction of movement;

(d) or the step of the supporting elements of the grids within each rarefaction zone remains constant and the step of the supporting elements of the grids in successively extending rarefaction zones decreases in the direction of motion;

or the step in successively running support elements of the grids inside each rarefaction zone decreases in the direction of movement;

(e) the suction boxes supporting the supporting elements of the nets are made and arranged so that the supporting elements of the nets are in contact with the machine sides of the conveyor forming mesh and the supporting forming mesh in a checkerboard pattern in the direction of movement;

(e) on all suction boxes:

or all the supporting elements of the grids have the same width in the direction of movement;

or all the supporting elements of the grids have an unequal width in the direction of movement.

It is preferable that the step of the supporting elements of the grids within each rarefaction zone is constant and the step of the supporting elements of the grids within successively arranged rarefaction zones decreases in the direction of movement. Alternatively, the pitch of the supporting grid elements within each rarefaction zone may not be constant, and the pitch of the supporting grid elements within each of the successively located rarefaction zones decreases in the direction of movement.

Preferably, the radii of curvature of the curved surfaces supporting the supporting elements of the grids in successively located rarefaction zones are reduced in the direction of movement. Alternatively, the radii of curvature of the curved surfaces supporting the supporting elements of the meshes in successively located rarefaction zones decrease progressively in the direction of movement.

Preferably, each suction box is provided with at least one rarefaction zone. More preferably, at least one suction box is provided with at least two vacuum zones. Even more preferably, all suction boxes are provided with more than one vacuum zone.

Preferably, the ratio of the width of the supporting elements of the nets to the width of the gap between them varies from about 1:10 to about 1: 0.5.

Preferably, the forming part contains a mesh-rotary shaft, equipped with a drainage of water with vacuum. Alternatively, the forming part includes a mesh rotary shaft not provided with a vacuum with a vacuum.

The invention will now be described with reference to the accompanying drawings, in which:

figure 1 - forming part with gaps in accordance with the first embodiment of the present invention;

figure 2 is a schematic illustration of the collision zone in figure 1;

figure 3 - image of the second, third and fourth suction boxes in figure 1;

figure 4 is an alternative solution compared to figure 3;

5, 6 and 7 are schematic views of additional alternative solutions for the collision block in FIG. 1;

Fig. 8 is a solution in which a collision shaft is used;

Fig.9 is an alternative solution compared to that shown in Fig.1;

figure 10 is an alternative solution compared to that shown in figure 1.

Figure 1 shows a double-mesh forming part 1 with gaps used in a paper machine. The forming part 1 is located vertically, the arrow A shows the vertical direction.

The forming part 1 starts from the place where the conveyor forming net 2 enters the forming part 1 around the first forming shaft 3, and the supporting forming net 4 enters the forming part 1 around the second forming shaft 5 and ends where the supporting and conveyor nets 2 and 4 are separated from each other after passing through the mesh-rotary shaft 6. Between the two forming grids 2, 4 inside the forming part 1 is placed a layer of source material 7, moved from the outlet slit 8 of the head box to the point 9 of the collision. Two forming nets 2, 4 move together through the forming part 1 in the direction shown by arrow 10. Thus, it is clear that the source material 7 moves upward through the forming part 1. As will be described below, other solutions are possible.

Four suction boxes 11, 12, 13 and 14 are located between the first forming shaft 3 and the adjacent second forming shaft 5 from one end of the forming part and the mesh-turning shaft 6 from the other end. Each of these boxes has a curved surface 15, 16, 17 and 18, respectively that support grid support elements (not shown). The supporting elements of the nets provide a curved supporting surface on each of the suction boxes 11, 12, 13 and 14 for forming nets 2, 4.

As shown, these four suction boxes 11, 12, 13 and 14 are arranged on opposite sides of the forming nets 2, 4 in a checkerboard pattern so that the two forming nets 2, 4 are wound around the supporting elements of the nets (such as the supporting elements 26, 27, 28 the grids shown in FIG. 3) located on each curved supporting surface 15, 16, 17 and 18 in the sequence in which they together move in direction 10 through the forming part 1.

The four suction boxes 11, 12, 13 and 14 are not the same.

The first suction box 11 is a collision block to which a controlled vacuum formed by a vacuum source (not shown) is supplied through the compartment 24. A preferred collision block of this type is described in US 2003/0173048. Other solutions may also be used to implement the collision block.

The second suction box 12 is divided into two separate zones 19 and 20, each of these zones 19 and 20 may have a separate source of controlled vacuum (not shown).

The third suction box 13 is also divided into two separate zones 21 and 22, each of these zones 21 and 22 is equipped with its own source of controlled vacuum (not shown). This is done in order to have two separate vacuum zones 21 and 22 independently controlled.

The fourth suction box 14 is not divided and has only one compartment 23, equipped with a source of controlled vacuum (not shown). If necessary, the suction box 14 may have two vacuum zones, as shown for the box 13.

It is clear that these four boxes contain at least six separate zones of controlled depression, over which two moving nets pass. In the direction of movement, zones 24, 19, 20, 21, 22, and 23 are successively encountered. These six zones are designed so that the two forming nets 2, 4 and, therefore, the source material 7 located between them, are exposed to the following conditions:

1) the applied vacuum varies from almost zero in zone 24 to the maximum in zone 23;

2) the radius of curvature of the curved surfaces supporting the supporting elements of the grids varies from a maximum on surface 16 in zone 19 to a minimum on surface 18 in zone 23;

3) the step of the supporting elements of the grids in the direction 10 varies from a maximum on the surface 16 to a minimum on the surface 18.

Figure 2 shows in detail the point 9 of the collision with figure 1. Two forming mesh 2, 4 converge at the point 9 of the collision, where the source material 7 is placed between them. Next, two moving nets go along a curved path defined by the outline of the side facing the paper, curved surface 33 of the collision pad located on surface 15. When using the collision pad described by Buchanan and others in US 2003/0173048, the curved surface 33 of the pad The collision contains a number of gaps (not shown) that can be rotated by a certain angle relative to direction 10.

Figure 3 shows in more detail the suction boxes 12, 13 and 14 in figure 1. Some features of this set of suction boxes are clear in FIG.

First, it can be seen that the radius of curvature of the three curved surfaces 16a, 16b, 17a, 17b and 18 decreases in the direction of motion indicated by arrow 10.

The second step of the three sets of support elements of the grids is shown in more detail.

It:

- the first set, indicated by the number 26, located on the suction box 12;

- the second set, indicated by the number 27, located on the suction box 13;

- the third set, indicated by the number 28, located on the suction box 14.

In these sets, the width of the surfaces supporting the grids and consisting of the supporting elements of the grids is constant. The step of the grid support elements is described more complexly:

- inside each set 26, 27 and 28 attached to the curved surfaces 16, 17 and 18, respectively, the pitch remains constant;

- however, the step used within each set decreases in the direction of movement 10, so that the step in set 26 is wider than the step in set 27, and the step in set 27 is wider than the step in set 28. It is also clear that the step of the supporting elements of the meshes in the set 27 decreases (i.e. becomes narrower) in the direction of movement 10.

Thus, in a sequence of sets, the pitch decreases in the direction of motion, and the radius of curvature also decreases sequentially in the same direction.

Fig. 4 shows an alternative solution with respect to Figs. 1 and 3. In Figs. 1 and 3, the surfaces of all suction boxes are convex, so that two moving forming nets 2, 4 are wrapped around the supporting elements of the nets due to the tension on two moving forming nets 2 , 4. In Fig. 4, opposite the suction box 12, there is an additional suction box 30. Since this suction box is located on the opposite side of the convex curve of the two forming nets, the supporting elements of the nets, indicated by the number 31, must be fixed flexible. A suitable fastening method is described in US 6361657.

Figures 5, 6 and 7 show alternative designs for collision blocks 11. 1, a groove block is used as described in US 2003/0173048.

Fig. 5 shows a combination of a first suction box 11, which can be seen in Figs. 1 and 2, which includes a curved surface 33 of the collision block, and a suction box 30, which is shown in Fig. 4 and contains flexibly attached support elements 31 of the nets.

The solution shown in FIG. 6 shows a conventional collision block 34 on which a small plurality of support elements of the grids 35 are located.

The design of the collision pad 11 shown in FIG. 7 again follows the concept from US 2003/0173048 (FIG. 1), but it is located on the other side of the two forming nets adjacent to the first suction box 12. Thus, instead of touching side of the moving forming mesh 2, in this case, the box is in contact with the side of the forming mesh 4.

On Fig shows another solution that uses a collision shaft 40. The collision shaft 40 is provided with a controlled vacuum source (not shown) and has a vacuum zone 41. Shafts with a vacuum of this type are well known at present. In this solution, the point 9 of the collision of the source material is where two moving nets 2, 4 begin to contact on the vacuum shaft 42.

Figure 9 presents an alternative solution in relation to the solution depicted in figure 1. Comparison with figure 1 shows that there is located on the opposite side of the suction box 30 containing the supporting elements 31 of the nets. This box is located next to box 11. In FIG. 1, the suction box 13 has two compartments 21 and 22. In FIG. 9, this suction box is replaced by a suction box 50 having three compartments 51, 52 and 53. Also, the one-volume suction box 14 in FIG. .1 is replaced in FIG. 9 by a suction box 54 having two compartments 55 and 56. Next, the shaft 6 is shown having a vacuum compartments A and B, which can be found on a conventional gauch-shaft. The adapter box C is located lower in the direction of movement of the shaft 6, where the supporting mesh 4 is separated from the conveyor mesh 2, carrying the layer 7 of the source material from the adapter box C further in the direction of movement to the press part (not shown). Alternatively, shaft 6 may be monolithic.

Figure 10 shows another additional alternative solution with respect to the solution depicted in figure 1. In this case, the second forming block 57 is located lower in the direction of movement relative to the suction box 11. The forming block 57 having one compartment 59 is preferably provided with a cover 58 with grooves and is made in accordance with the ideas of US 2003/0173048, although other options may also be used Forming pad designs currently known. The forming block 57 is provided with a curved cover 58 with grooves and is positioned so that the grids 2, 4 together with the source material layer 7 repeat its contour, which, generally speaking, is opposite to the contour of the lid 15 of the box 11. This change in the curvature of the grid path to the opposite leads to the action on the source material 7 pulsating pressure fluctuations in order to shake paper fibers. The path of the nets 2, 4 then again experiences some curvature when the nets together pass over a curved surface defined by the supporting elements 26 of the nets located on the lid 16 of the suction box 12 described above in discussing FIGS. 3 and 4. As described in a discussion of FIG. 4 , the suction box 30 is located opposite the suction box 12 and is likewise provided with a plurality of support elements 31 of the nets, alternating in opposite manner with similar elements on the suction box 12. Mesh 2, 4 with the source material 7, s pressed between them, forced to bend in the opposite direction above the surface 17 of the box 13 in the same way as shown in figure 1. Following the box 13, the grids 2, 4 pass together above the surface of the supporting elements of the grids (not shown) located on the cover 18 of the box 14. Next, the grids 2,4 pass around the grid-turning shaft 6, which can be monolithic or have one or more discharge compartments A and B, as described in the discussion of FIG. 9. The transmission box C, located lower in the direction of movement relative to the mesh-rotary shaft 6, helps to separate the grids 2 and 4 so that the sheet of paper remains on the conveyor grid 2.

In the drawings, all supporting elements of the meshes are shown schematically having the same width in the direction of travel. In practice, the supporting elements of the nets may not have the same width for all suction boxes. Some suction drawers may require support elements of nets of a different width to accommodate the volume of white water discharged from the forming nets at a given location. It is also possible that the supporting element of grids of a different width may be needed to obtain the necessary level of pulsating pressure fluctuations of the source material in some place. Experience shows that the ratio of the width of the supporting elements of the grids to the width of the gap between them should be from about 1:10 to about 1: 0.5.

The drawings depict suction boxes that have more than one compartment, each of which is under vacuum controlled level. If the level of rarefaction in adjacent compartments or suction boxes does not coincide, then it is desirable that the curvature of the surfaces, as well as, possibly, the corresponding step of the support element of the nets, be different. Moreover, experience shows that it is desirable that the level of rarefaction in the sequence of suction boxes or compartments should increase relatively smoothly in the direction of movement. Although the level of rarefaction can remain constant in two adjacent suction boxes or compartments, it should not decrease in the direction of movement and, moreover, there should be no pressure surges. In other words, all variables do not have to change gradually, stepwise; neighboring zones may have the same values for at least some variables.

Using a paper machine with a two-mesh forming part, basically corresponding to that schematically shown in Fig. 9, several newsprint samples were made. It turned out that the sparseness profile shown in the table gives rise to improved paper quality compared to other paper machines with a conventional two-mesh forming part. In the table, the designations of places refer to the numbers of the departments of the suction boxes and the collision block, these numbers can be found in Fig.9.

Table A place Sparseness, kPa eleven 1,2 twenty 3.8 51 8.5 52 12,2 53 14.6 55 22.6 56 27.9 BUT 38.6 AT 51.0 FROM 62.1

Claims (7)

1. The forming part with gaps, intended for a two-mesh paper machine, having a conveyor forming grid and supporting a forming grid, such that: each of the forming grids has a side facing the paper and a machine side; forming grids move together, located close to each other, in the direction of movement, and between them there is a layer of source material; forming nets are supported by sets of supporting mesh elements that are selected from the group consisting of shafts, fixed supporting mesh elements in contact with the nets, and at the same time shafts and stationary supporting mesh elements in contact with the nets, the forming nets being slidable along the machine side elements, the supporting elements of the grids are supported by suction boxes arranged in series, each of these suction boxes has a curved supporting surface, consisting drawer from the supporting elements of the grids; the suction boxes are provided with separate drainage zones, at least some of them are connected to a vacuum source to create separate vacuum zones, in which the forming zone comprises that part of the forming part, which is located between the location where the forming grids meet and clamp the source material from two sides, and the location where the two forming grids are separated, and the source material continues to move on one of them; the suction boxes are provided with at least four separate separate rarefaction zones located inside the forming part; the radii of curvature of the curved surfaces supporting the supporting elements of the meshes decrease gradually in the direction of movement, or the radii of curvature of the curved surfaces supporting the supporting elements of the meshes are reduced on successive supporting surfaces in the direction of motion; the step of the supporting grid elements within each rarefaction zone remains constant, and the step of the supporting grid elements in successive rarefaction zones decreases in the direction of movement, or the step in the successive supporting grid elements within each rarefaction zone decreases in the direction of movement; the suction boxes supporting the supporting elements of the nets are made and arranged so that the supporting elements of the nets are in contact with the machine sides of the conveyor forming mesh and the supporting forming mesh in a checkerboard pattern in the direction of movement, while all the supporting elements of the nets have the same width on all suction boxes direction of movement, or all supporting elements of the grids do not have the same width in the direction of movement. 2. The forming part according to claim 1, in which each suction box is equipped with at least one rarefaction zone. 3. The forming part according to claim 2, in which at least one suction box is equipped with at least two rarefaction zones. 4. The forming part according to claim 3, in which each suction box is equipped with at least two rarefaction zones. 5. The forming part according to claim 1, in which the ratio of the width of the supporting elements of the grids to the width of the gap between them varies from about 1:10 to about 1: 0.5. 6. The forming part according to claim 1, which contains a mesh-rotary shaft equipped with a water outlet with vacuum. 7. The forming part according to claim 1, which includes a mesh rotary shaft that is not equipped with a water outlet with vacuum.

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