FI85732C - FOERFARANDE I INLOPPSLAODAN AV EN PAPPERSMASKIN FOER ATT KONTROLLERA FIBERORIENTERINGEN AV PAPPERSBANAN. - Google Patents

Description

85732

Method for a paper machine perälaatlkossa to control paperlrainan fiber orientation method 1 inloppslädan of a paper 5 for checking fiberorienteringen of the paper web 10 of the invention relates to a method for the paper machine perälaatlkossa to control paperirai-nan fiber orientation, in which method the headbox flow channel to both opposite edge portions of the additional flows in the headbox in the prevailing direction of flow of the pre its lip portion of the turbulence generator and in which method, by adjusting the magnitude and / or interrelationship of the additional flows, a transverse flow rate compensating for the skew of the fiber orientation is generated in the lip flow of the headbox.

The aim is to construct known headboxes in such a way that paper homogeneous in weight, shape and strength properties over the entire width of the web can be produced, from which as little as possible would have to be cut off from the edges of the web. To achieve said objects, it is already known to use different additional or exhaust flows on each side wall of the headbox lip channel at both sides, for which reference is made to the applicant's FI patent 30095 and Beloit Corporation's FI patent 43812.

Paper, especially fine paper, is required to have even greater structural uniformity, which is required by the recently introduced printing and copying methods in which the sheet is heated very quickly and hard.

A particularly important requirement is that the major axes of the directional distribution of the paper fiber network coincide with the directions of the major axis 35 of the paper and that the orientation be symmetrical with respect to these axes. For example, in copy papers, it is important that their top and bottom surface orientations are substantially the same. Sufficiently accurate implementation of the above requirements over the entire width of the web is not possible with the solutions described above. The diagonal curvature of the sheet and the "fall" of the form stack have been particularly awkward and causing complaints.

5 The problems raised by the applicant have been thoroughly investigated by the applicant. In this case, it has been shown that the symmetry required of the fiber orientation requires that at no point in the finished web, a higher transverse velocity of about 1-3 cm / s is exceeded, which is sufficient to pour the main orientation of the fibers. ° deviating from the machine direction (depending on the s / v ratio), causing the above-mentioned "tipping" and warping problems. Since the transverse velocity is already generated in the lip channel with the damping of the uneven main flow profile, the main attention must be paid to the uniformity of the velocity profile in the direction of flow 15 after the turbulence generator.

The systematic cause of the transverse velocity in the lip channel is the effect of slowing down the friction caused by the vertical side walls of the lip channel in the machine direction. Another systematic effect is the spillage or spreading of the stock on the flat wire portion 20 in the edge areas of the wire as the 10-30 mm thick layer self-levels. To compensate for these effects, the previously known additional feeds of side flow are excellently suited.

At current manufacturing tolerances, no major differences in main flow profile, e.g. due to turbulence generator split, have been observed that they would not be attenuated to an insignificant level in the lip channel.

Applicant's FI Patent No. 75377 (cf. U.S. Pat. No. 4,687,548) discloses a method for controlling the fiber orientation skew profile with a headbox which allows for the slight inaccuracy that always occurs in productive manufacturing. Em. The method of the FI patent is characterized in that additional flows of the pulp suspension are directed in the flow direction of the headbox to the edge cells at the turbulence generator 35 preceding its lip part, and by adjusting the magnitude and / or mutual ratio of

Em. The invention of the FI patent is based on a flow control system for each edge region 5 of the headbox, in which, in a region a few centimeters wide, the flow discharged from the turbulence generator into the lip channel can be controlled within a sufficiently wide range.

Em. The operation and mode of action of the method disclosed in the F1 patent can be characterized as follows. If the flow of the second edge region of the lip channel is increased above the average flow, a continuous cross-flow towards the opposite edge is created in the lip channel and further on the wire, the maximum value of which is at the border of the said adjustment range decreasing steadily towards zero as the other edge of the lip gap is approached. If an equal increase in mass feed is then made at the other edge of the wire as well, a reverse transverse flow symmetrical with the previous one is created. The cross-flows are summable and the end result is that each edge has a maximum flow towards the middle and the cross-velocity in the middle of the machine is zero with equal but different speeds canceling each other. Correspondingly, the maximum values of the orientation skew at different edges and the symmetry of the orientation in the middle of the path are observed from the paper. The graph of the orientation skew is thus an inclined line that intersects the zero plane in the middle of the orbit. If the graph of the orientation skew had, for one reason or another, before em.

25 FI correction according to the FI patent equal but opposite slope, the distortion has been removed by the adjustment.

The object of the present invention is to make use of a new method and to further develop the method 30 disclosed in the above-mentioned FI patent 75377 for controlling the skew of the fiber orientation of a paper web.

The object of the invention is to provide such a method by which the fiber orientation can also be controlled in the z-direction of the paper. This is an important goal for several different grades of paper, especially fine and copy papers, so that the orientations of the top and bottom surfaces of the paper are substantially the same.

4,85732

The infiltration of the wire part typically takes place in layers, so that the surfaces (s) against the wire (s) seep first and the fibers close to the upper surface (middle layer) last. (Comments in parentheses apply to the kit, others to the hybrid). The velocity components of the unfiltered pulp in the form of fluid-5 may change due to friction and pressure shocks of the dewatering elements, so that the main orientation direction of the infiltrating fibers varies in the z-direction depending on the point of the wire section where the infiltration has taken place. Without the possibility of adjusting the transverse speed in the z-direction, it is not possible to influence the layered orientation, which may result in, for example, diagonal curvature.

It is a particular object of the invention to provide a new method by which the diagonal curved sea bucket of a paper web can also be better controlled. Diagonal curl of the paper sheet due to the upper and lower sides of different orientation angles of the various layers. For this and other background related to the invention, reference is made to the journal article in the Journal of Pulp and Paper Science, Vol. 17 No. 2, March 1991, T. Uesaka: "Dimensional Stability of Paper, Upgrading Paper Performance in End 20 Use", J39-J46. With regard to the diagonal curvature, reference is made to component k3 in Fig. 6 (p. J41) of the above article, which is discussed in the first paragraph of the first column of page J45.

It is a further object of the invention to make possible an adjustment method by which the orientation profiles of opposite surfaces of the paper can be measured and these measurement results can be used in the method according to the invention. It is intended that said measurements can be performed either as laboratory measurements or as direct on-line measurements of a paper web.

30

In order to achieve the above and later objects, the invention is mainly characterized in that in order to control the thickness-oriented (z-direction) orientation of the paper produced by the headbox-associated paper machine, the thickness distribution of said additional flows is layered in both edge regions of the headbox.

85732 5

The edge currents according to the invention can be used to influence the orientation of the paper web in the z-direction in layers. The purpose of the additional flow control devices used in the invention, such as valves, is to provide layer-controlled different amounts of additional feed flows at the edges of the lip-5 channel to the different layers of paper in the thickness direction. Either a pulp suspension and / or water can be used as the feed medium. If a pulp suspension is used as an additional feed, it can be taken from different points in the pulp system, preferably from the headbox distribution supports.

The number of z-direction paper layers controlled by the additional feeds according to the invention can generally vary between 2 and 10. Three layers are particularly suitable, in which case said layers can be designated as an upper layer, a middle layer and a bottom layer, the respective flow channels of which are preferably separated in the lip channel of the headbox by hetero plates. However, the use of hetula plates is not always necessary. The feed channels of the different layers do not necessarily have to be equal in size or identical in hydrodynamic resistance.

In the following, the invention will be described in detail with reference to some application examples of the invention schematically shown in the figures of the accompanying drawing, to which the invention is not limited.

Figure 1 shows schematically and partly in block diagram form a method according to the invention and an associated on-line control system based on measuring surface orientations on both sides of a paper web.

Figure 2 shows a top view of the second edge region of the headbox 30 applying the method according to the invention.

Figure 3 shows the same as Figure 2 seen from the side.

Fig. 4 shows the same as Figs. 2 and 3 as seen from the direction 35A (machine direction) indicated in Fig. 3.

85732 6

Figure 5 is a schematic side view of an embodiment of the invention using manifolds and then control valves in manifolds.

Figure 6 shows the same as Figure 5 seen from above.

The headbox 10 schematically shown in the figures feeds a mass jet onto the forming wire or forming bead. The lip channel 14 of the headbox 10 is bounded by an upper wall 14a and a lower wall 14b. The lip channel 14 terminates 10 in a lip opening 15, the associated tip strip 16 of which adjusts the cross-sectional profile J of the massasus-pension jet. The lip channel 14 is preceded in the feed direction F of the pulp suspension by a turbulence generator with a perforated plate 12 and e.g. a honeycomb 13, the outlet side of which has vertically stepped flow tubes 15 with a rectangular cross-section (Fig. 4). Said flow tubes start from the holes in the grating plate in a circular cross-section and become a rectangular cross-section on the discharge side of the turbo-lens generator 12,13 (Fig. 4). The edge grooves 13j ... 135, to which the additional layered feeds Fx and F5 of the pulp according to the invention are fed, are polygonal in cross-section, as shown in Fig. 4. The turbulence generator comprises, in the pulp suspension feed direction, a first perforated plate 12 preceded by a compensating chamber 11. The pulp suspension flow F is fed from a manifold through a manifold (not shown) to said compensating chamber 11.

According to the method disclosed in FI patent 75377, e.g. the bypass tubes 21 of the pulp suspension 21 are led from both ends of the manifold, passing the manifold and the equalization chamber 11 to the overlapping edge cells 13 ^ .. 135 of both edge regions of the turbulence generator 12,13. The bypass flow pipes 21 leave the joints in the lower walls of the manifold, which are located in the width direction of the headbox at the side walls of the headbox. The flow resistance of the bypass flow pipes 21 is dimensioned so that the bypass flows are preferably provided by the normal pressure difference of the headbox without pumps, which in special cases can, however, be used to obtain sufficiently large flows.

35 85732 7

The edge grooves 26a, 26b disclosed in F1 patent 75377, to which additional feeds according to the method are introduced, extend over the entire height of the flow channel of the pulp suspension at the turbulence generator. In the present invention, which is intended to control the fiber orientation layer-by-layer also in the z-direction of the paper, i.e. in the thickness direction, vertical headbox manifolds 20A.20B connected to the additional feed inlet pipe 21 are used. / F5, which each flow Fx-F5 discharges in both edges of the headbox at each edge region 131 ... 135 as best seen in Figure 4.

Of Figures 2-4 according to a further feeds introduced into the direction of arrow Eng the vertical direction 23 through the control valve to the inlet headers 20, 15 which uses a bypass flow F out through the bypass pipe 22 in the direction of arrow F out. Bypass flows Fout are controlled by other control valves 24.

According to Fig. 1, the method is controlled by an on-line control system comprising a control unit 30. The control unit 30 receives measurement signals mx and 20 m2, which describe the fiber orientation distributions of the paper web U1 measured by the drying section. The upper side of the paper web W x x kuituorientaatiojakautumaa measured e.g. a laser sensor 31 for detecting the polarized light applied to the paper Rx influence of the reflected light R2. The corresponding measuring device 32 is located below the paper web Vx. The measuring devices 25 31.32 traverse in the direction T over the entire width of the web Wx. The above-mentioned fiber orientation measuring devices 31 and 32 are commercially available. The control unit 30 provides control signals cx and c2 to the control valves 23 and 24. The first control valves 23 control the orientation profile of the web W to be produced and its shape in the transverse direction of the paper web and the second valves 24 control the similarity the mutual distribution of the flows F ^ .- Fs.

Here again, it should be emphasized that the additional feeds 35 and manifolds 20 shown in the figures are on both edge regions of the headbox turbulence generator, although only Figures 1 and 6 show both edge areas of the headbox. The dividers 20A, 20B of the two edge areas are preferably identical to each other so that the additional feed structure arrangement is symmetrical with respect to the vertical (machine direction) vertical center plane of the web W.

5

The various structural variations shown in Figures 2-6 are described in more detail below. According to Figures 2, 3 and 4, the manifold 20 is vertical and the tubes 25 exit from the vertical wall on its headbox side, connecting the manifold to the overlapping flow cells 13i ... 13s (Figure 4), 10 where the flows F1 .- Fs turn transversely in the machine direction as shown in Figure 2. . Figure 4 shows the discharge side 13a of the cell 13 of the turbulence generator. The cells are in vertical phase shift. The honeycomb 13 is bounded by horizontal partitions 17 and vertical walls 18. The outlet side 13a of the honeycomb 17 has short lamellae 19 extending over the entire width of the machine.

By controlling or manually adjusting the valve 23 by the signal Cj, the plane of the overlapping bypasses Fj ^.-Fs and thereby the shape of the orientation profile in the transverse direction 20 of the paper web W is uniformly influenced according to the principles disclosed in FI patent 75377. By adjusting the valve 24 in the bypass tube 22 by signal c2 or manually, it is mainly influenced by the mutual distribution of the flows F1 ... FS so that the flows affecting the fiber orientation profile of the upper and lower surface of the web and the middle layers are differentiated so that the achieved orientation layered the distribution is realized.

Figures 5 and 6 show an embodiment of the invention in which the turbulence generator of the headbox 10 consists of a perforated plate 29 with a smaller diameter perforation 28 on the compensating chamber 11 side which opens into a larger diameter perforation 27a on the discharge side of the perforated plate 29 through. From the manifolds 20A.20B, adjustable flows Fout-Fin are fed at both edge regions of the headbox, from which the layer-adjustable flows 35 F1 / F2 / F3 are taken. Said edge flows F1 (F2, F3) are controlled by control valves 271 (272 and 273) 85732 9 fitted to the manifolds 261 (262 and 263) connected to the wall of the manifolds 20A.20B. Said edge flows F1pF2 and F3 are between the flexible hetulalevyt 19a and 19b, which extend in the headbox over the entire width. Those edge flow-5 of F3 to manage the formed paper web W, the underside of the fiber orientation bias, adjustable reunavirtauksilla F2, the paper web W in the middle layer of fiber orientation bias and adjustable reunavirtauksilla F3 paper web W and the upper side of the fiber orientation bias.

10

The structure shown in Figures 5 and 6 can be advantageously implemented in such a way that the inlet headers 20A.20B is connected to the two manifolds 261 and 262, wherein the paper only the top and bottom side fiber orientation bias is controlled separately.

15

The embodiment shown in Figures 5 and 6 is further advantageous in that flexible lip plates 19a and 19b are used in the lip channel 14, which divide the lip channel into overlapping subchannels 141, 142, 143. The needle plates 19a, 19b preferably extend close to the lip opening 15, thus providing an advantage. -Fn flow profiles are well preserved up to the lip jet J without mixing.

The following claims set forth within the scope of the inventive idea as defined by the various details of the invention may vary and differ from those set forth above by way of example only.

Claims (10)

A method in the inlet carriage of a paper machine for controlling the fiber orientation of the paper web (W), in which method one conducts 5 additional currents (Fin-Fout) on both opposite edge portions of the inlet sliding flow channel, in the flow direction (F) which travels in inlet tubes, to edge passages (13x5; 26) at the turbulence generator (12,13) which precedes its lip portion (14,15,16) and by which method one is controlled by controlling the size of and / or the mutual relationship between the 10 the currents generate transverse flow velocity in the lip current of the inlet carriage which compensates for a distortion of the fiber orientation, characterized in that to control the thickness-oriented (z-directional) orientation of the paper (W) produced by the paper machine connected to the sealing device connected to it F1 / F2 / F3 / F4 / F5) of said auxiliary currents layered in the thickness direction on both edge regions of the inlet carriage. Process according to claim 1, characterized in that water and / or pulp suspension are used as extra streams. 20 3. A method according to claim 2, characterized in that the pulp suspension of the extra currents is taken from the inlet carriage's mass-current before the turbulence generator (12,13) and that the extra currents are achieved with the normal pressure difference of the inlet carriage without pumps. 25 4. A method according to any one of claims 1-3, characterized in that said auxiliary currents are distributed in mutually arranged edge channels (13, 135) by the turbulence generator (12,13) in the thickness direction of the paper web (W), using 2 -10, most preferably 3-6, 30 channels on each other. Method according to any of claims 1-4, characterized in that the orientation profile of the web (W) produced is controlled by the control signal (cj) of the automatic control system or manually by using first control valves (23) of the extra supply pipes. (21) and the web shape in the transverse direction of the paper web (W) 85732 and that at least other control valves (24) regulate the mutual similarity of the orientation profiles above or below the paper web (W) by controlling the mutual distribution of the currents (Fj-F5). which comes to the different layers of paper. 5 Method according to any of claims 1-5, characterized in that the method uses the tapered distribution beams (20a, 20b) in the flow direction (Fln-Fout) of the extra currents, whereby through flow channels (25 ; 26) which opens into the wall of the distribution booms conducting edge currents on both edge regions (131 ... 135, 261 ... 263) of the housing plate (29) or the cell system (13) of the turbulence generator (12,13) (Figs. 2 , 3 and 4). Method according to any one of claims 1-6, characterized in that a method (20A, 20B) of distribution beams for the edge currents is used in the process, with a wall (26x, 262,263) of distribution tubes joined to it. , which is provided with a series of control valves (27j.272.273) which control the edge currents (Fj / F2 / F3) by which the distribution (Fj / F2 / F3) of the extra currents in layers is regulated (Figures 5 and 6). 8. A method according to any one of claims 1-7, characterized in that the method uses either such a turbulence generator having a heel plate (12) and a cell system structure (13) as an extension thereto. starting with a circular cross-section and ending (13a) with a rectangular cross-section and feeding the edge passages (13j ... 135) formed by the pipes of said cell system construction (13) from said edge streams (Fj.F2.F3) the boom (20) or the like and that the turbulence generator is constituted by such a heel plate (29) having a small cross-section perforation (28) which is connected to a perforation (27) of a larger cross-section by means of a step-down part (27a). wherein the edge currents are measured from a pair of distribution beams (20A.20B) or equivalent via the tubes (26) to the edge passages (26; 28). 35 85732 9. A method according to any one of claims 1-8, characterized in that said edge currents are directed to both edge regions of the inlet carriage to flow channels (14j, 142, 143) of the lip part (14) of the inlet carriage which are separated from each other. teachable flexible disc tabs (19a, 19b). Method according to any one of claims 1-9, characterized in that the method measures, most preferably in the area of the drying section of the paper machine, the fiber orientation profiles of the upper side and the lower side of the paper (Μχ), and thus measuring signals are obtained ( m1, m2) which is directed to the control system (30), which gives control signals (c1, c2), by which said edge currents and their layered distribution are regulated in the thickness direction of the paper (Figure 1).