FI86087C - Method in paper machine and its inlet box to check the fiber orientation of the web - Google Patents

Description

86087

Method for controlling the fiber orientation of a paper machine and its headbox Förfarande i pappersmaskin ooh dess inloppsläda för att controllera banans fiberorientering 5

The invention relates to a method for controlling the transverse fiber orientation angle profile of a paper web made therein in a paper machine headbox, in which method the pulp suspension flow is directed through the headbox lip channel, from which a lip jet is directed through the lip opening to the forming wire or between the forming wires.

The invention further relates to a paper machine headbox comprising a pulp suspension flow channel having a turbulence generator or the like and then a pulp suspension tapered lip channel terminating in a lip opening whose cross-section is fine-tuned by a tip strip and associated control arms.

As is known, the headbox of a paper machine has a lip channel, which is generally delimited at the bottom by a stationary lower lip beam and on the other side by an upper lip beam fixed by a horizontal joint for pivoting in connection with the upper lip structures. The front edge of the upper lip bar has a tip strip that determines the exact profile of the lip opening in the transverse direction of the machine. As is known per se, the top strip has adjusting devices for raising the lip profile 25. As is already known, the upper lip beam is supported from above by several support arms, usually 4-6. The aim is to arrange this support in such a way that the deflection of the upper lip beam is as small as possible and the fine adjustment of the lip opening profile is usually handled by an adjustable tip strip.

30 It is also known to have headboxes in which the upper lip beam is supported on the arms at both ends, in addition to which various support and deflection compensation solutions, for example operating with hydraulic pressure chambers or hoses, have been used.

The aim is to construct the known headboxes in such a way that it is possible to produce paper which is homogeneous in its basis weight, shape and strength properties over the entire width of the web, from which as little as possible would have to be cut off from the edges of the web. In order to achieve said objects, it is already known to use different additional or exhaust flows at both sides of the headbox lip channel in connection with each side wall, for which reference is made to the applicant's FI patent 75,377 (cf. U.S. Pat. No. 10,468,548).

A particularly important requirement is that the major axes of the orientation distribution of the paper fiber network coincide with the directions of the major axis 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 be substantially the same. Sufficiently accurate implementation of the above requirements over the entire width of the web is often not possible with the above solutions. The diagonal curvature of the sheet and the "fall" of the form stack have been particularly awkward and causing complaints.

20 The problems raised by the applicant have been thoroughly examined by the applicant. In this case, it has been shown that the symmetry required of the fiber orientation requires that it not be finished; at any point of the web, depending on the jet / wire ratio used in the lip jet, a transverse velocity of about 1-3 cm / s is exceeded, which in connection with the web infiltration process is sufficient to deviate the main orientation direction of the fibers from 5-20 ° to the machine direction, causing the above "tipping" 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 parallel flow profile after the turbulence generator.

30 One systematic reason for 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 of 3,86087 is the spillage or spreading of the stock on the flat wire portion 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 for side flow (FI-pat. 75 377) are excellently suitable.

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In the previously known headboxes, the cross-section of the lip channel is measured to be uniformly high in the transverse direction, and it is also known to use, in particular, devices for adjusting the deflection of the upper lip beam so that the lip channel is as constant as possible in the transverse direction. In this regard, reference is made to the applicant's FI patent application 884649, which discloses a paper machine headbox upper lip beam adjusting device, in which or the like via the upper lip bar. 15 Em. In the invention of the FI patent application, it is considered novel that in order to adjust the deflection of the upper lip beam, said shaft pins are arranged to be rotatable by actuators and that the centers of rotation

When the paper web is dried, it shrinks less from the center of the web than from the edge areas, with shrinkage generally being about 4% in the middle and about 5-6% at the edge areas. Said shrinkage profile causes a change in the cross-sectional profile 25 corresponding to the web so that, due to the shrinkage, the dry basis weight profile of the flat web after drying is changed during drying so that both edge regions of the web have a slightly higher basis weight than the central region. Due to the drying shrinkage of the web, the already commonly used basis weight profile adjustment automation sets the headbox top rail more open from the center area than from the edge-30 areas. In addition, when the lip channel is known to be rectangular in the transverse direction, transverse currents are thus generated in the lip jet from the edges to the center, because 4 86087 of the pulp suspension filing from the edge areas of the lip channel is forced to move towards the center of the web. This is adversely manifested in the so-called fiber orientation angle profile. S-form. Attempts have been made to control this problem by adjusting the profile of the top strip straighter, but in this case it has been necessary to compromise the uniformity of the basis weight profile. S A typical example of said S-shape of the directional angle profile of the fiber orientation will appear in the accompanying Figure 1C, which will be described in more detail later.

The object of the invention is to provide such a method and a lip channel of a headbox in connection with a paper machine headbox, with which the above-mentioned S-shape or other profile deviation of the fiber orientation profile can be corrected efficiently and using simple device arrangements.

The object of the invention is to provide such a method and a lip channel in the headbox of a paper machine, in which the so-called The S-shape correction can be carried out without having to compromise, at least to a substantial extent, the straightness of the other profiles of the paper, in particular the basis weight profile.

In order to achieve the above and later objects, the invention is essentially characterized by compensating for the uneven drying shrinkage profile and drying of the pulp suspension jet in the region of the web the basis weight profile is realized.

The headbox lip channel according to the invention, in turn, is mainly characterized in that the free flow cross-section of the lip channel in the transverse direction of the lip channel in its central region is traced about 1-10%, preferably about 2-3%, larger than the lip channel edge regions.

In the invention, the channel height of the lip channel is preferably varied substantially inversely with respect to the transverse drying shrinkage profile of the web.

5,86087

In the invention, the shape of the walls or wall delimiting the lip channel can be adjusted by deflection control devices or the like, or the free flow cross-section of the lip channel can be traced larger in the transverse direction in the central part of the lip channel than in the lip channel edge areas. When drying the paper web, it shrinks less from the center region 5 of the web than from the edge regions, with shrinkage generally about 4% in the center and 5-6% at the edge regions, it is preferable to dimension the free flow cross section of the lip channel in the middle portion of the lip channel about 2-3% larger than the lip channel edge regions.

The invention will now be described in detail with reference to the cross-section of a paper web illustrating the background of the invention and realized by the invention, as well as some application examples of the invention, the details of which are in no way narrowly limited.

Figure 1 shows the different cross-sections of a previously known headbox equipped with a basis weight-15 profile adjustment: curve A shows the cross-sectional profile of the top strip, curve B the cross-sectional profile of the basis weight, curve C the cross-sectional profile of the fiber orientation and the cross-sectional profile

Curves A, B, C and D in Figure 2 illustrate the same profiles as in Figure 1 when simulating the method and apparatus according to the invention.

Figure 3 shows a machine direction vertical cross-section of a lip section of a headbox with which the method of the invention can be implemented.

Figure 4 shows a section IV-IV in Figure 3.

Figure 5 shows a machine direction vertical cross-section of a lip channel implementing the method according to the invention.

Fig. 6 is a schematic section along the line VI-VI in Fig. 5.

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Figure 7 shows a section VII-VII in Figure 5.

Fig. 8 shows, in a manner similar to Fig. 5, a lip section of a headbox implementing the method of the invention, in which one plate lamella with which the invention is implemented is used.

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Figure 9 is a section IX-IX in Figure 8.

Figure 10 is a section X-X in Figure 8.

In the invention, the S-shape of the fiber orientation angle profile described above is corrected from the shape of Fig. 1C to the shape of Fig. 2C by profiling the headbox lip channel 13 so that the channel height H changes substantially inversely with respect to the drying shrinkage profile of the web. This is realized in such a way that the flow cross-section of the lip channel is larger in the central region of the lip channel 13 compared to its edge regions. This can be implemented either with the control devices shown in Figures 3 and 4 or with the fixed structures shown in Figures 5-10. According to Figures 5, 6 and 7, the lower wall 10 of the lip channel is arranged planarly and the upper wall 14 is structurally shaped so that the height R of the channel in the middle is higher than in the edge areas. According to Figures 8-10, a transverse constant height Rq lip channel 20 is used, but is followed by a plate lamella 30 which is thicker in the edge region than in the middle region so that the free channel height in the middle of the lip channel 13 is higher than in the edge regions. As described above, the design of the lip channel 13 anticipates the anisotropy of the drying shrink so that the headbox lip opening 13C can be adjusted to a uniform basis weight profile (curves IB and 2B) 25 in an effort to be more uniform (curve 2A compared to curve IA). The fine adjustment of the basis weight profile is further carried out by a tip strip 12 arranged in connection with the lip opening 13C of the lip channel 13 and the adjusting spindles 12a and adjusting motors connected thereto, for which adjustment there are already known pre-developed methods and devices.

P ': 30 7 86087

Figure 1 shows the cross-sections of a web of a fine paper machine equipped with the control of a previously known basis weight profile in a normal driving situation. When aiming at the rather straight basis weight profile shown in curve IB of the figure, the automatic control of the paper machine sets the headbox tip strip 12 more open in the middle than in the edge areas according to curve A in figure 1. This results in the S-shape of the fiber orientation angle profile described above according to curve C, in which the main orientation varies within ± 6 ° with the main direction being machine direction in the middle of the web and almost machine direction just near both edges of the web.

By means of the method to be described in more detail and the lip channel 13 of the headbox, the web profiles corresponding to Figure 1 according to curves A, B, C and D of Fig. 2 have been realized. In this case, for example, using the devices according to Figures 3 and 4, the normal profile of the tip strip 12 is adjusted to Figure 2A, which implements the basis weight profile of Figure 2B.

Figures 3 and 4 show the structure of the lip portion of the headbox, in which a mechanism for adjusting the shape of the upper lip beam 2 and the cross-section of the lip channel 13 is applied, with which the method and lip channel of the invention can be implemented. The lip portion comprises a lower lip beam 1 and an upper lip beam 2 a lip channel 13 converging in the flow direction F of the pulp suspension and terminating in the lip opening 13 C. A lip suspension pulp jet is discharged through the opening 13C onto the forming wire (not shown). with fine adjustment spindles 12a, shown only schematically by a dotted line in Fig. 3. The upper lip beam 2 is supported at one edge on the upper lip structures 16 by a horizontal joint 15 for rotation around it for basic height adjustment and opening of the lip opening 13C.

Γ 30 8 86087

Fastening flanges 17 with ear pairs 18a, 18b are fastened transversely to the upper side of the upper lip beam 2 in certain transverse directions, e.g. at regular intervals. There are at least three ear pairs 18a, 18b, preferably 5-10, in the cross-machine direction. The ear pairs 18a, 18b have holes in which the pin part 19a, 19b is mounted, the center of rotation of which is indicated by the symbol K0-K (). Said pin parts 19a, 19b are connected by an eccentric shaft pin 21, the center of rotation of which in the hole 20 in the lower end of the support arm 22 is marked KrKj. The eccentric shaft pin 21 is eccentric in dimension E with respect to the center of rotation K0-K0 of the lugs and pin parts 19a, 19b. Attached to the pin portion 19b is an adjusting arm 23, to the upper end of which a transfer screw 24 is attached by a pivot pin 25. The transfer screw 24 is moved by a fine adjustment gear 26a driven by a stepper motor 26 10. The turning sector of the adjusting arm 23 is indicated in Fig. 1 by an angle α, the magnitude of which is preferably about 60 °. When the eccentric shaft pin 21 is turned by the adjusting arm 23 around the center of rotation K0-K0, the support of the upper lip beam 2 changes. at the support arm 22n. When the center of eccentricity is parallel to the support arms 22, the height Rj..Rn of the lip channel 13 at its maximum is at its maximum. In question, there is a four-joint mechanism with articulation points 15, KQ, Kj and articulation points (not shown) with which the upper ends of the support arms 22 are attached to the frame structures 27.

With the four-joint mechanism according to Figures 3 and 4, the deflection of the upper lip beam 2 and thereby the height profile R, ... RN of the lip channel 13 can be adjusted. This adjustment can be described, for example, with respect to the height R i of the lip channel 13 prevailing at the support arm 22n, so that at the adjacent support arms 22η-1 and 22n + 1, where the heights R ^ resp. The support points Rn + 1 remain stationary and the upper lip beam 2 is bent at said fixed support points at the support arm 22n to adjust the local height Rn of the lip opening 13C. The heights R ^ -. R ^ .- Rn 25 define an adjustable profile of the lip channel 13, which in Fig. 4 shows a section · 13A1 in the plane IV-IV indicated in Fig. 3.

If necessary, a measuring arrangement can be connected to the adjustment mechanism according to Figs. 3 and 4, with which the height profile (heights R 1 -Rjj) of the lip channel 13 is measured. This measuring arrangement comprises N pieces of position measuring sensors, which are schematically indicated in Fig. 4 by reference numerals 40j ... 40n. Measurement signals are obtained from the sensor receiver 40, which 9 86087 is fed to the measuring and control block 41, which in turn controls the stepper motors 26 (N pieces). This provides a feedback measurement and adjustment system for the height R (L) (L = width of the lip channel) of the lip channel 13. By changing the set value set Rj ... Rn of the control system, the lip channel profiles required by the method 5 of the invention can be implemented with the system very accurately.

Figures 5, 6 and 7 show some cross-sections of the lip channel 13 with which the method according to the invention can be implemented. Fig. 6 is a section VI-VI in Fig. 5 and Fig. 7 is a section VII-VII in Fig. 5, respectively. The lower wall 10 of the lip channel 13 is straight 10 and the upper wall 14 is curved so that the channel height at the edges Rq = RN is less than the height Rk in the middle of the lip channel 13. . Channel height R ^. ..Rk ... RN preferably changes inversely with respect to the dry matter shrinkage profile of the web, whereby the transverse flows in the lip jet and in the emerging pulp layer can be substantially reduced in order to achieve the objects of the invention. As shown in Fig. 6 15, the profile 14A of the upper wall 14 of the lip channel 13 at the initial end of the lip channel 13 near the turbulence generator 28 is shaped by the curved top wall 14 as described above. The curved profile 14A (full line) of the wall 14 can be implemented either. with a fixed structure of the lip channel 13 or with the adjusting devices shown in Figures 3 and 4.

Instead of the continuous curved profile 14A, the top wall 14 can be constructed structurally without adjusting devices as a broken line profile 14B shown by a broken line by forming the top wall from e.g. three planar parts connected to each other at 14b. One possible approximation in the design of the lip channel 13 is to implement the top wall 14 with dotted lines as the profile 14C shown in Figure 6, which consists of two planar wall portions having an angle 14c on the machine direction centerline of the channel 13.

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According to Fig. 7, the heights RqB = RNB of the edges of the lip channel 13B are smaller than the height RkB of the channel 13 in the middle thereof. Figure 7 shows a cross-section 13B of the lip channel 13 near the lip opening 13C. The lower wall 10 of the channel is planar and - - - the profile 14A of the upper wall 14 is curved or the broken line profiles 14B shown in Fig. 6

30 or 14C equivalent or other profile consisting of planar parts.

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Figures 8, 9 and 10 show an embodiment of the invention in which both the lower wall 10 and the upper wall 14 of the lip channel 13 are planar so that the height Rq of the lip channel is adjusted e.g. by Figures 3 and 4 or other adjusting devices or structurally traced across the width of the lip channel 13 The side walls 29 of the lip channel 13 5 are, as is known per se, planar vertical walls, the height of which decreases linearly from the turbulence generator 28 towards the lip opening 13C in the flow direction F.

According to Figures 8, 9 and 10, a plate lamella 30 is placed in the lip channel 13, the thickness H of which 10 in the vertical direction has been exaggerated in Figures 9 and 10 for the sake of clarity. The plate lamella 30 is fixed in the flow direction F on the inlet side to the trailing edge of the turbulence generator 28. The plate lamella 30 extends over almost the entire length of the lip channel 13 close to the tip strip 12 and the lip opening 13C. The plate lamella 30 consists of a lower flat side 30a and a curved upper side 30b. If necessary, both sides 30a and 30b may be curved 15 or the sides of the lamellae 30 may be formed of two or more planar parts in a manner similar to the top wall profiles 14A, 14B, 14C shown in Fig. 6. According to Figures 9 and 10, the height H of the plate lamella at the edges H0 is slightly higher than its height Hj in the middle of the channel 13. The plate lamella 30 also tapers in the flow direction F so that. the edge dimension H0 shown in Fig. 9 decreases to the dimension H0B visible from Fig. 10, and the average dimension Hj decreases to the dimension H1B, respectively. The lamellae 30 are already known to be used as uniform thickness elements in the lip channel for generating turbulence, a task which the plate lamella 30 profiled in the transverse direction according to the invention shown in Figures 8, 9 and 10 can fulfill if necessary.

By shaping the thickness profile H (L) of the lamella 30 in such a way that the cross-sectional area of the open part of the cross-section of the channel 13 retains the same relative height difference of about 2-3%. in accordance with the invention, the transverse flows originating in the lip channel 13 can be eliminated. If necessary, more than one plate lamella 30 can be used one on top of the other. The invention can also be implemented e.g. by using more than one plate lamella in the edge areas of the lip channel 13 than in the central region of the channel 13, thereby providing transverse profiling of the lip channel 13 11 86087. Instead of the plate lamellae 30 or lamellae, the invention can also be implemented with different strip-like or thread-like hetero-ducts, e.g. a large number of said hetula-ducts placed in the lip channel 13 so that the hetula-ducts are denser in the lip channel edges than in the central areas. L, but the hetero portions of the edge portions have a larger cross-sectional area than the heteroatings of the central region, so that the free flow cross-section of the lip channel can be distributed according to the invention.

It is a particular object of the invention to be able to use as many 10 lip profile 13C profiles as possible, e.g. a profile similar to that shown in curve A of Fig. 2, in order to correct the fiber orientation angle distribution of the lip jet J, e.g. as curve C in Fig. 2. For this purpose, the channel height of the lip channel 13 is preferably changed inversely in proportion to the drying shrinkage profile of the web. In practice, this means that the height H of the lip channel on the center line 15 of the lip channel in the machine direction is about 2-3% higher than in the edge areas of the channel 13. In general, the objects of the invention are achieved when said free channel height on the center line of the lip channel 13 is about 1-10% higher than in its edge areas. The optimal shape of the profile of the lip channel 13 can be determined experimentally and / or by computer simulation.

It is advantageous to connect the method according to the invention and the lip part of the headbox in connection with the use of the side currents disclosed in the applicant's FI patent application 75 377, whereby in most cases the S-shape of the fiber orientation angle can be sufficiently corrected and smoothed.

The following claims, within the scope of the inventive idea defined by which the various details of the invention may vary and differ above only:; by way of example.

Claims (12)

A method in the inlet carriage of a paper machine for checking the transverse angular profile of the fiber orientation of the paper web produced thereon, by which method a pulp suspension stream (F) is controlled via the inlet carriage lip channel (13), from which a lip beam (J) is directed. a lip opening (13C) over a forming wire or a gap between the forming wires, characterized in that it compensates for uneven shrinkage profile formed during the drying of the paper web to be produced and reduces cross-currents in the pulp suspension beams (J) by arranging the flow (13) in the transverse direction is larger at the center region of the lip channel than at the edge regions of the lip channel so that a sufficiently even surface weight profile (Figure 2B) is performed for the web. Method according to Claim 1, characterized in that the channel height (R <) (C)) of the lip channel (13) is changed substantially inversely proportional to the transverse shrinkage profile caused by the drying of the web. A method according to claim 1 or 2, characterized in that at. the method controls the shape of the wall (14) or the walls (10, 14) which restrict the lip channel (13), most preferably the shape of the lower wall (14) of the Upper lip beam (2) supporting the Upper wall (14) of the lip channel (13) with bending control devices (17-26). Method according to claim 1 or 2, characterized in that the free flow cross-section of the lip channel (13) is arranged with fixed structures to be larger in the transverse direction in the middle part of the lip channel (13) than at the edge areas of the lip channel (13). A paper machine inlet carriage comprising a pulp suspension flow channel where there is a turbulence generator (28) or equivalent and then a lip channel (13) that tapers in the flow direction (F) of the pulp suspension, which channel terminates at a lip opening (13). the transverse profile of which is finely regulated with a tip strip (12) and with a series of control spindles (12a) or the like associated therewith, characterized in that the free flow cross-section of the lip channel (13) in the transverse direction of the lip channel in the middle region of the this is arranged to be about 1-10%, most preferably about 2-3%, larger than at the edge areas of the lip canal (17). 6. An inlet carriage according to claim 5, characterized in that the lip channel (13) is limited between the stationary upper and lower walls (10, 14), which walls are formed in such a way that the flow cross-section of the lip channel (13) is greater in the transverse direction. the middle of the lip canal (13) than at the border areas. 7. An inlet carriage according to claim 6, characterized in that in the lip part there is a stationary planar lower wall (10) and a curved or corresponding planar upper wall (14). 15 8. An inlet carriage according to claim 5, characterized in that a disc lamella (30) or a series of disc louvers, whose surface in the transverse direction is larger at the edge regions of the lip channel (13) than is arranged in the lip region, is arranged. • 20 9. An inlet carriage according to claim 8, characterized in that in the lip channel _ · *; (13) there is a disc slab substantially extending over the entire width (L) thereof, the input edge of which is fixed to the output side of the turbulence generator (28) and the disc slab (13) extends close to the lip opening (13C) of the inlet carriage and the height (H,) of the cross-section of the slab (30) is smaller at the center region of the lip channel (13) than at the edges of the slab (30) (height Hq). 10. An inlet carriage according to claim 9, characterized in that said slab lamella (30) has a straight planar longitudinal side (30a) which is most conveniently on the side of the lip-shaped planar lower wall (10) and a curved or corresponding planks. formed Upper side (30b) (Figures 9 and 10). 17 86087 A paper machine inlet carriage according to any of claims 5-10, wherein the upper lip beam (2) which above limits the lip channel (13) is supported by a horizontal link (15) at the inlet carriage body structures (16) and which upper lip beam (14) furthermore is supported by at least three parallel support shafts (22), which support shafts (22) at their lower end are pivotally fixed by means of shaft pins (19a, 19b, 21) and brackets (18a, 18b) or the like at the upper lip beam, characterized thereof, in order to control the profile of the wall (14) bounded by the lip channel (13) by the upper lip beam (2) in the transverse direction, said shaft pins (19a, 19b, 21) are arranged to be rotatable with functional devices (23,24,25 , 26, 26a) and that the pivot centers (Kj-K) of the shaft members (21) supporting the opening (20) at the lower end of the support shaft (22p22N) of the shaft pins (19a, 19b, 21) are eccentric shafts ( 19a, 19b, 21) in relation to the turning center (Kq-Kq) of parts The rods (18a, 18b) which fasten the shaft pins (19a, 19b, 21) at the upper lip beam (2) so that by turning the eccentric shafts with functional devices (23,24,25,26,26a) the profile of the wall is obtained of the lip channel (13) regulated. 12. An inlet carriage according to claim 11, characterized in that the guide shaft (15) of the edge opposite the lip opening (13C) of the upper lip beam (2), the guide points (28) of the upper ends of the support shaft (22) and the eccentric . The centers of rotation (Kq and KJ) of said eccentric shaft pins (19a, 19b, 21), which centers are eccentric in relation to each other, form a four-way mechanism between them, thereby providing a profiling of the wall (14) of the upper lip beam (2). by turning the turning centers (Kq and Kj) in relation to each other. : T: 25