FI118015B - Apparatus in the headbox of a paper machine or the like for adjusting the fiber orientation profile - Google Patents

Description

118015; . f! '.

EQUIPMENT FOR ADJUSTING THE PAPER MACHINE OR SIMILAR BOX-PROFILE PROFILE

The invention relates to apparatus for adjusting the fiber orientation profile of a web in a paper machine or the like 5, which headbox includes: - a manifold and a lip channel, in the transverse direction in which the outermost channels in the headbox are arranged such that the fiber orientation profile of the web is adjustable by varying the amount of dilution and water flow, U.S. Patent 5,843,281 describes a headbox according to the preamble.

It is an object of the invention to provide a novel apparatus for adjusting the fiber orientation profile of a web in the headbox of a paper machine which is simpler and more accurate than before.

It is a further object of the invention to provide a dry web. · To adjust the fresh orientation profile in the paper machine headbox * · * ·> | • a new type of apparatus for easier adjustment of the fiber orientation profile and a simpler structure known in the art. Characteristic of the apparatus of the present invention

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features are apparent from the appended claim 1. The invention is · · ·; In the * headbox, the volume flow of the outermost channels ·· ♦ • · * ... * is changed to adjust the fiber orientation profile. The change in volume flow 30 is unexpectedly achieved by changing the flow rate of the dilution water ··· ** ♦, which is achieved by designing the geometry of the outermost channels • · ·. In other words, the flow rate of the dilution water is changed in the outermost channels by the state of the fiber suspension, *, ···, to obtain the desired fiber orientation profile.

In the apparatus of the invention, the geometry is modified at a given | * channel section, which can be implemented in a wide variety of *. *: in headboxes. In addition, the geometry change can be made in several | differently, but simply. The hardware can! h '·' '\ 2 ·; 118015 also utilizes existing components, reducing hardware acquisition and operating costs.

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

Figure 1 is a side view of the headbox according to the invention, Figure 2a is a sectional view of a second headbox of the invention,

Fig. 2b shows the principal partial magnification of Fig. 2a,

Figure 3a is a sectional view of a first embodiment of a dilution chamber according to the invention, Figure 3b is a sectional view of a second embodiment of a dilution chamber according to the invention,

Figure 3c is a sectional view of a third embodiment of a dilution chamber according to the invention,

Figure 4a is a graph of the change in total flow obtained by geometry 20 of the invention as a function of dilution

Figure 4b is a schematic drawing of a cross section of the tubes: viewed from the machine direction before the dilution chamber,. : Figure 4c shows a schematic drawing of the pipe cross section * · * * ·. · Viewed from 25 machine directions, dilution of the chamber ice • · ·. movement.

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Fig. 1 is a plan view of the • · * "headbox according to the invention, viewed from the side. The headbox includes, at its most extreme parts, a manifold 10 and a lip passageway 11 between the · ·: ** turbulence generator 12. Before the turbulence generator 12, * additionally, a distribution grid 13 for dividing the fiber suspension into a turbulent ·; ··· sigenerator 12. In some headboxes, there may be another distribution grid and a distribution grid before the turbulence generator ···. 35. In addition to the turbulence generator 12, the lip channel 11 is delimited by the upper lip 14 • · · * · and the lower lip 15, between which a lip opening 16 is formed. The turbine 118015: ί · 3 lens generator 12 is connected to a 13 through the manifold 10 and terminates in said lip passageway 11. In practice, the turbulence generator 12 consists of tubes 18. includes dilution means 19 known per se and connected to channels 17 and 17 '. Figure 1 further shows lamellae 20 fitted to lip duct 11 to maintain turbulence up to lip opening 16.

In practice, a fiber suspension is fed from the manifold via a manifold and a turbulence generator into the lip duct to provide sufficient turbulence with the turbulence generator. In addition, the diluent means delivers dilution water to adjust the basis weight profile of the fiber suspension in the transverse direction of the headbox. In other words, the liposuction profile of the liposuction suspension being discharged from the lip orifice is substantially the same across the entire width of the headbox, resulting in a homogeneous end product. Surprisingly, the dilution means further adjust the volume flow of the headbox peripheral channels to adjust the fiber orientation profile of the web. Adjustment is necessary because the lip-20 channel edges slow down the flow in the lip channel. In this case, the fiber suspension tends to settle at a certain angle in the fibrous suspension discharged from the lip opening, which distorts the fiber orientation profile. In other words, the quality of the final product would vary * · · • ·. ·. ; in the headbox width direction without adjusting the flow of the peripheral parts.

In the apparatus according to the invention, the geometry of the outermost channels • · · • · 1 ”is adjusted to adjust their volume flow by adjusting the flow rate of the dilution water. In other words, simply increasing the flow rate of dilution water in the outermost channels will mainly compensate for the distortion caused by friction. • · • · 30 Using dilution water causes the consistency of the fiber suspension at the ends of the headbox to be reduced: * · *: however, since later in the manufacturing process the edge portions of the web are removed.

• ·. . 35 ··· * * As is known in the art of dilution, the geometry of the headbox channels is adapted so that the addition of dilution water does not affect 118015; The four sensors can be adjusted by varying the amount of dilution water without affecting the fiber orientation profile. In the headbox, the geometry of the outermost channels is adjusted such that a change in the flow rate of the dilution water modifies the flow of the fiber-5 pension, in particular its volume flow. Thus, in practice, the volume flow of the outermost channels is dependent on the flow rate of the dilution water. Preferably, the geometry is adjusted as desired by altering the geometry of the mixing region of the outermost channels, whereby the fiber suspension and the dilution water are combined. Preferably, the geometry of the outermost channels is arranged such that the change in flow is substantially directly proportional to the change in the flow rate of the dilution water. The dependence of the flow on the amount of dilution water will be explained in more detail in connection with the description of the structure 15 of the dilution chamber of the mixing zone and Figures 4a and 4b.

Fig. 2a shows a headbox with turbulence generator 12 comprising two rows of overlapping tubes 18. Turbulence generator 12 is provided with a manifold 10 with a flow connection 20 with a manifold 13, which is further provided with a manifold 22 for dilution water D. The tubes 24 of the manifold 13 are supported on the plate preceding the manifold 22. Similarly. . the tubes 18 of the turbulence generator 12 are supported on the next plate from the distribution plate 22 «1 ··. The tubes 24 open as an extension of the distribution channel; 1 to 25 dilution chamber 21 (Figures 3a-c). Pipes 24 and 18 are

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** 1 · additionally axially separated, resulting in dilution water • · 9 + i «»

J ·· · D mixes with the main flow. In this case, the fiber suspension S

• · · • «·! · 1 and the dilution water D are connected, advancing to the turbulence generator ··· * · * ... 1 tube. Figure 2b shows, in principle, the merging of the flows 30. Thus, in the embodiments shown, each channel is comprised of: · · · · ·::! and the dilution chamber between them. Functionally, • 1 · for like parts, the same reference numerals are used. channels

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. ···, is generally referred to as 17, and especially the outermost • · * t1 35 channels with 17 '.

• · * · · 1 · · · · · 1 118 · ·

In the embodiment of Figure 2a, the dilution water D is supplied in a transverse direction relative to the main flow of the fiber suspension S. According to the invention, the geometry of the outermost channels can also be adapted so that the dilution water is supplied parallel to the channels or 5 sides (Figures 3a-c). In this case, the feed direction of the dilution water can be selected in the most advantageous manner. In general, according to the invention, the geometry of the mixing zone is adjusted such that the pressure drop in the flow after the dilution chamber is as high as possible. small. In this case, adjusting the flow rate with the dilution water flow rate is easy and accurate. In Figure 1, a single dilution water channel 25 is provided on top of the manifold 10, from which the dilution water D is led through parallel intermediate channels 26 to each distribution channel 23 and further to the dilution chamber. In practice, each overlapping row of tubes has its own distribution channel and thus its own intermediate channel.

Each intermediate channel 26 further has a control valve 27 so that the amount of dilution water can be adjusted zone by zone along the width of the headbox. In Fig. 2a, the intermediate channel 26 is formed by a flexible hose. The control valve control system is not shown here> · \.

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There are different ways to adjust the dilution chamber geometry. In general, however, the geometry of the mixing region within each channel is arranged differently in the outermost: channels compared to other headbox channels. The figures • ** * · 25 show the outermost channels and their dilution • · * • · * *. chambers that are different from other headbox ducts and • »f dilution chamber. Figures 4b and 4c further illustrate other channels of the headboard · * ". *, From which the outermost channels differ according to the invention. According to the invention, the the diameter of the duct is substantially larger than the preceding section of the duct, thereby avoiding unnecessary stroke *,: ** to maintain the change in volume flow caused by the dilution water • · · Figure 4b shows that before the dilution chamber * * .. ·· 21 the area is smaller than the cross-sectional area of the center tubes 24. Accordingly, it is apparent from Figure 4c that after the dilution chamber 21, the peripheral tubes 18 'have a larger cross-sectional area than the central region. 118015 6: --- The cross-sectional area of the tubes in the pipeline 18. The geometry of the dilution chamber and, more generally, of the mixing zone is determined by all the channel sections which influence the flow combination. miseen.

5 In addition to the distribution channel, the geometry of the mixing zone is particularly influenced by the dimensioning of the manifolds and the pipes of the turbulence generator and their mutual location. Figures 3a-c show some geometries of the mixing zone according to the invention. According to the invention, the portion 28 10 of the channel portion 28 preceding the dilution chamber 21 is smaller than the corresponding channels in the middle region of the headbox. In other words, the bellows tubes 24 are smaller in the outermost channels than in the center of the headbox. Hereby, the flow of the fiber suspension is more restricted than elsewhere, whereby the flow without dilution water at the edges of the headbox 15 is smaller than at the center of the headbox. This is also clear from Figure 4b. In practice, the aim is to control about ± 10% of the flow in the outermost channels, with a stroke prior to the dilution chamber aiming at a 10% reduction and a corresponding increase of 20% in the dilution water. This is illustrated by the graph of Figure 4a, which plots the percentage deviation of the flow rate as a function of dilution. The computational graph shown is ascending, whereby the adjustment can be defined as linear. The aim is also to · β · # ί as steep as possible, so that the amount of dilution water · ·; 25 remains at a reasonable level. Computational graph equals • ·. ·. : A high volume flow rate in all headbox channels is achieved by a dilution ratio of • · · j φ · φ. Correspondingly, an increase of 10% deviation • · · jIV is achieved with a dilution ratio of 30%.

Thus, generally, the portion of the passageways preceding the dilution chamber 21 is at least 15%, preferably at least 25%, · · * ”smaller than the passageways in the middle of the headbox. In order to maintain an advantageous adjustment, according to the invention, the cross-sectional area 35 of the passageway 29 following the dilution chamber 21 is larger than the cross-sectional area of the channels * * *. \ in the center of the headbox. not to strangle unnecessarily.

• · 7 118015 In practice, the outermost tubes 18 of the turbulence generator 12 are larger than the rest of the headbox. This is also clear from Figure 4c. Generally, the portion of the duct following the dilution chamber has a cross-sectional area of at least 50%, preferably greater than 5,100%, than the corresponding portions in the other ducts of the headbox. This geometry provides and maintains the desired dilution water and percentage deviation: sufficient accuracy. In particular, the linearity of equivalence facilitates the design and operation of the dilution water control system.

Figure 3a shows the geometry of the mixing zone in which dilution water is supplied from the side to the mixing chamber 21. In the solution of Figure 3b, the dilution water is supplied to the mixing chamber 21 from above. Dilution water may also be introduced in the direction of the tubes 18 as shown in Figure 3c. The geometry of the mixing zone can also be fine-tuned in various ways. Figure 3b shows a relief 30 at the ends of the dilution chamber 21 of the tubes 24, which increases the flow of dilution water into the tube 18. Correspondingly, the tube 20 18 of Figure 3c has sleeves to provide the throttle 31 required in the tube.

The apparatus according to the invention can be applied to various headboxes. The desired adjustability is achieved simply by replacing the outermost components of the headbox with parts according to the invention. However, it is also possible to use already existing dilution media. Thanks to the geometry of the invention, the feed direction of the dilution water can be freely selected * * * * · 'and increasing the amount of dilution water results in a linear change in the deviation in the outermost channels. In addition, the geometry can be easily fine-tuned in simple ways. Here, the * * • '·· paper machine also refers to paperboard, tissue paper and • · * pulp drying machines.

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Claims (3)

Device in the inlet carriage of a paper machine or equivalent for controlling the web's fiber orientation profile, which comprises an inlet carriage - a distributor (10) and a lip channel (11), - channels (17, 17 ') connected to the distributor (10) and closing in the lip channel (11), and - diluting means (19), which are connected via the dilution chamber 10 (21) to each channel (17, 17 ') for control in the transverse direction of the inlet carriage of the gram weight profile of the fiber suspension (S) as through the channel (17). , 17 ') is measured from the distributor (10) to the lip channel (11), where the channels (17') which are closest to the edges of the inlet carriage '15 are arranged so that the fiber orientation profile of the web can be controlled by changing the flow rate of the dilution water (D), characterized by the geometry of the channels (17 ') closest to the edges of the inlet carriage is arranged such that - the cross-sectional area of the portion (28) of the channel (17') preceding the dilution chamber in the the channels (17 ') which are closest to the edges are at least 15% smaller than corresponding parts of the channels (17) located in the middle area of the inlet drawer, and: - the cross-sectional area of the part (29) of the channel (17') lying; • «: after the dilution chamber (21) in the channels (17 ') which lie * * · ^ • ·, ·. : 25 nearest the edges are at least 50% larger than the corresponding parts of # · · • ·; . ·, The ducts (17) located in the center area of the inlet carriage. • · · ··· · * ·· “• · · • · 2. Device according to claim 1, characterized in that the cross-sectional area of said part (28) is at least 25% smaller than the corresponding parts of the channels (17) which are in the middle portion of the inlet ... . Device according to claim 1, characterized in that the transverse * · · * ... * rivet area of the part (29) of the said channel is more than 100% • greater than the corresponding parts of the ducts (17) contained in the middle portion of the inlet carriage. '·'