FI97738B - Inlet box in a paper or cardboard making machine - Google Patents

Description

5,97738

Paper or board machine perbox Inloppsl & da i en pappers- eller cardboard mask

The invention relates to a headbox of a paper or board machine, in which the feed points for the additional fluid flow in the direction of flow of the pulp flow upstream of the orifice are located in the direction of means for controlling the supply of water or a non-bulk pulp to the bulk flow, the feed points being auxiliary liquid or pulp supply channels connected to said flow backgrounds, provided with control means such as control valves for supplying additional flows.

In a paper or board machine, an aqueous suspension containing the final fibrous materials 20, hereinafter referred to as pulp, is fed from the mouth of the headbox at the orifice to a forming substrate or wire moving in the feed direction, where dewatering and felting of the pulp into the final product begins.

25 When a wide lip jet from the lip of the headbox is discharged onto the forming base, it spreads from its edges. The spreading causes a transverse flow component in the pulp in the direction of travel of the substrate, which affects the fiber orientation and the surface shape of the finished product. Since the surface weight profile in the transverse direction of the machine is as flat as possible, the lip opening has to be enlarged from the edge area. This, in turn, inevitably causes a transverse flow component in the flow space of the headbox, which is inevitably preceding the lip opening, in the lip channel, which affects the orientation in the same way as the spread of a spray of wire on a wire.

35 • · »e ··. The basis weight profile of the final product is also affected by the subsequent narrowing of the web formed from the pulp fed to the wire as a result of tensile and wear shrinkage. This narrowing is easier to occur at the edges of the web. As a result, the basis weight increases in the edge region. Very close to the edge, this phenomenon compensates for the decrease in surface area caused by the edge effect mentioned in the previous paragraph, but when moving from the edge to the center, the surface weight reaches its maximum, after which it then decreases towards the center. Again, an attempt has been made to compensate for this phenomenon by the arrangement of the lip, which again results in orientation errors.

Efforts have been made to control the spreading of the mass towards the edges after the lip opening with special edge finishes, which, however, have more disadvantages than benefits due to the edge wave they cause.

With regard to the state of the art most closely related to the invention, reference is made to F1 patent application 885684 (J.M. Voith GmbH, v. DE application 3741603).

This application discloses a paper machine headbox as in the preamble of claim 1, in which the diluent is fed into the pulp channel immediately before the throttling point of the turbulence generator. However, this known device has the disadvantage of detrimental flow disturbances, inaccurate and unstable adjustment of the basis weight profile, and in particular the fact that increasing the supply of diluent increases the total flow 20 and causes detrimental transverse flow. There is also the disadvantage of poor mixing of the main flow and the additional flow, which is very detrimental, especially if the consistency differences of the flows are large.

The object of the invention is to provide a headbox which does not have the above-mentioned drawbacks. To accomplish this, the headboard according to the invention is mainly characterized in that said separated flow hoses are post-manifold manifolds, that the chamber where the flow hoses converge is a headbox equalization chamber, coincide with the main mass flow paths at an acute angle from the upstream side of the main mass flow, from the top of the flux, so that the overflow of the mass or liquid replaces the main mass flow, whereby the

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Additional fluid flows are fed to the separated flow paths, such as manifolds, so that each of them mixes with the effect of the flows in the flow paths on the mass flow of its wines at the confluence of the flow paths. The basis weight profile can thus be controlled without disturbing the behavior of the mass as it flows out of the lip opening. The combination of the supplemental fluid flow with the main mass flow then takes place at a sufficiently early stage to allow any transverse flows in the main mass flow to level off, but still close enough to the orifice to allow the additional fluid flow to be controlled. By means of separated flow paths, such as manifolds, the additional liquid flow can be made to mix with the main flow so that at each point the additional liquid flow directed to the main flow acts in a certain area in the width of the headbox.

The additional fluid flow is preferably of such a nature that the consistency of the mass flow decreases. In this case, it can be either water alone or a suspension with a lower fiber concentration than the suspension in the form of a mass flow.

The invention will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 illustrates the use of a pulp jet from an orifice on a subsequent web-forming substrate. schematically shows the lip opening profile used in the prior art perlautsk, 33 Fig. 5 shows in longitudinal section a headbox in which the invention can be applied, Fig. 6 shows a detail according to the invention of the head plate of Fig. 5,

Figure 1 shows a headbox 1 which terminates in the direction of flow of the pulp in a transverse lip opening 2, from which a jet of pulp discharges onto a movable forming base, i.e. a wire 4, passing through a breast roll 3 at the lip opening of the headbox. As the pulp discharges from the lip opening, it spreads at the edges as described by the lateral arrows, whereby both the surface pressure decreases in the edge region of the web formed from the pulp and the orientation of the fibers in this region changes.

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Figure 2 shows the way to influence these phenomena. Here, the width of the lip opening 2, i.e. its dimension in a direction perpendicular to the plane of the wire 4, is arranged larger in the edge region. This is done by lifting the upper lip 2a at the respective edges of the lip opening. In this case, however, a transverse velocity component is generated already in the lip channel before the lip opening 2 and after the lip opening in the wire 4. This phenomenon is also illustrated by the lateral arrows in Fig. 2.

Figure 3 shows the basis weight profile of the formed web in its polk-25 direction, greatly exaggerated. The effect of the drying shrinkage on the surface weight is depicted by broken lines and the actual, final web surface profile is depicted by a solid line showing the edge effect, i.e. the decrease of the surface collar in the edge region caused by the spread of the above-mentioned lip jet.

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Fig. 4 shows schematically and strongly exaggerated the shape of the headbox lip opening 2, which is intended to counteract the distortions shown in Fig. 3. In this case, the width of the lip opening is arranged at a minimum in the central region of the web precisely in those areas between the central region of the web and the edge-35 regions where the maximum edge effect and shrinkage of the finished web surface can be expected. In this case, the transverse currents described by the arrows in the forward direction are again generated, which cause orientation errors. In addition, it is clear from Figure 4 how a special structure and the associated adjustment devices are required for the lip opening, in particular for its upper lip.

Figure 5 shows a longitudinal section of a headbox of a paper and board machine in which the invention can be applied. The headbox 1 comprises a lip channel S in the direction of mass flow immediately before the mouth opening 2, which tapers in the direction of mass flow ending in the mouth opening 2. In connection with the mouth opening there are devices for adjusting the total width of the mouth opening. not included in this section in more detail. The pulp, which is an aqueous suspension containing cellulosic fibers and possibly other substances, is introduced into the headbox 1 as a pump feed by a pulp feed-15 pipe to a manifold 6, from which the pulp flows in a separate of the manifolds 7. The manifolds may also be provided, for example, in two or more overlapping rows extending transversely to the flow, and the invention is particularly well implemented in a box of the tAmA type. However, for the purpose of the invention, it is most essential that at this point the mass flow there are cross-flow paths separated from each other. Through the manifolds 7, the mass flows from the manifolds 6 to the equalization chamber 8, i.e. to the intermediate chamber, where the flows from the different tubes' 25 again coincide with the effect that the flows * discharge from the orifices of the tubes opening into the rear wall of the equalization chamber 8. In connection with the equalization chamber 8 there is a flow from the pressure variation: a compensating nozzle 9 which opens through a channel in the upper wall of the equalization chamber 8. There is an overflow at the top of the air chamber side to drain the excess • 30 mass. The equalization chamber 8 JAike is followed by turbulence. a generator 10 consisting of separated pipes or 9 openings through which the mass flow passes from the equalization chamber 8 to the lip channel 5, the upper wall and the lower wall of which approach each other in the direction of the lip opening 2.

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Figure 6 shows one of the manifolds 7 starting from the manifold in a longitudinal section. According to the invention, a channel 11, 6 y / 0ö is connected to the distribution pipe 7, which is connected to a device for supplying an additional liquid flow to the pulp flow flowing in the distribution pipe. The channel is introduced into the manifold from above and joins the manifold at an acute angle on the inlet side of the pulp flow with a portion of the manifold in the mass flow direction 5 before the stepped expansion 7a, which causes the additional fluid flow to mix well with the pulp flow.

The additional liquid may be a pulp stream consistency, i.e., a fiber-reducing liquid, such as dilute water alone or water, or an aqueous suspension having a fiber content lower than the pulp stream fiber content. The question may include e.g. various waters of the paper machine circulating water system. Naturally, as dilute water as possible is advantageous, because then even very small changes in the water flow rate of this water can affect the consistency of the mass flow after channel 11 in the manifold 7. Devices for supplying additional liquid flow can be located e.g. above or below the rows of manifolds 7.

According to the invention, it is essential that a sufficient supply of auxiliary liquid is arranged in a sufficient number, preferably 20, of each distribution pipe or the like at different points in the transverse direction of the mass flow. In addition, for the control of the basis weight profile, it is important that at least the flow rate of the additional liquid flow to the manifolds 7 or the like is available for each such manifold.

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The auxiliary fluid supply channels and manifolds or the like can also be arranged in such a way that the auxiliary fluid flow replaces the mainstream flow from the manifold to the manifold, whereby the combined flow of In any case, the auxiliary liquid flow supply channels 11 are provided with control means, such as a valve, by means of which the auxiliary liquid flow is supplied, and they can then be connected to a suitable control automation.

As already mentioned above, in order to carry out the invention, there must be a sufficient number of additional liquid flow supply points in the transverse direction of the base plate.

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7 aa. Since there are often two or more overlapping rows of manifolds, it is sufficient to practice the invention to provide one such row with the inlet fluid flow supply channels 11. If there are three or more such rows, these rows with additional fluid flows are most preferably one or more of the average rows. . For example, the rows in question may be the second highest and second lowest rows, for which the channels 11 can be brought from above and below, respectively, as shown in Fig. 5.

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The control of the basis weight profile can be further improved by feeding a thicker mass to the transversely extreme manifolds so that the flow from the manifold to the equalization chamber is thicker than the flow from the other manifolds in the middle. This mass 15 is thicker than the other mass and has a consistency of up to 3 t. This causes the thick mass to form protective walls on each edge region of the web, which prevent the mass from spreading after the lip opening. To achieve this purpose, it is sufficient to arrange one manifold at the narrowest edge in each of the overlapping rows as a separate separate manifold, and these manifolds can also be completely separated from the rest of the mass flow so that the mass flow in them comes entirely from their own thick pulp feeder.

25 The edge area of the web on which the edge formed by the thicker mass is located is trimmed in the normal way into the cam cone by means of edge whistles.

An important advantage of the invention is that the width of the lip opening can be kept constant in the transverse direction of the machine, i.e. the lip opening is made tAy-30 sin straight, so that transverse currents causing orientation errors are not generated.

The invention is particularly suitable for the production of fine papers, where high quality is required of the final product, but it is clear that it can be used in all paper or board machines to improve the quality of the product produced with them.

Claims (7)

97738 8 A paper or board machine headbox in which the feed points of the auxiliary fluid flow 5 are located upstream of the orifice (2) to adjust the entire transverse basis weight profile of the web and at the same time control the flow are in communication with means for controlling the supply of water or a non-mainstream mass flow to the mainstream flow, the supply points being additional fluid or mass supply channels (11) connected to said flow paths (7) and provided with a control member such as control valves for controlling additional flows, that said separated flow paths 15 are manifolds (7) after the manifold (6), that the chamber in which the flow paths converge is a headbox alignment a chamber (8) followed by a turbulence generator (10) before the lip-narrowing space (5), and that the additional liquid or mass supply channels (11) are arranged to coincide with the main mass flow paths at an acute angle from the main 20 inlet side, preferably from above, thus that the additional flow of the additional mass or liquid replaces the main mass flow, so that the combined flow of the main mass flow and the additional flow discharging into the chamber where the flow paths converge is always of the desired magnitude for each flow path. : 25 Headlamp according to Claim 1, characterized in that the additional liquid introduced into said feed channels (11) is a main mass flow-reducing liquid such as dilute water alone or water or an aqueous suspension having a fibrous alum content. 30 less than the gold content of the main mass flow, e.g. a paper machine. circulating water system. m Headlamp according to Claim 1 or 2, characterized in that the width of the lip opening of the headbox is kept constant in the transverse direction of the machine 35, so that transverse currents which cause orientation errors cannot occur. m 97738 9 Headbox according to one of Claims 1 to 3, characterized in that said regulators are connected to an automatic control unit. Headbox according to one of Claims 1 to 4, characterized in that said supply ducts (11) are connected in the incoming direction of the pAA mass flow before the step-like expansion (7a), as a result of which the llsA flows are well mixed with the pAA mass flow. Headbox according to one of Claims 1 to 5, characterized in that a sufficient number of flow supply pipes (11) are arranged in the transverse direction of the headbox and that in a headbox with several overlapping said separated flow paths, additional flow supply pipes (11) are arranged. to several of said rows, preferably to one or more of the middle rows. Headbox according to one of Claims 1 to 6, characterized in that the flow path 20 at least at one end is connected to means for feeding a pulp thicker than the bulk flow. m m m 9 9 m • m 9 • 9 9 9 9 V • * »9 9 9 • • e * 9 · 97738 10