MULTI-LAYER HEADBOX FOR A PAPER MACHINE/BOARD MACHINE

Abstract: The invention concerns a multi-layer headbox (10) for a paper/board machine, comprising stock inlet headers (J1, J2...) for the stocks (M1, M2...). The inlet headers communicate with a tube tank (11) and through the tube bank with an intermediate chamber (E1, E2...), from which the stock flows further into the turbulence generator (12) and through the pipes (12a1.1, 12a1.2..., 12a2.1, 12a2.2...) in the turbulence generator (12) further into the slice cone (13) and onto the forming wire (H). The multi-layer headbox comprises, across the width of the headbox, distribution valves (V1, V2...) for dilution water, each of which distribution valves (V1, V2...) communicates with a distribution plate (16) placed in connection with the tube bank (11), in which connection, from one valve (V1, V2...), the dilution liquid is distributed at the same time to at least two of the stocks (M1, M2...) that from the different layers of the web in the multi-layer headbox.

Description: Multi-layer headbox for a paper machine/board machine The invention concerns a multi-layer headbox for a paper/board machine. With respect to the prior art, reference is made to the solutions in EP 634,523 and in DE 44 35 860 and DE 44 16 909. From said publications, on the whole, the use of dilution liquid is known in connection with a multi-layer headbox in order to regulate the basis weight of a multi-layer web across the web width. When multi-layer paper is produced, one of the main requirements is purity of the layers. In the present patent application, a novel construction of a multi-layer headbox is described, which is suitable both for paper machines and for board machines. In accordance with the invention, it has been realized to construct the multi-layer headbox so that it comprises separate inlet headers of their own for each stock and, after them, a common distribution plate, through which the dilution liquid is distributed to the desired portions of the web width and, preferably at the same time, into all of the layers in view of regulating the basis weight of the web across the web width. Further, preferably the same amount of dilution liquid, favourably dilution water, is passed into each layer. Since, in the construction of a multi-layer headbox in accordance with the invention, for regulation of the dilution liquid, in each zone of regulation across the width, one valve only is needed, the solution becomes less expensive and simpler, compared with the prior-art solutions. In the solution in accordance with the invention, the layers can be made stable, in which connection even partial mixing together of layers of different consistencies is prevented. Thus, in the solution in accordance with the present invention of ours, the layers remain in equal proportions, which is important when the individual layers are thin, which is the case with printing papers. The optimal field of application of the invention is a 3 -layer headbox in the manufacture of printing papers. Further, in accordance with the invention, the construction of the headbox is such that the constructional portions corresponding to its individual layers are equal to one another both in respect of the numbers of pipes and in respect of the cross-sectional shapes of the pipes, in which case the flow velocities become equal in each layer. Thus, since the flow velocities in each layer are substantially equal, no impurity of layers, arising from differences in flow, occurs. Further, in the construction in accordance with the invention, between the layers, in the slice cone long aprons are used which become narrower towards their ends and extend substantially over the entire length of the slice cone. Further, in each layer, between the horizontal rows of pipes, intermediate aprons are used which become narrower towards their ends. In a multi-layer headbox in accordance with the invention, preferably a what is called single-stock system is employed. The stock is passed from one common tank and branched into branch ducts, in which the fillers/admixtures required by each layer are added to the basic stock. In a multi-layer headbox in accordance with the invention, there are at least two layers, preferably three. There may also be more than three layers. The multi-layer headbox in accordance with the invention is mainly characterized in what is stated in the patent claims. The invention will be described in the following with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying drawings, the invention being, however, not supposed to be confined to said embodiments alone. Figure 1A is a longitudinal sectional view of a multi-layer headbox in accordance with the invention. Figure IB is a sectional view of the construction shown in Fig. 1A viewed from the top and taken along the line I— I in Fig. 1A. Figure 2A is an illustration on a larger scale of the supply of dilution liquid into the multi-layer headbox in accordance with the invention into connection with the distribution plate common of its different layers. Figure 2B is a sectional view taken along the line II— II in Fig. 1A. As is shown in the figure, the dilution flow is distributed from the narrowing duct at the same time into all the flow pipe components that form the different layers in the multi-layer headbox in each vertical row of pipes. Figure 3 illustrates the stock system employed in the multi-layer headbox in accordance with the invention. Figure 4A shows a second preferred embodiment of the invention. Figure 4B is a sectional view taken along the line III— III in Fig. 4A. Figure 5A shows an embodiment of the invention in which the dilution liquid is passed at the same time through the same valve into one surface layer and into the middle layer in a three-layer headbox. Figure 5B is a sectional view taken along the line IV— IV in Fig. 5 A. Fig. 1A is a longitudinal sectional view of a multi-layer headbox 10 in accordance with the invention for a paper/board machine. The multi-layer headbox shown in the figure comprises three stock inlet headers: the headers J j ,J 2 , T 3 for the stocks Mi ,M 2 and M 3 . Each stock M 1 ,M2,M 3 is fitted to be passed from the inlet headers J j ,^ and J 3 so that the stocks are not mixed with each other but that three separate web layers are formed. As is shown in Fig. 1A, the dilution liquid, preferably dilution water, is passed out of its header T through the valves Vi and/or V 2 and/or V 3 ... connected with the header into the ducts D j and/or D 2 and/or D 3 connected with the valves selectively. In this way, by regulating the valves Vi and/or V 2 and/or V 3 ... , it is possible to regulate the flow of dilution liquid, preferably dilution water, across the web width. The concentration of the dilution liquid, preferably dilution water, differs from the average concentration of the stock suspension. In this way the basis weight of the web can be regulated in the desired mode across the web width. This has been achieved so that the stocks Mι ,M 2 ,M 3 are made to flow out of their inlet headers J j .J2.J3 into the tube bank 11 placed after the inlet headers, into the individual tubes lla j ,lla j 2 ... ;lla 2 j , lla 2 2 ... in the tube bank and further, out of said tubes in the tube bank 11 into intermediate chambers Eι ,E 2 ,E 3 related to the stocks Mι ,M2 and M 3 , and out of the intermediate chambers E j ,E2,E 3 into the turbulence generator 12, into its pipes 12a j , 12a 2 ... ;12a 2 ι , 12a 2 2 ... , and further into the slice cone 13, which comprises aprons 14aι ,14a 2 which extend substantially over the entire length of the slice cone 13. Further, in the slice cone 13, between the two pipes in the vertical row in the slice-cone block or layer provided for each stock Mι ,M 2 ,M 3 , an intermediate apron 15a 1 ,15a 2 , 15a 3 has been fitted, which is substantially shorter than the aprons 14a 1 ,14a 2 that are placed between the blocks and divide the blocks and that extend substantially over the entire length of the slice cone 13 and become narrower towards their ends. In the headbox in accordance with the invention, by means of the inlet plate 160, the stocks Mι ,M 2 and M 3 are passed out of their headers Jι ,J 2 and J 3 , in the way indicated by the arrows L 2 ',L 2 " and 2"', into the flow pipes 16aι ι ,16a j 2 ... ; 16a 2 2 , 16a 2 2 ... in the inlet plate 160. From the plate 160 the flow is passed into the ducts provided with corresponding numerals in the distribution plate 16, and in said distribution plate 16 the dilution liquid Li is divided into each pipe in the vertical row of pipes so that the dilution liquid L j is divided uniformly into all of the stocks M j ,M 2 and M 3 . From the distribution plate 16 the combined stock flow and dilution water flow is passed into the tubes 16a ι ,16aι 2 ... ; 16a 2 ι , 16a 2 i- - . in the tube bank 11. From the tubes in the tube bank the stocks Mi ,M 2 and M 3 and the dilution flow Li combined with them are passed into the intermediate chamber compartments E j ,E 2 and E 3 . The intermediate chambers E! ,E 2 and E 3 are separated from one another in the vertical direction by means of horizontal walls gj and g 2 extending across the width of the headbox. From the intermediate chamber compartment E the stock is passed into the pipes 12aj j,12a 2 - • • ; 12 2 , ι , 1 a 2 2- - - ; 1 &3 ι,12a 3 2 ... in the turbulence generator 12. From the middle compartment E 2 the stock is passed into the middle pipes 12a 1 3 ,12a j ; 12a 2 3 > 12a 2 4... in the turbulence generator 12, and from the compartment E 3 the stock is passed into the pipes 12aι 5 ,12aι 6 ; 12a 2 5, 12a 2 g... in the turbulence generator 12. From the turbulence generator 12 the stocks M j ,M 2 and M 3 and the dilution waters added to them are passed further into the spaces between the main aprons 14aι , 14a 2 in the slice cone 13 and further onto the forming wire H. In a headbox in accordance with the invention, it is further possible to use an adjustable top slice bar K at the end of the slice cone 13. As is shown in the figure, the inlet headers J1 2 3 form a construction enclosed by a unified frame R. Between the inlet headers Jj and J 2 there is a partition wall C1 passing horizontally in the figure between the frame R and the inlet plate 160. Similarly, between the inlet headers J 2 and J 3 there is a horizontal partition wall C 2 passing between the frame R and the inlet plate 160. The figure illustrates a headbox by whose means it is possible to manufacture three- layer paper. It is obvious that the invention is not supposed to be confined to the embodiment described above only, but the headbox may also consist of a construction unit that manufactures two-layer paper and comprises two inlet headers J j and J 2 only. In such a case the distribution plate 16 divides the dilution liquid into the stocks M j and M 2 . It is obvious that the invention is also suitable for use in multilayer headboxes in which there are more than three inlet headers Jι ,J 2 ,J3,J 4 ... for more than three different stocks M 1 ,M2,M 3 ,M 4 ... Fig. IB shows the construction of Fig. 1A viewed from above. As is shown in Fig. IB, the dilution liquid is distributed through the valves V j , V 2 ... V N (in Fig. 2B) into the multi-layer headbox in accordance with the invention into different points of width of the headbox into the vertical ducts 17a 1 ,17a 2 ... and further into the tubes 16a, ι ,16a j 2 - - - ; 16a 2 ι ,16a 2 2 - - - m view of regulation of the basis weight of the web. The dilution liquid can be dilution water, for example fibrous or clear water or water taken from the wire as retention. As a rule, the concentration of the dilution liquid differs from the concentrations of the stocks M j ,M 2 and M 3 . In accordance with the invention, the dilution liquid (arrow L j ) is distributed through a valve V j ,V 2 ... (in Fig. 2B) placed at each point of width into connection with the multi-layer headbox 10 to a certain point of width into all the layers in the multilayer headbox 10, i.e. both into connection with the stock M shown in the figure and into connection with the stock M 2 and into connection with the stock M 3 to regulate the basis weight of the multi-layer web to be formed across the web width. Fig. 2 A is an illustration on a larger scale of the supply of the dilution liquid into a multi-layer headbox in accordance with the invention. As is shown in Fig. 2 A, a separate distribution plate 16 is employed, which is fitted after the inlet headers J j ,J 2 and J 3 in the stock flow direction L2 ahead of the tube bank 11. In front of the distribution plate 16 there is an inlet plate 160. Said separate distribution plate 16, which is fitted in connection with the tube bank 11, comprises flow ducts 17a j , 17a 2 ... narrowing in the direction of flow of the dilution liquid. The dilution liquid Li coming from the flow duct D j and from the valve Vi ; from the flow duct D 2 and from the valve V 2 , etc. flows into the connected narrowing duct 17aι ,17a 2 ... , from which the flow is distributed further, at the same time, into all of the tubes 16a ι j , 16a 2 . ■ • ; 1 a 2 1 , 16a 2 2- • • in the vertical line of tubes connected with each particular valve Vι ,V 2 ... In this way, through the duct 17a 1 ; 17a 2 ... connected to the outlet side of one valve V ,V 2 ... at the distribution plate 16, the dilution water is distributed into all the stocks M 1 ,M 2 and M 3 in the multi-layer headbox. Fig. 2 A shows the duct 11 aγ connected with the valve V j partly in section, which duct becomes narrower towards its end. By means of said narrowing shape, the flow can be distributed in the desired way and preferably uniformly into all the flow tubes 16a j j ,16a j 2 and 16aι 3 in said vertical row of tubes. Similarly, through the valve V 2 , the dilution liquid is distributed into the tubes 16a 2 ι ,16a 2 2 and 16a 2 3 etc. Fig. 2B is a sectional view taken along the line II— II in Fig. 1A. In the way shown in Fig. 2B, the branch ducts 18a j j , 18a j 2 ,18a j 3 ... are opened into the narrowing duct 17a j . In the way shown in Fig. 2B, the branch duct 18a j j distributes the flow L j from the narrowing duct 17a j into the tube 16a j j of the stock M j , and similarly the branch duct 18a j 2 distributes the flow L j of dilution liquid from the narrowing duct 17a into the tube 16a j 2 of the stock M 2 , and similarly the branch duct 18a 1 3 distributes the flow from the narrowing duct 17a j , from its lower end, into the tube 16a j 3 of the stock M 3 . As is shown in Fig. 2B, the arrow L j illustrates the introduction of the dilution flow from the valve V into the narrowing duct 17a , and the arrows illustrate the distribution of the dilution flow into connection with the flows L^'.I^" and L2"' that come from the inlet headers J j .J2. 3 of the stocks M .M2.M3. The headbox 10 is a construction in which the pipe systems and the headbox constructions related to the treatment of each stock M j .M2.M3 are similar to one another, for example, in respect of their pipe numbers and pipe sizes. In this way differences between the flow velocities in the different layers are excluded, which differences would further result in impurity of layers. For example, the number of tubes provided for the stock M j in the tube bank 11 is equal to the number and size of tubes provided for the middle stock M 2 , and similarly the number and size of the tubes for the stock M 3 of the other surface layer are equal to those of the preceding layer. Similarly, the constructions provided for the stocks M j ,M 2 and M 3 are similar to one another at the intermediate chamber and the turbulence generator. The aprons 14a ,14a 2 in the slice duct extend preferably over the entire length of the slice duct and become evenly narrower towards their ends. Further, in each layer in the slice duct 13, the headbox in accordance with the invention comprises intermediate aprons 15a j , 15a 2 ,15a 3 , which are substantially shorter than the main aprons 14a j , 14a 2 . Fig. 3 illustrates the single-stock system connected with the multi-layer headbox in accordance with the invention. The stocks M j ,M 2 and M 3 to be passed into the inlet headers J ,J 2 and J 3 have been brought from the same stock tank F placed in connection with the multi-layer headbox. The stocks M j ,M 2 and M 3 have been formed out of one common basic stock M by to the basic stock M adding the admixtures/fillers required by the layers and, thus, by each individual stock M j ,M 2 and M 3 . Thus, the basic stock M is passed from the stock tank F by means of a pump P and branched into the branch lines e ,e 2 ,e 3 ,e4,e 5 , after which the fillers and/or retention agents are added at the points b j and b 2 in compliance with the requirements of each stock M j ,M 2 and M 3 . Figs. 4 A and 4B illustrate an embodiment of the invention in which the dilution liquid is passed from its header T through the set of valves V j , V 2 ... into the ducts D , D 2 ... and to the desired locations along the width of the headbox, always depending on the regulation setting of the valve V , V 2 ... The dilution liquid, preferably dilution water, is passed at the same time, for example, in the way illustrated in Fig. 4A, through the duct D j into connection with the stock flows L2' and L2'" passed from the stock inlet headers J and J 3 . Thus, as is shown in the figure, for example, the dilution flow L is passed through the duct D j out of its header T, at the same time, through one regulation valve (the valve V j as shown in the figure), into at least two stock layers, in the way shown in the figure, into connection with the stocks M j and M 3 that form the surface layers in the three-layer headbox. The stock M 2 is passed out of its inlet header J 2 as the flow L^" so that, in the embodiment shown in the figure, no dilution liquid L j is passed into connection with said middle flow L 2 ". Thus, as is shown in Fig. 4A, the dilution liquid L is first passed into the duct D j out of its header T, and after that through the duct 16 into the narrowing duct 17a j and from it through the branch ducts 18a j j and 18a j 3 into the stock flows L 2 ' and L2"' of the stocks M and M 3 flowing in the ducts 16a j j and 16a j 3 . Thus, it is an essential feature of the embodiment of Figs. 4 A and 4B that the dilution liquid L j is passed, being regulated by one regulation valve V j and/ or V 2 ... and/or V 3 ... and/or V n , into the duct D j and/or D 2 ... connected with said valve, and said dilution liquid is passed out of its header T, at the same time, into at least two stock layers and, in the embodiment shown in the figure, into connection with the stock flows L 2 ' and L 2 '" that form the surface layers M j and M 3 in the three-layer headbox. The stock flows L2' and L2"' are passed into the ducts 16a j j and 16a j 3 out of their inlet headers J and J 3 , and in said ducts 16a j j and 16a j j the dilution liquid L j is passed, in the way shown in the figure, out of the narrowing duct 17a j into connection with said flows L 2 ' and L 2 '". The combined flow of stock flow and dilution liquid is passed further into the tube bank 11 and further in the headbox construction. Figs. 5A and 5B show an embodiment of the invention which is in other respects similar to the embodiments shown in the preceding figures, but in which the dilution liquid L is passed into connection with the flow L2' of the stock M j that forms a surface layer and into connection with the flow L 2 " of the stock M 2 that forms the middle layer. In this embodiment, no dilution flow L j is passed into connection with the stock flow L2'" . Also in this embodiment, there is a set of valves V , V 2 ... fitted across the width of the headbox, in which case the dilution flow L j is passed from the header T of the dilution liquid, preferably dilution water, in the desired way through the valve V j and/or V 2 and/ or V 3 ... into the connected duct D j and/or D 2 ... and further into the narrowing duct 17a j and/or 17a 2 , and from said duct the flow is branched at the same time into connection with the flows L2' and L2 " of the stocks M and M 2 passed from the stock inlet headers J j and J 2 .

Claims: Claims 1. A multi-layer headbox (10) for a paper/board machine, comprising stock inlet headers (J j ,J 2 - •) for the stocks (M ,M 2 ...) > which inlet headers communicate with a tube bank (11) and through the tube bank with an intermediate chamber (E j ,E 2 ...), from which the stock flows further into the turbulence generator (12) and through the pipes (12a j j ,12a j 2 - - - ,12a 2 ι ,12a 2 2- - -) in the turbulence generator (12) further into the slice cone (13) and onto the forming wire (H), characterized in that the multi-layer headbox comprises, across the width of the headbox, distribution valves ( V j , V 2 ... ) f or dilution water , each of which distribution valves (V j , V 2 ... ) communicates with a distribution plate (16) placed in connection with the tube bank (11), in which connection, from one valve (V j ,V ...), the dilution liquid is distributed at the same time to at least two of the stocks (M j ,M 2 ...) that form the different layers of the web in the multi-layer headbox. 2. A multi-layer headbox as claimed in claim 1, characterized in that the flow of dilution liquid, preferably dilution water, is distributed from the inlet header (T) for dilution water selectively through the valves (V j and/or V 2 and/or V 3 ...) into the connected ducts (D j and/or D 2 and/or D 3 ...) and further into connection with the flow (L2') of the stock (M j ) that forms a surface layer in the dilution headbox and into connection with the other surface layer (I^"') * in which connection no dilution liquid, preferably dilution water, is distributed into connection with the flow (L2'.') of the stock (M 2 ) that forms the middle layer. 3. A multi-layer headbox as claimed in claim 1, characterized in that the dilution liquid, preferably dilution water, is passed selectively through the valves (V j and/or V 2 and/or V 3 ...) into the duct (D j and/ or D 2 and/ or D 3 ...) connected with the valve, the dilution liquid being distributed in a three-layer headbox, which comprises stock inlet headers (J , J 2 , J 3 ) for three stocks (M j , M 2 , M 3 ), into connection with the flow (L j ') of the stock (M j ) that forms one surface layer and, at the same time, through the same valve, into connection with the flow (L 2 ") of the stock (M 2 ) that forms one middle layer in the web, and that no dilution liquid is distributed into connection with the flow (L 2 '") of the stock (M 3 ) that forms the other surface layer. 4. A multi-layer headbox as claimed in claim 1, characterized in that the multi- layer headbox comprises a distribution plate (16) common of all the layers and, in said plate, ducts (17a j ,17a 2 ...) connected to the valves (Vj,V 2 ...), in which connection, from each duct (17a j ,17a 2 ...), there are branch ducts (18a j ,18a j 2 ... ; 18a 2 , 18a 2 2- • •) P ass ing into all of the stock flow pipes (16aj j,16aj 2- • • ; 16a 2 , 16a 2 2- - -) in the corresponding vertical row, in which connection the dilution liquid is passed from the branch duct (17a j ,17a 2 ...) connected with each valve (V j ,V 2 ...) at the same time into all the stocks (M ,M 2 ,M ...) that form the different web layers in the multi-layer headbox. 5. A multi-layer headbox as claimed in any of the preceding claims, characterized in that the slice cone (13) comprises aprons (14a j ,14a 2 ...) that extend over the length of the slice cone between the different layers. 6. A multi-layer headbox as claimed in claim 5, characterized in that in the groups of tubes that form each web layer there is additionally a shorter intermediate apron (15a j ,15a 2 ...). 7. A multi-layer headbox as claimed in any of the preceding claims, characterized in that the structural components that form the different layers in the multi-layer headbox, such as the tubes in the tube bank, are similar to one another, in which connection the velocities of the stock flows in the different layers are equal to one another, and differences in speed between the stock flows do not cause impurity of layers. 8. A multi-layer headbox for a paper/board machine as claimed in any of the preceding claims, characterized in that the stocks (M ,M 2 ...) are passed into the inlet headers (J j ,J 2 ...) from the same stock tank (F) placed in connection with or in the vicinity of the multi-layer headbox, and that the separate stocks (M ,M 2 ...) for each layer are formed out of said basic stock (M) by, in the approach lines (e ,e 2 ...) of the inlet headers (J j ,J 2 ...), to the basic stock adding the admixtures/chemicals/- retention agents required for the formation of the different stocks (M j ,M 2 ...).

Inventors: HUOVILA JYRKI, KINNUNEN JUHA, LINSURI ARI, NYBERG PETRI, HUOVILA, JYRKI, KINNUNEN, JUHA, LINSURI, ARI, NYBERG, PETRI
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1997
Main classification: D21F1
IPC codes: D21F1, D21F9