The invention concerns an equipment in connection with the headbox of a paper/board machine for combining a dilution flow with the stock flow passed out of the inlet header in the paper/board machine in order to regulate the basis weight of the paper/board web across the width of the web.

From the applicant's patent applications FI-901593, Fl-933027 and FI-942780 of earlier dates, a what is called dilution headbox is known, which is understood to mean a headbox construction in which the basis weight of the web can be regulated across the web width by through regulation valves passing dilution flows to different areas of width of the headbox and by regulating the quantities of said flows. The dilution flow is mixed with the stock flow passed out of the inlet header of the headbox. The dilution flow can consist of clean or fibrous liquid. Thus, the dilution water can be, for example, white water taken from the web as retention.

It is suggested in the solution in accordance with the present patent application that, in order to regulate the basis weight of the paper/board web, the dilution liquid, preferably dilution water, is passed through valves along dilution liquid ducts to points of different widths in the headbox of the paper/board machine. The regulation of the dilution flow takes place in each dilution liquid duct by means of a regulation valve connected with the duct. It is suggested in the invention that the dilution liquid is passed into separate mixing chambers that, in accordance with the invention, have been formed so that separate, loose, attachable partition walls are used, which walls can have been made favourably by casting or by machining of a metal plate blank, for example by milling or turning on a lathe. Additionally it is suggested in the present patent application that the dilution liquid is passed to said mixing chamber through a separate pipe which opens into the mixing chamber in one or several places. The following advantages are achieved by means of the invention:

— To permit shaping of the flow duct with reasonable costs, among other things, the duct in the flow direction can be shaped as a curved line.

— Partition ribs, i.e. partition walls, can be manufactured by means of a smaller (cheaper) machine tool by casting or by some other method of mass produc¬ tion, in which case need of a machine tool that has large dimensions and that is accurate is reduced.

— The intake pipe of dilution water can also be made as a separate mass product. In this connection, need of a large and accurate (expensive) machine tool is reduced.

— Maintenance (washing) of a separate intake pipe of dilution water is easier than of a machined one (there are always curves in a machined intake duct, behind which curves the washing/checking of the duct is difficult).

— Altering of the flow conditions (tuning) in the headbox is easier afterwards. By changing the dilution water intake pipe (shaping , diameter, turning/size/place of the water discharge openings) it is possible to influence the flow qualities (flow resistance) of the tube bank concerned and, thus, the velocity profile of the headbox and further the orientation profile.

The invention is 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 drawings, the invention being, however, not supposed to be confined to said embodiments alone.

Figure 1A shows the area of the invention, the headbox of a paper/board machine as a side view. The dilution water for regulation of the basis weight of the paper/board web is passed to the desired locations across the width of the headbox, as is shown in the figure, into connection with the ducts in the tube manifold after the inlet header.

Figure IB shows the headbox as an illustration in part viewed from above at the location of the inlet header J _j .

Figure 2 shows a construction in accordance with Fig. IB viewed in the direction of the arrow K _j in Fig. IB.

Figure 3A shows formation of the mixing chamber by means of partition walls that are shaped and separately attachable to the upper and lower plates of the pipe construction.

Figure 3B is a separate illustration of a partition wall module, a so-called rib, of Fig. 3 A. The partition wall module is formed by casting or by some other mass- production method and it is attachable to the grooves in the upper and the lower plate from its shoulders.

Figure 4A shows different partition wall constructions, by whose means the desired mixing of the dilution flow and of the stock flow can be carried out.

Figure 4B is a sectional view taken along the line I— I in Fig. 4A.

Figure 5A shows some alternative modes of formation of the partition wall construc¬ tion.

Figure 5B is a sectional view taken along the line II— II in Fig. 5A.

Figure 6A shows a preferred embodiment of the wall construction in accordance with the invention. The illustration is from above in the area of the inlet header J _j in the headbox.

Figure 6B is a sectional view taken along the line III— III in Fig. 6A.

Figure 6C is a sectional view taken along the line IV— IV in Fig. 6A.

Figure 7A shows a separate, removable mixing/throttle washer that is installable and attachable between the removable, rib-like partition walls, which washer includes a flow opening/openings. The illustration is a sectional view from above at the location of the inlet header J _l .

Figure 7B is a sectional view taken along the line V— V in Fig. 7A.

Figure 7C shows various embodiments of the mixing/throttle washer.

As is shown in Fig. 1A, the headbox 10 of a paper/board machine comprises an inlet header J _j , a tube bank 11 after the inlet header J _j , and after that an intermediate chamber 12. which opens into the stilling chamber 13. After the intermediate chamber 12 there is a turbulence generator G. The pipes G _j J ,GJ ₂ ... of the turbu¬ lence generator G open further to the slice cone 16, which comprises the vanes 17a _j ,17a ₂ , 17a3, as is shown in the figure. The stock is passed further from the slice cone 16 through the discharge gap onto the formation wire H. As is shown in the figure, the discharge gap after the slice cone 16 comprises a top slice bar n and its regulation mechanism 18. The position of the top slice bar n can be adjusted by means of the regulation spindles 19 of the regulation mechanism 18 and by means of the regulation motors 200. The flow of the dilution liquid L _j is adjusted by means of the valves V _j ,V ₂ ... The equipment comprises several distribution pipes D _j ,D ... for the dilution flow across the width of the headbox, in which case the desired dilution flow can be passed to different width points of the headbox and the dilution flow can be regulated at each width point by regulating the valve V _j ,V ₂ ... of the dilution flow.

The dilution flow L _| is passed from the inlet header J _j of the dilution liquid into connection with the stock flow L^ so that the basis weight of the web can be adjusted as desired across the web width.

Fig. IB shows the construction in accordance with Fig. 1A in the area of the inlet header J _j in the headbox viewed from above as an illustration in pan and partly in section.

As is shown in Fig. IB, the dilution flow is passed after the inlet header J _j into mixing chambers S _[ ,S ₂ ,S ₃ ... placed in front of the tube bank 11.

Fig. 2 is an illustration of Fig. IB viewed in the direction K _j .

In accordance with the invention, the partition wall 21a _j ,21a ₂ ... between two mixing chambers can be installed and attached separately, while the construction is assembled, to the fastenings 22a, 22b at the upper plate F _j and at the lower plate F ₂ , preferably to grooves, so that the upper fastening 23a of the partition wall 21a _j , 21a ₂ ... , preferably a shoulder, is fitted into the corresponding fastening 22a of the upper plate F _] , preferably a groove, and the lower shoulder 23b of the partition wall 21a _| ,21a ₂ ... is fitted into the groove 22b of the lower plate F ₂ . In accordance with the invention, the partition wall 21a _j ,21a ₂ ... can be cast. It is an advantage of casting that it is easy to give the mixing chamber the desired shape required by the flow. Thus, the partition wall 21a _j ,21a ₂ ... is a module- like construction component, which can be easily given the desired, curved surface form, which co-operates with the surface form of the other wall at the opposite side of the mixing chamber. Thus, the partition wall 21a _j ,21a ₂ ... is preferably made by casting but it can also be made by machining a separate wall blank so that the desired surface form is machined by means of a machine into the wall blank. The wall blank can also be made by means of some other method of mass production. The wall blank can be installed separate¬ ly, while the headbox is being assembled, in connection with the upper plate F _} and the lower plate F ₂ of the construction in the fastenings 22a, 22b above and below the plates.

Fig. 3 A shows an embodiment of the wall construction on an enlarged scale. The partition walls 21aι ,21a ₂ ... of the mixing chamber S _j ,S ₂ ... are made of removable partition wall modules, which modules are separately shaped into the desired shape

optimal for the flow. Thus, most advantageously, the partition wall can have been made by casting, or it can also have been made out of a separate plate blank by machining (for example milling) the desired surface form to it. As is shown in the figure, the dilution liquid is passed into the mixing chamber from above (or from below) through a separate pipe 24a _j ,24a ₂ opening into the mixing chamber S _j ,S ₂ ...

Fig. 3B shows a partition wall module 21a _j as a separate illustration. The module 21a _t shown in Fig. 3B is a rib-like part which can be installed, by its fastenings, to the plate F _j above the headbox construction to the corresponding fastenings 22a, and to the corresponding fastenings 22b of the plate F ₂ below the headbox. The figure shows a mode of joint construction. It is obvious that a joint can be formed out of a number of different coupling possibilities.

Fig. 4 A shows different partition wall constructions and solutions for the supply of the dilution liquid. Fig. 4B is a sectional view taken along the line I-I in Fig. 4A. As is shown in Figs. 4A and 4B, for example, a throttle point can be formed before the area of inlet for the dilution liquid (chamber S _j ) so that a shoulder d is shaped on the module-like partition walls 21a _j ,21a ₂ ... Thus, when the partition wall modules

21a!,21a ₂ ... are installed in the headbox, said shoulders d form a throttle point after the point of supply of the dilution liquid. The supply of the dilution liquid in this solution is carried out by means of a separate pipe 24a _j fitted in the mixing chamber

S _j . The pipes 24a _j ,24a ₂ ... extend preferably into the middle of the mixing chamber, and they comprise several flow openings for passing the dilution flow into the mixing chamber. The pipe 24a _j ,24a ₂ ... can also comprise, for example, an inclined end, and it can be rotatable around its centre axis, in which case the direction of the dilution flow to the mixing chamber can be adjusted.

Fig. 5 A shows other partition wall constructions that control the mixing chambers S _j ,S ₂ ... , by means of which constructions a desired mixing of the dilution flow and the stock flow can be carried out in the mixing chambers S _j ,S ₂ ... The illustration is a sectional view across the width of the headbox.

Fig. 5B is a sectional view taken along the line II— II in Fig. 5A.

The above figures illustrate the mixing chamber in the space after the inlet header J right in connection with the tube bank 11. The mixing chamber construction in accordance with the invention can also be used after the intermediate chamber in connection with the turbulence generator G.

Fig. 6A shows a second preferred embodiment of the invention.

Fig. 6B is a sectional view taken along the line III— III in Fig. 6A.

Fig. 6C is a sectional view taken along the line IV— IV in Fig. 6A.

In the embodiments shown in Figs. 6A...6C a rather complex chamber construction combination is formed by means of wall constructions, in which chamber con¬ struction combination there is the first chamber section S ₁ ',S ₂ ',S ₃ ' ... into which the dilution liquid is passed from the dilution liquid duct D _{1 ?} D ₂ ... and in which said second chamber section S _j ",S ₂ " ,S3" ... is either a bending chamber construction that ends in the pipes of the tube bank 11 , or the second chamber section S _j " ,S ₂ " ,S3" ... concerned has been substituted for by separate pipes that end in connection with the pipes of the bending pipe row in the tube bank. The dilution liquid flow L _j is passed into the first chamber sections S ₁ ',S ₂ ',S ₃ ' ... through the pipes 24a _j ,24a ₂ .. . The stock flow comes from the inlet header J _t . The combined flow L _j + I--- is passed into the second chamber section S ₁ " ,S ₂ ",S ₃ " ... and further into the pipes in the tube bank 11.

Fig. 7A shows an embodiment of the invention in which a pipe 102 passing the dilution liquid is fitted between the removable partition walls 21a ₍ ,21a ₂ ... , in front of which pipe a separate mixing washer 100 is fitted. The mixing washer 100 is an adjustable/changeable plate comprising a flow opening/openings 101 , through which plate the combined flow _j + L passes as is shown in the figure and which plate

is supposed to mix the combined flow L _[ + L^ effectively before the combined flow passes, for example, into the pipes l la _{j j} . l la _{j 2} ... in the tube bank 11.

Fig. 7B is a sectional view of the embodiment of Fig. 7A taken along the line V-V in Fig. 7A.

In figures a, b and c of Fig. 7C, different embodiments of the mixing plate 100 are shown, in which the opening/openings 101 passing through the plate 100 can comprise a different shape of the flow area. Likewise, the number of the flow openings 101 in the mixing plate 100 can vary. It is easy to install the mixing plate at the outlet side of the area of inlet of the dilution liquid, and the plate is easily changeable in order to obtain the desired mixing of the flow L _[ + L , i.e. in order to combine the stock flow and the dilution flow.