The invention concerns an apparatus in connection with the headbox of a paper machine or equivalent.

It has proved to be a problem with old headboxes that the distribution tube banks are there attached to the headbox structures in such a way that it has proved diffi- cult to add a dilution profiling system to them. In known headboxes, the diluting profiling is done in such a way that the diluting liquid is conducted into one row of pipes formed by superimposed pipes. The number of dilution valves will hereby be high in many cases and many other mechanisms are also needed. In known device solutions, expensive machining is made in the dilution plates and thick plate dimensions have to be used. This has resulted in further increases in costs. In many cases cleaning at state-of-the-art dilution headboxes is imple- mented in such a way that they are equipped with an opening structure, which can be opened owing to hinging means for the time of washing. However, the solution is expensive.

The present application presents an apparatus of a new type in the web formation for mixing dilution water and the stock conducted from the inlet header of a paper machine. According to the invention, the apparatus comprises such a body, into which inlet channels for the dilution water are drawn, which are made to open into mixing chambers for the stock and dilution water, which chambers may also be called dilution water chambers in the present application. The dilution water is conducted into the top part of each mixing chamber, so that the facing end of the dilution water will open into the mixing chamber from its top wall. In the solution according to the invention, each mixing chamber comprises at least two, prefera- bly more rows of pipes located side by side. In bringing the dilution water into the mixing chamber it is made to flow around the pipes entering the mixing chamber

and further through the flow gap between the pipe ends and the outlet pipe ends to join the stock flow and further as a joined flow of dilution water and stock Ll + L2 away from the mixing chamber. In the operating situation, the mixing chamber proper is entirely filled and pressurized by dilution water.

In the new solution there is no need to exchange the tube bank and it is also suit- able for headboxes provided with a fixed tube bank. The dilution can be divided simultaneously into several pipes located side by side and on top of each other using the same valve, whereby the number of valves and the costs are reduced. It has been possible to shorten the time of standstill for installation, because the tube bank need not be exchanged. The structure is a light sleeve structure and the parts can be made without any manual grinding.

In the solution according to the invention, washing of the mixing chamber can be carried out in the following manner. A duct opens into each washing chamber from the lower part of the washing chamber. The duct in question can be con- nected to a system of supply ducts for the washing liquid. Thus, by supplying the washing liquid from below upwards into the mixing chamber, washing liquid is made to flow in a direction opposite to the dilution water and also in a direction opposite to the stock from the stock inlet header. In this way the washing opera- tion is made even more effective.

In the apparatus solution, the device may comprise a closing spindle, in which holes are made by boring at mixing chamber spacing. Using the spindle, the sys- tem of washing ducts can be opened and closed by a rotating or linear motion of the spindle. The closing spindle may have a circular or rectangular cross-sectional shape. The closing spindle may extend over the entire width of the headbox or it may be, so to speak, modulated in the CD direction, whereby the closing spindle extends into the area of certain mixing chambers and several closing spindles are used side by side. In the structure, the closing spindle may be placed in a groove made as a part of the body plate of the apparatus structure.

The concerned system of washing ducts allows washing the mixing chambers the lower way and individually, for example, using a pressure washer, or alternatively all mixing chambers may be connected to the same system of washing ducts, whereby supply of the washing water takes place simultaneously into all mixing chambers. Since in the washing situation the direction of flow inside the mixing chamber is changing from normal to the opposite due to the washing pipe fitting located in the lower part, cleaning of the areas soiled in the running situation be- comes more effective.

The apparatus according to the invention in connection with the headbox of a pa- per machine or equivalent is characterised by the features presented in the claims.

The invention is presented in the following with reference to some advantageous embodiments shown in the figures of the accompanying drawings. However, the invention is not limited to these only.

Figure 1A is a side view and longitudinal cross-section of the headbox in a paper machine.

Figure 1B shows the target area of the invention, an arrangement for supplying dilution water to join stock conducted from a stock inlet header. The figure shows target area X, from Figure IA.

Figure 1C is a sectional side view along the line 1-1 in Figure 1B.

Figure 2 shows on an enlarged scale a mixing chamber and the structures associ- ated with it.

Figure 3 is an axonometric view of the formation of a mixing chamber structure.

Figure 4A is an example in principle of an arrangement for washing mixing chambers.

Figure 4B shows washing modules on an enlarged scale.

Figure 1A shows the so-called dilution headbox 100 of a paper machine.

Figure 1B shows the area X, of Figure 1A on an enlarged scale.

Figure 1C shows the apparatus as a partial view from the front and as a sectional view along the line I-I in Figure 1B.

Dilution headbox 100 comprises a stock inlet header Ji, from which stock m1 is conducted as shown by arrow L, into mixing chambers 13a1, 13a2... of an appara- tus 10 according to the invention, which chambers may also be called dilution water chambers in this application. The dilution water is conducted from a dilu- tion water inlet header J2 through ducts 12a1, 12a2.. and valves V1, V2.. regulating the flow L2 into mixing chambers 13a1, 13a2... The ducts 14al l, ducts 14al. 2 lead from the stock inlet header J, into the mixing chambers 13al, 13a2... From the mixing chambers 13a1, 13a2.. there are ducts 15a).), 15at. 2..., 15a2.), 15a2. 2... for the dilution water and stock mixture L, + L2 to be conducted away.

Ducts 12al, 12a2.. lead to mixing chambers 13a1, 13a2... located in various width positions of the paper machine's headbox. The dilution water is used to control the consistency of the stock mi and thus the web's basis weight across the width of the web to be the desired ones by adjusting valves V"V2... Thus, the dilution valves V, are used to control the dilution water flow L2 to the desired places across the headbox width and thus to control the basis weight of the paper web or equivalent across the width of the web. The dilution water flow L2 arrives in each mixing chamber 13al, 13a2... at the desired place across the width in the desired quantity and the dilution water is mixed with the stock flow L, conducted from

the inlet header J, at the concerned place over the width into the mixing chamber 13al, 13a2... The combined flow L, + L2 is conducted further as shown in Figure 1A into a tube bank P and further into an intermediate chamber E and further into a turbulence generator G and further through a slice cone K on to a forming wire Hl.

Figure 2 shows a mixing chamber 13al and the relating structures on an enlarged scale. The view is a longitudinal sectional view in the machine direction. As is shown in Figure 2, the apparatus 10 comprises the following structural parts for mixing a flow of dilution liquid, preferably dilution water (arrow L2), and stock mi conducted (arrow LI) from the stock inlet header Jl of the headbox. The appa- ratus 10 according to the invention for mixing dilution water and stock ml com- prises a body part 11, which is connected in a module-like manner. It can be con- nected in between the stock inlet header J, and the tube bank P, for example, into old headboxes.

From an inlet header J2 for the dilution water the dilution water is conducted into ducts 12al, 12a2,12a3.., each of which comprises a valve Vl, V2.. The valves Vl, V2... are used to control the flow of dilution water; the rate of flow through the ducts 12al, 12a2.., preferably through hoses or pipes to join the flow Ll of stock m, conducted from the stock inlet header Jt. The ducts 12a1, 12a2.. for the dilution water are drawn to the various headbox width positions, and by controlling the inlet of dilution water joining the flow L, of stock mi the dilution is controlled and thus also the consistency of the stock at each place across the width of the headbox and thus the basis weight of the web, such as a paper web, at each posi- tion over the web width.

According to the invention, the dilution water ducts 12a1, 12a2.. open into the mixing chambers 13a,, 13a2,13a3... for stock m, and dilution water. The ducts 12al, 12a2.. open into the top part of the mixing chambers 13al, 13a2... They do not extend into the mixing chambers 13a1, 13a2.. proper, but open from the cover-

ing wall T, of the mixing chambers 13a1, 13a2.. directly into the mixing chamber 13ai, 13a2...

Each mixing chamber 13a1, 13a2.. comprises pipes 14a1.1, 14a1.2 .. , which are drawn to the mixing chamber from a stock inlet header Jl and in such a way that into each mixing chamber extend at least two duct rows, preferably pipe rows 14a1.1, 14a1.2 .. ; 14a2. 1, 14a2.2... The ducts, preferably pipes 14a1.1, 14a1.2 .. ; 14a2.), 14a2. 2.., are adapted to open into the mixing chamber 13a1, 13a2.. in such a way that the ends of the pipes 14a1.1, 14a1. 2.. are at a short distance h1 from the outlet ducts, for example, pipes or, as in the figure, preferably plate borings 15al. 1, 15ai. 2.. ; 15a2. l, 15a22..., which outlet ducts open into the mixing chamber 13a1, 13a2... and face the ends of the pipes. Under these circumstances, an annular gap D, is left between the ducts 14a,.,, 14a,. 2.. for the stock flow and the ducts 15a1.1, 15a1. 2 on the outlet side for the stock mi and the dilution liquid conducted thereto.

The width h1 of the annular gap D, is within a range of 2-8 mm, preferably 3-5 mm. Thus, the dilution water flow and the stock flow are mixed together in the space between the end of ducts 14a1.1, 14a1. 2.. and the ends of the ducts 15a1.1, 15au. 2 on the outlet side. Thus, the term mixing chamber is used. Outside the mix- ing point proper the mixing chamber is filled by dilution water. The pressure of the dilution water exceeds the pressure existing in the stock flow, whereby the direction of flow of the dilution water is from the mixing chamber 13al, 13a2.. into the ducts 15a,.,, 15a,. 2.

Under these circumstances, the dilution water is conducted from the ducts, such as pipes 12ai, 12a2.., into the mixing chambers 13a1, 13a2.. located side by side, which in the present application may also be called dilution water chambers, and it will flow into each mixing chamber 13a1, 13a2.. from above downwards and around the ducts 14ai.,, 14a1, 2.. on the inlet side of the mixing chamber 13a1, 13a2... for the stock mi, and further through the annular gaps D, into each duct 15a1.1, 15a1. 2..; 15a2. 1, 15a2. 2.. on the outlet side of the mixing chamber 13al, 13a2.. as a flow L2 + Li. The dilution water fills the mixing chambers 13ai, 13a2..,

and the actual mixing together of the dilution water and the stock mi takes place in the space between the ducts 14a1.1, 14a1.2.. on the inlet side and the ducts 15a1. 1, 15at. 2.. on the outlet side.

Thus, each mixing chamber 13al, 13a2.. is a free space, which is limited only by the mixing chamber's covering wall Tl and bottom wall T2 and vertical walls T3 and by the partition walls 16al, 16a2.. separating the mixing chambers 13au, 13a2... Into the concerned free internal space of the mixing chamber 13al, 13a2.. extend the ducts for the stock m, drawn from the stock mi inlet header Jl, such as pipes 14a. l, 14a. 2.., and in such a way that there are inlet ducts into each mixing chamber 13au, 13a2.. in at least two adjacent rows, preferably in three or even in more rows. The ducts, such as pipes 14a,.,, 14a,. 2.., in each row, and correspond- ingly the outlet ducts 15a1.1, 15at. 2.., may be in non-linear rows superimposed in a zigzag fashion.

The body 11 of the device according to the invention with its parts mentioned above can easily be connected in between the stock inlet header J, and the tube bank P of old headboxes, and thus the old headbox structure is easily changed afterwards and made into a dilution headbox. According to the invention, the par- tition walls 16a1, 16a2.. may be designed as curved structures and, in addition, according to the invention, adjacent duct rows or pipe rows may be staggered in relation to each other in a zigzag-like manner, whereby marking of the web is avoided.

The device body 11 comprises a first facing plate 17. The facing plate 17 is joined by screws R, to the basic body 18, to its plate 18a,. Another facing plate 19 is further joined to a plate 18a2 by screws R2. The plates 18a, and 18a2 are connected by ribs 18b. The apparatus 10 is connected by screws Ri, R3 and R4 to the tube bank P and to the stock inlet header J, and, for example, to an old headbox.

Figure 3 is an illustrating axonometric view of the apparatus 10 according to the invention separately from the tube bank P before it is joined to the tube bank P.

The embodiment is otherwise like the structure shown in the other figures, but each vertical row comprises only three ducts 14al l, 14al. 2, 14a1.3... 15a1.1, 15a1. 2, 15al. 3; 14a2.1, 14a2.2, 14a2.3... 15a2.1, 15a2. 2, 15a2. 3.

Figures 4A and 4B show washing of the mixing chambers 13al, 13a2.. and ducts 14a1.1, 14a1.2 ..., 15a1.1, 15a1. 2. Washing of the mixing chamber 13a1, 13a2.. may be performed efficiently by joining the inlet duct 20 for washing liquid to each washing liquid duct 21a1, 21a2.. opening into each mixing chamber 13al, 13a2...

Thus, washing of the mixing chamber 13a,, 13a2.. can be performed by making the washing liquid flow from below upwards from the bottom part of the mixing chamber 13a1, 13a2.. to its top part and out through the inlet ducts 12a1, 12a2.. for dilution water and the ducts 14ai, l, 14a,, 2..., 15a,.,, 15a,. 2. For efficient washing, washing should be done in the direction opposite to the direction of flow during operation.

The inlet duct 20 for washing liquid is connected to each mixing chamber 13a1, 13a2... As is shown in Figure 4A, the washing duct 20 is branched into branch ducts 20al, 20a2,20a3, which join a washing module 21al. Correspondingly, branch ducts 20a4, 20a5, 20a6 join another washing module 21a2. The washing module 21a1 has an adjusting or closing spindle 21bu and the washing module 21a2 has an adjusting or closing spindle 21b2. In the embodiment shown in the figure, the adjusting spindle is turned to align the perforations Ci, 2.. of the ad- justing spindle with the ducts 20al, 20a2,20a3... and with ducts el, e2... opening into the mixing chambers 13a,, 13a2.., and in this way a connection can be opened to each mixing chamber 13a1, 13a2...

A paper machine or equivalent means paper, board and tissue machines as well as pulp drying machines.