WO2004027152A1

WO2004027152A1 - A spreading apparatus in a paper machine, with a converging feeding chamber

Info

Publication number: WO2004027152A1
Application number: PCT/FI2003/000677
Authority: WO
Inventors: Heikki Vatanen; Tapio Pitkäniemi
Original assignee: Metso Paper, Inc.
Priority date: 2002-09-20
Filing date: 2003-09-17
Publication date: 2004-04-01
Also published as: AU2003262602A1; FI113197B; FI20021675A0

Abstract

The invention relates to a spreading apparatus in a paper/board or pulp machine, or finishing machine for feeding fibrous or other liquid and/or paste onto a web-like object travelling in the longitudinal direction of the machine. The spreading apparatus (1, 22, 28) extends in a transverse direction with respect to the direction of movement of the object and comprises at least one nozzle unit (3, 3a, 20) having a feeding chamber (12) extending in the longitudinal direction (W) of the spreading apparatus, inside which the substance being fed is conveyed from one end (4) of the feeding chamber, moving along the feeding chamber (12) to its opposite end, to which opposite end is optionally formed a by-pass, and a nozzle slot (11) in flow communication with the feeding chamber, the said slot also extending in the longitudinal direction (W) of the spreading apparatus, and to which the substance being fed is conveyed from the feeding chamber, over the total width of the nozzle slot, and further conveyed out of the outlet opening (31) of the nozzle slot (11). The feeding chamber (12) is made so as to converge in the longitudinal direction (W) of the nozzle unit (3, 3a, 20) from the input end (4) of the substance being fed towards the opposite end, and at least one of the walls (13) of the feeding chamber is adjustable for adjusting the convergence of the feeding chamber as desired.

Description

A SPREADING APPARATUS IN A PAPER MACHINE, WITH A CONVERGING EEEDING CHAMBER

The present invention relates to a spreading apparatus in a paper/board or pulp machine, or finishing machine for feeding fibrous or other liquid and/or 5 paste onto a web-like object travelling in the longitudinal direction of the machine, the said spreading apparatus extending in a transverse direction with respect to the direction of movement of the object and comprising at least one nozzle unit having a feeding chamber extending in the longitudinal direction of the spreading apparatus, inside which the substance being fed is

10 conveyed from one end of the feeding chamber, moving along the feeding chamber to its opposite end, to which opposite end is optionally formed a bypass, and a nozzle slot in flow communication with the feeding chamber, the said slot also extending in the longitudinal direction of the spreading apparatus, and to which the substance being fed is conveyed from the

15 feeding chamber, over the total width of the nozzle slot, and further conveyed out of the outlet opening of the nozzle slot.

The aim of the present invention is to provide an improvement to a spreading apparatus, especially one intended for spreading coating paste 20 onto a paper/board web, such as a curtain coater or a jet coater, and more generally to the spreading apparatuses of a paper/board machine for spreading various liquids/pastes, such as a headbox spreading apparatus for feeding pulp to the wire.

25 Curtain coaters are becoming more widely used for coating paper or board webs, because they exert much less force on the web than blade coating/rod coating, and thus cause fewer interruptions due to the breaking of the web being coated, thus improving runnability. With curtain coating, the same smoothness is not achieved as with blade coating, but the coverage attained

30 is better than that attained with blade coating. Curtain coaters can be divided into slot-fed and slide-fed coaters. In a slide- fed curtain coater, the coating is fed by means of a nozzle unit onto an inclined plane, along which the coating flows towards the edge of the plane, thereby forming a curtain as the coating drips from the edge of the plane. In slot-fed applicator beams, the coating is pumped via a manifold into a narrow vertical slot on the lip of which the curtain is formed and drips onto the web. The coating may be spread in one or more layers.

The curtain thus formed is guided by means of an edge guide, which is located on the edge of the feeding slot/feeding lip, as indicated by its name.

One problem with current coating paste curtain coaters is the limited size of the paste feed channels and, partly due to this, the difficulty of controlling the size of the nozzle slot. They are, therefore, unsuitable for wide machines. In addition, current nozzle units form a part of the support structure, which causes problems in manufacture. Accordingly, one important aim of the present invention is to provide a curtain coater which makes possible uniform feeding of coating paste over the total width of the nozzle unit, the said feeding preferably being adjustable to different pastes. More generally, the aim of the invention is to provide a spreading apparatus for spreading various fibrous or other liquids or pastes in a paper/board or pulp machine environment.

To achieve the aims of the invention, a spreading apparatus according to a first aspect of the invention is characterised in that the feeding chamber is made so as to converge in its longitudinal direction from the input end of the substance being fed towards the opposite end, and that at least one of the walls of the feeding chamber is adjustable for adjusting the convergence of the feeding chamber as desired. A spreading apparatus according to another aspect of the invention is characterised in that the feeding chamber is made to converge in its longitudinal direction from the input end of the substance being fed towards the opposite end, and that the length of the nozzle slot in the transverse direction of the nozzle unit also diminishes in the longitudinal direction of the nozzle unit from the input end towards the opposite end.

Between the feeding chamber and nozzle slot is preferably at least one distributing chamber, which balances differences in flow based on the flow resistance being less in the transverse direction than in the direction of the slot. The distributing chamber may be of uniform width, or converge or widen towards the opposite end. A distributing chamber of uniform width is preferably located between the feeding chamber and the nozzle slot into an inclined position so that the length of the nozzle slot in the transverse direction of the nozzle unit diminishes in the longitudinal direction of the nozzle unit from the input end of the substance being fed towards the opposite end.

Between the feeding chamber and the distributing chamber may be a separating wall, which is cogged or perforated, through the openings in which cogging or the said perforations the substance being fed is conveyed from the feeding chamber to the distributing chamber. This type of a separating wall may be utilised in assembling the nozzle unit, whereby the clamping screws can be passed through at the separating wall and from the opposite side to join adjacent parts with each other, and thus the distance from the row of clamping screws at the separating wall to the tip of the nozzle slot remains relatively short. This means that the nozzle unit can be made small, whereby its low own weight will not cause harmful deflections.

Due to the solution relating to the invention, the profile of the substance flowing out of the nozzle slot can become even. According to one preferred embodiment, the profile adjustment of the paste/liquid is automated, which means that transverse profiling may be carried out also during running, which is not possible with currently known solutions. The invention is described in greater detail in the following, with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a slide-fed curtain coater according to the invention,

Figure 2 shows a perspective view of a nozzle part comprised in the nozzle unit of a curtain coater,

Figure 3 shows the nozzle part of Figure 2 as a view seen from the opposite end with respect to the feeding end together with the counterpart, which closes the nozzle part,

Figure 4 shows an embodiment according to the invention of the nozzle unit of a slot-fed curtain coater as seen from the end,

Figure 5 shows the nozzle unit of Figure 4 when assembled with the framework into an applicator beam, and a perspective view of a nozzle part of the nozzle unit,

Figure 6 shows a view corresponding to Figure 5 of another embodiment of the nozzle unit of a slot-fed curtain coater,

Figures 7-9 show a perspective view of the spreading apparatus of a headbox provided with a manifold, as a view seen from the front and as a view seen from the end, respectively,

Figure 10 shows the profile of the substance flowing out of the nozzle slot in the case of a straight feeding chamber, and Figure 11 shows the profile of the substance flowing out of the nozzle slot in the case of a converging feeding chamber.

The slide-fed curtain coater 1 according to the invention shown in Figures 1 to 3 comprises nozzle parts 3, 3a and 32 located on bearers 2 forming a supporting structure, the said nozzle parts together forming a nozzle unit, which has three nozzle slots 11 that make multiple coating possible. The outermost nozzle part 3a is fixed solidly on the bearers 2 and its edge 33 forms a feeding lip, over which the coating paste flowing along the upper surface of the nozzle unit is conveyed to form a coating curtain and to guide it by means of edge guides (not shown) onto the surface of the paper/board web to be coated which is travelling below the coater. The nozzle parts 3 and 32 are arranged movably on top of the bearers 2. In order to move the movable nozzle parts 3, 32, the curtain coater comprises a fixed support 5 resting on the bearers 2, on the other side of the said support, between the innermost nozzle part 32 and the fixed support 5, is a closing tube 6, and on the opposite side of the fixed support 5 an opening tube 7, whereby by pressurising the closing tube 6, the movable nozzle parts 3, 32 can be made to move towards the fixed nozzle part 3a to close the nozzle unit, and by releasing the pressure from the closing tube 6 and pressurising the opening tube 7, the movable nozzle parts 3, 32 can be made to move away from the fixed nozzle part 3a to open the nozzle unit, for example, to remove dried paste from the nozzle slot and/or the different chambers of the nozzle.

At one end of the nozzle unit are arranged feeder pipes 4 for the coating paste being fed, the said pipes opening into the feeding chamber 12 (Figures 2 and 3). The substance being fed travels along the feeding chamber towards the opposite end, at which is optionally arranged a by-pass. When proceeding in the feeding chamber, the substance being fed moves at each point over the length of the feeding chamber to the distributing chamber 15, and from there further to the nozzle slot 11, over the entire width of the nozzle slot 11. The aim being to achieve as even as possible a profile for the substance flowing out of the outlet opening 31 of the nozzle slot 11, the feeding chamber 12 is made to converge in accordance with the invention from the feeding end 4 towards the opposite end, that is, the height U of the feeding end 4 of the feeding chamber 12 is greater than the height L₂ of the by-pass end. In the embodiment shown in Figure 2, this has been realised by placing an adjustable separating wall 13 in the feeding chamber, by means of which the size of the convergence can be changed through adjustment means 14. The operation of the adjustment means is preferably automated, whereby profiling during running will also be possible in the transverse direction of the object to be coated. Merely by making the feeding chamber converge from the feeding end towards the opposite end will result in the situation shown in Figure 11, where the profile of the substance flowing out of the nozzle declines evenly from the feeding end towards the opposite end. This is due to the fact that in the converging feeding chamber, the flow rate remains relatively constant although the paste discharges through the nozzle slot. In such a case, also the pressure loss remains constant because the pressure loss is dependent on the flow rate. While the flow rate remains constant, static pressure in the feeding chamber falls steadily when moving from the feeding end to the by-pass end. In such a case, with a nozzle slot of standard thickness and standard length, also the profile will become an evenly declining one, as shown in Figure 11. When the feeding chamber is a straight one, that is, when it does not converge, the shape of the profile will be approximately that shown in Figure 10, where the profile first clearly falls at the feeding end and then evens out towards the end.

To change the profile so that it will be essentially straight, in the embodiment shown in Figures 2 and 3, also the flow resistance of the nozzle slot 11 has been changed by altering the length of the nozzle slot in the transverse direction L of the nozzle part 3, that is, the length L₃ of the nozzle slot 11 at the feeding end diminishes to the same extent towards the opposite by-pass end (length U of the nozzle slot). In the embodiment of Figures 2 and 3, between the feeding chamber 12 and the nozzle slot 11 is, in addition, a distributing chamber 15, which widens towards the opposite by-pass end in the embodiment shown. The distributing chamber may also be realised so as to be of uniform width by placing it in an inclined position between the feeding chamber 12 and the nozzle slot 11, in such a way that the nozzle slot 11 will converge to the same extent as the feeding chamber 12 converges.

Figures 4 and 5 show a slot-fed curtain coater which is comprised of a nozzle part 20 and a support part 21, which is fixed to the framework 23. For corresponding parts of the nozzle part 20 are used the same reference numerals as for the nozzle part 3 in Figures 1 to 3. In the slot-fed curtain coater 22, the coating is pumped through a feeding chamber into a nozzle slot placed in a vertical position, at the lip of which the curtain is formed and drips downwards onto the web. The slot-fed curtain coater 28 according to Figure 6 differs from the embodiment of Figure 5 in that the feeding chamber 12 of the nozzle part 25 is formed so as to be a solid, converging chamber, while the nozzle slot 11 correspondingly converges from the feeding end towards the opposite end. The nozzle part 25 is connected with the counterpart 26 to form the nozzle unit, the counterpart being fixed to the frame part 27.

Figures 7 to 9 show an embodiment of a spreading apparatus intended for headbox pulp feed, the spreading apparatus comprising a converging feeding chamber 42, from which the substance being fed is conveyed through the manifold 41 into the distributing chamber 45, and further to the nozzle slot 44. The nozzle slot 44 of the nozzle part 43 and the distributing chamber 45 are of uniform width in this embodiment, whereas the length of the manifold 41 shortens from the feeding end towards the opposite end to the same extent as the feeding chamber 42 converges. This will give a relatively even outflow profile.

Claims

1. A spreading apparatus in a paper/board or pulp machine, or finishing machine for feeding fibrous or other liquid and/or paste onto a web-like object travelling in the longitudinal direction of the machine, the said spreading apparatus (1, 22, 28) extending in a transverse direction with respect to the direction of movement of the object and comprising at least one nozzle unit (3, 3a, 20) having a feeding chamber (12) extending in the longitudinal direction (W) of the spreading apparatus, inside which the substance being fed is conveyed from one end (4) of the feeding chamber, moving along the feeding chamber (12) to its opposite end, to which opposite end is optionally formed a by-pass, and a nozzle slot (11) in flow communication with the feeding chamber, the said slot also extending in the longitudinal direction (W) of the spreading apparatus, and to which the substance being fed is conveyed from the feeding chamber, over the total width of the nozzle slot, and further conveyed out of the outlet opening (31) of the nozzle slot (11), characterised in that the feeding chamber (12) is made so as to converge in the longitudinal direction (W) of the nozzle unit (3, 3a, 20) from the input end (4) of the substance being fed towards the opposite end, and that at least one of the walls (13) of the feeding chamber is adjustable for adjusting the convergence of the feeding chamber as desired.

2. An apparatus as claimed in claim 1, characterised in that the length (L₃, U) of the nozzle slot (11) in the transverse direction (L) of the nozzle unit (3,

3a, 20) diminishes in the longitudinal direction (W) of the nozzle unit (3, 3a, 20) from the input end (4) of the substance being fed towards the opposite end.

3. An apparatus as claimed in claim 1 or 2, characterised in that between the nozzle slot (11) and the feeding chamber (12) is at least one distributing chamber (15), which also extends in the longitudinal direction (W) of the spreading apparatus.

4. An apparatus as claimed in claim 3, characterised in that the distributing chamber (15) is of uniform width and located between the feeding chamber

(12) and the nozzle slot (11) into an inclined position so that the length (L , U) of the nozzle slot (11) in the transverse direction (L) of the nozzle unit diminishes in the longitudinal direction (W) of the nozzle unit (3, 3a, 20) from the input end (4) of the substance being fed towards the opposite end.

5. An apparatus as claimed in claim 3, characterised in that the distributing chamber (15) widens in the longitudinal direction (W) of the nozzle unit from the input end (4) of the substance being fed towards the opposite end.

6. An apparatus as claimed in any of the claims 1 to 5, characterised in that the said at least one adjustable wall (13) of the feeding chamber (12) can be adjusted gradually to achieve the desired transverse profiling of the substance flowing out of the nozzle slot (11).

7. An apparatus as claimed in claim 6, characterised in that the adjustment of the said adjustable wall (13) is automated.

8. An apparatus as claimed in any of the above claims, characterised in that the said at least one nozzle unit (3, 3a, 32) is located on a separate support structure (2).

9. The use of an apparatus as claimed in any of the claims 1 to 8 for curtain coating.

10. The use of an apparatus as claimed in any of the claims 1 to 8 for jet coating.

11. The use of an apparatus as claimed in any of the claims 1 to 8 in a headbox for supplying pulp onto a wire.

12. A spreading apparatus in a paper/board or pulp machine, or finishing machine for feeding liquid and/or paste onto a web-like object travelling in the longitudinal direction of the machine, the said spreading apparatus (1, 22, 28) extending in its longitudinal direction (W) with respect to the direction of movement of the object and comprising at least one nozzle unit (3, 3a, 20) having a feeding chamber (12) extending in the longitudinal direction (W) of the nozzle unit, inside which the substance being fed is conveyed from one end (4) of the feeding chamber, moving along the feeding chamber (12) to its opposite end, to which opposite end is optionally arranged a by-pass for the substance being fed, and a nozzle slot (11) connected to the feeding chamber, the said slot also extending in the longitudinal direction (W) of the spreading apparatus, and into which the substance being fed is conveyed from the feeding chamber, over the total width of the nozzle slot, and further conveyed out of the outlet opening (31) of the nozzle slot (11), characterised in that the feeding chamber is made to converge in its longitudinal direction (W) from the input end of the substance being fed towards the opposite end, and that the length of the nozzle slot in the transverse direction (L) of the nozzle diminishes also in the longitudinal direction (W) of the nozzle unit from the input end towards the opposite end.