FI90740B - Device for coating a moving web of paper or paperboard - Google Patents

Abstract

The metering mechanism positioned against a counter-roller and located behind, with respect to the running direction of the material web, a pre-coating facility features a slit 14 on the feed side of a balancing chamber 1 formed on a front wall 4 to the counter-roller 2 and extending over the width of the web. The front wall 4 is provided with discharge channels 10 extending in the manner of a slit across the width of the web, which can be throttled by a rotary disc valve 7. In this way, an outflow from the balancing chamber 1 can only occur through the discharge channels 10, while only the coating material from the material web can be introduced through slit 14 into the balancing chamber but no coating slip emerges from the balancing chamber. <IMAGE>

Description

90740 APPARATUS FOR COATING MOVING PAPER OR PAPERBOARD -ORDING FOR BESTRYKNING AV EN RÖRLIG PAPER- ELLER CARTON BANA 5

The invention relates to a device according to the preamble of claim 1.

Such a device has become known from DE-OS 15 46 10 312. Here the coating mass enters the leveling chamber through the inlet gap and fills it completely. Part of the coating mass exits the leveling chamber, adheres to the paper web on the discharge side, namely between the scraper element and the paper web. The second part, namely the excess, leaves the leveling chamber again on the inlet side and counter-15 to the flow mass entering therein. The inflow gap then has two flows that occur in opposite directions to each other.

These opposite currents always lead to problems. Namely, the quality of the front 20 is deteriorated in this countercurrent. Deterioration can usually no longer be smoothed out with a scraper element.

There are numerous other solutions, for example, a nozzle application device with a machine-wide slit nozzle from which a jet of spray pulp emits 25 per paper web. There is too much work here too. In this case, there is again an excess on the inlet side of the paper web in the coating zone between the two lips of the gap. Thus, the excess must also flow again here against the direction of travel of the paper web. The consequences are as unfavorable as in the device 30 described above with a smoothing chamber.

In the following, the prior art has been further evaluated, initially with the apparatus disclosed in U.S. Pat. No. 4,250,211, based on the principle that from the pulp chamber to the coating zone 35 in the opposite direction. The problem is that with the paper web traveling dry to the coating zone, due to the roughness of the web 2, a very large amount of air passes to the coating zone.

Correspondingly, in FI patent application 844151, the web feed side-5a has a web scraping blade as well as a transition point towards the blade below the coating zone. In this case, the excess coating mass is passed directly through this transition point.

In the solution according to FI patent application 861663, the plate with more than 10 outlets is formed in such a way that it forms a long throttling gap in the material web.

GB patent application 2,173,718 has a transition plate forming a choke gap with a web of material, practically raised so as to be in contact with the web of material. In addition, at least one opening is formed in the plate of the transition point for the excess coating mass. In this case, the plate of the transition point scrapes the web of material in an unfavorable manner.

U.S. Patent 4,396,648 discloses an apparatus based on the basic principle already described, in which a substantially rotating rod is placed in different positions and actually controls the excess coating material flowing from the coating zone through the throttling gap of the transition point plate.

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The object of the invention is to provide a device according to the preamble so as to avoid flow and countercurrent disadvantages in the area of the inlet of the equalization chamber.

30 That task is solved by the novelty characteristics of the main claim.

The invention is described in more detail in connection with the drawings. They set out in detail:

Figure 1 shows a cross-section of the device seen from the side.

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Figure 2 shows another embodiment, in which only the essential elements are shown in cross-section.

Fig. 3 shows a top view of the embodiment according to Fig. 2.

Figure 4 and

Figure 5 shows other embodiments 10 according to the invention in the same side view and also in cross-section.

In the embodiment shown in Figure 1, the paper web surrounds the rotating support roll, as shown by the dotted line. The paper web is coated with a coating composition 18 applied by a roll application device (not shown) which includes a dipping roll. The lubricant 18 is applied here in excess.

A smoothing chamber 1 is further seen, which - viewed in the direction of travel of the paper web-20 (see arrow) - is delimited on the inlet side by the front wall 4 and on the outlet side by a scraper 3.

On the opposite side of the counter roll 2, the leveling chamber 1 is delimited by the support wall 29 of the support beam and the Tightening piece 25 attached thereto. The sliding blade 3 is attached to the tensioning piece 25 by means of a tensioning lever 28. The front wall 4 is maintained in the double arrow direction of the movably supporting the wall 29 (this is not shown in detail).

As can be seen, the front wall 4 is formed in a special way, the edge part 6 forms a wedge-shaped inlet wedge with respect to the support roll 2. its front wall shows an outlet channel 10 which, viewed in the flow direction, consists of a part 8 having a relatively large flow cross-section and a part having a relatively small flow cross-section. Part 8 includes a cylindrical rotary slide 7.

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The rotating slide 7 has a plurality of openings 9, which - viewed in the direction of the longitudinal axis of the rotating slide 7 - are arranged side by side. Likewise, a number of outlet channels 10 are provided over the entire width of the machine, as can be seen, for example, in Figure 3 with regard to the second option 5 (openings 10 '). In this case, the length of the rectangular cross-section of the outlet openings 10 can also be substantially greater. It is theoretically possible - with a relatively small machine width - that only a single slit-like discharge channel is provided, which extends over the entire width of the machine and, on the other hand, several rotating slides.

The alternative of the invention shown in Figures 2 and 3 illustrates only its front wall and cross section (Figure 2) and the top view of the side from which the paper web comes (Figure 3).

In this case, there are again outlet channels 20 in the front wall 24 and the number of these channels is distributed over the entire width of the machine. The outlet ducts 20 are provided with a sliding strip 15 with a window 16. The number of windows 16 is exactly the same as the number of outlet ducts 20. The discharge channels can be opened more or less by pushing the sliding strip 15 against the direction of travel of the paper web, respectively, whereby the discharge channels are more or less released.

The amount of pre-dosing-25 applied in a large overdose is now transferred to the leveling chamber 1 through the gap 14 formed in the web of material. Preferably, the chamber may also be closed by retractable sidewalls 22 at the edges 30 of the web. The gap with a smaller gap width 14 is now adjusted by moving the front wall 4. The rotating slide 7 or the throttling slide 15 is then adjusted so that the excess coating mass exits only through the discharge channels 10 or 20, but not at all or in a noticeable amount through the gap 14 from the leveling chamber 1. in the area as uniform as possible flow conditions in the leveling chamber 1 including slot 14 and li 5 90740 flawless coating without creases, orange peel formation, film unevenness or the like.

The alternative shown in Fig. 4 is substantially similar in structure to that shown in Fig. 1, except for the only difference that the sliding 7 and the discharge channels of the leveling chamber 21 are not located in the front wall 6 but in the rear wall 12 supporting the scraper 3.

In the embodiment shown in Fig. 5, the discharge channels 10 are located lower, i.e. in the wall 49 of the leveling chamber 31, which is further away from the counter roll 2 or the material web.

15 The leveling chamber is preferably closed by side dam walls or sealing walls 17, 27, 37. It is not necessary for these walls to rest on a track or counter roll (in which case they should be made of a soft material which is reversible), there are 20 small gaps of 1-2 mm. These dam walls are preferably held in place by holding devices formed by extensions 33 of the walls of the leveling chamber. They can thus be adapted alternately and to different positions of the leveling chamber. This is shown in particular in detail in Figure 3.

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Claims (5)

An apparatus for coating a web of moving paper or board, 5 of which surrounds a rotating support roller (2), the apparatus having a pre-coating for applying the coating mass (18) in excess, a leveling chamber (1, 21, 31) having a wall (4) on the inlet side, which in turn leaves the inlet gap (14) free at and against the coated track, and on the outlet side of which there is an element (3) of the scraper 10, characterized in that the leveling chamber (1, 21, 31) has one or more outlet channels (10, 20, 40), 50) and that throttling means (7, 15) are arranged in the discharge channels (10, 20, 40, 50) for controlling the amount and / or pressure of the discharge mass. 15 Device according to claim 1, characterized by outlet ducts (8, 10, 20) in the same wall (6) which forms the inlet gap (14). Device according to Claim 1, characterized in that the outlet ducts (40, 50) are located in at least one of the walls of the leveling chamber (21, 31) other than the inlet wall (24, 26, 34). Device according to one of Claims 1 to 3, characterized in that the throttling elements (7, 15) are arranged inside or structurally immediately in said walls. Device according to one of Claims 1 to 4, characterized in that one or more slides (15) or rotating slides (7) are arranged as throttling elements. Il 90740