EP1676957A2 - Coating apparatus - Google Patents

Abstract

A curtain coater for applying liquid to paste-like media (especially aqueous pigment suspensions) to a running sheet of paper, cardboard etc. has, in addition to an air boundary layer-abatement device on the coating side, another such device on the other side of the sheet near the point of impact of the curtain. A device for applying a liquid to paste-like medium, especially an aqueous pigment suspension (I), to one side of a running sheet of paper, cardboard or other fibrous material during its production and/or finishing. This comprises a curtain applicator (5) by means of which (I) is delivered directly onto the coating side (1a) of the sheet (1) in a free-falling, closed curtain (6) under the action of gravity, with the curtain impinging at a point (P) on an open section of sheet or on a part supporting the other side (1b) of the sheet, and with a device (2) for weakening or removing the air boundary layer, which is dedicated to the coating side (1a) and installed in the running direction (L) in front of the curtain (6). The system also has another air boundary layer abatement device (10) for air boundary layers (LG) flowing with the fibrous sheet (1), which is located on the other side (1b) of the sheet near the impact position (P) of the curtain (6).

Description

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

Machines for the production and / or finishing of a paper, cardboard or other fibrous web nowadays have widths of up to 10m and more for reasons of economy. When coating this wide fibrous web by means of a curtain coater, a curtain delivered by the applicator is to be kept stable over its entire width, so that the curtain in closed form, without the influence of harmful air inclusions, over the entire Web width ensuring uniform order result.
This requirement is the more difficult to realize the faster the fibrous webs run in the machine. It is also dependent on the quality of the fibrous web and the application medium.

The curtain coater is arranged at a predetermined distance from the web side of the fibrous web to be coated and discharges the application medium, consisting for example of pigment-containing coating color, as a substantially gravitationally moving curtain from a machine-wide slit nozzle. The coating with this commissioned work (curtain coater) takes place without excess of medium. This means that only as much medium is dispensed and applied to the fibrous web as to remain on it in the end. The curtain produced by the commissioned work is therefore less voluminous and very sensitive, especially to incoming air boundary layers.

The subsequently published DE 103 58 508.7 deals with the problem of the harmful influence of air boundary layers flowing in front of the applicator with the high-speed fibrous web.

In this invention, it is described that in the running direction of the moving fibrous web before the commissioned work an air boundary layer-attenuation device is arranged. So that the influence of the air boundary layers can be further reduced, further devices (also denoted as removal means) are provided around the applicator or the applicator nozzle on the coating side. These facilities are designed here strip-shaped and assigned to the web page to be coated as mentioned. In addition, configurations are described with which a shield of the entire commissioned work or parts thereof or the curtain against the influences of the air boundary layers are possible.

In the past, however, disturbances of the curtain were repeatedly observed.

It is therefore an object of the invention to provide an improved device with which eliminates these disorders, but at least can be further minimized so that an even more uniform order result on a moving fibrous web in their manufacture and / or finishing with a curtain coater can be achieved.

The object of the invention is achieved with the characterizing features of claim 1.

According to the invention, it is provided that an air boundary layer control device for air boundary layers flowing with the fibrous web is arranged on the web side opposite the coating side. This control device is assigned to a longitudinal track section, which passes through the moving track and in the area of which the impact position of the curtain is located on the opposite side of the track.

It is the merit of the inventors to have realized that air boundary layers even also exert harmful effects on the fibrous web on the opposite side of the coating side. The web therefore tends to flutter, bulge, drape or even demolition. The effects described above have a very negative effect on the curtain located opposite or above the web, especially at its impact point.

The proposed air boundary layer fighting device can be made as a structural unit, consisting of a support body and arranged thereon acting in the direction of the web underside Luftabstreifleisten. Here it is very advisable if the squeegee are flexible. Ideally, they do not or hardly touch the fibrous web.

In one embodiment of the invention can be provided that this control device is disposed on a present below the fibrous web catcher for the curtain. The device is characterized compact.

Their configuration is possible in various ways.

Thus, it can be provided in a variant that an existing collecting device, which is provided for collecting medium parts of the curtain outside the width of the fibrous web, so for collecting the dispensed side edges of the curtain during the operating phase of the commissioned work and / or a web break, simultaneously is designed as air boundary layer removal device. The catcher then has side walls which act as baffles, whereby in the operating phase of the applicator the incoming air boundary layers can be stripped and directed outwards to a location where they are harmless.
The complete catcher is designed swiveling.

In a further variant, it can be provided that a height-adjustable squeegee strip on the inlet side (this is the side to which the fibrous web in its Running way tapers) of the collecting device is arranged. The distance between the upper edge of the squeegee is motorized, but also manually adjustable.

In the former variant, a further advantageous solution is that the collecting device is formed like a trough with respectable height. As a result, it can be designed in a simple manner in terms of flow, so that its inlet side (which is also the side on which the fibrous web tapers to it) can act as a guide surface for deflecting the air boundary layer. In addition, the collecting device has a continuous fibrous web substantially parallel upper edge or upper edge surface. This upper edge is very close to the fibrous web, that is arranged at a distance a between about 0 and 3 mm. It is an arrangement at a distance, an arrangement with contact or an arrangement with "immersion" (up to -1 mm) in the web possible.
As a result, it is particularly prevented that the air boundary layer can be formed again.

It is very advantageous if the collecting device is arranged in the region between two bodies which convey the fibrous web to the applicator unit and which are again guided away from the applicator unit and optionally deflected. At a particularly small distance a the fibrous web undergoes a certain support in the area of the curtain applicator. In this arrangement, at least one side wall of the collecting device should reach up to at least one of the body or guide body, which has a particularly favorable effect on the running behavior of the web in the region of the guide body. Air boundary layers can thus not crowd between the guide body and the web, which in turn has a positive effect on the running behavior of the fibrous web in the further path through the manufacturing and / or finishing machine.

With regard to the running behavior of the web, it is expedient if the bodies or guide bodies are each designed as rotating rollers. As center distance from each other 400 to 2000mm, preferably 500 to 1200mm provided. The Body formed as guide rollers are adjustable relative to each other in height, so that a sloping or rising guide the fibrous web at an angle α between 10 and 40 ° can be achieved. Such a slope (+/-) has been found to be particularly effective at depositing the curtain on the fibrous web. An increasing web guide brings advantages in terms of preventing the entry of incoming air boundary layers on the coating side, while a falling web guide causes an additional stretching of the curtain when depositing on the fibrous web and thus an improvement in the quality of the application layer.
The arranged in front of the curtain relatively large guide roller already acts as an air barrier barrier.

Instead of the rotatable, designed as rollers and possibly as suction rollers guide body can also be provided that at least one guide body is formed as a stationary element. For this purpose, a known Airturn for contactless guidance and deflection of the fibrous web is suitable.

An advantageous embodiment may be that the collecting device is equipped with a hinged Luftgrenzschicht- squeegee, which faces the inflowing air boundary layer. Such an embodiment is easier to produce than the production of a specially designed as a bulkhead sidewall.

The entire catcher, as well as the squeegee can be designed as swung off. This is useful for service purposes, above all, space is created when in this area a new train pulled, i. must be transferred.

Further advantageous embodiments will become apparent from further subclaims.

The invention will be explained in more detail with reference to embodiments.

Show it:

• Figure 1 : a schematic representation of a first embodiment of the applicator device according to the invention with falling web guide in the side view
• Figure 2 : a schematic representation of a second embodiment of the applicator device according to the invention with increasing web guide in the side view
• Figure 3 to 5 : in a schematic representation of further embodiments of the applicator device according to the invention with falling web guide in the side view
• Figure 6 ad: various examples of web guide paths, for the fibrous web before and after the coating

In the figures, identical or equivalent elements or components are provided with the same reference numerals and are described only insofar as changes result from the other figures.

FIG. 1 shows how a fibrous web 1 traveling in the running direction L, coming from above, approaches a first body 2 for guiding and deflecting the web. Then, in a distance 3 sloping at an angle α of about 15 °, the web 1 passes to a second body 4, from which the web 1 runs downwards to further treatments, such as drying, smoothing, further coatings, rolling up, etc.
Both bodies 2 and 4 are guide bodies for the fibrous web 1. They could be designed as so-called standing air turns, as shown in FIGS. 6 a to d . In the example of Figure 1 but rotating rollers are provided, whose diameter is between 400 and 800mm. Due to their diameter, these, in particular the first roll 2, are suitable for use as air-boundary layer control systems. or removal device to be able to act on the coating side 1a.

The coating side 1 a within the distance 3 a machine-wide (adapted to the width of the fibrous web) curtain applicator unit 5 is arranged, which emits a vertically downwards and freely falling curtain 6 on the coating side 1 a. This curtain 6 strikes in a position P or in a point of impact or impingement on the fibrous web and deposits there as a coating layer in the desired thickness. In order for this layer to deposit as evenly as possible over the entire width of the web or desired coating width and without defects, various devices are provided with which the penetration of disturbing air boundary layers in the direction of the curtain 6 is prevented or minimized. Namely, if the curtain 6 is not stable and does not form a uniform and continuously closed veil (without air pockets), then the coating layer is then not even. These devices are in the running direction L of the fibrous web 1 before and after the curtain 6 and the web - i. Coating side 1a assigned. These so-called air boundary layer weakening or removal or control devices are designed in the form of the first roller 2 and at least one sealing strip 7 arranged downstream of the roller 2. After the curtain is on the same side of the web 1a a vertically Asked and approximately the length of the curtain 6 representing protective wall 8 is provided, which also still disturbing air boundary layers -something caused by pumping effects of the fibrous web- prevented.

For the sake of completeness, a collecting channel for the start and stop phase of the commissioned work 5, which can be moved in and out of the curtain 6 in the direction of the double arrow, is shown here. The starting chute is in the retracted state above the second guide body. 4

The opposite web page 1b is within the distance 3 in the region of the impact point P, a further air boundary layer weakening or control device 10 is present.

In the figure 1 it is shown that this is attached in the form of a wiper blade 10a on a trough-shaped collecting device 11 for collecting discharged substantially outside the width of the fibrous web 1 side edges of the curtain 6 at the inlet side wall 11a hinged. With dashed lines and double arrow folding down the squeegee 10a and the entire pan 11 should be shown.
FIG. 1 also shows that the outlet-side side wall 11b of the collecting trough 11 is adapted to the outer shape of the body 4, ie the roller 4, and with its upper edge 11c facing the fibrous web side 1b extends far into an existing gusset 12 between the roller 4 and the web side 1b , As a result, the gusset 12 is protected from inflowing air boundary layer LG, whereby the running behavior of the fibrous web 1 is improved and the web web shown further down can be made to further treatment steps trouble-free.

Above all, however, the curtain 6 remains stable in the region of its impact at position P and thus ensures a high quality of the application layer 13 depositing on the fibrous web.

FIG. 2 likewise shows a fibrous web 1 coming from above, which in turn tapers toward the first body or the roller 2 for guiding and deflecting the web. Also, a curtain applicator 5 is assigned above the fibrous web 1 and the web page 1a. Dashed lines and arrows show that the commissioned work can be adjusted horizontally and / or vertically. This is in addition to the mobility for service purposes especially the impact angle β of the curtain 6 on the fibrous web 1 adjustable.

In contrast to the illustration shown in FIG. 1, the fibrous web 1 travels in a distance 3 rising at an angle α of approximately 30 ° to the second guide body or a second roller 4. As in FIG. 1, both rolls 1 and 4 are made with a relatively large diameter whose size is approximately 400 to 800 mm. Therefore, the first roller 2 is able to keep air curtain boundary layers LG reliably from the curtain on the coating side 1a. It is the second roller 4 Preferably, that at an appropriate rotational speed, an air cushion LP can form on the surface of the roller 4, so that in the case of the arrangement of the commissioned work 5 above the roller 4, the side edges of the curtain, which are delivered outside the web width, yet not the surface of the Can contaminate roller 4. The curtain side edges lie on the air cushion LP and are derived with the air cushion, in particular guided into a gutter.
If there is no or only insufficient air cushion, the curtain side edges lay down on the roller 4 and must be scraped free with blade elements.

Below the fibrous web 1 and the web side 1b, a collecting device 11 is likewise arranged as in FIG. This collecting device 11 is designed such that it simultaneously acts as an air boundary layer control device 10 against the with the fibrous web 1 on the side facing away from the curtain 6 web page 1 b air boundary layers LG.

The collecting device 11 is also trough-like with a continuous fibrous web 1 substantially parallel upper edge 11 c formed. This upper edge 11 c forms with the web side 1 b a distance a between 0 and 3mm. The device 11 can therefore touch the web 1 or even dip into a minus region of about 1 mm, without scratches on the web, abrasion dust and electrostatic charges are generated.

As is the case with FIG. 1, it can be seen from FIG. 2 that the collecting device 11 is in the area between the two bodies / rollers 2 and 4 leading the fibrous web 1 and also deflecting there, ie within the path 3 and below the impact position P of the opposite curtain 6 is arranged. At least one side wall of the collecting device 11, namely the outlet-side side wall 11 b and also a scraper plate 11 d attached thereto extends into the gusset 12 between the roller 4 and fibrous web side 1b.

The vertically drawn on the catcher double arrow to show the vertical adjustment. In addition, a pivoting of the device 11 is possible, but not shown separately.

Incidentally, the collecting device 11 is dimensioned longer than the web 1 is wide. In addition, the height of the collecting device 11 corresponds approximately to the size or the diameter of the second body. 4

Nachzutragen is still the center distance between the two guide or deflecting bodies 2 and 4, which is about 400 to 2000 mm.
The height of both bodies can be adjusted in such a way that the sloping or the guiding of the fibrous web 1 shown in FIG. 1 can be achieved.
FIG. 2 also shows a side plate 14 arranged above the coating side 1a. This is present on both sides of the machine and also serves to prevent inflowing air boundary layers LG in the direction of the curtain 6. His the curtain 6 end facing away from the curtain 6 at a distance b of about 30 mm. Its underside, which faces the web side 1a, has a distance c of 0 to 3mm. These dimensions ensure avoidance of the rebuilding of air boundary layers and thus contribute to the fact that the curtain can fall on the fibrous web 1 uninfluenced by harmful air influences.

FIG. 3 shows that the air boundary layer control device 10 is manufactured as a component separated from the catching device 11. At the web inlet and the web drain side are flexible squeegee 10 a, ideally not the fibrous web base 1b to touch, arranged. The device 10 could additionally be equipped with an air suction, not shown.

Figures 4 and 5 show an example in which the wiper strip 10a on the collecting device 11, that is arranged on a collecting trough, at the inlet side. The height adjustment should indicate the double arrow.

In Figure 4 , the working position of the wiper blade is shown, while Figure 5 shows a detailed representation in the pivoted or worn state of the catcher 11 with wiper blade 10a.
The pivoting of the combined components 10 and 11 and the height adjustment of the wiper strip 10a can be done both by motor, as well as manually.

FIG. 6 is intended to show overall possibilities for the course or running direction L of the fibrous web 1 immediately before and immediately after the coating with a curtain applicator 5, which is located above the fibrous web 1 in all variants shown. These possibilities are also applicable to the variants according to the figures 1 to 5. As a guide body so-called Airturns are shown as representative of all conceivable embodiments of control and deflection elements in Figure 6. These emit gas or impact air jets in the direction of the web side to be guided, as a result of which the fibrous web 1 is guided without contact.

FIG. 6a shows a web guide which resembles a downwardly open or inverted "U". The fibrous web 1 coming from below, initially up to a guide body 2, is deflected by this, then approximately horizontally or rising or falling also fed to another guide body 4 and is deflected by this again down. The guide bodies 2 and 4 are in this case both arranged below the fibrous web, between which there is still the air boundary layer removal device 10 and a collecting device 11, which, however, are indicated for reasons of clarity only in the figure 6a with arrows. Above the fibrous web 1 is the commissioned work 5, which has already been described in FIG. 1 and is therefore also indicated only by arrow 5.

Figure 6b shows in principle the same structure of the device, as in Figure 6a, except that this web guide is a "U" with in the end again upwardly running web. The guide bodies 2 and 4 are here associated with the coating side 1a.

Figures 6c and d each show an S-shaped web guide.
In Figure 6c , the fibrous web 1 comes from above, is deflected in an approximately horizontal direction and after an approximately horizontal or rising or falling track section, in the as in the other figures, the region of the coating with above the web 1 arranged curtain applicator 5 falls with the impact position P of the curtain 6, again deflected downwards.
The first guide body 2 is located at the first deflection above the web, ie on the coating side 1a and the second guide body 4 below the web. 1
The web guide shown here also corresponds to those of Figures 1 to 5 and is the preferred variant.

FIG. 6d shows a web guide that is exactly the opposite of the variant according to FIG. 6c.

Overall, the device according to the invention is characterized by its compactness and the uncomplicated retrofitting with various air boundary layer removal or control devices 10.

Despite the additional attachments with the retrofittable facilities, the curtain job is very variable to accomplish. It can be either supported as well as unsupported. Both variable angles of incidence, as well as various collection options during start / stop operation and during application are possible.

LIST OF REFERENCE NUMBERS

1

Fibrous web

2

first body

3

sloping route

4

second body

5

Curtain applicator

6

curtain

7

sealing strip

8th

bulkhead

9

Start / stop channel

10

Air boundary layer-fighting equipment

10a

squeegee

11

catcher

11a

inlet side wall

11b

drain side wall

11c

top edge

12

gore

13

application layer

A

Wheelbase

a

distance

L

direction

LG

Air boundary layer

P

Position or impact point

α

angle

Claims (15)

Device for applying a liquid to pasty medium, in particular aqueous pigment suspension, on a web page of a running paper, board or other fibrous web in their production and / or finishing, with a curtain applicator (5), which the application medium as substantially Gravitationally moving, free-falling, closed curtain (6) directly to the one web side or coating side (1a) of the moving fibrous web (1) emits and wherein the curtain (6) in a position (P) on a free train or track ( 3) or on a, the other side of the web (1 b) of the fibrous web (1) supporting area and wherein in the running direction (L) of the fibrous web (1) in front of the curtain (6) one of the coating side (1a) associated with air boundary layer weakening or removal device (2) is arranged,
characterized in that
a further air boundary layer control device (10) for with the fibrous web (1) flowing air boundary layers (LG) is provided, said control means (10) of the coating side (1a) opposite web side (1 b) in the region of the impact position (P) of the curtain (6) is assigned. Device according to claim 1,
characterized in that
a collecting device (11) for collecting the application medium in a tear of the fibrous web (1) and / or for dispensed side edges of the curtain (6) during the operating phase of the commissioned work (5) is provided. Device according to claim 2,
characterized in that
the collecting device (11) is designed such that it simultaneously acts as an air boundary layer control device (10) for the air boundary layers (LG) flowing with the fibrous web (1) on the web side (1b) facing away from the curtain (6). Device according to claim 2 or 3,
characterized in that
the collecting device (11) is trough-shaped with a continuous fibrous web (1) substantially parallel upper edge (11c) is formed and the upper edge (11 c) to the fibrous web (1) in the operating phase has a distance a between 0 and 3mm. Device according to claims 2 to 4,
characterized in that
the collecting device (11) is arranged in the region between two bodies (2, 4) guiding the fibrous web, at least one side wall (11b) of the collecting device (11) reaching at least one of the bodies (2, 4), in particular not touching and wherein the bodies are suitable for imparting a change of direction to the fibrous web (1). Device according to claims 2 to 5,
characterized in that
the collecting device (11) and the air boundary layer control device (10) is designed to be height-adjustable and / or swivelable. Apparatus according to claims 2 to 6,
characterized in that
the collecting device (11) is equipped with a hinged and / or height-adjustable air boundary layer stripping strip (10a) as an air boundary layer control device (10). Device according to claim 7,
characterized in that
the wiper strip (10a) is flexible. Device according to claims 2 to 8,
characterized in that
the collecting device (11) is dimensioned larger in its longitudinal extent than the fibrous web (1) is wide. Device according to claim 5,
characterized in that
the bodies (2, 4) are each designed as rotating rollers whose center distance (A) to each other between 400 and 2000mm, preferably between 500 and 1200 mm and which are adjustable in height to each other so that a straight or sloping or rising guide the fibrous web (1) can be reached at an angle (α) between 10 and 40 °. Apparatus according to claim 1 or 7,
characterized in that
the air boundary layer control device (10) is wider than the fibrous web (1) and / or the fibrous web leading body (2, 4) is formed. Device according to one or more of the preceding claims,
characterized in that
the height of the collecting device (11) and / or the air boundary layer fighting device (10) corresponds approximately to the size or the diameter of the second body (4). Device according to claim 5,
characterized in that
at least one of the two bodies (2, 4) standing, that is not designed to rotate. Device according to one or more of the preceding claims,
characterized in that
the fibrous web (1) after passing through the last body (4) takes a downwardly directed path (L). Device according to one or more of the preceding claims,
characterized in that
the position of the commissioned work (5) and thus the impact position (P) of the curtain (6) with respect to the web longitudinal direction up to a fibrous web (1) supporting area is adjustable.

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