EP0642613A1 - DEVICE FOR COATING A BAND OF PAPER OR CARDBOARD. - Google Patents

Abstract

Prior art devices for coating continuous strips of paper or cardboard (1) exist which have a counter-roller round which the paper or cardboard (1) passes, an application system (3) which applies an excess of coating material to the paper or cardboard (1), and a metering system (4) disposed a certain distance downstream from the application system (3) and fitted with a doctor blade. The application system (3) includes an application roller (8), driven to rotate, with a smooth surface which, together with the counter-roller (2), forms an application gap (9) to which excess coating material is fed in the same direction as the direction of motion of the paper or cardboard. The invention calls for the application roller (8) to have a diameter of 5 to 200 mm, preferably 10 to 150 mm, and to form together with the counter-roller (2) an application gap (9) of 0.01 to 2 mm, preferably 0.05 to 1 mm, these figures being in addition to the thickness of the paper or cardboard, and the rear side of the application roller (8) i.e. that remote from the counter-roller (2), rests, over the whole working width of the roller, against a mounting (12, 26, 27) which is rigid in the direction radial to the counter-roller (2) to prevent bending.

Description

 DESCRIPTION

Device for coating a paper or cardboard web

Technical field

The invention relates to a device for coating a paper or cardboard web according to the preamble of patent claim 1.

For coating paper or cardboard webs, devices are known with a counter-roll deflecting the web, in which an application system in the area of the counter-roller wrapped by the web applies the coating material in excess to the web, and a metering system with a distance behind the application system in the web running direction a squeegee element is arranged, which strips off the excess up to the desired coat weight.

State of the art

In the generic coating devices known from DE-PS 36 23 402, the application system consists of an application roller which can be rotated by means of a drive and which forms a coating gap with the counter roller, to which coating material is supplied in excess from the web entry side. An essential feature of this application system, which is referred to as a roller application unit (flooded nip coater), is that there is a fixed gap between the counter roller and the application roller, so that it is not pressed against the web. Furthermore, the coating material is fed to the application gap with the lowest possible pressure, it being necessary to ensure that the application gap is completely filled for a uniform coating. DE-OS 37 35 889 describes a so-called short dwell coater with an application chamber which is open to the counter roll, into which coating material is fed under higher pressure and which is closed at the web exit end by a doctor element pressed against the counter roll. The application chamber is used as a pre-metering device, at the outlet end of which a doctor blade rod with circumferential grooves is arranged, which is pressed onto the material web or counter roller by means of a pressure hose.

Presentation of the invention

Due to the constantly increasing web widths (8 m and more) and increasing machine speed (800 m / min and more) in paper production, the application rollers of roller applicators must have larger and larger diameters so that they are sufficiently stable, on the one hand, to keep the application gap constant across the width hold, i.e. no disturbing deflection occurs, and on the other hand to avoid disturbing dynamic effects (vibrations). In addition to the greater design effort, a large application roller diameter has the disadvantage that the metering system must be arranged at a relatively large distance from the application gap due to the large installation space. A long penetration distance between application and doctoring can lead to larger minimum coat weights because the material that has penetrated the web can no longer be doctored.

The invention has for its object to improve a generic coating device so that at high web speeds and large web widths with a lower design effort, a uniform application can be achieved even with a small excess.

This object is achieved with the features of claim 1.

In addition to the lower design effort, the metering system can advantageously be arranged at a short distance behind the application system due to the small diameter of the application roller. The support of the application roller considerably reduces deflection effects due to its own weight or hydrodynamics in the application gap, so that even smaller gap widths can be adjusted to - if desired - evenly apply a small excess.

Furthermore, the application system according to the invention also has procedural advantages:

The smaller diameter of the application roller leads to a significantly lower hydrodynamic pressure in the application nip, especially in the case of wide and fast devices. This results in less penetration of the coating material into the web, with advantageous effects on the quality, especially with lower coat weights. Line errors due to film splitting and tension line formation are also significantly reduced.

The subclaims contain preferred, since particularly advantageous, embodiments of the invention:

When storing the applicator roller in a bed according to claim 2, the deflection effects are minimal and the elasticity of the system can be adjusted to desired values.

In the embodiment according to claim 3, the elasticity of the application roller-bed-holder system is sufficiently low to ensure the stability of the gap against the hydrodynamic pressure. In the particularly advantageous embodiment according to claim 4, the stability of the gap does not impair elasticity, so that the applicator roller in the event of malfunctions, for. B. can avoid a continuous glue point.

While in the embodiment according to claim 5 a secure hold of the applicator roller in the bed is guaranteed, claim 6 contains an advantageous embodiment of the bed for lubricating and cleaning the applicator roller, preferably with water.

A lip-shaped inner wall of the bed according to claim 7 keeps the applicator roller clean by scraping off adhering contaminants when rotating. Claim 8 contains an advantageous structural design of the bed of the applicator roller in order to be able to replace it quickly and easily if necessary.

The embodiment according to claim 9 with the baffle has the advantage that even larger gap widths of the application gap can be set without uncovered areas occurring. The baffle separates the incoming and the recycled coating material, thus avoiding turbulence in the application gap.

The embodiment with a baffle arranged in a paint chamber according to claim 10 brings about a comparative, calm feeding of coating material into the application gap.

A scraper knife arranged in front of the applicator roller according to claim 1 1 considerably reduces the entry of air into the coating material by the web.

Brief description of the drawing

The drawing serves to explain the invention with reference to an embodiment shown in simplified form. Show it:

Figure 1 is a side view of a coating device with an application system according to the invention, in which the application roller is stored in a bed

Figure 2 is an enlarged view of the application system.

The figures

3 and 4 show embodiments with a coating device in which the application roller is supported by a bearing.

Ways of Carrying Out the Invention

The coating device has a driven counter-roller 2 deflecting the paper or cardboard web 1, in the area of which the web 1 wraps Application system 3 and in the web running direction at a distance behind a metering system 4 is arranged, which contains a doctor blade 5 as a doctor element. The scraper knife 5 is clamped in a known manner with its foot in a clamping bar 6 which can be displaced in the direction of the counter roll 2. The clamping bar 6 is mounted in a pivotable scraper bar 7, so that the contact pressure of the scraper knife 5 and the blade angle (= angle of the scraper knife 5 to the tangent of the counter-roller 2) can be adjusted.

The application system 3 shown enlarged in FIG. 2 contains an application roller 8 connected to a rotary drive with a diameter of 5 mm to 200 mm, preferably 10 mm to 150 mm, which is arranged axially parallel to the counter roller 2 in such a way that between the web 1 the narrowest point forms an application gap 9 of 0.01 mm to 2 mm, preferably 0.05 mm to 1 mm. The smallest distance from the counter roll 2 is therefore these values plus the paper or cardboard thickness of the web 1. The axial length of the applicator roller 8 extends at least over the length of the counter roller 2, that is to say the maximum web width. It is preferably made of steel with a smooth outer surface and on its back facing away from the counter-roller 2 over the entire working width, i.e. supported over its entire length against deflection. In the embodiment according to FIGS. 1 and 2, the applicator roller 8 is mounted in a bed 10, 11 made of a limited elastic, rubber-like material open to the counter roller 2. In the present example, the bed 10, 1 1 is made of rubber and consists of two mirror-symmetrical parts 10, 1 1, which are fitted into a holder 12 so as to be movable relative to and away from one another.

The holder 1 2 extends like the bed 10, 1 1 over the entire working width and is made of a rigid material, for. B. aluminum. In the present exemplary embodiment, the holder 12 has a central slot which extends radially to the counter-roller 2 and is fitted in a U-shaped carrier 13 which is screwed onto a pivotable cross member 14. On one side, between the holder 12 and one leg of the carrier 13, a pressure hose 15 extends over the working width, with which the two parts of the holder 12 can be compressed so that the bed 10, 11 holds the applicator roller 8 securely. So that despite the clamping force generated between the two parts of the holder 1 2, the applicator roller 8 can rotate as little friction as possible, the inner walls of the bed 10, 1 1 are designed so that they rest only in sections on the applicator roller 8. At least one inner wall is preferably designed in the form of an axially extending lip in order to Rotate the application roller 8 scrape off adhering contaminants. In addition, 8 open channels 16 are incorporated into the inner walls of the applicator roll, into which water is introduced as a lubricant and cleaning agent during operation. For a secure hold of the applicator roller 8, it is covered on its outer circumference in a range of at least 180 ° by the bed 10, 1 1. To replace an applicator roller 8, the pressure hose 15 is relieved, thereby opening the two parts 10, 11 of the bed, and the applicator roller 8 can be removed.

It is essential for the invention that the application roller 8 is supported over the entire working width in such a way that the set gap width of the application gap 9 is retained at the hydrodynamic pressure that occurs. In the embodiment shown in Figures 1 and 2, the applicator roller 8 is held by a bed 10, 1 1, which is fitted in a holder 12 which is rigidly configured radially to the counter-roller 2 and is immovably and rigidly stored in the working position. In order to maintain the gap width, in this embodiment the restoring force of the system application roller 8 - bed 10, 1 1 - holder 1 2 against deflection in the radial direction away from the counter roller (2) is at least 1 * 10 ^β N * x * y, preferably more than 5 * 10 ^β N * x * y; with x = axial length of the application roller (in [m]) and y = deflection radially from the counter roller 2 (in [m]).

So that the order roll 8 in the event of a fault, eg. B. if a thickened adhesive point of the web 1 runs through, can dodge to a limited extent, the restoring force of the system application roller 8 - bed 9 - holder 12 is preferably additionally less than 2 * 10 ⁷ N * x * y, preferably less than 1 * 10 ⁷ N * x * y; with x = axial length of the application roller (in [m]) and y = deflection radially from the counter roller 2 (in [m]). This low elasticity prevents damage without impairing the stability of the application gap 9.

The supply of coating material into the application gap 9 takes place on the inlet side via a feed channel 17 which is formed by a guide plate 18 which extends into the vicinity of the application gap 9 and the inlet-side flank of the holder 1 2 or the circumference of the application roller 8. The feed channel 17 extends at an acute angle to the tangent to the counter roller 2 in the application nip 9. It is connected to an ink chamber 19 which extends over the entire working width and which is connected via an inlet side Distribution pipe 20 coating material is supplied. The back of the guide plate 18 facing away from the application roller 8 is designed as a drainage surface for excess coating material. The guide plate 18 thus separates the supply of the coating material conveyed in excess into the application gap 9 from the return. This avoids turbulence in the coating material, and the excess rate can be set to lower values or the application gap to larger values without uncovered areas occurring. The returned coating material is collected in an ink pan 21 and returned to the ink chamber 19.

In the ink chamber 19 there is a guide plate 22 which extends over the working width and radially to the counter roller 2 and ends at a distance from the chamber bottom. The guide plate 22 forms with the outlet-side wall of the ink chamber 19 a channel 23 with a slot-shaped inlet opening, which opens into the feed channel 19. As a damming wall opposite the distributor pipe 20, it prevents irregularities in the supplied coating material from propagating into the feed channel 17 and thus equalizes the pressure and the flow conditions in this and in the application gap 9. At the same time, the guide plate 22 enables the ink chamber 19 to be vented without unevenness in the supply of coating material in the application gap 9. In this way, unwanted air pockets can be removed from the coating material.

On the inlet side, in front of the applicator roller 8, a scraper knife 24 is arranged at a short distance in front of the guide plate 18 and approximately parallel to it, the scraper knife 24 resting against the web 1 with its tip. The scraper knife 24 is shown in FIGS. 1 and 2; it can also be used in the embodiments according to FIGS. 3 and 4. The scraper knife 24, which extends over the entire web width, removes the air adhering to the surface of the web 1 before the web enters the application gap 9. Air introduced into the coating material from the web 1 leads to undesirable irregularities in the line diagram after the metering. The negative effects resulting from the introduced air are considerably reduced by the doctor knife 18 and / or the ventilation of the coating material in the ink chamber 19.

The application systems 3 according to FIGS. 3 and 4 each contain an application roller 8 with a larger diameter between 50 mm and 200 mm, preferably between 50 mm and 1 50 mm. Such application rollers 8 are hung with roller journals on their end faces in pivot bearings which are fastened on both long sides of the frame. In addition, a support bearing 26, 27 is arranged between the crossmember 14 and the application roller 8 as a holder, which extends over the entire working width (ie the length of the application roller 8) and deflections of the application roller 8 due to their own weight and / or the hydrodynamic pressure in the application gap 9 prevented.

The support bearing 26, 27 is preferably shaped on its surface facing the application roller 8 in such a way that the application roller 8 is supported flatly. Each support bearing 26, 27 is made of a hard material with low friction to the applicator roller 8, preferably hard rubber or rubber-like plastic, if the applicator roller 8 coated with hard metal, z. B. chrome, or made of a hard metal, if the applicator roller 8 is coated with rubber or a rubber-like plastic.

The surface of the support bearing 27 according to FIG. 4, which bears against the application roller 8, is lip-shaped, similar to the bed 10, 11 according to FIG. 2, on the inlet and outlet sides, so that adhering impurities are scraped off when the application roller 8 is rotated. There are open to the applicator roller 8 and extending their axial direction channels 28 into the support bearing 27, in which a lubricant or cleaning agent, for. B. water can be introduced.

Depending on the application, the application roller 8 is driven with or in the opposite direction to the counter roller 2. The co-operation of the applicator roller 8 has the advantage that the applicator roller 8 also draws from the feed channel 17 and thus supports the filling of the application gap 9. In opposite operation, film splitting effects and tension line formation are advantageously further reduced. The peripheral speed of the application roller 8 during application is greater than 0 m / min and less than 100 m / min, preferably it is between 2 m / min and 20 m / min.

The application system 3 is thus able to evenly apply small excess amounts to the web 1. The excess is scraped off again by the scraper knife 5 of the subsequent metering system 4 to the desired coat weight and returned to an ink pan 25.

Claims

PATENT TO PRÜCHE 1. Device for coating a paper or cardboard web (1) with a counter roller (2) deflecting the web (1), an application system (3), the coating material in excess on the Applies web (1), and a metering system (4) with a doctor element (5) arranged at a distance behind the application system (3) in the web running direction, the application system (3) containing an application roller (8) with a smooth outer surface that can be rotated by a drive, which forms an application nip (9) with the counter roller (2), to which coating material is supplied in excess from the web entry side, characterized in that the application roller (8) has a diameter of 5 mm to 200 mm, preferably 10 mm to 150 mm , with the counter roller (2) forms an application gap (9) of 0.01 mm to 2 mm, preferably 0.05 mm to 1 mm, plus the paper or cardboard thickness, and on its rear side facing away from the counter roller (2) from a rigid radially to the counter roller (2), in the working position immovable holder (12, 27, 28) over the entire Working width is supported against deflection. Second Apparatus according to claim 1, characterized in that the applicator roller (8) is mounted in a bed (10, 11) which extends over the working width and is open to the counter-roller (2) and which is made of a limited elastic, rubber-like material and in the holder (12) is fitted. 3rd Apparatus according to claim 2, characterized in that the restoring force of the application roller system (8) - bed (10, 11) - holder (12) against deflection in the radial direction from the counter roller (2) is at least 1 * 10 ^β N ^# x * y , preferably more than 5 * 10 ^β N * x * y; with x = axial length of the application roller (in [m]) and y = deflection radially from the counter roller (2) (in [m]). 4th Device according to claim 3, characterized in that the restoring force of the application roller system (8) - bed (10, 11) - holder (12) is less than 2 x 10 ⁷ N * x * y, preferably less than 1 * 10 ⁷ * N * x * y is; with x = axial length of the application roller (in [m]) and y = deflection radially from the counter roller (2) (in [m]). 5th Device according to one of claims 2 to 4, characterized in that the bed (10, 11) comprises the application roller (8) on its outer circumference in a range of at least 180 °. 6th Device according to one of claims 2 to 5, characterized in that the bed (10, 11) contains one or more channels (16) which are open to the application roller (8) and run parallel to the axis of the application roller (8). 7. Device according to one of claims 2 to 6, characterized in that at least one inner wall of the bed (10, 11) bearing against the applicator roller (8) is designed as a lip which extends in the axial direction. 8th. Device according to one of claims 2 to 7, characterized in that the bed consists of two parts (10, 11) which are mounted for holding and removing the application roller (8) in the holder (12) against each other and movable away from each other. 9th Device according to one of claims 1 to 8, characterized in that on the inlet side of the application roller (8) is arranged a guide plate (18) which extends into the vicinity of the application gap and which is connected to the inlet-side flank of the holder (12) or with the circumference of the roller (8) forms a feed channel (17) running at an acute angle to the tangent of the counter-roller (2) and the back of the roller (8) facing away from it is designed as a drainage surface for excess coating material. 10th Device according to one of claims 1 to 9, characterized by the fact that on the inlet side of the application roller (8) there is arranged a feed channel (17) which extends into the vicinity of the application gap (9) and which connects to an ink chamber (19) with a Supply (20) for coating material is connected, wherein in the ink chamber (19) over the working width and radially to the counter-roller (2) extending baffle (22) is arranged, which ends at a distance from the bottom of the ink chamber (19) and with outlet-side wall of the ink chamber (19) forms a channel (23) with a slot-shaped inlet opening, which opens into the feed channel (17). 11th Device according to one of claims 1 to 10, characterized in that a scraper knife (24) which extends over the entire width of the web and whose tip lies against the web (1) is arranged on the inlet side in front of the application roller (8).