EP2872334B1 - Screen printing device for applying a colour - Google Patents

Description

The invention relates to a screen printing apparatus for applying a paint, a method for applying a paint, in particular Einbrennfarbe, on a disc and their use.

In screen printing, paints are applied through a sieve to the object to be printed using a rubber squeegee. There are various possibilities of executing the printing process. When Flachbettsiebdruck the object to be printed on a flat surface, such as a table is placed. In a next step, the screen template is placed flat on a frame on the object. With the help of a squeegee, the color is then pushed through the mesh of the screen. If articles are to be printed continuously, the printing can take place via a rotating screen-printing hollow cylinder or else a screen-printing drum. The outer lining of the drum is at least partially formed by a printing screen in this embodiment. This printing screen transmits the ink on contact with the surface to be printed using a squeegee located in the screen printing drum. The screen-printing drum can be used in combination with a treadmill for the continuous printing of, for example, panes. Ink residues settling on or in the stitches can be removed within the screen printing drum by means of a second doctor blade and, for example, transferred to a roller in contact with the screen printing drum. Especially with changing geometries or dimensions of the objects to be printed can otherwise easily get stuck paint residues in the Siebmaschen and accumulate under circumstances or even harden in the worst case and clump together. These paint residues can easily lead to ghosting or blurry images or patterns.

Particularly in the field of automobile glazing, screen printing is of great importance. In the border area of many different panes, for example, splices must be optically covered. Especially windscreens have an extensive edge pressure, which is clearly visible. In addition to covering contact or splices play but also increasingly the look and design of the windshield edge a greater role.

An important cost factor in the production of a finished printed vehicle window is the cycle time and the stability of the process. This also plays a role in the printing of the disc edges with a stoving paint. Baking colors often contain color pigments on ceramic glazes or enamel, for example silicates and oxides. These stains are "cured" by heating to form a stable, chemically stable and glassy coating. In many cases, this heating process can also be integrated into the tempering process. Established processes enable, for example, printing speeds of 3 m to 4 m per minute. However, these print speeds are often not fast enough to cost-effectively enable a process such as the manufacture of car glazing. Only at faster cycle times, these processes are cheaper.

DE 2247570 A1 discloses a silk screen printing press.

GB1,526,213 A discloses a printing machine for printing paper cartons. The printing press has a hollow cylindrical structure.

DE 41 09 707 C1 discloses a screen printing method for printing glass sheets with a decorative layer. When applying the decorative layer, a printing screen is used whose surface extends beyond the peripheral surface of the glass sheet.

DE 198 32 414 A1 discloses a screen printing method for printing flat and flat objects, such as glass. The screen printing device comprises both a hollow cylindrical screen stencil and a color removal roller.

The object of the invention is to provide a screen printing device which allows a reproducible, precise printing of different sized discs with a high and faster clock frequency.

The object of the present invention is achieved by a device according to independent claim 1. Preferred embodiments will become apparent from the dependent claims.

An inventive method for printing a disc and its use are apparent from further independent claims.

The screen printing device according to the invention for applying a paint comprises at least one treadmill or assembly line. A rotating hollow cylindrical screen with a peripheral screen as the printing surface is placed above the belt together with an adjacent placed rotary paint stripper. The term "above" means in the context of the invention on the treadmill, but with pressure contact of the rotating screen with an object to be printed. In a preferred embodiment, the rotating hollow cylindrical screen template and the color removal roller are arranged vertically and longitudinally adjustable over the treadmill. Within the screen template, a paint supply device, for example a valve or hoses connected via lines to a paint reservoir, is arranged. The screen template further includes a first squeegee adjacent the treadmill and a second squeegee adjacent to the color removal roller. A third squeegee is arranged in the direction of travel of the treadmill and / or the direction of rotation of the screen template in front of the first squeegee. The term "in the direction of rotation" for the purposes of the invention includes a positioning of the third doctor in front of the first doctor with respect to the running direction of the treadmill. The third squeegee fills the mesh of the rotating screen with the ink, the first squeegee presses the ink onto the plate or substrate to be printed and allows adhesion of the ink to the surface of the wafer by means of adhesion. The combination of third squeegee and first squeegee improves and increases the process speed of the device according to the invention. The rotating hollow cylindrical screen template can thus be moved faster with a higher turn. The pane preferably includes glass panes, more preferably glass panes of different size or dimensioning. Excess or unused color due to the geometry of the disk is transferred to the paint stripping roller via the second squeegee. The distance between the screen and the ink removal roller is set so that both rotate independently of each other and at the same time the ink residues can be transferred.

Between the third squeegee and the second squeegee, a feed trough is preferably arranged. The feed chute allows the transport of excess paint which runs back from the screen within the screen stencil over the second squeegee and can not be transferred to the ink removal roller. Above all, the second squeegee transfers the color present in sieve meshes to the ink removal roller. The paint located on the webs of the screen runs mostly over the second squeegee back into the interior of the rotating hollow cylindrical screen template. About the feed channel, the excess color returns to the third squeegee and is entered from there back into the sieve.

The ink removal roller preferably comprises a paint collecting container. The paint catcher collects the paint collected by the paint stripper. In an optional embodiment, the ink collected in the ink removal roller can be returned via hoses back into the rotating hollow cylindrical screen template.

The color removal roller preferably comprises a color scraper. The color scraper allows the transfer of the paint located on the color removal roller into the paint collector.

The ink supply device preferably comprises hoses or nozzles. The ink supply device introduces new paint into the rotating hollow cylindrical screen template. Optionally, the ink supply device can also be coupled with the ink collecting container and reuse ink already used. This color feedback lowers the production costs.

The screen template preferably has a hole diameter of 40 .mu.m to 70 .mu.m. The individual mesh width depends on the motif to be printed and the composition, viscosity and wetting of the color.

The color preferably contains stoving paint. The stoving paint may preferably be cured on the disc following the bending process following the inking. Alternatively, a separate heating process, preferably at 500 ° C to 800 ° C is possible.

The invention further comprises a method for printing a pane with a screen printing device according to the invention. In a first step, a disc is placed on a treadmill or assembly line. The disc located on the treadmill is printed on a rotating hollow cylindrical sieve with a rotating sieve. Simultaneously, ink is introduced via a paint supply device continuously or as needed within the hollow cylindrical screen. The paint is partially introduced on the rotating screen via a third doctor blade. The third squeegee thus allows a defined (pre) filling of the screen with color. The disk is positioned on the treadmill below the rotating hollow cylindrical screen. The paint is applied over the first squeegee through the screen on the disk. The (pre-) filling the screen with paint via the third doctor reduces the amount of ink present in the area of the first doctor blade. Larger amounts of ink in the area of the first doctor blade often lead to clumping or smearing on the disk to be printed. The disc leaves in the next step, the hollow cylindrical screen template on the treadmill. The remaining ink within the screen is transferred via a second doctor blade to an adjacent rotating paint stripper roller.

The paint on the disc is preferably baked. The baking process improves the stability and durability of the paint.

The disc is preferably preloaded or partially preloaded. The tempering process of the disk is preferably used for baking the paint. The integration of the burn-in process into the tempering process makes a separate burn-in process superfluous and thus saves process energy.

The treadmill is preferably moved at a speed of 5 m / min to 20 m / min, more preferably 10 m / min to 17 m / min, in particular greater than 30 m / min. This speed allows compared to the prior art, a more cost-efficient printing process at significantly higher cycle times.

The hollow cylindrical sieve stencil and the ink removal roller preferably rotate in opposite directions.

The invention further includes the use of the screen printing apparatus for applying a paint, preferably a stoving paint.

In the following the invention will be explained in more detail with reference to a drawing. The drawing is a purely schematic representation and not to scale. It does not limit the invention in any way.

Figur 1

einen Querschnitt einer Siebdruckvorrichtung nach dem Stand der Technik,

Figur 2

einen Querschnitt der erfindungsgemäßen Siebdruckvorrichtung,

Figur 3

einen Querschnitt des Siebes der rotierenden hohlzylindrischen Siebschablone und

Figur 4

ein Fliesschema des erfindungsgemäßen Verfahrens zum Bedrucken einer Scheibe.

Show it:

FIG. 1

a cross section of a screen printing device according to the prior art,

FIG. 2

a cross section of the screen printing device according to the invention,

FIG. 3

a cross section of the screen of the rotating hollow cylindrical screen template and

FIG. 4

a flow diagram of the method according to the invention for printing a disc.

FIG. 1 shows a cross section of a screen printing apparatus (I) according to the prior art. The screen-printing device for applying a paint (12) comprises at least one moving belt (3) moved in the direction (C) or else an assembly line. A hollow-cylindrical screen template (1) rotating in the direction (A) with a rotating screen (13) as printing surface, not shown, is arranged above the conveyor belt (3) together with an adjacently placed color removal roller (3) rotating in direction (B). Within the screen template (1) is a paint supply device (8), for example, a connected via lines with a paint reservoir valve or hoses arranged. The screen template (1) further includes a first squeegee (4) adjacent to the treadmill (3) and a second squeegee (5) adjacent to the color removal roller (2). The first squeegee (4) fills the stitches of the rotating screen (13) (not shown) with the ink (12) and presses the ink (12) onto the plate (10) or substrate to be printed and allows adhesion of the ink (12) the surface of the disc (10) by means of adhesion. The pane (10) preferably includes glass panes, more preferably glass panes of different size or dimensioning. Excess or due to the geometry of the disc (10) not used ink (10) is transferred via the second doctor blade (5) on the color removal roller (2). The ink removing roller (2) includes a paint collecting container (11). The ink collecting container (11) collects the ink (12) collected by the paint removing roller (2) by means of a paint doctor (6). However, the structure of the prior art shown only allows relatively low cycle times in the printing. The achievable printing speeds, ie the running meter of glass which can be printed per minute, are in the range of 3 m to 4 m per minute.

FIG. 2 shows a cross section of the screen printing device (II) according to the invention. The basic structure corresponds to that in FIG. 1 shown. The ink (12) is introduced via a third doctor blade (7) partly on the revolving screen (13), not shown. The third doctor blade (7) thus enables a defined pre-filling of the screen (13) with ink (12). The disc (10) is positioned on the treadmill (3) below the rotating hollow cylindrical sieve template (1). The ink (12) is then applied via the first doctor blade (4) through the sieve (13) on the disc (10). Between the third squeegee (7) and the second squeegee (5) a feed chute (9) is arranged. The feed chute (9) allows the removal of excess ink (12) which runs back from the wire (13) via the second doctor blade (5) and can not be transferred to the ink removal roller (2). The second squeegee (5) transfers, in particular, the ink (12) present in sieve meshes to the ink removal roller (2). The color (12) located on the webs of the screen (13) largely returns to the interior of the rotating hollow-cylindrical screen template (1) via the second squeegee (5). Without feeding channel (9), this ink (12) would accumulate in the region of the first doctor blade (4) and hinder the printing process there. This can lead to a blurring of the printed image with larger amounts of ink. Instead, the excess ink passes largely through the feed channel (9) back to the third doctor blade (7) and is reintroduced from there into the sieve (13). The achievable printing speeds of the device according to the invention are in the range of at least 15 m to 20 m, preferably greater than 30 m per minute. The inventive device therefore allows an acceleration of the cycle time by a factor of 3 to 4. The significantly higher cycle time also significantly reduces the cost per printed disc (10).

FIG. 3 shows a cross section of the screen (13) of the rotating hollow cylindrical screen template (1). The structure corresponds to the in FIG. 2 shown. The third squeegee (7) allows a defined pre-filling of the screen (13) with ink (12) and the first doctor blade (4) applying the ink (12) through the sieve (13) in the direction of (C) moving disc (10). The feed channel (9) transports the excess ink (12) again to the third doctor blade (7) and is reintroduced from there into the sieve (13).

FIG. 4 shows a flow diagram of the method according to the invention for printing a disc (10). In a first step, a disc (10) on a treadmill (3) or assembly line is arranged. Within the hollow cylindrical screen template (1), ink (12) is filled continuously or if necessary via an ink feed device (8). The ink (12) is introduced via a third doctor blade (7) partially on the rotating screen (13). The disc (10) is positioned on the treadmill (3) below the rotating hollow cylindrical sieve template (1). The paint (12) is applied via the first doctor blade (4) through the screen (13) on the disc (10). The (pre-) filling of the screen (13) with ink (12) via the third doctor blade (7) in the preceding step reduces the amount of ink present in the region of the first doctor blade (4). These often lead to clumping or smearing on the disc to be printed (10). The disc (10) leaves in the next step on the treadmill (3), the hollow cylindrical screen template (1). The ink (12) remaining within the screen (13) is transferred via a second doctor blade (5) to an adjacent rotating paint stripper roller (2).

LIST OF REFERENCE NUMBERS

(A), (B) and (C)

direction

(I)

Screen printing device according to the prior art

(II)

Screen printing device according to the invention

(1)

rotating hollow cylindrical sieve template

(2)

Color removal roller

(3)

treadmill

(4)

first squeegee

(5)

second squeegee

(6)

paint scraper

(7)

third squeegee

(8th)

Color feeder

(9)

feeding trough

(10)

disc

(11)

Color collection container

(12.)

colour

(13)

scree

Claims (14)

1. Screen printing device for applying an ink, comprising at least:

   a. a conveyor belt (3),

   b. a rotating hollow cylindrical screen stencil (1) arranged above the conveyor belt (3) with a circumferential screen (13) and a rotating ink removal cylinder (2) arranged adjacent the screen stencil (1), wherein

   c. inside the screen stencil (1) are an ink supply device (8), a first doctor blade (4) adjacent the conveyor belt (3), a second doctor blade (5) adjacent the ink removal cylinder (2), and
   a third doctor blade (7), which is arranged upstream of the first doctor blade (4) in the running direction of the conveyor belt (3) and/or the rotational direction of the screen stencil (1).
2. Screen printing device according to claim 1, wherein a supply channel (9) is arranged between the third doctor blade (4) and the second doctor blade (5).
3. Screen printing device according to claim 1 or 2, wherein a pane (10) is arranged on the conveyor belt (3).
4. Screen printing device according to one of claims 1 through 3, wherein the ink removal cylinder (2) includes an ink collection container (11).
5. Screen printing device according to one of claims 1 through 4, wherein the ink removal cylinder (2) includes an ink scraper (6).
6. Screen printing device according to one of claims 1 through 5, wherein the ink supply device (8) includes hoses or nozzles.
7. Screen printing device according to one of claims 1 through 6, wherein the screen stencil (1) has a mesh hole diameter from 40 µm to 70 µm.
8. Screen printing device according to one of claims 1 through 7, wherein the ink (12) contains baking ink.
9. Method for printing a pane with a screen printing device according to one of claims 1 through 8, wherein a pane (10) on a conveyor belt (3) is printed via a rotating hollow cylindrical screen stencil (1) with a circumferential screen (13), wherein

   a. inside the hollow cylindrical screen stencil (1), ink (12) is filled via an ink supply device (8),

   b. the ink (12) is introduced via a third doctor blade (7) on the circumferential screen (13),

   c. the pane (10) on the conveyor belt (3) is positioned below the rotating hollow cylindrical screen stencil (1),

   d. the ink (12) is applied on the pane (10) via the first doctor blade (4) through the screen (13) and the pane (10) leaves the hollow cylindrical screen stencil (1) on the conveyor belt (3), and the ink (12) remaining inside the screen (13) is transferred via a second doctor blade (5) to an adjacently arranged rotating ink removal cylinder (2).
10. Method according to claim 9, wherein the ink (12) situated on the pane (10) is baked.
11. Method according to claim 9 or 10, wherein the pane (10) is prestressed or partially prestressed.
12. Method according to one of claims 9 through 11, wherein the conveyor belt (3) is moved at a speed from 5 m/min to 20 m/min, preferably 10 m/min to 17 m/min, particularly preferably greater than 30 m/min.
13. Method according to one of claims 8 through 11, wherein the hollow cylindrical screen stencil (1) and the ink removal cylinder (2) rotate in opposite directions.
14. Use of the screen printing device according to one of claims 1 through 8 for applying an ink, preferably baking ink.

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