Abstract
Screen printing device for applying an ink, having at least: a) a conveyor belt, b) a rotating hollow cylindrical screen stencil arranged above the conveyor belt with a circumferential screen and a rotating ink removal cylinder arranged adjacent the screen stencil, wherein: c) inside the screen stencil an ink supply device, a first doctor blade adjacent the conveyor belt, a second doctor blade adjacent the ink removal cylinder, and a third doctor blade, which is arranged upstream of the first doctor blade in the running direction of the conveyor belt and/or the rotational direction of the screen stencil are provided.
Claims
1. A screen printing device for applying an ink onto a pane, comprising: a conveyor belt for conveying the pane; and a rotating hollow cylindrical screen stencil arranged above the conveyor belt with a circumferential screen and a rotating ink removal cylinder arranged adjacent the screen stencil, the rotating ink removal cylinder being distanced from the rotating hollow cylindrical screen stencil so that both can rotate independently of each other, wherein inside the screen stencil are an ink supply device, a first doctor blade adjacent the conveyor belt for applying ink on the pane, a second doctor blade adjacent the ink removal cylinder for transferring ink to the ink removal cylinder, and a third doctor blade for filling meshes of the circumferential screen with ink, which is arranged upstream of the first doctor blade in the running direction of the conveyor belt, wherein a supply channel is arranged between the third doctor blade and the second doctor blade for supplying ink from the second doctor blade to the third doctor blade, and wherein the second doctor blade is positioned above the third doctor blade so as to allow flow of ink under gravity through the supply channel.
2. The screen printing device according to claim 1, wherein the ink removal cylinder includes an ink collection container.
3. The screen printing device according to claim 1, wherein the ink removal cylinder includes an ink scraper.
4. The screen printing device according to claim 1, wherein the ink supply device includes hoses or nozzles.
5. The screen printing device according to claim 1, wherein the screen stencil has a mesh hole diameter from 40 μm to 70 μm.
6. The screen printing device according to claim 1, wherein the ink contains baking ink.
7. A method for printing a pane with the screen printing device according to claim 1, wherein a pane on a conveyor belt is printed via a rotating hollow cylindrical screen stencil with a circumferential screen, comprising: inside the hollow cylindrical screen stencil, ink is filled via an ink supply device, meshes of the circumferential screen are filled with ink via a third doctor blade on the circumferential screen, the pane on the conveyor belt is positioned below the rotating hollow cylindrical screen stencil, ink is applied on the pane via a first doctor blade through the screen, the pane leaves the hollow cylindrical screen stencil on the conveyor belt, the ink remaining inside the screen is transferred via a second doctor blade to an adjacently arranged rotating ink removal cylinder, the rotating ink removal cylinder being distanced from the rotating hollow cylindrical screen stencil so that both can rotate independently of each other, and ink is supplied from the second doctor blade to the third doctor blade via a supply channel, wherein the second doctor blade is positioned above the third doctor blade so as to allow flow of ink under gravity through the supply channel.
8. The method according to claim 7, wherein the ink situated on the pane is baked.
9. The method according to claim 7, wherein the pane is prestressed or partially prestressed.
10. The method according to claim 7, wherein the conveyor belt 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.
11. The method according to claim 7, wherein the hollow cylindrical screen stencil and the ink removal cylinder rotate in opposite directions.
Description
(1) In the following, the invention is explained in detail with reference to drawings. The drawings are a purely schematic depiction and are not true to scale. They in no way restrict the invention.
(2) They depict:
(3) FIG. 1 a cross-section of a screen printing device according to the prior art,
(4) FIG. 2 a cross-section of the screen printing device according to the invention,
(5) FIG. 3 a cross-section of the screen of the rotating hollow cylindrical screen stencil, and
(6) FIG. 4 a flowchart of the method according to the invention for printing on a pane.
(7) FIG. 1 depicts a cross-section of a screen printing device (I) according to the prior art. The screen printing device for applying an ink (12) includes at least a conveyor belt (3) or even an assembly line moved in the direction (C). A hollow cylindrical screen stencil (1) rotating in the direction (A) with a circumferential screen (13) (not shown) as a printing surface is arranged together with an adjacently placed ink removal cylinder (3) rotating in the direction (B) above the conveyor belt (3) An ink supply device (8), for example, a valve connected via lines to an ink supply tank or hoses, is arranged inside the screen stencil (1). The screen stencil (1) further includes a first doctor blade (4) adjacent the conveyor belt (3) and a second doctor blade (5) adjacent the ink removal cylinder (2). The first doctor blade (4) fills the meshes of the circumferential screen (13) (not shown) with the ink (12) and presses the ink (12) onto the pane (10) or substrate to be printed and enables bonding of the ink (12) on the surface of the pane (10) by adhesion. The pane (10) preferably includes glass panes, particularly preferably glass panes of different sizes or dimensions. Excess ink or ink not used due to the geometry of the pane (10) is transferred via the second doctor blade (5) to the ink removal cylinder (2). The ink removal cylinder (2) includes an ink collection container (11). Using an ink scraper (6), the ink collection container (11) gathers the ink (12) collected by the ink removal cylinder (2). However, the structure depicted according to the prior art enables only relatively low cycle times during printing. The printing speeds achievable, in other words the running meters of glass that can be printed per minute, are in the range from 3 m to 4 m per minute.
(8) FIG. 2 depicts a cross-section of the screen printing device (II) according to the invention. The basic structure corresponds to that depicted in FIG. 1. The ink (12) is introduced via a third doctor blade (7) partially onto the circumferential screen (13) (not shown). The third doctor blade (7) thus enables a defined pre-filling of the screen (13) with ink (12). The pane (10) is positioned on the conveyor belt (3) below the rotating hollow cylindrical screen stencil (1). The ink (12) is then applied via the first doctor blade (4) through the screen (13) onto the pane (10). A supply channel (9) is arranged between the third doctor blade (7) and the second doctor blade (5). The supply channel (9) enables transporting away excess ink (12) that runs back from the screen (13) via the second doctor blade (5) and cannot be transferred to the ink removal cylinder (2). The second doctor blade (5) transfers primarily the ink (12) present in the meshes of the screen to the ink removal cylinder (2). The ink (12) situated on the webs of the screen (13) runs for the most part via the second doctor blade (5) back into the interior of the rotating hollow cylindrical screen stencil (1). Without the supply channel (9), this ink (12) would accumulate in the region of the first doctor blade (4) and would interfere there with the printing process. In the case of relatively large amounts of ink, this can result in blurring of the printed image. Instead, for the most part, the excess ink arrives via the supply channel (9) back at the third doctor blade (7) and is reintroduced from there into the screen (13). The achievable printing speeds of the device according to the invention fall within the range from at least 15 m to 20 m, preferably greater than 30 m per minute. Consequently, the device according to the invention enables an acceleration of the cycle time by a factor of 3 to 4. The significantly faster cycle time also significantly reduces the costs per printed pane (10).
(9) FIG. 3 depicts a cross-section of the screen (13) of the rotating hollow cylindrical screen stencil (1). The structure corresponds to that depicted in FIG. 2. The third doctor blade (7) enables defined pre-filling of the screen (13) with ink (12) and the first doctor blade (4) enables application of the ink (12) through the screen (13) on the pane (10) moving in the direction (C). The supply channel (9) transports the excess ink (12) back to the third doctor blade (7) and from where it is reintroduced into the screen (13).
(10) FIG. 4 depicts a flowchart of the method according to the invention for printing on a pane (10). In a first step, a pane (10) is arranged on a conveyor belt (3) or assembly-line. Inside the hollow cylindrical screen stencil (1), ink (12) is filled continuously or as needed via an ink supply device (8). The ink (12) is partially introduced onto the circumferential screen (13) via a third doctor blade (7). The pane (10) is positioned on the conveyor belt (3) below the rotating hollow cylindrical screen stencil (1). The ink (12) is applied on the pane (10) via the first doctor blade (4) through the screen (13). The pre-filling/filling of the screen (13) with ink (12) occurring in the preceding step via the third doctor blade (7) reduces the amount of ink present in the region of the first doctor blade (4). These amounts of ink often result in clumping or even smearing on the pane (10) to be printed. In the next step, the pane (10) leaves the hollow cylindrical screen stencil (1) on the conveyor belt (3). 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).
LIST OF REFERENCE CHARACTERS
(11) (A), (B) and (C) running direction (I) screen printing device according to the prior art (II) screen printing device according to the invention (1) rotating hollow cylindrical screen stencil (2) ink removal cylinder (3) conveyor belt (4) first doctor blade (5) second doctor blade (6) ink scraper (7) third doctor blade (8) ink supply device (9) supply channel (10) pane (11) ink collection container (12) ink (13) screen
