Method for printing paper and digital printing device

Abstract

The invention relates to a method for printing paper (10) by means of a digital printing device having a plurality of paint application tools (6) for applying printing inks of different colors onto the paper (10), in which method the paper (10) to be printed passes through the paint application tools (6) in a feed direction, wherein the digital printing apparatus has a device (4, 18) configured and adapted to prevent or reduce the formation of condensation on the paint application tool (6), and by means of the device (4, 18), the formation of condensation on the paint application tool (6) is prevented or reduced, and wherein the device (4, 18) has a temperature controller and an electrical controller, wherein the temperature controller is arranged to influence the temperature of the paint application tool (6) and the electrical controller is arranged to control the temperature controller such that the paint application tool (6) has different temperatures wherein the temperature of the paint application tool (6) increases in a feed direction (16), the temperatures of two adjacent coating application tools (6) differ from each other by at least 0.5 DEG C, at most 1.5 DEG C, and the temperature between the first coating application tool (6) in the feed direction (16) and the last coating application tool (6) in the feed direction (16) differs by at most 10 DEG C.

Description

Technical Field

[0001] The invention relates to a method for printing paper by means of a digital printing device, the digital printing device having a plurality of coating application tools for applying printing inks of different colors to the paper, wherein in the method, the paper to be printed passes the coating application tools in a feed direction, wherein the device has a temperature controller and an electrical controller, wherein the temperature controller is arranged to influence the temperature of the coating application tools, and the electrical controller is arranged to control the temperature controller so that the coating application tools have different temperatures, the characteristic being that the temperature of the coating application unit (6) increases in the feed direction (16), the temperature of two adjacent coating application tools (6) differs by at least 0.5° C. and at most 1.5° C., wherein the temperature difference between the first coating application tool (6) in the feed direction (16) and the last coating application tool (6) in the feed direction (16) is at most 10° C. The invention also relates to a digital printing device, which is arranged and suitable for printing paper by means of the method. Background Art

[0002] Printed papers have been known in the prior art for many years. Printed papers have different uses. In the form of decorative papers, i.e. papers printed with decorative patterns, they can be used, for example, to produce laminates, for example for producing floor or wall and ceiling coverings, but also as furniture panels. The desired decoration, such as real wood decoration, is printed on a paper web or paper. This is then, for example, pressed onto a core material, preferably a wood-based panel.

[0003] Digital printing devices for printing paper have also long been known. So-called single-pass digital printing devices are used, for example, in the packaging industry to print packaging materials such as cartons, wherein the paper to be printed only passes through the printing device once. In this case, however, the requirements placed on the print and quality of the decoration produced thereby are significantly lower than, for example, in the case of producing decorative paper for the above-mentioned purposes. This applies both to the quality of the individual prints of the decoration and to the reproducibility of the decoration, which is usually required for large production runs. Furthermore, decorative papers with the same decoration are usually produced in batches at relatively large time intervals, which places higher demands on reproducibility.

[0004] It is known from the prior art that various parameters influence the quality of the decoration produced. This relates, for example, to the paper used, the amount and type of printing ink applied, the amount and type of any primer (also called undercoat) used, as well as environmental influences such as humidity and temperature. These parameters cannot usually be optimized independently of one another, but influence each other and have an impact not only on the paper to be printed, but also on the digital printing device used for printing. For example, it is known that condensation may form on the print head. This can affect the quality of the printing result. Condensation on the print head can get mixed in and clog individual nozzles on the print head through which the ink is discharged. This can lead to malfunctions of the entire print head. In order to prevent this, more intensive cleaning is required to remove the condensation that forms. In addition, such cleaning leads to the need and consumption of cleaning fluids for cleaning, thus increasing production costs. Printing ink is also consumed during the cleaning process, which can also have a negative effect.

[0005] If condensation is not detected and removed promptly, it may result in scrapped products, which can increase production costs and the cost of necessary materials, leading to longer downtime of printing equipment and increased maintenance and repair costs. Summary of the invention

[0006] Therefore, the object of the present invention is to propose a method for better achieving safe and continuous production.

[0007] The object is achieved by a method of printing paper by a digital printing device according to the present invention, wherein the digital printing device has a plurality of coating application tools for applying printing inks of different colors to the paper, wherein in the method, the paper to be printed passes through the coating application tool along a feed direction, wherein the device has a temperature controller and an electrical controller, wherein the temperature controller is configured to influence the temperature of the coating application tool, and the electrical controller is configured to control the temperature controller so that the coating application tool has a different temperature, wherein the digital printing device has a device, which is configured and suitable for preventing or reducing the formation of condensation on the coating application tool, and the formation of condensation on the coating application tool is prevented or reduced by the device, and the method is unique in that the temperature of the coating application tool increases in the feed direction, and the temperature difference between two adjacent coating application tools is at least 0.5°C and at most 1.5°C, wherein the temperature difference between the first coating application tool in the feed direction and the last coating application tool in the feed direction is at most 10°C.

[0008] Therefore, the paper to be printed passes over various coating application tools in the digital printing device. The printing ink applied by the corresponding coating application tool is applied to the paper. After the paper has passed through all existing coating application tools, the paper is thus printed with the desired decoration.

[0009] Instead of having to remove the condensation produced in the prior art and / or maintain, clean or repair the printing device, the invention solves the problem by reducing or completely preventing the formation of condensation. According to the invention, a device is provided for this purpose, which is preferably part of a digital printing device and is configured and suitable for preventing or reducing the formation of condensation. In the method of the invention, it also takes on this task. This means in particular that less condensation is produced in a digital printing device with the device than in a digital printing device without the device. This is especially true if the same parameters are used.

[0010] According to the invention, the device has a temperature controller and an electrical controller. The temperature controller is arranged to influence the temperature of the paint application tool. This can occur in different directions. The temperature controller preferably comprises a heater, which is configured to increase the temperature of the paint application tool. Particularly preferably, the heater is arranged to increase the temperature of the paint application tool independently of each other. Alternatively or additionally, the temperature controller preferably has a cooling device, which is arranged to reduce the temperature of the paint application tool. Particularly preferably, the cooling device is arranged to reduce the temperature of the paint application tool independently of each other.

[0011] The electrical controller is arranged to control the temperature controller. In a preferred embodiment, the digital printing device has at least one temperature sensor. Particularly preferably, the digital printing device has at least one temperature sensor for each paint application tool. The temperature sensor is arranged to transmit measurement data to the electrical controller, the measurement data containing information about the temperature of the corresponding paint application tool. Thus, the temperature can be measured. The electrical controller is preferably arranged to access an electronic data storage device in which a target temperature value of the corresponding paint application tool is stored. The electrical controller is or preferably includes an electronic data processing device. The electrical controller compares the temperature of the paint application tool measured by the sensor with the target temperature stored in the electronic data storage device, and is arranged to control the temperature controller based on the comparison result. If the measured temperature deviates from the target temperature by more than a predetermined value, the electrical controller sends a control signal to the temperature controller, and then the temperature controller changes the temperature of the paint application tool. If the measured temperature is greater than the stored target temperature, the cooler of the temperature controller is controlled by the control signal and reduces the temperature. If the measured temperature is lower than the stored target temperature, the heater of the temperature controller is controlled by the control signal.

[0012] According to the invention, the electrical controller is arranged to control the temperature controller so that the coating application tool has different temperatures. Particularly preferably, the temperature of the coating application tool increases in the feed direction. This design is based on the recognition that the amount of liquid printing ink applied to the paper increases in the feed direction. This also increases the risk of condensation of the applied amount of liquid. The higher the temperature of the coating application tool, the lower the probability that liquid located in the vicinity of the coating application tool will condense on the coating application tool. Therefore, it is generally advantageous if the temperature of the coating application tool increases in the feed direction.

[0013] The temperatures of two adjacent coating application tools differ by at least 0.5° C., preferably at least 0.7° C., particularly preferably at least 1.0° C. The temperatures of two adjacent coating application tools differ by at most 1.5° C., preferably at most 1.3° C., particularly preferably at most 1.0° C.

[0014] In a specific embodiment, for example, the digital printing system has four coating application tools, whose temperatures increase in the feeding direction. In this specific embodiment, the temperature of the first coating application tool is 29°C, the temperature of the second coating application tool is 30°C, the temperature of the third printing tool is 31°C, and the temperature of the fourth printing tool is 32°C.

[0015] On the one hand, it is advantageous if the temperature between the paper to be printed and the print head is as low as possible in order to reduce the risk of condensation formation. Since the paper is also heated when passing through the digital printing device, it is advantageous if the temperature of the coating application tool also increases in the feed direction. On the other hand, the amount of printing ink applied by the respective coating application tool increases with the temperature of the coating application tool. It is therefore advantageous to limit the overall temperature difference between the first and the last coating application tool. The temperature difference between the first coating application tool in the feed direction and the last coating application tool in the feed direction is at most 10° C., preferably at most 7° C., particularly preferably at most 5° C.

[0016] In a preferred embodiment, the device has at least one air flow deflector, which is arranged between two coating application tools and is configured and suitable for deflecting the air flow from the coating application tool to the adjacent coating application tool. Therefore, in the absence of an air flow deflector, the air flow flows from one coating application tool to the adjacent coating application tool and is subsequently deflected by the air flow deflector. The air flow deflector can be designed in the form of a wall or a plate, for example, which is placed or positioned in the path of the actual air flow. This is particularly advantageous in order to prevent the printing ink spray generated when the printing ink is ejected from the coating application tool from being guided or blown by an air flow from one coating application tool to an adjacent coating application tool, the air flow may, for example, come from a moving part of a digital printing device, from a paper moved by the digital printing device and / or from an air flow in the environment (Halle) in which the method is performed. This also reduces the amount of liquid in the adjacent coating application tool position, which also reduces the risk of condensation.

[0017] Particularly preferably, the device has at least one air flow deflector between each two adjacent paint application tools. This means that whenever two paint application tools are arranged adjacent to each other, at least one air flow deflector is located between the two paint application tools.

[0018] Preferably, the device has at least one air extractor, which is arranged between two adjacent paint application tools and is suitable and configured to suck the air between the two paint application tools. Particularly preferably, the device comprises at least one air extractor between each two adjacent paint application tools. This means that whenever two paint application units are arranged adjacent to each other, at least one air extraction device is located between the two paint application tools. The air extractor sucks the ink spray generated when the printing ink is ejected from the paint application tools. The air extractor is preferably part of a cooler of a temperature controller.

[0019] Advantageously, the device has a housing surrounding the coating application tool. Thus, moisture, spray and other factors that accelerate or contribute to the formation of condensation can be kept away from the print head of the coating application tool.

[0020] In a preferred embodiment, the digital printing device has a monitoring unit configured to detect condensation formation of at least one coating application tool.

[0021] The invention also achieves the stated object by a digital printing device of the type described herein, which is arranged and adapted to print paper using the method described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] An embodiment of the present invention is explained in more detail below with the aid of the accompanying drawings. In the drawings:

[0023] Figure 1 A schematic diagram of a digital printing device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] Figure 1 A digital printing device is shown, which has a printing unit 2 surrounded by a housing 4. The printing unit has four coating application tools 6, each of which can apply a color of printing ink. Optionally, additional coating application tools 6 are possible. The coating application tools 6 apply the printing ink to the printing cylinder 8. In the embodiment shown, the paper 10 to be printed is introduced into the housing 4 from the right through an opening not shown and is guided by a first tensioning roller 12, the printing cylinder 8 and a second tensioning roller 14. The printing cylinder 8 is therefore not used to transfer the printing ink to the paper 10, but to guide the paper 10 past the coating application tools 6. The feed direction is indicated by an arrow 16, which indicates the direction of rotation of the printing cylinder 8.

[0025] In the housing 4 of the printing unit 2, between each two adjacent coating application tools, a device 18 is arranged, which is configured to reduce or completely prevent the formation of condensation at the coating application tools 6. In the embodiment shown, the device 18 is an air aspirator and air flow deflector, which are only shown schematically. The housing 4 also ensures that the formation of condensation at the coating application tools 6 is low and is therefore also part of the device 18.

[0026] Reference numerals list

[0027] 2 printing units

[0028] 4 Shell

[0029] 6Paint application tools

[0030] 8 Printing Cylinders

[0031] 10. Paper

[0032] 12 The first tension roll

[0033] 14 Second tension roller

[0034] 16 Arrows

[0035] 18 devices.

Claims

1. A method for printing a paper (16) by means of a digital printing device, the digital printing device having a plurality of coating application tools (6) for applying printing inks of different colors on the paper (10), wherein in the method, the paper (10) to be printed passes the coating application tools (6) in a feeding direction, wherein the digital printing device has a device (4, 18) configured and suitable for preventing or reducing the formation of condensation on the coating application tools (6), and the formation of condensation on the coating application tools (6) is prevented or reduced by the device (4, 18), wherein the device (4, 18) has a temperature controller and an electrical controller, wherein the temperature controller is configured to influence the temperature of the coating application tools (6), and the electrical controller is configured to control the temperature controller so that the coating application tools (6) have different temperatures, characterized in that The temperature of the coating application tool (6) increases in the feed direction (16), and the temperatures of two adjacent coating application tools (6) differ from each other by at least 0.5°C and at most 1.5°C, wherein the temperature difference between the first coating application tool (6) in the feed direction (16) and the last coating application tool (6) in the feed direction (16) is at most 10°C.

2. The method according to claim 1, characterized in that The temperatures of two adjacent coating application tools ( 6 ) differ by at least 0.7° C., particularly preferably by at least 1.0° C., and by at most 1.3° C., particularly preferably by at most 1.0° C.

3. The method according to claim 1 or 2, characterized in that: The temperature of the first coating application tool (6) in the feed direction (16) and the last coating application tool (6) in the feed direction (16) differs by at most 7°C, in particular at most 5°C.

4. The method according to any one of the preceding claims, characterized in that The device (18) has at least one air flow deflector which is arranged between two paint application tools (6) and is designed and suitable for deflecting the air flow from the paint application tool (6) to the adjacent paint application tool (6).

5. The method according to claim 4, characterized in that The device (18) has at least one air flow deflector between every two adjacent paint application tools (6).

6. The method according to any one of the preceding claims, characterized in that The device (18) has at least one air extractor, which is arranged between two paint application tools (6) and is designed and suitable for sucking air between the two paint application tools (6).

7. The method according to claim 6, characterized in that The device (18) has at least one air extractor between every two adjacent paint application tools (6).

8. The method according to any one of the preceding claims, characterized in that The device (4) has a housing (4) surrounding the paint application tool (6).

9. The method according to any one of the preceding claims, characterized in that The digital printing device has a monitoring unit which is arranged to detect the formation of condensation on at least one coating application tool (6).

10. A digital printing device adapted and arranged to print a sheet (10) by a method according to any one of the preceding claims.

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