Printing device for printing a workpiece and method

Abstract

The invention relates to a printing device (100) for printing a workpiece, to a machine comprising such a printing device and to a corresponding method. A workpiece of this type is in particular a plate-shaped workpiece which is, for example, at least partially made from wood or wood materials.

Description

Technical field

[0001] The invention relates to a printing device for printing on a workpiece, a machine with such a printing device, and a corresponding method. Such a workpiece is, in particular, a plate-shaped workpiece that consists, for example, at least partially of wood or wood-based materials. State of the art

[0002] In the furniture and building component industries, it is known to print on sheet-shaped workpieces using a printing device, in particular an inkjet printing device. In this context, for example, publication EP 1 837 189 A2 should be mentioned, which discloses a device for finishing workpieces that preferably consist at least partially of wood, wood-based materials, or the like. This device uses an inkjet printing device with a plurality of nozzles.

[0003] When using an inkjet printing system on an industrial scale, it is necessary to clean the printheads at specific intervals to ensure that all nozzle openings are fully functional and reliably available for applying the printing material. This nozzle cleaning can be performed manually, for example.

[0004] To check whether all nozzles are functioning again, a test print can be performed on a conventional printer, the result of which is scanned and subsequently evaluated. However, when an inkjet printing system is used on an industrial scale for printing on a sheet-shaped workpiece, checking by means of a test print on a workpiece has proven to be relatively uneconomical or impractical, because printing on a sheet-shaped workpiece involves significantly higher costs compared to printing on paper.

[0005] Especially when printing on the narrow edge of a flat workpiece, a test print can only be performed to a limited extent, because the printable height of the narrow edge depends on the thickness of the flat workpiece. However, the thickness of a flat workpiece can vary depending on the workpiece and the machine type, so the full functionality of a printing device can only be reliably assessed when printing on a workpiece of maximum thickness. Often, however, workpieces are printed whose thickness is less than the maximum printable area of ​​the printing device. Therefore, suitable workpieces would need to be available for a test print.

[0006] Document DE 10 2010 008 295 A1 is known, which shows a printing device for printing on the surfaces of material boards, in particular wooden boards, with a multicolored image. Description of the invention

[0007] One objective of the invention is to provide a printing device for printing on a workpiece and a corresponding method to ensure high-quality printing on a workpiece.

[0008] The subject matter of claim 1 provides a corresponding printing device. Further preferred embodiments are listed in the dependent claims. Furthermore, the invention proposes a machine with a printing device and a method, wherein a printing device according to one of the aforementioned aspects can be used in the course of the method.

[0009] The printing device is designed for printing on a workpiece, in particular a plate-shaped one (made of wood or a wood-based material), and comprises: a printing unit with at least one print head for printing on an area (for example, a narrow surface) of the workpiece, and a control unit with a recording medium, wherein the printing unit is configured to print on the recording medium or a medium held on the recording medium.

[0010] Thus, the control unit makes it possible to test the full functionality of the printing device without printing on a workpiece or preparing a workpiece for this purpose. Furthermore, the printing unit, in particular the opening(s) / nozzle(s) of the printing unit, can be tested independently of any possible workpiece dimensions, especially workpiece thickness.

[0011] The recording medium or the medium held by the recording medium can be paper, for example paper on a roll (such as a fax roll, cash register roll or similar), a film, a glass pane, a PTFE-coated material, or similar.

[0012] It is preferred that the control unit includes a detection unit configured to detect the printed section on the recording medium or on the medium held by the recording medium. This allows for the digitized monitoring of the printing quality performed by the printing unit, enabling software-based analysis. Furthermore, the results of the assessment performed by the detection unit can be used for other control or regulation processes.

[0013] According to the invention, the printing device is designed such that the printing unit has a pivot axis about which the at least one printhead can be pivoted. Thus, the at least one printhead, which in the case of an inkjet printhead has a plurality of openings for ejecting a printing substance, can be pivoted from an operating position to an inspection position or a maintenance position. It has been found in particular that orienting the printing unit such that the printhead openings for ejecting the printing medium point downwards in a vertical direction is advantageous for inspection and / or cleaning. Printing on a narrow side of a plate-shaped workpiece, on the other hand, preferably takes place with the printing unit oriented in such a way that the printhead openings for ejecting the printing medium point in a horizontal direction.

[0014] However, it is also possible that a workpiece is oriented in such a way that one narrow side forms a horizontal plane. In this case, the printing unit is arranged so that the openings of the printhead for ejecting the printing medium point vertically downwards or upwards.

[0015] The control position and the maintenance position are preferred distinct positions of the printing unit. However, it is also possible that the control position and the maintenance position are the same position of the printing unit, with the printing unit printing on the recording medium or a medium held against the recording medium in the control position, and cleaning of the printing unit taking place in the maintenance position, in which the recording medium has been removed.

[0016] It is preferred that an opening of a printhead of the printing unit, in the maintenance position, points downwards in a vertical direction. According to a further modification, however, an opening of a printhead of the printing unit, in the maintenance position, can also be oriented in an orientation inclined to the vertical direction or in a horizontal direction.

[0017] It is preferred that the printing device has a guide, in particular a linear one, along which the printing unit can be moved. Thus, the printing unit can, for example, be moved in a horizontal direction.

[0018] According to a further embodiment, the printing device includes a cleaning unit for cleaning the printing unit. In one embodiment, the cleaning unit comprises an ink collection system (e.g., a tray with a drain into a container) and / or a suction device for rinsing the opening(s) of the printing unit. The cleaning unit can be positioned to move towards the printing unit. Additionally or alternatively, the cleaning unit can include a unit for wiping the opening(s) of the printing unit.

[0019] The cleaning unit can also be designed in such a way that it covers the opening(s) of the pressure unit to protect them from light and dust when the unit is not in use.

[0020] It is preferred that the recording medium is a sheet-shaped element, and preferably that the recording medium can be unwound from a roller. Thus, the recording medium can be moved relative to the printing unit and, after the application of a printed section, guided into the area of ​​the detection unit.

[0021] Furthermore, the recording medium can be designed in a disc-like form and be movable by means of a drive, in particular a linear drive. Such a design has proven to be particularly robust.

[0022] The printing device preferably further comprises a control unit configured to release the printing unit based on the detection result of the detection unit. If the detection unit determines that further cleaning of the printing unit, in particular of one or more printheads, is required, a cleaning process can be initiated.

[0023] It is preferred that the detection unit includes a CCD sensor, a CMOS sensor, and / or a camera system. A CMOS sensor offers the advantage of comparatively high frame rates and higher image quality compared to a CCD sensor. Conversely, the CCD sensor is more cost-effective. A camera system can be connected to image processing software to perform a detailed evaluation.

[0024] It is preferred that the printing unit is set up to print a print area of ​​5mm-2000mm, preferably 8mm-110mm.

[0025] According to one embodiment, the control unit (and / or the cleaning unit) is / are movable in such a way that the printing unit can be positioned with the control unit to print on a recording medium or a medium held on the recording medium (and / or to clean the printing unit in a position).

[0026] According to another embodiment, the control unit (and / or the cleaning unit) is movable from a rest position to a working position, and vice versa. This provides a compact arrangement of the printing device.

[0027] The control unit and / or cleaning unit may be mounted on a sliding mechanism that is actuated to move the control unit (and / or cleaning unit) from its rest position to its working position, and vice versa. Actuation of the sliding mechanism can be motorized, pneumatic, or manual. In the rest position of the control unit and / or cleaning unit, a specific orientation or arrangement of the pressure unit can be achieved without risk of collision between the pressure unit and the control unit and / or cleaning unit.

[0028] In particular, the sliding mechanism is designed to be movable in a translational, preferably horizontal, direction in order to move the control unit and / or the cleaning unit from the rest position to the working position, and vice versa. This can be done similarly to the movement of a drawer.

[0029] Furthermore, a machine for processing, in particular plate-shaped, workpieces is provided, comprising a device for applying a strip-shaped coating to the workpiece and a printing device according to one of the preceding aspects.

[0030] According to another embodiment, such a machine can be a conveying device for moving the workpiece, in particular a belt conveyor. This allows the machine to process particularly large quantities.

[0031] Printing on a recording medium or a medium held on the recording medium can be done independently of the machine feed.

[0032] For example, the machine may have a control device configured to prompt the machine operator to print onto a recording medium or a medium held against the recording medium in the event of a long period of inactivity. Such printing can be started manually or carried out automatically at defined time intervals, after detecting a prolonged period of inactivity, or similar.

[0033] Furthermore, a method with the features according to claim 13 is provided.

[0034] When printing on the recording medium or the medium held on the recording medium, further information can be applied, for example a QR code, barcode or similar, which includes information such as date, time, printed meters, age of the ink, last cleaning, next maintenance, and / or wear of the printing unit (especially opening(s) / nozzle(s) of the printing unit).

[0035] As part of the process, a printing device can be used in accordance with one of the aforementioned aspects. Brief description of the drawings

[0036] Further features and advantages will become apparent from the following description of embodiments with reference to the accompanying drawings. Fig. 1 shows a schematic cross-sectional view of a printing device according to one embodiment of the invention. Fig. 2 shows a front view of a control unit according to a first embodiment. Fig. 3a shows a side view of a control unit according to a second embodiment. Fig. 3b shows a front view of the control unit according to a second embodiment. Description of embodiments

[0037] Identical reference symbols listed in different figures name identical, corresponding, or functionally similar elements.

[0038] A machine 150, comprising a printing device 100, has a housing 151 and a machine bed 152. The housing 151 is designed such that workpieces processed by the printing device 100 enter at least partially into an inner area of ​​the housing 151. Furthermore, the machine 150 includes a belt conveyor 153 (conveyor device), whereby, according to further embodiments, other conveying mechanisms may also be provided. The belt conveyor 153 comprises a circulating conveying element 153a and is provided in an edge region of the housing 151 and arranged such that a section of a workpiece moved by the belt conveyor 153 rests on the conveying element 153a.

[0039] A pressure plate 154 is provided vertically above the belt conveyor 153, enabling a plate-shaped workpiece (not shown) to be moved by the belt conveyor 153 and held in place by the pressure plate 154. In the present embodiment, the pressure plate 154 comprises a plurality of rollers; however, the pressure plate 154 could also comprise, for example, a circulating belt or similar device.

[0040] The printing device 100 comprises a printing unit 10, which, according to the embodiment, is designed as an inkjet printing device and has a plurality of printheads 10a, 10b, 10c, 10d. The printing unit 10 is in Figure 1 shown in a maintenance position (also called "service position") B2, in which the printheads 10a, 10b, 10c, 10d are arranged next to each other in a substantially horizontal direction.

[0041] In operating position B1 of the printing unit 10, the printheads 10a, 10b, 10c, and 10d are positioned horizontally next to each other, allowing for the printing of workpieces of varying thicknesses and correspondingly different dimensions of a narrow surface. To move the printing unit 10 from operating position B1 to maintenance position B2, it is pivoted about a horizontal axis. Thus, the printing unit 10 can assume both operating position B1, in which it is positioned for printing on the narrow surface of a plate-shaped workpiece, and maintenance position B2, in which it is pivoted for cleaning the printheads.

[0042] For printing on workpieces with different narrow surfaces, individual openings of the print heads 10a, 10b, 10c, 10d are controlled in such a way that those openings which are opposite the narrow surface of the moving workpiece are actuated, whereas other openings which are outside the area to be printed of the respective narrow surface remain closed.

[0043] The printing unit 100 further comprises a cleaning unit 20, which is located in a vertical direction below the printing unit 10, and which is dimensioned such that the printheads of the printing unit 10 can be cleaned in the maintenance position B2.

[0044] According to the preferred embodiment, the cleaning unit 20 comprises a vertically movable tray (ink collection system) that can be moved towards the printing unit 10 for cleaning the printheads. This allows the cleaning unit to cover the openings to protect them from light and dust when the unit is stationary. Once the cleaning unit 20 has been positioned towards the printing unit 10, the printheads can be cleaned, in particular rinsed.

[0045] In addition to or as an alternative to the aforementioned tub, the cleaning unit may include a suction device and / or a unit for wiping the opening(s) of the pressure unit.

[0046] The pressure unit 10 is movable along a guide 15, the guide 15 extending in a substantially horizontal direction transverse to the conveying direction of the workpieces.

[0047] Adjacent to the cleaning unit 20 is a control unit 30, with which a test print can be performed and checked accordingly. To move the printing unit 10 into the area of ​​the control unit 30 (control position B3), the printing unit 10 is moved along the guide 15 and positioned in the area of ​​the control unit 30. The printheads 10a, 10b, 10c, 10d of the printing unit 10 are arranged next to each other in a substantially horizontal direction in control position B3, as in the maintenance position B2.

[0048] In addition to the previously mentioned positions of the printing unit (operating position B1, maintenance position B2, inspection position B3), the printing unit 10 can be pivoted such that the printheads 10a, 10b, 10c, 10d of the printing unit 10 point in a different direction than in operating position B1. This arrangement of the printing unit 10 is referred to as inspection position B4. In inspection position B4, the printing unit 10 can be visually inspected. For this purpose, the housing 101 of the printing device 100 has a (in Fig. 1 (Window not shown) opens so that an operator of the printing device 100 can view the printing unit 10 accordingly. Alternatively or additionally, a camera can be provided in the housing 101 with which the printing unit 10 can be recorded and viewed by an operator, for example, at an operating panel of the printing device 100.

[0049] In Fig. 2Figure 1 is a schematic detail representation of the control unit 30 described above. The control unit 30 comprises a detection unit 31 and a recording medium 32. According to the embodiment, the recording medium 32 can be unwound from a first roller 33 and received by a second roller 34. A support section 35 extends between the first roller 33 and the second roller 34, on which the recording medium 32 rests. The detection unit 31 comprises, in particular, a CCD sensor or a CMOS sensor. Furthermore, the detection unit 31 can be configured as a camera system. The evaluation of the information recorded by the detection unit 31 can be carried out using a computer program.

[0050] The control unit 30 is configured such that the printheads 10a, 10b, 10c, 10d of the printing unit 10 perform a test print on the recording medium 32 (or a recording medium held by the recording medium 32), and subsequently the recording medium 32 can be detected by the detection unit 31. By moving the first roller 33 and the second roller 34, the recording medium 32 is guided from an area below the printheads 10a, 10b, 10c, 10d of the printing unit 10 along a detection area of ​​the detection unit 31, so that the printed recording medium 32 enters the area of ​​the detection unit 31.

[0051] When printing on the recording medium or the medium held on the recording medium, further information can be applied, for example a QR code, a barcode or similar, such as date, time, printed linear meters, age of the ink, last cleaning and / or next maintenance, wear of the printing unit (especially opening(s) / nozzle(s) of the printing unit).

[0052] In Fig. 3a / 3b A modification of a control unit 30' is shown. As in the previously described embodiment, the control unit 30' comprises a detection unit 31', which, similar to the first embodiment, may include a CCD sensor, a CMOS sensor and / or a camera system.

[0053] Furthermore, the control unit 30' comprises a plate-shaped recording carrier 32' and a linear drive 33' with which the recording carrier 32' can be moved. A recording medium 32a' can be arranged on the recording carrier 32', or the recording carrier 32' itself can serve as the recording medium. The recording carrier 32' can be moved along the printheads by the linear drive 33'. In this way, the nozzle availability can be checked in a position provided in a vertical direction below the printheads.

[0054] Even if, according to the embodiments described above, the cleaning unit and the control unit are arranged adjacent to each other, a modification may provide that the cleaning unit and / or the control unit is / are moved in such a way that the printing unit can be cleaned in a position and the control unit can be used to print on a recording medium or a medium held on the recording medium.

[0055] In particular, it may be provided that the control unit and / or the cleaning unit is / are mounted on a sliding device that is actuated to move the control unit (and / or the cleaning unit) from the rest position to the working position, and vice versa. As in Fig. 1 It is evident that the movement of such a sliding device in a horizontal direction can be carried out similarly to the movement of a drawer.

[0056] The sliding mechanism can be operated either manually or by motor. In the rest position of the control unit and / or the cleaning unit, a specific orientation or arrangement of the printing unit can be achieved without risk of collision. In particular, it is possible to align the printing unit for printing on the narrow side of a flat workpiece. If the printing unit has been pivoted for cleaning or inspection, the control unit and / or the cleaning unit can be moved towards the printing unit using the sliding mechanism.

[0057] A specific procedure according to this modification is as follows: Lowering the cleaning unit, pivoting the pressure unit so that one or more opening(s) / nozzle(s) point vertically downwards. Moving the control unit so that the control unit is positioned below the pressure unit. If necessary, snapping the control unit onto the pressure unit. Printing on a recording medium or a medium held on the recording medium.

[0058] It is evident to a person skilled in the art that individual features described in different embodiments can also be implemented in a single embodiment, provided they are not structurally incompatible. Likewise, various features described within a single embodiment can also be provided individually or in any suitable subcombination in several embodiments.

Claims

1. A printing device (100) for printing a workpiece, in particular a plate-shaped one, comprising: a printing unit (10) with at least one printing head (10a-10d) for printing on a surface, preferably a narrow surface, of the workpiece, and a checking unit (30, 30') with a record carrier (32, 32'), wherein the printing unit (10) is configured to print on the record carrier or on a medium held on the record carrier, characterised in that the printing unit (10) has a pivot axis (12) about which the at least one printing head (10a-10d) can be pivoted.

2. The printing device (100) according to claim 1, wherein the checking unit (30, 30') further has a detection unit (31, 31') which is configured to detect the section printed on the record carrier or on the medium held by the record carrier, wherein it is preferred that the printing device further comprises a control apparatus which is configured to release the printing unit, based on the detection result of the detection unit (31, 31').

3. The printing device (100) according to claim 2, wherein the detection unit (31, 31') comprises a CCD sensor, a CMOS sensor and / or a camera system.

4. The printing device (100) according to any one of claims 2-3, wherein the checking unit comprises an analysis unit that analyses the detection result of the detection unit (31, 31') by means of a computer program and / or artificial intelligence.

5. The printing device (100) according to any one of the preceding claims, wherein the printing head (10a-10d) is pivotable in such manner that openings of the printing head (10a-10d) for ejecting the printing medium point downwards in a vertical direction.

6. The printing device (100) according to any one of the preceding claims, further comprising a guide (15), in particular a linear one, along which the printing unit (10) is movable.

7. The printing device (100) according to any one of the preceding claims, further comprising a cleaning unit (20) for cleaning the printing unit (10).

8. The printing device (100) according to any one of the preceding claims, wherein the record carrier (32) is a sheet-shaped element, wherein it is preferred that the record carrier can be unwound from a roller (33).

9. The printing device (100) according to any one of claims 1-4, wherein the record carrier (32') is plate-shaped and is movable by means of a drive (33'), in particular a linear drive.

10. The printing device (100) according to any one of the preceding claims, wherein the printing unit (10) is configured to print on a printing region of 5 mm-2000 mm, preferably 8 mm-110 mm.

11. The printing device (100) according to any one of the preceding claims, wherein the checking unit (30, 30') is movable in such manner that the printing unit can be positioned with the checking unit to print on a record carrier or a medium held on the record carrier, and / or the checking unit (30, 30') is movable from a rest position to a working position, and vice versa.

12. A machine (150) for processing, in particular plate-shaped, workpieces, with a device for applying a strip-shaped coating to the workpiece and a printing device (100) according to any one of the preceding claims, wherein it is preferred that the machine (150) further comprises a conveying apparatus (153) for moving the workpiece, in particular a belt conveyor.

13. A method for printing a workpiece, in particular a plate-shaped one, comprising the steps: effecting a relative movement between a printing unit (10) and the workpiece, printing on a surface, in particular a narrow surface, of the workpiece using the printing unit (10), printing on a record carrier or on a medium held on the record carrier, characterised in that the printing unit (10) has a pivot axis (12) about which the at least one printing head (10a-10d) can be pivoted.

14. The method according to claim 13, further comprising the step of cleaning the printing unit (10) by means of a cleaning unit (20), wherein it is preferred that the printing unit (10) is pivoted from an operating position (B1) into a maintenance position for cleaning the printing unit (10), wherein it is preferred that an opening of a printing head of the printing unit (10) points downwards in a vertical direction in the maintenance position.

15. The method according to claim 13 or 14, further comprising the step: detecting a section printed on the record carrier or on the medium held by the record carrier, and / or wherein, when printing on the record carrier or on the medium held on the record carrier, further information is applied, preferably a QR code, a barcode or similar, preferably comprising information relating to the date, time, printed running meters, age of the ink, last cleaning, next maintenance, and / or wear of the printing unit.

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