Cleaning method for cleaning nozzle surface of ink print head assembly

Abstract

SOLUTION: To provide a method in which a cleaning carriage (23) performs motion (70) along an assembly (11) and cleans a nozzle surface (13), the cleaning carriage (23) has an ultrasonic cleaning device (30), a suck-out apparatus (40), and a flushing device (50), the motion (70) of the cleaning carriage is performed on an approach path (71) and a return path (72), on the approach path, the ultrasonic cleaning device and the suck-out apparatus are operated and the flushing device subsequent to the ultrasonic cleaning device and the suck-out apparatus is not operated, and on the return path, the flushing device and the suck-out apparatus are operated and the ultrasonic cleaning device subsequent to the suck-out apparatus and the ultrasonic cleaning device is not operated.EFFECT: This method can prevent entry of cleaning liquid together with impurities into an interior of a print head or an ink supply system of the print head.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for cleaning a nozzle face of an ink printhead assembly having the features of the preamble of claim 1.

[0002] Technical Field The technical field of the invention is that of the graphic industry, in particular that of industrial, i.e. highly productive and high-quality, ink printing (inkjet) on flat substrates, i.e. the image-wise application of extremely fine droplets of liquid ink to a sheet-, web-, film- or label-like substrate, preferably made of paper, cardboard, paperboard, plastic, metal or composite material. In particular, the invention is in the sub-scope of cleaning print heads or sensitive nozzle faces.

[0003] Background technology DE 102020105736 A1 discloses ultrasonic inkjet printhead cleaning, where ultrasonically vibrated cleaning fluid is brought from a cleaning tray to the nozzle face of the printhead of a print bar, flows through a gap between the cleaning tray and the printhead and is collected in a collection tray. Relative motion can then be created by movement of the printhead along the cleaning tray. Furthermore, "purging" can be performed during cleaning, i.e. cleaning fluid can be sprayed in and out.

[0004] In this case, there is a risk that the cleaning liquid may reach the inside of the print head carrying impurities therewith.

[0005] Technical issues SUMMARY OF THE DISCLOSURE The object of the present invention is therefore to provide an improvement over the prior art, in particular by which it is possible to prevent the cleaning liquid from entering the interior of a print head or into the ink supply system of a print head together with impurities.

[0006] In particular, cleaning fluid should be prevented from getting into the nozzles and contaminating the ink there, since this could lead to problems in which the ink thus contaminated does not cure or cures incorrectly and the ink has to be replaced.

[0007] Solution of the problem by the invention This problem is solved according to the invention by the method according to claim 1.

[0008] Further advantageous and therefore preferred configurations of the invention emerge from the dependent claims as well as the description and the drawings.

[0009] A cleaning method according to the present invention for cleaning a nozzle face of an ink print head assembly, in which a cleaning carriage moves along the assembly and cleans the nozzle face with ultrasonically vibrated cleaning liquid, is characterized in that the cleaning carriage has an ultrasonic cleaning device, a suction device and a flushing device, and the movement of the cleaning carriage is made in an outward and return path, in which the ultrasonic cleaning device and the suction device following the ultrasonic cleaning device are operated in the outward path, and the flushing device following the ultrasonic cleaning device and the suction device are not operated, and in the return path, the flushing device and the suction device following the flushing device are operated, and the ultrasonic cleaning device following the flushing device and the suction device are not operated.

[0010] Advantageous Configurations and Functions of the Invention The methods according to the invention advantageously make it possible to prevent the cleaning liquid from entering the interior of the printhead or into the ink supply system of the printhead together with impurities.

[0011] The inventive suction of the cleaning liquid of the ultrasonic cleaning device prevents this liquid, and possibly entrained impurities, from passing from the nozzle opening to the print head and from there to the ink supply system and being dispersed there. The suction is therefore preferably carried out immediately after the ultrasonic cleaning, i.e. at a very short spatial and therefore time interval. The spatial interval (between the adjacent walls of the ultrasonic cleaning device and the suction device or between the respective centers of both devices) is preferably a few millimeters to a few centimeters, for example less than 5 cm, or less than 3 cm, or less than 1 cm. The same applies to the cooperation of the suction device and, if provided, a flushing device and the interval between them.

[0012] An "assembly of ink print heads" may also be called a print bar. The print bar preferably extends laterally over the entire width of the substrate to be printed. In the case of multi-color printing, several print bars may be provided one behind the other in the transport direction of the substrate. The print bar with the print heads is preferably arranged laterally stationary in the ink printing machine. The relative movement for cleaning is preferably effected by a lateral movement of a cleaning carriage.

[0013] Further configurations of the invention In the following, preferred further configurations (for short, further configurations) of the present invention as a method are described.

[0014] A further configuration may be characterized in that the activated ultrasonic cleaning device releases the cleaning liquid, in particular upwards. A further configuration may be characterized in that the release of the cleaning liquid is from a chamber that is open towards the ink print head. A further configuration may be characterized in that the release of the cleaning liquid is from the chamber as a surge bath. A further configuration may be characterized in that the release is via a leading wall of the chamber in the outward path and via another wall that is following in the outward path, as the surge bath as an overflow. An overflow via a side wall may also be provided. A further configuration may be characterized in that the cleaning liquid overflowing in the surge bath is collected and drained / discarded or fed back to the chamber. A pump may be used for the supply. A further configuration may be characterized in that the collection is in a collection channel that extends to the wall and adjacent to the other wall, preferably open upwards. A further configuration may be characterized in that an ultrasonic source that can be turned on and off, located facing or within the chamber, ultrasonically vibrates the cleaning liquid. Preferably, the ultrasonic source is provided at the bottom surface of the chamber.

[0015] A further arrangement may be characterized in that the activated flushing device ejects flushing liquid, preferably upwards. A further arrangement may be characterized in that the ejection of flushing liquid occurs from a separate chamber - different from the chamber - that opens towards the ink print head. The separate chamber may be provided as an open passage. The separate chamber is preferably smaller than the chamber (in terms of the liquid volume contained therein). The chamber and the separate chamber preferably extend laterally / transversely across the print head assembly or at least transversely across a section of the nozzle face that has to be cleaned.

[0016] A further configuration may be characterized in that the cleaning liquid and the flushing liquid are identical to each other. Both liquids may preferably be supplied from the same reservoir, i.e. only one type of liquid may be used. For this purpose, one or two pumps may be provided.

[0017] A further configuration may be characterized in that, on the forward path, the suction device sucks air, thereby sucking both the cleaning liquid and the impurities out of the nozzle face. A further configuration may be characterized in that, on the return path, the suction device sucks air and / or the flushing liquid of the flushing device, thereby sucking both the cleaning liquid and the impurities out of the nozzle face. A further configuration may be characterized in that the suction is performed through a suction passage of the suction device formed in the cleaning carriage with a suction opening opening towards the ink print head. This passage is preferably at least as long as the chamber and the further chamber, transversely to the assembly of the print head. A further configuration may be characterized in that the sucked out cleaning liquid and / or flushing liquid is guided to a liquid separator. A further configuration may be characterized in that the sucked out cleaning liquid and / or flushing liquid is fed back to the ultrasonic cleaning device or the flushing device via a return passage. One further configuration may be characterized in that the aspirated cleaning or flushing liquid is guided to a waste container.

[0018] A further configuration may be characterized by providing an adapter for the ultrasonic cleaning device before the first ink print head of the assembly, moving the ultrasonic cleaning device toward the adapter where it is filled with cleaning fluid, preferably completely filled. A further configuration may be characterized by providing another adapter for the ultrasonic cleaning device after the last ink print head of the assembly, moving the ultrasonic cleaning device toward the other adapter where it is emptied of cleaning fluid, preferably completely emptied. The adapter may preferably be provided as a matching cover for the ultrasonic cleaning device or its chamber.

[0019] A further configuration may be characterized in that the cleaning carriage is provided in a horizontally movable cleaning drawer. A further configuration may be characterized in that the cleaning carriage is moved together with the cleaning drawer, preferably from a parked position of the drawer. A further configuration may be characterized in that the cleaning drawer is moved horizontally below the ink print head assembly. A further configuration may be characterized in that a roller platform provided for transporting the substrate is lowered. A further configuration may be characterized in that the cleaning drawer is moved into the space created by the lowering.

[0020] A further configuration may be characterized in that the cleaning carriage is provided as part of a cleaning box with a tray, which is provided in a cleaning drawer. A further configuration may be characterized in that the ink print head ejects ink into the tray of the cleaning box when the cleaning carriage stops between the forward and backward passes (English "purgen"). A further configuration may be characterized in that the cleaning drawer is provided with several cleaning boxes with a tray each and a cleaning carriage each movable relative to and along the boxes. In this case, preferably all cleaning carriages are moved together. A further configuration may be characterized in that a corresponding number of cleaning boxes are provided for simultaneously cleaning several assemblies of the ink print head. For example, four (for CMYK), seven (for CMYK+OGV), eight (for CMYK+OGV+white) cleaning boxes may be provided for a corresponding number of inks in multi-color printing.

[0021] A further configuration may be characterized in that the cleaning carriage is supported resiliently against the cleaning box. This allows the cleaning carriage to be applied against the print head by spring load and to slide along the print head (but in this case without contacting the nozzle face). In this case, a spacing accuracy of ±0.02 mm can be maintained. During cleaning and flushing, the carriage preferably travels at a speed of 20 to 80 mm / s on the outward or return path. A further configuration may be characterized in that in this case, a predetermined spacing is maintained between the ultrasonic cleaning device, the suction device, and the flushing device on the one hand and the nozzle face on the other hand. This makes it possible to avoid damage to the delicate nozzle face.

[0022] A further arrangement may be characterized in that the cleaning drawer is driven by a motor.A further arrangement may be characterized in that the cleaning drawer is provided for driving by a motor.

[0023] A further configuration may be characterized in that the cleaning method is implemented in an ink printing machine. A further configuration may be characterized in that in this case one assembly of ink print heads is cleaned by one cleaning box. A further configuration may be characterized in that in this case several parallel assemblies of ink print heads are cleaned by several cleaning carriages movable in parallel. A further configuration may be characterized in that several cleaning carriages are moved together.

[0024] A further configuration can be characterized in that a cleaning drawer with several cleaning boxes is moved horizontally by a motor from a transverse stop position - relative to the transport direction of the printed material - to a cleaning position, in which several cleaning carriages together, correspondingly along a large number of printing bars, are moved horizontally in an outward direction for cleaning and in a return direction for flushing, with the ultrasonic source being activated during cleaning and the cleaning drawer finally being moved again to its stop position.

[0025] The features and combinations of features disclosed in the above Technical Field, Invention and Further Features paragraphs and the following Example paragraph - in any combination with one another - form further advantageous features of the present invention. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 illustrates a preferred embodiment of the present invention and further configurations. [Diagram 2] FIG. 1 illustrates a preferred embodiment of the present invention and further configurations. [Diagram 3]FIG. 1 illustrates a preferred embodiment of the present invention and further configurations.

[0027] Examples and drawings of the invention Figures 1 to 3 show a preferred embodiment of the invention and further configurations. Corresponding features are given the same reference numerals in the figures. Figures 1 to 3 show an apparatus for carrying out a preferred embodiment of the cleaning method according to the invention.

[0028] An ink printing machine 10 for industrial, i.e. high-productivity and high-quality inkjet printing, preferably for printing on web-like substrates, e.g. made of paper or label material, has at least one assembly 11 (or so-called printing bar, or "printbar") of a plurality of ink print heads 12, preferably arranged in a row, oriented downwards and immobile during printing, oriented transversely to the substrate or its transport direction. Each print head 12 has a nozzle face 13 with a plurality of nozzles 14 for the controlled - depending on the image information to be printed - ejection of ink 15 in the form of very fine individual droplets. This nozzle face is very delicate and must therefore be carefully cleaned of possible impurities 16, e.g. hardened ink 15 and / or (e.g. paper) dust.

[0029] The device comprises a number of elongated cleaning boxes 21, preferably arranged parallel to one another and preferably both horizontally movable parallel to the printbar (relative to the longitudinal extension of the printbar). All boxes 21 may be arranged in a preferably horizontally movable cleaning drawer 20 and can be moved together with the cleaning drawer in a forward direction 71 and a backward direction 72. By way of example, in Figures 1 and 2 only one box 21 is shown from the side in cross section, and in Figure 3 two boxes are shown.

[0030] The drawer 20 can be moved back and forth between a cleaning position and a rest position in the above-mentioned lateral direction, preferably by a motor. During printing, the drawer is pulled back to the rest position and the nozzle surface is freely located above the substrate being transported underneath. The cleaning box 21 comprises an upwardly open tray 22 for the so-called purging of the print head 12 and a cleaning carriage 23 which can be moved back and forth with an upwardly cleaning action for cleaning and flushing the nozzle surface 13 and / or the nozzles 14. In FIG. 1, the carriage 23 is shown in a cleaning position 24, i.e. it is located at a small distance below the nozzle surface 13. The cleaning carriage can be moved back and forth along the nozzle surface (when the drawer 20 is in its cleaning position). This movement can be performed by a motor drive, for example by a motor with a belt drive, not shown. The forward movement (preferably towards the working side BS of the machine) serves for cleaning, while the return or return movement (preferably towards the drive side AS of the machine) serves for flushing after cleaning. The cleaning carriage is preferably positioned at a small distance 25 relative to the nozzle face and is movable. The gap between the carriage and the nozzle face created by this distance avoids direct contact between the two and thus possible damage to the nozzle face. Furthermore, this gap is used for containing liquid for cleaning and / or flushing.

[0031] The cleaning carriage 23 includes three devices: an ultrasonic cleaning device 30, a suction device 40 and a flushing device 50. These devices may be arranged in one common block of the carriage. The device 30 works with a cleaning liquid 60 and the device 50 works with a flushing liquid 61.

[0032] FIG. 2 shows the same device as in FIG. 1, but in less detail. It can be seen, however, that the illustrated printbar 11 has an adapter 17 and another adapter 18 at the beginning and end of the row of printheads 12. Both adapters have their respective adapter faces which lie in a plane with the nozzle face 13. The adapters can be formed as aluminum blocks. This allows the adapters to be used for processes which may stress, contaminate or damage the printheads. The adapter 17 or its adapter face is used, for example, to close the device 30 when filling with cleaning fluid, while in this case a gap remains between the adapter 17 and the device 30 (as between the printhead 12 and the device 30). In contrast, the other adapter 18 or its adapter face is used, for example, to control the device 40 or the negative pressure of the device 40 which is required for suction. Filling and draining therefore preferably does not take place adjacent to the printheads 12, but in the adapters. After filling, the ultrasonic source and suction are activated (see below) and the cleaning carriage 23 preferably runs once under and along the nozzle face (cleaning run; outward run). Optionally, a purge is then performed, i.e. the print head ejects ink into the tray 22 in order to push any cleaning residues that have entered the print head out of the print head. At the end, a flushing run (return run) is performed supplying flushing liquid in order to clear the print head or its nozzle face of any ink residues (see also below). Of course, the cleaning run and the flushing run may be performed in different directions, in which case only cleaning is performed first and then flushing is performed.

[0033] In Figures 2 and 3, the side wall 19 of the printing press 10 can also be seen (the drive side AS of the machine). That is, the drawer 20 is preferably reciprocated through an opening 19a provided in the side wall (or a part of the drawer, for example a laterally extending support, moves through a corresponding opening 19a). The stop position is preferably located behind the side wall (and the transport path for the print head and the substrate is located in front of the side wall). The movement is preferably effected by a motor 26, which drives the drawer.

[0034] In FIG. 1, an operable ultrasonic source 31 is shown at the bottom of a chamber 32 for the cleaning liquid 60 to be discharged. The device 30 forms a surge bath 33 with a respective overflow 34 via a leading wall 35 (in the forward direction) and a further trailing wall 36 (in the forward direction). The cleaning liquid is ultrasonically vibrated during cleaning or in the forward direction and contacts the nozzle face 13, thereby cleaning the same. The excess liquid 60 is returned to the liquid separator 43 via one or more collecting passages 37 and is then discarded in a waste container 45. This can be done without a pump, just by the gravity of the liquid. The supply of the cleaning liquid can take place from a reservoir tank 46 via a line. In this case, a pump can be used.

[0035] In the forward path of the cleaning movement (to the right, for example, in FIG. 1), in addition to the cleaning device 30, the subsequent suction device 40 is also activated. The device 40 has a suction channel 41 with a suction opening 42 opening upwards onto the nozzle surface 13. For example, liquid 60 discharged from the device 30, which remains attached to the nozzle surface and is therefore not returned via the collecting channel 37, is sucked out by the device 40, preferably together with air 62. The liquid thus sucked out is guided via the return channel 44 and / or the return line 44 to the liquid separator 43, from where it is guided to a waste container 45 and disposed of.

[0036] The device shown in FIG. 1 further comprises a flushing device 50, which is operated in the return path of the cleaning movement (to the left in FIG. 1, for example), and the suction device 40 following the flushing device is also operated. The device 50 releases flushing liquid 61 from a further chamber 51, preferably with a flushing slope 52, in the direction of the suction device 40, which flushing liquid is sucked out by the suction device 40, preferably together with air 62. The sucked out liquid 61 carrying the impurities is then guided via a return passage 44 to the liquid separator 43, from where it is guided to a waste container 45 and disposed of. The supply of flushing liquid can take place via a line from a reservoir tank 46. A pump can be used in this case. The flushing liquid and the cleaning liquid can preferably be the same liquid. As an alternative to the illustrated configuration of the flushing device 50 having a separate chamber 51 with a flushing slope 52, the flushing device may also have a device for spraying the flushing liquid 61, for example a spray bar with spray nozzles.

[0037] In Fig. 3 a perspective view of the printing press 10 is shown. Parts of the machine not relevant to the invention have been omitted in this case for clarity. One can see the side wall 19 with the openings 19a, the cleaning drawer 20 in the cleaning position 24, two cleaning boxes 21, each with a cleaning carriage 23, and one print bar 11, each with a print head 12. [Explanation of symbols]

[0038] 10 Ink Printing Machine 11 Assembly / Print Bar / Print Bar 12 Ink Print Head 13 Nozzle surface 14 Nozzles 15 Ink 16 Impurities 17 Adapters 18 Alternative Adapters 19 Side wall 19a aperture 20 Cleaning Drawer 21 Cleaning Box 22 Tray 23 Cleaning carriage 24 Cleaning Position 25 intervals 26 Motor 27 Belt 30 Ultrasonic cleaning device 31 Ultrasound Source 32 chamber for the cleaning liquid to be discharged 33 Surge bath 34 Overflow section 35 The preceding wall 36 Another wall follows 37 Collection passage / Collection pipe 40 Suction device 41 Suction passage 42 Suction opening 43 Liquid separator 44 Return passage / return pipe 45 Waste container 46 Reservoir tank 50 Flushing device 51 Separate chamber for flushing liquid to be discharged 52 Flushing Slope 60 Cleaning Fluid 61 Flushing Fluid 62 Air 70 Cleaning carriage movement 71 Outbound 72 Return

Claims

1. A cleaning method for cleaning the nozzle surface of an ink print head assembly, wherein a cleaning carriage (23) moves (70) along the assembly (11) and cleans the nozzle surface (13) with an ultrasonically vibrated cleaning fluid (60), The cleaning carriage (23) comprises an ultrasonic cleaning device (30), a suction device (40), and a flushing device (50), and the movement (70) of the cleaning carriage is performed in a forward path (71) and a return path (72), wherein in the forward path, the ultrasonic cleaning device and the subsequent suction device are activated in conjunction with the ultrasonic cleaning device, but the subsequent flushing device is not activated in conjunction with the ultrasonic cleaning device and the suction device, and in the return path, the flushing device and the subsequent suction device are activated in conjunction with the flushing device, but the subsequent ultrasonic cleaning device is not activated in conjunction with the flushing device and the suction device.

2. The method according to claim 1, wherein the activated ultrasonic cleaning device (30) discharges the cleaning fluid (60).

3. The method according to claim 2, wherein the cleaning fluid (60) is discharged from a chamber (32) that is opened toward the ink print head (12).

4. The method according to claim 3, wherein the cleaning liquid (60) is discharged from the chamber (32) which serves as a surge bath (33).

5. The method according to claim 1 or 2, wherein the activated flushing device (50) discharges a flushing liquid (61).

6. The method according to claim 5, wherein the flushing liquid (61) is discharged from a separate chamber (51) that is open toward the ink print head (12) and is different from the chamber (32).

7. In the forward path (71), the suction device (40) sucks in air (62), thereby sucking out both the cleaning liquid (60) and impurities (16) from the nozzle surface (13), the method according to claim 1 or 2.

8. In the return journey (72), the suction device (40) sucks up the flushing liquid (61) from the flushing device (50), thereby sucking out both the cleaning liquid (60) and impurities (16) from the nozzle surface (13), the method according to claim 1 or 2.

9. The method according to claim 1 or 2, wherein the suction is performed through a suction passage (41) formed in the cleaning carriage (23) of the suction device (40), which has a suction opening (42) that is open toward the ink print head (12).

10. The method according to claim 1 or 2, wherein an adapter (17) for the ultrasonic cleaning device (30) is prepared in front of the first ink print head (12) of the assembly (11), the ultrasonic cleaning device is moved toward the adapter, and the ultrasonic cleaning device is filled with cleaning fluid (60).

11. The method according to claim 10, wherein after the last ink print head (12) of the assembly (11), another adapter (18) for the ultrasonic cleaning device (30) is prepared, and the ultrasonic cleaning device is moved toward the other adapter, where the cleaning fluid (60) is removed from the ultrasonic cleaning device and emptied.

12. The method according to claim 1 or 2, wherein the cleaning carriage (23) is provided on a cleaning drawer (20) that is movable in the horizontal direction.

13. The method according to claim 12, wherein the cleaning carriage (23) is provided as part of the cleaning box (21), and the cleaning box is provided in the cleaning drawer (20).

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