APPARATUS AND METHOD FOR CONTROLLING AN INK-JET PRINTING HEAD THROUGH DETECTION OF LIGHT DIFFUSION

Description

[0001] The present invention concerns the technical field relating to the manufacture of printing systems which use ink-jet printing heads, the ink-jet printing heads being widely used in various sectors, such as office professional printing, industrial printing and, in particular, printing on ceramic. Specifically, the invention concerns the technical field regarding systems for controlling the correct operation of printing systems, in particular of nozzles of ink-jet printing heads.

[0002] The use of the ink-jet technique for decorating a variety of materials is widespread, although most applications concern printing particularly on paper. However, the numerous nozzles of the printing heads used by the ink-jet technique tend to get clogged and consequently produce results with evident defects. While a print defect has a relatively inexpensive impact if paper is printed, such a defect becomes unacceptable if it occurs in processes, like the process of decorating ceramic tiles, in which the defect becomes visible after the product has undergone other operations and the rejection of the product results in considerable economic loss.

[0003] The problem of possible partial or total clogging of the nozzles of a printing head, which can be easily experienced by anyone who uses a desktop printer, is frequent also in the industrial field and the consequence of this problem, whether the clogging is partial or total, is that the print results become unusable. This implies serious drawbacks and considerable costs, especially in the industrial field, since an imperfectly printed product must be disposed of, which results in a loss of earning. In order to highlight how much important is that the nozzles of a printing head work correctly, or are constantly controlled, it is important to remember that the industrially used machines, in all the fields mentioned above and in general, are so designed as to employ advanced automation system which are suitable for the digital printing system at issue. This means that the general production is of the serial and continuous type, so that the defective operation of the nozzles of a printing head implies a considerable economic waste for a factory. Such economic waste is due both to the loss of time required for making the system working again and to the materials deteriorates while the nozzles of a printing head are only partially working. Moreover, when industrial productions are concerned, the print area is generally inside the production line of the specific product, which inevitably leads to working in cleanliness conditions that are not always optimum, even if specific subgroups may be provided for cleaning purposes. Dusts, vapours, or the printing ink which is not perfectly ejected considerable increase the possibility of clogging of the printing head nozzles, so that this serious problem may occur more frequently in this specific operating field. Currently there is no means which makes it possible to check tin advance, an far as printing is concerned, the correct operation of the nozzles of an ink-jet printing head, so that this detect can only be highlighted "ex post" after the damage is done.

[0004] US 4510504 discloses a method for detecting a deflection amount of ink jets applied to an ink jet printer. The method comprises the steps of projecting light upon a flying ink drop, and detecting deflection amount of the ink drop on the basis of the behaviour of the light reflected by the ink drop.

[0005] EP 0596203 discloses a multiple printhead cartridge color thermal ink jet printer having apparatus for measuring the offsets between the multiple printhead cartridges, each of which comprises a nozzle array of one or more columns of nozzles, each column being parallel to the media axis of the printer.

[0006] EP 1027987 discloses an apparatus for checking a plurality of printer nozzles in a printer device. The apparatus comprises a printer head comprising a plurality of nozzles, a means for detecting at least one droplet of ink sprayed from at least one nozzle of said plurality of nozzles, and a means for performing a sequence of measurements on a first output signal of said detecting means.

[0007] US 2006/0071957 discloses the features of the preamble of independent claims 1 and 17, it concerns an apparatus and a method of visualizing droplets dispensed from an inkjet printing system. A droplet visualization system is integrated with the inkjet printing system and is capable of measuring the sizes and the speeds of dispensed inkjet droplets and capturing the trajectories of the dispensed inkjet droplets. The measured information regarding the sizes, the speeds and trajectories of the droplets is feedback to the inkjet printing system to monitor and to control the dispense operation of the inkjet printing system.

[0008] The object of this invention is to avoid these and other drawbacks, by providing a system for controlling the nozzles of a printing head which allows The working efficiency of the nozzles of the printing head to be controlled before printing and/or periodically, thereby making it possible to act before the problem occurs.

[0009] This result has been reached by adopting the technical solution according to the independent claims. Other features of the invention are set out in the dependent claims.

[0010] The advantages deriving from this invention are basically that: damages due to badly working of the nozzle can be avoided before printing, thereby safeguarding the production line from material rejects and expansive machine downtimes for restoring the initial conditions; the controlling station made for this purpose has extremely small dimensions and weight and can be used in existing machines, both in the design phase or added as an important accessory; said controlling station can employ the machine movements to bring the printing heads in a control position; the control operation can be carried out both in a phase of production start of the line and periodically, during the downtimes of the machine to which it is applied, without negatively affecting the hourly production.

[0011] These and further advantages, objects and features of the present invention will be better understood by any skilled person from the following description and with the help of the attached drawings in which some embodiments of the invention are shown by way of non-limiting example, in which: Figure 1 shows a schematic and non-limiting axonometric view of the components of the controlling station. Any kind of material, having generally a parallelepiped shape, can be used for creating a box structure or housing 1 that is substantially closed, the housing 1 having a top opening through which the ink drop/s 2 ejected by the nozzle/s of the printing head can vertically pass. Said box structure has the function of making it possible to work in a zone that is protected from light. However, the box structure could also be omitted. The laser lighting source 3 is positioned on the wall of the box structure perpendicularly to the jet 2. The laser lighting source 3 produces a horizontal light beam 4 which, if the printing head nozzles are correctly working, will surely be crossed by the ink drop/s 2. This situation is recorded by video camera 5, that is positioned on the same plane as the laser 3, but perpendicularly to the laser 3. When one or more drop/s pass/es through the lighted zone, the light signal produced by diffusion and/or reflection of the light beam 4 on the drop/s 2 crossing said light beam is detected by the video camera 5. This allows the efficiency of each single nozzle of the printing head to be controlled. If the nozzle is badly working, no ink drop/s is/are ejected, hence no light is diffused and therefore the video camera does not detect any light signal, thereby indicating the presence of a problem to the controlling system. The latter possibly interrupts production, thereby avoiding production rejects, and warns the operator of the need to replace or clean and in any case, restore the printing head nozzles to working order.

[0012] Figure 2 shows a side view of the controlling station, which view further highlights the position of the printing head 6, with the ink jet 2 crossing the light beam 4 generated by the laser 3, and the luminous effect of light diffusion which is detected by the video camera 5.

[0013] Figure 3 shows a plan view of the same system, highlighting a possible position (in this example of perpendicularity) between the video camera 5 and the laser 3, which allows optimum signalling of the presence or absence of ink drop/s 2 visible owing to the phenomenon of diffusion of light of the beam 4.

[0014] The invention relates to a system for controlling operation of the nozzles of an ink-jet or similar printing head.

[0015] The system concerned employs the physical phenomenon of light diffusion. If particles are involved, such as aerosol particles, having dimensions ranging from the same order of magnitude of the wavelength of visible light to much larger dimensions, light diffusion is due to different phenomena, such as refraction of rays incident on the surface of particles and reflection by the surface of the particles. Diffraction in particular conditions also produces diffusion. In the system, there is provided lighting the zone adjacent to the printing head nozzle, which is intended to be crossed by the drops of ink coming out of the nozzle if the latter works correctly. The impact between the light rays and the particles of the ink drops having dimensions greater than the wavelength of said rays, leads to diffusion and thus generates a ray of light which can be perceived and detected by a video camera.

[0016] The system concerned does not therefore involve lighting the ink drops to make them visible, but involves causing the ink drops to meet the light beam, so as to originate a diffusion which, in turn, creates a "light" which can be recorded by a video camera or a similar device.

[0017] The recording system, a video camera, provided in the controlling system, is connected to an electronic processor, such as a sensor, a memory device, a computer or another device, which receives the data sent by the video camera, interprets it and carries out further functions for which it is programmed.

[0018] In the system, given at least one nozzle of a printing head the operation of which is to be controlled, there is arranged:

• at least one lighting system 3 directed at lighting the zone adjacent to at least one nozzle, said zone being crossed by an ink jet 2 in correct working conditions;
• at least one recording system 5 directed at recording the zone adjacent to the at least one nozzle, said zone being crossed by an ink jet 2 in correct working conditions.

[0019] Advantageously, the lighting system 3 generates a light beam 4 which is incident on the plane which must be crossed by the jet 2. The incidence of said beam 4 in relation to the zone intended to be crossed by the jet 2 may be of any degree. The system cannot work only if the light beam 4 is parallel to the jet 2 and such as not to intersect said jet, even to the slightest extent, since in that case diffusion does not occur.

[0020] In an embodiment, which is preferred, said light beam 4 is perpendicular or almost perpendicular to the jet 2.

[0021] In an embodiment, the light beam 4 defines a horizontal plane while the jet 2, which drops downwards from the top, draws a vertical line which intersects said plane 4. This reciprocal position is preferable since the drops normally flow out of the nozzle of the printing head 6 and fall vertically.

[0022] The lighting system is advantageously realized by using light sources like LED, LASER, halogen lamp or other sources. Preferably, but without limitation, the light beam is generated by a lighting source consisting of a laser, provided with suitable optics, which generates a lamellar light beam.

[0023] The laser 3 generates a horizontal light beam 4 which makes the jet 2 visible. If there is no jet, because the printing head is clogged, nothing is visible and the recording system will record the absence of this jet. Said laser 3 is perpendicular, or in any case, incident, in relation to the direction of the jet 2.

[0024] Advantageously, the recording system 5 is positioned in such a way that the light generated by the laser does not strike the recording system 5. Said recording system must be suitable for recording the effect of the diffusion deriving from the impact between the photons and the ink particles, without receiving the direct light of the light source.

[0025] In an optimum configuration of the system, the lighting source is placed on the same axis and on the same side as the video camera, in such a way that the lighting source and the video camera are one over the other but not parallel.

[0026] In the attached figures, to facilitate the representation, said light beam 4 is shown orthogonal with respect to the recording system, but both the light beam 4 and the recording system are on the same plane.

[0027] The recording system 5 is on the same plane on which the light beam 4 is formed or, in any case, on a plane not too distant from the above mentioned plane, so that the video camera can record the effect of diffusion.

[0028] The outlet speed of the drop from the nozzle is high (8-10 m/sec) and an acquisition system based on a video camera having an extremely high acquisition speed would therefore be required. Such a video camera would therefore be much expensive. This invention uses a light source consisting of a laser, provided with suitable optics which generates a "blade" of light 4, incident on the zone through which the jet must pass and positioned in such a way as not to strike the video camera frontally. The light source thus does not strike the video camera directly and therefore a dark image is acquired in normal conditions.

[0029] Before the controlled nozzle emits the drop, the video camera is programmed so as to have an acquisition time longer than the time required by the drop to pass through the visual field of the video camera. The result is the following phenomenon: when the drop passes through the "bade" of light produced by the laser source, a flash of light is produced by diffraction. Such flash of light is detected by the video camera. Thus, by checking by means of a special software that the image acquired by the video camera has a clear dot on a dark background, it is possible to measure the actual production of the drop by the controlled nozzle. If this is not the case, it means that the nozzle has not emitted the jet and is therefore clogged.

[0030] Advantageously, in order to detect the signal generated by the passage of the ink 2 on the lighted plane 4 a video camera 5 is provided, the video camera 5 being connected to a processor suitably programmed for transmitting a signal to a controlling system of the machine, generally a PLC, if the jet 2 is detected, thereby allowing the machine to proceed. If this is not the case, the automatic process can be interrupted and the operator can be requested to act to solve the problem.

[0031] The system comprises a programmed processor connected to the recording system in such a way that once the signal relative to the absence of the jet is received, further control operations, alarm operations or reset operations can be carried out.

[0032] If the nozzle does not emit drops, it means that the nozzle is clogged and therefore the unclogging procedure can be activated.

[0033] The unclogging procedure can be carried out automatically by the system.

[0034] After trying to unclog the nozzle, the test is repeated and even if in this case correct ejection of drops is not detected, an alarm is activated which requires intervention by the operator, in order to proceed with manual unclogging or replacement of the printing head.

[0035] Advantageously, the control is carried out in a dark zone and preferably inside a special chamber 1.

[0036] The system can be implemented by means of a controlling device comprising a chamber 1 having:

• at least one opening, having shape and dimensions compatible with the shape and dimensions of the printing head, said at least one opening being, at the right moment, at the outlet point at which the ink exits from said nozzle;
• at least one recording system 5 suitable for recording the zone intended to be crossed by the ink jet 2;
• at least one lighting system 3 suitable for lighting the zone intended to be crossed by the ink jet 2.

[0037] Advantageously, the nozzle of the printing head is moved until it is positioned near said chamber, preferably above it, but, in any case, in such a way that the ink drop can fall into said opening.

[0038] This movement can be caused directly by the automation mechanism which controls the movement of the printing head to an operating position.

[0039] Said movement may also be a movement of the controlling system which moves, together with the chamber, to arrive under the printing head in such a way as to be able to check its correct operation.

[0040] In an embodiment, before one possible drop, preferably more than one drop, is emitted by the at least one nozzle of the printing head, the recording system, a video camera, is set up for acquisition for an acquisition time longer than the time taken by the drop to cross the field of vision of the video camera.

[0041] In an embodiment, when the drop passes through the light beam 4 generated by the lighting source, preferably by the laser 3, a flash of light is produced by diffraction. This flash of light is detected by the video camera.

[0042] In an embodiment, by checking that the image acquired by the video camera has a clear dot on a dark background, it is possible to detect the actual production of the drop by the specific controlled nozzle.

[0043] Advantageously, in the latter case, the system provides that a signal is transmitted to a controlling system, generally a PLC or a suitably programmed processor which controls the continuation of the printing process.

[0044] In an embodiment, by checking that the image acquired by the video camera is completely dark, it is confirmed that the at least one examined nozzle has not emitted the jet and is therefore clogged.

[0045] Advantageously, in the latter case, the system provides that an alarm signal is emitted.

[0046] Advantageously, in the latter case, the system envisages that a signal is transmitted to a controlling system, generally a PLC or a suitably programmed processor which makes it possible to carry out the interruption of the printing process and /or the unclogging procedure and/or any other operation that may be useful or necessary.

[0047] In an embodiment, after trying to clear the nozzle, the test is repeated, and If correct ejection of drops is not detected even in this case, an alarm is activated which requires intervention by the operator, in order to proceed with manual unclogging or replacement of the printing head. Advantageously, the control is carried out in a dark area and preferably inside a special chamber 1.

[0048] A device for controlling operation of at least one nozzle, preferably more than one, of a printing head, comprises a box structure 1 having a top opening through which the jet 2 of ink drops passes, at least one lighting source 3 and at least one recording system 5.

[0049] In an embodiment, said opening is kept closed in the rest phase so that no dust or other residue can enter the box structure, and it is opened only near the printing head when operation is to be controlled.

[0050] In an embodiment, the controlling station in which the controlling system and/or the controlling device 1 works is located at any point of the production line in such a way that the printing head is positioned above said point, emits the jet of ink drops and proceeds with the operation.

[0051] In an embodiment, the printing head is moved so as to be positioned above the above mentioned controlling station and/or device.

[0052] In an embodiment, the above mentioned controlling station and/or device are movable and are positioned below the printing head.

[0053] The invention further comprises a method which makes it possible to implement parts of the functions provided for by the system.

[0054] Specifically, the method comprises at least the following steps:

• checking the detection of at least one ink drop by the recording system;
• if the result is positive, transmitting a signal to a controlling system, generally a PLC or a suitably programmed processor, which allows continuation of the printing process.

[0055] In addition to the steps described above, the method also provides the following steps, carried out alone or in addition to the previous steps:

• checking the detection of at least one ink drop by the recording system;
• if the result is negative, emitting at least one alarm signal.

[0056] The method further comprises the following steps:

• checking the detection of at least one ink drop by the recording system;
• if the result is negative, transmitting at least one signal to a controlling system, generally a PLC or a suitably programmed processor which makes it possible to interrupt the printing process and /or to activate the unclogging procedure and/or to carry out any other operation that may be useful or necessary.

[0057] The method also provides the following step:

• trying to clear the clogged nozzle and repeating the controlling procedure, and possibly emitting an alarm or other signal, if the controlling procedure is negative.

[0058] As an example, as one of the forms of implementation of the above mentioned method, there is a program for an electronic processor suitable for carrying out one or more of the above mentioned steps.

[0059] There is also an electronic processor programmed for carrying out one or more of the steps of the method described above.

Claims

1. A combination of an apparatus for controlling an ink-jet printing head (6) and an ink-jet printing head (6), the apparatus comprising a lighting device (3) for lighting with a light beam (4) a passage zone through which at least one ink drop (2) emitted by a nozzle of said printing head (6) can pass and a recording system (5) for recording said at least one drop (2) when said at least one drop (2) is made visible by said lighting device (3), said recording system comprising a video camera (5) programmed in such a way as to have an exposure time longer than the time required by said at least one drop (2) to cross said passage zone, whereby the passage zone is the visual field of the camera (5), the apparatus further comprising a processor configured in such a way that, if a signal relative to the absence of drop is received, further control operations can be carried out, characterized in that said lighting device (3) is positioned in such a way that, when said lighting device (3) illuminates said drop (2) in said passage zone, said drop (2) generates a light diffusion that is detectable by said recording system (5).

2. A combination according to claim 1, wherein said lighting device (3) is positioned in such a way that said light beam (4) intersects the path of said at least one drop (2) in said passage zone.

3. A combination according to claim 2, wherein said lighting device (3) is so configured that said light beam (4) is substantially perpendicular to said path.

4. A combination according to any one of claims 1 to 3, wherein said lighting device (3) is so configured that said light beam (4) lies substantially in a plane.

5. A combination according to claim 4, wherein said plane is horizontal.

6. A combination according to any one of claims 1 to 5, wherein said lighting device (3) is selected from a group consisting of: laser lighting device, LED, halogen lamp.

7. A combination according to any one of claims 1 to 6, wherein said recording system (5) is positioned in such a way as not to be directly struck by said light beam (4).

8. A combination according to claim 7, wherein said recording system (5) is arranged along an axis that is non-parallel in relation to a further axis along which said light beam (4) is emitted.

9. A combination according to claim 8, wherein said axis and said further axis are substantially perpendicular.

10. A combination according to claim 7 or 8, wherein said axis and said further axis lie on the same plane.

11. A combination according to claim 7, wherein the recording system (5) is positioned on the same side and on the same axis as the lighting device (3), in such a way as to record both a line generated by the lighting device (3) on the camera background and the ink drops emitted by the nozzle, thus allowing the correct working of the lighting device (3) to be checked at the same time.

12. A combination according to any one of claims 1 to 11, and further comprising a housing (1) for enclosing said passage zone, so as to protect said passage zone from light sources other than said lighting device (3).

13. A combination according to claim 12, wherein said housing (1) comprises an opening through which said at least one drop (2) coming from said printing head (6) can pass.

14. A combination according to claim 13, and comprising closure means for opening or closing said opening selectively.

15. A combination according to any one of claims 1 to 14, and further comprising moving means for positioning said apparatus near said printing head (6).

16. A combination according to any one of claims 1 to 15, and further comprising a ceramic tiles decoration line, said printing head (6) being positioned along said line for printing a decoration on said ceramic tiles.

17. Method for controlling an ink-jet printing head (6), comprising the steps of:

- illuminating by means of a light beam (4) a passage zone through which at least one ink drop (2) emitted by a nozzle of said printing head (6) can pass;

- checking if said at least one drop (2) is present in said passage zone by recording said passage zone illuminated by said light beam (4),

- if the result of the checking step is positive, transmitting a signal to a controlling system which allows continuation of a printing process,

whereby for recording said passage zone a video camera (5) is used having an exposure time longer than the time required by said at least one drop (2) for crossing said passage zone and the passage zone is the visual field of the camera, characterized in that said checking comprises the camera (5) detecting the diffusion generated when said light beam (4) meets said drop (2) when crossing said passage zone.

18. Method according to claim 17, wherein, if said at least one drop (2) is present in said passage zone, a clear flash is seen against a dark background when recording said passage zone.

19. Method according to claim 17 or 18, wherein, if said at least one drop (2) is not present in said passage zone, a dark image is seen when recording said passage zone.

20. Method according to any one of claims 17 to 19, and comprising the step of moving said printing head (6) to bring said printing head (6) near said light beam (4).

21. Method according to any one of claims 17 to 19, and comprising the step of moving a lighting device (3) suitable for emitting said light beam (4) and a recording device (5) suitable for recording said passage zone to bring said lighting device (3) and said recording device (5) near said printing head (6).

22. Method according to any one of claims 17 to 21, wherein the controlling system is a PLC or a suitably programmed processor.

23. Method according to any one of claims 17 to 22, wherein, if said at least one drop (2) is not detected in said passage zone, there is provided emitting at least one alarm signal.

24. Method according to any one of claims 17 to 23, wherein, if said at least one drop (2) is not detected in said passage zone, there is provided transmitting at least one signal to the controlling system, generally a PLC or a suitably programmed processor which makes it possible to interrupt the printing process and/or to activate an unclogging procedure.

25. Method according to claim 24, and further comprising the following step:

- trying to clear the clogged nozzle and repeating the checking procedure and possibly emitting an alarm or other signal, if said at least one drop (2) is not detected in said passage zone.

Ansprüche

1. Kombination einer Vorrichtung zur Steuerung eines Tintenstrahldruckkopfes (6) und eines Tintenstrahldruckkopfes (6), wobei die Vorrichtung eine Beleuchtungseinrichtung (3) umfasst, um mit einem Lichtstrahl (4) einen Durchgangsbereich zu beleuchten, durch den mindestens ein Tintentropfen (2), abgegeben von einer Düse des genannten Druckkopfs (6), durchgehen kann, sowie ein Aufzeichnungssystem (5) zum Aufzeichnen des genannten mindestens einen Tropfens (2), wenn der genannte mindestens eine Tropfen (2) durch die genannte Beleuchtungseinrichtung (3) sichtbar gemacht wird, wobei das genannte Aufzeichnungssystem eine Videokamera (5) umfasst, so programmiert, dass sie eine Belichtungszeit besitzt, die länger ist als die Zeit, die der mindestens eine Tropfen (2) benötigt, um den genannten Durchgangsbereich zu durchqueren, wobei der Durchgangsbereich das Sichtfeld der Kamera (5) ist; die Vorrichtung umfasst ferner einen Prozessor, der so konfiguriert ist, dass beim Empfang eines Signals bezüglich der Abwesenheit von Tropfen weitere Kontrollvorgänge durchgeführt werden können, dadurch gekennzeichnet, dass die genannte Beleuchtungseinrichtung (3) so positioniert ist, dass der genannte Tropfen (2) eine Lichtdiffusion generiert, die durch das genannte Aufzeichnungssystem (5) detektiert wird, wenn die genannte Beleuchtungseinrichtung (3) den genannten Tropfen (2) im genannten Durchgangsbereich beleuchtet.

2. Kombination gemäß Anspruch 1, wobei die genannte Beleuchtungseinrichtung (3) so positioniert ist, dass der genannte Lichtstrahl (4) den Weg des genannten mindestens einen Tropfens (2) im genannten Durchgangsbereich kreuzt.

3. Kombination nach Anspruch 2, wobei die genannte Beleuchtungseinrichtung (3) so konfiguriert ist, dass der genannte Lichtstrahl (4) im Wesentlichen senkrecht zu genanntem Weg angeordnet ist.

4. Kombination nach einem der Ansprüche 1 bis 3, wobei die genannte Beleuchtungseinrichtung (3) so konfiguriert ist, dass der genannte Lichtstrahl (4) im Wesentlichen in einer Ebene liegt.

5. Kombination nach Anspruch 4, wobei die genannte Ebene waagerecht ist.

6. Kombination nach einem der Ansprüche 1 bis 5, wobei die genannte Beleuchtungseinrichtung (3) aus einer Gruppe ausgewählt ist, bestehend aus: Laserbeleuchtungseinrichtung, LED, Halogenlampe.

7. Kombination nach einem der Ansprüche 1 bis 6, wobei das genannte Aufzeichnungssystem (5) so positioniert ist, das es nicht unmittelbar vom genannten Lichtstrahl (4) getroffen wird.

8. Kombination nach Anspruch 7, wobei das genannte Aufzeichnungssystem (5) an einer Achse angeordnet ist, die nicht parallel zu einer weiteren Achse verläuft, an der der genannte Lichtstrahl (4) abgegeben wird.

9. Kombination nach Anspruch 8, wobei die genannte Achse und die genannte weitere Achse im Wesentlichen lotrecht sind.

10. Kombination nach Anspruch 7 oder 8, wobei die genannte Achse und die genannte weitere Achse auf derselben Ebene liegen.

11. Kombination nach Anspruch 7, wobei das Aufzeichnungssystem (5) auf derselben Seite und auf derselben Achse wie die Beleuchtungseinrichtung (3) positioniert ist, und zwar so, dass es sowohl eine durch die Beleuchtungseinrichtung (3) erzeugte Linie auf dem Kamerahintergrund als auch die von der Düse abgegebenen Tintentropfen aufzeichnet und so die korrekte Arbeit der Beleuchtungseinrichtung (3) ermöglicht, zu prüfen zur selben Zeit.

12. Kombination nach einem der Ansprüche 1 bis 11 und ferner umfassend ein Gehäuse (1) für das Umhüllen des genannten Durchgangsbereichs, sodass der genannte Durchgangsbereich vor Lichtquellen geschützt wird, die nicht die genannte Beleuchtungseinrichtung (3) sind.

13. Kombination nach Anspruch 12, wobei das genannte Gehäuse (1) eine Öffnung umfasst, durch die der mindestens eine Tropfen (2), kommend vom genannten Druckkopf (6), fließen kann.

14. Kombination nach Anspruch 13, umfassend Verschließmittel zum selektiven Öffnen oder Schließen der genannten Öffnung.

15. Kombination nach einem der Ansprüche 1 bis 14, ferner umfassend Bewegungsmittel zum Positionieren der genannten Vorrichtung in der Nähe des genannten Druckkopfs (6).

16. Kombination nach einem der Ansprüche 1 bis 15, ferner umfassend eine Keramikfliesendekorationsanlage, wobei der genannte Druckkopf (6) an der genannten Anlage positioniert ist, um eine Dekoration auf die genannten Keramikfliesen zu drucken.

17. Methode zur Steuerung eines Tintenstrahldruckkopfes (6), umfassend die Schritte:

- Beleuchten eines Durchgangsbereichs, durch den mindestens ein Tintentropfen (2), abgegeben von einer Düse des genannten Druckkopfs (6), durchlaufen kann, mittels eines Lichtstrahls (4);

- Prüfen, ob der genannte mindestens eine Tropfen (2) im genannten Durchgangsbereich vorhanden ist, und zwar durch das Aufzeichnen des genannten Durchgangsbereichs, beleuchtet durch den genannten Lichtstrahl (4),

- falls das Ergebnis der Prüfphase positiv ist, Übermitteln eines Signals an ein Steuerungssystem, das die Fortsetzung eines Druckverfahrens ermöglicht, wobei für die Aufzeichnung des genannten Durchgangsbereichs eine Videokamera (5) verwendet wird, die eine Belichtungszeit besitzt, die länger ist als die Zeit, die der genannte eine Tropfen (2) benötigt, um den genannten Durchgangsbereich zu durchqueren, und der Durchgangsbereich das Sichtfeld der Kamera ist, dadurch gekennzeichnet, dass das genannte Prüfen die Kamera (5) zur Detektion der Diffusion umfasst, die erzeugt wird, wenn der genannte Lichtstrahl (4) auf den genannten Tropfen (2) trifft, wenn dieser den genannten Durchgangsbereich durchquert.

18. Methode nach Anspruch 17, wobei ein klarer Blitz gegen einen dunklen Hintergrund beim Aufzeichnen des genannten Durchgangsbereichs zu sehen ist, wenn der genannte mindestens eine Tropfen (2) im genannten Durchgangsbereich vorhanden ist.

19. Methode nach Anspruch 17 oder 18, wobei ein dunkles Bild beim Aufzeichnen des genannten Durchgangsbereichs zu sehen ist, wenn der genannte mindestens eine Tropfen (2) nicht im genannten Durchgangsbereich vorhanden ist.

20. Methode nach einem der Ansprüche 17 bis 19, umfassend die Phase der Bewegung des genannten Druckkopfs (6), um den genannten Druckkopf (6) in die Nähe des genannten Lichtstrahls (4) zu bringen.

21. Methode nach einem der Ansprüche 17 bis 19, umfassend die Phase der Bewegung einer Beleuchtungseinrichtung (3), geeignet, um den genannten Lichtstrahl (4) abzugeben, und eine Aufzeichnungseinrichtung (5), geeignet, um den genannten Durchgangsbereich aufzuzeichnen, um die genannte Beleuchtungseinrichtung (3) und die genannte Aufzeichnungseinrichtung (5) in die Nähe des genannten Druckkopfs (6) zu bringen.

22. Methode nach einem der Ansprüche 17 bis 21, wobei das Steuerungssystem eine SPS oder ein geeignet programmierter Prozessor ist.

23. Methode nach einem der Ansprüche 17 bis 22, wobei mindestens ein Alarmsignal zur Verfügung gestellt wird, wenn der genannte mindestens eine Tropfen (2) nicht im genannten Durchgangsbereich detektiert wird.

24. Methode nach einem der Ansprüche 17 bis 23, wobei mindestens ein Signal zum Steuerungssystem, bei dem es sich im Allgemeinen um eine SPS oder einen geeignet programmierten Prozessor handelt, gesendet wird, das es möglich macht, das Druckverfahren zu unterbrechen und/oder ein Verfahren zum Freimachen zu aktivieren, wenn der genannte mindestens eine Tropfen (2) nicht im genannten Durchgangsbereich detektiert wird.

25. Methode nach Anspruch 24, ferner umfassend den folgenden Schritt:

- Versuch, die verstopfte Düse freizumachen und Wiederholung des Prüfverfahrens und möglichst Aussenden eines Alarms oder eines anderen Signals, wenn der genannte mindestens eine Tropfen (2) nicht im genannten Durchgangsbereich detektiert wird.

Revendications

1. Association d'un dispositif de commande d'une tête d'impression à jet d'encre (6) et d'une tête d'impression à jet d'encre (6), le dispositif comprenant un appareil d'éclairage (3) pour éclairer par un faisceau lumineux (4) une zone de passage par laquelle peut passer au moins une goutte d'encre (2) émise par une buse de ladite tête d'impression (6), et un système d'enregistrement (5) pour enregistrer ladite au moins une goutte (2), quand ladite au moins une goutte (2) est rendue visible par ledit appareil d'éclairage (3), ledit système d'enregistrement comprenant une caméra vidéo (5), programmée de sorte à avoir un temps d'exposition plus important que le temps nécessaire à ladite au moins une goutte (2) pour traverser ladite zone de passage, dans laquelle la zone de passage est le champ visuel de la caméra (5), le dispositif comprenant aussi un processeur configuré de sorte que, si un signal indiquant l'absence de goutte est reçu, d'autres opérations de contrôle peuvent être effectuées, caractérisée en ce que ledit appareil d'éclairage (3) est positionné de sorte que, quand ledit appareil d'éclairage (3) éclaire ladite goutte (2) dans ladite zone de passage, ladite goutte (2) génère une diffusion de lumière qui peut être détectée par ledit système d'enregistrement (5).

2. Association selon la revendication 1, caractérisée en ce que ledit appareil d'éclairage (3) est positionné de sorte que ledit faisceau lumineux (4) croise la course de ladite au moins une goutte (2) dans ladite zone de passage.

3. Association selon la revendication 2, caractérisée en ce que ledit appareil d'éclairage (3) est configuré de sorte que ledit faisceau lumineux (4) est pratiquement perpendiculaire à ladite course.

4. Association selon l'une quelconque des revendications 1 à 3, caractérisée en ce que ledit appareil d'éclairage (3) est configuré de sorte que ledit faisceau lumineux (4) se situe pratiquement dans un plan.

5. Association selon la revendication 4, caractérisée en ce que ledit plan est horizontal.

6. Association selon l'une quelconque des revendications 1 à 5, caractérisée en ce que ledit appareil d'éclairage (3) est choisi dans un groupe comprenant : appareil d'éclairage laser, LED, lampe halogène.

7. Association selon l'une quelconque des revendications 1 à 6, caractérisée en ce que ledit système d'enregistrement (5) est positionné de sorte à ne pas être directement touché par ledit faisceau lumineux (4).

8. Association selon la revendication 7, caractérisée en ce que ledit système d'enregistrement (5) est disposé le long d'un axe non parallèle à un autre axe le long duquel est émis ledit faisceau lumineux (4).

9. Association selon la revendication 8, caractérisée en ce que ledit axe et ledit autre axe sont pratiquement perpendiculaires.

10. Association selon les revendications 7 ou 8, caractérisée en ce que ledit axe et ledit autre axe se trouvent sur le même plan.

11. Association selon la revendication 7, caractérisée en ce que le système d'enregistrement (5) est positionné sur le même côté et sur le même axe que l'appareil d'éclairage (3), de sorte à enregistrer à la fois une ligne générée par l'appareil d'éclairage (3) sur l'arrière-plan de la caméra et les gouttes d'encre émises par la buse, permettant ainsi de vérifier aussi le bon fonctionnement de l'appareil d'éclairage (3).

12. Association selon l'une quelconque des revendications 1 à 11, et comprenant aussi un logement (1) pour abriter ladite zone de passage, afin de protéger ladite zone de passage des sources lumineuses autres que ledit appareil d'éclairage (3).

13. Association selon la revendication 12, caractérisée en ce que ledit logement (1) comprend une ouverture par laquelle peut passer ladite au moins une goutte (2) provenant de ladite tête d'impression (6).

14. Association selon la revendication 13, et comprenant des moyens de fermeture pour ouvrir ou fermer ladite ouverture de manière sélective.

15. Association selon l'une quelconque des revendications 1 à 14, et comprenant aussi des moyens de déplacement pour positionner ledit dispositif près de ladite tête d'impression (6).

16. Association selon l'une quelconque des revendications 1 à 15, et comprenant aussi une ligne de décoration des carreaux de céramique, ladite tête d'impression (6) étant positionnée le long de ladite ligne pour imprimer une décoration sur lesdits carreaux de céramique.

17. Méthode de commande d'une tête d'impression à jet d'encre (6), comprenant les étapes de :

- éclairer par un faisceau lumineux (4) une zone de passage par laquelle peut passer ladite au moins une goutte d'encre (2) émise par une buse de ladite tête d'impression (6) ;

- contrôler si ladite au moins une goutte (2) est présente dans ladite zone de passage en enregistrant ladite zone de passage éclairée par ledit faisceau lumineux (4),

- si le résultat est positif à l'étape de contrôle, transmettre un signal à un système de commande qui autorise la continuation d'un procédé d'impression, dans laquelle, pour enregistrer ladite zone de passage, une camera vidéo (5) est utilisée, ayant un temps d'exposition plus important que le temps nécessaire à ladite au moins une goutte (2) pour traverser ladite zone de passage, et la zone de passage est le champ visuel de la caméra, caractérisée en ce que ledit contrôle comprend la caméra (5) détectant la diffusion générée quand ledit faisceau lumineux (4) rencontre ladite goutte (2), quand elle traverse ladite zone de passage.

18. Méthode selon la revendication 17, caractérisée en ce que, si ladite au moins une goutte (2) est présente dans ladite zone de passage, une lueur intense est visualisée contre un arrière-plan noir pendant l'enregistrement de ladite zone de passage.

19. Méthode selon les revendications 17 ou 18, caractérisée en ce que, si ladite au moins une goutte (2) n'est pas présente dans ladite zone de passage, une image noire est visualisée pendant l'enregistrement de ladite zone de passage.

20. Méthode selon l'une quelconque des revendications 17 à 19, et comprenant l'étape de déplacer ladite tête d'impression (6) pour amener ladite tête d'impression (6) près dudit faisceau lumineux (4).

21. Méthode selon l'une quelconque des revendications 17 à 19, et comprenant l'étape de déplacer un appareil d'éclairage (3) pouvant émettre ledit faisceau lumineux (4) et un dispositif d'enregistrement (5) pouvant enregistrer ladite zone de passage pour amener ledit appareil d'éclairage (3) et ledit dispositif d'enregistrement (5) près de ladite tête d'impression (6).

22. Méthode selon l'une quelconque des revendications 17 à 21, caractérisée en ce que le système de commande est un API ou un processeur programmé de façon appropriée.

23. Méthode selon l'une quelconque des revendications 17 à 22, caractérisée en ce que, si ladite au moins une goutte (2) n'est pas détectée dans ladite zone de passage, au moins un signal d'alarme est émis.

24. Méthode selon l'une quelconque des revendications 17 à 23, caractérisée en ce que, si ladite au moins une goutte (2) n'est pas détectée dans ladite zone de passage, au moins un signal est transmis au système de commande, en général un API ou un processeur programmé de façon appropriée qui permet d'interrompre le procédé d'impression et/ou de lancer une procédure de désincrustation.

25. Méthode selon la revendication 24, et comprenant aussi l'étape suivante :

- essayer de désincruster la buse bouchée et refaire le procédé de contrôle et, si possible, émettre une alarme ou un autre signal, si ladite au moins une goutte (2) n'est pas détectée dans ladite zone de passage.

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