EP3953186A1

EP3953186A1 - Method for transporting printing media and for cleaning a nozzle front panel

Info

Publication number: EP3953186A1
Application number: EP20751472.0A
Authority: EP
Inventors: Manfred KOFLER; Stefan WALDNER
Original assignee: Durst Group AG
Current assignee: Durst Group AG
Priority date: 2019-08-07
Filing date: 2020-08-05
Publication date: 2022-02-16
Anticipated expiration: 2040-08-05
Also published as: EP3953186B1; BR112021023676A2; EP3953186C0; CN114126879A; PL3953186T3; WO2021023400A1; ES2968355T3; CN114126879B

Abstract

The invention relates to a method for transporting piecemeal printing media (101) into the effective region of a print head (103) and out of said effective region again, and for cleaning at least one part of at least one nozzle front panel (105) provided on the print head (103), wherein the method comprises the steps of: a) providing a printing system (100) that comprises the print head (103) having the nozzle front panel (105), wherein the print head (103) comprises at least one print module (107) having at least one nozzle panel (109), from which droplets of a printable composition can be discharged; b) transporting the printing media (101) in a transport direction (T) in such a way that printing media (101) can be transported into the effective region of the nozzle front panel (105) and out of said region again; c) cleaning the at least one part of the nozzle front panel (105) by means of one or more fluid flow configurations (111) from a fluid-flow-activating cleaning device (114), wherein the fluid flow configurations (111) comprise at least one fluid flow directed against the at least one part of the nozzle front panel (105), wherein the nozzle front panel (105) comprises the nozzle panel (109), wherein at least some of the printing media (101) are transported in the transport direction (T) so as to be spaced apart from at least one of their closest adjacent printing media (101), as a result of which gaps (L) are produced between these spaced-apart adjacent printing media (101) in the transport direction (T) and the cleaning device (114) activates fluid flow not necessarily always but exclusively in the region of the gaps (L) and so as to be synchronised with said gaps.

Description

Process for transporting print media and cleaning a nozzle faceplate

The present invention relates to a method for transporting print media piece by piece into and out of the effective area of a print head and for cleaning at least part of at least one nozzle front plate provided on the print head. The invention also relates to a printing system for carrying out the method according to the invention.

Printing systems can print different print media, such as ceramic tiles, sheets of paper, sheets of corrugated cardboard, metal plates, wooden plates or glass plates with a print head, which typically comprises several printing modules with several nozzle plates with nozzles from which drops of a printable composition can be output. In any case, the nozzle plates must be cleaned from time to time in order to enable a trouble-free printing operation, the production of defect-free printed print media being of great importance.

Soiled nozzle plates to be cleaned can form over time during printing operation if, for example, undesired wetting of the nozzle plate surface by ink takes place, which accordingly has to be cleaned regularly.

In DE 102 56 879 A1, such regular cleaning of a nozzle plate of a print head is achieved by interrupting the printing operation before cleaning and then removing the print head so far from the conveyor belt disclosed therein for transporting a printing material that a cleaning device parked next to the print head can be guided from its parking position into the area between the print head and the conveyor belt and is guided there accordingly for cleaning. The nozzle plate is cleaned in such a way that an impulse of a gas flow is passed over the nozzle plate, with which paint residues and / or foreign particles adhering to the nozzle plate are transported to a detachment edge and detached there from the nozzle plate.

The printing operation of the above-described printing system from the prior art has the disadvantage that it has to be repeatedly interrupted at relatively short time intervals for cleaning the nozzle plate in order not to produce any rejects.

It would be desirable to have a method which can be used to reduce the frequency of interruptions in the transport of the print media to be carried out in a defined time interval, which is necessary in conventional methods To reduce nozzle plate cleaning both in the printing operation but also in transit operation of the printing system.

In the following, transit operation of a printing system is to be understood as the use of the same, at least for a certain period of time, exclusively in its capacity as a transit system, in which print media pass through the effective area of a print head of this printing system without being printed and are only printed in a further printing system downstream of this printing system .

It is therefore the object of the invention to provide a method for increasing the throughput of waste-free printing media through the effective area of a nozzle front plate of a printing system while reducing or even avoiding transport interruptions for cleaning the nozzle front plate.

According to the invention, the object is achieved with a method which comprises the features of claim 1. The subclaims relate to further advantageous and optionally additionally inventive embodiments. The invention is based on the idea of transporting print media into and out of the effective area of a nozzle front plate, with at least some of the print media being transported at a distance from at least one of their next adjacent print media, which creates gaps between them in the transport direction and cleaning the nozzle front plate is carried out by means of a fluid flow directed against the nozzle front plate in such a way that a fluid flow cleaning device is not necessarily activated but always exclusively in the area of the gaps and synchronized with them. A method according to the invention for transporting print media is carried out with a printing system comprising a print head, on which print head at least one nozzle front plate is provided, the print head comprising at least one print module with at least one nozzle plate from which drops can be output. The cleaning of the at least one part of the nozzle front plate takes place by means of one or more fluid flow configurations from a cleaning device that activates the fluid flow. The nozzle front plate encompasses the nozzle plate. In the following, a medium that is to be printed is referred to as a print medium. A “dummy” or “placeholder” that cannot or cannot be printed, which can also create a gap between the next adjacent print media, must be distinguished from a print medium. Accordingly, the method according to the invention is a method for transporting print media in pieces into and out of the effective area of a print head and for cleaning at least part of at least one nozzle front plate provided on the print head, the method comprising the steps of: a) providing a printing system comprising the print head with the nozzle front plate, wherein the print head comprises at least one print module with at least one nozzle plate, from which drops of a printable composition can be output, b) transport of the print media along a transport direction such that print media is in the effective area of the nozzle front plate be transported in and out of this again, c) cleaning of the at least one part of the nozzle front plate by means of one or more fluid flow configurations from a fluid flow activating cleaning device, wherein the fluid flow configuration Rations include at least one directed against the at least part of the nozzle front plate fluid flow.

According to the invention, the nozzle front plate comprises the nozzle plate, with at least some of the print media being transported at a distance in the transport direction to at least one of their next adjacent print media, which results in gaps between these spaced-apart adjacent print media in the transport direction and the cleaning device fluid flow not necessarily but always exclusively in the area of the gaps and activated synchronized with these.

The method according to the invention is particularly suitable when, for example, the nozzle front plate of the printing system is used under working conditions in which large amounts of liquid condense out on the nozzle front plate in a very short time. Such contamination is known from the ceramic industry, for example, when ceramic printing media, after they have been produced in a pressing device and have passed through several stations, and then in a state moistened with water and at a temperature of the printing media between 30 ° C and 120 ° C in the printing system can be transported in and out of this again. The water from the ceramic pressure media changes into the gas phase, from which the gaseous water can condense out again on the nozzle front plate.

When additional printing is then carried out, part of the composition printed on these printing media changes into the gas phase, from which it can condense out again on the nozzle front plate. As time progresses, the drops can keep growing, until the force of gravity on the drops exceeds the holding forces on the nozzle faceplate, causing drops of the composition to detach and fall onto the print media.

In this way and in the ways described below, spoiled products produced cannot be used as high-quality products, but can at best be sold on the market as second-class, inferior products, whereby they can in any case be classified as rejects.

It is clear that the printable composition comprises a volatile component, at least in the case described above. This is typically water and / or a polyglycol. If printing media are printed in a printing system with a glaze suspension as a printable composition, relatively large amounts, in particular maximum amounts greater than 200 g / m ² to 1500 g / m ² based on a full-surface application, are often applied to the printing media to create relief-like or full-surface decorations to manufacture. The glaze suspension is often heated to a temperature between 30 ° C and 50 ° C before the media is printed. In this case there is a considerable rate of evaporation of liquid from the glaze suspension applied to the printing media, some of which condenses out again on the nozzle front plate, so that the nozzle front plate becomes particularly heavily soiled without corresponding repeated cleaning.

During an investigation, the inventors have observed that if large amounts of printed glaze composition are printed, even if the nozzle front plate is heated electrically to temperatures of 50 ° C., for example, it can occur that the problem of water condensation is partially but completely inadequate Dimensions remedy can be provided.

The condensation of liquid from the air can create another problem. The printing of the print media is normally known to take place at a very small height of a fraction of a millimeter or a few millimeters between the nozzle faceplate and the surface of the print media. Drops that form on the nozzle front plate over time do not even have to fall onto the print media due to gravity in order to contaminate them, but can grow to a size where they hang down at "eye level" with the print media being transported at least level with the surface of the print media, causing it to be carried away by the print media. This often results in dirt that is stretched along the surface of the print media. Another cause which leads to nozzle contamination, especially when printing ceramic printing media with the glaze suspension, is due to the bounce of the drops from the surface of the printing media to be printed back onto the nozzle front plate. Several variables play a role in the rebound behavior. These include the size and speed of the drops as well as the distance between the nozzle front plate and the surface of the printing medium to be printed.

Nozzle front plates can also become soiled if, due to poor jetting behavior, so-called satellites or satellite droplets form in the main droplets that are emitted and are emitted together with the main droplet in the form of very small droplets. The droplets form a droplet mist, which is deposited on the nozzle front plate and can contaminate it.

On the other hand, the contamination of the nozzle front plate can even be the result of manual cleaning of the same. With manual cleaning, clogged nozzles can be freed from dried-on ink residues. If the nozzle faceplate is not dried sufficiently, however, so much cleaning liquid can remain on the nozzle faceplate that this liquid can fall over time in the form of drops onto the print media or can be carried away by the print media as set out in the manner described above.

In a very particularly preferred embodiment of the method according to the invention, at least that entire area of the nozzle front plate to which the print media are exposed during transport through the effective area of the nozzle front plate is cleaned.

This has the advantage that the contamination of the printing media can be prevented on the entire surface of the printing media. According to a preferred embodiment of the provided print head, it comprises at least two print modules, each with at least one nozzle plate, the print modules being arranged one behind the other as seen in the transport direction of the print media. Here, the nozzle front plate comprises the nozzle plates of the print modules.

The nozzle front plate can comprise the nozzle plate and at least one frame plate, the side of the nozzle front plate facing the print media in particular lying in one plane with the nozzle plate and frame plate.

According to a particularly preferred embodiment of the method according to the invention, the cleaning device activates the fluid flow sequentially. This embodiment is advantageous because gaps between the print media arranged in the transport direction can be selected to be relatively narrow, for example, with respect to the length of the nozzle front plate in the transport direction.

According to another preferred embodiment, during the transport of the print media through the effective area of the nozzle front plate, the cleaning of the at least one part of the nozzle front plate according to step (c) is accompanied at least at times.

According to a particularly preferred embodiment, the method comprises the step (d) of printing the print media in that the at least one nozzle plate of the at least one print module emits drops of the printable composition, preferably an ink or a glaze suspension.

The printable composition used, preferably the ink or the glaze suspension, can comprise at least one volatile component, preferably water and / or at least one non-aqueous polar solvent. The non-aqueous polar solvent is typically a polyglycol. According to a preferred embodiment of the glaze suspension or ink, the water is accordingly present in the glaze suspension or in the ink in a proportion between 30% by weight and 60% by weight based on the weight of the glaze suspension or the ink.

According to a particularly preferred embodiment, the print head comprises a gas flow module which has at least a first and a second slot nozzle in the nozzle front plate, with a gas in the gap between the nozzle front plate and the print media to be printed in the method at least when printing the print media according to step (d) is discharged from the first slot nozzle and sucked in again through the second slot nozzle, in such a way that a laminar gas flow is generated in the gap.

Such a method has the advantage that if, for example, water-containing air is present in the gap between the print media and the nozzle front plate, this is partially removed and thus the amount of water that can and will condense out on the nozzle front plate is reduced.

According to a preferred embodiment, the nozzle front plate is designed as a closed, liquid-tight nozzle front plate, with the exception of the openings of the nozzles and preferably except for the openings of the slot nozzles of the gas flow module. According to a particularly preferred embodiment, the print head is designed as a closed, liquid-tight print head. These developments are advantageous because they can reduce or avoid the penetration of air humidity and other volatile constituents of an ink or a glaze suspension from the gas phase into the print head. The ingress of humidity into the printhead can damage the printhead.

According to a further particularly preferred embodiment, the cleaning is carried out at periodic time intervals, the respective interval duration being selected as short as necessary but as long as possible, in such a way that within the respective interval duration a throughput free of waste during the transport or the transport and printing of the print media of the print media is ensured by the effective area of the nozzle front plate, a different, higher interval duration than the respective interval duration would have led to print media with waste.

This further development is advantageous because it enables the throughput of print media without waste to be increased further.

According to a further particularly preferred embodiment, printing according to step (d) and cleaning of the at least part of the nozzle front panel according to step (c) go hand in hand at least temporarily during the transport of the printing media through the effective area of the nozzle front plate.

In this way the fluid flow can preferably be activated with the cleaning device at least during the printing according to step (d), in such a way that the fluid flow does not cross the flight paths of the drops emitted from the nozzle plate or from the nozzle plates.

The transport of the print media can take place in a transport plane along the transport direction, the nozzle front plate of the print head being arranged above the transport plane, the transport according to step (b) and the cleaning according to step (c) at the same height X, preferably at the same target Height, take place between the nozzle front plate and the surface of the print media in a direction perpendicular to a transport plane of the print media.

In a preferred embodiment of the method, the transport according to step (b) and the cleaning according to step (c) and the printing according to step (d) take place at the same height (X), preferably at the same target height.

According to a further preferred embodiment of the method, the method comprises the steps: (e) Detecting an actual height by means of a sensor before the. Transport of the print media into the effective area of the nozzle front plate,

(f) Setting the ACTUAL height by means of a positioning device of the printing system if the recorded ACTUAL height does not correspond to a target height.

This development is advantageous because it allows different print media with different thicknesses to be transported through the effective area of the nozzle front plate.

The DESIRED height preferably corresponds to a predetermined value in a range between 0.4 mm and 15.0 mm. The person skilled in the art is aware of the nominal height to which he has to set the nozzle front plate in order to obtain a high quality print, and that this depends on several variables, such as the drop size, the drop speed and the straightness of the trajectory of the drops.

According to a preferred embodiment of the method, a single-pass inkjet printer is provided as the printing system in step (a), the transport of the print media taking place at a constant speed in the transport direction, and preferably at a speed of at least 3 m / min, particularly preferably at a Speed of at least 12m / min.

This embodiment offers the advantage, for example, that printed print media can be produced on an industrial scale.

The fluid can be a gaseous and / or liquid fluid, preferably a gas or gas mixture, particularly preferably air.

According to a preferred embodiment of the method, the fluid stream is emitted from one or more nozzles of the cleaning device, the nozzles preferably being designed as flat jet nozzles.

The cleaning device can be operated in such a way that the discharged fluid flow at each point of the at least one part of the nozzle front plate has at least such a high speed that it is suitable for entraining droplets of a liquid hanging down at least in one part of the nozzle front plate, preferably having such a high speed, that it completely cleans the part of the nozzle front plate or completely removes any liquid adhering to the nozzle front plate.

The cleaning device or the one nozzle or the plurality of nozzles of the cleaning device can be operated in such a way that the fluid flow emitted each point of the at least one part of the nozzle front plate has a speed of at least 5 meters / second, preferably at least 7 meters / second, particularly preferably at least 10 meters / second, very particularly preferably 15 meters / second. According to a preferred embodiment of the invention, the one or more nozzles of the cleaning device are provided movably in the transport direction, wherein during the cleaning according to step (c) the one or more nozzles are moved in the transport direction, preferably synchronously with the gaps. This preferred further development is advantageous because it allows a smaller number of nozzles to be provided in order to clean the at least part of the nozzle front plate than can be the case with stationary nozzles.

According to a further preferred embodiment of the method, the cleaning takes place via a plurality of fluid flow configurations with at least two fluid flows directed against one another and against the at least part of the nozzle front plate. These are preferably formed by at least two nozzles arranged along the transport direction.

This preferred embodiment is advantageous if, for example, very large nozzle front plates extending transversely to the transport direction have to be cleaned.

The method according to the invention is preferably used for producing relief-like or full-surface decorative glazes on printing media, the printing according to step

(c) takes place by adding drops from a glaze suspension in relative application quantities of a 200 g / m ² to 1500 g / m ² based on a full-surface application on the printing media (101), preferably between a 300 g / m ² to 1500 g / m ² are output based on a full-area order on the print media (101). According to a particularly preferred embodiment of the method, such high amounts of a glaze suspension are printed with a printing system which is designed as a single-pass inkjet printer, preferably designed as a single-pass inkjet printer with a ram-operated print module.

The glaze suspensions described in the description of the Italian application IT 10 2019 000 001 387 by the applicant of the same name should be mentioned here as an example of such glaze suspensions. As an example of print modules operated with a ram, those in the description of WO 2013/013983 A1 or WO 2019/042585 A1 and WO 2019/042586 A1 by the applicant of the same name, which are referred to therein as inkjet print heads for inkjet printers, and print modules of a print head of the invention Printing system can be. Due to the large inner diameter of the nozzles between 250 pm and 350 pm, such printing modules can print inkjet printing inks with larger particles than the otherwise typical piezoelectrically operated inkjet printing devices from the prior art, which typically include nozzles with an internal diameter of up to 50 pm.

According to a preferred embodiment of the method, the printing media are printed with drops of a glaze suspension tempered to a temperature in the range between 25 ° C and 50 ° C, preferably between 25 ° C and 45 ° C, particularly preferably between 30 ° C and 40 ° C or ink.

The print media can be in the effective range at a temperature between 30 ° C and 120 ° C, preferably between 40 ° C and 100 ° C, particularly preferably between 50 ° C and 90 ° C, very particularly preferably between 55 ° C and 85 ° C of the print head of the printing system.

In a preferred embodiment of the method, the print media, which are provided as ceramic print media, in particular unfired ceramic tiles, are accordingly moistened with water and at a temperature between 30 ° C and 120 ° C, preferably between 40 ° C and 100 ° C , particularly preferably between 50 ° C and 90 ° C, very particularly preferably between 55 ° C and 85 ° C transported into the effective range of the nozzle front plate, the nozzle front plate being tempered to a temperature that is lower than the temperature of the print media during the Transport of the same through the effective area of the nozzle front plate, whereby the nozzle front plate and the print media in the effective area of the nozzle front plate are aligned relative to one another in such a way that, with advancing time, drops form due to condensation of water vapor on the nozzle front plate and continue to grow until they cease after a certain time due to gravity r would fall onto the print media and / or hang from the nozzle faceplate in such a way that they would be carried away by the print media.

In a further preferred embodiment of the method, the printing media are provided as ceramic printing media, in particular unfired ceramic tiles, and are particularly preferred in a state moistened with water and at a temperature between 30 ° C and 120 ° C, preferably between 40 ° C and 100 ° C between 50 ° C and 90 ° C, whole particularly preferably transported between 55 ° C and 85 ° C into the effective area of the nozzle front plate, the nozzle front plate being heated to a temperature that is lower than the temperature of the print media during the transport of the same through the effective area of the nozzle front plate, the nozzle front plate and the Print media in the effective area of the nozzle front plate are aligned essentially horizontally relative to one another.

According to a particularly preferred embodiment, the nozzle front plate is tempered to a temperature which is lower than the temperature of the print media during the transport of the same through the effective area of the print head and which is between 25 ° C and 50 ° C, preferably between 25 ° C and 45 ° C , particularly preferably between 30 ° C and 40 ° C.

The print head is typically provided in such a way that the temperature of the nozzle front plate is largely determined or at least significantly co-determined by the temperature of the tempered glaze suspension or ink. According to a first preferred variant of the method, the printing system is provided with a transport device for transporting the print media in a transport plane along the transport direction, the nozzle front plate of the print head being arranged above the transport plane and the one or more nozzles outside the at least part of the nozzle front plate the transport direction and above the transport plane, and preferably mounted on the print head.

According to a particularly preferred embodiment of this first variant of the method, the transport device is provided as an endless belt conveyor, which preferably has a longitudinal direction and a transverse direction extending perpendicular thereto, which transverse direction is at least as wide as the effective area of the nozzle front plate, the endless belt conveyor particularly preferably having a cleaning unit for Removal of the drops collected on the endless conveyor belt is assigned.

According to a second preferred variant of the method, the printing system is provided with a transport device for transporting the print media in the transport plane along the transport direction, the nozzle front plate of the print head being arranged above the transport plane and the one or more nozzles inside or outside but below the transport plane be arranged on the transport device along the transport direction.

According to a particularly preferred embodiment of this second variant of the method, the transport device is a belt conveyor with at least two transverse to Transport direction spaced apart and parallel belts provided, wherein the belts are driven synchronously.

According to the method according to the invention, the printing media are preferably ceramic printing media, sheets of paper, sheets of corrugated cardboard, metal plates, wooden plates or glass plates, the printing media being particularly preferably ceramic printing media such as, for example, unfired tiles.

According to the first and second variant of the preferred embodiments of the method, the method preferably comprises the following steps:

- Providing a conveyor and transporting the print media with the conveyor to the transport device of the printing system, which is arranged downstream of the conveyor;

- Transfer of the print media from the conveyor to the transport device:

- Creating a gap between the next adjacent print media before or during the transfer of the print media from the conveyor to the transport device.

According to the invention, the object is also achieved by a printing system according to claim 23. This is done by a printing system comprising a) a transport device for printing media; b) at least one print head with at least one nozzle front plate provided on the print head, which print head comprises at least one print module with at least one nozzle plate for outputting drops of a printable composition; c) a cleaning device which makes it possible to activate a fluid flow directed against at least part of the nozzle front plate;

According to the invention, the nozzle front plate comprises the nozzle plate, the cleaning device being designed in such a way that one or more fluid flow configurations with at least one fluid flow directed against the at least one part of the nozzle front plate can be activated synchronously with gaps between adjacent print media in the transport direction.

In a preferred embodiment of the printing system, the cleaning device comprises one or more nozzles via which the fluid flow can be output, wherein the one or more nozzles are particularly preferably flat jet nozzles.

In a further preferred embodiment of the printing system, the printing system comprises a control device for carrying out at least one method according to the invention. According to a preferred embodiment of the printing system, the nozzle front plate comprises the nozzle plate and at least one frame plate, the side of the nozzle front plate facing the print media, in particular with the nozzle plate and frame plate, lying in one plane.

According to a further preferred embodiment, the print head comprises at least two print modules, each with at least one nozzle plate, the print modules being arranged one behind the other as seen in the transport direction of the print media. Here, the nozzle front plate comprises the nozzle plates of the print modules.

According to a preferred embodiment, the printing system according to the invention comprises a supply system and the at least one printing module, which can supply the at least one printing module with the printable composition, preferably the glaze suspension or the ink, the ink supply system means for tempering the glaze suspension or the ink to a working temperature in a range between 25 ° C and 50 ° C, so that when printing drops from the printable composition can be output at this working temperature.

According to a further preferred embodiment, the printing system is designed as a single-pass printing system, preferably designed as a single-pass printing system with a ram-operated printing module.

The invention is explained in more detail below on the basis of a preferred exemplary embodiment with reference to the accompanying drawings.

1 shows a schematic side view of a particularly preferred variant of the printing system according to the invention in cross section.

FIG. 2 shows a schematic view from below of the print head of the printing system from FIG

3A to 3F show schematic sketches of a very particularly preferred method according to the invention during the transport of print media through the printing system from FIGS. 1 and 2.

By way of introduction, it should be noted that in the figures, the same parts are provided with the same reference symbols or the same component designations, it being possible for the disclosures contained in the entire description to be transferred accordingly to the same parts with the same reference symbols or the same component designations.

FIG. 1 shows, in side view, the transport of ceramic printing media 101 from a conveyor 131 to a transport device 121 of a printing system 100 and the Transport of the print media 101 along a transport direction T into the effective area of a print head 103 of the printing system 100 and out of this again. The transport of the print media 101 takes place in the printing system 100 by means of an endless conveyor belt 123 of the transport device 121. The conveyor 131 transports ceramic print media 101 that were produced in a previous step by a pressing device and after one or more pretreatment stations passed through, for example for drying and / or for moistening with water and / or for applying engobe to the printing media 101 (not shown), which have a temperature of over 50 ° C. and are moistened with water.

The printing system 100 is designed as a single-pass inkjet printing system with ram-operated printing modules 107 for printing glaze suspensions in large quantities onto the ceramic printing media 101 (not shown). The print head 103 of this printing system 100 comprises ten print modules 107 operated by a ram, each with a nozzle plate 109 with nozzles 110 for dispensing drops of the glaze suspension. The ten print modules 107 are arranged one behind the other as seen in the transport direction T of the print media 101.

The printing system 100 is designed such that the print media 101 can be transported in a transport plane TE along the transport direction L, the nozzle front plate 105 of the print head 103, and in particular each nozzle plate 109, being arranged above the transport plane TE at a height X.

The transport device 121 of the printing system 100 comprises the endless conveyor belt 123 and also a cleaning unit 127 for removing drops of the glaze suspension (not shown) that have fallen on the endless conveyor belt 123 after cleaning the nozzle front plate 105, the endless conveyor belt 123 being continuously guided over two deflection rollers 125 during printing .

The print head 103 is described in detail in FIG. It comprises a nozzle front plate 105, the ten print modules (see “107” in Figure 1) each with a nozzle plate 109 and a frame plate 113, the side of the nozzle front plate 105 facing the print media 101, in particular with the nozzle plates 109 and one frame plate 113 lies in one plane (see Figure 1).

The cleaning device 114 in FIG. 2 is arranged laterally on the nozzle front plate 105 and is designed in such a way that it has several fluid flow configurations 111 (see FIGS. 3A-3E), each with several against the at least one part of the nozzle front plate 105 directed fluid flows can activate synchronously with the gap L between adjacent print media 101 in the transport direction T.

The method according to the invention to be carried out with the aid of the device according to the invention will now be described in detail below.

In the method, as explained above, print media 101 are first transferred from a press device (not shown) via conveyor 131 at a temperature of the print media 101 of over 50 ° C to the transport device 121 of the printing system 100 and then transported piece by piece along the transport direction T in such a way that the print media 101 are transported into and out of the effective area of the nozzle front plate 105.

The cleaning of the nozzle front plate 105 can be carried out at periodic time intervals, the respective interval duration being selected to be as short as necessary but as long as possible, in such a way that within the respective intervals a throughput of the print media 101 free of waste during the transport and printing of the print media 101 at least is ensured by the at least part of the effective area of the nozzle front plate 105, wherein a different, longer interval duration determined in comparison to the respective interval duration would have led to print media 101 with waste.

The time intervals to be selected are preferably adapted to different transport speeds and temperatures of the printing media 101 and also to different application quantities and temperatures of the glaze suspension or the ink in order to optimize the time intervals. It is important, however, that the time intervals are selected to be as long as possible, but short enough to prevent the drops of a liquid from dripping off the nozzle front plate 105. It is also important to start with short time intervals in order to avoid corresponding defects or at least to keep the nozzle front plate 105 under constant observation, so that a cleaning step is carried out in good time before it is detached if the formation of liquid continues.

There are different ways in which a person skilled in the art can arrive at optimized time intervals. For example, he can carry out a series of tests at a certain printing operation of the printing system 100 with different time intervals and thus check up to which time interval a still acceptable, ie sufficiently clean surface of the nozzle front plate 105 remains, with no detachment of liquid or dirt takes place from the nozzle front plate 105. The inventors have observed, for example, that when ceramic printing media 101, which are transported at a transport speed of 20 m / min at a printing media temperature of 80 ° C through the effective area of the nozzle front plate 105 of this printing system 100 and are coated with a selected glaze suspension with a water content of 30 wt % based on the total weight of the glaze suspension in application quantities of 1000g / m ² based on a full-surface application on the print media 101, the time intervals in which the nozzle front plate 105 has to be cleaned in order to obtain print media 101 printed without waste is about 2 minutes had to be chosen.

In the following, the individual steps of cleaning the nozzle front plate 105 will now be described again by way of example with reference to FIGS. 3A to 3F.

After a predetermined time interval has elapsed, a gap L is created between the next adjacent print media 101 on the conveyor 131 or at the latest when the print media 101 is transferred from the conveyor 131 to the transport device 121.

In the entry area of the printing system 100, when a trailing edge of a first printing medium 101 is led past a sensor (not shown), a counter of a counter is started, and when a leading edge of a further printing medium 101 is led past the sensor, another counter of the counter is started. If the distance between the first and the further print medium 101, 101 with or without starting the further counter of the counter, when a counter reading is reached which corresponds to the distance equivalent from the position of the sensor to the middle of the gap, the four nozzles are activated 115 of the first group of nozzles 114A of the cleaning device 114, specifically in such a way that the cleaning device 114 activates the fluid flow exclusively in the region of the gap L and synchronized with it. The nozzles 115 are designed as flat jet nozzles.

The four nozzles 115 of the first nozzle group 114A are connected via fluid lines 117 to an externally piloted 2/2-way process valve 119 (see FIG. 3A), which in turn is connected to a compressor for applying a certain pressure to the fluid (not shown).

The time interval between two valve actuations of the same nozzle group 114A is 2 minutes, the duration of the valve actuation for activating the fluid flows from the nozzles 115 of the nozzle group 114A being 1000 milliseconds. In this example, the flat jet nozzles are operated with a pressure of 2.5 bar and a fluid flow throughput of 20 liters / minute to 25 liters / minute per nozzle 115. The nozzle group 114A with 4 nozzles 115 is operated accordingly with a fluid flow throughput of a total of 80 liters / minute to 100 liters / minute. The cleaning device 114 comprises five nozzle groups 114A, 114B, 114C, 114D, 114E, which are each connected via fluid lines 117 to an externally piloted 2/2-way process valve 119 (see FIG. 2), which are connected to a compressor to act on the Fluids are connected to a certain pressure (not shown).

According to a preferred embodiment of the method, the time interval between two cleanings of the same part of the nozzle front plate 105 is in the range between 30 seconds and 5 minutes, in particular between 1 minute and 3 minutes, the duration of the cleaning being in the range between 100 milliseconds and 5 seconds, in particular in the range from 300 milliseconds to 1.4 seconds.

The following FIGS. 3B to 3F show further basic sketches of the particularly preferred method according to the invention during the transport of the print media 101 through the effective area of the nozzle front plate 105.

FIG. 3B reveals a point in time at which no fluid flow is activated, since upon activation of the same from a nozzle group 114A or 114B, drops of a liquid hanging down from the nozzle front plate 105 would be activated by the fluid flow not only in the area of the gap L, but also in the area of the Print media 101, which would become dirty as a result.

FIGS. 3C to 3F reveal different points in time during the progressive transport of the print media 101 through the effective area of the nozzle front plate 105, in which the cleaning device 114 activates fluid flows sequentially and synchronously with the gap L via the nozzles 115 of the respective nozzle groups 114B, 114C, 114D, 114E . With this procedure, at least that entire area of the nozzle front plate 105 to which the print media 101 are exposed during transport through the effective area of the nozzle front plate 105 was cleaned.

According to a further embodiment of the method not shown in the figures, printing media on which a glaze suspension has been applied with the printing system to produce a relief-like or full-surface decorative glaze can be transported from the printing system to another printing system in order to print a color image on the applied decorative glaze. The further printing system can be a completely ordinary inkjet printer for printing ceramic printing media with color ink. The distance between the two printing systems is chosen so that the glaze suspension can at least partially dry so that the colored ink does not mix with the applied glaze suspension. As an alternative or in addition to this, the printing media printed with the first printing system can be supplied with at least one suitable drying source, such as for example an IR source, are at least partially dried before they are printed with the further printing system. After the application of the colored ink to the relief-like or full-surface decorative glaze has been completed, the ceramic printing media printed in this way can be transferred to a kiln, fired in it and then cut to size if necessary.

Claims

Expectations:

1. A method for transporting print media (101) in pieces into the effective area of a print head (103) and out of this effective area again, as well as for cleaning at least a part of at least one nozzle front plate (105) provided on the print head (103), the method comprising the steps : a) Providing a printing system (100) comprising the print head (103) with the nozzle front plate (105), wherein the print head (103) comprises at least one print module (107) with at least one nozzle plate (109) from which drops of a printable composition are output b) transport of the print media (101) along a transport direction (T), in such a way that print media (101) are transported into and out of the effective area of the nozzle front plate (105), c) cleaning of at least one part of the Nozzle front plate (105) by means of one or more fluid flow configurations (111) from a fluid flow activating cleaning device (114), w if the fluid flow configurations (111) comprise at least one fluid flow directed against the at least part of the nozzle front plate (105), characterized in that the nozzle front plate (105) comprises the nozzle plate (109), with at least some of the print media (101) in the transport direction (T ) are transported at a distance to at least one of their nearest neighboring print media (101), as a result of which gaps (L) arise in the transport direction (T) between these spaced apart adjacent print media (101) and the cleaning device (114) does not necessarily always but exclusively in the area of the fluid flow Gaps (L) and activated synchronized with them.

2. The method according to claim 1, characterized in that at least that entire

Area of the nozzle front plate (105) to which the print media (101) are exposed during transport through the effective area of the nozzle front plate (105) is cleaned.

3. The method according to claim 1 or 2, characterized in that the printing media (101) are provided as ceramic printing media, in particular as unfired ceramic tiles and in a state moistened with water and at a temperature between 30 ° C and 120 ° C, preferably between 40 ° C and 100 ° C, particularly preferably between 50 ° C and 90 ° C are transported into the effective area of the nozzle front plate (105), the nozzle front plate (105) being heated to a temperature that is lower than the temperature of the print media (101) during the transport of the same through the effective area of the nozzle front plate (105), The nozzle front plate (105) and the print media (101) in the effective area of the nozzle front plate (105) are aligned relative to one another in such a way that drops form over time due to condensation of water vapor on the nozzle front plate (105) and continue to grow until they continue to grow due to gravity a certain time would either fall onto the print media (105) and / or would hang down from the nozzle faceplate (105) in such a way that they would be carried away by the print media (101).

4. The method according to at least one of the preceding claims, characterized in that the nozzle front plate (105) comprises the nozzle plate (109) and at least one frame plate (113), the side of the nozzle front plate (105) facing the print media (101) in particular with nozzle plate (109) and frame plate (113) lies in one plane.

5. The method according to at least one of the preceding claims, characterized in that the cleaning device (114) activates the fluid flow sequentially.

6. The method according to at least one of the preceding claims, characterized in that during the transport of the print media (101) through the effective area of the nozzle front plate (105) at least temporarily the cleaning of the at least part of the nozzle front plate (105) according to step (c) is accompanied.

7. The method according to at least one of the preceding claims, characterized in that the method comprises the step: d) printing the print media (101) by the at least one nozzle plate (109) of the at least one print module (107) drops of the printable composition, preferably one Dispenses ink or a glaze suspension.

8. The method according to claim 7, characterized in that during the transport of the print media (101) through the effective area of the nozzle front plate (105) at least temporarily simultaneously the printing according to step (d) and the cleaning of the at least part of the nozzle front plate (105) according to step (c) goes hand in hand.

9. The method according to at least one of the preceding claims, characterized in that the transport of the print media (101) takes place in a transport plane (TE) along the transport direction (T), the nozzle front plate (105) of the Print head (103) is arranged above the transport plane (TE), the transport according to step (b) and the cleaning according to step (c) at the same height (X), preferably at the same target height, between the nozzle front plate (105) and of the surface of the print media (101) in a direction perpendicular to a transport plane (TE) of the print media (101).

10. The method according to at least one of the preceding claims based on claim 9, characterized in that the transport according to step (b) and the cleaning according to step (c) and the printing according to step (d) at the same height (X), preferably at the same TARGET height take place.

11. The method according to claim 9 or 10, characterized in that the method comprises the step:

(g) Detection of an ACTUAL height by means of a sensor before the transport of the print media (101) into the effective area of the nozzle front plate (105),

(h) Setting the ACTUAL height by means of a positioning device of the printing system (100) if the recorded ACTUAL height does not correspond to the SET height.

12. The method according to at least one of the preceding claims, characterized in that in step (a) a single-pass inkjet printer is provided as the printing system (100), the transport of the print media (101) taking place at a constant speed in the transport direction (T) , and preferably at a speed of at least 3 m / min, particularly preferably at a speed of at least 12 m / min.

13. The method according to at least one of the preceding claims, characterized in that the fluid is a gaseous and / or liquid fluid, preferably a gas or gas mixture, particularly preferably air.

14. The method according to at least one of the preceding claims, characterized in that the fluid flow is emitted from one or more nozzles (115) of the cleaning device (114), wherein the nozzles (115) are preferably designed as flat jet nozzles.

15. The method according to at least one of claims related to claim 14, characterized in that the one nozzle (105) or the plurality of nozzles (115) of the cleaning device (114) are provided movably arranged in the transport direction (T), wherein during the cleaning according to step (c) the one nozzle (115) or the several nozzles (115) are moved in the transport direction (T), preferably synchronously with the gaps (L).

16. The method according to at least one of the preceding claims, characterized in that the cleaning takes place over a plurality of fluid flow configurations (111) with at least two fluid flows directed against one another and against the at least one part of the nozzle front plate (105).

17. The method according to at least one of the preceding claims based on claim 7 for the production of relief-like or full-surface decorative glazes on printing media (101), characterized in that the printing according to step (d) takes place by adding drops from the glaze suspension in application quantities of & 200 g / m ² to 1500 g / m ^z based on a full-area application to the print media (101), preferably based between £ 300 g / m ² to 1500 g / m ² are output on a full-area application to the print media (101).

18. The method according to at least one of the preceding claims based on claim 7, characterized in that the printing of the print media (101) with drops at a temperature in the range between 25 ° C and 50 ° C, preferably between 25 ° C and 45 ° C , particularly preferably between 30 ° C and 40 ° C tempered glaze suspension or ink takes place.

19. The method according to at least one of claims 14 to 18 based on claim 9, characterized in that in the method the printing system (100) with a transport device (121) for transporting the print media (101) in the transport plane (TE) along the transport direction (T ) is provided, wherein the nozzle front plate (105) of the print head (103) is arranged above the transport plane (TE) and the one or more nozzles (115) outside the at least part of the nozzle front plate (105) along the transport direction (T) and be arranged above the transport level (TE), and preferably mounted on the print head (103).

20. The method according to claim 19, characterized in that the transport device (121) is an endless belt conveyor, which preferably has a longitudinal direction and a transverse direction extending perpendicular thereto, which transverse direction is at least as wide as the effective area of the nozzle front plate (105), the endless belt conveyor particularly preferably a cleaning unit (127) is assigned to remove the drops caught on the endless conveyor belt.

21. The method according to at least one of claims 14 to 18 based on claim 9, characterized in that in the method the printing system (100) with a transport device (121) for transporting the print media (101) in the transport plane (TE) along the transport direction (T ) is provided, wherein the nozzle front plate (105) of the print head (103) is arranged above the transport plane (TE) and the one nozzle (115) or the several nozzles (115) inside or outside but below the transport plane (TE) on the transport device (121) are arranged along the transport direction (T).

22. The method according to claim 21, characterized in that the transport device (121) comprises a belt conveyor with at least two transversely to the transport direction (T) spaced apart and parallel belts, wherein the belts are driven synchronously.

23. The method according to at least one of claims 19 to 22, characterized in that the cleaning according to step (c) comprises the following steps:

- Providing a conveyor (131) and transporting the print media (101) with the conveyor (131) to the transport device (121) which is arranged downstream of the conveyor (131);

- Transferring the print media (101) from the conveyor (131) to the transport device (121);

- Creating a gap (L) between the next adjacent print media (101) before or during the transfer of the print media (101) from the conveyor (131) to the transport device (121).

24. The method according to at least one of the preceding claims, characterized in that the cleaning according to step (c) is carried out in periodic time intervals, the respective interval duration being selected as short as necessary but as long as possible, in such a way that one within the respective interval duration During the transport or the transport and printing of the print media (101), throughput of the print media (101) free of waste is ensured at least through the at least part of the effective area of the nozzle front plate (105), another higher interval duration being affected by waste compared to the respective interval duration Print media (101).

25. Printing system (100) comprising a. a transport device (121) for print media (101); b. at least one print head (103) with at least one nozzle front plate (105) provided on the print head (103), which print head (103) comprises at least one print module (107) with at least one nozzle plate (109) for dispensing drops of a printable composition; c. a cleaning device (114) that allows one against at least one

To activate part of the nozzle faceplate (105) directed fluid flow; characterized in that the nozzle front plate (105) comprises the nozzle plate (109), the cleaning device (114) being designed in such a way that one or more fluid flow configurations (111) with at least one fluid flow directed against the at least one part of the nozzle front plate (105) in sync with

Gaps (L) between adjacent print media (101) in the transport direction (T) can be activated.

26. Printing system (100) according to claim 25, characterized in that the cleaning device (114) comprises one or more nozzles (115) via which the fluid flow can be output, wherein the one or more nozzles (115)

Flat jet nozzles are.

27. Printing system (100) according to at least one of claims 24 or 26, characterized in that the printing system comprises a control device for performing at least one method according to at least one of claims 1 to 25.