EP3450179A1 - Direct printing machine and method for printing on containers by means of direct printing - Google Patents

Abstract

Direct printing machine (1) for printing on containers (2) with direct printing, with at least one stationary direct printing station (5 W, 5 C, 5 M, 5 Y, 5 K) with a direct printing head (50) for printing on the containers (2) Direct printing, an ink supply system (6) for supplying the direct print head (50) with printing ink (60a) from a storage tank (60), and with a conveyor (3) for transporting the container (2) at least a stationary direct printing station (5 W , 5 C, 5 M, 5 Y, 5 K), wherein the ink supply system (6) comprises a feed line (6 v) and / or a return line (6 r) for the printing ink (60a) to prevent ink flow from the storage tank (60 ) to the direct print head (50) and / or back, characterized in that the ink supply system (6) comprises at least one header tank (61a, 61b) arranged in the flow (6 v) and / or return (6 r) to provide a meniscus pressure of the Press in ink (60a) to the direct print head (50) and that between the at least one header tank (61a, 61b) and the direct print head (50) a valve island (62) is arranged to interrupt the flow of ink through the direct print head (50) and in parallel in a bypass line (62d) Direct print head (50).

Description

The invention relates to a direct printing machine and a direct printing method for printing on containers with a direct printing according to the features of the preamble of claim 1 and 13, respectively.

Typically, containers, such as beverage containers, are provided with a label in a labeling machine to mark and / or advertise the container contents.

Recently, however, there are increasingly used direct printing machines and methods, wherein the containers are provided instead of or in addition to the labels with a direct print on the inkjet principle. This makes it possible to individually print the containers in a container stream.

Such direct printing machines usually comprise at least one stationary direct printing station with a direct print head and a feed dog for transporting the containers past the at least one direct printing station. With the transporter, the containers are received, for example, in container receptacles and transported to the at least one stationary direct printing station. There, the containers are rotated by means of container receptacles and thereby printed with the direct print head from a plurality of printing nozzles with printing ink. The print nozzles are controlled so that the ink drops delivered to the container produce the desired print image. If a multicolored direct printing is desired, the containers are transported past several direct printing stations and printed there sequentially with printing inks of different colors. In addition, such direct printing machines include an ink supply system with a lead for the printing ink to produce an ink flow from a storage tank to the direct print head. For ink with a higher pigmentation, the ink supply system optionally includes a return for the printing ink to produce an ink flow from the direct print head back to the storage tank. As a result, the printing ink is kept in a continuous flow, so that particles in the printing ink can not settle.

The DE 10 2013 217 679 A1 discloses a printing machine for ink jet printing on containers, comprising at least one stationary printing unit for printing on the containers and a printing ink filling station associated with the printing unit.

The DE 10 2009 020 702 A1 discloses a printing system for printing on bottles, with a along a transport path for the container movable, working on the inkjet principle printhead for printing the respective arranged at a printing position container, as well as with a supply system of the printhead with ink. As the printhead moves with the bottle to be imprinted, it is proposed to divide the supply system into a static part and a moving part, the moving part having, in addition to the printhead, an auxiliary tank for the ink in order to ensure a high print quality.

The disadvantage here is that during maintenance of the direct print head or during startup, the supply and / or return of the ink supply system must be separated and it is time-consuming because of this, then restore a closed ink flow. In addition, no automatic flushing of the ink supply system or the direct print head is possible.

The object of the present invention is therefore to provide for a direct printing machine with at least one stationary direct printing station and a conveyor an ink supply system in which the production of a closed ink flow is simplified and an automated flushing of the ink supply system or the direct print head is possible. In addition, it is an object of the invention to reduce the number of ink pumps, without affecting the print quality.

To solve this problem, the invention provides a direct printing machine with the features of claim 1 ready. Advantageous embodiments of the invention are mentioned in the subclaims.

By virtue of the fact that the ink supply system comprises the at least one header tank arranged in the supply and / or return, a predefined meniscus pressure of the printing ink on the direct print head can be set precisely and the circulation can be controlled such that the print result has a particularly high quality.

Characterized in that the valve island is arranged between the at least one header tank and the direct print head, the flow of the printing ink can be selectively switched through the direct print head or via the bypass line. This makes it possible to rinse the ink supply system during maintenance or commissioning automatically with printing ink and to remove bubbles or foreign matter. In addition, it is possible to open the valves in the valve terminal intermittently and so a purge (impact cleaning) with increased pressure durzuführen. As a result, the direct print head can be cleaned particularly well, independently of further direct print heads connected to the ink supply system. For example, this allows the air and / or air bubbles are removed from the printing system.

Consequently, with the direct printing machine of the present invention, it is possible to achieve a high quality of direct printing at a lower ink supply cost.

The direct printing machine can be arranged in a beverage processing plant. The direct printing machine can be arranged downstream of a filling plant for filling a product into the containers and / or a capper for closing the containers with closures. However, the direct printing machine can also be connected upstream of the filling process and / or be connected directly downstream of a container production process. Detached from this, it can also be a direct printing press, which is not assigned to any system, but operates in so-called stand-alone mode.

The containers may be intended to contain drinks, toiletries, pastes, chemical, biological and / or pharmaceutical products. In general, the containers may be provided for any flowable or fillable media. The containers may be made of plastic, glass and / or metal, but also hybrid containers with material mixtures are conceivable. The containers may be bottles, cans, beverage containers and / or tubes. It is conceivable that the containers are shaped containers which deviate from rotational symmetry.

The feed dog may comprise a carousel and / or container receptacles arranged in a revolving manner with it. As a result, the containers can be transported in a predetermined pattern and rotated relative to the direct printing station during printing. The feed dog can be designed to transport the containers intermittently. In this case, the containers are each briefly stopped during printing with respect to the at least one stationary direct printing station and subsequently transported on. It is also conceivable that the feed dog is designed to transport the containers continuously, preferably if the containers are forming containers.

The at least one stationary direct printing station may comprise at least one further direct printing head, each with a further valve terminal and each with at least one further header tank. Preferably, a distributor unit can be arranged downstream of the storage tank in order to distribute the printing ink to the direct print head and to the at least one further direct print head, preferably via the header tank and the at least one further header tank and / or via the valve terminal and the at least one further valve terminal. As a result, the direct print heads from the same storage tank can be supplied with printing ink of one color. In other words, the stationary direct printing station may also comprise a plurality of the above-described direct print head or the direct print head according to claim 1, to simultaneously print the containers with a plurality of direct print heads, wherein the ink supply system is designed to supply the Direktuckköpfe from the storage tank, the ink supply system Distributor unit and starting therefrom for the direct-return heads each comprises a flow and a respective return for the printing ink to produce an ink flow from the storage tank to the direct print heads and back. By using the distribution unit between the at least one header tank and the direct print head, the ink supply system can supply a plurality of direct print heads. The use of cost-intensive ink pumps is thus reduced to a minimum. By using several direct print heads, the pressure range on the containers can be increased. Preferably, the ink supply system per direct print head each comprise at least one arranged in the supply and / or in the return headertank to adjust a meniscus pressure of the printing ink to the respective direct print head out, and arranged between each of the head tank and the direct print head valve terminal in the flow and in the return is to interrupt the flow of ink through the respective direct print head and make him in an associated bypass line parallel to the respective direct print head. The valve islands can each be individually switchable. As a result, the supply strands or the direct print heads can be flushed individually.

In addition, the header tank may optionally include a heater, whereby a better viscosity or a better ink temperature control can be done.

The direct print head can operate with a digital or ink jet printing process in which the ink is delivered to the containers by means of a plurality of printing nozzles. "Ink-jet printing process" here may mean that in chambers of a printing nozzle, a sudden increase in pressure via piezoelectric elements or thermocouples is generated such that a small amount of pressure fluid is forced through the pressure nozzle and discharged as a pressure drop to the container. The direct print head may each have a number of print nozzles in a range of 100 to 10,000, in particular in a range of 500 to 5000 nozzles. The pressure nozzles can be arranged in one or more rows of nozzles (for example 1 to 4), which are arranged in particular parallel to the container axis. The direct print head may include a feed port and / or a return port to allow the direct print head to print ink to be fed or discharged. The flow can be connected to the supply connection and the return can be connected to the return connection of the direct print head.

The direct printing machine may include a control unit for controlling the direct print head and / or the transporter, preferably arranged on the container receptacles and / or the ink supply system or work together with or be connected thereto. The control unit may comprise a CPU, a screen and / or an input unit.

The ink supply system may include an ink pump in the flow and / or the return, respectively, to establish the flow of ink. Preferably, the ink pump in the flow include a pressure relief valve to prevent pressure spikes in the flow. The ink supply system may include the dispensing unit to distribute the printing ink from the storage tank to the direct print head and one or more additional direct print heads. Preferably, the distribution unit in the flow and in the return each comprise a plurality of controllable switching valves to control the flow of ink to the respective direct printing heads out.

Preferably, the valve terminal may be arranged in the flow and / or in the return. It is also conceivable that the valve terminal is connected to a flow connection and / or return connection of the direct print head.

The valve terminal may include a switchable flow valve, a switchable return valve and a switchable lock-up valve in the bypass line. This can interrupt the flow and return of the direct print head and clear the bypass line to interrupt the flow of ink through the direct print head, making it parallel to the direct print head in the bypass line. As a result, a back pressure in the flow and / or in the return can be established for the purge. Subsequently, the flow and / or the return of the direct print head are released again by means of the valve terminal and the bypass line is interrupted so that the built-up dynamic pressure on the direct print head leads to increased output of the printing ink. As a result, the direct print head is cleaned particularly effectively. The flow valve and the return valve can be arranged in the flow or return. Preferably, the flow valve can be connected to the flow connection and the return valve to the return connection of the direct print head, in particular directly via ink lines.

At least one quick-release coupling may be disposed between the valve terminal and the direct print head to selectively connect the direct print head to the ink supply system or disconnect from it. As a result, the direct print head can be changed very easily and quickly. In addition, it is possible to interrupt the flow of ink through the valve terminal when changing the direct print head and make him over the bypass line parallel to the direct print head, so that the ink flow is not hindered by the change of the direct print head. Preferably, the at least one quick coupling can be arranged in the flow and / or in the return. In particular, each one quick coupling can be assigned to the flow connection or the return connection of the direct print head.

Between the valve terminal and the direct print head, a flow pressure sensor can be arranged in the flow and, optionally, a return flow pressure sensor can be arranged in the return flow in order to detect the meniscus pressure. As a result, the meniscus pressure can be detected by the aforementioned control unit and, as a result, the pressure in the at least one header tank can be regulated. Consequently, the meniscus pressure is set very accurately. Preferably, the flow pressure sensor and / or the return pressure sensor may be arranged immediately before or after the direct print head in the flow or return. This makes the measurement of the meniscal pressure particularly accurate.

The flow pressure sensor and optionally the return pressure sensor can be arranged between the respective quick coupling and the direct print head. As a result, the measurement of the meniscus pressure of pressure drops in the quick couplings remains unaffected and is therefore particularly accurate.

Between the valve terminal and the direct print head can be arranged in the flow a flow filter and optionally in the return a return filter for the printing ink to protect the print head from particles in the printing ink.

Preferably, the flow filter and optionally the return filter between the respective quick coupling and the direct print head may be arranged. This filters out the particles from the printing ink, which, for example, penetrate when opening and closing the quick couplings so that they can not get caught in the fine print nozzles of the direct print head.

The direct print head, the valve terminal and the at least one header tank can be designed to be movable with a common adjustment unit. As a result, the height between the head tank and the direct print head does not change due to an adjustment, so that the meniscus pressure is kept constant regardless of the travel of the direct print head. With the adjustment, it is possible, the position of the direct print head with respect to the containers to adapt, for example, when changing to another container type. The adjustment unit may comprise a linear motor in order to move the direct print head, the valve terminal and the at least one header tank preferably vertically.

In the flow can be arranged between the storage tank and the valve terminal a replaceable maintenance unit with an ink filter and a degassing, which is designed to be interchangeable in particular by means of quick couplings. As a result, particles, dissolved gases and gas bubbles in the printing ink are filtered out so that they are not conveyed to the direct print head by means of the ink supply system. By means of quick couplings, it is possible to exchange the maintenance unit very quickly. This results in a particularly low cost of maintenance.

The at least one header tank may be associated with a pneumatic unit to regulate the pressure of an air mailer in the at least one header tank, the pneumatic unit preferably comprising a piezo proportional valve. With the pressure of the air cushion in the at least one header tank, the meniscus pressure and the circulation can be regulated independently of a discharge pressure of the ink pump. Preferably, the storage tank is connected to the header tank by means of ink lines via the ink pump in the flow, the maintenance unit and / or the distribution unit, so that continuously or intermittently printing ink can be conveyed into the header tank. The pneumatic unit may include a proportional valve to an overpressure supply and / or a proportional valve to a vacuum supply to regulate the pressure of the air cushion in the headertank. Preferably, the pneumatic unit may comprise a collecting unit for refluxing printing ink from the direct printing head. As a result, the pneumatic unit is particularly well protected from the suction of printing ink from the at least one header tank at a negative pressure due to a malfunction.

The storage tank may include an agitator to prevent sedimentation of the printing ink. As a result, the liquid and the particle-like constituents of the printing ink in the storage tank are continuously mixed, so that a consistent consistency of the printing ink is ensured.

In addition, to solve the problem, the invention provides a direct printing method for printing on containers with a direct printing according to the features of claim 13.

The fact that the meniscus pressure of the printing ink is adjusted to the direct print head with the at least one arranged in the flow and / or return Headertank, he can be set so that the print result without the use of an additional ink pump has a particularly high quality.

The fact that the ink flow is interrupted via the direct print head with the valve terminal and is produced in the bypass line parallel to the direct print head, it is possible to automatically rinse the ink supply system with print ink during maintenance or commissioning and remove bubbles or foreign matter. In addition, it is possible to open the valves in the valve terminal intermittently and thus carry out a purge (impact cleaning) with increased pressure. As a result, the direct print head can be cleaned particularly well, independently of further direct print heads connected to the ink supply system. For example, this allows the air and / or air bubbles are removed from the printing system.

Consequently, with the direct printing method of the present invention, it is possible to achieve a high quality of direct printing at a lower ink supply cost.

The ink flow can preferably be produced via the direct print head with the valve island arranged between the at least one header tank and the direct print head, and the ink flow in the bypass line can be interrupted parallel to the direct print head for this purpose. This allows printing with the direct print head again in a normal printing operation.

In addition, the direct printing method may comprise the features described above with respect to the direct printing machine, preferably according to one of claims 1-12, individually or in any desired combinations. The direct printing method can be carried out with the direct printing machine described above, preferably according to one of claims 1-12.

Figur 1

ein erfindungsgemäßes Ausführungsbeispiel einer Direktdruckmaschine zur Bedruckung von Behältern mit einem Direktdruck in einer Übersichtsdarstellung von oben;

Figur 2

das Tintenversorgungssystem aus der Figur 1 als zirkulierende Variante in einer Diagrammansicht; und

Figur 3

eine weitere Ausführungsform des Tintenversorgungssystems aus der Figur 1 als nicht-zirkulierende Variante in einer Diagrammansicht.

Further features and advantages of the invention will be explained in more detail with reference to the embodiments described in the figures. Showing:

FIG. 1

an inventive embodiment of a direct printing machine for printing containers with a direct pressure in an overview from above;

FIG. 2

the ink supply system from the FIG. 1 as a circulating variant in a diagram view; and

FIG. 3

Another embodiment of the ink supply system of the FIG. 1 as non-circulating variant in a diagram view.

In the FIG. 1 an inventive embodiment of a direct printing machine 1 for printing containers 2 with a direct pressure is shown in an overview. It can be seen that the containers 2, coming for example from a filler and a capper, are fed to the feed dog 3 with the feed star 9.

At the conveyor 3, the container receptacles 4 are arranged, which are shown here only schematically. The container receptacles 4 may comprise, for example, a turntable and a centering bell in order to receive the container bottom or the mouth region of the respective container 2. The conveyor 3 is designed, for example, as a carousel and rotates about the axis A, so that the containers 2 are transported past in the container receptacles 4 in the transport direction T at the stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K.

Surrounding the feed dog 3, the stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K are arranged, each comprising three direct printing heads 50. However, it is also conceivable that the stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K each comprise only one, two or more than three direct printing heads 50. The stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K are designed for printing with printing inks of different colors, corresponding to the reference numerals 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K with white, cyan, magenta, Yellow and black. As a result, a multicolored direct print can be printed on the containers 2. The printing inks are preferably UV curable to allow a rapid drying process.

Furthermore, the feed dog 3 is designed for intermittent transport of the containers 2, wherein the container receivers 4 are respectively stopped at printing positions relative to the stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K. When printing the container 2 are rotated by means of the container receptacles 4 about their longitudinal axes and thereby printed by the direct print heads 50 according to the inkjet principle. It is also conceivable that the feed dog 3 is designed for a continuous transport of the containers 2, in particular when printing on shaped containers. In this case, the containers 2 with the container receptacles 4 are pivoted relative to the direct printing heads 50 at an angle such that the pressure interval varies as small as possible.

The direct printing heads 50 each have at least one row of nozzles with a multiplicity, for example 1000 printing nozzles, which are controlled by the control unit 8 so that individual ink droplets are dispensed onto the containers 2. The at least one row of nozzles is aligned substantially parallel to the container axes, so that via the rotation by means of the container receptacles 4, a flat direct pressure is generated.

After application of the direct pressure, the containers 2 are moved past the curing station 7 by means of the transporter 3 and the printing ink is cured by means of UV light. It is also conceivable that between the individual stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K further pinning stations are arranged to fix the individual colors.

Subsequently, the containers 2 are transported from the feed dog 3 to the outlet star 10 and fed to further processing stations, for example a packaging machine.

Furthermore, by way of example, the example of the print head 5 _Y in the FIG. 1 to see that the direct printing machine 1 comprises the ink supply system 6 for supplying the direct print heads 50 with printing ink from a storage tank. It is understood that a corresponding ink supply system is also attached to the stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _K.

The ink supply system 6 consists of a directly attached to the direct print heads 50 part 6a and a second part 6b with the storage tank. The two parts 6a, 6b are connected to each other via sections of the flow 6v and the return 6r.

Also visible is the control unit 8, with which the direct printing machine 1, in particular the feed dog 3, the container receptacles 4, the stationary direct printing stations 5 _W , 5 _C , 5 _M , 5 _Y , 5 _K , the ink supply system 6, the evaluation unit 7, the Inlet star 9 and the outlet star 10 are controlled.

The ink supply system 6 will be described below with reference to FIGS Figures 2 and 3 illustrated variants:
In the FIG. 2 is a circulating variant of the ink supply system 6 of the FIG. 1 shown as a diagram view. The ink supply system 6 is for supplying the direct print heads 50 from the FIG. 1 formed with printing ink 60a from the storage tank 60. In the FIG. 2 For the sake of clarity, from the distributor units 66v and 66r, only a single supply line to one of the direct print heads 50 is shown. It is understood that two corresponding supply lines are connected to the distribution units 66v, 66r with the other two direct print heads 50. In addition, the distribution units 66v and 66r may also be configured to distribute the printing ink to only two or more than three of the direct printing heads 50.

The storage tank 60, in which there is a supply of printing ink 60a, can be seen. The supply is constantly stirred with the agitator 60b to mix in from the return 6r back-flowing printing ink 60a and thus to ensure a high degree of homogeneity. In addition, this generally prevents settling of pigments from the printing ink 60a. About the lead 6v, the printing ink is removed from the storage tank 60 and conveyed by the flow ink pump 67a to the direct print heads 50 out. Parallel to the flow-in ink pump 67a is a pressure relief valve 67b to intercept pressure spikes.

Subsequent to the forward ink pump 67a, the replaceable maintenance unit 68 with the ink filter 68a and the degassing cartridge 68b, which can be separated from the ink flow by means of the quick-action couplings 68d, 68e and exchanged, is located in the supply line 6v. Particles are removed with the ink filter 68a and bubbles and / or dissolved gases are removed from the printing ink 60a with the degassing cartridge 68b. To remove the bubbles, the degassing cartridge 68b is connected to the vacuum supply 70b via the valve 68c. Preferably, the valve 68c is opened only when the precursor ink pump 67a conveys the printing ink 60a. As a result, the printing ink 60a is uniformly degassed.

Subsequently, the printing ink is distributed via the first distributor unit 66v to the direct printing heads 50, which are respectively supplied with printing ink via the connections 66.1v, 66.2v and 66.3v. For this purpose, a switching valve is provided per connection 66.1v, 66.2v, 66.3v in order to control the flow of ink.

After the distributor unit 66v, the printing ink with the supply line 6v is led via the feed header tank 61a, the valve island 62 to the direct print head 50 and from there with the return line 6r via the valve terminal 62, the return header tank 61b to the second distribution unit 66r.

With the second distribution unit 66r in the return line 6r, the return-flowing printing ink from the individual direct printing heads 50 is reconnected from the connections 66.1r, 66.2r or 66.3r and optionally conveyed back to the storage tank 60 via the return ink pump 71. Here too, a switching valve is provided per connection 66.1r, 66.2r, 66.3r in order to control the flow of ink.

The feed header tank 61a and the return header tank 61b serve to adjust the meniscus pressure and the circulation of the printing ink 60a through the direct print head 50. For this purpose, the first pneumatic unit 69a and the return header tank 61b, the second pneumatic unit 69b associated with the flow header tank 61a. They each include a pressure sensor to the To regulate pressure with two proportional valves of a compressed air supply 70a and a vacuum supply 70b so that in the respective header tank 61a, 61b, an air cushion with the desired pressure arises. As a result, a pressure differential is created between the supply header tank 61a and the return header tank 61b, whereby the circulation by the direct print head 50 can be controlled. The meniscus pressure is given by the average of the pressures in the flow and return header tanks 61a, 61b. Thus, the direct printing is printed with a particularly high quality.

In addition, the fill level sensors 61d are arranged on the flow header tank 61a and on the return header tank 61b, via which the fill levels are detected and regulated based thereon.

Further, the supply header tank 61a includes a heating unit 61c for bringing the printing ink to the desired temperature for optimum direct printing.

In addition, it can be seen that between the pneumatic units 69a, 69b and the two header tanks 61a, 61b there are respective catching units 69c, 69d for entrained printing ink. As a result, the pneumatic units 69a, 69b and the vacuum supply 70b are protected against entrained printing ink in the event of a fault.

It can also be seen that between the two header tanks 61a, 61b and the direct print head 50, the valve island 62 is arranged in the flow 6v and in the return 6r. For this purpose, the valve island 62 comprises a switchable flow valve 62a in the flow 6v, a switchable return valve 62b in the return 6r and a switchable bypass valve 62c in the bypass line 62d.

In addition, it can be seen that between the valve terminal 62 and the direct print head 50 in the flow 6v and return 6r in each case a quick coupling 63a, 63b is arranged to selectively connect the direct print head with the ink supply system 6 or decouple.

With the valve terminal 62 and the quick-release couplings 63a, 63b, it is possible to first interrupt the flow of ink through the direct print head 50 and to make it parallel to the direct print head 50 in the bypass line 62d. Consequently, therefore, the printing ink no longer flows through the direct print head 50 but via the bypass line 62d. At the same time, the quick couplings 63a, 63b can be released and the direct print head 50 exchanged for maintenance or replacement.

Conversely, after start-up of the new or maintained direct print head 50, the bypass valve 62c is closed again and the flow valve 62a and the return valve 62b are reopened to establish the flow of ink through the direct print head 50.

It is also possible with the valve island 62 to interrupt the flow of ink to the print head at a standstill of the direct printing machine 1 in order to use the time for purging the ink supply system 6.

Consequently, it is possible to automatically flush the ink supply system 6 with printing ink during the maintenance, startup or standstill of the direct printing machine 1 and to remove any bubbles or foreign matter. This achieves a particularly high print quality.

Further, the valve island 62 can be used to interrupt the flow of ink through the direct print head 50 for a pressure build-up by the header tanks 61a, 61b, so that subsequently a particularly effective purging of the print nozzles in the direct print head 50 under increased pressure.

In addition, it can be seen that between the valve terminal 62 and the direct print head 50 in the flow 6v, the flow pressure sensor 64a and in the return 6r, the return pressure sensor 64b are arranged. As a result, the pressure conditions are detected by the direct print head 50, and thus the meniscal pressure can be detected and adjusted particularly accurately. In addition, since the two pressure sensors 64a, 64b are respectively arranged between the quick-action coupling 63a, 63b and the direct-pressure head 50, pressure losses through the quick-action couplings 63a, 63b can not falsify the measurement result.

Further, a return filter 65a may be arranged between the valve island 62 and the direct print head 50 in the feed 6v and a return filter 65b for the printing ink 60a in the return 6r in order to protect the print head 50 from particles in the printing ink 60a. These are arranged, for example, between the respective quick coupling 63a, 63b and the direct print head 50.

In addition, it can be seen that the portion 6a of the ink supply system 6 attached to the direct print head 50 comprises the two header tanks 61a, 61b, the valve island 62, the quick connect couplings 63a, 63b, the feedforward filter 65a, the return filter 65b, the feed pressure sensor 64a, and the return pressure sensor 64b , and that the part 6a is designed to be movable together with the adjusting unit 51. As a result, the liquid level in the header tanks 61a, 61b does not change with respect to the direct print head 50, so that the printing ratios are not changed by the method of the direct print head 50.

The circulating variant of the ink supply 6 is particularly suitable for use of white printing ink with higher pigmentation, which otherwise tends to settle.

In the FIG. 3 is another embodiment of the ink supply system 6 of the FIG. 1 shown as a non-circulating variant in a diagram view. This indicates all previously in terms of the FIG. 2 However, the stirrer, the return ink pump, the switching valves in the second distribution unit 66r, the return header tank and the return pressure sensor on the direct print head 50 are omitted.

All other features apply accordingly. This makes the ink supply 6 even easier to construct and is particularly suitable for use with colored inks with less pigmentation. The return 6r remains in contrast to the previous embodiment in the FIG. 2 unused in regular printing operation. Only during startup is the filling of the ink supply system 6 with the printing ink 60a supported. It is also conceivable that the ink supply system 6 is emptied via the return 6r.

The in terms of the Figure 1-3 Direct printing machine 1 described and the ink supply system 6 are used in the regular printing operation as follows:
The containers 2 are transported with the conveyor 3 at the stationary direct printing stations 5w, 5c, 5 _M , 5 _Y , 5 _K , wherein the container 2 at the stationary direct printing stations 5w, 5 _C , 5 _M , 5 _Y , 5 _K each of three Direct print heads 50 are printed with a direct print.

The direct print heads 50 of a color are supplied from the storage tank 60 with printing ink 60a by means of the ink supply system 6, wherein an ink flow from the storage tank 60 to the direct print head 50 is established via the feed 6v of the ink supply system 6. In addition, in the embodiment in the FIG. 2 in regular printing operation via the return 6r an ink flow from the direct print head 50 back to the storage tank 60 made.

In this case, the meniscus pressure of the printing ink 60a to the direct printing head 50 with the header tanks 61a, 61b arranged in the front and optionally in the return 6v, 6r is adjusted such that a particularly high print quality is achieved.

In addition, the ink flow through the direct print head 50 at startup, maintenance, a standstill and a printhead change with the upstream and downstream 6v, 6r between the header tanks 61a, 61b and the direct print head 50 arranged valve island 62 interrupted and are made in the bypass line 62d in parallel to the direct print head 50.

As a result, the ink supply system 60 can be rinsed while the direct print head 50 is changed with as little loss of printing ink as possible.

Moreover, it is possible to interrupt the ink flow via the direct print head 50 by means of the valve island 62 in order to build up the pressure of the printing ink 60a with the two headertanks 61a, 61b for a subsequent purge.

It is understood that in the embodiments described above mentioned features are not limited to these combinations, but also individual or in any other combinations are possible.

Claims (13)

Direct printing machine (1) for printing on containers (2) with direct printing, with - At least one stationary direct printing station (5 _W , 5 _C , 5 _M , 5 _Y , 5 _K ) with a direct print head (50) for printing the container (2) with the direct pressure, - An ink supply system (6) for supplying the direct print head (50) with printing ink (60a) from a storage tank (60), and - with a conveyor (3) for transporting the containers (2) to at least one stationary direct printing station (5 _W , 5 _C , 5 _M , 5 _Y , 5 _K ), wherein the ink supply system (6) comprises a lead (6 _v ) and / or a return (6 _r ) for the printing ink (60 a) to produce an ink flow from the storage tank (60) to the direct print head (50) and / or back,
characterized in that
the ink supply system (6) comprises at least one head tank (61a, 61b) arranged in the feed (6 _v ) and / or return (6 _r ) for setting a meniscus pressure of the printing ink (60a) toward the direct print head (50), and
in that a valve island (62) is arranged between the at least one header tank (61a, 61b) and the direct print head (50) in order to interrupt the flow of ink via the direct print head (50) and in parallel in a bypass line (62d) to the direct print head (50 ). Direct printing machine (1) according to claim 1, wherein the valve island (62) has a switchable flow valve (62a) in the supply line (6 _v ) and / or a switchable return valve (62b) in the return line (6 _r ) and / or a switchable bypass valve (62c) in the bypass line (62d). A direct printing machine (1) according to claim 1 or 2, wherein at least one quick connector (63a, 63b) is disposed between the valve terminal (62) and the direct print head (50) to selectively connect the direct print head (50) to the ink supply system (6) disconnect from it. Direct printing machine (1) according to one of the preceding claims, wherein between the valve terminal (62) and the direct print head (50) in the flow (6 _v ) a flow pressure sensor (64a) and optionally in the return (6 _r ) a return pressure sensor (64b) are arranged, to capture the meniscal pressure. A direct printing machine (1) according to claims 3 and 4, wherein the flow pressure sensor (64a) and optionally the return pressure sensor (64b) are disposed between the respective quick coupler (63a, 63b) and the direct print head (50). Direct printing machine (1) according to one of the preceding claims, wherein between the valve terminal (62) and the direct print head (50) in the flow (6 _v ) a flow filter (65a) and optionally in the return (6 _r ) a return filter (65b) for the printing ink (60a) are arranged to protect the printhead (50) from particles in the printing ink (60a). Direct printing machine (1) according to claim 3 and 6, wherein the flow filter (65a) and optionally the return filter (65b) between the respective quick coupling (63a, 63b) and the direct print head (50) are arranged. Direct printing machine (1) according to one of the preceding claims, wherein the direct print head (50), the valve terminal (62) and the at least one head tank (61a, 61b) are designed to be movable with a common adjustment unit (51). Direct printing machine (1) according to one of the preceding claims, wherein a replaceable maintenance unit (68) with an ink filter (68a) and a degassing cartridge (68b) is arranged in the supply line (6 _v ) between the storage tank (60) and the valve terminal (62), in particular by means of quick couplings (68d, 68e) is designed exchangeable. A direct printing machine (1) according to any one of the preceding claims, wherein the at least one header tank (61a, 61b) is associated with a pneumatic unit (69a, 69b) to regulate the pressure of an air mailer in the at least one header tank (61a, 61b) the pneumatic unit (69a, 69b) preferably comprises a piezo-proportional valve. Direct printing machine (1) according to one of the preceding claims, wherein the storage tank (60) for preventing sedimentation of the printing ink (60a) comprises a stirrer (60b). Direct printing machine (1) according to one of the preceding claims, wherein the at least one stationary direct printing station (5 _W , 5 _C , 5 _M , 5 _Y , 5 _K ) comprises at least one further direct print head with at least one further valve terminal and with at least one further header tank, and wherein after the storage tank, a distribution unit (66 _v ) is arranged to distribute the printing ink (60 a) on the direct print head (50) and the at least one further direct print head. Direct printing method for printing on containers (2) with direct printing, wherein the containers (2) are transported past a conveyor (3) at at least one stationary direct printing station (5 _W , 5 _C , 5 _M , 5 _Y , 5 _K ), wherein the Container (2) at the at least one stationary direct printing station (5 _W , 5 _C , 5 _M , 5 _Y , 5 _K ) are printed by a direct print head (50) with the direct print, wherein the direct print head (50) by means of an ink supply system (6) from a storage tank (60) with printing ink (60a) is supplied, via a flow (6 _v ) and / or a return (6 _r ) of the ink supply system (6) an ink flow from the storage tank (60) to the direct print head (50) and / or back is made,
characterized in that
a meniscus pressure of the printing ink (60a) is set towards the direct printing head (50) with at least one head tank (61a, 61b) arranged in the feed (6 _v ) and / or return (6 _r ), and
that the ink flow via the direct print head (50) with a in the flow (6 _v ) and / or in the return (6 _r ) between the at least one header tank (61 a, 61 b) and the direct print head (50) arranged valve island (62) interrupted and in a bridging line (62d) parallel to the direct print head (50).

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