WO2013170888A1

WO2013170888A1 - An inkjet printing machine and a corresponding printing method

Info

Publication number: WO2013170888A1
Application number: PCT/EP2012/059045
Authority: WO
Inventors: Bertrand WICHT; Eric CHARLOT; Olivier SAVARY; Stéphane RUMO; Daniel WIDER
Original assignee: Polytype S.A.
Priority date: 2012-05-15
Filing date: 2012-05-15
Publication date: 2013-11-21

Abstract

The present invention relates to an inkjet printing machine (1), in particular for printing onto three-dimensional objects (2.1, 2.2, 2.3,…), comprising a first printing object inputting means (3) for inputting three-dimensional objects (2.1, 2.2, 2.3,…) into the machine (1), a printing object transferring means (4) for transferring three-dimensional objects (2.1, 2.2, 2.3,…) from the printing object inputting means (3) to a printing object conveying means (5), the printing object conveying means (5) conveying the three-dimensional objects (2.1, 2.2, 2.3,…) during the printing in the machine (1), at least one printing head (6.1, 6.2, 6.3,…) for applying ink onto the three-dimensional objects (2.1, 2.2, 2.3,- …), and a printing object outputting means (7) for outputting three-dimensional objects (2.1, 2.2, 2.3,…) from the machine (1), wherein the inkjet printing machine (1) further comprises at least one movable printing object supporting means (8.1, 8.2, 8.3,…) for supporting and displacing three-dimensional objects (2.1, 2.2, 2.3,…) with respect to the at least one printing head (6.1, 6.2, 6.3,…).

Description

An Inkjet Printing Machine and

a Corresponding Printing Method

Technical Field of the Invention

The present invention relates in general to the technical field of inkjet printers. More in particular, the present invention relates to an inkjet printing machine, in particular for printing onto three-dimensional objects, comprising a printing object inputting means for inputting three-dimensional objects into the machine, a printing object transferring means for transferring three- dimensional objects from the printing object inputting means to a printing object conveying means, the printing object conveying means conveying the three- dimensional objects until the printing position in the machine, at least one printing head for applying ink onto the three-dimensional objects, and a printing object outputting means for outputting three-dimensional objects from the machine. Moreover, the present invention relates to a corresponding printing method.

State of the Art

Inkjet printing machines have been used ever since the 1950's. In general, an inkjet printing machine uses droplets if ink in order to propel them onto paper, wood, plastic or other synthetic material, or any other appropriate printing support.

In terms of methods for creating and propelling droplets in an inkjet printer machine, two different inkjet technologies exist: the so called continuous inkjet method (CIJ) which is commonly used for marking and coding of products and packages and a droplet-on-demand method (DOD). In the continuous inkjet technology, liquid ink is pressed by means of a high-pressure pump from a reservoir through a very small nozzle, creating thereby a continuous stream of ink droplets. A vibrating piezoelectric crystal causes this continuous stream to break into droplets at regular intervals. These ink droplets are then subjected to a variable electrostatic field, charging each individual ink droplet in a particu- lar way. The droplets charged in this way are then deflected by means of electrostatic plates to print on the substrate.

When the droplet-on-demand method is used, ink droplets are produced only if they are needed. The droplet production can thereby be thermal (in which case a printing head contains a series of tiny chambers with heaters, and a current is passed through the heating element causing a quick vaporization of the ink in the chamber to form a bubble, provoking a pressure increase, which propels a droplet of ink onto the substrate) or piezoelectric (where a piezoelectric element is subjected to a voltage in order to change its shape, which generates a pressure pulse in the fluid forcing a droplet of ink from the nozzle).

In general terms, CMYK color model is used in inkjet printing machines. This color model is based on four differently colored inks (cyan, magenta, yellow and black). This is a subtractive model and works basically by masking colors on a lighter background. By applying an ink on the substrate, its properties are being changed and therefore the amount of light that would otherwise be reflected is reduced. In line with this principle, inkjet printing machines generally have four printing heads (one for each of the mentioned colors). Typically, these four heads are mounted side-by-side, aligned, such that printing different colors can be performed in a single passage without any adjustment of the substrate.

A "fifth" head is sometimes used, corresponding to a UV-light emitter. In actual facts, many inks used in professional inkjet printing machines can be fixed (or cured) using ultraviolet light. Such inks consist mainly of acrylic monomers which can be cured by exposing them to strong ultraviolet light. Thereby, the printed surface can be used immediately after being printed, which can reduce considerably the manufacturing process of the printed products.

Among other applications, inkjet printing machines are also commonly used for printing onto packaging containers made of diverse plastic materials (e.g. polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) or others). While some of these package containers exclusively have flat surfac- es, others have more irregular shapes, including oval or circular surfaces and/or rounded edges. Inkjet printing on such containers or any other three- dimensional objects with non-flat surfaces is very difficult with current printing machines.

Disclosure of the Invention

The object of the present invention, therefore, is to provide an inkjet printing machine and a corresponding printing method which enable a simple, efficient, and cost-effective inkjet printing on three-dimensional objects, in particular those which have non-flat surfaces.

The above object is in particular achieved by the invention as set out in the accompanying claims 1 and 8.

More specifically, the above objet is in particular achieved by the invention by means of an inkjet printing machine, in particular for printing onto three-dimensional objects, comprising a printing object inputting means for inputting three-dimensional objects into the machine, a first printing object transferring means for transferring three-dimensional objects from the printing object inputting means to a printing object conveying means, the printing object conveying means conveying the three-dimensional objects until the printing position in the machine, at least one printing head for applying ink onto the three- dimensional objects, and a printing object outputting means for outputting three-dimensional objects from the machine, wherein the inkjet printing machine further comprises at least one movable printing object supporting means for supporting and displacing three-dimensional objects with respect to the at least one printing head.

The advantage of the present invention resides among other things in the fact that the printing machine according to the present invention comprises at least one movable printing object supporting means which supports and displaces three-dimensional objects with respect to the at least one printing head, such that ink can be applied to the surface of the three-dimensional objects by means of the printing head. In such a way, the printing head can remain immobile, while the three-dimensional object (e.g. a food container) to be printed onto is being displaced and put into position for printing. Thanks to this arrangement, the positioning of the three-dimensional object with respect to the printing head and, therefore, the printing precision can be improved significantly. In particular, three-dimensional objects having non-flat surfaces (e.g. oval or circular surfaces) and/or rounded edges can be printed in a very accurate way. Furthermore, the printing speed can be increased since the three- dimensional objects to be printed can be moved in front of the printing head in a very quick way.

In a preferred embodiment of the present invention, the inkjet printing machine further comprises a pre-treatment means for pre-treating the three- dimensional objects prior to applying ink onto them. The pre-treatment means can in particular be interposed between the printing object inputting means and the first printing object transfer means. It is however also possible to install the pre-treatment means onto other positions in the inkjet printing machine according to the invention. The pre-treatment can in particular comprise any combination of chemical, mechanical or chemical treatment of the three-dimensional objects. The advantage of this embodiment of the present invention lies in particular in the fact that the pre-treatment of the printing objects allows for a better printing quality.

In another preferred embodiment of the present invention, the inkjet printing machine further comprises a second printing object transferring means for transferring three-dimensional objects from the printing position to the printing object outputting means. Thanks to such a solution, the printed objects can be easily removed from the printing object and then transferred to the outputting means, without need for further operation of the supporting means. In this way, the printing object supporting means can be liberated and reused immediately after the printing process of one object has been accomplished. Therefore, the printing speed can be increased, without any quality losses.

Preferably, the inkjet printing machine comprises instead of a single printing head a printing module with four printing heads, wherein the module comprises one of the printing heads for the colors cyan, magenta, yellow and black, respectively. The advantage of this embodiment of the present invention resides, inter alia, in the fact that it allows for the classical CMYK color system printing to be used in an improved way. In this embodiment, the printing object supporting means displaces the three-dimensional object in front of the module having four different printing heads. Therefore, four different colors can be applied to the surface of the three-dimensional object in one single step. Thanks to this feature, the speed of the printing process can be further increased.

More preferably, the inkjet printing machine further comprises a bottom printing head for printing onto the bottom surface of the three-dimensional objects. Of course, this bottom printing head can be replaced by a bottom printing station comprising more than one printing head, e.g. four printing heads for the colors cyan, magenta, yellow and black. Thanks to this arrangement of the printing heads, side surfaces of the three-dimensional objects can be printed in a first step, while the bottom surface can then be printed in another printing position by another printing system. Again, this principle allows for a better printing quality and a higher printing speed.

In a further embodiment of the present invention, the inkjet printing machine comprises an UV-head for pinning the ink on the three-dimensional objects and/or an UV-station for curing the ink on the three-dimensional objects. In particular, an UV-head can be integrated into the printing module (e.g. as a fifth printing head), such that the pinning of ink can be performed immediately after it has been applied to the surface of the objects. However, such a head can also be placed on a different place within the machine. As to the UV- station, it can be installed on any place between the printing position and the exiting position of the objects. The advantage of the UV-head and of the UV- station is that the ink can be pinned and/or cured on the surface of the objects prior to outputting the printed objects from the machine.

In another embodiment of the present invention, a rotation driving means is foreseen for rotating the printing object supporting means around its rotational axis. The advantage of such a solution is that all side surfaces of the printing objects can be placed successively in front of the printing heads. Mo- reover, a rotational movement of the support means allows the smooth edges of the printing objects to be moved in front of the printing heads which allows for a direct printing (printing in only one move of the object) onto these edges.

In a further preferred embodiment of the present invention, at least two linear driving means are foreseen for displacing the printing object supporting means in two different directions. This embodiment has the advantage, inter alia, that the printing object supporting means can be further moved in order to align with the printing head. Together with the rotational movement as mentioned above, the printing head can be completely immobile while the printing object can make all necessary movements in order to realize the printing. The speed and the accuracy of the printing process can thus be further increased.

Moreover, in a preferred embodiment of the present invention, the printing object conveying means is arranged for moving in a discrete way such that it makes a predetermined displacement at regular time intervals. This embodiment has the advantage, among other things, that the displacement of the printing objects can be controlled in a very efficient way. Since the displacement of the conveying means and thus the position of each three-dimensional object is always well defined, the whole printing process can be further optimized.

Finally, the printing machine can also comprise at least one block of four printing modules which are positioned in line with each other. Thanks to this solution, the printing of the three-dimensional objects can also be realized in a "classical" way, i.e. with a parallel movement of the object with respect to the printing heads. Moreover, various groups of printing modules (blocks) can be arranged in parallel to each other, which allows for a parallel printing of different three-dimensional objects. Together with the indexed conveying means and the corresponding printing object supporting means, the printing process can further be optimized.

At this place, it is important to point out that the present invention does not only relate to an inkjet printing machine as explained above, but also to a corresponding inkjet printing method.

Short Description of the Drawings

The invention will now be described more in detail with reference to the accompanying drawings, in which:

Figure 1 shows a schematic perspective view of the inkjet printing machine according to the present invention.

Figure 2 shows a schematic perspective view of the container supporting means and the printing module with the different printing heads.

Figure 3 shows a schematic view from the side of the container supporting means and the printing module.

Figures 4a and 4b show schematically two different printing methods for the three-dimensional objects; Figure 4a showing the method using different passages in front of the printing module and Figure 4b showing the method using one single passage in front of the printing module.

Figure 5 shows a schematic representation of three different loading schemes for the indexing belt system used as printing object conveying means.

Detailed Description of the Preferred Modes

The following figures are intended as an aid to understanding the invention, and are not intended to imply any limitation of the scope of the invention or protection. Where the same reference signs are used in different drawings, these reference signs are intended to refer to the same or corresponding features. Figure 1 illustrates one embodiment of the inkjet printing machine 1 according to the present invention in a schematic perspective view. In figure 1 , the most important elements of the inkjet printing machine 1 according to the present invention are represented in a schematic way. It is therefore clear to any person skilled in the art that the illustrated elements can also be realized differently, without departing from the general scope of the invention.

The three-dimensional objects 2.1 , 2.2, 2.3,... to be printed onto, for example containers made of synthetic material which are used for different food articles such as yogurt, fresh cheese or butter, can be loaded into a printing object inputting means 3 of the machine 1 manually or automatically. To this end, a loading means (not illustrated) can be used in a known way. It is in particular also possible to connect the printing object inputting means 3 of the inkjet printing machine 1 directly to a manufacturing machine for three-dimensional objects 2.1 , 2.2, 2.3,... such that objects 2.1 , 2.2, 2.3,... which exit the manufacturing machine are directly loaded into the inputting means 3 of the machine 1 . Of course, any other loading method of the three-dimensional objects 2.1 , 2.2, 2.3,... into the inkjet printing machine 1 can be used.

After the three-dimensional objects 2.1 , 2.2, 2.3,... to be printed onto have been loaded into the inkjet printing machine 1 , they can be pre-treated by the pre-treatment means 9 prior to having ink applied onto them. This pre-trea- ting of the three-dimensional objects 2.1 , 2.2, 2.3,... can in particular comprise a gas pretreatment, in other words a treatment of the three-dimensional objects 2.1 ,2.2,2.3,... with a flame. This flame increases the surface tension of the three-dimensional objects 2.1 ,2.2, 2.3,... which results in a better adhesion of the ink on the surface. Of course, any other kind of pre-treatment (such as corona pre-treatment or plasma pre-treatment) can of course be used. Furthermore, it is generally possible to place the pre-treatment means 9 at any position within the inkjet printing machine 1 prior to the printing position of the three-dimensional objects 2.1 , 2.2, 2.3,....

Following this pre-treatment, a first printing object transferring means 4 is used to transfer the three-dimensional objects 2.1 , 2.2, 2.3,... from the printing object inputting means 3 to a printing object conveying means 5. This first transferring means 4 can in particular be any kind of in-feed conveyor and/or of a screw feeder assembly. However, other known means can also be used. An important property of this first printing object transferring means 4 is that it is capable of collecting the three-dimensional objects 2.1 , 2.2, 2.3,... one-by-one in the printing object inputting means 3 and of transferring these three- dimensional objects 2.1 , 2.2, 2.3,... in an organized way to the printing object conveying means 5 which is then further transporting the three-dimensional objects 2.1 , 2.2, 2.3,... until the printing position within the machine 1 .

It would of course also be possible to integrate the above-mentioned pre-treatment means 9 into the first transferring means 4 such that the three-dimensional objects 2.1 , 2.2, 2.3,... are pre-treated during their transfer from the inputting means 3 to the conveying means 5. The pre-treatment means 9 can in particular comprise a grapping means for taking a three-dimensional object

2.1 , 2.2, 2.3,... from the first transporting means 4, transporting this object 2.1 ,

2.2, 2.3,... to the pre-treatment position, and bringing the object 2.1 , 2.2, 2.3,... back onto the first transporting means 4 after the pre-treatment operation.

For the sake of completeness, we would like to mention that the pre- treatment means 9 can comprise various elements, for example one separate pre-treatment mechanism for pre-treating side walls of the three-dimensional objects 2.1 , 2.2, 2.3,... and another pre-treatment mechanism for pre-treating bottoms of the three-dimensional objects 2.1 , 2.2, 2.3,.... In any way, a person skilled in the art will be aware of these different possibilities.

From there, the three-dimensional objects 2.1 , 2.2, 2.3,... are further conveyed by the printing object conveying means 5 until the printing position in the machine 1 . This printing object conveying means 5 can in particular be realized as an indexing in-feed belt, having for example integrated vacuum stations for maintaining the three-dimensional objects 2.1 , 2.2, 2.3,... in place during their conveying through the machine 1 . Of course, any other suitable means for maintaining the three-dimensional objects 2.1 , 2.2, 2.3,... in place can also be used. Once the three-dimensional objects 2.1 , 2.2, 2.3,... have reached their printing positions, they are unloaded from the printing object conveying means 5 and positioned on the respective movable printing object supporting means 8.1 , 8.2, 8.3,.... Each one of these movable printing object supporting means 8.1 , 8.2, 8.3,... is foreseen for supporting and displacing the three-dimensional objects 2.1 , 2.2, 2.3,... during the printing process itself, i.e. with respect to the respective printing heads 6.1 ,6.2,6.3,.... In other words, the printing process in the inkjet printing machine 1 according to the present invention is characterized by unmovable (or mainly unmovable) printing heads 6.1 ,6.2, 6.3,... and three-dimensional objects 2.1 , 2.2, 2.3,... which are being moved with respect to the printing heads 6.1 , 6.2, 6.3,... by means of the printing object supporting means 8.1 ,8.2,8.3,....

In particular, as can be seen in Figures 2 and 3, each printing object supporting means 8.1 , 8.2, 8.3,... can comprise a rotation driving means RM for rotating the printing object supporting means 8.1 , 8.2, 8.3,... around a rotational axis A. Generally, the rotational axis A can coincide with a symmetry axis of the three-dimensional objects 2.1 ,2.2,2.3,..., but it is clear to any skilled person that any other appropriate rotational axis can be used instead. Thus, this invention is not limited to this particular embodiment.

Moreover, the inkjet printing machine 1 according to the invention can also comprise one or more linear driving means (for example two linear driving means TM1 and TM2) for displacing each of the printing object supporting means 8.1 , 8.2, 8.3,... in different linear directions. As illustrated in Figure 2, if two different linear directions are used, they can preferably be perpendicular to each other, but it is obvious that any other combination of directions can be used.

In a particular embodiment (and as illustrated in Figure 2), each one of the printing object supporting means 8.1 ,8.2,8.3,... can comprise fully independently driven linear driving means TM1 ,TM2. However, it is imaginable to combine linear driving means of the different printing object supporting means 8.1 ,8.2,8.3,... in order to simplify their command. As an example, different horizontal linear driving means (called TM1 in Figure 2) could be interconnected such that different printing object supporting means 8.1 ,8.2,8.3,... can make exactly the same linear displacement at the same time. This embodiment can considerably reduce the command complexity and allow for a further increase in printing accuracy and efficiency.

Thanks to these rotation driving means RM and the linear driving means TM1 ,TM2, each printing object supporting means 8.1 ,8.2,8.3,... (and therefore also the three-dimensional objects 2.1 ,2.2,2.3,... which are supported by the printing object supporting means 8.1 ,8.2,8.3,...) can very easily be moved in different directions and with respect to the printing heads 6.1 ,6.2,6.3, ... which can, if necessary, remain immobile during the printing process.

Figures 4A and 4B show two different printing methods which can be used with the inkjet printing machine 1 according to the present invention. Obviously, other printing methods can also be used; however, these two printing methods, together with the above-mentioned system in which the printing objects are moved with respect to immobile printing heads offer the biggest advantages.

The first printing method comprises four roll-offs, whereas only one color is printed onto the printing object at a time. In other words, a first color is printed by means of a first printing head 6.1 during the first roll-off. For this displacement, the rotation driving means RM is generally used together with the linear driving means TM1 , TM2. In case of perfectly symmetrical objects, it is however possible to simplify this displacement and to use only the rotation driving means RM. Then, the three-dimensional printing object 2.1 is moved (by means of the linear driving means TM1 ,TM2) to another printing head 6.2 with another color and the second color is applied onto the surface of the object 2.1 in the same manner as described above.

The advantage of this first printing method is the possibility to create a fully flexible printing method. In actual fact, instead of four "classical" printing heads 6.1 ,6.2,6.3,6.4 (cyan, magenta, yellow and black), it is possible to use a further printing head (not represented), i.e. printing white color. In this way, the white ground layer could for example be printed onto transparent objects prior to applying the "regular" printing pattern. Of course, other combinations of colors are also possible.

When all four colors have been applied onto the object 2.1 , this object can be transferred to a UV-chamber (not illustrated) for curing. A possible alternative is adding a fifth roll-off below a fifth "printing head" 6.0 which comprises a UV-LED (or another appropriate source of UV radiation) for freezing the inks very quickly after they have been printed in order to improve the print quality. This quick pinning can be used or not depending on the ink features. The time between the printing and the curing of the ink is generally a very important factor for the printing process, since it plays an essential role in increasing the print quality. Therefore, using a fifth "printing head" and pinning (or pre-curing) the ink immediately after the ink has been applied onto the surface of the object 2.1 can increase the printing quality dramatically. At this place, we need to add that, after this intermediate pinning step has been performed, the printed object 2.1 can nevertheless be transferred to a UV-chamber for the final curing.

The second printing method, illustrated in Figure 4B uses a different approach and is generally based on linear trajectories.

In this case, the four colors are first printed simultaneously on one side during one passing of the three-dimensional object 2.1 in front of the printing head module 6. In other words, each printing head 6.1 ,6.2,6.3,... applies ink on the three-dimensional object 2.1 at the same time, but thanks to the necessary physical distance between the printing heads 6.1 ,6.2,6.3,... , each ink can be applied on the object 2.1 independently. Obviously, this movement requires use of the linear driving means TM1 ,TM2. Then, the printing object 2.1 is rotated (in this embodiment, a rotation by 45° is illustrated, but the concrete rotation angle can vary as a function of the object shape) in order to print the corner of the object 2.1 . This procedure is continued until ink has been applied onto all side walls and corners of the three-dimensional object 2.1 .

Also in this case, it is imaginable to add a UV-LED as a fifth "printing head" and to use it for freezing the inks directly after the print. It is to be noted at this place that the printing heads 6.1 ,6.2,6.3,... in general do not move during the printing process. It is however also imaginable to have printing heads 6.1 ,6.2,6.3,... which are also capable of making displacements, if necessary. Specifically, as illustrated in Figure 3, the support 61 of the printing heads 6.1 ,6.2,6.3,... can be moved in order to adapt the position of the printing heads 6.1 ,6.2,6.3,... (for example to align them) with respect to the side walls of the three-dimensional objects 2.1 ,2.2,2.3,.... Evidently, it is also thinkable to add another driving means for the printing object supporting means 8.1 ,8.2,8.3,... which can allow for changing the orientation of the rotational axis A (for example to the position illustrated as A'). In this way, the speed of the printing process can be further increased.

After the applying and curing of the ink onto the side walls (and corners) of the three-dimensional objects 2.1 ,2.2,2.3,... have been completed, the bottom side of the objects 2.1 ,2.2,2.3,... can also be printed. Obviously, it can also be arranged for a previous printing onto the bottom surface and a person skilled in the art will understand how the machine 1 could be adapted accordingly. Also, the printing of the bottom surface of the three-dimensional objects 2.1 ,2.2,2.3,... can be performed while the three-dimensional objects 2.1 ,2.2, 2.3,... are supported by the printing object supporting means 8.1 ,8.2,8.3,... (as when the side walls and corners are printed onto), but it is also possible to implement this part of the printing process in a completely different way.

Once all surfaces of the three-dimensional objects 2.1 ,2.2,2.3,... are printed, they are taken by a second printing object transferring means 10 which transfers them from the printing position to the printing object outputting means 7. Again, this second transferring means 7 can be any kind of in-feed conveyor and/or of a screw feeder assembly. However, other known means can also be used. If the three-dimensional objects 2.1 ,2.2,2.3,... have reached the printing object outputting means 7, they can be unloaded from the machine 1 in any suitable way.

It is important to point out that unloading of the three-dimensional objects 2.1 , 2.2, 2.3,... from the printing object conveying means 5 and their positioning on the movable printing object supporting means 8.1 , 8.2, 8.3,... can in a preferred embodiment be performed simultaneously with the unloading of the three-dimensional objects 2.1 , 2.2, 2.3,... from the movable printing object supporting means 8.1 , 8.2, 8.3, ... and their loading onto the second printing object transferring means 10. In this way, the printing efficiency and speed can again be further increased.

Coming back to the printing object conveying means 5, it is to note that the indexing belt system works in the way that the displacement of the three-dimensional objects 2.1 , 2.2, 2.3,... follows a pre-determined scheme. The movement of the conveying means 5 is discrete, i.e. each displacement is followed by a phase in which the conveying means 5 stays still. In other words, the printing object conveying means 5 makes a predetermined displacement at regular time intervals.

Also, the conveying means 5 is designed in such a way that one displacement phase moves the three-dimensional objects 2.1 , 2.2, 2.3,... always by exactly the distance which is necessary to have the three-dimensional objects 2.1 , 2.2, 2.3,... positioned such that they can be unloaded from the printing object conveying means 5 and loaded onto the printing object supporting means 8.1 , 8.2, 8.3,.... Therefore, the speed (or the displacement rate) of the conveying means 5 depends on the number of the printing object supporting means 8.1 , 8.2, 8.3,... which are available in the inkjet printing machine 1 and these again depend on the number of the printing modules 6 (comprising each four different printing heads 6.1 ,6.2,6.3,...).

Although any number of printing modules 6 can be used (cf. in particular the description further down), the inkjet printing machine 1 according to the present invention will typically have four such modules 6 (or sixteen printing heads 6.1 ,6.2,6.3,..., four for each color). One such group of four printing modules 6 is also called a printing block B. Following this reasoning, if the printing modules 6 are positioned in parallel (as represented in Figure 1 ), the printing object conveying means 5 will be commanded such that the total linear displacement of the conveying means 5 during one printing process corresponds to the distance between the first and the fourth printing module 6. This approach allows then for four three-dimensional objects 2.1 ,2.2,2.3,... to be brought to the correct printing position such that they can be unloaded from the printing object conveying means 5 and loaded onto the printing object supporting means 8.1 ,8.2,8.3,8.4. Again, following this approach allows for an increased speed of the printing process.

Should it be necessary to increase the quantity of the three-dimensional objects 2.1 , 2.2, 2.3,... which are printed at the same time, the machine 1 can be extended with one, two or more additional blocks. In this case, the printing object conveying means 5 can be commanded in a different way such that each three-dimensional object 2.1 , 2.2, 2.3,... reaches its printing position during the printing process of the previous objects.

One possible approach for changing the capacity of the printing object conveying means 5 could be simply changing the speed of the conveying means 5 as a function of the number of printing modules 6. In other words, the printing object conveying means 5 in a machine 1 with only four printing modules 6 or one block B (the standard case) would move at a smaller speed as the printing object conveying means 5 in a machine 1 in which the capacity was increased to eight or twelve printing modules 6 (two or three printing blocks B).

Another approach would be to maintain the average displacement speed of the printing object conveying means 5 constant but to change the displacement i.e. to reduce or to increase the displacement according to the number of modules or according to the loading policy. Namely, as mentioned above, it is in particular possible to use more than one printing module (which generally comprises four printing heads). Generally, the machine according to the present invention will comprise at least four printing modules (or one block). It is however possible to use a different number of printing modules in a block. In any way, if for example only four printing modules (or one block) are used, the printing object conveying means 5 would be loaded at a lower rate than if eight printing modules (two blocks) or even twelve printing modules (three blocks) are used.

If we now assume that the maximal number of printing modules can be twelve (corresponding to three blocks) and that the only possible combina- tions comprise machines with four, eight or twelve printing modules, we could imagine the following loading schemes for three blocks, two blocks and one block, respectively:

12 printing modules O O O O O O O O O O O O O

8 printing modules 0 0 - 0 0 - 0 0 - 0 0 - 0

4 printing modules 0 - - 0 - - 0 - - 0 - - 0

In these schemes, the sign Ό" represents a three-dimensional object 2.1 ,2.2,2.3,... while the sign "-" represents a gap.

It is interesting to note that the displacement with 8 printing modules compared with 4 printing modules correspond to a "division by 2", respectively a "division by 3" if 12 printing modules are used compared with 4 printing modules.

It is also interesting to note that a machine with two blocks does not have the same distance between the blocks as compared with a machine with three blocks.

The corresponding loading possibilities are represented schematically in Figure 5. The reference signs M1, M2, M3,... represent printing modules (typically with four printing heads each), while reference signs B1 , B2, B3 relate to the printing blocks. It can easily be seen that one block B1 , B2, B3 corresponds to four printing modules M1, M2, M3,....

It is obvious that, in case of the variable loading schemes, the loading of the three-dimensional objects 2.1,2.2,2.3,... on the printing object conveying means 5 would need to be performed by a variable speed means which could support this scheme. This detail is represented in Figure 5 by means of different indexing distances t1, t2, t3, a2 and a3 between the individual printing modules M1, M2, M3,.... Although the present disclosure has been described with reference to particular means, materials and embodiments, one skilled in the art can easily ascertain from the foregoing description the essential characteristics of the present disclosure, while various changes and modifications may be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as set forth in the following claims.

Claims

1 . An inkjet printing machine (1 ), in particular for printing onto three- dimensional objects (2.1 , 2.2, 2.3,...), comprising a printing object inputting means (3) for inputting three-dimensional objects (2.1 , 2.2., 2.3, ...) into the machine (1 ), a first printing object transferring means (4) for transferring three-dimensional objects (2.1 , 2.2, 2.3,...) from the printing object inputting means (3) to a printing object conveying means (5), the printing object conveying means (5) conveying the three-dimensional objects (2.1 , 2.2, 2.3,...) until the printing position in the machine (1 ), at least one printing head (6.1 , 6.2, 6.3,...) for applying ink onto the three-dimensional objects (2.1 , 2.2, 2.3,...), and a printing object outputting means (7) for outputting three-dimensional objects (2.1 , 2.2, 2.3,...) from the machine (1 ), characterized in that the inkjet printing machine (1 ) further comprises at least one movable printing object supporting means (8.1 , 8.2, 8.3,...) for supporting and displacing three-dimensional objects (2.1 , 2.2, 2.3,...) with respect to the at least one printing head (6.1 , 6.2, 6.3,...).

2. The inkjet printing machine according to claim 1 , characterized in that the inkjet printing machine (1 ) further comprises a pre-treatment means (9) for pre-treating the three-dimensional objects (2.1 , 2.2, 2.3,...) prior to applying ink onto them.

3. The inkjet printing machine according to claim 1 or 2, characterized in that the inkjet printing machine (1 ) further comprises a second printing object transferring means (10) for transferring three-dimensional objects (2.1 ,

2.2, 2.3,...) from the printing position to the printing object outputting means (7).

4. The inkjet printing machine according to any one of the claims 1 to 3, characterized in that the inkjet printing machine (1 ) comprises instead of a single printing head a printing module (6) with four printing heads (6.1 , 6.2, 6.3, 6.4), wherein the module (6) comprises one of the printing heads for the colors cyan, magenta, yellow and black, respectively.

5. The inkjet printing machine according to any one of the claims 1 to

4, characterized in that the inkjet printing machine (1 ) further comprises a bottom printing head for printing onto the bottom surface of the three-dimensional objects (2.1 , 2.2, 2.3,...).

6. The inkjet printing machine according to any one of the claims 1 to

5, characterized in that the inkjet printing machine (1 ) comprises an UV-head (6.0) for pinning the ink on the three-dimensional objects (2.1 , 2.2, 2.3,...) and/- or an UV-station (1 1 ) for curing the ink on the three-dimensional objects (2.1 , 2.2, 2.3,...).

7. The inkjet printing machine according to any one of the claims 1 to

6, characterized in that a rotation driving means is foreseen for rotating the printing object supporting means (8.1 , 8.2, 8.3,...) around its rotational axis.

8. The inkjet printing machine according to any one of the claims 1 to

7, characterized in that at least two linear driving means are foreseen for displacing the printing object supporting means (8.1 , 8.2, 8.3,...) in two different directions.

9. The inkjet printing machine according to any one of the claims 1 to

8, characterized in that the printing object conveying means (5) is arranged for moving in a discrete way such that it makes a predetermined displacement at regular time intervals.

10. The inkjet printing machine according to any one of the claims 1 to 9, characterized in that the printing machine (1 ) comprises at least one block (B) of four printing modules (6) which are positioned in line with each other.

1 1 . An inkjet printing method, in particular for printing onto three-dimensional objects (2.1 , 2.2, 2.3,...), wherein three-dimensional objects (2.1 , 2.2, 2.3,...) are inputted into the machine (1 ) by means of a printing object inputting means (3), three-dimensional objects (2.1 , 2.2, 2.3,...) are transferred from the printing object inputting means (3) to a printing object conveying means (5) by means of a printing object transferring means (4), the printing object conveying means (5) conveying the three-dimensional objects (2.1 , 2.2, 2.3,...) until the printing position in the machine (1 ), three-dimensional objects (2.1 , 2.2, 2.3,...) are supported and displaced with respect to at least one printing head (6.1 , 6.2, 6.3,...) by at least one movable printing object supporting means (8.1 , 8.2, 8.3,...) such that ink can be applied onto the three-dimensional objects (2.1 , 2.2, 2.3,...) by the at least one printing head (6.1 , 6.2, 6.3,...), and three-dimensional objects (2.1 , 2.2, 2.3,...) are output from the machine (1 ) by a printing object outputting means (7).

12. The inkjet printing method according to claim 1 1 , characterized in that ink is pinned on the three-dimensional objects (2.1 , 2.2, 2.3,...) by an UV-head (6.0) and/or that the ink is cured on the three-dimensional objects (2.1 , 2.2, 2.3,...) by an UV-station (1 1 ).

13. The inkjet printing method according to any one of the claims 1 1 or 12, characterized in that during the application of the ink on the three-dimensional objects (2.1 , 2.2, 2.3,...) the printing object supporting means (8.1 , 8.2, 8.3,...) is rotated around its rotational axis.

14. The inkjet printing method according to any one of the claims 1 1 to 13, characterized in that during the application of the ink on the three-dimensional objects (2.1 , 2.2, 2.3,...) the printing object supporting means (8.1 , 8.2, 8.3,...) is displaced in two different directions.

15. The inkjet printing method according to any one of the claims 1 1 to 14, characterized in that the printing object conveying means (5) moves in a discrete way such that it makes a predetermined displacement at regular time intervals.