Technical Field

The present invention relates to a process and system for the decoration of ceramic slabs.

Background Art

Ceramic slabs are widely used in the construction industry to cover floors and walls.

In this sector there is a strong need to produce articles provided with valuable decorative effects and through methods allowing a precise and faithful reproduction of the desired designs.

The decoration of ceramic slabs consists in the application of decorative elements on the surface of flat manufactured articles, made of unfired or partly fired ceramic material at low temperatures, to be then completely and definitively stabilized by firing at high temperatures.

Generally, the processes of known type for the decoration of ceramic slabs involve the use of nano-inks deposited on the surface of the manufactured articles by means of special digital printers with piezoelectric heads.

More in details, nano-inks are powdered dye mixtures of very fine nanometersized particles, suspended in a special solvent or other carrier.

This process for the decoration of ceramic slabs has some drawbacks related to the use of the aforementioned nano-inks.

In particular, the milling of dyes for nano-inks is carried out by means of special equipment (atomizers and/or turbines) which are able to reduce the particles to very small sizes, in the order of nanometers, but which are very expensive and have a rather low production output, as well as non-negligible energy consumption.

As a result, the overall costs for the production of nano-inks are very high and have an impact on the final price of ceramic slabs, with the risk of making the products less attractive to customers.

At the same time, the solvents required for the production of nano-inks are usually organic solvents which, in addition to being harmful to the environment and to the health of the operators who use them, lead to rapid wear of the printing heads.

In the light of the previous considerations, it is clear that the known decoration processes mentioned above are susceptible to further refinements aimed at obtaining decorated ceramic articles with a valuable aesthetic effect, in a practical, safe and low-cost manner.

Description of the Invention

The main aim of the present invention is to devise a process and a system for the decoration of ceramic slabs which allow obtaining a valuable aesthetic effect through surface decoration.

A further object of the present invention is to devise a process and a system for the decoration of ceramic slabs which allow them to be freed from the use of nano-inks and digital printers.

Another object of the present invention is to devise a process and a system for the decoration of ceramic slabs which allow using low-cost decorative devices and materials in order to obtain decorated ceramic slabs, in a practical manner and under safe conditions for the environment and the operators.

Another object of the present invention is to devise a process and a system for the decoration of ceramic slabs which make it possible to overcome the aforementioned drawbacks of the prior art within the scope of a simple, rational, easy and effective to use as well as affordable solution.

The objects set out above are achieved by the present process for the decoration of ceramic slabs having the characteristics of claim 1.

The objects set out above are achieved by the present system for the decoration of ceramic slabs having the characteristics of claim 15.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a process and a system for the decoration of ceramic slabs, illustrated by way of an indicative, yet non-limiting example, in the accompanying tables of drawings wherein:

Figure 1 is an axonometric view of the system in the execution of the process according to the invention;

Figure 2 is an axonometric view of a possible embodiment of the laser device according to the invention;

Figure 3 is an axonometric view of a further embodiment of the laser device according to the invention.

Figure 4 is a side detailed view of a first embodiment of the application means according to the invention;

Figures 5 and 6 are schematic representations of a second embodiment of the application means according to the invention.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally indicates a system for the decoration of ceramic slabs.

In the context of the present disclosure, the expression “ceramic slab” means an article having width and length significantly greater than its thickness, i.e. at least one order of magnitude greater (i.e. more than 10 times greater), intended for covering surfaces such as e.g. floors, walls or the like.

The system 1 according to the invention comprises at least one supporting surface 2 movable along a direction of forward movement D and adapted to sustain a slab-shaped article 3.

In the embodiment shown in the figures, the supporting surface 2 is schematically represented in the form of a series of conveyor belts and roller conveyors arranged in succession, on which the various machining phases of the slab- shaped article 3 are performed.

It is easy to appreciate, however, that alternative embodiments are possible wherein the supporting surface 2 consists of systems of forward movement different from those illustrated and intended, e.g., to transfer the slab-shaped article 3 between different machining stations.

The slab-shaped article 3 is made of unfired ceramic material.

In the context of the present disclosure, the expression “unfired ceramic material” means a mixture of ceramic material that has not yet been fired in a kiln.

The slab-shaped article 3 is provided with a substantially flat surface to be decorated 4. The expression “substantially flat” means that the slab-shaped article 3 may also have slightly convex or suitably machined surfaces in order to give a particular aesthetic effect to the finished ceramic slab (so-called “structured surfaces”).

The slab- shaped article 3 is arranged on the supporting surface 2 with the surface to be decorated 4 facing upwards.

The system 1 comprises application means 5a, 5b of a decorative powder P to the surface to be decorated 4.

Usefully, the decorative powder P is composed of one out of: one or more colored metal oxides and glaze.

In particular, metal oxides are characterized by complex chemical structures which give them special colorations. The application of colored metal oxides therefore allows obtaining a colored decorated surface 10.

The glaze, on the other hand, is glass powder, composed e.g. of silicon dioxide, boron trioxide, aluminum oxide which during firing melts and, in addition to giving a glazed effect to the decorated surface 10, also forms a protective cover for the ceramic slab 12.

The decorative powder P is made in micrometer particle sizes.

The application means 5a, 5b comprise: at least one transfer surface 6 on which the decorative powder P is dispensed; and at least one laser device 7 adapted to emit at least one laser beam 8 towards the decorative powder P, according to at least one predefined design 9.

The interaction between the laser beam 8 and the decorative powder P generates a decorative gas G adapted to be deposited on the surface to be decorated 4 according to the predefined design 9 to obtain a decorated surface 10.

In particular, the application means 5a, 5b are adapted to apply the decorative powder P to the surface to be decorated 4 according to the predefined design 9 as a result of the movement of the slab- shaped article 3 along the direction of forward movement D.

The system 1 then comprises firing means 11 of the slab-shaped article 3 to obtain a ceramic slab 12.

The firing means 11 comprise, e.g., a ceramic kiln adapted to fire the unfired ceramic material at high temperatures (greater than 1100°C) to obtain the ceramic slab 12.

This operation has both the function of transforming the composition of the unfired material mixture, thus providing the finished ceramic slab 12 with a mechanically resistant structure, and the objective of fixing the decoration on the decorated surface 10. During firing, in fact, the decorative powder P interacts with the ceramic material, stabilizing itself.

Usefully, the application means 5a, 5b also comprise dispensing means 13 of the decorative powder P on the transfer surface 6.

The dispensing means 13, of the type e.g. of a hopper, are adapted to spread a layer of decorative powder P on the transfer surface 6.

According to a first embodiment shown in Figure 4, the decorative powder P is dispensed substantially evenly over the transfer surface 6.

In order to ensure even spreading, the decorative powder P may be dispensed, e.g., by electrostatic deposition. By this method, the particles of decorative powder P are subjected to a negative or positive electrical charge, while the transfer surface 6 is grounded (potential 0).

In this way, the decorative powder P is attracted by the transfer surface 6 thus ensuring even coverage.

The transfer surface 6 faces, at least partly, the surface to be decorated 4.

In more detail, the application means 5a, 5b comprise a transfer body 14 arranged above the supporting surface 2 and defining the transfer surface 6, facing at least partly towards the supporting surface 2.

The transfer body 14 also comprises a work surface 15 opposite the transfer surface 6.

The work surface 15 faces the laser device 7. Advantageously, the transfer surface 6 is transparent to the laser beam 8.

In more detail, the transfer body 14 is made of a material transparent to the laser beam 8.

The laser device 7 is configured to irradiate special points on the work surface 15, thus transferring the energy to the transfer surface 6 and consequently to the decorative powder P.

The laser beam 8 then strikes the decorative powder P passing through the transfer body 14.

In particular, the interaction of the laser beam 8 with the decorative powder P results in at least partial sublimation of the decorative powder itself.

The laser device 7 is configured to emit the laser beam 8 at a predefined intensity and frequency such that sublimation of the stroken decorative powder P is induced.

Specifically, the laser beam 8 is emitted at a power density greater than 10 ⁶ W/cm ² . For example, at a power density of 10 ⁸ W/cm ² .

The decorative gas G, thus generated, expands to form a laser plume facing the surface to be decorated 4.

As is known to the technician in the sector, the expression “laser plume” means a cloud of gaseous material which, due to the high power of the laser beam, is thrown towards a deposition surface taking the shape of a plume.

Then, upon contact with the surface to be decorated 4, the decorative gas G is deposited according to the predefined design 9.

It should be noted that the transfer surface 6 and the surface to be decorated 4 are arranged at a very close distance so as to avoid dispersion of the decorative gas G, so that the deposition of the decorative gas itself corresponds exactly to the predefined design 9.

The laser device 7 is configured to emit the substantially punctiform- section laser beam 8, and is positioned so that such laser beam 8 is substantially transverse to the work surface 15.

The laser device 7 is mounted on a crossbar 16, which is arranged above the supporting surface 2 and extends along a horizontal direction and orthogonal to the direction of forward movement D.

In one possible embodiment, shown in Figure 2, the laser device 7 is movable by sliding on the crossbar 16 so as to move from side to side on the work surface 15 and direct radiation to any point on the transfer surface 6 as the slabshaped article 3 moves forward along the direction of forward movement D.

The laser device 7 is adapted, therefore, to emit the laser beam 8 in a work plane transverse to the direction of forward movement D. Specifically, the work plane is orthogonal to the direction of forward movement D.

In other words, the laser device 7 behaves similarly to a head for printers and is movable at the same time as the slab- shaped article 3 slides.

In a further embodiment, not shown in detail in the figures, the laser beam 8 may be shifted by means of special movable reflective means with respect to the crossbar 16. In this embodiment, the laser device 7 is fixed with respect to the crossbar 16, while the movement of the laser beam 8 is performed through the reflective means, sliding on the crossbar 16.

In a further embodiment, shown in Figure 3, the laser device 7 is movable in rotation around an axis of work A substantially parallel to the direction of forward movement D and is adapted, therefore, to emit the laser beam 8 in the work plane, which is substantially perpendicular to the axis of work itself.

Thus, even in this second embodiment, the laser beam 8 is able to reach any point on the slab- shaped article 3 as it moves forward along the direction of forward movement D.

Similarly to what has been described for the first embodiment, the laser beam 8 may be rotated by means of special reflective means which can be rotated with respect to the crossbar 16.

Conveniently, the application means 5a, 5b comprise at least one electronic unit 17 operatively connected to the laser device 7 and configured to store the predefined design 9 and to operate the laser device 7 depending on the predefined design itself.

According to a first embodiment of the present invention, shown in Figure 4, the decorative powder P is evenly dispensed on the transfer surface 6 and the laser device 7 is configured to strike the work surface 15 at each point, according to the predefined design.

Advantageously, the transfer surface 6 is substantially continuous.

In the embodiment shown in the figures, the transfer surface 6 is substantially cylindrical.

It cannot, however, be ruled out that the work surface 15 may have a different conformation.

Specifically, the transfer body 14 is substantially rigid, shaped as a hollow cylinder, and has an outwardly facing transfer surface 6 and an inwardly facing work surface 15.

It cannot be ruled out that the transfer body may have a different conformation. Likewise, it cannot be ruled out that the transfer body 14 may be of the type of a transparent tape.

The transfer surface 6, therefore, has only one portion facing the surface to be decorated 4.

Preferably, the transfer body 14 is arranged above the supporting surface 2 with the relevant longitudinal axis substantially parallel to the supporting surface 2 and transverse to the direction of forward movement D. Preferably, the transfer body 14 is positioned with its longitudinal axis orthogonal to the direction of forward movement D.

The transfer body 14 extends along the relevant longitudinal axis by a length at least equal to the width of the slab- shaped article 3.

The laser device 7 is arranged inside the transfer body 14 and is configured to emit the laser beam 8 towards the portion of the transfer surface 6 which faces the surface to be decorated 4.

In more detail, the laser device 7 is configured to emit the laser beam 8 perpendicularly to the surface to be decorated 4.

The transfer surface 6 is movable to continuously position a portion of the decorative powder P at the point where the work plane of the laser beam 8 is located.

In particular, the transfer surface 6 is movable in rotation around a relevant axis of rotation R.

The axis of rotation R coincides with the longitudinal axis of the transfer body 14.

The transfer surface 6 rotates around the axis of rotation R so that the laser beam 8 may continuously strike a portion of the transfer surface 6 which is entirely covered by the decorative powder P.

Specifically, as a result of the rotation of the transfer body 14, the transfer surface 6 has a first stretch 6a, which has already interacted with the laser beam 8 and is partly free of decorative powder P, moving away from the surface to be decorated 4, and a second stretch 6b, which is completely covered with the decorative powder P, moving close to the surface to be decorated 4.

In this way, the application means 5a, 5b are able to apply the decorative powder P to the slab- shaped article 3 in a substantially continuous manner, allowing optimization of the operating times.

For this purpose, the dispensing means 13 are usefully adapted to dispense the decorative powder P onto the transfer surface 6 as a result of the rotation of the transfer body 14 around the axis of rotation R.

Specifically, the dispensing means 13 are adapted to restore the layer of decorative powder P on the transfer surface 6 in a substantially continuous manner.

The special expedient of providing a continuous, specifically cylindrical transfer surface makes it possible to apply the decorative powder P in a substantially continuous manner, thus avoiding any interruption due to the restoration of the layer of decorative powder itself.

Advantageously, the system 1 may comprise a plurality of application means 5a, 5b arranged side by side along the direction of forward movement D and adapted to apply different decorative powders P and/or according to different predefined designs 9.

In the embodiment shown in Figure 1 , for example, the system 1 comprises first application means 5a adapted to apply a colored decorative powder P, i.e., composed of one or more colored metal oxides, to the surface to be decorated 4, and second application means 5b adapted to apply a decorative powder P composed of glaze to the surface to be decorated 4 so as to give a protective cover to the ceramic slab 12.

In particular, the second application means 5b are arranged downstream of the first application means 5a with respect to the direction of forward movement D so as to cover the previously applied colored metal oxides with the glaze.

Usefully, the laser device 7 of the second application means 5b may be moved so as to apply the decorative powder P in full field or according to a predefined design 9 so as to cover only part of the surface to be decorated 4.

In a further embodiment not shown in detail in the figures, the system 1 comprises a plurality of first application means 5a, each adapted to apply a decorative powder P provided with a different color so as to make elaborate decorations.

Specifically, the first application means 5a can apply decorative powders P having only primary colors, which, as a result of deposition, combine together to generate colors which are different from the primary colors themselves.

In addition, the electronic unit 17 may determine an appropriate movement of the relevant laser devices 7, following several predefined designs 9 depending on the type of decorative powder P used.

In other words, the application of the decorative powder P with a first primary color can be performed following a first predefined design, the application of the decorative powder P with the second primary color can be performed following a second predefined design, the application of the decorative powder P with the third primary color can be performed following a third predefined design, and so on.

The operation of the present system 1 in the execution of the process according to the invention is as follows.

The process comprises a supply of at least one slab-shaped article 3 made of unfired ceramic material, provided with at least one surface to be decorated 4. The slab- shaped article 3 is placed on the supporting surface 2 with the surface to be decorated facing upwards and moved along the direction of forward movement D.

The process then comprises a phase of application of at least one decorative powder P on the surface to be decorated 4 according to at least one predefined design 9 to obtain a decorated surface 10.

The phase of application is performed by means of the application means 5a, 5b.

Finally, the process involves a firing phase of the slab-shaped article 3 in a kiln to obtain a ceramic slab 12.

The firing phase is performed by means of the firing means 11.

According to the invention, the application phase comprises: a phase of dispensing of the decorative powder P on a transfer surface 6; a phase of treatment of the decorative powder P on the transfer surface 6 to obtain a decorative gas G; and a phase of deposition of the decorative gas G on the surface to be decorated 4 according to the predefined design 9.

The phase of dispensing is performed by means of the dispensing means 13 so as to cover the transfer surface 6 in a substantially even manner.

The phase of dispensing can be performed, e.g., by electrostatic deposition of the decorative powder P on the transfer surface 6.

The phase of treatment comprises the sub-phases of: emission of a laser beam 8 towards the transfer surface 6; interaction of the laser beam 8 with a portion of the decorative powder P to generate the decorative gas G.

The phase of emission is performed by means of the laser device 7, which is adapted to generate the laser beam 8.

The laser beam 8 is suitably moved according to the predefined design 9 so as to strike only part of the decorative powder P present on the transfer surface 6.

In more detail, the phase of interaction is performed by passing the laser beam 8 through the transfer surface 6.

Specifically and as set forth above, the laser beam 8 strikes the work surface 15, passes through it and reaches the decorative powder P dispensed on the transfer surface 6.

Advantageously, the interaction comprises a phase of at least partial sublimation of the decorative powder P.

The laser beam 8 is emitted at such a power that it causes the particles of decorative powder P to sublimate.

The phase of interaction also comprises a phase of expansion of the decorative gas G to form a laser plume facing the surface to be decorated 4.

Usefully, the phases of treatment and deposition are performed in a substantially continuous manner. In fact, the presence of a continuous transfer surface 6 allows the decoration to be performed without interruption of the operating phases.

Appropriately, the phase of dispensing is also performed in a substantially continuous manner.

In more detail, the dispensing is performed following the rotation of the transfer surface 6 around the axis of rotation R.

Advantageously, the process comprises the repetition of the phase of application with different decorative powders P and/or depending on different predefined designs 9.

Figures 5 and 6 show a second embodiment of the present invention which differs from the previous one in the following characteristics.

As shown in the figures, the transfer surface 6 comprises a plurality of holes 18 adapted to contain the decorative powder P.

The holes 18 are made on the transfer body 14 by material removal using the technique of laser etching, acid etching, or a combination thereof.

With reference to Figures 5 and 6, it should be specified that the holes 18 are shown with out-of-scale dimensions for simplicity of representation.

The actual dimensions of the holes 18 are in the order of micrometers. Specifically, the holes 18 have a depth comprised between 10-50 pm and a diameter comprised between 50-100 pm. The holes 18 are arranged at a minimum mutual spacing of 10-30 pm.

In addition, the holes 18 are shown to be circular in shape. It cannot, however, be ruled out that the holes may have polygonal or irregular conformation.

The interaction of the laser beam 8 with the decorative powder P is performed at the point where the holes 18 are located.

This embodiment solution allows for extremely precise application of the decorative powder P, resulting in sharp, outlined decorative effects.

The holes 18 are, in fact, adapted to contain a substantially even amount of decorative powder. It follows that the laser beam 8, emitted at the point where the holes 18 are located, always strikes the same amount of decorative powder P.

Usefully, the phase of dispensing comprises a phase of introduction of the decorative powder P inside the holes 18.

For this purpose, the application means 5a, 5b comprise leveling means 19 of the decorative powder P on the transfer surface 6 which are adapted to equalize the content of the decorative powder P inside the holes 18.

The leveling means 19 comprise, e.g., a squeegee.

The phase of introduction is performed continuously by means of the leveling means 19, following the rotation of the transfer body 14.

Conveniently, the holes 18 are arranged according to a predefined pattern.

Thus, the electronic unit 17 is also configured to store the predefined pattern and to operate the laser device 7 according to the predefined pattern itself and to the predefined design.

In other words, the laser beam 8 may only be directed to those parts of the transfer surface 6 where the decorative powder P is present, namely the holes 18.

As shown in Figure 6, the holes 18 are made according to a die and are arranged in rows Fl-Fn and columns.

In more detail, the rows Fl-Fn are substantially parallel to the axis of rotation R and transverse to the direction of forward movement D.

Preferably, the rows Fl-Fn are substantially perpendicular to the direction of forward movement D.

During the phase of treatment, the laser device 7 is, therefore, configured to emit the laser beam 8 between the first hole 18 and the last hole 18 of a same row F. Following the rotation of the transfer body 14 around the axis of rotation R, each row F is systematically positioned in the work plane of the laser beam 8, which can be moved to strike the decorative powder P present inside the holes 18.

It has in practice been ascertained that the described invention achieves the intended objects, and in particular the fact is emphasized that the process and the system for the decoration of ceramic slabs according to the invention allow achieving a valuable aesthetic effect through a surface decoration of the same. In addition, the present process and system allow doing without the use of nanoinks and digital printers.

Finally, the present process and system allow using affordable decorative devices and materials in order to obtain decorated ceramic slabs, in a practical manner and under conditions of safety for the environment and the operators.