The present invention relates to a process for the manufacturing of ceramic slabs with a textured effect, particularly for surface coating.

Background Art

It is well known that in certain industrial sectors there is a strong need to renew products in order to meet specific customers’ requirements.

This need is particularly felt in the field of ceramic slabs intended for coating surfaces such as floors, walls or the like.

In the ceramic sector, in fact, there is an increasing demand for ceramic slabs with decorations which faithfully reproduce the surfaces of natural materials such as wood, marble, rocks, stones or the like.

These surfaces have reliefs and depressions which give a three-dimensional effect, the so-called textured effect, which is difficult to reproduce faithfully and exactly in ceramic manufactured articles.

Processes are known for the manufacturing of ceramic slabs which attempt to reproduce the three-dimensional effect of such natural materials.

Known processes involve the use of moulds or molding jigs adapted to print a predefined imprint reproducing the desired decorative effect, on the surface of a ceramic manufactured article made of raw material, i.e. not yet fired in a kiln.

However, the decorative effects which can be obtained through these methods are not very precise and defined due to the difficulty in obtaining certain effects through a mould.

Moreover, this method requires the replacement of the mould every time the desired decorative effect and/or the size of the ceramic slab have to be changed. Furthermore, in order to respond adequately to customers’ requirements, it is necessary for companies to make one or more specific moulds for every customer.

As a result, companies find themselves forced to keep a plurality of different moulds which are to be installed on the production line every time a change to the production cycle is required.

It is evident, therefore, that the processes of known type are susceptible to further refinements.

Description of the Invention

The main aim of the present invention is to devise a process for the manufacturing of ceramic slabs with a textured effect, particularly for surface coating, which enables ceramic slabs with a textured effect to be manufactured in a practical and easy manner.

A further object of the present invention is to devise a process for the manufacturing of ceramic slabs with a textured effect, particularly for surface coating, which allows reproducing in a faithful and precise manner the three- dimensional effect typical of the surfaces of natural materials.

Still one object of the present invention is to devise a process for the manufacturing of ceramic slabs with a textured effect, particularly for surface coating, which allows customizing the decorative effect to be given to the ceramic slabs quickly and easily, according to the needs of the individual customer.

Another object of the present invention is to devise a process for the manufacturing of ceramic slabs with a textured effect, particularly for surface coating, which allows the aforementioned drawbacks of the prior art to be overcome within a simple, rational, easy and effective to use as well as affordable solution.

The aforementioned objects are achieved by the present process for the manufacturing of ceramic slabs with a textured effect, particularly for surface coating, having the characteristics of claim 1.

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 for the manufacturing of ceramic slabs with a textured effect, particularly for surface coating, illustrated by way of an indicative, yet nonlimiting example, in the accompanying tables of drawings wherein: Figure 1 is a schematic representation of the process according to the invention, according to a first embodiment;

Figures 2 to 5 are schematic representations of the various phases of the process in Figure 1 ;

Figure 6 is a schematic representation of the process according to the invention, according to a second embodiment;

Figures 7 to 10 are schematic representations of the various phases of the process in Figure 6.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally indicates a ceramic slab, particularly for surface coating.

The process according to the invention comprises a phase of full-field distribution of at least one powder 5 comprising at least one raw ceramic material on a supporting surface 4 to obtain a slab-shaped article 2.

Within the scope of the present disclosure, the expression “raw ceramic material” means a mixture of ceramic material, i.e. composed of a mixture comprising at least one of clays, feldspars, kaolin, silica sand, iron oxides, alumina, quartz, etc., not yet fired in a kiln. At the same time, the expression “slab-shaped article” means a manufactured article with significantly greater width and length than its thickness, i.e. at least one order of magnitude greater (i.e. more than 10 times greater).

Advantageously, the powder 5 may also comprise glaze.

Glaze is glass powder, made up of e.g. silicon dioxide, boron trioxide, aluminum oxide. The supporting surface 4 is movable along a direction of forward movement D and is adapted to move the slab- shaped article 2 to implement the various phases of the process.

According to a first embodiment shown in Figures 1 to 5, the supporting surface 4 is defined on top of a movement line 3.

The movement line 3 comprises a series of conveyor belts and roller conveyors arranged in sequence with each other along the direction of forward movement D. It is easy to appreciate, however, that alternative embodiments are possible wherein the movement line 3 consists of forward-moving systems other than those illustrated herein and intended, for example, to transfer the slab-shaped article 2 between different machining stations intended to implement the phases of the process according to the invention.

The slab- shaped article 2 is provided with at least one work surface 2a.

The slab- shaped article 2 is arranged on the movement line 3 with the work surface 2a facing upwards.

Conveniently, the powder 5 comprises a plurality of powder particles 5a provided with a predefined particle size.

The distribution phase allows obtaining one or more layers of powder particles 5a evenly arranged to coat the supporting surface 4 depending on the shape one wish to give to the slab-shaped article 2.

The distribution phase is carried out by means of the distribution means 6.

In the embodiment shown in the figures, the distribution means 6 are of the type of a hopper adapted to release the powder 5 onto the supporting surface 4 as a result of the movement along the direction of forward movement D.

It cannot, however, be ruled out that the distribution means 6 be of a different type.

The process also comprises a phase of at least partial removal of the powder 5 from the work surface 2a according to at least one predefined pattern and at least one predefined depth, by means of radiation-emitting removal means 9.

The removal phase will be described in more detail later on in the present disclosure.

Conveniently, the process also comprises a phase of compression of the powder 5 on the supporting surface 4.

The compression phase has the function of providing greater compactness to the powder 5 and contributes to giving high strength and surface mechanical resistance to the finished ceramic slab 1.

In the embodiment shown in the figures, the compression phase is carried out prior to the removal phase. Alternatively, or in combination thereof, the compression phase may be carried out subsequently to the removal phase.

The compression phase is carried out by means of the compression means 7.

The compression means 7 are of the type of a shifting belt arranged on top of the movement line 3 and adapted to operate in conjunction with the latter to compact the deposited powder 5, as a result of the forward movement of the slab- shaped article 2.

It cannot, however, be ruled out that the compression means be of a different type.

Finally, the process comprises a firing phase of the slab-shaped article 2 in a kiln to obtain a ceramic slab 1 provided with a textured effect.

In the context of the present disclosure, the expression “textured effect” means that the surface of the ceramic slab 1 has a series of reliefs and depressions typical of natural surfaces, such as wood, marble, rocks or the like.

The firing phase is carried out at very high temperatures (greater than 1100 °C) using firing means 14.

The firing means 14 are of the type of a ceramic kiln.

The firing phase has the function of transforming the ceramic material mixture by supplying the finished ceramic slab 1 with a mechanically resistant structure. During this phase, the powder particles 5a firmly unite with each other, by stabilizing the textural decorative effect defined on the surface of the ceramic slab 1 (Figure 5).

In the event of the powder 5 comprising also the glaze, mixed together with the ceramic material, it is possible to avoid the ancillary glazing/coating phases of the ceramic slab 1. The glaze, in fact, melts during firing and allows forming a protective coating for the surface of the ceramic slab 1.

As set forth above, the process comprises a phase of at least partial removal of the powder 5 from the work surface 2a according to at least one predefined pattern and at least one predefined depth.

In particular, the removal phase is carried out so as to make one or more grooves 8 in the powder 5 in order to give a three-dimensional effect to the work surface 2a.

Advantageously, the removal phase comprises a phase of moving at least one powder particle 5a away from the adjacent powder particles 5a.

Specifically, the process provides for the repetition of the moving away phase so as to remove a plurality of powder particles 5a and to form a groove 8.

The removal means 9 comprise at least one laser device 10 adapted to emit a laser beam 11 towards the work surface 2a.

More in detail, the removal means 9 also comprise reflecting means 12 adapted to receive the laser beam 11 from the laser device 10 and to reflect it towards the work surface 2a.

Conveniently, the laser device 10 is of the pulsed type.

The laser device 10 emits short pulses of high-intensity radiations so as to move the powder particles 5a away from the adjacent powder particles 5a while preserving the chemical and physical properties of the ceramic material.

Advantageously, the moving away phase is carried out by interaction between the laser beam 11 and the powder particles 5a.

More in detail, the laser beam 11 is adapted to break the cohesion forces between the powder particles 5a.

As is known to the technician in the sector, cohesion forces are forces of attraction which are created among the molecules of the same substance and which help to keep them united together, opposing any external forces which tend, instead, to separate them. In the case of powders, the cohesion forces are the forces of attraction among the powder particles.

Cohesion forces are a set of bonds of attraction, comprising van der Waals forces, the force of gravity, any compressive forces applied to the powder 5, etc. The laser device 10 is therefore suitably configured to emit the laser beam 11 at an intensity such that it can break such cohesion forces and move the predefined powder particles 5a away while at the same time keep the remaining powder particles 5a in place.

The moving away phase comprises a movement phase of the laser beam 11 relative to the work surface 2a depending on the predefined pattern and the predefined depth.

The movement of the laser beam 11 is carried out by means of the reflecting means 12 which are able to direct the laser beam 11 towards any powder particle 5a as a result of the movement of the slab-shaped article 2 along the direction of forward movement D.

Specifically, the laser beam 11 is moved at different speeds on the powder 5, so as to stay more on the same, depending on the depth which one wishes to give to the grooves 8. More specifically, each groove 8 can be made according to different depths in order to reproduce in an extremely faithful manner the most complex natural materials, such as e.g. wood.

Advantageously, the removal means 9 comprise at least one electronic unit comprising at least one memory unit adapted to store at least one of either the predefined pattern or the predefined depth.

The electronic unit is operatively connected to the reflecting means 12 and is configured to operate the latter to move the laser beam 11 according to the predefined pattern and/or the predefined depth.

As set forth above, the laser beam 11, by interacting with the powder particles 5a, breaks the cohesion forces and helps to push the powder particles themselves away.

Advantageously, the removal phase comprises a suctioning phase of the at least one powder particle 5a moved away.

The suctioning phase occurs substantially at the same time as the removal phase so that the powder particle 5a moved away does not fall back by gravity on the underlying powder particles 5a.

The removal means 9 also comprise suctioning means 13 adapted to remove the powder particle 5a moved away by means of vacuum application.

Conveniently, the process may also comprise an application phase of decorative pigments onto the powder 5.

The decorative pigments are selected from ceramic pigments, powdered metals, glaze or a combination thereof.

The application phase allows the textured effect defined by the grooves 8 to be finished by means of the distribution of the colored decorative pigments, so as to visually emphasize the three-dimensional effect of the ceramic slab 1.

The application phase is preferably carried out prior to firing so that the decorative pigments can be firmly attached to the ceramic materials.

The application phase is carried out using techniques known to the technician in the sector, e.g. digital printing.

Figures 6 to 10 show a second embodiment of the present process which differs from the first embodiment in the following aspect.

The process according to the second embodiment comprises, prior to the distribution phase, at least one phase of providing at least one slab- shaped body 15 made of an additional raw ceramic material.

In particular, the slab- shaped body 15 is made of a first ceramic material and the powder 5 is made of a second ceramic material.

The second ceramic material differs from the first ceramic material in at least one of its composition, color or grain size.

It cannot, however, be ruled out that the second ceramic material coincides with the first ceramic material.

The slab-shaped body 15 defines the supporting surface 4.

In particular, the slab-shaped body 15 is arranged to rest on the movement line 3 with the supporting surface 4 facing upwards.

Prior to the providing phase, the process comprises a phase of pressing the first ceramic material to obtain the slab- shaped body 15.

Similarly to what has been described above for the compression phase, the pressing phase has the function of providing greater compactness to the mixture and contributes to giving high strength and mechanical resistance to the finished ceramic slab 1 as a result of firing at high temperatures.

The pressing phase is carried out by means of pressing means, not shown in the figures, of a type known to the technician in the field.

The ceramic slab 1 is, therefore, composed of a base layer, defined by the slabshaped body 15 and a visible layer, defined by the powder 5.

The slab-shaped body 15 makes the ceramic slab 1 stronger than powder 5 only and its use is especially advantageous in applications where the ceramic slab 1 is subjected to high mechanical stress.

Pressing is carried out at a first pressure value.

The compression phase is carried out at a second pressure value wherein the second pressure value is lower than the first pressure value.

The subsequent distribution phase is, therefore, carried out on the slab-shaped body 15.

The resulting slab-shaped article 2 is, therefore, defined by the slab-shaped body 15 and by the layers of powder particles 5a distributed thereon.

As a result of the removal phase, the slab- shaped article 2 is subjected to the firing phase wherein the first ceramic material and the second ceramic material join intimately together, providing the finished ceramic slab 1 with a mechanically resistant structure.

It has in practice been ascertained that the described invention achieves the intended objects, and in particular the fact is emphasized that the process according to the present invention allows manufacturing, in a practical and easy manner, ceramic slabs provided with a textured effect, and in particular, it allows reproducing, in a faithful and precise manner, the three-dimensional effect typical of the surfaces of natural materials.

Moreover, this process allows customizing the decorative effect to be given to the ceramic slabs in a quick and easy manner, according to the requirements of the individual customer.