The present invention relates to a digital printer for the decoration of tiles made of ceramic material.

Background Art

In the field of ceramic manufacture, the need has long been felt to decorate the exposed face of tiles for mainly aesthetic purposes.

This practice is also linked to the need of ceramic industries to produce tiles that differ as much as possible from those of the competition and that best meet the aesthetic standards required by customers.

Specifically, the decoration of tiles consists in the application of pigments on the exposed face of the tiles, made of raw or partially fired ceramic material, to be then completely and definitively stabilized by firing them in the kiln.

The decoration of tiles can be done using different methods and, currently, the use of digital printers is very widespread.

The decoration of tiles through digital printers involves the application of ceramic inks on the exposed face of the tiles, these inks being mixtures of powder dyes, with very fine grain size, suspended in a special solvent or another carrier agent.

The digital printers for the decoration of tiles made of ceramic material of known type usually comprise a plane of forward movement on which the tile to be decorated is laid and a plurality of printing heads facing the plane of forward movement and dispensing the ceramic ink on the exposed face of the tile.

The plane of forward movement is usually composed of a conveyor belt that is moved along a substantially horizontal direction thanks to motor-driven mechanical rollers.

This way the tile is moved below the printing heads during the dispensing of the ceramic ink.

The printing heads spray the ceramic ink onto the exposed face of the tile according to a previously established design. The digital printers for the decoration of tiles made of ceramic material of known type do have some drawbacks.

Specifically, the digital printers of known type do not allow obtaining a full- bodied coloring of the tile.

More precisely, the digital printers for the decoration of tiles made of ceramic material of known type apply a decoration that has a very reduced thickness (of the order of a few micrometers) with respect to the thickness of the tile (of the order of a few millimeters).

This means that the tiles decorated by means of digital printers cannot often be subjected to additional machining such as, e.g., sanding occurring after installation.

The sanding of the tiles, in fact, involves the partial removal of material from the exposed face in order to make the surface of the tiles shinier and as free of surface imperfections as possible.

In the case of sanding decorated tiles using digital printers, therefore, the decoration is almost entirely abraded due to the reduced thickness of the same; for this reason, the digitally printed tiles are never sanded after installation and this determines an important limit for the use of this technology.

Description of the Invention

The main aim of the present invention is to devise a digital printer for the decoration of tiles made of ceramic material that allows obtaining a full-bodied decoration or at least an increase in the thickness of the decoration itself.

Another object of the present invention is to devise a digital printer for the decoration of tiles made of ceramic material that allows getting decorated tiles that can be sanded.

Another object of the present invention is to devise a digital printer for the decoration of tiles made of ceramic material that allows overcoming the above mentioned drawbacks of the prior art in a simple, rational, easy and effective to use solution with the highest possible aesthetic effects.

The above mentioned objects are achieved by the present digital printer for the decoration of tiles made of ceramic material having the characteristics of claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will be more evident from the description of a preferred, but not exclusive, embodiment of a digital printer for the decoration of tiles made of ceramic material, illustrated by way of an indicative, yet non-limiting example, in the attached tables of drawings in which:

Figure 1 is an axonometric view of the digital printer according to the invention; Figure 2 is a side, partly split view, of the digital printer according to the invention.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally indicates a digital printer for the decoration of tiles made of ceramic material.

In the particular embodiment shown in Figure 1, the digital printer 1 is placed between a feeding line 39 of the tiles 19 to be decorated and a moving-away line 40 of the decorated tiles 19.

The feeding line 39 conveys the tiles 19 towards the digital printer 1 for the decoration thereof, while the moving-away line 40 receives the decorated tiles 19 from the digital printer 1 and conveys them towards the next machining stations.

The digital printer 1 comprises at least one bearing frame 2 onto the ground.

The bearing frame 2, e.g., comprises holding bars 3 made of metal material mutually associated to each other to form a reticular structure resting on the ground.

The bearing frame 2 also comprises a plurality of containment walls 4 made of plastic and/or metal material and associated with the holding bars 3.

The digital printer 1 comprises at least one substantially horizontal plane of forward movement 5 which is associated with the bearing frame 2. Advantageously, the plane of forward movement 5 comprises at least one flexible element 6 wound at least partly around at least one inlet roller 7 and at least one outlet roller 8 which are associated with the bearing frame 2. Alternative embodiments cannot however be ruled in which the plane of forward movement 5 is shaped differently; for example, the plane of forward movement 5 may comprise a roller conveyor.

The flexible element 6 is substantially a belt made of polymeric material, rubber or the like, and which is arranged to form a closed ring-shaped band positioned outside to the inlet roller 7 and to the outlet roller 8.

Specifically, the inlet roller 7 and the outlet roller 8 hold the flexible element 6 and keep it substantially taut.

The inlet roller 7 and the outlet roller 8 are positioned at the same height, have a substantially cylindrical shape and extend along a first axis A and a second axis B respectively, substantially horizontal and mutually parallel.

The inlet roller 7 is associated with the bearing frame 2 in rotation around the first axis A and the outlet roller 8 is associated with the bearing frame 2 in rotation around the second axis B.

In the particular embodiment shown in the figures there are also a first auxiliary roller 9 and a second auxiliary roller 10 associated with the bearing frame 2.

The first auxiliary roller 9 and the second auxiliary roller 10 are positioned at the same height, have a substantially cylindrical shape and extend along a third axis C and along a fourth axis D respectively, substantially horizontal and parallel to each other.

The first auxiliary roller 9 is associated with the bearing frame 2 in rotation around the third axis C and is positioned below the inlet roller 7.

The second auxiliary roller 10 is associated with the bearing frame 2 in rotation around the fourth axis D and is positioned below the outlet roller 8.

The flexible element 6 is partly wound around the first auxiliary roller 9 and the second auxiliary roller 10 which hold the flexible element 6 and keep it substantially taut by operating in conjunction with the inlet roller 7 and the outlet roller 8.

Alternative embodiments cannot however be ruled out in which the first auxiliary roller 9 and the second auxiliary roller 10 are absent, or in which a different number of auxiliary rollers are present. For example, an alternative embodiment can be envisaged in which there is only one of either the first auxiliary roller 9 or the second auxiliary roller 10 allocated below the inlet roller 7 and the outlet roller 8 and positioned in an intermediate position between them.

The digital printer 1 comprises movement means 11 of the plane of forward movement 5.

Specifically, the movement means 11 comprise a motor 12 that moves in rotation the first auxiliary roller 9 around the third axis C.

The setting in rotation of the first auxiliary roller 9 causes the flexible element 6 to be dragged and also the setting in rotation of the inlet roller 7, the outlet roller 8 and the second auxiliary roller 10.

Alternative embodiments cannot however be ruled out, wherein the digital printer 1 comprises different movement means 11 of the plane of forward movement 5 in which, e.g., the motor 12 can move the second auxiliary roller 10 and/or the inlet roller 7 and/or the outlet roller 8.

Again, in the particular embodiment shown in the figures, the motor 12 is of the electric type and the digital printer 1 comprises a power supply unit 13 of the motor 12; alternative embodiments cannot however be ruled out in which the motor 12 is of a different nature, e.g. of the hydraulic type.

Conveniently, the flexible element 6 comprises: at least one forward section 14 extending from the inlet roller 7 to the outlet roller 8; and at least one backward section 15 extending from the outlet roller 8 to the inlet roller 7.

The forward section 14 has a longitudinal extension along a substantially horizontal axis.

The backward section 15 comprises: a first section 16 that extends from the outlet roller 8 to the second auxiliary roller 10 and has a longitudinal extension along a substantially vertical axis; a second section 17 that extends from the second auxiliary roller 10 to the first auxiliary roller 9 and has a longitudinal extension along a substantially horizontal axis; a third section 18 that extends from the first auxiliary roller 9 to the inlet roller 7 and has a longitudinal extension along a substantially vertical axis. The plane of forward movement 5 is adapted to move at least one tile 19 made of ceramic material along a substantially horizontal direction of forward movement L.

The ceramic material of which the tile 19 is made is usually a raw material that has different levels of porosity depending on the level of compaction of the ceramic material itself.

In this regard, it should be noticed that the ceramic material may be compacted and have a low porosity or be semi-compacted and have a higher porosity.

The tile 19 is a substantially solid body that has a substantially slab-shaped conformation and that must be decorated.

The tile 19 can have different dimensions and can consist of a mixture of different ceramic material depending on the particular manufacturing plant in which the digital printer 1 is inserted.

In this regard, it should be noted that, in the ceramic industry, both large size slabs (e.g. 1 m x 3 m) and smaller size slabs (e.g. 10 cm x 10 cm) can be decorated.

Furthermore, the slabs to be decorated have variable thickness which can be very small (e.g. 3 mm in the case of laminated slabs) or higher (e.g. up to 8 mm or more).

The tile 19 is provided with a laying face 20 resting on the plane of forward movement 5 and with an exposed face 21 facing upwards.

The laying face 20 is placed on the forward section 14 and is the portion of the tile 19 that is attached to the wall to be covered during the use of the tile 19 itself.

The exposed face 21 is opposite the laying face 20 and is visible after the tile has been installed.

The exposed face 21 is totally or partly decorated by the digital printer 1.

In the particular embodiment shown in Figure 1, the tile 19 comes from the feeding line 39 and is positioned on the plane of forward movement 5 at the point where the inlet roller 7 is located; thanks to the movement of the plane of forward movement 5 by the movement means 11 , the tile 19 is moved towards the outlet roller 8 and arrives on the moving-away line 40.

The direction of forward movement L substantially coincides with the horizontal direction from the inlet roller 7 to the outlet roller 8.

After the tile 19 moves in the proximity of the outlet roller 8, it is removed from the plane of forward movement 5 and positioned on the moving-away line 40. The digital printer 1 comprises a plurality of printing heads 22 associated with the bearing frame 2 and positioned on top of the plane of forward movement 5. Conveniently, the printing heads 22 are attached to the bearing frame 2. Specifically, the containment walls 4 define on top of the plane of forward movement 5 a containment compartment 23 inside which the printing heads 22 are allocated and, precisely, are attached to the internal surface of the containment compartment 23.

The containment compartment 23 has an opening at the bottom from which the printing heads 22 partly protrude towards the plane of forward movement 5.

The printing heads 22 are adapted to spray at least one ceramic ink 24 onto the exposed face 21.

In the particular embodiment shown in the figures, the digital printer 1 is intended to spray on the exposed face 21 a plurality of ceramic inks 24 that differ according to the chemical composition and according to the color generated on the exposed face 21 after being attached.

In more detail, each printing head 22 sprays just one ceramic ink 24 onto a predefined portion of the exposed face 21; this prevents inadvertent contamination between different ceramic inks 24 inside the printing head 22. Advantageously, the digital printer 1 comprises a management and control unit (not shown in the figures) through which the printing heads 22 can be operated and adjust the type and amount of ceramic ink 24 to be sprayed on the exposed face 21.

Furthermore, the digital printer 1 comprises adjusting means 41 of the pressure of the ceramic ink 24 leaving the printing heads 22.

In the particular embodiment shown in the figures, the adjusting means 41 are allocated inside the containment compartment 23 and are positioned on top of the printing heads 22.

The digital printer 1 advantageously comprises a plurality of tanks 27 inside which the ceramic inks 24 are stored.

The tanks 27 are connected to the printing heads 22 via the supply channels 28 of the ceramic ink 24 towards the printing heads 22.

The containment walls 4 form, below the plane of forward movement 5, a containment volume 29 inside which the tanks 27 are housed.

The digital printer 1 conveniently comprises at least one pumping unit 42 allocated inside the containment volume 29 and associated with the bearing frame 2.

The pumping unit 42 is connected in a fluid- operated manner to each tank 27 and to the supply channels 28 and is adapted to take the ceramic ink 24 from the tanks 27 and to send it to the printing heads 22 through the supply channels 28. According to the invention, the digital printer 1 comprises at least one polarization assembly 30 associated with the printing heads 22, positioned on top of the plane of forward movement 5 and adapted to generate at least a first electromagnetic field 31 for the polarization of the ceramic ink 24 sprayed by the printing heads 22.

Conveniently, the polarization assembly 30 comprises at least one polarization duct 25 positioned upstream of the printing heads 22 and adapted to be crossed by the ceramic ink 24.

In the particular embodiment shown in the figures there is a plurality of polarization ducts 25 and, specifically, each polarization duct 25 is allocated upstream of a printing head 22.

This way, the ceramic ink 24 coming out of a polarization duct 25 is directed towards a single printing head 22.

Advantageously, in the particular embodiment shown in the figures, the polarization ducts 25 have longitudinal extension along a substantially vertical axis and are arranged on top of the printing heads 22.

The polarization ducts 25 extend in a substantially perpendicular manner to the plane of forward movement 5 and, this way, the direction of the ceramic ink 24 towards the printing heads 22 is facilitated.

Conveniently, the polarization assembly 30 comprises at least one coil 32 extending around the polarization duct 25 and adapted to be crossed by a first electric current to generate the first electromagnetic field 31.

In the particular embodiment shown in the figures there is a plurality of coils 32 and, precisely, each coil 32 is associated with a polarization duct 25.

The coils 32 consist of a wire made of electrically conductive material wound on itself to form a spiral.

In the particular embodiment shown in the figures, the coils 32 extend longitudinally according to a substantially vertical direction.

In particular, each coil 32 extends in a coaxial direction to the polarization duct 25 of a printing head 22.

Alternative embodiments cannot however be ruled in which the coils 32 have different extension.

For example, in case the polarization ducts 25 have longitudinal extension along an oblique axis, the coils 32 also have longitudinal extension along an oblique axis.

The first electric current passes through each coil 32, thus generating the first electromagnetic field 31 the intensity of which is greater at the longitudinal axis of the coil 32 itself.

The ceramic ink 24 passing through the polarization duct 25 is immersed inside the first electromagnetic field 31.

The ceramic ink 24, which contains metal mineral oxides, is particularly able to be affected by electromagnetic phenomena and therefore polarizes, i.e. it is electrically charged.

According to the invention, the digital printer 1 comprises at least one electromagnetic fields generation assembly 33 which is associated with the bearing frame 2 below the plane of forward movement 5 and is adapted to generate at least a second electromagnetic field 34 directed downwards and to attract downwards the polarized ceramic ink 24 deposited on the exposed face 21.

Conveniently, the forward section 14 and the backward section 15 are positioned spaced apart to each other in order to define at least one housing compartment 35 of the EMF generation assembly 33.

More precisely, the housing compartment 35 is comprised between the forward section 14, the first section 16, the second section 17 and the third section 18. The electromagnetic fields generation assembly 33 is positioned between the forward section 14 and the second section 17 and between the first section 16 and the third section 18.

Conveniently, the electromagnetic fields generation assembly 33 comprises a plurality of electric windings 36 having a longitudinal extension along a substantially vertical axis of magnetization M.

Alternative embodiments cannot however be ruled in which the axis of magnetization M is differently oriented, e.g. oblique.

Each electric winding 36 is substantially a coil composed of a wire made of an electrically conductive material wound in a spiral on a cylinder with a central longitudinal axis coinciding with the axis of magnetization M.

Conveniently, the electric windings 36 are fastened to the bearing frame 2. Specifically, the bearing frame 2 comprises a substantially horizontal holding plane 37, housed inside the housing compartment 35, associated with the bearing frame 2 and positioned on top of the second section 17.

The electric windings 36 are fastened to the holding plane 37.

The electric windings 36 are adapted to be crossed by a second electric current to generate the second electromagnetic field 34.

The second electromagnetic field 34 generated around each electric winding 36 has maximum intensity in the immediate vicinity of the axis of magnetization M and tends to fade as one moves away from the electric windings 36 themselves. The ceramic ink 24 previously polarized and positioned on the exposed face 21 is affected by the presence of the second electromagnetic field 34 and, therefore, is attracted towards the laying face 20 thus distributing itself through the thickness of the tile 19.

Conveniently, the special conformation of the housing compartment 35 allows the electric windings 36 to be positioned in the immediate vicinity of the forward section 14 and, therefore, allows the intensity of the second electromagnetic field 34 to remain high at the forward section 14 thus exerting a greater force of attraction than the ceramic ink 24 polarized downwards.

The digital printer 1 comprises a management and control unit 38 through which an operator can manage the operation of the digital printer 1 itself. Conveniently, the digital printer 1 comprises vibrating movement means of the plane of forward movement 5 associated with the bearing frame 2.

The vibrating movement means comprise a vibrator adapted to shake the plane of forward movement 5 moving it alternately along two opposite directions and both substantially horizontal and transverse to the direction of forward movement L.

The vibrator facilitates the distribution and penetration of the ceramic ink 24 through the thickness of the tile 19.

To further increase the penetration inside the tile 19, the ceramic ink 24 can be advantageously intended to be a penetrating soluble ink.

Penetrating soluble ink means a chromophore substance of the Sinkmet® type, developed by Metco S.r.l. company and able to penetrate for several millimetres into the medium, so that it can be lapped under pressure.

In order to facilitate the penetration of the penetrating soluble ink into the tile 19, moreover, the ceramic material of the tile 19 can be added with carrier agents, such as chromophore promoters of the METOX series, always produced by Metco S.r.l. company.

An alternative embodiment is provided of the digital printer 1 (not shown in the figures) in which the printing heads 22 are not fastened to the bearing frame 2.

In this case, the printing heads 22 are associated with the bearing frame 2 in a sliding manner along a direction of sliding which is horizontal and transverse to the direction of forward movement L. In this particular embodiment, the digital printer 1 comprises at least one rail associated with the bearing frame 2 and housed on top of the forward section 14 in a transverse position with respect to the forward section 14 itself.

The printing heads 22 are moved along the rail according to the direction of sliding.

This way, each printing head 22 sprays the ceramic ink 24 on different portions of the exposed face 21 as the tile 19 is moved according to the direction of forward movement L.

Again, an alternative embodiment of the digital printer 1 (not shown in the figures) is provided in which the electric windings 36 are not attached to the bearing frame 2.

In this case, the electric windings 36 are associated with the bearing frame 2 in a sliding manner along a direction of travel which is horizontal and transverse to the direction of forward movement L.

In this particular embodiment the digital printer 1 comprises motor-driven rolling elements positioned below the holding plane 37 and associated in rotation with the bearing frame 2.

The holding plane 37 is associated in a sliding manner on the rolling elements, which, by rotating, move the plane along the direction of travel.

This way, the electric windings 36 travel with respect to the forward section 14 and the polarized ceramic ink 24 is more influenced by the second electromagnetic field 34, which is movable below the forward section 14.

It should be noted that there are also embodiments in which both the electric windings 36 and the printing heads 22 are sliding with respect to the forward section 14 and, more precisely, the travel of the printing heads 22 according to the direction of sliding and the travel of the electric windings 36 according to the direction of travel take place simultaneously and in synchrony.

This way, as the polarized ceramic ink 24 is deposited on the exposed face 21 by a printing head 22, it is drawn towards the exposed face 21 by a respective electric winding 36 placed below the printing head itself and moving simultaneously therewith.