Plant and method for the production of slabs comprising ceramic material

Abstract

There are described a method and a plant (1; 1*; 1**) for the production of ceramic slabs (CP) with a conveyor device (2; 2*; 2** ) for conveying a plurality of base ceramic slabs (BCS), each having at least one surface (10) to be decorated, along a path (P) in a moving direction (A); at least one decoration station (12; 12*; 12** ) arranged along said path (P) and comprising a first application assembly (15; 15*; 15**) designed to apply a first layer (16) on the surface (10) to be decorated and comprising a preferably digital depositing member; a kiln (17; 17*; 7 ** ) arranged along the path (P) downstream of the decoration station (12; 12*; 12**) and configured to set a temperature ranging from at least circa 1000° C to at least circa 1300 °C for each base ceramic slab (BCS) so as to fire it; and an electrostatic application station (11; 11*; 11**; 18; 18*; 18**) which is arranged along the path (P), designed to apply a second layer (13; 19) consisting of a powder covering material and comprising an electrostatic application unit (22).

Description

[0001] PLANT AND METHOD FOR THE PRODUCTION OF SLABS COMPRISING CERAMIC MATERIAL

[0002] Cross-Reference to Related Applications

[0003] This Patent Appl ication claims priority from Italian Patent Application No . 102022000025236 filed on December 07 , 2022 , the entire disclosure of which is incorporated herein by reference .

[0004] Field of the Art

[0005] The present invention relates to a plant and a method for the production of slabs comprising ceramic material .

[0006] Prior Art

[0007] In the field of the production of ceramic articles , in particular of large-si zed ceramic slabs , i . e . of the type having at least one side with a length equal to or greater than 100 ( one hundred) centimetres , the plants of known type usually comprise a conveyor assembly which in a substantially continuous manner supplies a layer of ceramic powder material from an inlet station towards a station comprising a compaction machine . Downstream o f the compaction machine there is provided a cutting station to obtain a plurality of slabs of compacted ceramic powder ( i . e . a plurality of base or "raw" ceramic slabs ) .

[0008] The base ceramic slabs exiting the cutting station are then supplied to a decoration system comprising a drier which is configured to heat the base ceramic slabs up to a temperature of at least circa 100 ° C and a glazing station, arranged immediately downstream of the drier and comprising an airless booth to apply an even layer of liquid enamel so as to even out the surface to be decorated of the dried base ceramic slabs . The ceramic base slabs exiting the glazing station are then supplied to a number of decoration stations comprising respective printing, alternatively digital or inkj et assemblies , to apply decoration layers on the layer of liquid enamel so as to reproduce a predetermined decoration design or pattern on the surface to be decorated . Finally, the plant comprises a kiln arranged downstream of the decoration stations to sinter the base ceramic slabs so as to obtain the finished ceramic slabs .

[0009] The glazing stations of known type have some drawbacks , though in particular deriving from the fact that these glazing stations mostly use liquid enamels made with an aqueous suspension, for example at 33% water .

[0010] Firstly, for the preparation of the liquid enamels made with an aqueous suspension, dedicated preparation stations are necessary which have considerable overall dimensions and require a non-negligeable use of labour . Typically, said liquid enamel preparation stations comprise at least one discontinuous mill for the preparation of a granular material , pumping members and a plurality of sieving and storage devices arranged in succession to each other and which produce a non-negligible amount of scrap destined for disposal or other material that cannot be recycled in the production of the liquid enamels .

[0011] Furthermore , the glazing stations of known type are designed to apply a layer of liquid enamel on already dried base ceramic slabs and having a temperature ranging from circa 70 ° C to circa 90 ° C . A portion of the water contained in the liquid enamel must in fact be absorbed by the base ceramic slabs whilst the remaining portion of water evaporates to allow the subsequent decoration step and all this would not be possible i f the base ceramic slabs were cold or in any case at temperatures below 70 ° C . It is therefore absolutely necessary that the glazing station is arranged near the drier ( to allow the ceramic base slabs to be suf ficiently hot ) but at a certain distance from the decoration system ( to allow the portion of water to evaporate ) , preferably with interposition of fans to speed up the evaporation step .

[0012] Documents DE4239541 and WO2014174329 describe methods for the production of slabs comprising ceramic material provided with an electrostatic application station . Document WO2022137075 also describes a method for the production of ceramic slabs with an electrostatic application step during which a layer consisting of a powder covering material is applied indirectly, i . e . through interposition of a transfer body, on the surface to be decorated in the area of an electrostatic application station .

[0013] Disclosure of the Invention

[0014] Aim of the present invention is therefore to provide a plant for the production of slabs comprising ceramic material , which plant is free of the drawbacks of the state of the art and is at the same time easy and economical to manufacture .

[0015] A further aim of the present invention is to provide a method for the production of slabs comprising ceramic material , which method is free from the drawbacks of the state of the art and is at the same time easy and economical to implement .

[0016] In accordance with the present invention there are provided a plant and a method for the production of slabs comprising ceramic material according to what is claimed in the appended claims . The claims describe preferred embodiments of the present invention forming an integral part of the present disclosure .

[0017] Brief Description of the Drawings

[0018] The invention wi ll now be described with reference to the accompanying drawings , which show some non-limiting examples of embodiments , wherein :

[0019] Figure 1 is a side and schematic view of a first embodiment of a plant for the production of slabs o f ceramic material reali zed in accordance with the present invention;

[0020] Figure 2 is a schematic side view of a slab of ceramic material reali zed in accordance with the present invention;

[0021] Figure 3 is a perspective view of an electrostatic application station of the plant of Figure 1 ;

[0022] Figure 4 shows an enlarged detail of the electrostatic application station of Figure 3 ;

[0023] Figure 5 is a side and schematic view of a second embodiment of a plant for the production of slabs o f ceramic material reali zed in accordance with the present invention; and

[0024] Figure 6 is a side and schematic view of a third embodiment of a plant for the production of slabs o f ceramic material reali zed in accordance with the present invention .

[0025] Preferred Embodiments of the Invention

[0026] In Figure 1 , number 1 denotes as a whole a plant for the reali zation of a ceramic slab CP . Preferably, the ceramic slab 2 is of the type having at least one side with a length equal to or greater than 100 ( one hundred) centimetres .

[0027] The plant 1 comprises a conveyor assembly 2 comprising a belt conveyor 3 to supply ( in a substantially continuous manner ) a layer LPM of ceramic powder material along an initial stretch o f a path P in a moving direction A from an inlet station 4 towards a processing station 5 . The processing station 5 comprises a compaction machine 6 ( of known type and not described in detail ) adapted to compact the layer LPM of ceramic powder material so as to obtain a continuous plate SPM of compacted ceramic powder .

[0028] The plant 1 comprises a cutting station 7 arranged along the path P, downstream of the processing station 5 . The cutting station 7 is intended to cut transversely to the moving direction A the continuous plate SPM of compacted ceramic powder so as to obtain a plurality of slabs BCS of compacted ceramic powder ( i . e . a plurality of base or "raw" ceramic slabs BCS ) .

[0029] The conveyor assembly 2 then comprises a conveyor belt

[0030] 8 which receives the base ceramic slabs BCS exiting from the cutting station 7 and supplies them to a decoration system

[0031] 9 along the path P for the decoration of the base ceramic slabs BCS .

[0032] In particular, each base ceramic slab BCS is provided with a surface 10 to be decorated, defined by the surface that is intended, in use , to be visible ( i . e . exposed) ; in particular, the surface 10 to be decorated is the surface facing upwards during the conveying by means of the conveyor assembly 2 . In other words , sti ll , the surface 10 to be decorated is substantially parallel to the conveying plane defined by the conveyor assembly 2 , but is not in direct contact with the conveying plane while moving along the path P .

[0033] The conveyor belt 8 is configured to convey the base ceramic slabs BCS along an intermediate stretch of the path, downstream of the initial stretch, through the decoration system 9 ; in particular, through an electrostatic application station 11 and through a decoration station 12 .

[0034] The electrostatic application station 11 is adapted to apply on the surface 10 to be decorated a layer 13 consisting of a covering material , in particular a powder enamel . The enamel layer 13 i s applied evenly over the entire surface 10 to be decorated . The electrostatic application station 12 comprises an electrostatic application unit 22 , as better described in the following discussion .

[0035] The plant 1 then comprises a drier 14 arranged along the path P downstream of the electrostatic application station 11 ; the drier 14 is configured to heat the base ceramic slabs BCS up to a temperature of at least circa 100 ° C ( in particular, of at least circa 150 ° C ) .

[0036] The application or decoration station 12 is arranged along the path P downstream of the drier 14 . Advantageously, the decoration station 12 comprises a printing assembly 15 to at least partially apply a layer 16 on the surface 10 to be decorated . Preferably, the printing assembly 15 comprises a digital depositing assembly conf igured to digital ly apply the layer 16 so as to reproduce a predetermined decoration design or pattern on the surface 10 to be decorated . In other words , the printing assembly 15 is made so that the layer 16 defines a design on the surface 10 to be decorated . The layer 16 is preferably made of at least one granular material , comprising grits and / or atomi zed enamels , so as to form a pattern that is at least partially in relief on the surface 10 to be decorated .

[0037] Furthermore , the plant 1 compri ses a kiln 17 arranged along the path P downstream of the decoration station 12 to sinter the base ceramic slabs BCS so as to obtain the finished ceramic slabs CP . In particular, the kiln 17 is configured to set a temperature ranging from at least circa 1000 ° C to at least circa 1300 ° C .

[0038] According to an advantageous but non-limiting embodiment , the decoration system 9 comprises a further electrostatic application station 18 arranged along the path P downstream of the kiln 17 . The electrostatic application station 18 is des igned to apply on the layer 16 a f inal layer 19 comprising a powder covering material ; in particular to cover the decoration formed on the surface 10 to be decorated . Advantageously, the covering material of the final layer 19 can be any powder material , for example a fixing material , or a material such as to provide the surface 10 to be decorated with particular aesthetic properties ( for example particular shine ) and / or functional properties ( for example particular roughness ) . The electrostatic application station 18 comprises an electrostatic application unit 22 , as better described in the following discussion .

[0039] According to a preferred embodiment , the decoration system 9 then comprises an application station 20 , arranged along the path P immediately upstream of the electrostatic application station 11 . The application station 20 comprises a printing assembly 21 to apply a layer of a precursor material ( or primer) on the surface 10 to be decorated . The printing assembly 21 comprises a digital depositing member configured to digitally apply the layer of precursor material evenly over the entire surface 10 to be decorated . The Applicant has veri fied that the precursor material in order to ensure satis factory performance in the subsequent glazing step of the base ceramic slabs BCS must have the following characteristics: a working viscosity ranging from 10 cP to 30 cP, preferably ranging from 15 cP to 25 cP; a percentage of solid material ranging from 10% to 30%, preferably ranging from 15% to 25%; a particle size of the dry fraction ranging from 0.5 pm to 5 pm (microns) , preferably ranging from 1.5 pm to 3.5 pm (microns) ; and that the dispersing medium is aqueous or alternatively solvent-based (esters, fatty acids, glycols) .

[0040] According to what is shown in Figures 3 and 4, the electrostatic application unit 22 comprises a fluidized tank 23, which holds a powder fluidized with air. In particular, the tank 23 is provided with a bottom wall 24 having a plurality of through holes to allow air to enter.

[0041] To the fluidized tank 23 there is connected a pumping member 25 which pumps from the fluidized tank 23 through a cannula 26 and supplies the powder fluidized with air to any number of dispensing devices 27 through respective conduits 28 (even a single dispensing device 27) .

[0042] The electrostatic application process to apply the powders takes place in an application booth 29, preferably made of plastic material and enclosing in its inside the dispensing devices 27. Advantageously, the electrostatic application unit 22 comprises a plurality of dispensing devices 27 (i.e. at least two dispensing devices 27) . Preferably, the plurality of dispensing devices 27 are arranged equally spaced from each other to ensure an even electrostatic application on the surface 10 to be decorated. According to a first variant, the electrostatic application unit 22 comprises three dispensing devices 27 arranged in line .

[0043] According to a further variant, the dispensing devices 27 are at least four, arranged on at least two rows and at least two columns and preferably equally spaced from the adj acent dispensing devices 27 to ensure an even electrostatic application on the surface 10 to be decorated . The dispensing devices 27 are provided with respective axes substantially parallel to each other and transverse to the moving direction A of the base ceramic slabs BCS . In other words , the dispensing devices 27 are provided with respective axes substantially parallel to each other and transverse to the conveying plane defined by the conveyor assembly 2 . Preferably, the dispensing devices 27 are provided with respective axes orthogonal to the conveying plane defined by the conveyor assembly 2 .

[0044] According to a first embodiment , the dispensing devices 27 comprise applying guns 27 . Each applying gun 27 is provided with a high-voltage electrode 29 arranged in the area of a noz zle from which the powders exit . The applying guns 27 are made to electrostatically charge the particles of the powders directed towards the surface 10 to be decorated . The high-voltage electrode 29 generates an electric field and emits electric charges that are trans ferred to the ceramic powders which fall by gravity and are attracted to the surface 10 to be decorated . The electrical charges emitted by the high-voltage electrode 29 can alternatively be positive or negative .

[0045] Alternatively, the dispensing devices 27 comprise triboelectric devices for ceramic powders that exploit the triboelectric ef fect that allows , by means of rubbing ( in particular with a plastic material ) , the trans fer ( in particular, the removal ) of electric charges from the ceramic powders which fall by gravity and are attracted by the surface 10 to be decorated .

[0046] According to a further variant , the dispensing devices 27 comprise rotating cup electrostatic atomi zing devices for ceramic powders .

[0047] More generally, the dispensing devices 27 comprise any type of device configured to allow the electrostatic deposition of the ceramic powders .

[0048] The base ceramic slabs BCS are moved on a conveying device 30 (which is part of the conveyor assembly 2 ) . Preferably, the conveying device 30 is made of metal material . According to a further embodiment , the conveying device 30 is made of plastic material and comprises dispersed metal fibres . According to a further embodiment, the conveying device 30 is made of plastic material or of rubber .

[0049] Advantageously, according to a preferred embodiment variant , the conveying device 30 is not connected to the ground . Alternatively, according to a further possible embodiment variant , the conveying device 30 is connected to the ground .

[0050] Advantageously, the base ceramic slabs BCS moving on the conveying device 30 are connected to the ground .

[0051] Preferably the ground connection ( of the conveying device 30 and / or of the base ceramic slabs BCS moving on the conveying device 30 ) is made by means of at least one brush or roller (not shown) made of conductive material ( such as , for example , graphite ) connected to the conveying device 30 and / or to the base ceramic slabs BCS moving on the conveying device 30 .

[0052] According to a first embodiment, the conveying device comprises a transport belt 30 . According to a further embodiment , the conveying device 30 comprises a roller conveyor or a conveyor with belts .

[0053] The electrostatic application unit 22 then comprises a recovery system, which is designed to remove , preferably by means of suction, excess powders , in particular powders that do not stick to the surface 10 to be decorated (which do not settle on the conveying device 30 ) . The recovery system comprises a suction mouth adapted to suck upwards the powders that are not stuck to the surface 10 to be decorated and to supply them to the fluidi zed tank 23 . Alternatively, the removal device could be configured to remove excess powders by means of blowing .

[0054] Furthermore , according to a preferred embodiment , the electrostatic application unit 22 comprises a removal system 31 , which is designed to remove , preferably by means of scraping, excess powders , in particular powders that are not stuck to the surface 10 to be decorated that settle on the conveying device 30 . The excess powders settling on the conveying device 30 or falling below the conveying device 30 itsel f are recovered and returned to a sieving system which comprises a tank 32 , preferably housed below the conveying device 30 . The excess powders held in the tank 32 are sieved and supplied via a conduit 33 , preferably by pneumatic transport , to a hopper 34 . From the hopper 34 the powders are supplied back to the fluidi zed tank 23 .

[0055] According to a preferred embodiment , the powders used in the electrostatic application unit 22 are obtained by dry grinding and have a particle si ze ranging from 5 pm to 50 pm (microns ) , preferably ranging from 15 pm to 35 pm (microns ) . Advantageously, the aforesaid powders comprise : a percentage ranging from 10% to 30% of glass frit ; a percentage ranging from 0 to 10% of clay; a percentage ranging from 0 to 5% of aluminium oxide (or alumina) ; a percentage ranging from 0 to 10% of zirconium oxide; a percentage ranging from 0 to 5% of quartz sands; a percentage ranging from 20% to 50% of feldspars; a percentage ranging from 0 to 10% of calcium carbonate; and further additives to increase the flowability and modify the surface charge.

[0056] In Figure 5, a second embodiment of the plant 1* is shown which comprises a conveyor assembly 2* having a belt conveyor 3* to supply (in a substantially continuous manner) a layer LPM of ceramic powder material along an initial stretch of a path P in a moving direction A from an inlet station 4* towards a processing station 5*. The processing station 5* comprises a compaction machine 6* (of known type and not described in detail) adapted to compact the layer LPM of ceramic powder material so as to obtain a continuous plate SPM of compacted ceramic powder.

[0057] The plant 1 comprises a cutting station 7* arranged along the path P, downstream of the processing station 5* . The cutting station 7* is intended to cut transversely to the moving direction A the continuous plate SPM of compacted ceramic powder so as to obtain a plurality of slabs BCS of compacted ceramic powder (i.e. a plurality of base or "raw" ceramic slabs BCS) .

[0058] The conveyor assembly 2* then comprises a conveyor belt 8* which receives the base ceramic slabs BCS exiting from the cutting station 7* and supplies them to a decoration system 9* along the path P for the decoration of the base ceramic slabs BCS.

[0059] In particular, each base ceramic slab BCS is provided with a surface 10 to be decorated, defined by the surface that is intended, in use, to be visible (i.e. exposed) ; in particular, the surface 10 to be decorated is the surface facing upwards during the conveying by means of the conveyor assembly 2 . In other words , still , the surface 10 to be decorated is substantially parallel to the conveying plane defined by the conveyor assembly 2 * , but is not in direct contact with the conveying plane while moving along the path P .

[0060] The conveyor belt 8 * is configured to convey the base ceramic slabs BCS along an intermediate stretch of the path, downstream of the initial stretch, through the decoration system 9* . The plant 1 comprises a drier 14 * arranged along the intermediate stretch of the path P, immediately downstream of the cutting station 7 * . The drier 14 * is configured to heat the base ceramic slabs BCS up to a temperature of at least circa 100 ° C ( in particular, of at least circa 150 ° C ) .

[0061] The decoration system 9* comprises an electrostatic application station 11 * designed to apply on the surface 10 to be decorated a layer 13 consisting of a covering material , in particular a powder enamel . The enamel layer 13 is applied evenly over the entire surface 10 to be decorated . The electrostatic application station 11 * comprises an electrostatic application unit 22 * , of the type described in the preceding discussion . The electrostatic application station 11 * is arranged along the path P, downstream of the drier 14 * .

[0062] The decoration system 9* then comprises an application station 20* , arranged along the path P immediately upstream of the electrostatic application station 11 * . In other words , the application station 20* is interposed between the drier 14 * and the electrostatic application station 11 * . The application station 20* comprises a printing assembly 21* to apply a layer of a precursor material (or primer) on the surface 10 to be decorated. The printing assembly 21* comprises a digital depositing member configured to digitally apply the layer of precursor material evenly over the entire surface 10 to be decorated. Said layer consisting of a precursor material is necessary to allow the subsequent glazing step of the dried base ceramic slabs BCS . The Applicant has verified that the precursor material in order to ensure satisfactory performance in the subsequent glazing step of the dried base ceramic slabs BCS must have the following characteristics: a working viscosity ranging from 10 cP to 30 cP, preferably ranging from 15 cP to 25 cP; a percentage of solid material ranging from 10% to 30%, preferably ranging from 15% to 25%; a particle size of the dry fraction ranging from 0.5 pm to 5 pm (microns) , preferably ranging from 1.5 pm to 3.5 pm (microns) ; and that the dispersing medium is aqueous or alternatively solventbased (esters, fatty acids, glycols) .

[0063] According to a possible variant, the decoration system 9* comprises a glazing apparatus that integrates in its inside both the printing assembly 21* for the application of the precursor material and the electrostatic application unit 22* .

[0064] The decoration system 9* then comprises a decoration station 12*, arranged along the path P downstream of the electrostatic application station 11*. The decoration station 12* comprises a printing assembly 15* to at least partially apply a layer 16 on the surface 10 to be decorated. Preferably, the printing assembly 15* comprises a digital depositing assembly configured to digitally apply the layer 16 so as to reproduce a defined predetermined decoration design or pattern on the surface 10 to be decorated. In other words, the printing assembly 15* is made so that the layer 16 defines a design on the surface 10 to be decorated.

[0065] Finally, the plant 1 comprises a kiln 17* arranged along the path P downstream of the decoration station 12* to sinter the base ceramic slabs BCS so as to obtain the finished ceramic slabs CP. In particular, the kiln 17* is configured to set a temperature ranging from at least circa 1000 °C to at least circa 1300 °C.

[0066] According to an advantageous but non-limiting embodiment, the decoration system 9* comprises a further electrostatic application station 18* arranged along the path P downstream of the kiln 17*. The electrostatic application station 18* is designed to apply on the layer 16 a final layer 19 comprising a powder covering material; in particular to cover the design formed on the surface 10 to be decorated. Advantageously, the covering material of the final layer 19 can be any powder material, for example a fixing material, or a material such as to provide the surface 10 to be decorated with particular aesthetic properties (for example particular shine) and / or functional properties (for example particular roughness) .

[0067] In Figure 6, a third embodiment of the plant 1 is shown which comprises a conveyor assembly 2** comprising in turn a belt conveyor 3** to supply (in a substantially continuous manner) a layer LPM of ceramic powder material along an initial stretch of a path P in a moving direction A from an inlet station 4** towards a processing station 5**. The processing station 5** comprises a compaction machine 6** (of known type and not described in detail) adapted to compact the layer LPM of ceramic powder material so as to obtain a continuous plate SPM of compacted ceramic powder.

[0068] The plant 1 comprises a cutting station 7** arranged along the path P, downstream of the processing station 5**. The cutting station 7** is intended to cut transversely to the moving direction A the continuous plate SPM of compacted ceramic powder so as to obtain a plurality of slabs BCS of compacted ceramic powder (i.e. a plurality of base or "raw" ceramic slabs BCS) .

[0069] The conveyor assembly 2** then comprises a conveyor belt 8** which receives the base ceramic slabs BCS exiting from the cutting station 7** and supplies them to a decoration system 9** along the path P for the decoration of the base ceramic slabs BCS.

[0070] In particular, each base ceramic slab BCS is provided with a surface 10 to be decorated, defined by the surface that is intended, in use, to be visible (i.e. exposed) ; in particular, the surface 10 to be decorated is the surface facing upwards during the conveying by means of the conveyor assembly 2**. In other words, still, the surface 10 to be decorated is substantially parallel to the conveying plane defined by the conveyor assembly 2**, but is not in direct contact with the conveying plane while moving along the path P.

[0071] The conveyor belt 8** is configured to convey the base ceramic slabs BCS along an intermediate stretch of the path, downstream of the initial stretch, through the decoration system 9**; in particular, through an electrostatic application station 11** and a decoration station 12**.

[0072] The electrostatic application station 11 is adapted to apply on the surface 10 to be decorated a layer 13 consisting of a covering material, in particular an enamel. The enamel layer 13 is applied evenly over the entire surface 10 to be decorated. The electrostatic glazing station 12** comprises an electrostatic application unit 22**, as better described in the preceding discussion.

[0073] The decoration station 12** is arranged along the path P downstream of the electrostatic application station 11**. The decoration station 12** comprises a printing assembly 15** to at least partially apply a layer 16 on the surface 10 to be decorated. Preferably, the printing assembly 15** comprises a digital depositing assembly configured to digitally apply the layer 16 so as to reproduce a predetermined decoration design or pattern on the surface 10 to be decorated. In other words, the printing assembly 15** is made so that the layer 16 defines a design on the surface 10 to be decorated.

[0074] Finally, the plant 1 comprises a kiln 17** arranged along the path P downstream of the decoration station 12** to sinter the base ceramic slabs BCS so as to obtain the finished ceramic slabs CP. In particular, the kiln 17** is configured to set a temperature ranging from at least circa 1000 °C to at least circa 1300 °C.

[0075] According to an advantageous but non-limiting embodiment, the decoration system 9** comprises a further electrostatic application station 18** arranged along the path P downstream of the kiln 17**. The electrostatic application station 18** is designed to apply on the layer 16 a final layer 19 comprising a powder covering material; in particular to cover the decoration formed on the surface 10 to be decorated. Advantageously, the covering material of the final layer 19 can be any powder material, for example a fixing material, or a material such as to provide the surface 10 to be decorated with particular aesthetic properties (for example particular shine) and / or functional properties (for example particular roughness) .

[0076] According to a preferred variant, the plant 1 then comprises a drier 14** arranged along the path P immediately upstream of the kiln 17** and downstream of the decoration station 12**, configured to heat the base ceramic slabs BCS up to a temperature of at least circa 100 °C (in particular, of at least circa 150 °C) and supply them to the kiln 17**. According to a possible variant, the plant 1** comprises a firing apparatus that integrates in its inside both the drier 14** and the kiln 17**, so as to substantially reduce the path of the base ceramic slabs BCS and the overall dimensions of the plant 1**.

[0077] According to a preferred embodiment, the decoration system 9** then comprises an application station 20**, arranged along the path P immediately upstream of the electrostatic application station 11**. The application station 20** comprises a printing assembly 21** to apply a layer of a precursor material (or primer) on the surface 10 to be decorated. The printing assembly 21** comprises a digital depositing member configured to digitally apply the layer of precursor material evenly over the entire surface 10 to be decorated. The Applicant has verified that the precursor material in order to ensure satisfactory performance in the subsequent glazing step of the base ceramic slabs BCS must have the following characteristics: a working viscosity ranging from 10 cP to 30 cP, preferably ranging from 15 cP to 25 cP; a percentage of solid material ranging from 10% to 30%, preferably ranging from 15% to 25%; a particle size of the dry fraction ranging from 0.5 pm to 5 pm (microns) , preferably ranging from 1.5 pm to 3.5 pm (microns) ; and that the dispersing medium is aqueous or alternatively solvent-based (esters, fatty acids, glycols) .

[0078] The electrostatic application unit 22 described in the preceding discussion may find advantageous application in any electrostatic application station 11, 11*, 11**, 18, 18*, 18** described above.

[0079] In accordance with a further aspect of the present invention, there is also provided a method for the production of slabs CP comprising ceramic material.

[0080] The method comprises a first processing step during which a layer LPM of powder material comprising ceramic powder is processed by at least one compaction machine 6 arranged in the area of a workstation 5 to compact the layer LPM of powder material so as to obtain a continuous plate LPM of compacted powder.

[0081] The method further comprises a moving step, during which the continuous plate LPM of compacted powder is moved by a conveyor assembly 2 along a path P in a moving direction A from the workstation 5 through a cutting station 7 in which to obtain base ceramic slabs BCS, wherein each base ceramic slab BCS is provided with a surface 10 to be decorated, which is intended, in use, to be visible, i.e. exposed.

[0082] According to a first embodiment shown in Figure 1, the method then comprises a first electrostatic application step of the base ceramic slabs BCS, carried out in the area of an electrostatic application station 11 arranged along the path P downstream of the cutting station 7 and wherein an even layer 13 consisting of a covering material, in particular a powder enamel, is applied on the surface 10 to be decorated. The method then comprises a drying step, which is subsequent to the first electrostatic application step, during which each base ceramic slab BCS is dried inside a drier 14 arranged downstream of the electrostatic application station 11 along the path P .

[0083] The method then comprises an application step, carried out in the area of a decoration station 12 arranged downstream of the drier 14 along the path P and comprising a printing assembly 15 to at least partially apply a layer 16 on the surface 10 to be decorated . Preferably, the printing assembly 15 comprises a digital depositing assembly configured to digitally apply the layer 16 so as to reproduce a predetermined decoration design or pattern on the surface 10 to be decorated .

[0084] The method then comprises a firing step, during which each base ceramic slab BCS is fired in a kiln 17 arranged downstream of the decoration station 12 along the path P so as to obtain a finished ceramic slab CP .

[0085] Finally, according to a possible variant , the method comprises a second electrostatic application step of the finished ceramic slabs CP, carried out in the area of an electrostatic application station 18 arranged downstream of the kiln 17 along the path P .

[0086] According to a second embodiment shown in Figure 5 , the method comprises a drying step, which is subsequent to the first cutting step, during which each base ceramic slab BCS is dried inside a drier 14 * arranged downstream of the cutting station 7 * along the path P .

[0087] The method then comprises a first application step, carried out in the area of an application station 20* arranged downstream of the drier 14 * along the path P and comprising a printing assembly 21 * comprising a digital depositing assembly configured to digitally apply a precursor material on the surface 10 to be decorated .

[0088] Subsequently, the method comprises a first electrostatic application step of the base ceramic slabs BCS , carried out in the area of an electrostatic application station 11 * arranged along the path P downstream of the application station 20* and wherein an even layer 13 consisting of a covering material , in particular a powder enamel , is applied on the surface 10 to be decorated .

[0089] The method then comprises a second application step, carried out in the area of a decoration station 12 * arranged downstream of the electrostatic application station 11 * along the path P and comprising a printing assembly 15* to at least partially apply a layer 16 on the surface 10 to be decorated . Preferably, the printing assembly 15* comprises a digital depositing assembly conf igured to digital ly apply the layer 16 so as to reproduce a predetermined decoration design or pattern on the surface 10 to be decorated .

[0090] The method then comprises a firing step, during which each base ceramic slab BCS is fired in a kiln 17 * arranged downstream of the decoration station 12 * along the path P so as to obtain a finished ceramic slab CP .

[0091] Finally, according to a possible variant , the method comprises a second electrostatic application step of the finished ceramic slabs CP, carried out in the area of an electrostatic application station 18 * arranged downstream of the kiln 17 along the path P .

[0092] According to a third embodiment shown in Figure 6 , the method then comprises a first electrostatic application step of the base ceramic slabs BCS , carried out in the area of an electrostatic application station 11 * * arranged along the path P downstream of the cutting station 7* * and wherein an even layer 13 consisting of a covering material , in particular a powder enamel , is applied on the surface 10 to be decorated .

[0093] The method then comprises a second application step, carried out in the area of a decoration station 12 * * arranged downstream of the electrostatic application station 11 * * along the path P and comprising a printing assembly 15* * to at least partially apply a layer 16 on the surface 10 to be decorated . Preferably, the printing assembly 15* * comprises a digital depositing assembly conf igured to digital ly apply the layer 16 so as to reproduce a defined predetermined decoration design or pattern on the surface 10 to be decorated .

[0094] The method then comprises a firing step, during which each base ceramic slab BCS is fired in a kiln 17 * * arranged downstream of the decoration station 12 * * along the path P so as to obtain a finished ceramic slab CP . Advantageously, the method comprises a drying step, which is subsequent to the decoration step and prior to the firing step, during which each base ceramic slab BCS is dried inside a drier 14 * * arranged downstream of the decoration station 12 * * ( and upstream of the kiln 17 * * ) along the path P .

[0095] According to a possible embodiment not shown, the application stations 20 , 20* , 20* * comprise an application assembly to apply a layer of a fixing and protective material on the surface 10 to be decorated . In particular, said application assembly comprises a preferably digital printing member, configured to digitally apply the layer of fixing and protective material evenly over the entire surface 10 to be decorated. Said printing assembly to apply the layer of a fixing and protective material can be provided in combination or alternatively to the printing assembly 21, 21*, 21** to apply the layer of a precursor material (or primer) .

[0096] Finally, according to a possible variant, the method comprises a second electrostatic application step of the finished ceramic slabs CP, carried out in the area of an electrostatic application station 18** arranged downstream of the kiln 17** along the path P.

[0097] It is important to highlight that the electrostatic application unit 22 allows to apply directly (i.e., without interposition of further applying devices or elements) and evenly the layer 13, 19 consisting of a powder covering material on the surface 10 to be decorated in the area of the electrostatic application station 11; 11*; 11**; 18; 18*; 18**.

[0098] The object of the present invention has several advantages over the state of the art. In particular, the electrostatic application stations 11; 11*; 11**; 18; 18**; 18** described in the preceding discussion are suitable for the even application of layers 13, 19 consisting of a powder covering material both on compacted ceramic powder slabs (i.e. base or "raw" ceramic slabs BCS) , and on dried base ceramic slabs BCS, and on finished ceramic slabs CP. In other words, said electrostatic application stations 11; 11*; 11**; 18; 18*; 18** can be arranged along the path P in a multiplicity of points (in particular, upstream or downstream of the drier 14, 14*, 14**) allowing to obtain an extreme versatility and compactness of the plant 1 in addition to smaller overall dimensions compared to the plants of the prior art.

[0099] LIST OF REFERENCE NUMBERS OF THE FIGURES

[0100] I,1*, 1** plant

[0101] 2, 2*, 2** conveyor assembly

[0102] 3, 3*, 3** conveyor belt

[0103] 4, 4*, 4** inlet station

[0104] 5, 5*, 5** workstation

[0105] 6, 6*, 6** compaction machine

[0106] 7, 7*, 7** cutting station

[0107] 8, 8*, 8** conveyor belt

[0108] 9, 9*, 9** decoration system

[0109] 10 surface to be decorated

[0110] II, 11*, 11** electrostatic application station

[0111] 12, 12*, 12** decoration station

[0112] 13 enamel layer

[0113] 14, 14*, 14** drier

[0114] 15, 15*, 15** printing assembly

[0115] 16 layer

[0116] 17, 17*, 17** kiln

[0117] 18, 18*, 18** electrostatic application station

[0118] 19 layer

[0119] 20, 20*, 20** application station

[0120] 21, 21*, 21** printing assembly

[0121] 22 electrostatic application unit

[0122] 23 fluidized tank

[0123] 24 bottom panel

[0124] 25 pumping member

[0125] 26 cannule

[0126] 27 dispensing device

[0127] 28 conduits 29 electrode

[0128] 30 conveying device

[0129] 31 removal system

[0130] 32 tank

[0131] 33 conduit

[0132] 34 hopper

[0133] CP ceramic slab

[0134] LPM layer of ceramic powder material

[0135] P path

[0136] A moving direction

[0137] SPM plate of compacted powder material

[0138] BCS base ceramic slab

Claims

CLAIMS1.- A plant (1; 1*; 1**) for the production of ceramic slabs (CP) , in particular of the type having at least one side with a length equal to or greater than one hundred centimetres; said plant comprises: a conveyor device (2; 2*; 2**) to convey a plurality of base ceramic slabs (BCS) , each having a surface (10) to be decorated, along a path (P) in a moving direction (A) ; at least one decoration station (12; 12*; 12**) arranged along said path (P) and comprising a first application assembly (15; 15*; 15**) , in particular a printing assembly (15; 15*; 15**) , designed to apply a first layer (16) on the surface (10) to be decorated and comprising a, preferably digital, depositing member; a kiln (17; 17*; 17**) arranged along the path (P) downstream of the decoration station (12; 12*; 12**) in the moving direction (A) and configured to set a temperature ranging from at least circa 1000 °C to at least circa 1300 °C for each base ceramic slab (BCS) in order to fire it; and an electrostatic application station (11; 11*; 11**; 18; 18*; 18**) arranged along the path (P) , designed to apply a second layer (13; 19) consisting of a powder covering material and comprising an electrostatic application unit (22) evenly to the surface (10) to be decorated; the plant is characterized in that the electrostatic application unit (22) comprises a fluidized tank (23) , which holds the powder covering material fluidized with air, and at least one pumping member (25) , which pumps from the fluidized tank (23) and supplies the powder covering material fluidized with air to a plurality of dispensing devices (27) ; and wherein the dispensing devices (27) are provided withrespective axes transverse to the moving direction (A) and are arranged, in use, so as to face the surface (10) to be decorated .2.- The plant according to claim 1, wherein the dispensing devices (27) are arranged equally spaced from each other to ensure an even electrostatic application on the surface (10) to be decorated.3.- The plant according to claim 1 or 2, wherein the conveyor device (2; 2*; 2**) comprises a conveying device (30) arranged in the area of the electrostatic application station (11; 11*; 11**; 18; 18*; 18**) ; preferably, the conveying device (30) is made of metal material or plastic material with dispersed metal fibres or of a plastic material or of rubber.4.- The plant according to claim 3, wherein the conveying device (30) is not connected to the ground.5.- The plant according to claim 3 or 4, wherein the base ceramic slabs (BCS) moving on the conveying device (30) are connected to the ground.6.- The plant according to any one of claims 3 to 5, wherein the electrostatic application unit (22) comprises a removal system (31) , which is designed to remove, preferably by means of scraping, excess powders that do not stick to the surfaces (10) to be decorated and settle on the conveying device (30) and which supplies the recovered powders to the fluidized tank (23) .7.- The plant according to any one of claims 3 to 6, wherein the electrostatic application unit (22) comprises a recovery system, which is designed to remove, preferably by means of suction or blowing, excess powders that do not stick to the surfaces (10) to be decorated and do not settle onthe conveying device (30) and supply them to the fluidized tank (23) .8.- The plant according to any one of claims 3 to 7, wherein the conveying device (30) comprises a transport belt (30) and / or a roller conveyor and / or a conveyor with belts.9.- The plant according to any one of the preceding claims, wherein at least one dispensing device (27) comprises an applying gun (27) having a nozzle in the area of which it is provided with a respective high-voltage electrode (29) .10.- The plant according to any one of the preceding claims, wherein at least one dispensing device (27) comprises a triboelectric device for ceramic powders.11.- The plant according to any one of the preceding claims, wherein at least one dispensing device (27) comprises a rotating cup electrostatic atomizing device for ceramic powders .12.- The plant according to any one of the preceding claims, wherein the electrostatic application station (18; 18*; 18**) is arranged downstream of the kiln (17; 17*; 17**) in the moving direction (A) for the application of the second layer (19) on the first layer (16) .13.- The plant according to any one of the preceding claims, wherein the electrostatic application station (11; 11*; 11**) is arranged upstream of the decoration station (12; 12*; 12**) in the moving direction (A) for the electrostatic application of the second layer (13) comprising a powder covering material, in particular an enamel or a slip, on the surface (10) to be decorated.14.- The plant according to claim 13 and comprising a drier (14) which is arranged along the path (P) upstream of the decoration station (12) in the moving direction (A) andis configured to heat each base ceramic slab (BCS) to a temperature of at least circa 100 °C; wherein the electrostatic application station (11) is arranged upstream of the drier (14) in the moving direction (A) .15.- The plant according to claim 13 and comprising a drier (14*) which is arranged along the path (P) upstream of the decoration station (12*) in the moving direction (A) and is configured to heat each base ceramic slab (BCS) to a temperature of at least circa 100 °C; wherein the electrostatic application station (11*) is arranged downstream of the drier (14*) in the moving direction (A) .16.- The plant according to claim 14 or 15 and comprising an application station (20*) arranged along said path (P) immediately upstream of the electrostatic application station (11*) in the moving direction (A) and comprising a second application assembly (21*) , in particular a second printing assembly (21*) , to apply a layer of a precursor material on the surface (10) to be decorated with a preferably digital depositing member.17.- The plant according to claim 13 and comprising a drier (14**) which is arranged along the path (P) , interposed between the decoration station (12**) and the kiln (17**) and is configured to heat each base ceramic slab (BCS) to a temperature of at least circa 100 °C.18.- The plant according to claim 17 and comprising an application station (20**) arranged along said path (P) immediately upstream of the electrostatic application station (11**) in the moving direction (A) and comprising a second application assembly (21**) , in particular a second printing assembly (21**) , to apply a layer of a precursor material on the surface (10) to be decorated with apreferably digital depositing member.19.- A method for the production of ceramic slabs (CP) , in particular of the type having at least one side with a length equal to or greater than one hundred centimetres; said method comprises: a moving step, during which a conveyor device (2; 2*; 2**) supplies a plurality of base ceramic slabs (BCS) , each having a surface (10) to be decorated, along a path (P) in a moving direction (A) ; a decoration step during which a first application assembly (15; 15*; 15**) arranged in the area of a decoration station (12; 12*; 12**) along said path (P) applies a first layer (16) on the surface (10) to be decorated by means of a preferably digital depositing member; and a firing step, which is subsequent to the decoration step, during which each base ceramic slab (BCS) is fired in a kiln (17; 17*; 17**) which is arranged along the path (P) downstream of the decoration station (12; 12*; 12**) in the moving direction (A) and configured to set a temperature ranging from at least circa 1000 °C to at least circa 1300 °C; the method is characterized in that it comprises an electrostatic application step, during which a second layer (13; 19) consisting of a powder covering material is applied directly and evenly on the surface (10) to be decorated in the area of an electrostatic application station (11; 11*; 11**; 18; 18*; 18**) arranged along the path (P) and comprising an electrostatic application unit (22) .20.- The method according to claim 19, wherein the electrostatic application step is subsequent to the firing step .21.- The method according to claim 19, wherein the electrostatic application step is prior to the decoration step .22.- The method according to claim 21 and comprising a drying step, which is prior to the decoration step during which each base ceramic slab (BCS) is dried inside a drier (14) arranged along said path (P) ; wherein the electrostatic application step is prior to the drying step.23.- The method according to claim 21 and comprising a drying step, which is prior to the decoration step during which each base ceramic slab (BCS) is dried inside a drier (14*) arranged along said path (P) ; wherein the electrostatic application step is subsequent to the drying step.24.- The method according to claim 22 or 23 and comprising an application step to apply a layer of a precursor material on the surface (10) to be decorated in the area of an application station (20; 20*) arranged along said path (P) with a preferably digital depositing member; wherein the precursor material layer application step is prior to the electrostatic application step.25.- The method according to claim 22 or 23 or 24 and comprising an application step to apply a layer of a fixing and protective material on the surface (10) to be decorated in the area of an application station arranged along said path (P) with a preferably digital depositing member; wherein the application step to apply the layer of fixing and protective material follows the electrostatic application step .26.- The method according to claim 21 and comprising a drying step interposed between the decoration step and the firing step during which each base ceramic slab (BCS) isdried inside a drier (14**) arranged along said path (P) .27.- The method according to claim 26 and comprising an application step to apply a layer of a precursor material on the surface (10) to be decorated in the area of an application station (20**) arranged along said path (P) with a preferably digital depositing member; wherein the precursor material layer application step is prior to the electrostatic application step.

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