Patent Publication Number: US-2023158542-A1

Title: Method and machine for the surface treatment of a base ceramic article

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims priority from Italian patent application no. 102020000009067 filed on 27 Apr. 2020 and from Italian patent application no. 102020000009070 filed on 27 Apr. 2020, the entire disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     This invention relates to a method and a machine for the surface treatment of a base ceramic article. 
     Specifically, this invention relates to a method and a machine for the surface treatment of slabs comprising (consisting of) ceramic material; even more specifically, of tiles comprising (consisting of) ceramic material. 
     BACKGROUND OF THE INVENTION 
     In the field of ceramic article production, in particular ceramic slabs and tiles, it is known to subject base ceramic articles to surface treatments designed to provide the article with the desired aesthetic, mechanical, and functional properties. 
     The most common surface treatments are treatments to decorate the base ceramic articles. The machines known for the decoration of base ceramic articles are divided into machines for making so-called full-field decorations that affect the entire surface to be treated and machines for making patterns on part of the surface to be treated. Specifically, the machines and the processes for creating the so-called “full field” decorations involve the application of an adhesive material on basically the whole extension of the surface to be treated and, subsequently, the depositing, typically by means of depositing rollers, of a powder material, mainly consisting of ceramic powders, on the adhesive material. 
     On the other hand, the machines and processes for creating patterns on part of the surface to be treated involve the selective application of an adhesive material in certain defined areas of the surface to be treated in order to define the pattern and the subsequent depositing of the powder material on the entire surface to be treated, which thus remains attached to the adhesive material in the above-mentioned defined areas. 
     In both cases, the powder material is spread over the entire extension of the surface to be treated and in a sufficiently abundant manner to form a sufficiently thick and dense layer of powder material and to avoid the risk that areas of the base ceramic element to be decorated remain free of powder material. 
     However, doing so may result in not all of the applied powder material&#39;s coming into contact with the adhesive material and adhering to it. This could be a problem, as the powder material that has not adhered could move during the subsequent treatment steps to which the base ceramic article is subjected, risking soiling the machine and/or areas of the surface to be treated that should remain free of powder material, thus compromising the success of the process of decorating the base ceramic articles and risking damage to the machine for decorating the base ceramic articles. 
     To try to avoid this risk, known processes and machines for surface treatment, and more specifically for decoration, of base ceramic articles involve the removal of powder material that has not adhered (excess material) to the adhesive material, typically by means of suction. Obviously, this entails an additional work station inside the machine with a consequent increase in the number of machine components, the time, and cost of the treatment process and a large amount of powder material waste, which is used in excess, or in any case the need for complex and costly technical devices for a massive recirculation of the powder material that is sucked up. 
     Furthermore, the base ceramic articles treated with the known machines and methods described above often exhibit surface irregularities (i.e., defects), such as variations in thickness and/or density between different areas of the treated surface, caused for example by the non-uniform distribution of the ceramic powder on this surface or, in the case of selective processes (i.e., processes of applying the powder material only to certain defined areas of the surface to be treated), by the alternation of areas treated with the powder material and areas without the powder material. These surface irregularities, in addition to risking compromising the aesthetic appearance of the base ceramic article, may make the smoothing, lapping, polishing, etc. operations, to which the base ceramic article is generally subjected, more laborious and/or less effective. For example, when the treatment processes of the base ceramic articles involve the application of reagents, reinforcers, resins, or other substances to the layer of powder material, if the substrate on which these substances are applied (in the present case, the layer of powder material) is not uniform, on the one hand, the correct distribution of the above-mentioned substances may be impaired and, on the other hand, the above-mentioned surface irregularities may become even more visible. 
     All the drawbacks described above risk making the surface treatment processes of the base ceramic items inefficient and/or compromising the final aesthetic appearance of the ceramic products. 
     The purpose of this invention is to provide a method and a machine for the surface treatment of a base ceramic article, which make it possible to overcome, at least partially, the drawbacks of the prior art, while at the same time being economical and easy to implement/manufacture. 
     SUMMARY 
     In accordance with this invention, a method and a machine for the surface treatment of a base ceramic article are provided, according to what is claimed in the appended independent claims, and preferably, in any one of the claims depending directly or indirectly on the above-mentioned independent claims. 
     The claims describe preferred embodiments of the present invention, forming an integral portion of this description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described below with reference to the accompanying drawings which show some non-limiting embodiments of it, wherein: 
         FIG.  1    is a lateral and schematic view of a production plant for ceramic articles in accordance with this invention; 
         FIGS.  2  to  6    are schematic, lateral views of subsequent operating steps of a part of the plant in  FIG.  1   ; 
         FIGS.  7  to  13    are schematic, lateral views of subsequent operating steps of a different embodiment of the part of the plant illustrated in  FIGS.  2  to  6   ; 
         FIGS.  14  to  18    are lateral views of a base ceramic article subjected to different surface treatments in accordance with different embodiments of this invention; and 
         FIG.  19    is a schematic, perspective view of a detail of the plant in  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG.  1   , the number  1  designates, as a whole, a plant for the manufacture of a ceramic article T. In particular, the ceramic article T is a ceramic slab (more precisely, a ceramic tile). 
     According to some preferred but not exclusive embodiments, such as that illustrated in  FIG.  1   , the plant  1  comprises a conveyor assembly  2  for feeding (basically continuously) a powder material CP comprising (in particular, mainly consisting of) ceramic powder along a path P determined in a feeding direction A from an inlet station  3  towards (through) a compacting machine  4 , configured to compact the powder material CP so as to obtain a compacted powder layer KP, which compacted powder layer KP is also fed along the determined path P towards (through) a machine  5  for the surface treatment of a base ceramic article CB, for example a decoration machine, to an outlet station  6 . Advantageously, the base ceramic article CB comprises (at least) one portion of the compacted powder layer KP and at least one surface to be treated  7 , in particular the surface to be treated  7  is the surface facing upwards (i.e. towards the surface  7  of the base ceramic article CB that is parallel to the conveyor plane but is not in contact with the conveyor assembly  2  during the feeding of the base ceramic article CB on the conveyor assembly  2  itself). 
     According to some non-limiting embodiments such as the one illustrated in  FIG.  1   , the plant  1  comprises at least one cutting assembly  8  for transversely cutting the compacted powder layer KP so as to obtain the above-mentioned base ceramic article CB. In detail, advantageously but not necessarily, the conveyor assembly  2  is specifically configured to feed the compacted powder layer KP to the cutting assembly  8  and to transport the base article CB downstream of the cutting assembly  8  itself through the machine  5  for surface treatment of the base ceramic article CB. 
     According to the preferred but non-limiting embodiment illustrated in  FIG.  1   , the compacting machine  4  and the machine  5  for the surface treatment of the base ceramic article CB are arranged along the path P between the inlet station  3  and the outlet station  6 . Specifically, according to some preferred but not exclusive embodiments such as that illustrated in  FIG.  1   , the machine  5  is arranged downstream of the compacting machine  4 . Even more specifically, the cutting assembly  8  is also arranged along the path P, in particular, downstream of the compacting machine  4  and upstream of the machine  5  for surface treatment of the base ceramic articles CB. 
     According to some non-limiting embodiments that are not illustrated, the plant  1  does not comprise the compacting machine  4  and the cutting assembly  8  but does comprise a conventional (known) tile-pressing machine. Typically, this pressing machine is equipped with a vertical-axis hydraulic pressing device designed to press powder ceramic material in order to directly obtain single slabs (which do not require cutting) of pressed material. 
     According to certain non-limiting embodiments such as the one illustrated in  FIG.  1   , the plant  1  also comprises a dryer  9  arranged along the path P downstream of the compacting machine  4  (more precisely, downstream of the cutting assembly  8 ) and upstream of the machine  5  for the surface treatment of the base ceramic articles CB. Furthermore, in accordance with other non-limiting embodiments such as the one illustrated in  FIG.  1   , the plant  1  comprises (also) a firing kiln  10  for sintering (the compacted powder layer KP of) the base ceramic article CB so as to obtain a ceramic product T. In particular, advantageously but not necessarily, the firing kiln  10  is arranged along the path P determined downstream of the machine  5 . 
     According to some preferred but not exclusive embodiments such as those illustrated in  FIGS.  1  to  13   , the machine  5  comprises a conveying device  11  (which is, in particular, part of the conveyor assembly  2 ) for feeding (preferably, with basically continuous motion) the base ceramic article CB along the path P determined in the feeding direction A through a first application station  12 , a second application station  13 , arranged downstream of the first application station  12 , and at least one third application station  14 , arranged downstream of the second application station  13 . 
     Specifically, in accordance with some preferred but not exclusive embodiments such as those illustrated in  FIGS.  1  to  13   , the machine  5  for the surface treatment of the base ceramic article CB comprises a printing assembly  15 , which is arranged at the first application station  12  and is configured to apply a layer  16  comprising (in particular, consisting of) an adhesive material  17  on at least part of the surface to be treated  7  (see, for example,  FIGS.  3 ,  8   , and  FIGS.  14  to  18   ). 
     Advantageously but not necessarily, the printing assembly  15  comprises an inkjet head (inkjet—not visible in the appended figures and known so not further described herein) configured to emit one or more jets of adhesive material  17  (selectively) onto the surface to be treated  7 . In this case, advantageously but not necessarily, the adhesive material  17  is such (i.e. has a consistency and viscosity such) that it can be applied by means of an inkjet head. 
     In particular, according to some advantageous but not exclusive embodiments, the printing assembly  15  is configured to apply the layer  16  (in particular, selectively) to the surface to be treated  7 , in at least one defined area  18  of the surface to be treated  7 . 
     Specifically, according to some advantageous but non-limiting embodiments such as those illustrated in  FIGS.  14 ,  15 ,  16 , and  18   , the printing assembly  15  applies the layer  16  over basically the whole extension of the surface to be treated  7 . In other words, in these cases the defined area  18  has an extension that basically coincides with the extension of the surface to be treated  7 . 
     Alternatively, in accordance with other non-limiting variants, such as those illustrated in  FIGS.  3 ,  8 , and  17   , the defined area  18  is such that at least one other defined area  19  of the same surface to be treated  7  (in particular, different to the defined area  18 ) remains free of adhesive material  17 . In other words, in this case the extension of the defined area  18  is smaller than the extension of the surface to be treated  7 . 
     According to other non-limiting variants that are not illustrated, the printing assembly  15  is configured to apply (in particular, digitally) the adhesive material  17  so as to reproduce a defined pattern on the surface to be treated  7 . In other words, the printing assembly  15  is configured to apply the adhesive material  17  so that the layer  16  defines a pattern on the surface to be treated  7 . 
     Advantageously, the machine  5  also comprises a depositing assembly  20 , which is arranged at the second application station  13  and is configured to deposit a layer  21  comprising (in particular, consisting of) a powder material  22  on the layer  16  so as to remain adhered to the adhesive material  17  of the layer  16  (see, in particular,  FIGS.  4 ,  9   , and  FIGS.  14  to  18   ). 
     According to some preferred but non-limiting embodiments such as those illustrated in  FIGS.  14  to  17   , this layer  21  of powder material  22  is deposited over the whole extension of the layer  16 . In particular, over the whole defined area  18  on which the adhesive material  17  was previously (i.e., downstream along the determined path P) deposited. 
     Alternatively, according to some advantageous but non-limiting embodiments such as that illustrated in  FIG.  18   , the layer  21  of powder material  22  is selectively deposited on the layer  16  in a part  23  of the defined area  18  so as to remain adhered to the layer  16 . 
     In this case, advantageously but not necessarily, the machine  5  also comprises a control unit  25  (see  FIGS.  2  and  7   ) that is configured to control (in particular, digitally) the depositing assembly  20  so that it deposits the layer  21  of powder material  22  in the part  23  of the defined area  18  so that this layer  21  of powder material  22  remains adhered to the layer  16  and so that it does not cover at least part of the defined area  24  of the surface to be treated  7 . 
     Advantageously, this part  23  of the defined area  18  is such that at least part of another defined area  24  of the surface to be treated  7  (in particular, of the layer  16 ) is not covered by the layer  21  of powder material  22 . 
     Specifically, when the extension of the defined area  18  is smaller than the extension of the surface to be treated  7  (i.e. when the layer  16  is deposited on only part of the surface to be treated  7 ), the defined area  24  comprises (in particular, is formed by) that part of the surface to be treated  7  on which the layer  16  has not been deposited, in other words in this case the area  24  at least partially overlaps with the area  19  (see, for example,  FIG.  17   ). Alternatively, when the extension of the defined area  18  coincides with that of the surface to be treated  7  (i.e. when the layer  16  is deposited on basically the whole surface to be treated  7 ), the defined area  24  comprises (in particular, is formed by) at least part of said defined area  18 , more particularly it comprises at least that part of the defined area  18  that is not covered by the layer  21  of powder material  22  (see, for example,  FIG.  18   ). 
     According to some non-limiting embodiments that are not illustrated, the control unit  25  is configured to control (in particular, digitally) the depositing assembly  20  so as to reproduce a pattern defined on the layer  16 . In particular, when the layer  16  is such as to reproduce a pattern on the surface to be treated  7  the two patterns (the one defined by the layer  16  and the one defined by the other layer  21 ) may at least partially coincide. In these cases, the control unit  25  is advantageously but not necessarily configured to also control the printing assembly  15 . 
     In detail, advantageously but not necessarily, the distribution of the powder material  22  on the layer  16  may appear wider than the distribution of the adhesive material  17  on the surface to be treated  7  (in other words, the pattern defined by the layer  21  may appear wider than the pattern defined by the layer  16 ), as it may be advantageous to deposit an amount of powder material  22  slightly in excess of what is required (in order to reduce the risk that areas where there should be powder material  22  remain without the required amount). According to alternative embodiments, the distribution of the powder material  22  on the layer  16  may not appear as wide as the distribution of the adhesive material  17  on the surface to be treated  7  (in other words, the pattern defined by the layer  21  may not be as wide as the pattern defined by the layer  16 ). In this case, in the part of the pattern defined by the layer  16  on which the powder material  22  is not deposited, another powder material, in particular a different one from the first powder material  22 , may, for example, be deposited in the same application step or in subsequent application steps. 
     Advantageously but not necessarily, in accordance with the non-limiting embodiment illustrated in  FIG.  19   , the depositing assembly  20  comprises at least one depositing device  26  comprising a container  27 , which is configured to contain the powder material  22  and has an output mouth  28 , whose longitudinal extension is transverse (in particular, perpendicular) to the feeding direction A and a number of distribution elements  29 , which are arranged in succession along the output mouth  28  and can each be operated independently of the other ones so as to allow the powder material  22  to go through an area of the output mouth  28  where it is arranged. 
     Even more specifically, advantageously but not necessarily, the depositing device  26  comprises a number of actuators  30 , each of which is designed to move a corresponding distribution element  29  between a closed position, wherein the corresponding distribution element  29  blocks the passage of the powder material  22  through the output mouth  28  area where it is arranged, and an open position, wherein the corresponding distribution element  29  allows the passage of the powder material  22  through the output mouth  28  area in which it is arranged. 
     It should be noted that by using the depositing device  26 , even more precise depositing (also in terms of thickness) of the powder material can be achieved. 
     According to certain non-limiting embodiments, the depositing assembly  20  is as described in the patent application WO2009118611 (of the same applicant) and/or in the patent IT1314623. 
     In addition, according to some advantageous and non-limiting embodiments that are not illustrated, the powder material  22  comprises a first type of powder material that is deposited in a region of the layer  16  (or a first part of the pattern defined by the layer  16 ) and a second type of powder material, different from the first type, in another region, at least partially different from the previous one, of the layer  16  (or a first part of the pattern defined by the layer  16 ). These regions may at least partially overlap with each other. In particular, the first and second types of powder material  22  advantageously differ from each other in their mechanical and/or physical characteristics and/or their colour. 
     In these cases, advantageously but not necessarily, the depositing assembly  20  comprises two depositing devices  26  that are the same and arranged side-by-side in succession along the determined path P, one intended to deposit a first type of the powder material  22  and the other intended to deposit a second type of the powder material  22  (different from the first type of powder material). This makes it possible to obtain a combination of two (or more) types of powder material in a relatively simple way, and, thus, to create particular aesthetic effects such as combinations of different colours and/or shades. 
     Alternatively, the depositing assembly may comprise a single depositing device  26 , such as the one described above, whose container  27 , in temporally successive steps, is filled with powder material  22  of the two different types. 
     Advantageously, the machine  5  also comprises at least one additional printing assembly  31 , which is arranged at the third application station  14  and is configured to apply an additional layer  32 , which comprises (in particular, consists of) an adhesive and/or covering material, on the layer  21 . 
     Advantageously, but without imposing limits, this printing assembly  31  has a similar structure and operation to the printing assembly  15 . 
     The fact that the adhesive material  17 , the powder material  22 , and this additional layer  32  are simultaneously present on the surface to be treated  7  makes it possible to reduce the risk that the powder material  22  moves on the base ceramic article CB, for example in subsequent processing steps of the base ceramic article CB itself. In other words, the presence of the additional layer  32  ensures that any powder material  22  that had not remained adhered to the underlying layer  16  is blocked by the layer  32 , thereby minimising the risk of undesired movement of the powder material  22  that could soil components of the machine  5  or other parts of the plant  1 , compromising its proper operation in the worst case scenario. 
     According to some advantageous but non-limiting embodiments that are not illustrated, the layer  32  comprises (in particular, mainly consists of) a covering material that is applied over basically the whole extension of the layer  21  to cover it. Advantageously, this covering material may be any material, for example a fixative material in order to fix the powder material  22 , or a material such as to provide the surface to be treated  7  with particular aesthetic (e.g. particular gloss) and/or functional (e.g. particular roughness) properties. 
     According to alternative non-limiting embodiments, such as those shown in  FIGS.  14  to  18   , the layer  32  comprises (in particular, mainly consists of) an adhesive material  33 , which is applied to the layer  21  by the printing assembly  31 . This adhesive material  33  is, advantageously but not necessarily, of the same type as the other adhesive material  17 . 
     Similarly to what has been described above in relation to the layer  16 , in this case too, the printing assembly  31  may be configured to apply the layer  32  on basically the whole extension of the layer  21  so as to cover all the powder material  22 , in particular on the whole part  24  of the defined area  18  (see, for example,  FIGS.  14 ,  15 ,  16 , and  18   ). 
     Alternatively, the printing assembly  31  may be configured to apply the layer  32  in at least one defined area  34  so that at least one other defined area  35  (in particular different to the defined area  34 ) remains free of adhesive material  33  (see  FIGS.  17  and  18   ). 
     In this case, advantageously but not necessarily, the control unit  25  is configured to control (in particular, digitally) the printing assembly  31 , so as to selectively apply the layer  32  on the layer  21 , in particular on this defined area  34 . 
     In embodiments that involve a layer  32  mainly consisting of adhesive material  33 , this adhesive material  33  is intended to receive and fix an additional layer of powder material  36 . 
     Advantageously, this enables the overlapping of several layers of powder material, which ensures greater density of the layer of powder material arranged on each base ceramic article CB, but also the possibility of creating more complex decorations, and, more generally, surface treatments, for example, by overlapping powder materials of different functional and/or mechanical and/or aesthetic characteristics. 
     Specifically, in accordance with these preferred but non-limiting embodiments like the one illustrated in  FIGS.  7  to  13   , the determined path P extends through a fourth application station  37  arranged downstream of the third application station  14 , and the machine  5  comprises an additional depositing assembly  38  arranged at the application station  37  and configured to deposit a layer  39  comprising (in particular, consisting of) a powder material  36  on the layer  32  of adhesive material  33 . 
     Advantageously, but not necessarily, this additional depositing assembly  38  has a similar structure and operation to the depositing assembly  20  described above. 
     The powder material  36  may be the same as the powder material  22 , as illustrated in  FIGS.  14  to  16   , or different to the powder material  22 , as illustrated in  FIGS.  17  and  18   . 
     In particular, according to some advantageous but not exclusive embodiments, the powder materials  22  and  36  differ from each other according to the average particle size. In particular, in some cases in order to obtain a more homogeneous and less porous coverage of the surface to be treated  7 , it is advantageous to overlap particles of different particle sizes so that the particles of smaller size are positioned in the spaces remaining between two or more particles of larger size placed side by side. This advantageously maximises the final density of the powder layer (particularly ceramic powder layer) placed above the surface to be treated  7 . 
     Specifically, according to some advantageous but non-limiting embodiments such as those illustrated in  FIGS.  15  to  18   , the powder material  22  comprises (in particular, mainly consists of) ceramic particles with sizes from approximately 75 to approximately 150 μm, more specifically from approximately 100 to approximately 125 μm, while the powder material  36  comprises (in particular, mainly consists of) ceramic particles with sizes from approximately 150 to approximately 400 μm, more particularly from approximately 200 to approximately 350 μm (see  FIG.  15   ). Alternatively, as in the embodiments of  FIGS.  16  and  17   , the powder material  22  comprises (in particular, mainly consists of) ceramic particles with sizes from approximately 150 to approximately 400 μm, more particularly from approximately 200 to approximately 350 μm, while the powder material  36  comprises (in particular, mainly consists of) ceramic particles with sizes from approximately 75 to approximately 150 μm, more particularly from approximately 100 to approximately 125 μm. 
     Similar to the above description for the layer  21 , according to some advantageous but not exclusive embodiments, the depositing assembly  38  is configured to deposit the layer  39  selectively on the layer  32  in at least one part  40  of the defined area  34 . 
     In these cases, advantageously but not necessarily, the control unit  25  is configured to also control the depositing assembly  38  so that the powder material  36  is applied to a part  40  of the defined area  34 . Specifically, advantageously but not necessarily, this defined area  40  may comprise the whole extension of the defined area  34 , in other words the extension of the part  40  and the extension of the area  34  on which the layer  32  of adhesive material is deposited coincide (see, for example,  FIG.  17   ). According to other non-limiting variants, the control unit  25  is configured to also control the depositing assembly  38  so that this depositing assembly  38  deposits the powder material  36  only on a part of the layer  32  so that a part  41  remains free of the powder material  36  (see, for example,  FIG.  18   ). In this case, the extension of the part  40  is less than the extension of the area  34 . Specifically, this other part  41  may be intended to receive another type of powder material (as illustrated in  FIG.  18   ) or another substance, for example a covering material. 
     The powder material  36 , similarly to what has been said above for the first powder material  22 , may also comprise two different types of powder material that differ from each other in functional and/or mechanical and/or aesthetic characteristics, and which are intended to be applied to at least partially different regions of the layer  32 . 
     According to some advantageous but not exclusive embodiments, such as those illustrated in  FIGS.  7  to  13  and  16   , the determined path P extends along an additional fifth application station  42 , arranged downstream of the fourth application station  37 , and the machine  5  comprises an additional printing assembly  43  that is configured to apply a layer  44  comprising (in particular, consisting of) a material  45 , which comprises (in particular, is) a covering material, over basically the whole extension of the layer  39 , so as to cover it (see, in particular,  FIG.  16   ). 
     Advantageously, but not necessarily, this printing assembly  43  is similarly made and has the same operation as the printing assemblies  15  and  31 . 
     Advantageously, the presence of the covering material  45  allows the underlying layers  21 ,  30  to be fixed. 
     According to additional advantageous but non-limiting embodiments, such as those illustrated in  FIGS.  7  to  13   , the machine  5  comprises a removal station  46  arranged downstream of the second application station  13 , and configured to remove, preferably by suction, the excess powder material  22 , in particular the powder material  22  that has not adhered to the layer  16  (as illustrated, for example, in  FIGS.  5  and  10   ). 
     Advantageously, this removal station  46  is arranged along the path P defined upstream of the third application station  14 , more specifically, it is arranged between the second application station  13  and the third application station  14 . 
     In these cases, the machine  5  comprises a (known) removal device  47  comprising a suction unit for sucking up excess powder material  22  (i.e. not bound to the surface to be treated  7  by the adhesive material  17 ). More specifically, this removal device  47  comprises a suction mouth designed to suck the powder material  22  that has not adhered to the layer  16  upwards. 
     Alternatively, the removal device  46  may be configured to remove the excess powder material  22  by blowing. However, suction is preferable as it reduces (for example compared to blowing) the risk that the powder material  22  moves to unwanted areas. 
     According to additional advantageous embodiments that are not illustrated, the machine  5  comprises an additional removal station arranged downstream of the application station  37 , and configured to remove, preferably by suction, the excess powder material  36 , in particular the powder material  36  that has not adhered to the layer  32 . Specifically, this additional removal station that is not illustrated could be arranged along the path P determined between the fourth application station  37  and the fifth application station  42 . 
     It is understood that the machine  5  may comprise any number of depositing assemblies and printing assemblies, and possibly removal devices, made according to any one of the above-described embodiments, arranged in succession so as to achieve a multi-layered treatment, for example a decoration, on the surface to be treated  7 . 
     In accordance with an additional aspect of this invention, a method for the surface treatment of the base article CB that has at least the surface to be treated  7  is also provided. 
     Specifically, advantageously but not necessarily, the method comprises: a step of feeding a base ceramic article CB, during which the base ceramic article CB is fed along a path P determined in a feeding direction A through a first application station  12 , a second application station  13 , arranged downstream of the first application station  12 , and at least a third application station  14 , arranged downstream of the second application station  13 ; an application step, during which a printing assembly  15  arranged at the first application station  12  applies a layer  16  comprising (in particular, consisting of) a material  17 , which comprises (in particular, is) an adhesive material, on at least part of the surface to be treated  7 ; a second application step, during which a depositing assembly  20  arranged at the second application station  13  deposits a layer  21  comprising (in particular, consisting of) a powder material  22  onto the layer  16  so as to remain adhered to the layer  16 ; and at least one additional application step, during which a printing assembly  31  arranged at the third application station  14  applies a layer  32  comprising (in particular, consisting of) a material, which comprises (in particular, is) an adhesive and/or covering material, onto the layer  21 . 
     According to a preferred but not exclusive embodiment of the method, during the first application step, the printing assembly  15  applies the layer  16  in at least one defined area  18  of said surface to be treated  7 ; during the second application step, the depositing assembly  20  selectively deposits the layer  21  comprising (in particular, consisting of) the powder material  22  on the layer  16  in at least one part  23  of the defined area  18  so as to remain adhered to the layer  16  and so as not to cover at least a part of an additional defined area  24  of the surface to be treated  7 ; and during the third application step, the printing assembly  31  applies the third layer  32  on the layer  21  in another defined area  34 , which is at least a portion of the part  23  of the defined area  18 . 
     As mentioned above, with reference to the machine  5 , the defined area  18  may have an extension equal to that of the surface to be treated  7  (see, in particular,  FIGS.  14 ,  15 ,  16 , and  18   ) or may have an extension smaller than that of the surface to be treated  7 , so that an additional area  19  remains free of adhesive material  17 . 
     Similarly, the part  23  of the defined area  18  may have the same extension as the defined area  18  or may have a smaller extension, in particular so as not to cover at least part of the defined area  24  of the surface to be treated  7  (or of the layer  16 ). Similarly, the defined area  34  may have the same extension as the part  23  of the defined area  18 , or a smaller extension than the part  23  of the defined area  18 . 
     As mentioned above with reference to the machine  5 , according to some non-limiting embodiments, when adhesive material is applied during the second application step: during the feeding step, the base ceramic article CB is fed through a fourth application station  37  arranged downstream of the third application station  14 ; and the method comprises at least a fourth application step during which a depositing assembly  38  arranged at the fourth application station  37  deposits (preferably selectively) on at least part of the layer  32  a layer  39  comprising (in particular, consisting of) a powder material  36  so as to remain adhered to the layer  32 . 
     In particular, advantageously but not necessarily, the depositing assembly  38  selectively deposits the layer  39  comprising the (in particular, consisting of the) powder material  36  on the layer  32  in part  40  of said defined area  34 . 
     In this case, advantageously but not necessarily, during the feeding step, the base ceramic article CB is fed through a fifth application station  42 , which is arranged downstream of the fourth application station  37 ; and the method also comprises a fifth application step, during which a printing assembly  43 , which is arranged at the fifth application station, applies a layer  44  of a material  45  comprising (in particular, consisting of) a covering material over basically the whole extension of the layer  39  so as to cover it (see  FIG.  16   ). 
     Advantageously but not necessarily, the method is implemented by the above-described machine  5 . Therefore, all of the considerations set forth above regarding possible variants for operating the machine  5  also remain valid for the method for the surface treatment of the base ceramic article BC. 
     It is also understood that the steps of the method of this invention (carried out according to any one of the above-described embodiments) may be repeated a finite number of times, so as to achieve a multi-layered treatment, for example a decoration, on the surface to be treated  7 . 
     According to some advantageous but not exclusive embodiments, such as the one illustrated in  FIGS.  17  and  18   , the method involves, for example, an additional step of applying an adhesive material, just the same as either the first or third application step described above, during which an additional layer  48  of adhesive material  49  (advantageously, the same as the adhesive material  17  and  33 ) is applied to at least part of the layer  39 , and an additional application step during which an additional layer  50  comprising (in particular, consisting of) powder material  51  is applied to the layer  48 . 
     According to some advantageous but non-limiting variations such as the one illustrated in  FIG.  17   , the method also involves a final covering step, during which a printing assembly deposits a layer of covering material  52  over basically the whole extension of the surface to be treated  7  so as to cover all the layers below. 
     Advantageously, by superimposing several layers of powder material, possibly of different types (e.g., of a different kind and/or particle size), various types of decoration can be obtained. For example, it is possible to obtain different colour shades in order to reproduce the appearance of natural stones more realistically, but it is also possible to achieve three-dimensional effects that were not possible until now. 
     a. According to some non-limiting embodiments, the adhesive material  17 ,  33 , and  48  comprises (more precisely, consists of) mixtures containing glycols (such as DEG, PEG, Triethylene glycol bis CAS Number 94-28-0), esters (e.g., Ethylhexyl cocoate CAS Number 92044-87-6, Ethylhexyl palmitate CAS Number 29806-73-3, 2-ethylhexyl stearate CAS Number 22047-49-0, Caprylic/capric triglyceride, 2-ethylhexyl laurate CAS Number 20292-08-4), paraffins (e.g., Isoparaffin, n-paraffin), glycol ethers (such as Tripropylene glycol n-butyl ether (TPnB) CAS Number 55934-93-5, Tripropylene glycol monomethyl ether (TPM) CAS Number 25498-49-1), etc. or a combination thereof.
 
b. In addition or alternatively, according to some non-limiting embodiments, the adhesive material  17 ,  33 , and  48  is selected from the group consisting of: a material (in particular, a composition) that is basically stable and does not significantly change its characteristics in contact with air and at temperatures of at least 15° C. to 60° C., a material (in particular, a composition) that is thermoplastic and hardens at room temperature.
 
     According to some advantageous but not exclusive embodiments, the powder material  22 ,  36 , and  51  applied to the surface to be treated  7  comprises (consists of) a ceramic material. Even more particularly, the entirety of the powder material  22 ,  36 , and  51  applied to the surface to be treated advantageously comprises (consists of) particles with sizes from approximately 50 to approximately 500 μm, in particular from approximately 75 to approximately 350 μm. 
     According to alternative embodiments that are not illustrated, at least part (in particular a small part) of the powder material  22 ,  36 , and  51  may be substituted by another type of material, for example glass material, stone material, atomized material, granules, micronized material, synthesized material, agglomerates (for example flakes and threads) that are inert (for example composed of silicon carbide), metallic powders, powders from third processes suitable for ceramic use, etc., or a combination thereof. 
     a. Advantageously but not necessarily, the covering material  45  and  52  comprises (in particular, consists of) a fusible substance (i.e., a substance that melts at the firing temperatures of the base ceramic article CB). In particular, this fusible substance is at least partially liquid under the application conditions (i.e., under the temperature and pressure conditions under which the fusible substance is applied).
 
b. More particularly, this fusible substance is in the liquid state or in suspension under the application conditions (i.e., at the application temperature and pressure). In detail, advantageously but not necessarily, the covering material  45  and  52  is selected from the group consisting of: fixative material, hardening material, reinforcing material, polishing material, iridescent material, lead enamel, alkaline enamel, alkaline earth enamel, boric enamel, zinc enamel, etc., or a combination thereof.
 
c. The subject of this invention has several advantages compared to the prior art. These include the following.
 
     This invention, due to the more controlled and precise application of the powder material  22  and the presence of an additional layer  32  on top of the powder material layer  22 , also allows those particles of powder material  22  that may not have adhered to the underlying layer  16  of adhesive material  17  to be fixed, minimising the risk of unwanted movement of the powder material  22 . Surprisingly, this makes it possible to improve the positioning of the particles (and, therefore, the quality of the “pattern”—shape—of the part  23 ; the particles have less possibility of moving) and to avoid sucking the excess powder material  22 , effectively making the removal step non-essential (although still advantageous) with the consequent simplification of the machine  5  and of the method for the surface treatment of the base ceramic articles CB. In addition, this entails a significant saving of powder material  22 . In fact, the powder material  22  is applied in the correct amounts and basically all of it remains adhered to the base ceramic article CB. All this while, at the same time, guaranteeing improved results in terms of homogeneity of thickness and density of the treatment. 
     In addition, this improvement in density and thickness consistency of the layers  21 ,  39 , and  50  of powder material  22 ,  36 , and  52  enables the simplification of additional treatments to which the base ceramic article BC could be subjected after the application of the powder material  22 ,  36  and  52 . Specifically, both the processes of applying additional substances on the surface to be treated and the processes of lapping and/or polishing the base ceramic article CB can be simplified. In addition, the lapping and/or polishing processes can be performed using less polishing material and/or reducing the duration of the operations, having to act on a more uniform layer. 
     The following aspects of the invention are also provided (alternatively or additionally). 
     1.—A method for the surface treatment of a base ceramic article CB having at least one surface to be treated  7 ; the method comprises: 
     a feeding step for a base ceramic article CB, during which the base ceramic article CB is fed along a given path P in a feeding direction A through a first application station  12 , a second application station  13 , which is arranged downstream of the first application station  12 , and at least a third application station  14 , which is arranged downstream of the second application station  13 ; 
     a first application step, during which a first printing assembly ( 15 ) arranged at the first application station  12  applies a first layer  16  comprising (in particular, consisting of) a first material  17 , which comprises (in particular, is) an adhesive material on at least part of said surface to be treated  7 ; 
     a second application step, during which a first depositing assembly  20  arranged at the second application station  13  deposits a second layer  21  comprising (in particular, consisting of) a first powder material  22  on said first layer  16  so as to remain adhered to said first layer  16 ; 
     the first depositing assembly  20  comprising at least one container  27 , which is configured to contain said powder material  22  and has an output mouth  28 , whose longitudinal extension is transverse (in particular, perpendicular) to the feeding direction A; and a number of distribution elements  29 , which are arranged in succession along the output mouth  28  and can each be operated independently of the other ones so as to allow the powder material  22  to go through an area of the output mouth  28  wherein it is arranged; and 
     a third application step, during which a second printing assembly ( 31 ) arranged at the third application station ( 14 ) applies a third layer  32  comprising (in particular, consisting of) a second material  33 , which comprises (in particular, consists of) an adhesive and/or covering material, on said second layer  21 . 
     2.—A method according to aspect 1, wherein said first powder material  22  comprises a first type of powder material in a first region of said first layer  16  and a second type of powder material, which is different from the first type, in a second region of said first layer  16 , which is at least partially different from the first region. 
     3.—A method according to aspect 1 or 2, wherein, when the second material  33  comprises (in particular, is) an adhesive material: during said feeding step, said base ceramic article CB is fed through a fourth application station  37 , which is arranged downstream of the third application station  14 ; and the method comprises a fourth application step, during which a second depositing assembly  38 , which is arranged at said fourth application station  37  deposits, on said third layer  32  a fourth layer  39  comprising (in particular, consisting of) a second powder material  36  (in particular, different from the first powder material  22 ); 
     the second depositing assembly  38  comprising at least one additional container  27 , which is configured to contain the second powder material  36  and has an additional output mouth  28 , whose longitudinal extension is transverse (in particular, perpendicular) to the feeding direction A; and a number of additional distribution elements  29 , which are arranged in succession along said additional output mouth  28  and can each be operated independently of the other ones so as to allow the second powder material  36  to go through an area of the additional output mouth  28  where it is arranged. 
     4.—A method according to aspect 3, wherein either the first powder material  22  or the second powder material  36  comprises a ceramic material comprising (in particular, consisting of) particles with dimensions ranging from approximately 75 μm to approximately 150 μm, in particular from approximately 100 μm to approximately 125 m; and the other one of the first powder material  22  or the second powder material  36  comprises a ceramic material comprising (in particular, consisting of) particles with dimensions ranging from approximately 150 μm to approximately 400 μm, in particular from approximately 200 μm to approximately 350 μm. 
     5.—A method according to aspect 3 or 4, wherein: during said feeding step, said base ceramic article CB is fed through a fifth application station  42 , which is arranged downstream of the fourth application station  37 ; and the method also comprises a fifth application step, during which a third printing assembly  43 , which is arranged at said fifth application station  42 , applies a fifth layer  44  comprising (in particular, consisting of) a third material  45 , which comprises (in particular, consists of) a covering material, basically on the whole extension of said fourth layer  39  so as to cover it. 
     6.—A method according to any one of aspects 1 to 5, wherein the first powder material  22 , and, if necessary, the second powder material  36 , comprises a ceramic material comprising (in particular, consisting of) particles with dimensions ranging from approximately 50 μm to approximately 500 μm, in particular from approximately 75 μm to approximately 350 μm. 
     7.—A method according to any of the aspects from 1 to 6, wherein: 
     said first application step, said third application step, and possibly said fifth application step are performed using a corresponding printing assembly  15 ,  31 ,  43  applying said first material  17 , said second material  33 , and possibly said third material  45 ,  49 , respectively, by the emission of at least one jet of said first material  17 , said second material  33 , and possibly said third material  45 ,  49 ; 
     a. in particular, each printing assembly  15 ,  31 ,  43  comprises an inkjet head for emitting one or more jets of adhesive material and/or covering material; in particular, each printing assembly  15 ,  31 ,  43  applies said first layer  16 , said third layer  32  and, when required, said fifth layer  44 ,  48 , digitally so as to reproduce a defined pattern. 
     8.—A method according to any one of aspects 1 to 7, wherein said covering material comprises (in particular, consists of) a fusible substance at least partially liquid under the application conditions, in particular in a liquid state or in a suspension under the application conditions; even more particularly, said covering material is selected from the group consisting of: fixative material, hardening material, reinforcing material, polishing material, iridescent material, lead enamel, alkaline enamel, alkaline earth enamel, boric enamel, zinc enamel, or a combination thereof. 
     9.—A method according to any one of aspects 1 to 8, wherein at least during the first application step, said first printing assembly  15  applies said first layer  16  on at least part of said surface to be treated  7  so as to reproduce a defined pattern on the surface to be treated  7 ; during said second application step, said first depositing assembly ( 20 ) deposits said second layer  21  (in particular, selectively) on said first layer  16  so as to reproduce an additional defined pattern on said first layer  16 ; in particular, the pattern and the additional pattern coincide. 
     10.—A machine  5  for the surface treatment of a base ceramic article CB having at least one surface to be treated  7 ; the machine  5  comprises: 
     a conveying device  11  to feed the base ceramic article CB along a given path P in a feeding direction A through a first application station  12 , a second application station  13 , which is arranged downstream of the first application station  12 , and at least a third application station  14 , which is arranged downstream of the second application station  13 ; 
     a first printing assembly  15 , which is arranged at the first application station  12  and is configured to apply a first layer  16  comprising (in particular, consisting of) a first material  17 , which comprises (in particular, is) an adhesive material, on at least part of said surface to be treated  7 ; 
     a depositing assembly  20 , which is arranged at the second application station  13  and comprises at least one container  27 , which is configured to contain a first powder material  22  and has an output mouth  28 , whose longitudinal extension is transverse (in particular, perpendicular) to the feeding direction A and a number of distribution elements  29 , which are arranged in succession along said output mouth  28  and can each be operated independently of the other ones so as to allow said first powder material  22  to go through an area of the output mouth  28 , wherein it is arranged, so as to deposit a second layer  21  comprising (in particular, consisting of) said first powder layer  22  on said first layer ( 16 ) so as to remain adhered to said first layer  16 ; 
     a second printing assembly  31 , which is arranged at said third application station  14  and is configured to apply a third layer  32  comprising (in particular, consisting of) a second material  33 , which comprises (in particular, consists of) an adhesive material and/or a covering material, on said second layer  21 . 
     11.—A machine  5  according to aspect 10, wherein: 
     when said second material  33  is adhesive, said determined path P extends through at least a fourth application station  37  arranged downstream of said third application station  14 ; and said machine  5  comprises a second depositing assembly  38 , which is arranged at said fourth application station  37  and comprises an additional container  27 , which is configured to contain a second powder material  36  and has an additional output mouth  28 , whose longitudinal extension is transverse (in particular, perpendicular) to the feeding direction A and a plurality of additional distribution elements  29 , which are arranged in succession along said additional output mouth  28  and can each be operated independently of the other ones so as to allow the powder material  36  to go through an additional area of said additional output mouth  28 , wherein it is arranged, so as to deposit a fourth layer  39  comprising (in particular, consisting of) said second powder material  36  on said third layer  32  so that said powder material remains adhered to said third layer  32 . 
     12.—A machine according to aspect 11, wherein said given path (P) extends through a fifth application station  42 , which is arranged downstream of said fourth application station  37 , and the machine  5  comprises a third printing assembly  43 , which is arranged at said fifth application station  42  and is configured to apply a fifth layer  44  comprising (in particular, consisting of) a third material  45 , which comprises (in particular, is) a covering material, basically on the whole extension of said fourth layer  39  so as to cover it. 
     13.—A machine ( 5 ) according to any one of aspects 10 to 12, wherein the (possibly each) depositing assembly  20 ,  38  comprises a number of actuators  30 , each of which is designed to move a corresponding distribution element  29  between a closed position, wherein the corresponding distribution element  29  blocks the passage of the powder material  22 ,  36  through the output mouth  28  area in which it is arranged, and an open position, wherein the corresponding distribution element  29  allows the passage of the powder material  22 ,  36  through the output mouth  28  area in which it is arranged. 
     14.—A machine ( 5 ) according to any one of aspects 10 to 13, wherein each printing assembly  15 ,  31 ,  43  comprises at least one inkjet head, which is configured to emit one or more jets of adhesive material and/or covering material. 
     15.—A machine ( 5 ) according to any one of aspects 10 to 14, and comprising a control unit  25 , which is configured to control (in particular, digitally) at least said first printing assembly  15  and said first depositing assembly ( 20 ) so that said first printing assembly  15  itself applies said first layer  16  in order to reproduce a defined pattern on said surface to be treated  7 ; the control unit  25  is configured to control (in particular, digitally) said first depositing assembly  20  so that the first depositing assembly  20  itself deposits the second layer  21  (in particular, selectively) on said first layer  16  so as to reproduce another pattern defined on the surface on said first layer  16 ; in particular, the pattern and the additional pattern coincide.