Tiles, apparatuses and methods for producing tiles

The invention further concerns a cladding tile for surfaces, specifically for cladding on outer surfaces of architectonic structures, an apparatus and a method for obtaining the afore-mentioned cladding tile.

The invention concerns a tile made of ceramic material, specifically a striped tile, an apparatus and a method for obtaining afore-mentioned striped tile. Various cladding elements for building constructions are known, for example slabs of natural or artificial stone, as well as flat ceramic tiles of various sizes and geometric shapes. However, the types of various cladding elements available have technical functions substantially equivalent to one another, such as protecting an architectonic structure to which they are fixed from adverse weather conditions or wear and for adorning it.

Tiles are also known made of ceramic material and decorated in such a way as to show a substantially parallel striped decoration on one surface which remains visible after laying of the tile. The afore-mentioned stripes may be of different colours and are made by means of a screen printing process, by depositing layers of ceramic colour on the surface of the tile. One defect of tiles, thus obtained is that they do not. have a. satisfactorily pleasant appearance. In..fact,.. the .thickness of the layers of colour deposited on the tiles remains visible even after the tile is fired. The appearance of the tile is therefore not very natural, since it is easy to see that it is the result of a decoration process in which one or more colours have been applied on the surface of the tile.

One object of the invention is to improve the known cladding elements. Another object of the invention is to widen the range of technical functions of known cladding elements.

A further object is to improve the tiles made of ceramic material and having a substantially parallel striped decoration.

A still further object of the invention is to produce tiles with substantially parallel stripes with a satisfactorily pleasant appearance .

A still further object of the invention is to obtain tiles with substantially parallel stripes having a natural appearance where the layers of ceramic colour deposited cannot be identified.

In a first aspect of the invention, a tile is provided, comprising an exposed layer provided with a separation zone between a first portion and a second portion of said tile, said first portion and said second portion being made respectively of a first ceramic material and a second ceramic material, said tile being characterized in that said first ceramic material is a first semiconductor material having a p type structure and said second ceramic material is a semiconductor having an n type structure and said separation zone is a p-n joint arranged for generating an electric current when illuminated by solar radiation.

In a second aspect of the invention, a method is provided for forming tiles comprising supplying doped semiconductor . ceramic materials, through an inlet . opening... of....dispensing -means- and dispensing -said doped, semiconductor ceramic materials through a release opening of said dispensing means opposite said inlet opening, characterized in that said supplying comprises further dispensing said doped semiconductor ceramic materials through a plurality of dispensing nozzles, said dispensing nozzles leading into an enclosure body in which said inlet opening is provided. Owing to these aspects, a tile is made available the technical functions of which have been significantly improved and broadened. Electrogenic properties are thus conferred on the tile. The first ceramic material and the second ceramic material are

derived from the sinterization of a first ceramic powder and a second ceramic powder suitably treated so as to obtain type p and type n semiconductor materials, respectively, for example, doped with doping elements to develop electrogenic properties.

In this manner, once the tile is formed, the first portion and the second portion when brought alongside act like a photovoltaic cell, forming a so-called p-n joint in the separation zone which allows the formation of a direct electric current when the tile is illuminated by solar radiation.

By connecting a number of photovoltaic cells in series or in parallel, it is possible to obtain a required voltage and electric power. The tiles can be used for cladding the outer surfaces of architectonic structures, such as buildings or bridges. Thus, by offering structural and protective features similar to those of known cladding elements, the tiles according to the invention can generate an advantageously usable electric current .

In a third aspect of the invention, a tile is provided, comprising an exposed surface having a striped decoration, said tile being characterized in that said decoration extends .from said exposed surface for a . considerable - thickness of said .tile:.

In a fourth aspect of the invention, a method is provided for forming tiles comprising supplying coloured ceramic materials through an inlet opening of dispensing means and dispensing said coloured ceramic materials through a release opening of said dispensing means opposite said inlet opening, characterized in that said supplying comprises further dispensing through a plurality of dispensing nozzles, said dispensing nozzles leading into an enclosure body in which said inlet opening is provided.

Owing to these aspects, an apparatus and a method are described for producing striped tiles having a pleasant and natural appearance .

The expression "significant thickness" means a thickness which occupies a considerable part, or the entire part of the thickness of a tile formed, for example, more than a few millimetres for a tile having a total thickness of about ten millimetres . Owing to the third and fourth aspect of the invention, it is therefore possible to obtain tiles with a pleasant and natural appearance. The decoration is no longer obtained by depositing ceramic colour but is made by producing the tile using ceramic powders in different colours suitably brought side by side during the tile forming step. In a fifth aspect of the invention, an apparatus is provided for forming tiles comprising dispensing means arranged for receiving ceramic materials through an inlet opening and dispensing said ceramic materials through a release opening opposite said inlet opening, characterized in that said dispensing means further comprise a plurality of dispensing nozzles, said dispensing nozzles leading into an enclosure body in which said inlet opening is provided.

Owing to this aspect, an apparatus is made available by means .of which.-. it_., is possible to easily produce .. a. _tiIe having-"electrogenic .properties, as.-.well as a t-iIe .decorated with substantially parallel stripes, depending on the type of ceramic material used.

In one embodiment, the apparatus is supplied with doped semiconductor ceramic materials. The dispensing nozzles are brought side by side inside the enclosure body and are positioned at a suitable distance from a depositing surface to deposit well defined stripes of doped semiconductor ceramic material on the latter. Each dispensing nozzle is arranged for feeding the enclosure body with type p or type n doped semiconductor ceramic material in such a way that by depositing these ceramic

materials inside the enclosure body, alternate, well defined layers of type n doped ceramic material and type p doped ceramic material are formed.

These layers are subsequently released on the depositing surface so as to form stripes of type n doped ceramic material and type p doped ceramic material on the depositing surface .

At the end of a forming step and a firing step, the stripes determine the side by side first portions and second portions of the tiles.

Each first portion interacts with a second portion placed side by side so as to make a photovoltaic cell.

In fact, a separation zone, acting as a p-n joint, is made between each first portion and the second portion placed side by side.

Each dispensing nozzle can make a strip of type p or type n doped semiconductor ceramic material.

It is thus possible to obtain a number of separation zones i.e., a number of p-n joints can be obtained. When illuminated by solar radiation, each of these joints produces a direct electric current which can be used advantageously.

In another embodiment, the apparatus is supplied with coloured ceramic materials The- dispensing nozzles are placed side by side inside the enclosure body and are positioned at a suitable distance from so as to obtain a required decoration.

Each dispensing nozzle is arranged for supplying the enclosure body with coloured ceramic materials of predefined colours in such a way that different coloured layers are formed by depositing these ceramic materials inside the enclosure body.

These layers are subsequently released on the deposit surface in such a way as to form the stripes in a ceramic semi-finished product from which the striped tile is obtained by means of a forming step and a firing step.

In this manner, each dispensing nozzle can make a stripe of a predefined colour.

By supplying dispensing nozzles arranged side by side with a ceramic powder of the same predefined colour, it is possible to obtain wider stripes of this predefined colour.

In a sixth aspect of the invention, an apparatus is provided for forming tiles, comprising dispensing means arranged for receiving ceramic materials through an inlet opening and dispensing said ceramic materials through a release opening opposite said inlet opening, characterized in that said dispensing means further comprises at least one dispensing member, said dispensing member being provided with a plurality of cavities leading into an enclosure body in which said inlet opening is provided. In one embodiment, the dispensing member comprises a block made of non-stick and anti- friction material, such as polytetrafluoroethylene (PTFE) . The cavities are made in the thickness of the block. Owing to the use of the dispensing member having non-sick, anti- friction properties, possible problems of clogging of the dispensing nozzles caused by the ceramic material powders used are avoided.

In a seventh aspect of the invention, a method is provided for forming tiles comprising supplying coloured ceramic materials through an inlet opening of. dispensing .means and dispensing said coloured ceramic materials through a release opening of said dispensing means opposite said inlet opening, characterized in that said supplying comprises further dispensing through dispensing member means, said dispensing member means being provided with a plurality of cavities leading into an enclosure body in which said inlet opening is provided.

In one embodiment, there is provision for keeping the dispensing member means fixed, thus making it possible to produce tiles decorated with parallel stripes. In another embodiment, the dispensing member is moved in different prefixed directions, making it possible to produce

tiles decorated with non parallel stripes, i.e. wavy or broken.

The invention will be better understood and carried into effect with reference to the attached drawings, in which some embodiments are shown by way of non- limiting example, in which:

Figure 1 is a plan view of a tile according to one embodiment of the invention;

Figure 2 is an interrupted section taken along a plane II-II of Figure 1;

Figure 3 is a plan view of a tile according to a further embodiment of the invention;

Figure 4 is an interrupted section taken along a plane IV-IV of Figure 3 ; Figure 5 is a plan view of a tile according to a still further embodiment of the invention;

Figure 6 is an interrupted section taken along a plane VI-VI of Figure 5;

Figure 7 is an interrupted section like that of Figure 6 showing electrodes according to an alternative embodiment of the invention;

Figure 8 is a plan view of a tile according to a still further embodiment of the invention;

Figure .9 is an interrupted ..section taken .along . a plane IX-IX of. Figure.5;

Figure 10 is an interrupted section like that of Figure 9 showing electrodes according to a further alternative embodiment of the invention;

Figure 11 is a schematic side view of an apparatus for the forming of tiles according to the invention;

Figure 12 is a perspective view of dispensing means and positioning means of the apparatus of Figure 11;

Figure 13 is a schematic front view of the dispensing means of Figure 12 in a first operating configuration; Figure 14 is a schematic front view of the dispensing means of Figure 12 in a second operating configuration;

Figure 15 is a perspective view of a tile according to a further embodiment of the invention;

Figure 16 is a perspective view of a striped tile according to the invention; Figure 17 is a front section of the tile of Figure 16;

Figure 18 is a schematized side section of an apparatus according to one embodiment of the invention;

Figure 19 is a partially sectioned perspective view of the dispensing means of the apparatus of Figure 18; Figure 20 is a portion of a front section of the dispensing means of Figure 19. in a first operating configuration;

Figure 21 is a portion of a front section of the dispensing means of Figure 19. in a second operating configuration;

Figure 22 is a schematic interrupted and incomplete front view, showing an embodiment of the apparatus provided with a dispensing member;

Figure 23 is a schematic, interrupted and incomplete plan view of the dispensing member shown in Figure 22;

Figure 24 is a schematic section conducted along plane XXIV- XXIV of Figure 23;

Figure 25 is a schematic, interrupted and incomplete, plan view of an embodiment of the dispensing member,-

Figure 26 is a schematic, interrupted and incomplete, plan view of. another embodiment of the ,.dispensing member; Figure 27. is a schematic, interrupted and incomplete, plan view of a still further embodiment of the dispensing member;

Figure 28 is a schematic plan view showing a version of decorated tile which can be obtained with the apparatus of

Figure 18; Figure 29 is a schematic plan view showing a further version of decorated tile which can be obtained with the apparatus of Figure 18;

Figures 1 and 2 show a tile 1, according to an embodiment of the invention, comprising a base layer 2 consisting of a supporting ceramic material, not visible after tile 1 has

been installed, for example, for cladding the outer surfaces of architectonic structures.

Tile 1 is further provided with an exposed layer 3 comprising first portions 4 made of a first semiconductor ceramic material 5 and second portions 6 made of a second semiconductor ceramic material 7. Between the first portions 4 and the second portions 6 separation zones are defined between the first semiconductor ceramic material 5 and the second semiconductor ceramic material 7. The first semiconductor ceramic material 5 and the second semiconductor ceramic material 7 have been suitably doped using doping elements in such a way as to show an n type structure and a p type structure, respectively. The n type structure is a structure having a weakly bonded negative charge for example, obtained by doping semiconductors with elements of the fifth group of the Periodic Table of elements.

The p type structure, on the other hand, has an excess of positive charge and can be obtained, for example, by doping a semiconductor with elements of the third group.

The separation zones form the so-called p-n junctions which, if illuminated by solar radiation, produce a difference in electric power between the first semiconductor ceramic material 5 and the. second semiconductor...ceramic material 7. In :this manner., each pair-comprising one: first-portion.4.and. one second portion 6 alongside the first portion 4 defines a photovoltaic cell.

By suitably connecting a number of photovoltaic cells, in series or in parallel, to an electric circuit, it is possible to obtain direct electric current having the required voltage or intensity.

The greater the extension of the p-n joints, illuminated by solar radiation, present in tile 1, the greater the electricity produced.

For using or storing the electrical energy produced, each photovoltaic cell must therefore be connected to an electrical circuit.

For this purpose, wires 8 made of conductor material are placed between the base layer 2 and the exposed layer 3.

Each wire 8 is in contact with the first portion 4 or the second portion 6 and follows the direction of the corresponding portion keeping at a suitable distance from the p-n joint. In fact, the first portion 4 and the second portion 6 can extend substantially rectilinearly, as shown in Figure 1, but can also be made curvilinear, for example, for aesthetic reasons . The wires 8 which are in contact with the first semiconductor ceramic material 5 define a negative electrode

9 of the photovoltaic cell.

The wires 8 which are in contact with the second semiconductor ceramic material 7 define a positive electrode

10 of the photovoltaic cell. Wires 8 can be placed between the base layer 2 and the exposed layer 3 during the forming of tile 1 as will be explained subsequently.

Owing to the positive electrodes 10 and the negative electrodes .9 the...photovoltaic cells present, in. the tile. can. be" connected- tθ; the ^electrical -circuit..

For example, a user device or electrical energy accumulator or an alternator can be connected to the circuit for converting the direct current produced into alternate electric current. A further embodiment of the invention provides a tile 101, shown in Figures 3 and 4, and substantially similar to tile 1 except for the fact that an insulating layer 11 is provided between each photovoltaic cell and each further photovoltaic cell alongside.

A still further embodiment of the invention, shown in

Figures 5, 6 and 7, provides a tile 201 substantially similar to tile 1 but not provided with base layer 2.

An even still further embodiment of the invention, shown in Figures 8, 9 and 10, provides a tile 301 substantially similar to further tile 101 but not provided with base layer

2.

In tile 201 and in tile 301, the first portion 4 and the second portion 6 extend throughout the transverse thickness of the tile.

The electrodes can be connected to the first portions 4 and the second portions 6 in the forming step, as shown in

Figures 6 and 9, according to the same method used for the production of tile 1 and tile 101. Alternatively, the electrodes can be applied, after the forming step, to an unexposed surface 12 of exposed layer 3, as shown in Figures 7 and 10.

For example, they can be applied cold, after a tile firing step, by gluing sheets made of conductor material to the unexposed surface 12, or they may be made of printable material and be applied by means of a screen printing process on the unexposed surface 12.

Figure 11 shows an apparatus 13 for forming tiles 1 according_,to the invention. The apparatus -13 comprises- a hopper 14, a_ conveyor belt ^~ 15 , positioning means 18, dispensing means 16, pressor means 17, a cutting device 19, conveyor means 20 and a press 21.

The hopper 14 is arranged for supplying conveyor belt 15 with a first layer 22 of ceramic powder 23, having substantially constant thickness, which, after a forming step and a firing step forms the afore-mentioned base layer

2.

The hopper 14 comprises a container 24 which is filled with the ceramic powder 23 and which is provided with a outlet spout 25 situated near an upper branch 26 of conveyor belt

15 which identifies a substantially horizontal movement plane R shown in Figure 12.

The container 24 is arranged substantially vertically and ceramic powder 23 is deposited by gravity on conveyor belt 15.

The conveyor belt 15 comprises two end rollers 27 on which a belt 28 is wound in the form of a loop and is arranged for moving the first layer 22 along an advance direction F, shown in Figure 12. The conveyor belt 15 is further provided with motor means

(not shown) arranged for driving one of the two end rollers

27, and consequently the belt 28, and the side partitions

29, seen in Figure 12, arranged on the sides of conveyor belt 28 to prevent the ceramic material deposited on it, for example ceramic powder 23, from flowing out of the sides and dropping from belt 28 when it is moving.

As shown in Figure 12, the positioning means comprises a roller 56 arranged for positioning a net 57 on first layer 22. The net 57 can be wound on roller 56 or net 57 can be fed to roller 56 by a feed device (not shown) and be arranged only for positioning the latter.

After being positioned on the first layer 22 the net 57 appears .in the form of a „.plurality of wires 8, arranged .for forming:., the -negative " -electrodes- ,9- »and. _~ the positive electrodes 10, which are oriented along the advance direction F and by a further plurality of further wires 58, arranged transverse to the advance direction F. The further wires 58 are arranged for connecting wires 8 in such a way as to simplify a movement and are made of a material deteriorating at high temperatures, which deteriorates during the firing step, thereby insulating wires 8. This material may be, for example, a non conductor organic material.

Thus, in tiles 1 produced using apparatus 13, the electrodes are separated from one another and correct working of the photovoltaic cell is possible.

The dispensing means 16 is arranged for depositing on first layer 22 and on net 57, moved by conveyor belt 15, a second layer 30 formed of a first ceramic powder 31 and a second ceramic powder 32 having such a composition as to obtain the first semiconductor ceramic material 5 and the second semiconductor ceramic material 6, respectively, after the forming step and the firing step.

After the forming step and the firing step, the second layer 30 forms the afore-mentioned exposed layer 3.

More specifically, the first ceramic powder 31 is arranged to form the first portions 4 and is therefore composed in such a way as to obtain the type n structure of first portion 4 at the end of the forming step and the firing step. Similarly, the second ceramic powder 32 is so arranged as to form the second portions 6 and is therefore so composed as to obtain the type p structure of second portion 6.

The dispensing means 16 comprises a parallelepiped-shaped box frame 33, shown in Figure 12.

The box frame 33 comprises a first wall 34 and a second wall 35-,having similar dimensions and . having...a ..width, equal to. a further :.width of,:conveyor. belt.:.15

The box frame 33 further comprises two side walls 36 arranged for spacing the first wall 34 from second wall 35. The box frame 33 thus defines a cavity 37 having an inlet opening 38 made on an upper surface 39 of box frame 33 and a release opening 40 made on a lower surface 41 of box frame 33.

The box frame 33 is arranged substantially perpendicular to movement plane R and in such a way that release opening 40 is positioned near first layer 22. The cavity 37 is arranged to contain and subsequently deposit by gravity the first ceramic powder 31 and the

second ceramic powder 32 on first layer 22 and on net 57 moved by belt 28.

The cavity 37 is supplied with the first ceramic powder 31 and the second ceramic powder 32 by a plurality of tube- shaped dispensing nozzles 42 partly introduced into box frame 33 by means of inlet opening 38.

Each nozzle 42 is arranged substantially perpendicular to the movement plane R and the nozzles 42 are placed side by side along a preferential direction, transverse in relation to the advance direction F, in such a manner as to form a row of nozzles 42.

A first end 43 of each nozzle 42 opens into cavity 37.

A second end 44 of each nozzle is arranged for being connected to a supply tube 45 arranged for feeding the corresponding nozzle 42 with first ceramic powder 31 or second ceramic powder 32.

For convenience of representation, in Figure 12, only one nozzle 42a is shown entirely and connected to corresponding supply tube 45. Nozzles 42 are held up by supporting and adjusting means not shown in the Figures, arranged to support each nozzle 42 and to allow adjustment along a direction substantially perpendicular to movement plane R in such a manner as to vary a distance present between the first end 43. of each. -nozzle 42. and belt 28.

Figures 13 and 14 show how nozzles 42 supply cavity 37 to make layers 46 of first ceramic powder 31 and second ceramic powder 32 inside the latter.

In Figure 13 nozzles 42 are all adjusted similarly, in such a way that the distance between the first end 43 of each nozzle 42 and the belt 28 is substantially the same.

The ceramic powder is released by each nozzle 42 into cavity

37 by gravity.

During the working, the ceramic powder introduced by means of nozzles 42 into cavity 37, forms a head inside the latter.

Cavity 37 is supplied in such a manner that, when apparatus 13 is working at full speed, the head is arranged near the first end 43 of each nozzle 42, as shown in Figure 13. The ceramic powder coming out of the first end 43 of each nozzle 42 therefore, by dropping into cavity 37 and with the head being near the first end 43, does not acquire such a speed as to be able to mix with the ceramic powder released by other nozzles 42 and is deposited near first end 43. This makes it possible to obtain well defined layers 46 of ceramic powder.

In Figure 13, for example, first ceramic powder 31 coming out of a first nozzle 42e does not mix with second ceramic powder 32 coming out of a second nozzle 42f alongside the first nozzle 42e and layers 46 are well defined. These layers 46 are then released on the first layer 22 in such a way as to obtain alternate and well defined stripes 47 (Figure 12) of the first ceramic material 31 and second ceramic material 32. The stripes thus obtained define the first portions 4 and the second portions 6 which are obtained from the first ceramic material 31 and second ceramic material 32, respectively, at the end of the firing step.

Two stripes side by side and formed of first ceramic material .31.and second- ceramic material 3.2, respectively, are .therefore arranged-to forπua -.photovoltaic cell....

To make a plurality of layers 46 having transverse dimension N, all the nozzles 42 must be supplied with the same predefined quantity of ceramic powder. The transverse dimension N is substantially equal to a diameter of first end 43.

By "transverse dimension N" is meant a dimension of layer 46 measured in a direction belonging to a plane defined by first wall 34 and parallel to movement plane R. Layer 46 having transverse dimension N, when deposited on first layer 13, forms a stripe 47 having width substantially equal to transverse dimension N.

To obtain stripes 47 having width greater than transverse dimension N it is possible to supply two or more adjacent nozzles with the same ceramic powder.

To produce the tiles 101 having insulating layer 11, it is 5 necessary to supply the nozzles with a third ceramic powder 48 in addition to first ceramic powder 31 and second ceramic powder 32.

The composition of third ceramic powder 48 is such as to lead to the formation of insulating layers 11 at the end of

10 the firing step.

The dimensions of the insulating layers 11, which alternate with photovoltaic cells, may be different from first portions 4 and second portions 6. To obtain these different dimensions, it is necessary for

15 layers 46 of the third ceramic powder 48 deposited in cavity 37 to have a further transverse dimension different from transverse dimension N.

For example, to obtain a further transverse dimension substantially multiple of transverse dimension N, a number

20 of nozzles placed side by side can be supplied with the third ceramic powder 48.

Moreover, nozzles 42 can be adjusted to obtain layers 46 having a still further transverse dimension M less than transverse dimension. N.

25. To _r do .so, .one -nozzle 42b,. selected for.-making a_lay.er....46b having a still further transverse dimension M, must be adjusted in such a way that it is closer to belt 28 in relation to a first nozzle 46c and a second nozzle 46d alongside near the sides of nozzle 42b, as shown in Figure

30 14.

Nozzle 42b is buried in the ceramic powder released by the first and second nozzles 42c and 42d side by side. Moreover, nozzle 42b is supplied with a quantity of third ceramic powder 48 less than the predefined quantity, while

35 the quantity of first ceramic powder 31 or second ceramic

powder 32 supplied to first nozzle near it 30c and second nozzle near it 3Od is greater than the predefined quantity. In this manner, a first layer 46c and a second layer 46d, made by means of first nozzle near it 42c and second nozzle near it 42d, respectively, crush layer 46b determining its still further transverse dimension M.

The first layer 46c and the second layer 46d however develop a first transverse dimension and a second transverse dimension greater than transverse dimension N, respectively. In this manner, by choosing a suitable quantity of powder to be supplied to each nozzle 42 and adjusting the nozzles 42 suitably, it is possible to make a considerable range of decorations with substantially parallel stripes in such a manner as to obtain a pleasant appearance of tile 101, in addition to the benefits produced by the photovoltaic cells. Layers 46 of tile 1 can also be suitably sized to obtain the required decorations.

For example, it is possible to obtain stripes of required width greater than transverse dimension N and different from one of its multiples by suitably flanking and adjusting nozzles 42 supplied with the same ceramic powder. In addition to this, first ceramic powder 31, second ceramic powder 32 and third ceramic powder 48 may have different colours, suitably selected for making the required decorations.

Subsequently, first layer 22, second layer 30 and net 57 placed between them, are moved by conveyor belt 15 towards pressor means 17. The pressor means 17 is arranged for carrying out a first forming step during which first layer 22 and second layer 30 are compacted together.

Pressor means 17 is arranged above belt 28 and comprises two further end rollers 49 on which a pressor belt 50 is wound in a closed loop arranged for compressing first layer 22 and second layer 30.

In this first forming step, first layer 22 and second layer 30 are compressed in such a way as to form a continuous sheet 51 of ceramic material including net 57. The continuous sheet 51 is moved by conveyor belt 15 to the cutting device 19.

Cutting device 19 is positioned above belt 28 and can move towards the latter to cut the continuous sheet 51 in order to obtain rectangular shaped semi-finished ceramic products 52 having predefined dimensions. Cutting device 19 comprises a first rotary circular blade 53 arranged for cutting a continuous sheet 51 along a direction transverse to the advance direction F and a plurality of rotary circular blades 53 arranged for cutting the continuous sheet 54 substantially parallel to the advance direction F.

The semi- finished ceramic products 52 thus obtained reach one of the two end rollers 27 and are offloaded by the conveyor belt 15 on to conveyor means 20. The conveyor means 20 is arranged for transferring the semi- finished ceramic products 52 to a press 21.

The conveyor means comprises a plurality of rollers 55 driven by further motor means not shown in Figure 3. The semi-finished ceramic products 52 are moved by rollers 55. near .press 21 on to „ which., they are unloaded _by the .conveyor means.20.

Press 21 is a known kind of press arranged for carrying out a second forming step during which the semi- finished ceramic products 52 are further compacted for forming unfired tiles (not shown) . The unfired tiles are subsequently fired during the firing step in known type of kilns, (not shown), to obtain tiles 1 or the further tiles 101 having electrogenic properties. During the first pressing step and the second pressing step, stripes 47 are not deteriorated and remain well defined.

In this manner, it is possible to obtain tiles in which the first portions 4 and the second portions 6 are well defined and form the p-n joints, at the end of the firing step. An apparatus according to a first alternative embodiment of the invention can be used for the production of still further tiles 201 and other tiles 301.

The apparatus according to the first alternative embodiment is substantially similar to apparatus 13 except for the fact that it has no hopper 14 for depositing the first layer 22. In the apparatus according to the first alternative embodiment, the net is deposited directly on belt 28 and the second layer 30 is deposited on the latter.

Tiles 201 and tiles 301 can be formed by means of an apparatus according to a second alternative embodiment of the invention substantially similar to the apparatus according to the first alternative embodiment but also devoid of positioning means 18.

In this case, for example, a successive gluing station (not shown) must be provided, for gluing the electrodes, obtained in the form of sheets, made of conductor material, on the unexposed surface 12 of the tile, or a screen printing device, for printing the electrodes by means of a printable conductor material on the unexposed surface 12 of the tile. It is thus possible- to obtain the versions of .tile .20L.. and tile 301 shown in Figures -7 -and 10, respectively.

By moving nozzles 42 of apparatus 13, of the apparatus according to the first alternative embodiment and the apparatus according to the second alternative embodiment during the forming step, it is also possible to obtain stripes not parallel to one another and not parallel to the sides of the tiles produced.

Another embodiment of the invention provides a tile 401, shown in Figure 15, in which an exposed layer 3a is made of a single semiconductor translucent ceramic material 61 having a type n or type p structure and a base layer 2a is

made of a semiconductor ceramic material 62 having a type p or type n structure, respectively.

In this way, the p-n joint formed between the exposed layer 3 and the base layer 2 is entirely illuminated by solar radiation, since the semiconductor translucent ceramic material 61 allows light to pass through it, and has an extension substantially equal to the dimensions of tile 401. Figures 16 and 17 show a tile 501 according to an embodiment of the invention. Tile 501 comprises a base layer 502 consisting of a supporting ceramic material, not visible after tile 501 is fixed to a wall or a floor.

Tile 501 further comprises a decoration layer 503 comprising portions made of a first coloured ceramic material 504 and further portions made of a second coloured ceramic material 505.

The portions and the further portions are so arranged as to produce a decoration 537 with substantially rectilinear stripes . A width of each stripe 537 can be defined in relation to a special effect that is to be obtained with the decoration.

For example, it is possible to make tiles having a large number of narrow stripes 537, or tiles with few broad stripes 537. It- .is also . possible _^ to...make ..tiles ..501..having , stripes..53-7 made- of.. more .--than _™ two coloured ceramic- materials .and- .thus obtain decorations with more than two colours. A thickness S of decoration layer 503, visible in Figure 17, can be selected according to the requirements . For example, if the first coloured ceramic material 504 and the second coloured ceramic material 505 are more expensive than the ceramic material used for making the base layer 502, it is possible to have a limited thickness S. Or otherwise, to simplify the procedure for the production of these tiles 501, which is explained below, it is possible to eliminate the base layer 502 and obtain a tile 501, (not

shown) having two opposite surfaces having striped decoration.

Tile 501 has excellent aesthetic qualities because it is not decorated with surfacing ceramic colours, so it has a high quality surface finish.

Figure 18 shows an apparatus 506 for forming tiles 501 according to the invention.

Apparatus 506 comprises a hopper 507, a conveyor belt 508, dispensing means 518, pressor means 509, a cutting device 510, conveyor means 511 and a press 512.

Hopper 507 is arranged for supplying the conveyor belt 508 with a first layer 513 of ceramic powder 514 having substantially constant thickness, which forms the aforementioned base layer 502 after a forming step and a firing step.

Hopper 507 comprises a container 515 which is filled with ceramic powder 514 and which is provided with a outlet spout 516 situated near an upper branch 517 which identifies a movement plane R of conveyor belt 508, shown in Figure 4. Container 515 is arranged substantially vertically and ceramic powder 514 is deposited by gravity on conveyor belt 508.

Conveyor belt 508 comprises two end rollers 519 on which a belt 520..is...wound., in -the form of a loop . and . is .arranged...for moving...the. -first, .-. ^" layer...513. on ..a. movement.: plane . an advance direction F, shown in Figure 19.

The conveyor belt is further provided with motor means (not shown) arranged for driving one of the two end rollers 519, and consequently the belt 520, and the side partitions 521, seen in Figure 19, arranged on the sides of conveyor belt 520 to prevent the ceramic material deposited on it, for example, ceramic powder 514, from flowing out of the sides and dropping from belt 520 when it is moving. The dispensing means 518 is arranged for depositing on first layer 513 moved by conveyor belt 508 a second layer 522 formed of a first ceramic powder 523 (Figures 20 and 21) of

a first colour and a second ceramic powder 524 (Figures 20 and 21) of a second colour.

After the forming step and the firing step, the second layer

522 forms the afore-mentioned decoration layer 502. The dispensing means 18 comprises a parallelepiped-shaped box frame 525, shown in Figure 19.

The box frame 525 comprises a first wall 538 and a second wall 539 having similar dimensions and having a width equal to a further width of conveyor belt 508. The box frame 525 further comprises two side walls 534 arranged for spacing the first wall 532 from second wall

533.

The box frame thus defines a cavity 531 provided with an inlet opening 527 made on an upper surface 526 of box frame 525 and a release opening 529 made on a lower surface 528 of box frame 33.

The box frame is arranged substantially vertically in relation to conveyor belt 520 and in such a way that the release opening 529 is positioned near first layer 513. Cavity 531 is arranged for containing and successively depositing by gravity the first ceramic powder 523 and the second ceramic powder 524 on first layer 13 moved by conveyor belt 520.

Cavity 531 is .supplied .with the. first . ceramic powder..523.and, the..second ceramic powder ..524..by."a .plurality .of-.,tube-shaped- dispensing nozzles 530 partly introduced into box frame 525 by means of inlet opening 527.

Each nozzle 530 is arranged substantially perpendicular in relation to conveyor belt 520 and nozzles 530 are positioned side by side along a preferential direction, transverse in relation to the advance direction F, in such a manner as to form a row of nozzles 530.

A first end 532 of each nozzle 530 opens into cavity 531.

A second end 533 of each nozzle is arranged for being connected to a feed tube 535 arranged for feeding the

corresponding nozzle 530 with first ceramic powder 523 or second ceramic powder 524.

For convenience of representation, in Figure 19, only one nozzle 530a is shown entirely and connected to corresponding feed tube 535.

Nozzles 530 are held up by supporting and adjusting means (not shown in the Figures) , arranged to support each nozzle

530 and to allow adjustment along a direction substantially perpendicular to movement plane R so as to vary a distance present between first end 532 of each nozzle 530 and conveyor belt 520.

Figures 20 and 21 show how nozzles 530 supply cavity 531 to make layers 536 of first colour 536 and second colour 32 inside the latter. In Figure 20 nozzles 530 are all adjusted similarly, so that the distance between the first end 532 of each nozzle 42 and conveyor belt 520 is substantially the same.

The ceramic powder is released by each nozzle 530 into cavity 31 by gravity. By supplying cavity 531 with a quantity of ceramic powder greater than a further quantity of ceramic powder which can be deposited by means of release opening 529 on conveyor belt 520, in a first step of working of apparatus 506, a head of ceramic powder is formed inside cavity 531. Cavity 531 is, supplied .in. such a way as-_to_maintain -the. head near the first end 532 of each nozzle 530 while apparatus

506 is working at full speed.

The ceramic powder coming out of the first end 532 of each nozzle 530 is therefore deposited near the latter. This makes it possible to obtain well-defined layers 536 of ceramic powder, since the ceramic powder falling into cavity

531 with the head near the first end 532 does not acquire such a speed as to be able to mix with the ceramic powder released by other nozzles 530. In Figure 20, for example, the first ceramic powder 523 coming out of a first nozzle 53Oe does not mix with the

second ceramic powder 524 coming out of a second nozzle 53Of and the layers 536 are well defined.

These layers 536 are successively released on first layer 513 so as to form on the latter the second layer 522 having coloured stripes 537, seen in Figure 19.

If all the nozzles 530 are supplied with the same predefined quantity of ceramic powder, each nozzle 530 can make a layer 536 having transverse dimension N. The transverse dimension N is substantially equal to a diameter of first end 532.

By "transverse dimension N" is meant a dimension of the layer 536 measured in a direction belonging to a plane defined by first wall 538 and parallel to movement plane R. Layer 536 having transverse dimension N, when deposited on first layer 513, forms a stripe 537 having width substantially equal to transverse dimension N. To obtain stripes 537 having width greater than transverse dimension N it is sufficient to supply two or more adjacent nozzles with a ceramic powder of the same colour. For example, Figure 20 shows a layer 536a made by supplying three side by side nozzles 530 with second ceramic powder 524.

Layer 536a thus shows a further transverse dimension M substantially equal to three times transverse dimension N. - Nozzles ...530.. can. ;also. r.form layers , 536 ,of.-.a still, further- transverse dimension Q less than transverse dimension N. To do so, one nozzle 530b, selected for making a layer 536b having a still further transverse dimension Q, must be adjusted so that it is closer to conveyor belt 520 in relation to a first side by side nozzle 530c and a second side by side nozzle 53Od, as shown in Figure 21. In this manner, nozzle 530b is buried in the ceramic powder released by other nozzles 530. Moreover, nozzle 530b must be supplied with a quantity of ceramic powder less than the predefined quantity, while the first side by side nozzle 530c and the second side by side

nozzle 53Od must be supplied with a quantity of first ceramic powder 523 greater than the predefined quantity. In this manner, a first layer 536c and a second layer 536d, made by means of the first side by side nozzle 530c and the second side by side nozzle 53Od, respectively, crush layer 536b determining its still further transverse dimension Q. The first layer 536c and the second layer 536d however develop a first transverse dimension and a second transverse dimension greater than transverse dimension N, respectively. In the example of Figure 21, nozzle 530b is supplied with a second ceramic powder 524 while side by side nozzle 530c and second side by side nozzle 53Od are supplied with first ceramic powder 523. In this way, by selecting a suitable quantity of powders to be supplied to each nozzle 530 and adjusting it suitably, it is possible to obtain a considerable range of decoration with substantially parallel stripes.

For example, it is possible to obtain stripes of required width greater than transverse dimension N and different from one of its multiples by suitably flanking and adjusting nozzles 530 supplied with the same ceramic powder. In addition to this, each nozzle 530 can be supplied with different coloured ceramic powders to obtain decorations with more than two..,colours .. Successively., . _^ th'e- first., layer .513--.and'.-:the -second, layer- 522.,. deposited on top of the first layer 513, are moved by conveyor belt 508 towards pressor means 509.

The pressor means 509 is arranged for carrying out a first forming step during which the first layer 513 and the second layer 522 are compacted together.

Pressor means 509 is arranged above belt 520 and comprises two further end rollers 540 on which a pressor belt 541 is wound in a closed loop arranged for compressing first layer 513 and second layer 522.

In this first forming step, the first layer 513 and the second layer 522 are compressed in such a way as to form a continuous sheet 542 of ceramic material.

The continuous sheet 542 is moved by conveyor belt 508 to the cutting device 510.

Cutting device 510 is positioned above belt 520 and can move towards the latter to cut the continuous sheet 542 to obtain rectangular shaped semi-finished ceramic products 543 having predefined dimensions. Cutting device 510 comprises a first rotary circular blade 544 arranged for cutting a continuous sheet 542 along a direction transverse to the advance direction F and a plurality of rotary circular blades 545 arranged for cutting the continuous sheet 542 substantially parallel to the advance direction F.

The semi-finished ceramic products 543 thus obtained reach one of the two end rollers 519 and are offloaded by the conveyor belt 508 on to conveyor means 511. Conveyor means 511 is arranged for transferring the semi- finished ceramic products 543 to a press 512.

The conveyor means comprises a plurality of rollers 46 driven by further motor means not shown in Figure 18. The semi- finished ceramic products 543 are moved by rollers 5.46 near ..press.512 on to which they are unloaded by conveyor .means 511:

Press 512 is a known kind of press arranged for carrying out a second forming step during which the semi-finished ceramic products 543 are further compacted for forming unfired tiles 544. The unfired tiles are successively fired in known type of kilns (not shown) to obtain tiles having a striped decoration.

During the first pressing step and the second pressing step, the stripes 537 are not deteriorated and remain well defined.

It is thus possible to obtain at the end of a firing process, tiles having a striped decoration with a pleasant and natural appearance .

By moving the nozzles 530 during the forming step, the stripes 537 may not be parallel to one another and may not be parallel to the sides of tile 501 produced. Figures 22 to 24 show an embodiment of apparatus 506 wherein the nozzles 530 are replaced by a dispensing member 550, comprising a body 600 which is shaped approximately like a parallelepiped and made of non-stick, anti-friction material, for example, polytetrafluoroethylene (PTFE). Body 600 comprises an outlet face 553 and an inlet face 552, parallel and opposite each other. As shown in Figure 22, dispensing member 550 is positioned (by means of supporting means not shown) near box frame 525 so that, during use, outlet face 553 is adjacent to inlet opening 527 of box frame 525. A plurality of inlet holes 554 are made in inlet face 552, forming two rows parallel to each other and offset, while a plurality of outlet slots 555 is made in outlet face 553.

In an embodiment not shown, a single row of inlet holes 554 is provided in inlet face 552.

A plurality of cavities 55Od (Figure 24) is made in the thickness .of. body..600,...each, of . which comprises an . inLst portion. 556, .opening -to -the outside, by:..means, of... the corresponding inlet opening 554, and an outlet portion 557 opening to the outside by means of the corresponding outlet slot 553. An end of the corresponding supply tube 535 is inserted through inlet hole 554 in each inlet portion 556, owing to which supply tube 535 it is possible to supply cavity 55Od with the first ceramic powder 523 or the second ceramic powder 524. The feed tubes 535 are flexible and made of a polyamide material . In the version of apparatus 506 shown in Figure 22, a feed hopper 551 provided with a plurality of walls 552 is used. The walls 552 are arranged reciprocally parallel and

transverse in relation to a longitudinal axis (not shown) of the feed hopper 551, so as to define in the latter a plurality of chambers 553 from which feed tubes 553 are given out, connecting the feed hopper 551 with cavities 55Od of dispensing member 550. It is possible to supply the chambers 553 with a plurality of different coloured ceramic materials and/or different mixtures of coloured ceramic materials, thus making it possible to obtain specific and valuable chromatic effects in tile 501. When apparatus 506 is working, the coloured ceramic materials are dispensed by dispensing member 550 in a manner similar to that described earlier with reference to nozzles 530. The dispensing member 550 makes it possible to avoid undesirable phenomena of blockage which could occur in dispensing nozzles 530. Moreover, the outlet slots 553 make it possible to produce extremely thin stripes 537 thereby significantly widening the range of aesthetic effects that can be obtained owing to the invention. Consequently, to produce layer 536a of Figure 20 using dispensing member 550, in order to obtain tiles 501 having significantly broad stripes 537, it is necessary to supply more feed tubes 535, and therefore more cavities 55Od, with the same coloured ceramic material. By using dispensing member 550 it is possible to produce tiles ..501 ..of Figure 16, . i.e. tiles _ having.-.rectilinear stripes .. as. ,..well.-:.as". -non i rectilinear., -stripes .53-7...- .Jf dispensing member 550 is kept fixed inside apparatus 1, tiles having rectilinear stripes 537 are produced. Figures 28 and 29 show, respectively, a tile 501a having stripes 561 in the form of broken line and a further tile 501b having curvilinear stripes 562. Tiles 501a and 501b can be produced by moving dispensing member 550 alternatively

(during the working of apparatus 1) in two directions, reciprocally parallel and opposite, indicated by arrows Fl and F2 , transverse in relation to the advance direction F. By suitably combining the transverse movements of dispensing member 550 in the two directions Fl and/or F2 with the

advance direction F, it is possible to produce the curvilinear stripes 562 and broken line stripes 561. In an embodiment not shown, dispensing member 550 is moved in two directions Fl and/or F2 by a moving device, comprising a known type of crank-handle system acting on dispensing member 550 and driven by an electric motor. This embodiment makes it possible to produce the curvilinear stripes 562. In another embodiment not shown, dispensing member 550 is moved in two directions Fl and/or F2 by means of a further moving device, comprising a toothed belt mounted on pulleys and driven by a "brushless" stepping electric motor. A stepping drive can be used to move dispensing member 550 in such a way that it makes particularly precise movements. This embodiment makes it possible to produce the broken line stripes 561.

Figure 25 shows a dispensing member 550a, on the inlet face 552a of which inlet holes 554 are arranged (in groups of three) in such a way as to form a plurality of rows, which are parallel to one another, arranged transverse in relation to the longitudinal axis of dispensing member 550a and reciprocally offset. Dispensing member 550a is consequently provided with a plurality of cavities (not shown) , included between inlet face.5.52a. of .. dispensing member 550a . and Its outlet.- face ^r (not_ shown), : .-The ..cavities. -.of-.".dispensing...member 550a open to the outside near the outlet face, through an outlet hole 558, which is circular like inlet hole 554. Figure 26 shows a dispensing member 550b, the inlet face 552b of which is provided with circular inlet holes 554, while the outlet face is provided with corresponding square shaped outlet openings 559.

Figure 27 shows a dispensing member 550b, the inlet face 552b of which is provided with circular inlet holes 554, while the outlet face is provided with corresponding lozenge shaped outlet openings 560.

Dispensing member 550a, 550b, 550c can be used in the embodiment of apparatus 506 described with reference to Figure 22.

During the working of apparatus 506, the cavities of 5 dispensing member 550a, 550b, 550c receive corresponding ends of feed tubes 535 through corresponding inlet holes 554, so that they can be supplied with coloured ceramic powders coming from the feed hopper. The latter are dispensed to the box frame 525 through outlet holes 558, or

10 the outlet openings 559, 560 (depending on the dispensing member used) .

During the working of apparatus 1, the dispensing member 550a, 550b, 550c is moved in two directions Fl and/or F2 by means of a moving device (not shown) , comprising a toothed

15 belt mounted on pulleys and driven by a "brushless" stepping electric motor. A further moving device is provided, also of the stepping type, arranged for moving dispensing member 550a, 550b, 550c in the advance direction F and/or in a further direction (not shown) parallel and opposite to the

20 advance direction F. Since dispensing member 550a, 550b, 550c can be moved in the transverse as well as longitudinal direction (in relation to apparatus 506) , by suitably combining the longitudinal movements and transverse movements,, of .dispensing member 550a, ..55.Qb,.._.550c,. it is -25. possible >to make .tiles .~:(not :. shown)- -having, decorations.-, with, squares. By supplying dispensing member 550a, 550b, 550c with a plurality of ceramic powders of different colours, suitably selected and matched, it is possible to make tiles having polychromatic decorations that are particularly

30 valuable from an aesthetic point of view.