Apparatus for producing a decorated ceramic product

The invention concerns an apparatus and a method for producing a ceramic product, specifically, a tile, having decorations imitating the veining of natural stones . In the ceramic field, apparatuses and methods are known for producing tiles in which the exposed face is made in such a way as . to simulate the veining of natural stones . These apparatuses comprise a conveyor belt on which a first layer of ceramic material powder is deposited by means of a first hopper for forming the base portion of the tiles . A second layer formed of ceramic material powders having various colours is deposited on this first layer for creating the exposed face of the tiles. For producing this second layer, ceramic powders of different colours are unloaded separately into a collector in which they are kept separate by means of walls which divide the internal cavity of the collector into non-communicating compartments. The various coloured ceramic powders flow out of the collector separately through an equal number of tubes, one for each colour, and are unloaded into a second hopper. The latter is placed above a dispensing device which is., in turn, above the conveyor belt and positioned downline of the first hopper. The second hopper is moved horizontally while it unloads the coloured ceramic powders into the dispensing device, below . it~ In, this.. manner, the various coloured powders fill .a cavity included, in the dispensing device and form in the latter a plurality of reciprocally overlapping layers having variable colour, thickness and extension. Consequently, as the conveyor belt moves forwards gradually and the dispensing device deposits the coloured ceramic powders on the first layer, the latter produce the second layer, comprising a plurality of striations having various shapes and colours. In the exposed face of the finished product, i.e. the fired tile, the afore-mentioned striations are intended to simulate the coloured and irregular veining of natural stones.

One disadvantage of the apparatus described above is that the veining that can be obtained is substantially broad and rather repetitive. It is therefore significantly difficult to obtain . ceramic tiles in which the exposed face effectively reproduces the variety of shapes and dimensions of the veining of natural stones, by using a known type of apparatus. Specifically, it is not possible to reproduce thin veining, due to stratification processes, visible in natural stones . One object of the invention is to improve the known apparatuses and methods for producing ceramic products, specifically, tiles.

Another object is to improve the known apparatuses and methods for producing ceramic products, specifically tiles, having exposed faces reproducing the appearance of natural stones.

A further object is to provide an apparatus and a method for producing ceramic products, specifically tiles, which make it possible to obtain fine and irregular veining in the exposed face of the products .

A still further scope is to provide an apparatus and a method for producing ceramic products, specifically tiles, in which the exposed face reproduces the stratification visible in natural stones effectively In a first aspect, of the invention, an. apparatus is .provided for forming ceramic products, comprising dispensing means, arranged for dispensing on a surface a layer formed of a plurality of flowable ceramic materials, distributor means arranged for distributing said ceramic materials in said dispensing means, duct means arranged for conveying said ceramic materials separately in said distributor means, characterized in that said duct means comprises a plurality of conveyor ducts for each of said ceramic materials. In a second aspect of the invention, a collector is provided for flowable ceramic materials, comprising a plurality of reciprocally separated compartments, characterized in that

each compartment is provided with a plurality of outlet means .

In a third aspect of the invention, a method is provided for producing ceramic products, comprising supplying dispensing means with a plurality of flowable ceramic materials, dispensing said plurality of flowable ceramic materials on a surface by means of said dispensing means in such a way as to form a layer of said ceramic materials on said surface, characterized in that said supplying comprises filling said dispensing means only partly.

Owing to these aspects, an apparatus and a method are made available for forming ceramic products, specifically tiles, which make it possible to obtain fine and irregular veining in the exposed face of the products, so as to effectively reproduce the stratification visible in natural stones.

In fact, in the apparatus and method according to the invention, the ceramic material powders of different colours are fed separately into a collector. Each coloured ceramic material powder comes out of a corresponding compartment of the collector through a plurality of outlet means, in the form of tubes, to which an equal number of conveyor ducts are connected, having a substantially reduced diameter and unloading the ceramic materials in the distributor means. The distributor ..means...comprises a hopper- moved..horizontally in xelation to. the' dispensing means . .These movable distributor means move and/or stop in predefined positions and for predefined times above the dispensing means, unloading the coloured ceramic materials into the latter in such a way that each coloured ceramic material forms a plurality of thin and irregular layers. Fine and irregular striations significantly similar to the veining of natural stones correspond to this plurality of layers in the exposed face of the finished tile. Moreover, since the mobile distributor means work in such a way as to fill the dispensing means only partly, the pigmented particles of the ceramic materials are induced to

flow obliquely, from the top downwards, inside the dispensing means, thus contributing to obtaining thin and irregular coloured layers. It thus becomes possible to effectively reproduce the veining and, specifically, the typical stratifications of natural stones.

In a fourth aspect of the invention, distributor means of flowable ceramic materials are provided, which can be incorporated in an apparatus for forming ceramic products and arranged for distributing said ceramic materials, in dispensing means of said apparatus, characterized in that they comprise at least one hopper portion and at least one distribution portion, said distribution portion being shaped in such a way as to separately receive a plurality of conveyor ducts of said ceramic materials ^' . Owing to this aspect, distributor means are provided which, by making it possible to obtain a plurality of thin and irregular veining in the exposed face of the products, are found to be significantly effective in reproducing the stratifications visible in natural stones. In one embodiment, the distributor means comprises a pair of distributor units which are positioned near opposite ends of the hopper portion and separately receive the plurality of conveyor ducts . The coloured ceramic materials are unloaded alternatively.., in one or...the other, of .the. two distributor. units,, arid, therefore in ..one or ...the. other of the opposite ends of the hopper portion. The distributor means thus makes it possible to fill the dispensing means only partly and the pigmented particles of the ceramic materials are induced to flow obliquely, from the top downwards, inside the - dispensing means, thus, contributing to obtaining thin and irregular coloured layers. Moreover, the flowable ceramic materials flow out of the distributor units through slot- shaped openings which make it possible to form significantly thin layers of pigmented particles. By overlapping the various thin layers, it is possible to reproduce on the exposed face of a ceramic product a chromatic stratification

effect extremely similar to the stratifications visible in natural stones .

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 an interrupted and incomplete schematic lateral view showing an apparatus for the production of ceramic products, comprising dispensing means, ■ movable distributor means and a plurality of conveyor ducts supplying the movable distributor means;

Figure 2 is an interrupted and incomplete perspective view showing the distributor means and the respective conveyor ducts of the apparatus of Figure 1; Figure 3 is a perspective schematic view showing the dispensing means and the movable distributor means in operation;

Figure 4 is a schematic plan view showing distributor means provided with distributor units; Figure 5 is a schematic lateral view of the distributor means of Figure 4;

Figure 6 is a schematic plan view of one of the distributor units included in the distributor means of Figure 4; Figure, 7 is a partially sectioned, schematic lateral view of the distributor unit of Figure 6;

Figures 1 to 3 show an apparatus 1. for forming ceramic products, specifically tiles 40. Apparatus 1 comprises a known type of belt conveyor 2 , on the upper branch 3 of which a base layer 6 of ceramic material powder 4 , having a prefixed and constant thickness is deposited by gravity by a known type of hopper 5, arranged near one of rollers 2a of belt conveyor 2. Belt conveyor 2, which is provided with a pair of side panels 35, 36 (Figure 3) for preventing ceramic material powder 4 from flowing out on the sides, conveys the base layer 6 in a feed direction indicated by arrow Fl, so as to bring base layer 6 near a dispenser frame 7, above the

upper branch 3. Dispenser frame 7 is arranged for depositing coloured ceramic material powders 8 by gravity on base layer 6, so as to form on the latter an exposed layer 9 having- a prefixed and constant thickness. Dispenser frame 7 (Figure 2) , arranged at right angles to feed direction Fl, comprises a wall upline 7a and a wall downline 7b, parallel to each other and supported by a pair of lateral columns 11, 12. The wall upline 7a and the wall downline 7b are shaped in the form of a quadrilateral and made of a rigid material, made and/or treated in such a way that the coloured ceramic powders 8 do not adhere to them accidentally. The wall upline 7a is made of non-stick steel, for example, steel with polytetrafluoroethylene (PTFE) coating, while the wall downline 7b is made of a suitable transparent material such as glass or polymethyl methacrylate (PMMA) .

In one embodiment (not shown) , both walls of dispenser frame 7 are made of rigid and transparent material . In another embodiment (not shown) , both walls of dispenser frame 7 are made of rigid and opaque material . The two walls 7a, 7b are spaced ^' from each other to define a cavity 25, having constant thickness and closed on the sides by the pair of lateral columns 11, 12. The latter, together with the walls Ta, 7b, define a dispensing opening (not .shown) , facing belt conveyor 2/ and a .feed opening 10., opposite the dispensing opening. Dispenser frame 7 is positioned in relation to the upper branch 3 of conveyor belt 2 in such a way that the delivery opening is arranged near base layer 6. In this way, when dispenser frame 7 dispenses the coloured ceramic powders 8, the latter are deposited on the base layer 6 and form the exposed layer 9. Dispenser frame 7 is fed with coloured ceramic powders 8 by means of a collector 13, placed above dispenser frame 7, and a movable hopper 14, placed between the collector 13 and dispenser frame 7. In collector 13, which is substantially cylindrical-conical in shape, a plurality of compartments 15 are made (four, in the version seen in Figure 2) separated

from one another by a plurality of walls 16. Each of the compartments 15 supplies the movable hopper 14 below it with a coloured ceramic powder 8 of a predefined colour, and the latter is unloaded into the corresponding compartment 15 by a corresponding feed tube 18 provided at its end with a known type of dispensing device 17, having with a gate closure.

Each compartment 15 is provided with a plurality of rigid outlet ducts 20 of' small size, projecting from a base portion 19 of collector 13 in the direction of the movable hopper 14 below. Each outlet duct 20 is connected to a flexible outlet tube 21, having diameter similar to that of the corresponding outlet duct 20. The length of each outlet tube 21 is such as to be able to reach the movable hopper 14 and be received in the latter.

Collector 13 and the movable hopper 14 below it are mounted on the same movable frame 22,- which, owing to the known type of driving means (not shown) , can be moved horizontally in two directions, indicated by arrows F3 and F4, opposite to each other and parallel to feed opening 10 of dispenser frame 7. The latter is also provided with a guide plate 23

(Figure 2) near feed opening 10, in an approximately median portion of which a longitudinal feed slit 24 is made.

When apparatus 1 is in operation,, the f.eed tubes 1.8 unload the various coloured ceramic powders 8 into the respective compartments 15 of collector 13, in prefixed quantities at predefined times . The coloured ceramic powders 8 flow out separately from compartments 15 through the corresponding outlet ducts 20 and flow through outlet tubes 21 separately to enter movable hopper 14. The various coloured ceramic powders 8 are mixed in the movable hopper 14, while the latter, together with the collector 13 above it, slides alternately along the two directions F3 and/or F4 in a predefined manner. This means that the movable hopper 14 can move through a predefined distance, substantially corresponding to a transverse dimension of feed opening 10

of dispenser frame 7 , in direction F3 and/or F4. The movable hopper 14 can also stop for predefined times near prefixed areas of feed opening 10. The coloured ceramic powders 8 flow out of movable hopper 14 by gravity, cross ^" the feed slit 24 of guide plate 23 and enter cavity 25 of dispenser frame 7 through its feed opening 10.

As shown in Figure 3, if movable hopper 14 stops for a predefined time near one of the lateral columns, for example, the lateral column.12, the coloured ceramic powders 8 fall into cavity 25 and accumulate one on top of the other in a substantially asymmetric manner, thus filling cavity 25 only partly. In this manner, a flow area S is formed in cavity 25, arranged obliquely and corresponding to a surface free of coloured ceramic powders 8 between feed opening 10 and the lateral column situated in a position opposite to movable hopper 14 (in the case shown in Figure 3, lateral column 11) . When the pigmented particles forming each coloured ceramic powder 8 fall from movable hopper 14 on flow area S, they flow obliquely on the latter, from the top downwards, according to a direction indicated by arrow F5.

The flow area S and the fact that the coloured ceramic powders 8 reach the movable hopper 14 after they have been distributed between the numerous outlet tubes 21 co-operate t.o produce in cavity 25 a plurality of coloured layers..3.7-,.. which are reciprocally overlapping, thin and extremely, variable from one another in shape, length and colour. In this manner, when dispenser frame 7 dispenses the exposed layer 9 on base layer 6, the exposed layer 9 has a plurality of veinings 38 which derive from the corresponding coloured layers 37 and which, like the latter, are thin and vary in colour and length. This makes it possible to obtain tiles 40 having an exposed face 40a reproducing in a significantly faithful manner the aesthetic appearance and, specifically, the stratifications of natural stones . Figures 4 and 5 show a distributor device 26, which can be used in apparatus 1 in place of movable hopper 14. The

distributor device 26 comprises a supporting plate portion 21 in the shape of a rectangle and extending longitudinally, a pair of hopper portions 28a, 28b, each of which has a substantially triangular transverse section, and a pair of distributor units 60a, 60b (represented by the broken line) . In use, distributor 26 is supported by known type of supporting means, for example, a supporting frame (not shown), and positioned above dispenser frame 7. The supporting ^" plate portion 27 comprises a feed face 27a and a dispensing face 27b, which are parallel and opposite to each other. Two side elements 27c, 27d project from feed face 27a, parallel and opposite to each other, and extending along, the entire length of the supporting plate portion 27. When distributor device 26 is inserted in apparatus 1 and positioned there in a manner similar to that envisaged for the movable hopper 14 (i.e. near feed opening 10 of dispenser frame 7) , the dispensing face 27b faces the feed opening 10 and the feed face 27a faces collector 13. Hopper portions 28a, 28b are positioned near the opposite ends of supporting plate portion 27 and project from the latter' s dispensing face 27b. Each hopper portion 28a, 28b is provided with a rectangular inlet opening 29a, and an outlet opening 29b, shaped in the form of a slit and arranged, parallel to the supporting plate portion 2.7 and to the, respective inlet opening 29a . When distributor device 26 is inserted in apparatus 1, the outlet opening 29b is adjacent to and aligned with feed opening 10 of dispenser frame 7. Between the inlet opening 29a and outlet opening 29b there is a rectilinear wall 44, an oblique wall 41 and a pair of further oblique walls 42, 43. The rectilinear wall 44 and oblique wall 41 are shaped in the form of a triangle while the further oblique walls 42, 43 are shaped approximately in the form of a trapezoid rectangle. While the rectilinear wall 44 is arranged substantially at right angles in relation to supporting plate portion 27, oblique wall 41 is

inclined in relation to the latter, in such a way that an angle α of approx. 45° is defined between oblique wall 41 and supporting plate portion 27. In use, oblique wall 41 facilitates the flow and reciprocal mixing of the coloured ceramic powders 8 inside each hopper portion 28a, 28b.

Figures 6 and 7 show in detail the distributor units 60a, 60b, each of which comprises a body 61, shaped in the form of a parallelepiped and provided with an outlet face 6Od and an inlet face 60c, parallel and opposite to each other. Each distributor unit 60a, 60b is mounted on the supporting plate portion 27 of distributor device 26 in such a way that outlet face 6Od of distributor unit 60a, 60b is adjacent to feed face 27a of the supporting plate portion 27. Each distributor unit 60a, 60b is maintained in this position by means of side elements 27c, 27d of feed face 27a, with the body 61 of each distributor unit 60a, 60b placed between the side elements. Since the length of each body 61 is less than the length of each inlet opening 29a, each distributor unit 60a, 60b can be positioned near different areas of inlet openings 29a .

A plurality of duct portions 62b is made in the thickness of each body 61. Each duct portion 62b opens near inlet face 60c, by means of a circular-shaped hole 62, and near outlet face 6Od., by means of an elongated,.. and_. approximately rectangular slot 63. Each duct.', .portion 6.2b comprises a cylindrical inlet portion 62a, which narrows to continue into an outlet portion 62c, the transverse section of which resembles the shape of slot 63. When the distributor device 26 is inserted in apparatus 1, each inlet portion 62a receives (through the respective hole 62) a corresponding end of an outlet tube 21 coming from a feeding element (not shown) . Each distributor unit 60a, 60b can therefore separately receive as many outlet tubes 21 as there are duct portions 62b with which distributor unit 60a, 60b is provided. Outlet tubes 21 form two groups, each of which ^■ feeds a respective distributor unit 60a, 60b.

Distributor unit 60a, 60b shown in Figures 6 and 7 can receive up to 16 outlet tubes 21. In embodiments not shown, distributor units 60a, 60b are present, provided with a number of duct portions 62b more than or less than 16. In use, unlike what has been described above for the movable hopper 14 with reference to Figures 1 to 3 , distributor device 26 does not need to be moved to be able to operate. In fact, the coloured ceramic powders 8 conveyed through outlet tubes 21 towards one and/or the other of the two distributor units 60a, 60b, are dispensed by each outlet tube 21 connected to the respective duct portion 62b of distributor unit 60a, 60b required, when the corresponding slot 63 is above the inlet opening 29a of said hopper portions 28a, 28b, while dispensing of the powders stops when said slot 63 is outside the said inlet opening 29a. The powders dispensed by each outlet tube 21 fall by gravity into the corresponding hopper portion 28a, 28b and come out of its outlet opening, to enter cavity 25 of dispenser frame 7. Depending on the position in which each distributor 60a, 60b finds itself in relation to the inlet opening 29a, it is possible to change the formation of flow area S in cavity 25, which is arranged obliquely and lies between feed opening 10 and lateral column (11 or 12) situated in a position opposite distributor unit 6,0a, 6Qb.. The coloured ceramic powders 8 coming out of dis.trib.ut.ox units 60a, 60b through slots 63 form significantly thin layers which, by overlapping reciprocally in cavity 25, make it possible to reproduce a very likely stratification chromatic effect in exposed face 40a of tiles 40. In an embodiment not shown, distributor device 26 is provided with known type of driving means, which make it possible to move each distributor unit 60a, 60b in relation to inlet openings 29a according to one and/or the other direction F3 and F4, in relation to the inlet openings 29a. Downline of dispenser frame 7, apparatus 1 comprises a pre- compacting station 30 provided with a pressor belt 31, a

cutting station 32 and a known type of ceramic press 33. By depositing the exposed layer 9 on the base layer 6, a semifinished product 50 is obtained, which is pre-compacted in the known type of pre-compacting station 30, and then cut longitudinally and/or transversely in cutting station 32. The latter, of known type, comprises cutting disks 32a, arranged parallel to direction Fl, and further cutting disks 32b, arranged transverse to direction Fl. Once it is cut longitudinally and/or transversely, the semi-finished product 50 is then transferred to press 33 by means of a known type of roller conveyor 34. In press 33 the semifinished product 50 is transformed into an unfired tile 40 intended for being • fired by means of known type of apparatuses and procedures . In an embodiment not shown, tile 40 is obtained starting from a single layer of material in powder form, consisting of coloured ceramic powders 8 and produced according to the method described above. In this embodiment, apparatus 1, provided with movable hopper 14 or distributor device 26 does not comprise the hopper 5 meant for dispensing ceramic material powder 4.