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(11) | EP 0 115 361 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Ceramic tile with its rear configured as uniformly distributed hexagonal cells |
| (57) A ceramic tile having a perfectly plane rear which is provided, within a narrow peripheral
rim (2), with a dense honeycomb grid (3), so as to obviate internal stresses during
firing and the formation of glazed zones of different tones, and to obtain a high
coefficient of grip. |
[0001] The present industrial invention patent relates to a special configuration of the reverse face of ceramic paving or facing tiles.
[0002] Normal ceramic tiles are known to be constituted by a clay support which after forming is fired and glazed by one of the known ceramic double or single firing processes. The reverse face or rear of these tiles is also known to comprise a series of feet or studs which have the double purpose of acting as spacers during the firing of the material when in a stacked condition, and of facilitating their grip against the respective surfaces on which they are laid.
[0003] For example, in the case of a tile of 20 x 20 cm format, twelve frusto-conical studs are normally provided having an area of about 1 cm 2 at their summit. Such known tiles have drawbacks which have not yet been obviated.
[0004] A first drawback derives from the fact that the clay is more compacted at said studs than in the adjacent zones of the corresponding support, so that the differently compacted zones react differently to the application of the glaze and/or any decoration, so that different colour tones appear after firing said glaze and/or decoration.
[0005] Furthermore, again because of said different degrees of compacting, corresponding differential shrinkage is obtained during the firing this negatively influencing the planarity of said support and the linearity of its sides.
[0006] Moreover, because of this variable clay density, tiles which have just been formed are particularly sensitive to impact acting in the plane orthogonal to that in which they lie, for example during their transfer along conveying lines, and they are thus easily subject to breakage.
[0007] In addition, the presence of said studs or feet hinders comfortable and correct transfer along roller conveyors, as takes place for example in single-layer firing kilns.
[0008] Finally, this known tile configuration leads to a relatively small coefficient of grip, in particular in the case of facing tiles.
[0009] The present invention provides and protects a special tile rear configuration able to obviate the aforesaid. This is attained according to the invention by providing a tile rear having a plurality of uniformly distributed hexagonal cells which cover the reverse face of the tile with the exception of a narrow perimetral rim, and which have a depth of between 0.5 and 3 mm.
[0010] In substance, said tile rear is configured as a honeycomb, so as to provide a perfectly plane rear resting face. Furthermore, according to the invention, a tile with this rear has very regular cross-sections, so that a tile which has just been formed is uniformly compacted and thus more resistant to impact, and during its firing there is almost regular shrinkage without appreciable variation in the planarity of the support or in the linearity of its sides, and its front face reacts uniformly to the application of glaze and/or decoration.
[0011] In addition, the planarity of the rear in no way hinders correct transfer of the corresponding tiles by roller conveyors. Finally, the tile rear according to the invention provides a coefficient of grip which has not been obtainable up to the present time.
[0012] The constructional characteristics and merits of the invention will be apparent from the detailed description given hereinafter with reference to the figures of the single accompanying drawing, which illustrates a particular preferred embodiment by way of nonlimiting example.
Figure 1 is a plan projection of a ceramic tile provided with a rear according to the invention.
Figure 2 is a partial section on the line II-II of Figure 1.
Figure 3 shows the encircled detail III of Figure 2 to an enlarged scale.
[0013] Said figures show a ceramic tile 1 of right square or rectangular shape, but which can assume any other known tile shape. The plane rear of this latter, with the exception of a narrow perimetral band 2 which is internally coplanar with said rear whereas externally it extends into a bevel, is provided with a plurality of uniformly distributed hexagonal impressions 3.
[0014] As is clearly shown, these latter are disposed in mutually offset rows and columns, so that said impressions 3 are distributed in the manner of honeycomb cells. In addition, with particular reference to Figures 2 and 3, it can be seen that the ribs which separate two adjacent impressions are tapered at their summit in order to enable the corresponding forming die to be extracted.
[0015] According to the invention, the depth of these impressions 3 is of the order of 0.5-3 mm, and the average thickness of the separation ribs is between 1 and 2.5 mm. In addition, the side of the hexagon can vary from 3 to 5 mm, and is preferably 4 mm.
1. A ceramic tile as heretofore described, characterised by comprising a perfectly
plane'rear which, within a narrow peripheral rim (2), contains a plurality of hexagonal
impressions (3) distributed in the manner of a honeycomb.
2. A ceramic tile as claimed in claim 1, characterised in that said hexagonal impressions
(3) all have the same depth, namely between 0.5 and 3 mm.
3. A tile as claimed in claim 1, characterised in that the ribs which separate two
adjacent impressions are tapered towards their summit and have an average thickness
of 1-2.5 mm.
4. A tile as claimed in claim 1, characterised in that said impressions have a side
of 3-5 mm.
5. A tile as claimed in claim 1, characterised in that the impressions are distributed
at a density of 1.5-4 impressions per square centimetre.