EP0115361B1

EP0115361B1 - Ceramic tile with its rear configured as uniformly distributed hexagonal cells

Info

Publication number: EP0115361B1
Application number: EP84200045A
Authority: EP
Inventors: Lodovico Bardelli
Original assignee: Mass SpA
Current assignee: Mass SpA
Priority date: 1983-01-28
Filing date: 1984-01-13
Publication date: 1987-07-22
Also published as: IT8346810A0; EP0115361A1; ATE28488T1; DE3464941D1

Abstract

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.

Description

The present industrial invention patent relates to a special configuration of the reverse face of ceramic paving or facing tiles.
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.
For example, in the case of the tile of 20 x 20 cm format, twelve frusto-conical studs are normally provided having an area of about 1 cm² at their summit. Such known tiles have drawbacks which have not yet been obviated.
Ceramic tiles corresponding to the first part of claim 1 are known from US-A-1.702.912.
A first drawback derives from the fact that the clay is more compacted at said studs or ribs 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.
Furthermore, again because of said different degrees of compacting, corresponding differential shinkage is obtained during the firing this negatively influencing the planarity of said support and the linearity of its sides.
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.
In addition, the presence of said studs or feet hinders comfortable and correct transfer along roller conveyors, as take place for example in single-layer firing kilns.
Finally, this known tile configuration leads to a relatively small coefficient of grip, in particular in the case of facing tiles.
The present invention as claimed is able to obviat-3 the aforesaid.
Furthermore, according to the invention, tile 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.
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.
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 non-limiting 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.

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 tile, with the exception of a narrow peripheral rim 2 which is internally coplaner with said rear whereas externally it is bevelled, is provided with a plurality of uniformly distributed hexagonal impressions 3.
As is clearly shown, these impressions 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.
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.
The density of these impressions 3 is therefore between 4 and 1.5 impessions per square centimetre.

Claims

1. A ceramic tile (1) with a substantially planar rear surface which, within a narrow peripheral rim (2), contains a plurality of polygonal impressions (3) distributed in the manner of regular cells, characterised in that the impressions (3) are hexagonal and all have the same depth and are distributed contiguously in the manner of a honeycomb over the whole rear surface with exception of the rim (2).

2. A ceramic tile as claimed in claim 1, characterised in that said hexagonal impressions (3) have a depth of 0.5 to 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 length 3-5 mm.

5. A tile as claimed in claim 1, characterised in that the impressions are distributed at a density of 1.5 to 4 impressions per square centimetre.