In the name of: Stefano Cassani domiciled in: Imola, via Casola Canina n. 51

DESCRIPTION OF THE INVENTION

The subject of the present invention is a method for quality control of all the ceramic products that undergo pressure formation and subsequent firing, such as tiles, ceramic slabs, dishes, refractory materials, bricks, special ceramic products (medical field, electronics, sintered materials for mechanical use, etc.).

Specifically, but not exclusively, it can be usefully applied in the ceramic industry for the production of big tiles or slabs, based on the sintering of ceramic powder materials which are prepared in granular form, for example in atomizers, from which their frequent name "atomized" derives, suitable for pressure formation, with which an intermediate raw product is obtained, subsequently subjected to firing in kiln, which is capable of giving it the final solid structural consistency.

All the production lines of tiles or ceramic slabs using the above mentioned sintering are equipped with at least one pressure formation area, of which a product goes out, consisting of a raw tile or slab, which is subsequently subjected to drying, . glazing and firing in kiln, in which it assumes the final solid structural conformation. The part of the line downstream of the kiln is equipped for various operations on the slabs or tiles, such as acceptance and rejection of the faulty products.

The incidence of faulty products depends obviously on the production quality level as well as the economical result thereof since a rejected or non saleable article cannot be recovered and can be at the most partly recycled as a raw material, therefore subjected again to the whole preparation cycle so as to contribute to form new atomized material. Therefore, it is important to obtain processes and production lines for the production of ceramic tiles, in which the rejected items are minimized. In known solutions this is generally obtained either by casual sampling of atomized powder with subsequent laboratory tests or near the end of the production process, when the single piece has been already subjected to all the operations of the production cycle and certainly to the most expensive ones, such as forming, glazing and subsequent firing.

The described situation is further sharpened by the fact that it is common practice, currently, to produce big tiles or slabs and obtain smaller dimensions by cutting them, which is advantageous also because it eliminates calibration problems. A further cutting operation can cause an increase of rejected items in the case of a big slab presenting faults and structural irregularities that would not appear in the absence of this operation, which in any case is an additional operation with respect to the traditional technology, in which the tile is used as taken from the kiln.

The main object of the present invention is to overcome the limits and disadvantages mentioned above and those deriving therefrom, giving rise to a method for the quality control of ceramic tiles or slabs which comprises systematic verify of previously selected characteristics of the powder materials for the production of the tiles or slabs, wherein said control is carried out on the production line before the forming operation. The materials are subjected to prefixed tests, so that the collected data are compared with the prefixed reference values, in such a way that, in the presence of deviations, a feedback system is operated with intervention of a computer provided with a dedicated supervisory software, which system acts on the machines working upstream on the preparation of powder material.

One of the advantages derives from the reduction of the problems that could arise during firing.

These and other objects and advantages are obtained by the present invention as described, illustrated in the enclosed drawings and claimed hereinafter.

The characteristics of the present invention will become more evident from the following description of some of its preferred embodiments illustrated by way of not limiting example with the help of the enclosed figures, in which:

- figures 1a and 1 b show the same basic block diagram of a first embodiment in a simple form and in a feedback including form;

- figures 2a and 2b show the same block diagram of a second embodiment regarding a plant provided with wet milling in the simple form and in the feedback including form;

- figures 3a and 3b show the same block diagram of a third embodiment regarding a first type of plant provided with dry milling in the simple form and in the feedback including form;

- figures 4a and 4b show the same block diagram of a third embodiment regarding a second type of plant provided with dry milling in the simple form and in the feedback including form.

The illustrated embodiments refer to as many production lines for ceramic tiles or slabs.

In particular, the lines represented schematically by block diagrams of figures 1a, 2a, 3a, 4a, correspond to "simple" uses of the invention, indicated as a whole with the words "powders control" like a simple operation introduced in the line.

The lines represented schematically by block diagrams of figures 1b, 2b, 3b, 4b, correspond to the uses of the invention indicated as a whole with the words "powders control" in the line, but with the upstream feedback use.

The technology used in the lines is based on the sintering of ceramic powder materials, which are prepared in granular form, for example in machines called atomizers, from which their frequent name "atomized" derives. The granular form of the atomized is suitable for a pressure formation, with which an intermediate raw product is obtained, that is already in the form of tile or slab, which is then subjected to firing in kiln, that is capable of giving it its final solid structural consistency.

The illustrated embodiments describe a method for the production quality control of ceramic tiles or slabs, which comprises systematic tests of previously selected characteristics of the powder materials, atomized material and the like, for the production of the tiles or slabs, on which said control is carried out in the production line, indicated in the figures as "powder control" prior to the forming operation.

Such control is carried out by subjecting the atomized powder materials and the like to prefixed tests. The collected data are compared with the prefixed reference values, in such a way that, in the simplest embodiments, see figures 1a, 2a, 3a, 4a, it is possible to promptly correct the atomized powder materials and the like, which supply the lines or acting manually on the machines that work upstream of the pressure formation area. This considerably improves the present technique of random sampling to be controlled out of the line in laboratory.

In the more complete embodiments, that is, in the production lines, in which the powder materials are prepared in the same line upstream of the forming, the collected data are always compared with the prefixed reference values, in such a way that, in the respective embodiments schematically indicated in figures 1 b, 2b, 3b, 4b, a real feedback control of the powders is carried out directly in the line in the presence of the detection of certain deviations. And this with intervention of a feedback system using a dedicated supervisory software, which acts on the machines working upstream of the pressure formation, atomizers, mills, etc., on the preparation of the powder material or on the machines working directly downstream or at the end of the area or line for preparation of the powder material composed of atomizers, mills, etc.

The previously selected characteristics of powder materials for the production of tiles or slabs consist mainly in mineralogical composition, granulometry or size, color and optical characteristics, density and humidity.

In any case, the possibility of feedback intervention, if certain deviations with respect to prefixed reference values are detected, is provided to act on the dosing of the raw materials in the production line, on the dry or wet grinding systems, and/or atomizer and/or wetting systems.

For example, in the feedback control regarding the wet milling indicated in figure 2b, it is possible to act, one by one or in various combinations, on the inlet flow rates of the various components, water flow rate, mill rotation speed. In the feedback control regarding the sifting, likewise indicated in figure 2b, in the case of most commonly used sifters, it is possible to act on the rotation speed of the eccentric masses and/or variation of the eccentricity of the masses.

In the feedback control of the atomizer, figure 2b, it is possible to act, one by one or in various combinations, on the variation of the flow rate and introduction pressure of the barbotine, hot air flow rates and/or temperature.

In the feedback control regarding the dry milling of figure 3b, the indicated types of feedback control can be carried out, one by one or in the various combinations, by an intervention on the inlet flow rates of the various components, and/or the mill rotation speed.

In the feedback control of the wetting, the intervention is carried out on the water flow rate and/or granulator, if present, for example varying its rotation speed.

In the feedback control of the sifting, in the case of most commonly used sifters, it is possible to act on the rotation speed of the eccentric masses and/or variation of the eccentricity of the masses.

In the feedback control regarding the dry milling of figure 4b, the indicated types of feedback control can be carried out acting one by one or in the various combinations, by an intervention on the inlet flow rates of the various components and/or the mill rotation speed.

In the case of the most commonly used sifters, the feedback control of the sifting can be carried out acting on the rotation speed of the eccentric masses and/or variation of the eccentricity of the masses.

The feedback control of the wetting is carried out acting on the water flow rate. The indicated adjustment interventions are carried out on the basis of the deviations with respect to prefixed values, which are characteristic of the parameters defined experimentally for each product, by the detection or measurement of the previously selected characteristics of powder materials for the production of tiles or slabs are implemented by an equipment for spectroscopic analysis and, in particular, comprise equipment for absorption and/or emission spectrum analysis, preferably for infrared and near-infrared wavelengths. Raman spectrophotometers can be used for spectroscopic analysis.

In particular, the detection or measurement of the previously selected characteristics of powder materials for the production of tiles or slabs, dimension and humidity characteristics, are carried out by a possible combination with equipment for the optical analysis of the image and/or color detection.

In the case of a line for the wet powder preparation, in which the material wet ground in the mills is transferred to atomizers, the powder material produced by the atomizer will be subjected to an optical detection analysis combined with a spectroscopic analysis in the near-infrared or NIR, by which the values of percentage moisture and particle size can be detected. These values will be then compared with the prefixed reference values in such a way that, in the presence of certain deviations, a feedback system is operated with intervention of a dedicated supervisory software, which system acts on the machines working upstream on the preparation of powder material, such as mills, by varying their operating speed, by varying the flow rate and/or the transfer pressure of the ground material or barbotine from the mills to the atomizers, and/or by varying the temperature and air flow rate in the atomizers.

By allowing to control the characteristics of the starting powders, that is, those to be used in the subsequent pressure formation and firing phases, in a continuous way by a feedback, which in any case acts on the quality of the powder material, the illustrated method allows to obtain a high uniformity level. This allows to obtain an evident advantage in all the downstream operations. This allows to obtain an evident advantage in terms of productivity, continuity of the production quality, reducing the wastes deriving from the breakings before and during the firing or cutting, squaring and subsequent finishing, such as polishing and/or lapping.