FR2471355A1 - PROCESS FOR THE MANUFACTURE OF CERAMIC ARTICLES, PARTICULARLY FREE OF GLACURE, ESPECIALLY CERAMIC TILES WITH A DECORATIVE PATTERN - Google Patents

Abstract

THIS PROCESS CONSISTS THAT EITHER BEFORE COOKING ITEMS, EITHER AFTER THIS COOKING, WE REMOVE EITHER THEIR MOLDING SKIN, EITHER THEIR COOKING SKIN, BY JETS OF SAND AND USING ELASTIC PREFERABLES, THIS SKIN REMOVAL BEING FOLLOWED BY THE POSITIVE OR NEGATIVE SHAPE OF THE DESIRED DECORATIVE PATTERN. A TREATMENT, FOR EXAMPLE AN IMPREGNATION OF WAX, CAN BE CARRIED OUT ON THE STRIPPED SURFACES.

Description

_-1 - The present invention relates to a method of manufacturing articles

ceramic, in particular

devoid of glaze, in particular ceramic tiles

  mique, with a decorative motif.

  To make ceramic tiles with a decorative pattern, several methods have been developed to make it less costly to produce

of the decorative pattern compared to the serial process

  graphics always most often used The possibilities

capabilities offered by the most recent processes are certainly limited, but have nevertheless given birth to

  items with their own invoice and which have

chi the technique.

The object of the invention is to design another economical method for applying a decorative pattern on ceramic tiles. To this end, the invention provides either for removing the molding skin from the tiles before their firing, or, after their firing, for removing their hedgehog skin, this removal taking place, in one case as in the other, according to the positive or negative shape of the desired decorative pattern 0 In the ceramic pte it occurs, on the surface,

  during the hedgehog, slightly different transformations

  rents of those which occur in depths because the external surface is subjected to other conditions, The cooking atmosphere which, as a rule, is not neutral but on the contrary is either oydante, or reducing, stexes on the surface more strongly than in the thickness of the article; in addition the surface of the latter reaches higher temperatures because it directly receives the cooking heat, especially under

  a form of radiated heat which then does not reach the

inside the article only by conduotion, It is under these conditions that the cooking skin forms on the surface

  mentioned above and which is constituted by a ctu-

  ohe thick from 0.05 to 0.5 mm whose coloring oxides have slightly different oxidation stages from those in the thickness of the articles, so that the skin

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  -2 - cooking has a slightly different color from that of the material below it. In addition, this skin has # when it comes to porous pasta

greater density than the inner material.

  The formation of the cooking skin is, in the case of debauchery obtained by press molding or by oxtrusion, further favored by the molding skin which these blanks have and which is mainly formed by the fact that a certain amount of water is expressed from

the molded mass and accumulates under the punch of the press

  or to the wall of the extruder matrix, so that the surface of the blank is somehow joined and in any case made more dense. This higher density of the ceramic mixture promotes and accelerates

changes during cooking, so that

  As a result, the dough has a superficial layer.

  slightly different in appearance from the inside.

It is for this reason that we most often associate in a single concept the molding skin and the skin of

cooking.

It is of this texture different from the layer above

cooked dough in relation to the interior texture that the invention takes advantage of, either by removing

  in places the cooking skin and leaving the ma-

  interior surface of the dough thus exposed, constituting the exterior surface of the ceramic article, ie

  remove before baking the skin by

straight, so that at the places thus stripped the cooking skin forms without the initial base of a skin of

  molding and therefore has a less mar-

  as that of the cooking skin which is formed on a

  molding skin and which, therefore, stands out easily-

  is lying. The places where the molding skin was

removed can cut not only directly

visually, that is to say in particular by a difference in color and smoothness, but also by properties, such as in particular the porosity, which make it possible to achieve visual differentiation by 3-

a simple subsequent treatment, for example an impregn

  generation. The various possibilities outlined above do not

  are not mutually supportive and can also be

  hedged together, which increases dliver-

sification of surface aspects.

  The molding or baking skin can be removed as well according to the positive shape of the decorative pattern

  to create that according to the negative form of it, it is

  ie by removing the molding or baking skin around

of the decorative motif.

  It goes without saying that in the case where there is between the molding or baking skin and the interior of the raw or cooked dough a transient layer, it is sufficient, to implement the invention, to remove the skin only on

the depth necessary to obtain a no-difference

  table between the material of the initial surface and that

stripped naked.

  Removal of molding or baking skin

is possible by different means, for example by

lage; in the case of molding skin, less hard than

  the cooking skin, it can be removed by scraping.

  However, this grinding or scraping limits the choice of

decorative pattern. On the other hand, this choice becomes practical.

only unlimited when, according to a feature of the invention, the molding skin or the cooking skin is

  removed by Sand Jets and using po-

  choose. The invention is thus implemented with all its value ed compared to the result obtained, the means

used could not be simpler.

The process according to the invention is of importance

particularly in the manufacture of ceramic bars

  mique without glaze. In fact, until now it was not possible during the mass production of this kind of tiles, to apply sX each of them, in surfaooe a decorative pattern of a determined shape. It was only possible to produce on the tiles1 during their molding that reliefs provided in ereux in the _4 _

  punch of the molding press, and these parts in re-

  lief appeared in color only by the fact that the slip deposited in place of the glaze flowed over them. In addition, between the light and dark areas of the slip, only blurred and irregular boundaries could be obtained. On the other hand,

removal of molding or baking skin

  Even the process according to the invention can be effeo-

  killed on such a minimal depth that on the one hand the image obtained exerts an essentially flat effect, devoid of relief, and that, on the other hand, this image can be given very fine contours. In addition, the equipment necessary to implement the method according to the invention is

much more reduced while the possibilities of varia-

  tion are considerably more numerous, Another avan-

  not least, is that the process according to the

vention makes it possible to cook the tiles stacked on top of each other

  others. Finally, cleaning is made easier.

  There is nothing to prevent, however, that, by the process

  according to the invention, decorative patterns in relief then-

feels to be created. The depth of material removal is indeed not limited. One can thus, by playing on the height of the steps between the exposed surfaces and the others, more or less emphasize this particularity of the process according to the invention. Regarding this possibility of creating a relief, the new process can

  therefore lead to a new product.

  The abrasion resistance of the new ceramic tiles could not be higher, because the decorative pattern is formed by the ceramic paste itself and

either by the application of another material which, in

  general, is less hard. The process according to the invention

  tion is also fundamentally compatible with the ap-

plication of a glaze.

In an advantageous embodiment of the invention

the surface of the tile can be subjected to a treatment

particularly with an impregnation of wax, oil

linen, etc., to which the surface area reacts differently

  ment of the surface that has retained the molding skin or

Cooking. This treatment can be carried out not only-

  - ment with the aim, already indicated, of visually highlighting the stripped surface, but also and above all of strengthening and / or modifying the visual difference between stripped surfaces and surfaces which have retained their skin. Impregnation carried out with wax or

  linseed oil generally makes the overs darker

  bare faces, which absorb much more

  the impregnating agent as the cooking skin,

and such an impregnation generates a mat patinated crtain.

  Other impregnations can of course be envi-

  wise. We can also achieve a contrast between the surfaces with or without skin by deviating a little from the usual cooking conditions and ensuring that these conditions are such that they cause a difference between the color and / or the porosity of the hedgehog skin and that of the dough, or that they optimize a

such a difference. Depending on the circumstances, we can strengthen

cer the difference in color for example by causing a

fairly noticeable excess or defect in air.

The stencils may, as known in silk, be made of an elastic material which resists impact stresses.

Since the c,% hes are very easy to make

  quer, the process according to the invention ensures, in the manufacture

cation of large ceramic artioles a sou-

  plesse unknown hitherto with regard to the variety of decorative motifs. We can now satisfy the specific wishes of customers and even consider individual manufacturing, such as for example the making of coats of arms. We can also present customers with a large selection of decorative patterns. Furthermore, the method according to the invention is just as

  advantageous in the case of large series.

  For mass production, a device is proposed in which, directly above a strip

conveyor on which car blanks rest

  reaux (before cooking) or cooked tiles, is arranged parallel to this strip a strip of stencils which

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moves at the same speed as the said conveyor belt

at least one downward facing sandblasting nozzle or at least one

  sand centrifuge also directed downwards.

  The stencil strip is preferably part of a stencil circuit. Stencils can be individual

or, as described in the invention patent application,

tion DE-CS 25 53 846, be linked together to form an endless band, the implementation of the method according to the invention becoming however simpler than in the

case of said patent application.

  For sanding we can use the materials

  more diverse, for example quartz sands, corin-

silicon doni, glass beads, metallic granules, etc. Finally, in the manufacture of ceramic tiles

  presenting a decorative motif, the process according to the invention

  tion allows a very economical form of execution consisting

  both to separate the decoration operation from the manufacturing operations and to execute the decoration operation only on demand, from the storage store. This way of operating reduces inventory to a small fraction

  of the volume which would be necessary without the invention and fa-

  considerably limits the arrangements to be made to respond to orders. We save not only the often long shopping period, before the

sale, of certain decorative motifs, but also of the ma-

  gasing at all. The risk of unsold goods disappears

tick. In the case of tiled surfaces consisting in part of decorated tiles and in part of tiles having the basic shade, the method according to the invention implemented after storage of the tiles has furthermore

  particular advantage of ensuring without difficulty

absolute cordance of the decorated tiles as well as

  reaux not decorated, from the point of view of the basic shade, because all the tiles can have undergone absolutely the

  same manufacturing process until they are

will be decorated or sold.

-7- The proo6dé according to the invention is prgte in particular to be implemented on ceramic tiles of

all kinds, such as wall tiles

  floor, facade plates, tiles for stoves etc .; it can also be implemented on other

ceramic objects.

An example of execution of a floor covering slab provided with a decorative pattern according to the invention is shown in the drawing. The basic color of this slab is that of the molding and baking skin, for example a brown beige on a smooth surface. The decorative pattern was produced by sandblasting the molding and baking skin, using a stencil. The color of this motif was made a little darker by treatment with wax; she has become

  brown drawing on the black and the surface forming the

sin is a little rougher, but of a matt gloss, The very great sharpness of the contours of the doécora motif._

tif and its angles is characteristic of the process

lon the invention.

Claims (9)

  1. Method for manufacturing ceramic articles,   in particular devoid of glaze, in particular of car- ceramic reaux, comprising a decorative pattern, this process being remarkable in that either before the firing of these articles the molding skin is removed from them, or after firing the baking skin is removed from them, these removals taking place one or the other depending on the   positive or negative shape of the desired decorative pattern. at 2. Method according to claim 1, remrquable in that the molding or baking skin is removed by Jets of sand using a stencil, preferably requires an elastic stencil. 3. Method according to claim 1 or 2, remarks- quable in that the surface of the article is subjected to a treatment, in particular an impregnation, to which the stripped surface reacts differently. ment of the surface that has retained its molding or baking skin. 4. Method according to any one of the claims previous, remarkable in that the conditions of   are set to produce a difference in their and / or porosity between that of the cooking skin and that of the parts devoid of this skin.   5. Method according to any one of the claims previous, remarkable in that the decorative pattern is executed on demand on stored items after cooking.   6. Method according to any one of the claims previous remarkable what only part of a lot of otherwise identical tiles is decorated.   7. Device for implementing a method according to any of the preceding claims,   remarkable in that directly above a strip   conveyor on which car blanks rest   reaux (before cooking) or cooked tiles, is available   placed parallel to this strip a strip of stencils   which moves at the same speed as the said tape trans- porous and above which at least -9 is installed - a blast nozzle directed downwards or at least   a sand centrifuge directed downwards. 8. Device according to claim 7, remarks-   quable it that the stencil strip is part of a stencil circuit.   9, Device according to claim 8 remarks-   quable in that the stencils are connected the tus to others in an endless band.