METHOD AND SYSTEM FOR THE MANUFACTURE OF CERAMIC TILES OR SLABS WITH IRREGULAR OR JAGGED EDGES

Description

DESCRIPTION of the Italian Patent for Industrial Invention entitled: “METHOD AND SYSTEM FOR THE MANUFACTURE OF TILES OR CERAMIC SLABS WITH IRREGULAR OR JAGGED EDGES” on behalf of ANTICA CERAMICA RUBIERA SRL with headquarters in 42048 RUBIERA (RE). * * * * * Field of technology The present invention relates to a method and a plant for manufacturing tiles. or ceramic slabs with irregular or jagged edges. State of the art Ceramic tiles or slabs with irregular or jagged edges are known, which they are typically used to create wall or floor coverings, having a “rustic” appearance. Industrially, these ceramic tiles or slabs are manufactured with a traditional process, that is, pressing or compacting a raw support of ceramic powders and, after having subjected it to one or more phases of glazing and / or decoration, cooking at high temperature said support pressed inside a ceramic oven, in order to obtain the sintering and / or ceramization of the ceramic powders. To shape the edges of the ceramic tile or slab according to the desired profile irregular or jagged, before the glazing and / or decoration phases, the support raw material of compacted ceramic powders is generally subjected to la- mechanical processes that allow the removal, in a substantially causal and irregular, a part of the ceramic dusts which are localized in cor- edge fit. However, by doing so, the subsequent layers of enamel and / or ceramic ink used for decoration they also cover the irregular surfaces of the edges, by creating a vegetal layer on them after the cooking phase has been completed. troso which prevents, or in any case makes more difficult, the setting of the stuccos which They are normally used to seal the joints between ceramic tiles or slabs in the installation. Exposition of the invention An object of the present invention is to solve the aforementioned drawback. nothing of the known art, within a simple, rational and relatively low cost. This and other purposes are achieved by the features of the invention which are reported in independent claim 1. The dependent claims deli- preferred and / or particularly advantageous aspects of the invention but not strictly necessary for its implementation. In particular, one embodiment of the present invention makes available a method of making ceramic tiles or slabs having irregular or frac- outlined, including the phases of: - prepare a fired ceramic tile or slab with two opposing sides larger faces delimited along the perimeter by one or more lateral sides which they define with them respectively one or more upper edges and one or more lower edges, - chipping by mechanical action, for example using a suitable tool to remove material, at least one of said upper edges. Thanks to this solution, acting on a ceramic tile or slab already fired, the mechanical chipping action allows, not only to substantially remove initially random part of the ceramic powders placed along the edges, but also part of any layers of enamel and / or decorative paint that may have been applied above, thus facilitating and making the subsequent setting of the fillers more stable. who used to seal the joints. According to a preferred aspect of the invention, the chipping step may include to leave intact (i.e. not to chip) one or more of the, preferably all of them i, lower edges of the ceramic tile or slab. In other words, it is expected that the mechanical chipping action may concern only the top edges. This way, the bottom edges can remain perfectly straight and square, providing a safe reference for placing various ceramic tiles or slabs side by side during installation and also allowing the use of conventional devices spacers and levelers, which are used to place all the ceramic tiles or slabs mica at the same distance from each other and at the same level. According to another aspect of the invention, the chipping step may include create, along at least one side of the fired ceramic tile or slab, preferably along each lateral flank, a longitudinal groove suitable for define and separate two protruding longitudinal shelves, one of which is the upper shelf rear which includes the upper edge to be chipped, and a lower shelf which includes a lower edge. The creation of this longitudinal groove allows in fact to cause, or at least to facilitate, the substantially random breaking of the shelf upper and therefore the chipping of the edge defined by it. One aspect of the invention provides, for example, that the longitudinal groove can be achieved by means of a rotating tool, preferably a rotary disc many with tangential action. In particular, the longitudinal groove can be made using a mo- relative motion between said rotating tool and the fired ceramic tile or slab along a predetermined direction of translation parallel to the upper edge of the chip- to be such that, during said relative movement, the rotating tool comes into contact touch with the side of the fired ceramic tile or slab that defines the top edge to chip. Thanks to this solution, the creation of the longitudinal groove can be be advantageously automated. In case the creation of the groove is not sufficient in itself to also cause chipping of the edge, an embodiment of the invention provides that the chipping phase also includes the application phase to the upper shelf a force or pressure capable of causing it to break or crack capture. This breaking force or pressure can be directed, at least partially (ov- true can have at least one component), in a direction orthogonal to the major faces days of the fired ceramic tile or slab, preferably in the direction of pushing the top shelf towards the bottom shelf. Due to this force or pressure, the upper shelf tends to break in corre- slope of the section weakened by the groove, but in a substantially random and therefore irregular. According to one aspect of the invention, the breaking force or pressure may be exerted by means of a pressing body, for example a roller, which is placed at contact and pushing the top shelf. In particular, the breaking force or pressure can be exerted over the entire exten- longitudinal movement of the upper shelf by means of a relative movement between said pressing body and the ceramic tile or slab fired along a predetermined direction of translation parallel to the upper edge to be chipped, so that that, during said relative movement, the pressing body comes into contact and presses the upper shelf which includes the upper edge to be chipped. Thanks to this solution, the breaking or splitting phase of the upper shelf can be advantageously automated. In addition to the method outlined above, the invention also provides a corre- tooth implant to make ceramic tiles or slabs with irregular edges or jagged, which includes: - means for advancing fired ceramic tiles or slabs along a predetermined direction of advance, and - at least one tool capable of chipping, alone or in association with others means, by mechanical action at least one upper edge of said tiles or fired ceramic slabs, during the advancement. This embodiment of the invention achieves substantially the same effects and advantages previously mentioned in relation to the method. Of course all the subordinate aspects of the invention which have been outlined with reference to the method are applicable, mutatis mutandis, also to the corresponding plant. In particular, the tool may be a rotating tool, such as a disc tangential cutting action. The tool can be adapted to produce, along at least one lateral side of the plates ceramic slabs or plates a longitudinal groove that defines and separates two protruding longitudinal shelves, including an upper shelf comprising the top edge to be chipped, and a lower shelf that includes a edge inferior. The system can also include, if necessary, a pressing body suitable for to exert on the upper shelf a breaking force or pressure capable of causing flesh the breaking or splitting. Brief description of the drawings Further features and advantages of the invention will become apparent from reading of the following description provided by way of example and not limitation, with the au- silence of the figures illustrated in the attached tables. Figure 1 is a schematic axonometric view of a ceramic tile or slab. mica having irregular or jagged edges, according to one embodiment of the present invention. Figure 2 is a schematic axonometric view of a ceramic tile or slab. cooked and possibly squared mica, from which the ceramic tile or slab of figure 1. Figure 3 is the view of figure 2 shown during a subsequent phase of realization. tion of the longitudinal groove. Figure 4 is a schematic, reduced-scale side view of Figure 3. Figure 5 is the view of figure 3 shown during a subsequent pressing phase and splitting of the upper shelf which includes the chipping edge. Detailed description With the help of the figures mentioned, a method for making tiles is described. or ceramic slabs having irregular or jagged edges, of the type illustrated and indicated by 100 in figure 1. The method in question first requires preparing a ceramic tile or slab cooked mica 105 (see fig.2). By fired ceramic tile or slab 105 we mean a ceramic tile or slab which has already been subjected to a high temperature cooking process inside of a ceramic oven. In more detail, the fired ceramic tile or slab 105 can be obtained at starting from a soft (i.e. unpressed) mass of ceramic powder, which can be distributed on a supporting surface, for example in the form of a substantially flat layer of predetermined thickness. Ceramic powder can be obtained by grinding a mixture of ma- ceramic raw materials, including for example clays, talc, silica, feldspar minerals, carbonates, micas, glassy materials, etc. The raw ceramic material mixture can be dry ground, obtaining directly the ceramic powder, or it can be wet ground, for example obtaining the so-called slip, and then being subjected to a process of drying inside an atomizer. In this second case, the ceramic powder is called “atomized”. Subsequently, the soft mass of ceramic powder can be subjected to a pressing stage, for example using a ceramic press or compactor, which can be of a discontinuous or continuous type, in order to obtain a mass of pressed ceramic powder, which is conventionally called support raw ceramic. It should be noted that in ceramic jargon, "raw" support means, for example, the note, an artifact of pressed ceramic powder but not yet subjected to a cooking process. The pressure with which the soft mass is pressed can vary depending on the ceramic powders used, typically a minimum of 150 kg / cm (kilograms per square centimeter) to a maximum of 600 kg / cm . For example, in the case of porcelain stoneware, the pressure exerted on the mass 2 2 soft can be between 300 kg / cm and 450 kg / cm, more preferably between 2 2 350 kg / cm and 450 kg / cm . After pressing, the raw ceramic support can be possibly under- placed in a drying phase, during which it is heated to temperatures moderate inside a dryer in order to reduce the humidity of the wax powder miche pressed. Eventually, the raw ceramic support can be cut and / or trimmed in such a way to give it the desired shape and size. In any case, the raw ceramic support can generally present a shape planar which essentially corresponds to the shape of the ceramic tile or slab not cooked 105 final. In particular, it can include two larger faces, opposite and parallel. one to the other. On one of these larger faces of the raw ceramic support, typically that suitable for defining the visible face of the ceramic tile or slab, it can be even currently applied a layer of ceramic engobe. In general, a ceramic engobe is a mixture of inorganic raw materials. which is applied directly onto the mass of pressed powders (raw support) in order to cover any defects and inhomogeneities, make the surface more white and suitable for the subsequent decoration phases and to ensure a better match dilatometer between the support and the finishing enamel. The main components of a ceramic engobe are chosen from the group consisting of: clays, kaolins, feldspars, zirconium oxides, alumina, quartz and frits. The ceramic engobe layer has the function of levelling the roughness of the visible face of the ceramic tile or slab 105, making it less permeable to liquids. The ceramic engobe layer can be applied to the entire surface of the substrate raw ceramic, so as to cover it completely. Ceramic engobe can be applied using an airless applicator or qua- any other suitable device. Alternatively, the ceramic engobe can be applied with a digital glazer Drop on Demand technology. The ceramic engobe of the layer can have a density between 1350 and 1600 grams / liter (g / l), extremes included, for example substantially equal to 1450 g / l 1500 g / l. Furthermore, this ceramic engobe can be applied on the visible face of the support. 2 2 I carry raw ceramic in a specific quantity between 750 g / m and 1250 g / m, for example equal to 1000 g / m . The production method may also include applying the aforementioned larger face of the raw ceramic support, for example above the layer of ceramic engobe, one or more ceramic inks used to create a layer decorative, such as coloring and / or graphics. Each ceramic ink is generally made up of a suspension, that is from a mixture consisting of a finely divided solid material is dispersed in another material in a liquid state, typically so as not to settle in short time. The solid material present in the suspension is generally called fra- solid state, while the material in the liquid state is generally called liquid fraction or vehicle. In the case of ceramic inks, the solid fraction is inorganic in nature while the liquid fraction is organic in nature. In particular, the inorganic solid fraction may comprise one or more components selected from the group consisting of: calcined, coloured calcined, inorganic pigments, frits, inorganic oxides, (more or less) refractory inorganic oxides. The organic liquid fraction may comprise one or more components selected from the group consisting of: glycols, glycol ethers, esters derived from fatty acids, paraffins and naphthenes, esterified terephthalates, cyclohexane dicarboxylates, citrates, ester derivatives from benzoic acid, esters derived from the alcohol phenoxyethanol. To increase the range of decorations that can be created and the versatility of the process decoration, ceramic inks can be applied using one or more digital inkjet ceramic printers, which implement a ink-jet technology. After the possible application of the decorative layer, the above mentioned larger face of the raw ceramic support can be covered with a layer of a glaze ceramic covering, preferably transparent, which generally has the ef- to protect from oxidation, water and acids. Ceramic enamel can be applied using an airless applicator or qua- any other suitable device. In general a ceramic overglaze is a transparent glaze that is applied after decoration for protective purposes, to make the surface ma- daily waterproof, resistant to abrasion and chemical agents, to make the most vivid colours and to develop the desired light reflection effect (matt or shiny). To obtain a glaze, frits are used to which other additives are added raw materials. Some types of nail polish contain a high percentage of frits (even up to 95%), others, however, have a low percentage (around 20-30%). Among the raw materials used to make enamels there are: clays, kaolins, silica, calcium carbonates, magnesium, barium and strontium, alumina, Zinc oxide, etc.. Subsequently, the raw ceramic support can be subjected to the already men- cooking process, typically inside a ceramic kiln, so such as to sinter and / or ceramize and / or thermally consolidate the ceramic powders pressed micas and all the solid parts present in any various layers of coating chin applied on the larger face. This firing phase may involve heating the raw ceramic support until at a predetermined maximum temperature, which can vary between 550°C and 1400°C depending on the composition of the ceramic powder. In particular, the heating of the raw ceramic support can take place according to a set heating curve. The raw ceramic support can then be maintained at this maximum temperature for a certain amount of time, before cooling it. In any case, sintering and / or ceramization and / or thermal consolidation of the ceramic powders of the raw support, make the ceramic tile or slab mica 105 “cooked” acquires a solid consistency. Eventually, after firing, the ceramic tile or slab can be subjected to it is subjected to mechanical squaring processes, in order to give it a more rounded shape regular, for example a shape more similar to a perfectly square slab or rectangular. In any case, the fired ceramic tile or slab 105 will present, as anticipated, a planar shape having two larger, mutually opposite faces and pa- rallele, which are delimited along the perimeter by at least one lateral flank, whose height essentially corresponds to the thickness of the ceramic tile or slab cooked 105. In particular, the fired ceramic tile or slab 105 will normally have a square shape (e.g. rectangular or square) and will therefore be delimited along the perimeter composed of a quadrupole of substantially rectilinear, parallel and con- two by two, of which a pair of longitudinal sides 110 and a pair of transverse sides 115, for example substantially orthogonal to the longitudinal sides dinali 110. The larger faces of the fired ceramic tile or slab 105 may then include the (already mentioned) visible face, indicated with 120, intended to remain exposed and therefore to be visible after the 100 ceramic tile or slab has been laid in operation, and a 125 laying face designed to remain facing the surfaces to be cover and then hidden. The fired ceramic tile or slab 105 will also have one or more upper edges, defined at the intersection of the lateral flank(s) with the exposed face 120, and one or more lower edges defined at the intersection of the sidewall(s) with the laying face 125. For example, the fired ceramic tile or slab 105 may have a quaternary of substantially rectilinear upper edges, parallel and opposite in pairs, of which a pair of longitudinal upper edges 130, defined at the intersection of the sides longitudinal 110 with the visible face 120, and a pair of transverse upper edges salts 135, for example substantially orthogonal to the upper longitudinal edges 130, defined at the intersection of the transverse flanks 115 with the same visible face 120. the fired ceramic tile or slab 105 can also have a quaternary of lower edges, also substantially rectilinear, parallel and opposite to each other two, of which a pair of longitudinal lower edges 140, defined at the intersection of the longitudinal sides 110 with the laying face 125, and a pair of lower edges transversal 145, for example substantially orthogonal to the lower longitudinal edges nali 140, defined at the intersection of the transverse flanks 115 with the same face of pose 125. Starting from the fired ceramic tile or slab 105, the method being presented The invention provides for the chipping, by mechanical action, of at least one of the (preferably all) upper edges, e.g. 130 and 135, of the tile or la- fired ceramic stra 105, that is those defined between the lateral sides, for example 110 and 115, and the visible face 120, preferably leaving intact (i.e. not chipped) (giati) at least one of the (preferably all) lower edges, e.g. 140 and 145, that is, those defined between the lateral sides, for example 110 and 115, and the laying face 125. Thanks to this solution, each of the upper edges of the tile or slab ce- fired copper 105, for example 130 and / or 135, which is chipped, acquires the desired irregular or jagged profile which, remaining visible after installation in work of the 100 ceramic tile or slab, allows to give the covering thus obtaining a “rustic” look. At the same time, each of the lower edges of the ceramic tile or slab cooked 105, for example 140 and / or 145, which is not chipped and therefore remains substantially squared, it can be useful to allow an effective installation in work of the ceramic tile or slab 100. In particular, each of these lower edges, e.g. 140 and / or 145, can be be placed against a corresponding unchipped lower edge of an ana- logo tile or ceramic slab 100, so that these two ceramic tiles or slabs 100 mica, although presenting irregular and / or jagged edges to the eye, can be arranged in a regular manner towards each other. The fact that these lower edges, e.g. 140 and / or 145, are not chipped It also allows you to take advantage of the possibility of installing ceramic tiles or slabs during the installation miche 100, conventional spacers and / or levelers which are used to arrange two or more adjacent ceramic tiles or slabs at the right distance from each other and at the same level. These spacers and / or levelers are in fact generally equipped with a base on which the lower edges of the ceramic tiles or slabs rest, if they were chipped, they would not allow this base to perform its function effectively cement its function. On the other hand, mechanically chipping the upper edges, for example 130 and / or 135, of the ceramic tile or slab 105 when the same has already been cooked, it is advantageous as it allows for partial removal from said edges even any layers of engobe and / or enamel previously applied, exposed by sintering the underlying ceramic powders. The presence of such engobes and / or glazes would in fact make the grip of the grouts that are commonly used to seal the joints between two tiles or adjacent ceramic plates, which is much more stable on the powders sintered ceramics. According to the present invention, each upper edge to be chipped, e.g. pio 130 or 135, of the fired ceramic tile or slab 105, can be effectively mind chipped in the following way. In a first phase (see fig.3), the lateral side of the tile is made or fired ceramic plate 105, for example 110 or 115, which defines said edge su- upper, a longitudinal groove 160. By longitudinal groove 160 we mean a channel which, penetrating into the thickness base of the fired ceramic tile or slab 105, extends longitudinally in parallel to the prevailing dimension of the aforementioned lateral flank, for example 110 or 115, basically parallel to the top edge you want to chip, for example 130 or 135. This longitudinal groove 160, which preferably extends throughout the longitudinal extension of the side wall in which it is made, for example 110 or 115, preferably has a width L smaller than the thickness H of the plate strella or fired ceramic slab 105. In this way, the longitudinal groove 160 defines and separates, along said side panel, for example 110 or 115, two protruding longitudinal shelves, of which an upper shelf 165 which defines, together with the visible face 120 of the ceramic tile or slab 105, the top edge to be chipped, for example 130 or 135, and a lower shelf 170 which defines, together with the laying face 125, a lower edge, such as 140 or 145. The thickness H' of the upper shelf 165 is preferably relatively small. colo, for example less than 2 mm. Especially but not exclusively in the case of ceramic tiles or slabs 105 very thick, the longitudinal groove 160 can also be made in so as to be closer to the visible face 120 than to the laying face 125, and so that the thickness H' of the upper shelf 165 is less than the thickness H'' of the lower shelf 170. The longitudinal groove 160 can be made by action / machining mechanics with material removal, for example by means of a rotating tool 200. In particular, the longitudinal groove 160 can be made by means of a relative movement between said rotating tool 200 and the ceramic tile or slab cooked 105 along a predetermined translation direction T parallel to the upper edge higher to chip, for example 130 or 135, such that, during said movement relative, the rotating tool 200 (while rotating) comes into contact with the flank side of the fired ceramic tile or slab 105, for example 110 or 115, which defines the top edge to be chipped. Generally speaking, this relative motion can be achieved either by moving actively the rotating tool 200 (while rotating) relative to the tile or slab ce- ramica 105 which remains stationary, whether actively moving the tile or slab branch 105 with respect to the rotating tool 200 which remains stationary (apart from rotating), both actively moving both of them. The rotary tool 200 may be any tool suitable for making the groove. longitudinal machining 160 by removing material, for example a milling cutter or more preferably a tangential action rotating disc. A tangential acting rotating disc is generally a flat disc, having thickness approximately equal to or less than the width L of the longitudinal groove nal 160 to be realized, which is able to rotate on itself, preferably at high speed, around a rotation axis A perpendicular to the disk itself and passing through its center, and whose perimeter edge is provided with cutting edges and / or abrasive material. This tangential rotating disc can be arranged next to the plate ceramic slab or slab 105. The axis of rotation A of the rotating disk can be oriented perpendicularly to the larger faces of the ceramic tile or slab 105, or slightly in- inclined, with respect to an axis orthogonal to the major faces, for example by an angle less than or equal to 30° sexagesimal, but preferably continuing to lie in a plane perpendicular to the major faces and parallel to the direction of translation tion T (as illustrated in figure 4). Once the longitudinal groove 160 has been made, the chipping process may provide for the application of a force or pressure to the upper shelf 165 F, such as to cause it to break or split. This breaking force or pressure F can be for example directed, at least partially mind, in a direction orthogonal to the major faces of the ceramic tile or slab 105 and preferably in the direction of pushing the upper shelf 165 towards the men- lower only 170. In this way, the breakage of the upper shelf 165 generally occurs in proximity to the bottom of the annular groove 160, but according to a substantially initially random and irregular, achieving the desired edge chipping higher, for example 130 or 135. As illustrated in figure 5, the breaking force or pressure F can be exerted by means of a pressing body 205, for example a skate or a roller, which is placed in contact and pushes the upper shelf 165. In particular, the breaking force or pressure F can be exerted throughout the the longitudinal extension of the upper shelf 165, for example by means of a relative movement between said pressing body 205 and the ceramic tile or slab cooked 105 along a predetermined translation direction T parallel to the upper edge higher to chip, for example 130 or 135, such that, during said movement relative, the pressing body 205 comes into contact with the upper shelf 165 which defines said upper edge to be chipped. Again, relative motion can be achieved either by moving actively presses the pressing body 205 with respect to the ceramic tile or slab 105 which remains still, whether actively moving the ceramic tile or slab 105 with respect to the pressing body 205 which remains stationary, both by actively moving them both. The translation direction T along which the relative movement between the tile occurs or ceramic plate 105 and the pressing body 205 can be the same length where the relative movement between the tile or slab previously occurred branch 105 and the rotary tool 200. It should be noted that, in some forms of implementation, the application phase of the breaking force or pressure F may not be necessary and therefore po- should be omitted, since the mechanical action exerted by the tool rotating 200, to make the longitudinal groove 160, could be of per if sufficient also to cause the contextual and / or contemporary rupture or spac- capture of the upper shelf 165. This effect can be facilitated, for example, by positioning the rotating tool 200 so that the thickness H' of the protruding shelf 165 is very small and / or, in case of using the rotating disk, by tilting the rotation axis as anticipated A with respect to the direction perpendicular to the major faces of the tile or slab ceramics 105. From an operational point of view, chipping can be achieved, for example, through a production line in which the fired ceramic tiles or slabs 105 ven- are advanced in succession along a direction parallel to the edge from chipping, for example by means of a conveyor belt, and in which, during said progress, these fired ceramic tiles or slabs 105 come into contact, one after the other, with the rotating tool 200, for example with the rotating disc at tangential action, which can be appropriately positioned in position fixed, for example next to the conveyor belt. In particular, in the case of square ceramic tiles or slabs 105 which must be chipped on at least two opposing upper edges, for example on en- both the longitudinal upper edges 130 or transverse 135, the production line can be equipped with two of said rotating tools 200, for example with two discs rotating with tangential action, arranged for example on opposite sides of the belt wanter, so as to act simultaneously or in sequence on the two edges to be chipping of ceramic tiles or slabs 105 that advance along the line of production (as essentially illustrated in figure 4). If necessary, the production line can also be equipped with one or more pressing bodies 205, each of which can be suitably positioned in fixed position, for example next to the conveyor belt, downstream of a respective rotating tool with respect to the direction of advancement of the tiles or slabs ceramics 105 (as substantially illustrated in figure 5). In the preferred case where all the upper edges of the ceramic tiles or slabs 105 need to be chipped (as shown in figure 1), you can use a second production line similar to the previous one and an orienting device (commonly called a walker), which is suitable for receiving a ceramic tile or slab mica 105 at a time from the exit of the first production line described above and to re- ski it at the entrance to the second production line, after having oriented it so that the upper edges defined by the lateral sides not yet worked are parallel to the direction of progress of the second production line. Obviously, a technician in the sector will be able to provide further information on all that has been described. rose modifications of a technical application nature, without however departing from the scope of the invention as claimed below.

Claims

1. A method of making ceramic tiles or slabs (100) having irre- grooved or jagged, including the phases of: - prepare a fired ceramic tile or slab (105) having two counter- placed larger faces (120, 125) delimited along the perimeter by one or more lateral sides (110, 115) which define with them respectively one or multiple upper edges (130, 135) and one or more lower edges (140, 145), - chipping by mechanical action at least one of said upper edges (130, 135).

2. A method according to claim 1, wherein the chipping step involves to leave one or more of the lower edges intact (140, 145).

3. A method according to claim 1 or 2, wherein the chipping step It involves creating, along at least one lateral side (110, 115) of the tile or fired ceramic slab (105), a longitudinal groove (160) designed to define and separate two protruding longitudinal shelves, one of which is the upper shelf (165) which includes the upper edge to be chipped (130, 135), and a lower shelf rear (170) which includes a lower edge (140, 145).

4. A method according to claim 3, wherein the longitudinal groove final (160) is made by means of a rotating tool (200), preferably a disk tangential action rotary.

5. A method according to claim 4, wherein the longitudinal groove (160) is achieved by a relative movement between said rotating tool (200) and the fired ceramic tile or slab (105) along a predetermined direction of tra- slation (T) parallel to the upper edge (130, 135) to be chipped, such that, during said relative movement, the rotating tool (200) comes into contact with the lateral side (110, 115) of the fired ceramic tile or slab (105) which defines the upper edge (130, 135) to be chipped 6. A method according to any of claims 3 to 5, wherein step chipping involves applying a force or a pressure (F) capable of causing it to break or split.

7. A method according to claim 6, wherein said force or pressure of rot- tura (F) is directed, at least partially, in a direction orthogonal to the major faces (120, 125) of the fired ceramic tile or slab (105), preferably in the direction to push the upper shelf (165) towards the lower shelf (170).

8. A method according to claim 6 or 7, wherein said force or pressure of breaking (F) is exerted by means of a pressing body (205) which is placed at the con- touch and push the top shelf (165).

9. A method according to claim 8, wherein the breaking force or pressure (F) is exercised along the entire longitudinal extension of the upper shelf (165) by means of a relative movement between said pressing body (205) and the tile or fired ceramic slab (105) along a predetermined translation direction (T) parallel to the upper edge (130, 135) to be chipped, so that, during said relative movement, the pressing body (205) comes into contact and presses the upper shelf (165) which includes the upper edge (130, 135) from splinters jars.

10. A plant for making ceramic tiles or slabs (100) having edges irregular or jagged, including: - means for advancing fired ceramic tiles or slabs (105) along a predetermined direction of advancement, and - at least one tool capable of chipping by mechanical action at least one upper edge (130, 135) of said fired ceramic tiles or slabs (105), while progressing.