PT1321256E - Method and plant for manufacturing ceramic tiles and slabs - Google Patents

Abstract

A method for manufacturing construction elements such as ceramic tiles and slabs, consisting of pressing in one or two stages a mass consisting of at least two ceramic materials generally in powder form at least partially mixed together and having different properties, generally different colours, followed by firing of the pressed product, characterised by comprising the following operative steps: separately preparing bodies of generally irregular form starting from at least one ceramic material generally in powder form having properties different from those of said at least two materials of said mass; adding said bodies to said mass before the final pressing; and subjecting the product to a surface finishing operation before or after said firing step. <IMAGE>

Description

ΕΡ 1 321 256 / EN

DESCRIPTION &quot; Method & Installation for Making Ceramic Tiles & Slabs &quot;

This invention relates to the manufacture of ceramic building materials, generally tiles but also large slabs intended to be used as such or to obtain therefrom one or more smaller elements and / or generally in different forms. The invention also relates to the means for carrying out said method and the materials obtained therewith. The ceramic tiles industry is known to be constantly on the lookout for new and innovative ornamental motifs, with the current emphasis on decorations reproducing the appearance of stone and natural rock, such as marble, which is known to have veined and elongated streaks of various shapes and colors.

Decorative patterns reproducing said aesthetic elements typical of natural stones and rocks such as marble or granite may be obtained by the modern ceramic technology of typical porcelain stone manufacturing, well known to those skilled in the art, which will not be described in detail. It is sufficient to state that these decorative motifs may relate either to the entire mass, that is, to the entire thickness of the tile or slab, or to that layer only on the exposed face of said tile or slab.

In particular, in the second case a double load is performed, the first of which uses a non-particularly valuable base material intended to form the carrier part, while the second uses a finishing material having the properties capable of providing the characteristics the exposed face of the tile or slab. Said second material may consist of at least two ceramic materials in powder form which are at least 2

Partially mixed with each other and have different characteristics, generally different colors. WO-A-9615888 discloses a respective method and apparatus for compacting powders for making compressed ceramic tiles. The method comprises the steps of forming a layer of powders on the conveyor means which convey it to a die, isolating a portion of said layer within a frame of said die, bringing said die closer to said conveyor means, and compacting the portion of said layer isolated by said frame, by means of a punch of said die as it descends inside said frame. The apparatus for carrying out the above method comprises conveyor means for conveying a layer of powders, said die comprising a punch movable in a direction substantially orthogonal to said layer, associated with the respective cross member to cause compression of the powders in a frame movable in a direction substantially orthogonal to said layer independently of said punch, being able to slide in internal contact with said punch, serving as an insulation means for isolating a portion of said layer in said conveyor means.

As noted, natural stones and rocks in general, for example marble, are generally characterized by elongated veins and striae of varying shapes and colors generated by the agglomeration of natural elements of various types which are accumulated and distributed irregularly, or in a manner quite random. The aspect of said natural stones and rocks such as marble is further characterized by inclusions, nodules and masses of varying types which are generally many different at least in terms of color of the base matrix of the respective stone or rock.

As is well known to those skilled in the art, these are often materials deriving for example from the second recrystallization of natural elements such as calcite, limestone aragonite or dolomite.

The dimensions and shape of these inclusions are extremely varied. Usually, they are elongated and in 3

Usually have a generally irregular marginal strip, usually accompanied by a number of shadings, and one or more colorations which are usually considerably different from those of the central part. The main object of this invention is to provide means by which ceramic building materials, generally tiles and slabs can be obtained, having as mentioned above the typical multicolored aspect of natural stones and rocks such as marble, in a particular way in a decoration which in addition to the veins and striae of various shapes and colors also has circumscribed zones of generally irregular shapes having a different appearance from the surrounding general matrix, and possibly surrounded at least in part by a generally irregular width or halo, generally made with at least one least in part from or within the zones.

Essentially the said zones, also called spots, constitute the aforementioned inclusions, nodules or masses typical of natural stones and rocks such as marble.

Said objects are achieved by the features defined in the claims.

In a very general sense, a decorative ceramic product is prepared consisting of preformed congruent bodies acting as inserts for the final product. According to the invention, said bodies are generally of irregular shape and have relatively small dimensions, which means dimensions generally much smaller than those of the tiles and slabs that are intended to be obtained.

Said bodies generally consist of at least one ceramic material generally in the form of suitably compacted powder, which are intended to be added to ceramic materials generally in the form of powder for porcelain-stone type fabrications as explained in the introduction. 4

The at least one ceramic material generally in powder form has different characteristics from said porcelain-type stone material, generally a different color.

According to an advantageous feature of the invention, said bodies of said decorative product may be at least partially covered with at least one ceramic preparation, generally glazed, having different properties, generally a different coloring, of the material or constituents of said articles bodies and the carrier material of the final product, i.e. the tile or the slab.

Such bodies may have discretionary shapes and dimensions.

As regards its shape, it is generally irregular and preferably elongate. The outer surface of said elongated shape is preferably generally smooth, i.e., virtually free of tips or other projections with sharp edges.

With respect to their dimensions, in particular their transverse dimensions, they are generally proportional to the usual thicknesses of the loads deposited in the molds for the formation of the ceramic tiles or slabs. In tests performed with a pilot plant according to the instructions of the invention, elongate shaped bodies having a transverse dimension and a longitudinal dimension averaging 5-15 mm and 10-50 mm, respectively, have proved to be convenient, but these values are to be considered merely as examples.

The tiles, with their backing material incorporating said bodies preferably only within their surface layer, are subjected to a surface finishing operation, generally a smoothing operation, to show their outer face, which may be partially or fully as described, and one or more colors. Said smoothing is preferably effected immediately after forming by the press. Alternatively it can be done after cooking. 5

ΕΡ 1 321 256 / EN

The features and merits of the invention will be apparent from the following detailed description with reference to the figures of the accompanying drawings which show, by way of non-limiting example, a particular preferred embodiment of the upstream part of an installation for carrying out the method proposed. Figure 1 is a side view of the invention. Figure 2 is a plan view of the preceding figure. Figure 3 is the section III-III shown in Figure 2 but on an enlarged scale. Figure 4 is a perspective view of the elements of Figure 3. Figure 5 is the section VV shown in Figure 4. Figure 6 is a section showing part of a charge deposited in the cavity of a mold to form tiles or slabs according to with the invention. Figure 7 is a view totally similar to the previous one, showing the tile or slab compacted in section. Figure 8 shows the same tile after smoothing. Figure 9 is a plan view of the previous figure. Figure 10 is the computerized representation of a marble-like decoration according to the invention.

Said figures, and in particular Figures 1 to 5, show the upstream part of a manufacturing facility for ceramic tiles or tiles, the downstream part, not shown for reasons of simplicity, essentially comprises, in succession: supply for the starting materials, into which the part shown in Figure 1 extends; a forming station, which may be of the single or double pressing type; possibly a smoothing or polishing station; a cooking station, for example of the 6

For the translation of the tiles in one layer or in multiple layers; and a smoothing or polishing station if it has not already been mounted downstream of the forming station.

That portion of the plant shown in Figures 1 to 5 constitutes a production line for forming the generally irregular bodies used as decorative inserts (see Figures 6 to 10) for the finished product, i.e. the ceramic tiles and slabs. Said bodies generally have relatively small dimensions and are preferably elongate in shape, generally in the form of peanuts as shown in said figures.

For example said bodies 1 have a median transverse dimension and an average longitudinal dimension of 5-15 mm and 10-50 mm, respectively.

In Figures 1 and 2 said bodies 1 all have substantially the same shape and the same dimensions for the sake of simplicity. Said production line essentially comprises a compacting station 2, a cutting and finishing station 3, a coating station 4 and a collection and transport system 5.

Specifically, the compacting station 2 comprises a motorized belt 20, for example driven by a built-in speed variator transmission motor, the upstream end of which lies beneath a vertical discharge tube 21. To the discharge mouth of said tube 21 is associated with an adjustable valve member (not shown), preferably controlled by the system controlling the speed of the belt 20.

A series of conduits, of which three are shown, discharges into said pipe 21 and may be activated in a defined order, for example in the case that the process under discussion may be in accordance with a random relation 7

ΕΡ 1 321 256 / EN (variable of choice) integrated into the overall system control system.

Each individual conduit 22 supplies the underlying tube 21 with at least one ceramic material generally in the form of powder which is more or less extensively mixed with the material (s) supplied by the other conduits 22.

In the case, for example, of two materials supplied by the same conduit 22, they will generally have different properties, for example different colors, and may be blended in whole or in part, to respectively produce mixtures of the spotted type or the vein / stretch type type.

For example, the materials provided by the individual conduits 22 may consist of atomized, milled or micronized powders obtained from ceramic, semi-glazed or glazed mixtures, and mixtures thereof.

It should be noted that said generally powder-like materials will have different characteristics, generally different colorations, of the colorations of the powdered ceramic materials provided to form the matrix 100 of the tile body or end slab (see Figure 10) , to form a stone or natural rock type decoration such as marble, shafts and splines of which are indicated by the reference 10 in said figure. The belt 20 is constructed so as to be able to deform elastically for the reasons which will become apparent hereinafter, for example, it may consist of a rubber belt with mixtures of suitable fillers according to their elastic deformation ability and their strength mechanics.

In the center of the outwardly directed portion of the belt 20 is a guide ring 23 in which the belt takes over a relatively short length a tubular shape as a result of folding up its longitudinal edges (Figures 4 and 5) which lie superimposed for a certain distance to said ring 23, where a compaction unit 24 is located.

Essentially, said ring 23 and said unit 24 cause a generally funnel-shaped narrowing (Figures 4 and 5) upstream and downstream of which the outwardly directed portion of the belt 20 substantially takes the form of two channels which gradually respectively (Figures 1 and 2). Said ring 23 is carried by a support 25 which is positioned in the support structure of the belt 20 (Figure 4), the inner surface of said ring 23 being formed as a truncated cone whose minor base is situated downstream and has a circumference smaller than the width of the belt 20 (see Figure 5). Said ring 23 and said support 25 are also equipped with respective cuts for insertion and withdrawal of the belt 20 (Figures 4 and 5). Alternatively, at least the ring 23 may be divided into at least two mutually engaging portions. The compacting unit 24 comprises a circular array of equidistant louvred wheels 240, numbered four in the illustrated example, which are arranged to rotate along the tubular portion of the belt 20 as it leaves the ring 23 (Figures 1-5).

Specifically, two of the wheels 240 are in a horizontal plane, the other two are in a vertical plane which intersects the preceding one along the longitudinal axis of said ring 23, each wheel 240 being continuously forced elastically against the tubular portion of the belt 20 by a respective pressure member schematically referenced 241 in Figures 1 and 2. Said pressure member 241 may consist of a hydraulic or pneumatic cylinder-piston type unit, a helical or spiral flat spring, a spring sheet or the like. 9

ΕΡ 1 321 256 / EN

In the figures, the outer space of the wheels 240 is cylindrical but nothing prevents it from being otherwise configured, for example, with a circumferential groove of arc cross-section.

As a variant, instead of the wheels 240, a circumferential series of sliding skids with an arcuate active surface or equivalent can be mounted.

A mass of loose ceramic material 210 is loaded without discontinuity upstream of the belt 20 and is continuously made consistent by the compacting unit 24, at the outlet from which emerges a cord which divides naturally into pieces 11 (Figures 1 and 2) of shapes and varying dimensions when the two previously superimposed longitudinal edges of the belt 20 are opened.

It should be noted that said strand is compacted with a specific pressure lower than that used to compact the final tile, usually substantially half of the latter.

Said parts are provided to a chute 12 which discharges into the cutting and finishing station 3 between the downstream end of the belt 20 and said chute 12, a nozzle being mounted thereon which collects and removes the agglomerate pieces with dimensions too small. Said belt 20 may also be positioned in conjunction with at least one other totally similar belt to compact a loose starting material having different properties, generally with at least a different coloring of the (or the) of the loose material 210 compacted by the belt 20. In Figure 2, the at least one other belt is shown schematically by a dashed rectangle indicated by 101, and can discharge either in the chute 12 as indicated by the arrow A, or in the collection and transport system as indicated by arrow B. The cutting and finishing machine 3 comprises an inclined roller 30 having a non-horizontal axis which is rotated about itself by a suitable transmission system 31, such as 10

ΕΡ 1 321 256 / PT a gear motor with a built-in speed variator. The interior of said cylinder 30 contains means (not shown for reasons of simplicity) with two functions; one is to split the pieces 11 into smaller bodies 1, having for example the aforementioned shapes and dimensions, the other is to smooth the parts with sharp edges that said bodies 1 have after the fracture of said pieces 11. Said double means action may for example comprise fins of varying shapes and sizes, pins and / or like means.

In combination with said means, or in place thereof, openings with sharp edges can be made in the wall of the cylinder 30. In Figures 1 and 2, said apertures are the same and rhomboidal in shape, but this is indicated by way of example only. Said cylinder 30 discharges to the coating station 4, into which it also discharges, by means of a regulating valve, not shown, a vertical distribution tube 42 of a ceramic preparation consisting of at least one material generally in powder form which has different properties, at least a different coloration, of the starting mass (s) 210. Said preparation may consist of powders or granules of different species, for example chromophore oxides or atomised, ground or micronized powders obtained from mixtures ceramics, semi-glazed or glazed and mixtures thereof. Said coating station 4 comprises an inclined non-horizontal axis cylinder 40 which is rotated about itself by a suitable transmission system 41, such as a gear motor with a built-in speed variator.

Included within said cylinder 40 are means (not shown for reasons of simplicity) to assist the coating of said bodies 1 with said preparation, said means possibly consisting of ribs or projections of various shapes and sizes. 11

ΕΡ 1 321 256 / EN

By regulating the speed of rotation of the cylinder 40 and / or the opening of the discharge valve of the tube 42, both the thickness and the extent of the coating covering the bodies 1 can be selected.

Essentially, the following can be obtained: fully covered bodies (to the left in Figures 6-9, and substantially in the center of the lower third of Figure 10); partially covered bodies (in the center of Figures 6-9 and bottom right of Figure 10); and fully exposed bodies 1 (to the right in Figures 6-9 and the lower left of Figure 10).

The fully-exposed bodies 1 can be obtained either by the temporary closure of the delivery tube 42 while maintaining or not keeping the cylinder 40 in operation, or by bypassing the latter by a suitable offset and directly sending the product exiting from station 3 to the collection and transport system 5.

It should be noted that for certain processes, for example the formation of large ceramic slabs, the cutting and finishing station 3 described above can be bypassed, although excluding or not excluding the coating step.

In the illustrated example said coating takes place substantially dry, but there is nothing to prevent different methods being used. For example, the product leaving the cylinder 30 may be placed in a webbing and subjected to adequately fluidized glaze spray or drip, and then dried before being put into the collection system 5 or placed directly in the collection means. charging station.

As a variant, said webbing can pass either through a cascade sheet or a ceramic glaze bath, from which a suitable fan can be installed.

Nothing prevents a combination of these three techniques from being used. For example, treated bodies 1 after being raised in station 4 may be subjected, for example, to a 12

And subsequent spray or drip coating operation whereby the coating of the bodies 1 will comprise an inner (complete or partial) layer consisting of a first ceramic preparation, such as a glaze, and an outer layer (complete or partial) of a second ceramic preparation, such as a glaze having properties different from those of the prior, typically, a different color.

Again, downstream of the cylinder 30, at least one biasing device arranged, as necessary, may be provided to deflect at least a portion of the bodies arriving 1 towards the location of the coating (glazing) either by spraying, dripping or immersion.

Turning to Figures 1 and 2, it can be seen that bodies 1 (coated or not) upon leaving cylinder 40 are collected by system 5 which comprises two conveyor belts 50 and 51 perpendicular to each other.

Between the cylinder 40 and the upstream belt 50 there is provided a chute 52, between the latter and said belt 50, in case there is an overflow (not shown in the Figures) to collect and re-circulate the excess glaze powder. The bodies 1 obtained in this way are placed in the feed system of the plant forming station and can be used as explained below.

In the case of the single-stage formation, that is, if the generally soft ceramic mass to produce a tile or a slab is to be compacted to the desired degree using a single compression in a single press, said bodies 1 may be: - or previously mixed with said generally soft mass if we use a single loading method; - or previously mixed with a second layer of said mass if using a double charging method; - or deposited directly on the soft mass at the end of its load, irrespective of the loading method used. 13

The above-mentioned is also valid for two-stage forming systems, i.e. the generally soft mass to produce the tile or slab is compacted as desired with two successive pressings in two pressing units . In that case the bodies 1 may also be deposited on the product when it leaves the first pressing unit, i.e. before the second or final pressing. The direct deposit on said soft mass or on said product may be effected by any suitable device, for example a dispensing belt or a hopper with a spreader device.

At the end of the pressing the shaped tile may be subjected to at least one surface finishing operation, generally smoothing or polishing, after which it is cooked.

Alternatively said smoothing or polishing can be carried out on the already cooked product.

As explained, the bodies 1 according to the invention can generally be used for porcelain-type fabrications, in particular for the manufacture of tiles and slabs with natural stone or rock type decorations, such as marble, as shown by way of example of example in Figure 10. This is however not limiting. In this regard, there is nothing to prevent the use of said bodies 1 for slabs and tiles having a much more even or uniform matrix than that of Figure 10, for example, a matrix having a typical granite dotted appearance, obtain with ceramic primers of the spot type.

Lisbon,

Claims (33)

A method for the manufacture of building elements such as tiles and ceramic slabs, consisting in the pressing in one or two phases of a mass consisting of at least two ceramic materials generally in powder form at least partially mixed with one another and having different properties, generally different colors, followed by baking of the pressed product, the following operating steps comprising: - separately preparing the compacted bodies (1) in a generally irregular manner starting from at least one ceramic material generally in the form of powder having properties different from those of said at least two materials of said mass; - adding said compacted bodies (1) to said mass before final pressing; and - subjecting the product to a surface finishing operation before or after said cooking step. A method as claimed in claim 1, characterized in that said compacted bodies are prepared by cutting a pre-compacted accumulation of said at least one material generally in powder form. A method as claimed in claim 2, characterized in that said accumulation is compacted with a specific pressure lower than the pressure of the final formation of said product. A method as claimed in claim 2, characterized in that, during or after said cutting step, said compacted bodies (1) are subjected to a finishing operation in order to substantially eliminate roughnesses such as sharp edges. A method as claimed in claim 2, characterized in that said compacted bodies (1) are subjected to at least one coating operation in order to coat at least a part of their outer surface with at least one layer of at least one And a ceramic preparation having properties different from those of the constituent material of said compacted bodies (1). A method as claimed in claim 5, characterized in that said at least one coating operation is carried out by mixing together an accumulation consisting of a mass of said compacted bodies (1) and a generally powdered mass of said at least one ceramic preparation . A method as claimed in claim 5, wherein said at least one coating operation is effected by spraying said bodies with said at least one suitably fluidized ceramic preparation. A method as claimed in claim 5, characterized in that said at least one coating operation is carried out by exposing said compacted bodies (1) to a dripping distribution of said at least one ceramic preparation in fluid form. A method as claimed in claim 5, characterized in that said at least one coating operation is carried out by passing said bodies through a cascade sheet or a bath of said at least one ceramic material in a substantially liquid form. A method as claimed in claim 5, characterized in that it comprises at least two successive coating operations using ceramic preparations with different characteristics. A method as claimed in claim 1, characterized in that the addition of said bodies to said mass takes place by distributing said compacted bodies (1) through said whole mass. A method as claimed in claim 1, characterized in that the addition of said compacted bodies (1) to said mass takes place by dispensing said compacted bodies (1) into the upper layer of said mass. ΕΡ 1 321 256 / EN 3/6 A method as claimed in claim 1, characterized in that the addition of said compacted bodies (1) to said mass takes place by depositing said compacted bodies (1) on the upper face of said mass. A method as claimed in claim 1, characterized in that the addition of said compacted bodies (1) to said mass is effected before a second pressing step and takes place by depositing said compacted bodies (1) on the upper face of the mass compacted in correspondence with a first phase. A method as claimed in claim 1, characterized in that said finishing operation consists in smoothing. A plant for carrying out the method as claimed in claims 1 to 15, comprising a pressing station in one or two stages with respective means for supplying the ceramic starting materials, and a firing station for the products formed by said station (3, 4) for the finishing of the exposed face of said products, characterized in that said supply means is connected to a line (2, 3, 4) for forming compacted bodies (1) acting as inserts for the products produced by the plant. An installation as claimed in claim 16, characterized in that said production line comprises a displacement belt (20), the outer part of which is arranged to receive a loose mass consisting of at least one ceramic material generally in powder form which has properties different from the properties of said starting materials, generally a different color, and is provided with a compacting system (23, 24) which makes the mass present in said outer part generally consistent. ΕΡ 1 321 256 / EN 4/6 An installation as claimed in claim 17, characterized in that said travel belt (20) is continuously operated by an adjustable motor unit. An installation as claimed in claim 17, characterized in that said displacement belt (20) is elastically deformable. An installation as claimed in claim 19, characterized in that said compacting system comprises an intermediate guide member (23) arranged to cause a portion of said outwardly moving part to assume a tubular shape, and downstream a compacting unit (24) arranged to press against said tubular portion of the belt (20). An installation as claimed in claim 20, characterized in that said guide member (23) comprises an aperture which is traversed by said outer portion and is formed as a truncated cone whose smaller base is facing downstream and has a circumference less slightly less than the width of the belt (20). An installation as claimed in claim 20, characterized in that said compacting unit (24) comprises a circumferential series of contour pressing elements (240) distributed around said tubular portion of the belt (20), against which they are constantly supported by the effect of the elastic thrust means positioned at their rear. An installation as claimed in claim 22, characterized in that said pressure elements (240) each consist of a crazy wheel resting on a plane containing the axis of said frustoconical opening. An installation as claimed in claim 17, characterized in that downstream of said belt there is provided a cutting station for obtaining said compacted bodies (1) from said compacted mass, and for generally smoothing the roughness of the living edges of said compacts bodies. ΕΡ 1 321 256 / EN 5/6 An installation as claimed in claim 24, characterized in that said cut-off station (3) comprises an inclined rotary cylinder (30), on the inner surface of which means such as pins and / or ribs of various shapes and dimensions are provided. An installation as claimed in claim 25, characterized in that at least a portion of the wall of said cylinder is provided with vents with sharp edges. An installation as claimed in claim 17, characterized in that said downstream or said belt (20) or said cutting station (3) is provided with at least one station (4) for at least partially coating said bodies with a layer of at least one ceramic preparation having properties different from those of the at least one material constituting said compacted bodies (1). An installation as claimed in claim 27, characterized in that said at least one coating station (4) comprises an inclined rotary cylinder (40) within which said compacted bodies (1) pass and a distributor (42) for the said at least one ceramic preparation, the latter generally in powder form. An installation as claimed in claim 28, characterized in that the inner surface of said cylinder (40) has mixing means such as projections or ribs. An installation as claimed in claim 27, characterized in that said at least one coating station (4) comprises support and conveying means for said bodies, with which at least one spray unit for said one less a ceramic preparation. An installation as claimed in claim 27, characterized in that said at least one coating unit (40) comprises support and conveying means for said bodies, with which at least one drip apparatus is associated with said dough less a ceramic preparation. ΕΡ 1 321 256 / EN 6/6 An installation as claimed in claim 27, characterized in that said at least one coating unit (4) comprises support and conveying means for said bodies passing through at least one cascade sheet or a bath of said one less a ceramic preparation. An installation as claimed in claim 16, characterized in that said finishing apparatus comprises at least one smoothing or polishing machine. Lisbon,