EP0738215A1

EP0738215A1 - Silk-screen process for decorating items and associated apparatus

Info

Publication number: EP0738215A1
Application number: EP95904530A
Authority: EP
Inventors: Carlo Antonio Camorani; Maris Algeri
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-12-24
Filing date: 1994-12-23
Publication date: 1996-10-23
Also published as: WO1995018020A2; AU1317895A; WO1995018020A3

Abstract

Items are decorated using a silk-screen process with liquid glaze whereby the items (9) are positioned at a distance (A) from a matrix (2), through which the decorating fluid is forced, so that contact between said items and said matrix is avoided. The decorating fluid is selectively associated with the said matrix and subjected to transferring means (7) for transferring the fluid to the items. Said transferring means being capable of subjecting the decorating fluid to dynamic forces greater than the force due to gravity. The decorating fluid is projected onto the said items by virtue of the said dynamic forces.

Description

SILK SCREEN PROCESS FOR DECORATING ITEMS AND ASSOCIATED APPARATUS

The invention concerns a method for decorating flat items substantially using a silk screen process and the relative machine and products, that is, a new procedure for decorating items with liquid or powdered glaze, for example, ceramic tiles, ceramic dishes, or bottles: the machine and the products suitable for the implementation of the method also being part of the subject matter of the patent application. The prior art involves decorating procedures using wet process, dry process and transfer printing process. The most common wet process decoration procedures are: a)silk-screen process using a flat screen and with squeegees driven in alternating motion, by means of crank and connecting rod, or in general with programmed stop devices; b)rotating silk-screen process, using a cylindrical screen, also in sectors; c)rolling using elastic matrix, for example cut by laser; The procedures for dry process decoration are: d)with powdered glaze e)forcing the powder through a flat screen using a squeegee; f)dropping the powder from a vibrating sieve onto the flat element to be decorated, through a stencil; Transfer printing: g)transfer of the decoration from its paper based support to the surface that is to be decorated by wet or heat transfer. These procedures, however and the relative machines and products have the following principal drawbacks: with respect to procedures a), e): the need to bring the elements being decorated to a standstill; with respect to procedures a), b), c): the need, in the wet process, for treatment or drying time, with large overall dimensions or time wasting; with respect to procedures a), b), c): the possibility of the screen becoming clogged and breaking the tile by means of the squeegee's pressure with consequent need to stop the machine; with respect to a), b), c): the possibility of denting or breaking the tiles in their raw state due to the compression transmitted by the squeegees through the screen in contact with the tiles; with respect to a), b), c): the possibility of variations in the tone of the colours due to the contact between the screen and the tile and the subsequent non-uniform separation of the screen from the tile; with respect to a), b), c): the need for the use of additives or means for making the glazes suitable for the silk screen process; with respect to a), b), c): the need for substituting the screen or the roller when varying the quantity of glaze; with respect to a), b), c): the impossibility of extending the decoration to the edge of the tile and on surfaces that are undulated, or not flat in general, without avoiding smudging; with respect to a), b), c): the need for the continuous presence of the operator for cleaning and controlling operations; with respect to d): low productivity, low definition and limitations in the designs; the need to substitute the stencils; with respect to e): the difficulty in chosing the powder, low definition and difficulty in controlling the quantities; with respect to f): high costs; unsuitable for the requirements of normal tile production.

A further drawback involved in the prior art consists in that syncronisation of the tiles in a conveyor line with an active member of an operative machine is difficult to achieve.

The state of the art includes conveyor lines in ceramic tile production plants consisting of horizontal motorized roller conveyors, longitudinal closed loop belts driven by motorized pulleys, conveyor belts, or other systems.

When, for example, the top face of the tile needs to be decorated with the application of ceramic paints, in powder or liquid form, devices have to be used that synchronise the tiles with the decorating machine, the said devices consisting of longitudinal closed loop belts in vertical planes, wound on pairs of toothed pinions, one of which is motorized, that have transverse elements to push the tiles along, for example into the silk screen printing station, so that they are in phase with the start of the decorating cycle.

Alternatively, pairs of lateral closed loop belts have been used that act on the sides of the ceramic elements in order to advance them and to stop them under the screen in the silk screen printing station with subsequent activation of the spatulas.

Moreover, the devices with conveyor chains having transverse pushing elements, as well as possibly damaging the tiles when the said elements bang against their sides, require the chains to be changed every time the format of the tiles is varied, with consequent time wasting and increase in costs.

Furthermore, as regards the devices with pairs of lateral belts, it is to be noted that, whilst these are advantageous when used with tiles that have a longitudinal dimension close to the optimal one of the design, there is an unacceptable drop in productivity when smaller formats are used.

Furthermore, with the smaller formats there is considerable increase in the speeds required in positioning the tile in the silk screen printing station, with consequently the possibility of skidding and a reduction in the accuracy of positioning.

Also, the lateral belts acts simultaneously on a tile entering the silk screen printing station, to convey it to the printing position, and on a tile in the silk screen printing station, to expel it at the end of the cycle: in this way at least two tiles are mutually constrained in their movements to and from the processing station, with the possibility of idle time when the tiles have longitudinal dimensions that are shorter than the design length for the machine.

Finally, the use synchronising devices with pairs of lateral belts entails stopping the tile in the decorating station, so preventing their use in continuous decorating machines, for example in silk screen printing with cylindrical screen, or rotary printing.

Such prior art may be subject to considerable improvements with a view to eliminating the above-mentioned drawbacks.

From the foregoing emerges the need to resolve the technical problem of inventing a method that enables contact to be avoided between the screen and the moving surface to be decorated; a further aspect of the technical problem is to invent a method according to which the contact between the device forcing the glaze through the screen and the screen is avoided; said methd being suitable for the implementation both when using liquid, or damp, glaze and powdered glaze: this in order to avoid, or at least reduce, the defects resulting from the contact between the matrix and the product, particularly in the case of damp or liquid glaze.

The machine for implementing the method according to the present invention should be simple and with reduced operating costs and should not require the matrix to be cleaned or washed. The decoration of the product having to extend, if required, to the non flat edges of the item, for example, of ceramic tiles, to possible indentations of the corresponding surfaces and also over curved surfaces such as, for example, the surfaces of bottles and, where necessary, also to non flat surfaces in general. According to another aspect of the present invention, the need emerges to invent a a method, that can be implemented in a relative plant, for synchronising ceramic tiles with a high degree of flexibility, that is, a method and a machine that can be used in numerous applications, both with continuous and intermittent processes; it being necessary to achieve an substantially constant level of productivity even with variations in the longitudinal format of the tiles. In the context of the present invention the expression "decorating fluid" includes any kind of decorating substance, for example a glaze, in liquid, or powdered form.

The invention resolves the said technical problem by adopting a method for decorating an item with a decorating fluid wherein said decorating fluid is selectively associated to a matrix, or reticular conditioning element, and exposed to transferring means for transferring the decorating fluid to the item to be decorated. According to a preferred embodiment, said transferring means comprises injecting means, e.g. a nozzle, for selectively projecting the decorating fluid, in form of small particles, against the item to be decorated through said matrix.

According to another preferred embodiment, the transferring means comprises injecting means for projecting an operating fluid, particularly pressurized air, against said matrix having cavities containing said decorating fluid, so that said decorating fluid is projected against said item to be decorated. According to another preferred embodiment, said transferring means comprises vibrating means cooperating with said matrix for detaching said decorating fluid from cavities of the matrix into which the decorating fluid is contained and preject said decorating fluid against the item to be decorated.

It is to be understood that the method may also envisage incorporating, in the cavities of a matrix, the damp, liquid or powdered glaze: in this last case the cavities possibly being treated with an adhesive substance, but in such a way that the glaze may be immediately expelled onto the surface to be decorated which is not in contact with the matrix itself and which has, advantageously, synchronous motion when sharpness is required in the decoration. The lack of synchronization, furthermore, enabling shading effects to be obtained; the expulsion of the glaze in the matrix can be achieved by projecting through the matrix, if it is of the screen type, a jet of compressed air or, in general, by means of vibrations, advantageously ultrasonic; also in the case of the use, instead of the screen, of a belt with its external surface facing the item to be decorated having cavities, be they open or closed, which take a load of powdered glaze, or possibly damp glaze, the expulsion of the glaze can be effected by means of vibrations.

The surface to be decorated can also be pretreated with an adhesive substance.

According to a preferred embodiment, said matirx being located at a predetermined fixed distance from said item and said transferring means being able to transfer dynamic forces to particles of said decorating fluid.

According to another preferred embodiment, the decorating fluid, particularly a liquid glaze atomized without air, is projected, at a distance from the reticular conditioning element positioned between the transferring means, and the surface to be decorated: the reticular conditioning element and the surface to be decorated moving at generally the same speed and never coming into contact with each other.

EXAMPLE 1 -finely ground glaze suspended in water, that is, without residue on a filter screen with a 0,06 mm mesh; -glaze density of approximately 1600 g/l (possibly between even less than 1200 and even more than 2200); -high pressure atomization, without compressed air;

-nozzle for a vane jet having a cross-section of approximately 1 ,5 mm²; -input pressure of the glaze without air of 25 bar, with the possibility of it being less than 10 bar and more than 40 bar; -distance from nozzle to screen of 300 mm, with the possibility of it being less than 250 mm and more than 400 mm; -advancement speed of the tiles of 25 m/min. with the possibility of it reaching and exceeding 60 m/min; -screen with 15 strands/cm; -distance from screen to tile of 3-4 mm.

The invention furthermore includes a decorating machine for decorating an item with a decorating fluid, comprising an item positioned at a distance from a decorating matrix, wherein associating means are provided for associating a decorating fluid to a matrix, and transferring means are provided for transferring said decorating fluid to said item by means of a dynamic effect.

It is to be noted that said transferring means are capable of exerting a dynamic effect on said decorating fluid in a direction substantially independent to the direction of the gravity.

Said matrix may comprise a silk-screen having peripheral motion, from inside which the atomized glaze is projected, by means of an atomizing element without air, in a transverse vane, through the screen and on to the elements to be decorated, which are in continuous motion generally synchronised with the screen.

The advantages offered by the above embodiments of the invention are: the elimination, in the case of wet or damp glaze, of the contact between the screen and the surfaces to be decorated and therefore of all the associated drawbacks; greater definition in the decoration or improved shading as required; more precise control over the doses; possibility of decorating surfaces which are not perfectly flat and surfaces which are curved, inclined, vertical; absence of cleaning and washing; lower costs. According to another preferred embodiment, the machine comprises a According to another preferred embodiment, the machine comprises a screen having continuous peripheral motion, with the expulsion of the damp or liquid glaze from the mesh of the part of the screen with the motif: this by means of a jet of compressed air crossing the said mesh, or by means of vibration of the said portion of screen facing the underlying items to be decorated.

Alternatively, said matrix can consist of a belt with continuous motion having incisions on its external surface facing the item to be decorated, and with these incisions, open or closed, prefilled with powdered or damp glaze, the expulsion being obtained by vibrating the corresponding section of belt.

As regards the product, it is free of the defects associated with the traditional contact between the surface and the corresponding matrix, as well as being printed also in the areas which are indented or not flat, or curved.

EXAMPLE 2 (cylindrical screen, damp glaze, expulsion by compressed air)

- Matrix of the rotating cylindrical screen type, with one or more sectors; peripheral velocity 25 m/min, possible or convenient from 15 to 40 or more m/min;

- damp or powdered glaze inserted by pressure in the mesh of the screen using one or more squeegees;

- expulsion of the glaze from the mesh of the screen using compressed air nozzle having an opening of 0,1 mm;

- compressed air pressure 4 bar, much lower or much higher values are possible;

- distance opening-screen: 2 mm, though possibly from zero up to even 3-4 mm, or more;

- distance screen-tile: from 3 to 6 mm, tending towards zero - for example down to 0,1 mm - for maximum sharpness.

EXAMPLE 3 (band moving horizontally, vertically, or inclined, damp glaze, or even powdered, expulsion by vibration)

- Matrix of the moving band type, with one or more sectors, horizontal, inclined or vertical; peripheral velocity 25 m/min, possible or convenient from 15 to 40 or more m/min; - Damp, liquid or even powdered glaze; insertion in the mesh of the screen by means of, respectively, squeegees, or by means pump and squeegees;

- expulsion of the glaze from the mesh of the screen by ultrasound vibrations, with a frequency of approximately 20.000 Hz and amplitude of approximately 0,08 mm;

- distance of the section of band made to vibrate from the surface to be decorated from even less than 1 mm up to 20 mm or more, with loss of sharpness and shading achieved as the distance increases.

EXAMPLE 4 (band with incisions facing outward with cavities and/or surfaces to be decorated possibly made adhesive, powdered glaze, expulsion by vibration).

- Matrix of the band type with incisions facing outward, having one or more sectors with incisions, horizontal, vertical or inclined; velocity of the band 25 m/min, possible or convenient from 15 up to 40 m/min or more;

- powdered glaze; insertion in the . cavities of the screen from the outside by means of a squeegee; cavity possibly made adhesive;

- expulsion of the glaze from the cavities of the band by ultrasound vibrations, with a frequency of approximately 20.000 Hz and amplitude of approximately 0,08 mm;

- distance of the section of band made to vibrate from the surface of the surface to be decorated - possibly made adhesive - from 3 to 6 mm, tending towards zero, for example down to 0,1 mm, for maximum sharpness.

In the tests relating to examples 2, 3, 4, the following were used:

- damp glaze consisting of a powder suspended in polyglycol, having a density of 2000 g/l and a viscosity to prevent flow when the spoon containing the glaze is levelled and turned up side down;

- powdered glaze: impalpable and low flow;

- cylindrical or band screen, for example in polyester cloth, with motif than can be applied by photographic emulsion;cloth with 32 strands/cm, with mesh openings of 0,19 mm; alternatively, cloth with 54 strands/cm, with mesh opening of 0,10 mm; it is also possible to use cloths having less than 10 strands/cm and even up 80 or more strands/cm; - band in polyethylene with incisions achieved by mechanical removal with depths of 0,1 - 0,4 mm, up to even 1 or more mm. The advantages offered by the above embodiments of the invention are: the elimination, in the case of liquid glaze, of the contact between the screen and the item to be decorated and therefore of all the associated drawbacks; higher definition of the design or improved shading depending on requirements, a more precise control over the doses and the possibility, in the dry decoration process, of making use of normally used glazes; possibility also of decorating surfaces that are not flat; lower costs.

The invention also includes a method for synchronising ceramic tiles on a conveyor line moving towards a decorating machine equipped with a decorator element, the method involving the control of the position of each tile along the conveyor line, the measurement of the delay of each tile that arrives with respect to the decorator element of the said decorating machine, the transmission of a signal proportional to the delay to a control unit that is able to temporarily vary the velocity of a plurality of synchronising elements of the said tile along the conveyor line, the temporary variation of the velocity of the said synchronising elements so as to advance the tile into a position of synchronisation with the said decorating element; the position of synchronisation can be reached either with the tile stopped or while it is moving along the conveyor line.

The invention also concerns a syncronizing machine including a conveyor line for ceramic products moving towards a decorating station on the said conveyor line, the products being made to cooperate with a synchronising device positioned on the said conveyor line upstream of the said processing station; the said synchronising device consisting of a number of pairs of aligned rollers, or belts, that act on at least a part of a predetermined zone of the tile.

This, especially with the use of the pairs of rollers, enables the particular advantage of being able to act on each tile individually in order to position each of them, or set them in phase with the processing station, depending on its particular operating requirements. Each tile, furthermore, in interacting with only a part of the rollers that make up the synchronising device, can be independently checked and controlled as regards its position and/or speed in relation to the preceding and/or following tile.

It is to be noted that the use of the pairs of belts, especially in association with rotary decorator elements, is particularly suited to the decoration of moving tiles, that is without stopping them in the decorating position, for example, in silk screen printing with cylindrical screen, or contact printing.

In a particularly advantageous version, the said rollers have axes that are perpendicular to a plane that passes through the top face of the tile, the said rollers being arranged in opposing rows each side of the tile conveyor in such a way that they act on the sides of each tile.

This enables the handling of tiles whose top face is inaccessible, for example, because it is covered with liquid paint.

Alternatively, the said synchronising device consists of a motorized roller conveyor defining an substantially horizontal transit plane, in which, between adjacent rollers, there are aspirator devices that maintain the contact, by suction, between the said rollers and the ceramic products being conveyed.

This enables a maximum flexibility of application of the machine according to the invention for the most varied types of machinery, as no mechanical adjustments are required as a result of variations in the format of the tiles.

In a particularly advantageous version the rollers of the synchronising device according to the invention, in its various versions, are driven independently, or in groups.

The synchronising devices according to the above-mentioned embodiments may be used in conjunction with any kind of operatting machine for the manufature of flat items, particularly ceramic tiles.

Some embodiments of the invention are illustrated, purely by way of example, in the ten tables of drawings attached, in which: Figure 1 is an interrupted schematic axial view of a machine with a silk screen drum - for example with a surface made up of four separated screens or reticular elements - with internal atomization of liquid glaze, in the case where the said glaze is projected square through the screen, for the silk screen decoration of flat objects; Figure 2 is the schematic axial axial view of a machine having a belt made up of one or more screens or reticular elements in succession, wound in a closed loop, with internal atomization of the liquid glaze and projection according to the present invention; Figure 3 is a partial plan view of Figure 1 ; Figure 4 is a partial plan view of Figure 2: Figure 5 is an interrupted schematic axial view of a machine with a matrix consisting of a cylindrical reticular conditioning element, or rotating screen - for example having a surface formed by four spaced serigraphy screens - with internal feed of liquid, damp or powdered glaze for the silk screen printing of substantially flat objects by means of a jet of compressed air; Figure 6 is the schematic axial elevation of a machine having a serigraphy band consisting of one or more screens in succession, wound in a closed loop, with internal feed of liquid, damp or powdered glaze according to the invention; Figure 7 is the interrupted plan view of Figure 5; Figure 8 is the interrupted plan view of Figure 6; Figure 9 is the schematic axial view of a section of flexible band of a machine for the continuous decoration of flat items, having glaze loaded into cavities, or recesses, made in the external surface of the band itself constituting the matrix of the decorating motif with subsequent release of the powder on the item to be decorated by means of vibrations; Figure 10 is a partial plan view of Figure 9; Figure 11 is a schematic plan view of a machine having a serigraphy band consisting of one or more screens in succession, to project, by vibration, the motif, or pattern, of the screen on cylindrical items, such as bottles positioned vertically; Figure 12 is the elevation of Figure 11 ; Figure 13 is a schematic side view of a machine according to the invention, having synchronising device with formations of lateral rollers in association with a rotary printing machine for ceramic tiles; Figure 14 is the top view of Figure 1 ; Figure 15 is a view as in Figure 14, but interrupted and relating to a machine according to the invention in the version with a horizontal roller conveyor; Figure 16 is section XVI-XVI of Figure 15; Figure 17 is a view as in Figure 14 but relating to a version of the machine according to the invention, in association with silk screen printing machine with a flat screen, during the printing phase; Figures 18, 19 are views as in Figure 17, but in succeeding positioning phases showing succeeding rollers with variable peripheral velocities in a longitudinal direction parallel to the conveyor line, in longitudinal direction parallel to the conveyor line, in function of the progressive positioning of the products; Figure 20 is a side view as in Figure 13, but relating to a synchronising machine according to the invention in association with a continuous silk screen printing machine with cylindrical screen; Figures 21 , 22, 23 are schematic plan views of a machine for setting the phase of the ceramic tiles by means of pairs of lateral belts in association with a decorating machine having a rotary decorating element, respectively in the phases of activation of the position sensor, and the following entry and decoration phases of the tile.

The Figures show: 1 , a rotor made up of a cylindrical reticular conditioning element, or rotating screen 2, for example formed by sectors of screen separated by means of traverses 3, closed at the base by a disc 4, at the front having a rim 5 and driven by shaft 5a; 6, the supply tube for a glaze atomizing nozzle 7, for example, as in a vane jet 8 advantageously transverse with respect to the direction in which the flat elements 9 are conveyed by line 10 synchronized with the rotating drum, or even at a different speed where necessary; 11 , 12, two excess glaze scrapers; 13, a water and/or cleaning solvent sprayer for the reticular element, followed by an air jet dispenser 14 to dry it; 15, a collecting trough and screen advantageously having an aspirator to discharge the liquid; 16, (Figure 2) a continuous silk screen printing belt wound on rollers 17, at least one of which is motorized: said belt having at least one section that is parallel and immediately above the items 9 to be decorated; 18, an aspirator for excess glaze on the silk screen printing belt; 19, a sensor for synchronized operation, in the case of the belt-like reticular element consisting of sectors; 20, (Figure 3) the support for shaft 5a; 21 , 22, some ornamental designs of the screens, that permit the passage of the atomized liquid glaze; 21a, 22a the images formed on the tiles 9; A, the distance between the rotating screen 2 and the surface to be decorated 9, for example, even less than 1 mm - in any case as much as is required to avoid the disadvantage of contact - and up to 10 or more millimetres, in order to achieve, with increasing distance, accentuated shading effects, depending also on the parameters used. It is to be noted that a variation of the distance A allows corresponding variations of the decorating effects, namely: increasing the distance A produces decorations having shaded contours, while reducing said distance produces a defined outline of the decoration. Furthermore, a difference in speed between the matrix and the conveyor line of the tiles to be decorated generates shadings in the direction of movement of the tiles, or items to be decorated. Variations of distance A as well as said difference in speed may be carried out also in progress and automatically, i. e. when the machine is decorating the items, so that tiles having different decorating patterns, having a common matrix, may be obtained. Moreover, the distance between the nozzle 7 and the screen 2 can vary as required.

The Figures also show: 31 a rotor consisting a cylindrical reticular conditioning element 32, for example formed by sectors of screen separated by traverses 33, closed at one end by disc 34, having on its front a rim 35 and driven by shaft 35a; 36, a compressed air supply tube with nozzle 37 having a narrow opening that projects air 37a against the screen 32 to expel, with the action of the air itself, the glaze 38 inserted in the mesh by means of pressure applied by internal squeegee 39 and external squeegee 40 on the body of glaze 41 however brought between one of the squeegees and the screen; the substantially flat items, for example ceramic tiles, transported on line 42a, on which the decorative motifs 43 are printed (Figure 7); the same decorative motif of the mesh 32 filled with damp or liquid glaze 41 compressed by squeegees 39, 40; 45, the image of the same decorative motif left in the mesh 32 after the expulsion of the glaze contained in it by the jet of compressed air 37a; D1 , the distance from the opening in the nozzle 37 from the screen 32 at its lower area facing the surface to be decorated; D2, the distance between the screen 32 and the surface 42 to be decorated; 46, (Figure 6) a serigraphy band wound on rollers 47 with horizontal axis, at least one of which is motorized; 48, two lower side, internal runners for the band 46 with shaped sliding contact surfaces that delimit the narrowed horizontal zone A1 parallel to the surface 42 to be decorated, subjected to vibration to transfer the glaze, possibly also in powdered form 49, from the decorative motif 50 imprinted on screen 46, by means of flow 51 obtained by the action of vibrator 52, consisting of motor 53 with lower actuator element 54 in contact with screen 46 in zone A1 ; D3 the distance between the part of the screen included in zone A1 and the surface 42 to be decorated; 55, sensors for synchronizing the motion of the screen 46 with the tiles 42, in association with holes 46a on the edge of the screen 46; 56, (Figure 9) a band of flexible material, for example thermoplastic or rubber, whose external surface has cavities 57 forming the decorative motif to be printed onto the flat items 42 to be decorated: these cavities being filled with a very fine powder glaze 58, compressed against the said external surface by means of external squeegee 59 after possible treatment with an adhesive substance; B, a horizontal zone of the flexible band 56, included between two guiding rollers 60, on which the lower element 61 of vibrator 62 acts; 63, the flow of powder falling from the cavities 57 made to vibrate by the actuator element 61 in contact with the internal surface of flexible band 56 in zone B; 64, the areas of the tiles 42 parallel to zone B, imprinted by the glaze falling from the cavities 57; 65, areas of the external surface of the flexible band 56 without cavities; 66 (Figure 11) a serigraphy band wound on rollers 67 with vertical axes, at least one of which is motorized; 68, two internal shaped runners under which slides band 66, delimiting a narrowed horizontal zone V subjected to vibration from the inside by motorized vibrator 69, whose actuator element 70 is in contact with zone V; 71 , a vertical axis cylindrical element, for example a bottle, that is struck radially by the flow 72 of glaze - in liquid or powder form - inserted in the mesh of the decorative motif 73 of the serigraphy band 66 by compression with squeegees 74, 75, with contact line advantageously inclined to the vertical, of the body of glaze 76 in whichever way brought there; 77, a collecting tank for excess glaze 77a; 78, a pump to feed the glaze to the said band, through tubes 79, 80 from the said tank; 81 , (Figure 12) the decorative motif transferred to the cylindrical element 71 ; 82, the decorative motif of screen 66, emptied of glaze.

It is to be noted that vibrators 53, 62, 69 could also be split, that is, they could have more than one actuator element in contact with the screen or band constituting the matrix. Furthermore, the squeegees for enclosing the glaze in the mesh of the reticular elements or in the cavities of the band could be substituted with elastic rollers.

Figure 13 shows a positioning machine 101 for ceramic tiles 102 on conveyor line 103, for example consisting of a pair of closed loop belts that support the tiles themselves, upstream of a decorating machine

104, for example for the continuous rotary printing of tiles 102, having printing drum 105 with activating elements 106 distributed over a constant distance L1 that activate sensor S1 indicating the angular position of the drum 105 around its axis of rotation Z (Figure 14).

Drum 105 has at least one sector with a decorating design, in relief, or in intaglio, that is to be transferred to the tile 102 during printing.

The distance L1 between the activating elements 106 has to correspond to the distance between the tiles 102 entering the decorating machine 104.

The machine 101 has a number of rollers 107 with vertical axes, that is, perpendicular to the plane in which the tiles 102 are conveyed, made to rotate by corresponding motorized devices 108, in such a way as to accelerate the tiles 102 transiting on conveyor 103 from a speed

V1 to a synchronisation speed V2: the speed of rollers 107 can be adjusted in a controlled manner along the conveyor line 103.

The external surface of the rollers 107 is advantageously coated in a material that has a high resistance to wear and a high coefficient of friction with the part, or parts, of the tiles 102 that come into contact with them.

In the stretch between the last roller 107 and the decorating machine

104, tiles 102 are abandoned on the conveyor line at speed V1 of the conveyor but in a position where they are synchronised with the decorating pattern on the printing drum 105.

Machine 101 has a position sensor for the tiles 102 on conveyor 103, for example a photoelectric cell FC1 , that informs a control unit, not shown, for example a PLC (Programmable Logical Computer), of the delay of the arriving tile: to this end sensor FC1 has to be positioned so that tile 102 that is arriving is held between at least one pair of rollers

107 when its position is measured.

Evaluating the delay of the arriving tile with respect to printing drum

105 having a uniform rotation around axis Z, the pair of following rollers are programmed with increasing speeds so that the tile 102 reaches a more advanced position P1 with respect to position P that tile 102 would have reached if it had been left undisturbed on the conveyor line, with a difference SC that guarantees the moving synchronisation with the printing drum 105.

Figures 15, 16 show how the device for setting the phase of the tiles

102 can consist of rollers 109 having horizontal axes, possibly made to operate in conjunction with aspirator devices 110 to improve the adherence of the tiles transiting on the rollers themselves.

The aspirator devices have suction manifolds 111 inserted between each roller 109 and the next and have a top edge that is advantageously at a very short distance from the transit plane PS of the tiles 102 so as to improve the suction effect.

The rollers 109 advantageously have a central portion 109a with a reduced diameter so as to favour contact with the tile only along lateral strips.

The end portions of the rollers 109 can be directly in contact with the tiles 102.

Alternatively, in order to enable the air to be aspirated and to improve the control over the position of the tiles along the conveyor line, rollers

109 can have splined extremities which drive corresponding toothed belts 109b.

Note also that the motorized devices 108 can consist of stepper motors, direct current motors with encoder or asynchronous motors with encoder driven by an inverter, depending on the application requirements.

As shown in Figure 17, the pair of rollers 107, after having brought about the synchronisation of the tiles 102 and the conveyor line 103, can even bring each tile to a halt in the silk screen printing position under the screen 112, particularly in a silk screen printing machine with a flat screen: the rollers corresponding to the silk screen printing station have to be stopped throughout the entire duration of the printing cycle and subsequently reactivated to expel the decorated tile, in this case at an expulsion velocity V2 corresponding to the synchronisation velocity of the following tile, as illustrated in Figures 18, 19.

Figure 20 shows the rollers 107 that can be used also in association with a silk screen printing machine 113 having a cylindrical screen 114 and relative spatula 115, possibly made mobile in a vertical direction to avoid interference with longitudinal stiffening elements 116 of the screen located correspondingly with the generating lines of the screen itself.

The longitudinal elements 116 can advantageously function as exciters for the sensor S1 , it being possible, alternatively, to provide appropriate exciter elements 117 fixed to the said elements in an axial external position with respect to the silk screen printing area, in such a way that they do not interfere with the spatula and screen during the printing phase.

As the screen 114 can not be made to rotate, idling, with uniform motion around its axis Z1 of rotation, as is the case with the rotary printing drum, there has to be a device for generating periodical impulses, for example in the form of electrical signals, as produced by the PLC control unit, to evaluate, by means of position sensor FC1 , if the tile that is arriving is delayed with respect to the periodical signal and consequently accelerating it to achieve its synchronisation with respect to the screen.

The operating logic, used in the PLC, can be expressed as specified hereafter:

- after the passage of a tile under the sensor FC1 , the PLC activates the screen 114, precedingly at standstill, so as to obtain the decoration of the first tile;

- if, within a predetermined amount of time, for example equal to double the duration of a silk screen printing cycle, the passage of another tile is not signalled, the cylindrical screen is stopped again in a ready position until the arrival of the next tile, otherwise the uniform rotational motion around axis B of the screen is maintained and the transiting tile, sensed by FC1 , is accelerated by rollers 107 so that it arrives beneath the screen in a synchronised position. Consequently, with a low rate of arrival of tiles, the screen is controlled with stepped activation and the tiles progress on the conveyor at a constant speed, whereas, with a high rate of arrival the screen is activated with a uniform rotational motion around axis B and the tiles are accelerated by rollers 107 in order to achieve the condition of synchronisation beneath the screen 114.

Figures 21 , 22, 23, show how the said synchronising elements can consist of a number of pairs of belts 118, consecutive, aligned at the sides of the conveyor line 103 of the tiles 102, one of the pairs of belts

118, for example, being made to operate in conjunction with a printing drum 105, or other rotary decorating element, for example a cylindrical serigraphy screen.

The belts 118 are each wound in a closed loop on a pair of pulleys 119, one of which is motorized, positioned at the sides of the conveyor line

103.

The distance L3 covered by the tiles 102 in which the synchronisation of the rotary decorator element 105 with the tile 102 having variable velocity V3 has to take place, is included between an entry position of the tile gripped between belts 118 and an exit position with the tile still held by the belts but not yet introduced between the next pair of belts

1 18.

In practice, the materials, dimensions and details of execution or secondary details may be different from but technically equivalent to those described without departing from the juridical domain of the present invention.

Claims

1. A method for decorating an item with a decorating fluid, wherein said item is positioned at a distance from a matrix through which the decorating fluid is forced, so that contact between said item and said matrix is avoided, and said decorating fluid is selectively associated to said matrix and subjected to transferring means for transferring the decorating fluid to the item to be decorated; said transferring means being capable of subjecting said decorating fluid to dynamic forces substantially greater than the gravity forces, so that the decorating fluid is projected onto said item by virtue of said dynamic forces.

2. A method according to claim 1 , wherein a wet silk screen process is adopted which includes the passage of decorating fluid through openings provided for in said matrix.

3. A method according to claim 1 and 2, wherein said transferring means spray the decorating fluid under pressure through said openings onto the surface to be decorated, without contact between the said element and the said surface.

4. A method according to claim 1 and 2, wherein said decorating fluid is ejected from the said openings onto the surface to be decorated by said transferring means comprising a jet of pressurized gas coming from inside the said matrix.

5. A method according to claim 1 , wherein said decorating fluid is firstly incorporated in cavities provided for in said matrix.

6. A method according to claim 5, wherein said decorating fluid is ejected from the said cavities by said transferring means against the surface to be decorated, without contact between the said matrix and the said surface.

7. A method according to claim 2, or 6, wherein said transferring means comprises vibrating means, generating high frequency, low amplitude vibrations imparted to the matrix in the area where it faces the surface to be decorated.

8. A method, according to any preceding claim, wherein during the transfer of the decorating fluid the matrix and the surface to be decorated are in motion.

9. A method, according to any preceding claims, wherein the matrix and the surface to be decorated with the decorating fluid are synchronized.

10. A method, according to claim 3, wherein the pressure at which the glaze is sprayed is of between 10 and 40 or more bar.

11. A method, according to any preceding claim, wherein the said matrix and/or said surface to be decorated are covered with adhesive substances for the glaze in powder form.

12. A method, according to claim 4, wherein it includes the following elements:

- compressed air pressure of 4 bar, much lower or much higher values are also possible;

13. A method, according to claim 2, 7, wherein it includes the following elements:

- Matrix of the moving band type, with one or more sectors, horizontal, inclined or vertical; peripheral velocity 25 m/min, possible or convenient from 15 to 40 or more m/min;

-Damp, liquid or even powdered glaze; insertion in the mesh of the screen by means of, respectively, squeegees, or pump and squeegees;

- distance of the section of band made to vibrate from the surface to be decorated from even less than 1 mm up to 20 mm or more, with loss of sharpness and shading obtained as the distance increases.

14. A method, according to claim 5, wherein it includes the following elements:

-matrix of the band type with incisions facing outward, having one or more sectors with incisions, horizontal, vertical or inclined; velocity of the band 25 m/min, possible or convenient from 15 up to 40 m/min or more;

-powdered glaze; insertion in the cavities of the screen from the outside by means of a squeegee; cavity possibly made adhesive;

-expulsion of the glaze from the cavities of the band by ultrasound vibrations, with a frequency of approximately 20.000 Hz and amplitude of approximately 0,08 mm;

-distance of the section of band made to vibrate from the surface to be decorated - possibly made adhesive - from 3 to 6 mm, tending towards zero, for example down to 0,1 mm, for maximum sharpness.

15. A method according to claims 12, 13, wherein the damp glaze consists of a powder suspended in polyglycol, having a density of 2000 g/l and a viscosity to prevent flow when the spoon containing the glaze is levelled and turned up side down.

16. A method according to claim 14, wherein the powdered glaze is of the impalpable type with low flow.

17. A method, according to claims 12, 13 wherein the matrix consists of a screen, for example made of polyester cloth, with motif that can be applied by photographic emulsion: the cloth having from 32 to 54 strands/cm with mesh openings from 0,19 to 0,10, it also being possible to have values of less than 10 strands/cm and up to even more than 80 strands/cm.

18. A method, according to claim 14, wherein the matrix consists of a polyethylene band with incisions made by mechanical removal having depths of 0,1-0,4 mm and up to even more than 1 mm.

19. A method, according to any preceding claims, wherein the distance A between said matrix and said item is varied in progress.

20. A method according to any preceding claims, wherein the difference between the speed of the matrix and the speed of the items to be decorated is varied in progress.

21. A machine for decorating items, suitable for implementing the method according to any preceding claims, wherein positioning means means are provided for positioning said item at a distance from a matrix through which the decorating fluid is forced, so that contact between said item and said matrix is avoided, associating means are provided for selectively associating said decorating fluid to said matrix and transferring means are provided for transferring the decorating fluid to the item to be decorated; said transferring means being capable of subjecting said decorating fluid to dynamic forces substantially greater than the gravity forces, so that the decorating fluid is projected onto said item by virtue of said dynamic forces.

22. A machine according to claim 21 , wherein said matrix consists of a screen having openings through which the decorating fluid is projected by means of a glaze atomizing nozzle (7), serving as associating means and as transferring means of said decorating fluid, said nozzle being supported in that part of the screen facing the underlying surface of the item (9) to be decorated, which is not in contact with the screen itself.

23. A machine according to anyone of claims 21 , 22, wherein said associating means comprises one or more squeegees (9, 10) incorporating the decorating fluid (11) into said matrix.

24. A machine according to claims 21 , 23, wherein said transferring means comprises a nozzle (7) directing pressurised gas from inside against the screen (2) in the zone facing the surfaces (12) of the items to be decorated in order to transfer said decorating fluid onto said surfaces.

25. A machine according to anyone of claims 21 , 23, wherein said matrix is provided with cavities and said transferring means includes vibrating means.

26. A machine according to claim 25, wherein said matrix is a moving band (56) matrix.

27. A machine, according to claim 26, wherein said band is provided with incisions on its outside, made up of one or more sectors, wound on rollers (60), at least one of which being motorized, with its external face sliding past the glaze (58) pressed by the squeegee (59) incorporating it in the matrix: there being applied, on the inside, in zone (B) of the matrix stretched between a pair of internal rollers (60) facing the surface (42) of the items to be decorated, a vibrator (61 , 62) to to transfer, onto the said items (42) to be decorated, the incorporated glaze.

28. A machine according to claim 25, wherein said matrix is a moving band (36) matrix, with one or more sectors, wound on rollers (37), at least one of which being motorized, passing between one or more squeegees (44) that incorporate the decorating fluid (46) into it: in zone (V) of the matrix facing the curved surface of the item to be decorated (41), stretched between a pair of internal, shaped runners (38) there being applied, on the inside, a vibrator (40) for transferring, onto said item to be decorated (41), the incorporated decorating fluid.

29. A machine according to anyone of claims 21 to 28, wherein said matrix consists of a rotor (1) having a cylindrical screen (2) matrix with one or more sectors.

30. A machine according to claim 21 , wherein said positioning means define a distance (A) between the matrix and the surface to be decorated in the range of about 1 mm up to about 10 mm.

31. A machine according to anyone of claims 21 to 30, wherein said matrix includes a rotor (1) with cylindrical screen (2) having one or more sectors.

32. A machine according to any of claims 21 to 31 , wherein downstream of the area where the decorating fluid is projected onto the items there is at least one scraper (11 and/or 12) sliding on it to remove excess glaze.

33. A machine according to anyone of claims 21 to 32, wherein downstream of the area where the decorating fluid is projected onto the item there is a cleaning jet (13; 14) of a cleanig fluid acting on the screen itself.

34. A machine, according to any one of claims 21 to 33, wherein on the internal side of the screen (2), downstream of the area where the decorating fluid is projected onto the item, there is at least one collecting trough, screen and discharge (15).

35. A machine, according to anyone of claims 21 to 34, wherein downstream of the area where the decorating fluid is projected onto the item at least one aspirator for excess decorating fluid is provided for.

36. A machine, according to any of claims 21 to 35, wherein a pump (48) is provided for to supply the decorating fluid to said transferring (48) is provided for to supply the decorating fluid to said transferring means.

37. A product obtainable with the implementation of the method of any claims 1 to 20, wherein it is decorated even on its edges and on those parts in general that are not coplanar with the surface to be decorated.

38. A product obtainble with the implementation of the method of any claims 1 to 20, characterised in that the decorative impression is of the shaded variety.

39. A method for synchronising flat ceramic elements transiting on a conveyor line towards processing machinery characterised in that it controls the position of the single tiles arriving at the machine (104; 113), it measures the delay of each tile (102) that is arriving in relation to the operator element (105; 112; 114) of the said machine (104; 113), it transmits a signal proportional to that delay to a control unit (PLC) able to temporarily vary the speed of a number of synchronising elements (107; 109, 109a; 109b; 118) for the said tile (102) distributed along the conveyor line, it temporarily varies the speed of the said synchronising elements (107; 109, 109a; 109b; 118) so as to advance the tile in such a way that it reaches a position of synchronisation with the said operator element (105; 112; 114).

40. A method, according to claim 39, wherein the synchronisation position is reached with the tile (102) moving along the conveyor line (103).

41. A method, according to claim 39, wherein the synchronisation position is reached with the tile (102) stopped on the conveyor line (103).

42. A synchronising machine, suitable for implementing the method according to anyone of claims 39 to 41 , including a conveyor line (103) transferring ceramic products (102) towards a decorating station (104; 113) positioned on the said conveyor line (103) and a synchronising device for the products positioned on the conveyor upstream of the said decorating station (104; 113), characterised in that the said synchronising device (101) consists of a number of pairs of aligned synchronising elements (107; 109, 109a; 109b; 118) that act on at least part of a pair of parallel sides of the tile (102).

43. A machine, according to the preceding claim, wherein the said 43. A machine, according to the preceding claim, wherein the said synchronising elements consist of pairs of rollers (107; 109, 109a; 109b) aligned with the conveyor line (103).

44. A machine, according to the preceding claim, wherein the said rollers (107) have axes that are perpendicular to a plane that passes through the top face of the tile (102), the said rollers being arranged in opposing rows each side of the conveyor line (103) of the tiles (102) in such a way that they act on the sides of each tile.

45. A machine, according to claim 43, wherein the said rollers (109, 109b) have horizontal axes and are aligned so as to constitute motorized horizontal roller conveyor defining a transit plane (PS) of the tiles (102) on the extension of the conveyor line (103).

46. A machine, according to the preceding claim, wherein the said rollers (109) have a central portion (109a) with a reduced diameter.

47. A machine, according to any of claims 42 to 46, wherein the ends of the said rollers (109, 109a) are splined and coupled to toothed belts (109b) defining the supporting and driving surface for the tiles (102).

48. A machine, according to one of the preceding claims, wherein in correspondence with the distance between adjacent rollers (109, 109a; 109b) there are aspirator devices (110, 111 ) to maintain the contact, by suction, between the said rollers (109, 109a; 109b) and the said tiles (102).

49. A machine, according to claim 43, wherein the said synchronising elements consist of pairs of lateral belts (118) wound in a loop on corresponding pulleys (119) and act on the sides of the tiles (102).

50. A machine, according to one of claims 42 to 49, wherein the said decorator element (105; 114) has exciter elements (106; 117) that excite sensors (S1) for controlling the decoration cycle.

51. A machine, according to one of claims 42 to 49, wherein the conveyor line (103) has a sensor (FC1) to signal the passage of the tiles (102).

52. A machine, according to one of the preceding claims, wherein the said rollers (107; 109, 109a; 109b) are independently motorized.

53. A machine, according to one of the preceding claims, wherein the said rollers (107; 109, 109a; 109b) are motorized in groups.