Method for application of granular and/or powder products on an article, and a device that carries out this method

Abstract

 A method for application of granular and/or powder products, for example powder enamel (1), onto an article (2), to reproduce an image or a pattern (D) includes: the preparation, by an electronic processor, of a digital matrix of the image or pattern (D); the definition of a digital mapping, derived from the digital matrix, laid out on a digital grid of points, with the mapping having stored therein the information necessary to recognize each point of the grid and to attribute to the same the color and hue parameters for the reproduction of the image or pattern (D); the use of the digital mapping to operate the opening and closing of the calibrated holes (3), through which measured quantities of the powder enamel (1) are released, falling onto the article (2), to define a plurality of enamel-dots (PS), arranged according to the digital grid, with each of the enamel-dots (PS) having a position, color and hue corresponding to what is stored in the digital mapping, so as to reproduce the prefixed image or pattern (D) on the article (2).
Afterwards, if included in the method, the enamel-dots (PS) are subjected to the baking action, so as to be made adherent to the article (2).

Description

DESCRIPTION OF THE INVENTION

[0001] The present invention relates to the technical field concerning the application of granular and/or powder products on articles, so as to produce the so-called "dry-decoration"; the articles can be formed by, for example, ceramic tiles for floor or wall tiling, while the granular and/or powder products are dry powder enamel.

[0002] As known, dry decoration includes a first step, in which the granular and/or powder product, having a prefixed granulometry is applied onto the surface to be decorated, in a suitable quantity and with a prefixed lay-out, so as to reproduce the pattern of the desired decoration.

[0003] In the particular case of ceramic tiles, to which a dry powder enamel is applied, there is a subsequent baking step, that allows to obtain the vitrification of the enamel and adherence thereof to the tile.

[0004] The publication EP 1 419 863, of the same applicant, discloses an apparatus for the application of dry powder enamel onto articles, especially ceramic tiles, that includes an endless belt of elastic material, which has a plurality of blisters, made on the outer surface of the belt for defining a decoration array and aimed at receiving the powder enamel, so as to place it on the articles passing thereunder, carried by a conveying line.

[0005] The belt, which is known in technical jargon as "sleeve", is placed sloping above the conveying line and is stretched between a roller motor, situated above, and a lower cusp, having a rounded tip, turned downwards, near to the upper surface of the tile to decorate.

[0006] The sleeve is operated by the roller motor in a direction concurrent and synchronized with the motion of the tiles on the conveying line, so that define a forward run of the sleeve can be defined upstream of the rounded cusp, and a backward run can be defined downstream of the same.

[0007] The powder enamel is fed in exceeding quantity to the forward run, near the cusp and directly upstream of means that move the exceeding enamel, which has not entered the blisters and that, at the same time, compress the enamel inside the blisters.

[0008] When the blisters reach the rounded tip of the cusp, whose radius of curvature is suitably small, they occur to be turned downwards and dilated due to the cusp sleeve curvature and thus the enamel powder contained therein falls, due to the gravity, onto the surface of the tile therebelow, to create the decoration.

[0009] The above mentioned apparatus represents the current state of the art concerning the quality of the results and the reliability of the system operation.

[0010] Other apparatuses, technically obsolete with respect to the above mentioned one, adopt a sleeve, that is stretched to define two horizontal runs, parallel to the surface to be decorated situated below.

[0011] Anyway, in all these apparatuses, it is absolutely necessary to have physically a decoration matrix, in this case the sleeve, whose production includes first the preparation of a digital matrix by an electronic processor, and then impressing blisters by a laser beam, controlled by said electronic processor.

[0012] Thus, whenever the decoration is changed or modified, it is necessary to make a new sleeve, with the time and costs it involves.

[0013] The above mentioned times and costs include also those necessary for the substitution of the sleeve on the machine, which must be periodically substituted because of wearing out, even without changing the decoration.

[0014] The necessity of making an "analogue" matrix before seeing any final result, makes slow and expensive the test phase, in which a new decoration must be set up, with subsequent tests, valuations and changes.

[0015] The above mentioned problems may be moderately or seriously penalizing, according to the environment, in which one must work. Actually, if the production unit is situated in an area with facilities for services and logistics, it is relatively simple to have what is necessary for making new sleeves in short time, at the same cost, while, instead, if the same production unit is situated in a badly served and/or isolated area, the sleeves supply can be difficult, with consequent expensive downtimes.

[0016] Therefore, the main object of the present invention is to propose a method for the application of granular and/or powder products, for example powder enamel, onto an article, according to a predetermined pattern, which is capable of giving better results with respect to known systems of dry decoration, in particular by eliminating the use of an "analogue" pattern, either a sleeve or similar means, for transferring the image onto the surface to be decorated, and using a digital matrix for this purpose.

[0017] Another object of the present invention, deriving from the application of the above method, is to propose a universal device for the application of granular and/or powder products, for example powder enamel, onto an article, according to a predetermined pattern, which is capable of reproducing the decoration, independently from its aspect, directly after the definition of a digital matrix.

[0018] A further object of the present invention is to propose a device, that allows changing or modifying the decoration in any moment, as it adapts instantly to such changes the means that apply the enamel powder onto the surface to decorate.

[0019] The characteristics of the proposed method and of a possible device that carries it out, will become evident from the following description, in accordance with the contents of the claims and with the help of the enclosed drawings, in which:

• Figure 1 is a schematic, lateral view of a device for carrying out the proposed method;
• Figure 2 is a schematic, plan view of the device of Figure 1;
• Figures 3A and 3B are enlarged, lateral views of the device printing head, closed and open, respectively;
• Figure 4A is a further enlarged view of a detail of the head of Figures 3A and 3B;
• Figure 4B is a view of an embodiment of what has been shown in Figure 4A;
• Figure 5 is an enlarged, plan view of an element of the printing head, in a first embodiment;
• Figure 6 is a view of an embodiment of the element of Figure 5;
• Figure 7 shows the head of Figures 3A and 3B with associated means for feeding the powder enamel;
• Figure 8 is a schematic view of a digital matrix of a decoration to be made on an article, projected by a monitor of an electronic processor;
• Figures from 9 to 15 are schematic views of single steps of the method, with which the device transfers the decoration of Figure 8 onto the article.

[0020] The method proposed by the present invention concerns the application of granular and/or powder products, for example, powder enamel 1, in a suitable quantity and according to a predetermined pattern, onto an article 2, so as to reproduce thereon an image or a pattern D, according to the technique known as "dry decoration".

[0021] The granular and/or powder product, for example powder enamel 1, is prepared in known way, so that it has the desired granulometry and a selected maximum residual moisture, in order to avoid compression of the powder that invalidates its optimal flowability.

[0022] The articles 2 include, for example, ceramic tiles for floor or wall tiling.

[0023] In the particular case of ceramic tiles, to which a dry powder enamel is applied, a subsequent baking step takes place, which allows obtaining the vitrification of the enamel of the pattern D and its adhesion to the tile 2.

[0024] The first step of the method includes the preparation, by an electronic processor equipped with a programming software developed on purpose, of a two-dimensional digital matrix, that reproduces the image or the pattern D to be transferred onto said article 2.

[0025] The second step of the method includes defining, by the above mentioned programming software (either the one of the previously mentioned electronic processor, or another one), a digital mapping, derived from said digital matrix, laid out on a digital grid of points.

[0026] The latter is suitably set up, so as to have dimensions corresponding to those of said article 2 and selected longitudinal and transversal resolutions; as known, resolution means the number of dots aligned, with regard to a measure unit, in the reference directions.

[0027] Digital mapping, by the programming software, stores data which are necessary to recognize each point of said grid and to attribute thereto the parameters related to the color and hue for the reproduction of said image or pattern D to be transferred onto the article 2.

[0028] The third step of the method concerns the use of said digital mapping for controlling shutters connected to relevant calibrated holes 3, by an operating software, suitably developed and interfaced with the above mentioned programming software, with consequent opening and closing of the same holes 3, through which measured quantities of the granular and/or powder product, for example powder enamel 1, are released, falling onto said article 2, so as to define a plurality of enamel dots PS, laid out according to the digital grid, with each of said enamel dots PS having position, color and hue corresponding to what is stored in said digital mapping, so as to reproduce the selected image or pattern D on said article.

[0029] A preferred embodiment of a device 100 that carries out the above mentioned method is described in Figures from 1 to 8.

[0030] The device 100 includes a known electronic processor, having the above mentioned programming and operating software; only the monitor M of the processor is schematically illustrated in Figure 8.

[0031] The programming software carries out the first two steps of the method, that is the preparation of said two-dimensional digital matrix, reproducing the image or the pattern D to be transferred to the article 2, and the definition of said digital mapping, derived from the digital matrix, laid out on a digital grid of points, with the dimensions of the latter corresponding to those of the article 2 and selected longitudinal and transversal resolutions.

[0032] The programming software, in particular, allows:

• preparing the above mentioned digital matrix according to a respective coding format;
• defining the structure of said digital grid of points of said digital mapping;
• acquiring the data of said digital matrix and introducing them in said structure, so that each point of said grid is accompanied by the data necessary for its recognition and for assigning said point the parameters related to the color and the hue for the reproduction of said image or pattern D to be transferred to the article 2.

[0033] The device 100 includes also means 10 for supporting and positioning said article 2, set in horizontal and with the surface to decorate 2A turned upwards.

[0034] In the example, the support means 10 include a known conveying line, on which the articles 2 are placed, previously centered; the conveying line 10 has powered means for forward movement (not shown as known), aimed at moving longitudinally the article 2 in a forward direction W, from an inlet station to an outlet station, with a printing station S situated therebetween.

[0035] Said forward movement means are powered by, for example, brushless or stepper motors, suitable for being driven electronically.

[0036] The device 100 includes, in a position corresponding to said printing station S, at least one set 20 of printing heads, parallel one to another and situated above the article 2, crosswise with respect thereto and near its surface to decorate 2A (Figures 1 and 2).

[0037] In the shown example, the set 20 is formed by five printing heads 21, 22, 23, 24, 25, each for a selected hue of the same color, as it will be better specified later.

[0038] Thus, the device 100, shown in the Figures, is aimed at transferring only monochromatic decorations D; the example has been presented in this way for evident simplicity reasons, however it is obvious that there can be more sets 20 of printing heads, arranged in series, related to as many colors.

[0039] With four sets 20, prepared for powder enamel of red, yellow, blue and black color, respectively, it is possible to prepare a printing station S aimed at working according to the same concept as the ink type printing, known as four-color printing, in the way described later.

[0040] Each printing head 21, 22, 23, 24, 25 has a "V"-like hopper 4, that contains said granular and/or powder product, for example powder enamel 1, and that has an extension at least equal to the width of the article 2 and that has a plurality of calibrated holes 3, made in its bottom, arranged in a row and spaced out stepwise, in accordance with the transversal resolution defined by the points of said digital grid.

[0041] Each of said calibrated holes 3 has shutter means 30, operated by a related actuator 31, to allow the calibrated hole 3 to be opened and closed, thus determining the release, by falling, through the latter, of measured quantities of the granular and/or powder product, for example powder enamel 1, onto said article 2, to define a corresponding enamel dot PS; in the example, the shutter means 30 include a needle valve, made of anti-abrasion material, arranged in vertical in the hopper 4, with said actuator 31 situated above and out of the hopper.

[0042] All the actuators 31, formed by known electromagnetic devices, or piezoelectric or the like, are operated independently one from another, for the periods of time adjustable within a prefixed range.

[0043] As already mentioned, each printing head is prepared to reproduce a specific hue, which depends on the diameter of said calibrated holes 3, as well as on the opening time thereof; some values, deduced experimentally, by way of example, give a correlation between the hole diameter and the hue range, with the minimum and maximum opening time, respectively:

➢ head 21 - hole Ø 0,1 mm - hue of the enamel dot 0 ÷ 5 %

➢ head 22 - hole Ø 0,2mm - hue of the enamel dot 5 ÷ 25 %

➢ head 23 - hole Ø 0,3mm - hue of the enamel dot 25 ÷ 50 %

➢ head 24 - hole Ø 0,4mm - hue of the enamel dot 50 ÷ 75 %

➢ head 25 - hole Ø 0,5mm - hue of the enamel dot 75 ÷ 100 %

[0044] The holes 3 diameters can vary from the indicated ones together with varying of the enamel powder 1 granulometry.

[0045] According to a preferred constructive solution, the calibrated holes 3 have an "hour-glass" section (see especially Figure 4A), in which the diameter Ø indicated above for each head is the minimum passage one, pointed out with dimension lines in the same Figure 4A.

[0046] This form turns out to be advantageous for ensuring tightness of the upper area of contact with the conical tip of the needle valve 30 (Figure 3A), as well as for facilitating the flow of the enamel powder 1 in the lower area to the minimum passage section (Figure 3B).

[0047] Alternatively, according to a simpler constructive solution, the calibrated holes 3 have a tapered section (see Figure 4B), in which the diameter Ø indicated above for each head is the minimum passage one, situated below and pointed out with dimension lines in the same Figure 4B.

[0048] Each hopper 4 has feeding means 40, aimed at maintaining a certain level of powder enamel 1 inside the hopper.

[0049] It is important for the printing head good operation that said level be sufficiently constant along the extension of the same hopper 4, even with a consumption, that for some decorations can vary from one area to another or it can be located only in one of them.

[0050] A possible embodiment of said feeding means 40, that takes into consideration the above need, is shown in Figure 7: a small tank 41, situated beside the hopper 4, at a higher level with respect thereto, contains the powder enamel 1 and has the same longitudinal extension as the hopper 4 and its lower part is closed by a semi-circular bottom 42.

[0051] A horizontal shaft 43, centered with respect to the bottom 42 connection curvature, is situated inside the tank 41. Radial blades 44, having selected width, are hinged to the shaft 43, mutually side by side along the shaft 43 axis, so as to cover the whole extension of the tank 41.

[0052] Each radial blade 44 can be set into rotation in a direction Z, independently from one another, by motor means, not shown, and has a flexible wiper 45, aimed at scraping on the bottom 42 of the tank 41.

[0053] Each radial blade 44 is associated with a lamellar valve 46, arranged vertically on the wall 47 of the tank 41, turned toward the hopper 4 and having the same width as the blade 44. The blade 44, due to its rotation, carries a part of powder enamel 1 first upwards and then it comes to press the lamellar valve 46, forcing it to open, thus allowing a certain quantity of powder enamel to be poured to the hopper 4 situated below.

[0054] It is possible to maintain sufficiently constant level of the enamel powder 1 inside the hopper 4, as required, by operating selectively the radial blades 44 corresponding to the hopper areas of larger consumption.

[0055] Figure 5 shows a portion of the hopper 4 of a printing head, with the calibrated holes 3 aligned and spaced out by a pitch P, corresponding to the transversal resolution of the digital grid.

[0056] If the set resolution is too high for making holes with larger diameter, or is not compatible with the dimensions of the needle valves 30, and/or of the actuators 31, it is possible to divide the corresponding printing head in two consecutive hoppers 4A, 4B (Figure 6), in which the pitch P2 between one hole 3 and another in the same hopper is doubled; with a suitable misalignment of the two series of holes, it is possible to maintain the effective pitch P at the same previous value of Figure 5.

[0057] Obviously, if that is not enough, each printing head can be further divided into three or more hoppers.

[0058] Thermostated heating means, not shown, for example resistor, can be associated to the printing heads of each set 20, for keeping the powder enamel 1 contained in the hoppers 4 within prefixed humidity values.

[0059] The device 100 can advantageously have a system for removing the condensation, that could have formed above the surface to decorate 2A, if the article 2 is hot, like in the ceramic tiles case.

[0060] The system 28, for example using vacuum, shown schematically in Figure 7 with broken lines, can include only one suction unit, situated at the inlet of the printing station S, or more units, situated each one upstream of a respective set 20, or again upstream of each printing head, according to the needs.

[0061] Finally, the device 100 includes operating means, not shown, controlled by said electronic processor and aimed at driving, in mutual step relation, the shutter means 30 and the forward movement means of the conveying line 10, according to the program defined by said digital mapping, to determine the release, due to the gravity, through the calibrated holes 3, of measured quantities of the granular and/or powder product, for example powder enamel 1, destined to form, on the surface 2A below, corresponding enamel-dots PS, whose position, color and hue are in accordance with what is stored in the same digital mapping, so as to reproduce the prefixed image or pattern D on said article.

[0062] The above mentioned operating means are driven by an operating software, that allows:

• communicating with said programming software of the digital mapping (in this connection see the description of the second step of the method), to use the data stored in the latter and defining a program for producing the pattern D;
• supplying the activation/deactivation signals of the powered means for article 2 forward movement, controlling the position of the latter with respect to the pattern D execution program;
• supplying the activation/deactivation signals of the actuators 31 of the shutter means 30 to open and close the selected calibrated holes 3, in time relation with the article 2 forward movement and in accordance with the contents of said pattern D execution program;
• feedback controlling the operation parameters of said powered means of forward movement and shutter means, comparing them with corresponding parameters of the pattern D execution program;
• signaling possible differences between the detected operation parameters and the arranged ones.

[0063] In order to make more evident what has been described hereinabove, operation of the device 100 will be now described step by step, for transferring the pattern D shown on the monitor M in Figure 8, onto the article 2. The pattern D must be formed, in ascending order of size, by enamel-dots PS1, made by the head 21, enamel-dots PS2 made by the head 22, enamel-dots PS3 made by the head 23, enamel-dots PS4 made by the head 24 and enamel-dots PS5 made by the head 25.

[0064] For better understanding of the plan-view figures, from 9 to 15, the following must be borne in mind:

• the heads 21, 22, 23, 24, 25 are indicated with respective dot and dash lines;
• each in-operation head is pointed out in each Figure by a little circle enclosing the relevant reference number;
• each enamel dot applied on the article by the in-operation heads is pointed out in each figure by surrounding radial lines, with light-on effect;
• each enamel dot applied on the article by the passage preceding each figure lacks any remark, with light-off effect.

[0065] The article 2, moved in the forwarding direction W, reaches the printing station S and meets the first head 21 (Figure 9); when the longitudinal position of the article 2 is correct, the shutter means 30 of the two calibrated holes 3, related to the transversal positions, in which the two enamel-dots PS1 are to be applied, are operated.

[0066] According to the example, the two enamel-dots PS1 are situated on the same transversal line, therefore the opening of the two calibrated holes 3 is contemporaneous; the opening time of each one depends on the hue to be attributed to the respective enamel dot PS1, within the respective range.

[0067] The article 2 continues its forward movement and meets the second head 22 (Figure 10); when the longitudinal position of the article 2 is correct, one operates the shutter means 30 of the calibrated hole 3, related to the transversal position, in which the enamel-dot PS2 is to be applied.

[0068] As it has been said before, the opening time will depend on the hue to be attributed to the enamel dot PS2.

[0069] In Figure 11, the article 2, moved further, engages four heads, in the example three of which are contemporarily operational, exactly the first 21 head for the application of another enamel dot PS1, the second head 22 for the application of a further enamel dot PS2 and the third one 23 for an enamel dot PS3 (distinguishable by the light-on effect from other points applied in the previous passages of Figures 9 and 10).

[0070] In Figure 12, the article 2 comes to engage also the fifth head 25, which is operated to apply a enamel dot PS5. At the same time, according to the mapping, the first head 21 is operated again to apply another enamel dot PS1.

[0071] Figure 13 shows the application of an enamel dot PS4 by the fourth head 24, nor yet operated up to now.

[0072] Figure 14, where the article 2 continues its forward movement, shows the application of an enamel dot PS4 by the fourth head 24; according to the example, the open calibrated hole is the same as the one in Figure 13, since the two enamel-dots PS4 are longitudinally aligned.

[0073] In Figure 15 a last enamel dot PS5 is made on the article 2 by the head 25, before the article leaves the printing station S, with the pattern D completed according to what has been displayed on the monitor M of Figure 8.

[0074] Obviously, the cited example refers to a pattern D of a basic form, to make clear the proposed method; in practice, with complicated patterns, more heads and holes will be activated.

[0075] In order to obtain patterns D according to the above mentioned four-color printing, each enamel dot must be formed by a suitable mixture of red, yellow, blue and, if necessary, black powder enamel, so as to obtain all the needed color shades, like in the ink type printing.

[0076] The above mentioned mixture is formed by applying the selected quantities of red, yellow, blue and black enamel to the same enamel dot, by the respective sets of heads, in subsequent times.

[0077] It can be understood now, how the proposed method and device are innovative in the dry decoration field.

[0078] Actually, the absence of any analogue matrix, substituted by a digital matrix, that can be modified or changed at will, obtaining directly a corresponding modified or different pattern, without additional costs, allows expanding the operational potential of the dry decoration up to levels which have been unthinkable until now.

[0079] The four-color printing makes it possible to reproduce very complicated images, for example a photographic shot, obtaining a definition and performance of detail, that are unattainable at present with known apparatuses.

[0080] The only element of the device subjected to wear can be the hopper 4 of each head, due to the abrasive effect of the powder enamel on the calibrated holes 3, which widens them in time.

[0081] However, this is a negligible problem, because the hopper is a simple element, produced at low cost from an abrasion resistant material, and because its substitution, when necessary, is a quick operation and does not require subsequent phasing operations.

[0082] Moreover, the absence of a "physical" die allows to eliminate its production costs, as well as the logistic problems connected with the same supply, discussed in the introductory note.

[0083] The digital matrix and/or the digital mapping can be prepared at any distance and sent to the production unit by electronic supports, such as disks and the like, or using "on line" connections, like e-mail.

[0084] A final, but not less important advantage of the proposed method and device with respect to the known sleeve apparatuses, relates to the saving obtained by the elimination of the wastes of expensive enamel powder, that occurs in these apparatuses due to the fact that in order to fill the blisters, it is necessary to feed the exceeding powder enamel, trim the sleeve to remove the excess and make it re-circulate, which inevitably leads to volatilization of a part of it during these steps. In addition, the dispersion of powder enamel in the air must be controlled properly, since it is very dangerous for the operators' health.

[0085] It is understood anyway that what said above has an illustrative and not limiting value, therefore possible small corrections of the method steps and/or modifications of the device carrying it out, remain within the same protective scope defined by the claims below.

Claims

1. Method for the application of granular and/or powder products, characterized in that it includes:

- preparation, by an electronic processor, of a two-dimensional digital matrix, reproducing an image or a pattern (D) to be transferred to said article (2);

- definition, by an electronic processor, of a digital mapping, derived from said digital matrix, laid out on a digital grid of points, with the dimensions of the latter corresponding to those of the article (2) and with selected longitudinal and transversal resolutions, with said digital mapping having stored therein the information necessary to recognize each point of said grid and to assign each said point the color and hue parameters for the reproduction of said image or pattern (D) to be transferred to said article (2);

- use of said digital mapping to handle shutters, associated to respective calibrated holes (3), with consequent opening and closing of the same holes (3), through which measured quantities of the granular and/or powder product (1) are released, falling onto said article (2), to define a plurality of enamel-dots (PS), arranged according to said digital grid, with each of said enamel-dots (PS) having a position, color and hue corresponding to what has been stored in said digital mapping, so as to reproduce the selected image or pattern (D) on said article (2).

2. Method, according to claim 1, characterized in that said steps of preparation of the digital matrix and definition of the digital mapping are obtained by a programming software, installed in said electronic processor, and in that said step of operating the shutters associated to the calibrated holes (3) is driven by an operating software, interfaced with said programming software.

3. Device for the application of granular and/or powder products onto an article, characterized in that it includes:

- an electronic processor, which stores a two-dimensional digital matrix, related to an image or a pattern (D) to be transferred onto said article (2), and a digital mapping, derived from said die and laid out on a digital grid of points, with the dimensions of the latter corresponding to those of said article (2) and selected longitudinal and transversal resolutions; with said digital mapping storing the information necessary to recognize each point of said grid and to attribute thereto the parameters related to the color and hue for the reproduction of said image or pattern (D) to be transferred onto the article (2);

- means (10) for supporting and positioning of said article (2), with horizontal orientation and with the surface to decorate (2A) turned upwards;

- at least one set (20) of printing heads (21, 22, 23, 24, 25) parallel one to another and situated above the article (2), crosswise thereto and near its surface to decorate (2A); with each printing head (21, 22, 23, 24, 25) having a hopper (4), that contains said granular and/or powder product (1), and whose extension is at least equal to the width of the same article (2) and has a plurality of holes (3), made in its bottom and calibrated in accordance to the hue that each printing head (21, 22, 23, 24, 25) is to reproduce, with said holes (3) arranged in a row and spaced out stepwise, in accordance to the transversal resolution defined by the points of said digital grid;

- shutter means (30), associated to each of said calibrated holes (3) and operated by a respective actuator (31), to allow the calibrated hole (3) to be opened and closed;

- powered means for forward movement, associated to said support means (10) and moving longitudinally said article (2) by steps corresponding to the longitudinal resolution defined by the points of said digital grid;

- operating means, powered by said electronic processor, aimed at driving, in mutual step relation, said shutter means (30) and the forward movement means, according to the program defined by said digital mapping, to determine the release, due to gravity, through said calibrated holes (3), of measured quantities of the granular and/or powder product (1), that define on said surface to decorate (2A), situated below, corresponding enamel-dots (PS), whose position, color and hue correspond to what is stored in the same digital mapping, so as to reproduce the prefixed image or pattern (D) on said article (2).

4. Device, according to claim 3, characterized in that said electronic processor includes a programming software aimed at:

- preparing said digital matrix according to a respective coding format;

- defining the structure of said digital grid of points of said digital mapping;

- acquiring the data of said digital matrix and introducing them into said structure, so that each point of said grid is associated to information necessary for its recognition and the parameters related to the color and hue for the reproduction of said image or pattern (D) to be transferred onto the article (2) are attributed to said each point,

and in that said programming software is interfaced with an operating software, aimed at:

- communicating with said programming software of the digital mapping, to use the data stored in the latter and to define a program for the pattern (D) execution;

- supplying signals of activation/deactivation of the powered means of forward movement of the article (2), controlling the position of the latter with respect to said pattern (D) execution program;

- supplying the signals of activation/deactivation of the actuators (31) of the shutter means (30) to open and close the selected calibrated holes (3), in time relation with the article (2) forward movement and in accordance with the contents of said pattern (D) execution program;

- feedback controlling of the operation parameters of said powered means of forward movement and shutter means, comparing them with the corresponding parameters of said pattern (D) execution program;

- signaling possible differences between the detected operation parameters and the ones of the pattern execution program.

5. Device, according to claim 3, characterized in that said support and positioning means (10) are defined by a conveying line and in that said forward movement powered means include motors aimed at being driven electronically.

6. Device, according to claim 3, characterized in that it includes at least four said sets (20) of printing heads (21, 22, 23, 24, 25), each being provided for red, yellow, blue and black granular and/or powder product (1), respectively, with the same four sets (20) aimed at forming, by subsequent inputs, enamel-dots (PS), each of which formed by a prefixed mixture of enamels of the above mentioned colors.

7. Device, according to claim 3 or 6, characterized in that each of said sets (20) is aimed at reproducing one color and includes at least five printing heads (21, 22, 23, 24, 25), that define a gradual scale of said color varying from a minimum to a maximum.

8. Device, according to claim 3 or 6 or 7, characterized in that said hopper (4) of said printing heads (21, 22, 23, 24, 25) has a "V"-like shape.

9. Device, according to claim 3, characterized in that said calibrated holes (3) have a double flare profile, in which the calibrated diameter is situated in a position corresponding to the minimum passage section.

10. Device, according to claim 3, characterized in that said calibrated holes (3) have a truncated-cone profile, in which the calibrated diameter is situated lower, in correspondence to the minimum passage section.

11. Device, according to claim 3, characterized in that said shutter means (30) include a needle valve, arranged in vertical in said hopper (4), with said actuator (31) situated above and out of the hopper (4).

12. Device, according to claim 3 or 9, characterized in that said actuators (31) include devices, aimed at being driven electronically.

13. Device, according to claim 3, characterized in that each of said hoppers (4) has feeding means (40), that keep a selected level of granular and/or powder product (1) thereinside.

14. Device, according to claim 11, characterized in that each of said feeding means (40) supplies selectively sections of said hopper (4), arranged side by side along the extension of the latter, in presence of differentiated consumption of granular and/or powder product (1) thereinside.

15. Device, according to claim 11 or 12, characterized in that said feeding means (40) include a small tank (41), containing a granular and/or powder product (1) and situated beside said hopper (4), higher with respect thereto, and having the same longitudinal extension as the hopper (4), with said small tank (41) having, inside, a plurality of radial blades (44), arranged mutually side by side and hinged to a common horizontal shaft (43), with each of said radial blades (44) being selectively set to rotate by motor means, to withdraw granular and/or powder product (1) from said tank (41) and to pour it in the section of said hopper (4) situated below, through a corresponding lamellar valve (46) made in said tank (41).

16. Device, according to claim 13, characterized in that said tank (41) has a semicircular bottom (42), with said shaft (43) arranged centered with the bottom (42) - side curvature, and in that each of said radial blades (44) has, at its end, a flexible wiper (45), that scrapes on said semicircular bottom (42), due to said rotation of the radial blade (44).

17. Device, according to claim 3, or 6, or 7, or 8 characterized in that it includes, for each of said printing heads (21, 22, 23, 24, 25), at least two hoppers (4A, 4B), in each of which said calibrated holes (3) are spaced by a multiple pitch with respect to said transversal resolution, with the series of calibrated holes (3) of one hopper misaligned with respect to the other, so as to maintain an effective pitch corresponding to the transversal resolution.

18. Device, according to claim 3, or 6, or 7, or 8, characterized in that it includes thermostated heating means, associated to said printing heads (21, 22, 23, 24, 25), that maintain the powder enamel (1), contained in the respective hoppers (4) within prefixed humidity values.

19. Device, according to claim 3, or 6, or 7, or 8, characterized in that it includes a vacuum system (28), situated above said surface to decorate (2A) and aimed at eliminating the condensation vapor, produced by the heat emanated by said article (2) and hanging over said surface to decorate (2A).

20. Device, according to claim 19, characterized in that said system (28) includes a suction unit, situated at the inlet of said printing station (S).

21. Device, according to claim 19, characterized in that said system (28) includes a suction unit, situated upstream of each of said sets (20) of printing heads (21, 22, 23, 24, 25).

22. Device, according to claim 19, characterized in that said system (28) includes a suction unit, situated upstream of each of the printing heads (21, 22, 23, 24, 25).

Drawing