ES2383991T3 - Apparatus for decorating ceramic products - Google Patents

Abstract

An apparatus (10) for decorating ceramic tiles (11) includes combined use of printing heads (13) consisting of elastic silicone cylinders (15) provided with recessed cell matrices, and inkjet-type printing heads (14, 14' ) , arranged sequentially above a conveyor belt (12) bearing the tiles to be decorated. The inkjet nozzles are electronically commanded according to activation rhythms and times suitable for continuously producing patterns and graphics having a length congruent with the length of the patterns and graphics produced by the elastic recessed cell matrices, the activation of the nozzles further being suitably synchronised with the angular position of the cylinders and of the conveyor belt. The above-mentioned apparatus provides, alongside a high level of reliability and limited financial outlay, a considerable production flexibility, typical of inkjet machines

Description

Apparatus for decorating ceramic products.

Technical Field

The present invention relates to an apparatus for decorating ceramic products.

In particular, the present invention can be applied in a useful way to decorate ceramic tiles of various types in highly flexible production programs.

Existing Technique

As is well known, the decoration of ceramic industry products takes place mainly using the traditional screen printing technique, using rotary or flat machines, or using rotary machines provided with engraved elastic matrices that work in accordance with the flexographic or gravure process, in which the enamel to be transferred to the tile is placed on the protuberances of the matrix or in its cavities, respectively.

Compared to the other techniques already mentioned, the technique of intaglio matrices has particular advantages and characteristics, such as, for example, the possibility of decorating in proximity to the edges of the tiles, the ease of obtaining gradations of color or halftones , faster execution speed and also requires less maintenance and adjustment.

Anyway, whether using the screen printing technique or the technique of engraved elastic matrix, it is possible to obtain new decorative motifs only by creating new printing masks, whether they are composed of rollers or screen printing grids or new matrices and, obviously, This means a considerable effort in terms of material and time.

Such problems are solved by the latest inkjet printing machines, which comprise a nozzle collector sent by a computerized control unit in a memory from which the appropriate nozzle control sequence is stored to obtain the design or desired graphic on the tile.

With these machines it is possible to change the graphic without having to replace any device or component, but simply by varying the sequence of electronic controls stored in the memory of the control computer; in addition, it is possible to obtain special decorated pieces, since there is no contact between the surface to be decorated and the print head; and, on the other hand, enamel waste is significantly reduced. All this, however, is achieved with significantly higher plant costs compared to those of rotary machines, along with the risks associated with a technology not yet perfected.

EP-A1-1.098.689 discloses an apparatus for decorating ceramic tiles in accordance with the preamble of claim 1.

The main objective of this invention is to propose an apparatus for decorating ceramic tiles, in which it is possible to easily vary the shapes of the decoration using a low-cost structure and proven reliability.

Another objective of this invention is to propose an apparatus for decorating ceramic tiles or similar items, which can be easily integrated and used with existing production plants.

Said objectives and still others are obtained by a machine for decorating ceramic tiles according to claim 1.

The different printheads, rotary or inkjet, are synchronized with each other in accordance with a predefined phase relationship to ensure that the decoration parts produced by each individual head are conjugated together to form the general decoration that is desired. Synchronization according to a given phase relationship can also take place between the printheads and the means of transport of the products to be decorated. Preferably, the injectors sent electronically are arranged according to adjacent rows, above the means for transporting the tiles or tiles, the length of each row of injectors corresponding to the maximum width of the surface to be decorated. The injectors are uniformly separated from each other, in the adjacent rows, according to a configuration such that the injectors comprised in a row are arranged staggered, according to the direction of advance of the tiles, with respect to the injectors of the adjacent rows . The sequence of controls of the nozzles of a given printhead is such as to make successive rows of the decoration as a result of a continuous electronic scanning of an electronic map of the decoration stored in the memory of the print head control unit. The exploration is repeated in succession, so as to produce the same result that would occur with a continuous rotation roller that had the same decoration. A photocell capable of detecting the presence of the tile under the print head enables or disables the ink jet coming from the various nozzles of the head. The correct phase relationship between the activation sequence of the injectors and the angular positions of the rotating elastic matrices present in the apparatus is stored and then automatically invoked and restarted when the apparatus is activated.

For the sake of the foregoing it is clear that the apparatus of the present invention offers undoubted advantages in comparison with the apparatus of the known technique, in terms of both quality and variety of the decorations that can be obtained and in terms of general reliability.

Disclosure of the Invention

Other advantages and features of this invention will become even more apparent from the following detailed description of a preferred but not exclusive embodiment of the present invention, shown purely by way of example and not limiting in the attached figures, in which:

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 Figure 1 shows a schematic side elevation of the decorating apparatus according to the present invention;

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 Figure 2 shows a plan view from above of the apparatus of Figure 1.

Figure 1 shows a particular apparatus (10) for decorating ceramic tiles (11). The tiles (or tiles) (11) advance along the production line moved by a conveyor belt (12).

The apparatus (10) comprises printheads (13) of the type known as Rotocolor and printheads (14, 14 ’), of the inkjet type.

The Rotocolor printheads (13) comprise an elastic silicone cylinder (15) that supports the die with cavities in which the figure to be transferred to the tile (11) has been obtained; the enamel of the appropriate color is collected from the collection tray (16) using the pump (18) and is distributed, through the feeder conduit (19) into the cavities displayed on the surface of the cylinder (15) with the help of a scraper (20) supported and located through appropriate means (21). The excess enamel returns to the tray (16) through the collection channels (22).

The inkjet printheads (14 and 14 ’) comprise one or more groups (24) of nozzles distributed along adjacent rows. The groups of nozzles (24) that constitute the truly said inkjet printheads are fixed to a support body (25) independently of each other as in the case of the head denoted with 14 or linked to move together as in the case of the head denoted with 14 '. A self-leveling tank (26) associated with each of the groups, or printheads (24), is continuously fed from the main tank (27) through a suitable pump (28) and a refill line (29) . In addition, a sponge (30) is associated with each of the printing groups, or heads (24), for reasons of protection and cleaning. In addition, a photocell is arranged near the surface of the conveyor belt (12), which serves to detect the presence of the tile (11) between the two terminals, transmitter and receiver (31 and 32), of the same photocell

In the embodiment illustrated here, the apparatus comprises a set of four printheads, two of the Rotocolor type and two of the inkjet type, distributed according to the sequence indicated in the attached sheet of figures.

In accordance with the specific production requirements and, therefore, with the type of tiles and the decorations to be made, the apparatus of the present invention may be constituted by a greater or lesser amount of printheads, distributed in different ways.

The operation of the apparatus of the present invention takes place as described below.

Once the shape and color tones of the decoration have been defined, it is decided in a timely manner which part of the general figure, and which color shade, should be carried out by which printhead, the assignment and selection criteria being related to the ability and the experience of the staff and the characteristics of the plant that is available.

The part of the figure to be made using a given Rotocolor printhead is obtained using a well defined intaglio elastic matrix with said part of the decoration to be made.

The part of the figure to be made using a given inkjet printhead is obtained by subdividing the part of the figure into a certain amount of successive printing lines of a predetermined thickness, where it is possible to obtain each of said printing lines by means of a given combination of controls to the injectors included in the printhead. Then, the successive combinations of controls concerning the successive lines of printing are stored in the memory of the nozzle control unit, thus creating an electronic map of the figure to be made. In practice, the above is obtained simply by "reading" in succession the various lines of the map and activating the injectors according to the combinations of controls included in each line.

The printhead, then, behaves exactly like the continuous printing roller since the "reading" of the various lines of the electronic map starts again from the first of these lines each time it reaches the last of them. .

Obviously the printing speed is related to the reading frequency of the various lines and the execution times of the individual printing line, the speed having to be properly calculated in relation to the speed of advance of the tile (11) on the belt (12), and synchronized with it.

It is also evident that the length of the decoration that can be obtained with a given inkjet printhead must be equal to a multiple, or congruent anyway, of the length of the decoration that can be obtained with a Rotocolor printhead which is part of the same device; and that, to ensure an exact combination of the parts of the decoration made by the different printheads, the reading or scanning of the electronic map associated with a given inkjet printhead must begin in correspondence of a predetermined angular position in the cylinder of a given Rotocolor printhead. In other words, the pointer to the print line of an inkjet printhead varies depending on the signal produced by the position encoder associated with a cylinder of the Rotocolor printhead that is in the same apparatus.

In this regard, it should be taken into account that the print heads of the rotating elastic matrix, in the case that there is an amount greater than one in the apparatus, as in the case illustrated, are synchronized with each other based on a given phase-based relationship to the known master / slave techniques, in which a certain reference position (master) can be obtained from the position of the conveyor belt (actual master) or from an electronic signal generator of the reference signal (virtual master) ).

It should also be noted that if an exact phase relationship is predetermined between the angular position of the printing cylinders and the position of the tile on the tape, on the various tiles or tiles, well-defined and repeated decorations are obtained, while when there is no such phase relationship, but there is simply synchronism between the speed of rotation of the cylinders and the speed of advance of the conveyor belt, the decorations or decoration parts obtained are randomly printed on the various tiles. . The foregoing is also valid for the decoration parts made with the inkjet printheads, which, as stated above, behave exactly like synchronized virtual cylinders, according to a given phase relationship with Rotocolor cylinders .

The photocell predisposed to detect the presence of the tile or tile under a given inkjet head, enables or disables the output of the ink jet from the various injectors of the head, in order to prevent expensive and useless waste of enamel. The signal produced by the photocell with the arrival of the tile

or tile can also determine the location of the pointer in correspondence of the print line for that inkjet head and in this way, in this case a well defined part of the decoration is made in each tile, always corresponding to the decoration parts made using the other heads of the apparatus.

Once the phase relationship is established between the various printheads of the device, whatever the type, and activated with the appropriate predisposition / registration operation, it is automatically stored and invoked in correspondence of each successive start-up of the device, until it becomes restarted

Obviously, in the memory of the control unit of an inkjet printhead it is possible to store several and different electronic maps, which can be selected depending on the type of decoration to be made.

The decoration apparatus of the present invention offers clear advantages, in terms of extreme flexibility and quality of the production processes that can be achieved and, furthermore, in terms of reducing the costs of materials used in the process and reduction of the general costs of the plant, thanks to the transformation or adaptation of already existing rotary machines.

The various memory maps can obviously be stored in memory media of the control unit or in external memory media that can be placed in the control unit or connected to the latter when a certain decorating operation is performed.

The characteristics and operational advantages associated with the apparatus of the present invention are protected even in the case of introduction of variants or modifications to the execution described above.

For example, the dimensions of each group or printhead (24) could vary depending on the applications; In addition, the number or groups of nozzles in the same printhead (14, 14 ’) could also vary.

Also, the number of rows of injectors in each group and, therefore, the resolution that can be obtained, obviously can vary depending on the applications.

The means for actuating the various groups of inkjet injectors could be different

types and the same applies to the means for moving tiles, tiles or similar products, on which

decoration must be done.

The synchronization of the various printheads with each other and with the advance means of the products to be decorated can be done by placing sensors and using techniques different from those illustrated above by way of example. Also, the sensors that are simply used to detect the tile or tile under the printhead may differ from the photocell sensors used in the example above.

Claims (11)

 1.- Apparatus for decorating ceramic tiles (or tiles) or similar products comprising means for transporting the products to be decorated, where it comprises, rotary printing heads constituted by rotating elastic matrices and inkjet printing heads constituted by injectors of inkjet sent by electronic control units, characterized by the fact that the electronic control units are suitable for executing sequences and command times suitable for making decorations on a surface of the products, the decorations having a congruent length with a length of the decorations printed by said rotating elastic matrices, the electronic control units being able to send the nozzles of each inkjet printhead (14, 14 ') in accordance with a sequence of commands so as to execute successive lines of the decoration, after an exploration electronics of the lines into which an electronic map of the decoration stored in the memory of the inkjet printhead control unit is subdivided, so that scanning of the electronic map associated with a given jet printhead of ink begins in correspondence of a predetermined angular position of the rotary elastic matrix of a given rotary print head. 2. Apparatus (10) according to claim 1, wherein the rotary print heads consisting of rotary elastic dies and inkjet print heads (13, 14, 14 ') are also synchronized with each other, according to a phase relationship predetermined, to ensure that the decoration parts produced by each individual head correspond to the others so as to produce the general decoration that is desired to be obtained. 3. Apparatus (10) according to claim 2, wherein also the rotary print heads consisting of rotary elastic dies and inkjet print heads (13, 14, 14 ') are synchronized, in accordance with a phase relationship predetermined, with the means to transport (12) the products to be decorated (11). 4. Apparatus (10) according to any one of the preceding claims 1 to 3, wherein the inkjet print heads (14, 14 '), consisting of ink jet nozzles sent by electronic control units, comprise groups (24) of injectors arranged according to one or several adjacent rows, above the means of transport (12), the length of each group of injectors corresponding to the maximum width of the surface to be decorated. 5. Apparatus (10) according to claim 4, wherein the groups of nozzles (24) comprised in a specific inkjet printhead (14) are fixed to a support frame (25) so that they are mechanically independent each. 6. Apparatus (10) according to claim 4, wherein the groups of nozzles (24) comprised in a particular inkjet printhead (14 ') are fixed to a support frame (25) so as to be connected each other mechanically. 7. Apparatus (10) according to claim 5 or 6, wherein the injectors included in a group of injectors (24) are uniformly separated in adjacent rows so that the injectors comprised in a row are staggered relative to the adjacent rows of injectors according to the direction of advance of the conveyor belt. 8. Apparatus (10) according to claim 1, wherein the exploration is carried out continuously, starting again from the first of the lines when the last one has been reached, so as to make decorations continuously, analogously to the operating mode of the rotary print heads (13) which are composed of rotary elastic dies. 9. Apparatus (10) according to any one of the preceding claims 1 to 8, wherein the inkjet print heads (14, 14 ') constituted by ink jet injectors sent by electronic control units comprise photocells, or sensors, to detect the presence of a tile (or a tile) in correspondence of the print head, to enable or disable the output of an ink jet from the nozzles of the head. 10. Apparatus (10) according to claim 9, wherein a signal emitted by the photocells, or by the sensors, at the time of the arrival of the tile (or the tile) also determines the location of the pointer in correspondence of the line a Print with that inkjet printhead.