A METHOD FOR THE DECORATIVE PRINTING OF SURFACES, PARTICULARLY OF TILES AND THE LIKE, AND A MACHINE OPERATING IN ACCORDANCE WITH THE METHOD

Abstract: A method and a machine for the decorative printing of surfaces, particularly of tiles and the like, are described and in which is provided for a colouring substance to be transferred onto a surface (2) to be decorated through a mask (21) on which the colouring substance is distributed, the colouring substance being transferred onto the surface (2) by the action of a jet of gas directed onto the mask (21).

Description: A method for the decorative printing of surfaces, particularly of tiles and the like, and a machine operating in accordance with the method. Technical field 5 The present invention relates to a method for the decorative printing of surfaces, particularly of tiles and the like, according to the preamble to main Claim 1. The invention also relates to a machine designed for implementing the method of the invention. 10 Background art Within the field of the decorative printing of surfaces, particularly of tiles and similar articles, so- called ink-jet methods, which allow printing to be performed on such surfaces without any contact between the surfaces 15. and the printing means, are known. One of these methods provides for the colouring substance, for example, an ink, to be sprayed in a jet through a nozzle onto the surface to be decorated, the jet stream being directed by means of a mask interposed between the nozzle and the surface. 0 In an application of this type, the pressurization of the colouring substances may be quite complex since, because these substances are generally constituted by suspensions of solids in liquids, they are not very homogeneous and tend to create deposits with possible undesired sedimentation. 5 Moreover, the jet of colouring substance expelled from the nozzles of the printing head is normally subject to dispersal before it reaches the surface to be decorated, which may compromise and reduce the quality of the printing of the figure or the decoration produced. 0 Disclosure of the invention The main object of the present invention is ' to provide a method for the decorative printing of surfaces, particularly of tiles, which is designed to overcome the limitations complained of with reference to the prior art mentioned. This object and others which will become clear from the following description are achieved by the invention by means of a method and a machine having the characteristics defined in detail in the appended claims. Best mode of carrying out the invention The characteristics and the advantages of the invention will become clearer from the detailed description of some preferred embodiments thereof, described by way of non- limiting example with reference to the appended drawings, in which: - Figure 1 is a partially-sectioned, schematic, side elevational view of a machine for decorative printing operating in accordance with the method of the invention, - Figure 2 is a perspective view of the machine of Figure 1, Figures 3 and 4 show details of the machine of the previous drawings, on an enlarged scale, - Figures 5 and 6 are partial perspective views of two respective variants of the same detail of the machine according to the invention, and - Figure 7 is a partially-sectioned, perspective view of a further variant according to the invention of a detail of the machine of the previous drawings. With reference to Figure 1, a machine for the decorative printing of a surface 2, for example, one of the opposed surfaces of a tile 3, in accordance with the method of the present invention, is generally indicated 1. The machine 1 has one or more conveyor means 4, for example, a belt conveyor, shown schematically and partially in Figure 1, for moving the tiles 3 or other similar products to be decorated, during the printing stages provided for. The machine 1 also comprises a printing head, generally indicated 5 and including a device 6 for emitting compressed air the function of which will become clearer from the following description, a dispenser 7 for distributing a colouring substance, for example, a paint or other coloured pigment, and a device 8 for recovering the excess colouring substance dispensed at the printing stage . The device 6 comprises a first chamber 9 which is in communication with a nozzle 10 having a substantially rectangular outlet cross-section 10a, elongate along a major axis (Figure 2) and facing the conveyor belt 4. The chamber 9 is in communication with a second chamber 11, which in turn is in communication with a third chamber 12 by means of through-holes 13 aligned along the longitudinal axis of the nozzle 10 (Figure 3) . The chamber 12 is supplied with compressed air which is transported through the holes 13 to the chambers 11 and 9 and from the latter to the expulsion nozzle 10. The function of the chambers 9 and 11 is to permit a homogeneous distribution of the compressed air along the entire longitudinal extent of the nozzle. The dispenser 7 has a structure substantially similar to that of the device 6 and differs therefrom mainly in that it preferably has a pair of chambers 14, 15. A main chamber 14 is supplied with the colouring substance under pressure and is in communication with an intermediate chamber 15 which in turn is connected, by means of holes 16, to a nozzle 17 which also has a rectangular cross-section, elongate along a major axis. The chamber 15 has the function of permitting partial expansion of the colouring substance prior to its expulsion through the nozzle 17. The recovery device 8 comprises a pair, of suction chambers 18, 19 which are in communication with one another, the chamber 19 opening into a duct 20 with a rectangular cross-section elongate in the " same longitudinal direction as the nozzle 17, and . having the function of recovering the excess colouring substance which is not deposited on the surface 2 during printing. Conveyor means, not shown, are provided for transporting the colouring substance recovered back to the dispenser 7. The machine according to the present invention also comprises a .mask in the form of a belt, indicated 21 and shown partially in the drawings, arranged in a closed loop around a set of guide rollers two of which, indicated 22a, 22b, are disposed on opposite sides of the device 6 of the printing head. The guide rollers define three corresponding portions 23a, 23b, 23c of the mask 21. The portion 23b is disposed between the rollers 22a, 22b and is interposed, in operation, between the nozzle 10 and the surface 2 of the tile to be decorated. The portion 23a which is defined upstream of the portion 23b, with reference to the direction of movement of the mask indicated by the arrow A of Figure 2, faces the nozzle 17 of the dispenser 7 and the portion 23c, which is defined downstream of the portion 23b, faces the device 8 for recovering colouring substance. The belt-like mask 21 is moved around the guide rollers 22a, 22b in a manner such that the portion 23b performs a translational movement relative to the device 6 and the portion 23a is similarly translated relative to the dispenser 7. The method of the invention provides for the jet of colouring substance emitted by the nozzle 17 of the dispenser 7 to strike the mask 21, during the. movement of the mask 21 relative to the printing head 5, in order to deposit the colouring substance on the belt-like mask 21, and for the jet of compressed air to strike the mask downstream of the dispenser, along the portion 23b, in order to direct and transfer the colouring substance onto the surface 2 of the tile in the manner described in greater detail in the following description, thus bringing about the printing of the preselected decorative figure . Preferably, the tile 3 is moved along by the belt conveyor means 4 with a translational movement synchronous with the movement of the mask 21 and the transfer of the colouring substance by means of the compressed-air jet takes place continuously, without interruption, whilst the tile 3 passes beneath the device 6 of the printing head. It is pointed out that the direction in which the colouring substance is emitted by the dispenser 7 is substantially perpendicular to the direction in which the compressed-air jet is emitted by the device 6 of the printing head. More specifically, the colouring substance is emitted by the nozzle 17 substantially in a horizontal plane, whereas the compressed-air jet extends vertically (Figure 1) . In a first embodiment, the method of the invention provides for the belt-like mask 21 to have a plurality of depressions or recesses 24 (Figure 5) formed on the side of the mask facing the dispenser 7 in order to house the colouring substance ejected by the nozzle 17. By virtue of the transverse extent of the outlet cross-section of the nozzle 17, the colouring substance is distributed over the entire width of the mask 21, filling exclusively the depressions, in accordance with an intaglio method. The arrangement of the depressions 24 is correlated with a respective preselected decorative figure to be printed on the surface 2 of the tile. In the region of the nozzle 10, the mask 21 is struck by the compressed-air jet and is urged resiliently into contact with the surface 2 so as to transfer the colouring substance onto the surface 2 of the tile by contact and to produce the preselected decorative figure by virtue of the synchronous movement of the mask 21 and of the surface 2. The excess colouring substance which is not transferred onto the tile 3 is recovered by suction by the recovery device 8 and is then transported back to the dispenser 7. A second embodiment of the invention provides for the mask 21 to have a plurality of through-holes 25 in a substantially matrix-like arrangement, some of the holes being blocked in accordance with a preselected configuration correlated with a corresponding decorative figure to be printed on the tile 3 (Figure 6) . The colouring substance is then distributed on the belt-like mask 21 by means of the dispenser 7 and the mask is subsequently struck by the compressed-air jet emitted through the nozzle 10. The colouring substance deposited in the region of the open holes 25 is discharged onto the surface 2 of the tile under the action of this compressed-air jet, thus bringing about the printing of the preselected decorative figure by virtue of the alternation of the open and closed holes 25 of the matrix . The elongate shape of the nozzle 10 allows the compressed-air jet to strike the mask 21 throughout its width and consequently to transfer the colouring substance over the entire extent of the tile 3 transverse its direction of movement . A third embodiment of the invention provides for the device 6 of the printing head to comprise a plurality of compressed-air nozzles 26 (Figure 7) each of which is constituted by a micro-duct 27 connected to the pressurization chamber 9 and having a shut-off member 28 so that the individual nozzle 26 can be shut off selectively in order to control its compressed-air flow. As in the previous embodiment, the belt-like mask 21 has . a matrix of through-holes 25 representative of a preselected decorative figure, all of the holes being open without exception and the figure being produced by the selective opening/closure of the individual nozzles 26, the respective shut-off members 28 of which are controlled, for example, by a piezoelectric control . Each of the embodiments described above also provides for the mask 21 to be replaceable by other masks each having an arrangement of depressions 24, of blocked and open holes 25, or of holes which are open without exception. In the first and second embodiments, this arrangement is representative of a corresponding decorative figure to be printed and, in the third embodiment, it is simply a means of conveying the colouring substance in an undefined manner since, in this embodiment, the decorative figure is defined which emit compressed air, entraining the corresponding spots of colouring substance in a jet onto the surface to be decorated. The invention thus achieves the objects set, affording many advantages over known solutions . In the first place, the method and the machine according to the invention enable better precision and quality of printing to be achieved by virtue of the use of compressed air as a printing medium suitable for transferring the colouring substance onto the surface to be decorated. A second advantage is that the present invention facilitates and improves the re-homogenization of the colouring substance by virtue of the fact that it provides for the colouring substance to be supplied, in the dispenser, in a substantially horizontal direction relative to the vertical direction in which the compressed-air jet is emitted, so as to reduce possible sedimentation and deposits of the solid components of the colouring substances. A further advantage which is noticeable in particular in the second and third embodiments of the invention described is that it is possible to decorate with ink-jets using an ink which is substantially a suspension of solids, which is difficult to achieve with conventional ink-jet printing techniques. Not the least advantage is that the method and the machine of the invention achieve faster printing speeds than can be achieved in known ink-jet printing machines.

Claims: CLAIMS 1. A method for the decorative printing of surfaces particularly of tiles and the like, in which a colouring substance is transferred onto a surface (2) to be decorated through a mask (21) on which the colouring substance is distributed, characterized in that the colouring substance is transferred onto the surface (2) by the action of a jet of gas directed onto the mask (21) . 2. A method according to Claim 1 in which the jet of gas is a compressed-air jet. 3. A method according to Claim 2 in which the surface (2) is moved relative to the air-jet with preselected rules of movement and the mask (21) is moved relative to the air- jet with preselected rules of movement correlated with the rules of movement of the surface (2) . . A method according to Claim 3 in which the surface (2) and the mask (21) are moved with synchronous rules of movement . 5. A method according to one or more of Claims 2 to 4 in which the mask (21) is urged resiliently, by the air-jet, into contact with the surface (2) to be decorated in order to transfer the colouring substance onto the surface (2) . 6. A method according to Claim 5, in which a plurality of depressions (24) are provided in the mask (21) for holding the colouring substance, the depressions (24) being provided in positions facing the surface (2) to be decorated and having an arrangement correlated with a respective, preselected decorative figure to be printed on the surface (2) . 7. A method according . to o e or more of Claims 2 to 4 in which the mask (21) is provided with a plurality of through-holes (25) the arrangement of which is correlated with a respective, preselected decorative figure to be printed on the surface (2) and the air-jet is directed through the holes (25) in order to spray the colouring substance onto the surface (2) to be decorated and to print the decorative figure on the surface (2) . 8. A method according to Claim 7 in which a plurality of compressed-air jets are directed onto the mask in order to transfer the colouring substance distributed on the mask (21) onto the surface (2) to be decorated, the air-jets being capable of being activated selectively in a manner correlated with a respective decorative figure to be printed on the surface (2) . 9. A method according to one or more of Claims 2 to 8 in which the expulsion of the colouring substance takes place in a direction substantially transverse the direction in which the compressed-air jet is emitted by the printing head. 10. A machine for the decorative printing of surfaces (2) , particularly of tiles and the like, comprising: - a printing head (5) and at least one mask (21) interposed between the printing head (5) and the surface to be decorated, as well as dispenser means (7) for distributing a colouring substance onto the mask (21) , characterized in that it comprises, in the printing head (5), gas-jet pressure means directed onto the mask (21) for directing and transferring the colouring substance distributed on the mask (21) onto the surface (2) to be decorated. 11. A machine according to Claim 10 in which the printing _head (5) comprises at least one nozzle (10) for emitting a compressed-air jet, the nozzle (10) having a discharge cross-section (10a) which is elongate along a major axis. 12. machine according to Claim 11 in which the printing head (5) comprises a first air-pressurization chamber (9) in communication with the nozzle. (10) and a second chamber (11) in communication with the first chamber (9) . 13. A machine according to Claim 12 in which a plurality of through-holes (13) are provided between the first chamber (9) and the second chamber (11) , the holes (13) being aligned parallel to the longitudinal axis of the nozzle (10) . 14. A machine according to one or more of Claims 11 to 13 in which the printing head (5) comprises a plurality of compressed-air outlet nozzles (26) which can be shut off selectively in order to direct respective compressed-air jets onto the mask (21) in a manner correlated with the decorative figure to be printed on the surface (2) . 15. A machine according to Claim 10 in which the means for dispensing the colouring substance comprise a pair of pressurization chambers (14, 15) in communication with one another, one of which is also in communication with a respective nozzle (17) . 16. A machine according to one or more of Claims 10 to 15 in which the mask (21) is formed as a closed loop. 17. A machine according to one or more of Claims 10 to 16 in which the mask (21) is in the form of a belt.

Inventors: CESTARI MAURO, CESTARI, MAURO
Applicants: ARKTYPE S R L, CESTARI MAURO, ARKTYPE S.R.L., CESTARI, MAURO
Application year: 2000
Main classification: B05B7
IPC codes: B05B7, B05B15