ES2881532T3 - A device and a method for ink jet printing on surfaces having reliefs or recesses - Google Patents

Abstract

A method for ink jet printing on ceramic tiles provided with recesses and/or reliefs, comprising: providing an ink jet printing device (20) having at least one group of print heads (21, 22, 23) that have inclinations that can be arranged independently of one another, where each head (21, 22, 23) comprises a plurality of ink ejector nozzles (25), aligned to form a set of nozzles (26), one being direction of the ink jets (27) emitted from the nozzles (25) substantially perpendicular to the set of nozzles (26); subjecting the ceramic tiles (B) having a surface (10) to be decorated that has reliefs and/or recesses to the striking action of the printing device (20); move the surface (10) of the ceramic tiles (B) to be printed with respect to the printing device (20), in a forward direction (A) that is perpendicular to the direction of the nozzle assemblies (26), within the printing field of the device (20), said surface (10) having the dimension transverse to the direction of advance (A); assign to each head (21, 22, 23) a respective printing band (F21, F22, F23) on the surface (10), so that together the heads of the group cover the entire transverse dimension of the surface (10) to print; arrange the heads (21, 22, 23) with said inclinations so that, in at least one of them, the distances between the ejector nozzles (25) and the points of the surface (10) to be impacted are different, and the respective sets of nozzles (26) are oriented practically parallel to a center line of inclination of a transverse profile of the portion (10) of the surface subjected to the printing band (F21, F22, F23) of the head.

Description

DESCRIPTION

A device and a method for ink jet printing on surfaces having reliefs or recesses

Technical field

The present invention relates to a device and a method for ink jet printing on ceramic tiles that have reliefs or recesses, in particular on surfaces to be decorated that have at least one section that has a transverse section in the shape of a geometric arc, substantially an arc of circumference, ellipse, or parabola.

More generally, the invention is usually applied in the decoration of exposed surfaces which have reliefs or recesses that can even be of considerable thickness or depth.

Background of the technique

Ink jet devices have been in use for some time, including in the ceramic tile sector, comprising one or more print heads; These heads are formed by a plurality of nozzles, located along at least one line, usually a straight line, the nozzles of which emit controlled jets of ink microdroplets, collected from a well or a cartridge. Document US2007095218 discloses such an inkjet device.

The print head is controlled by an electronic processor which imparts a succession of printing commands to the various nozzles, according to the image to be obtained and the relative position between the head and the surface to be printed, either by activating or leaving inactive. the nozzles. During the printing process, the heads each have at least one series of nozzles that are aligned according to a line of action and the surface to be printed on is translated under the print heads, for example by positioning the surface on a conveyor belt, where it has a position perpendicular to the direction of the jets, while advancing along a direction transverse with respect to the direction of alignment of the nozzles, staying within the plane of position; the surface to be printed on passes completely into the field of action of the nozzles so that the printing device can print on the entire usable surface.

In the case of color printing, various print heads are used successively, each for a specific color of which the desired final image is made up, and the printing procedure described above is repeated using the various heads available for printing in color, each head is controlled autonomously by the software program according to the final image to be obtained.

A technical problem arises in a case in which the surface to be printed has reliefs or recesses. If the reliefs or recesses are of considerable thickness or depth, the ink droplets hit the surface with inclinations that are significantly different from point to point and consequently produce different effects in terms of extension, shape and intensity of the label. produced on the surface by microdroplet, with final results that are mostly disappointing and unacceptable in terms of quality. This technical problem is obviated by the ink jet recording device and method according to the appended claims.

Disclosure of the invention

This problem is obviated with the device and method for ink jet printing of the claims.

Brief description of the drawings

The invention is described in detail below, with the aid of the attached figures of the drawings which illustrate a non-exclusive embodiment by way of example, and in which:

Figure 1 is a schematic section of the surface to be printed and the print heads, in a vertical and transverse plane (perpendicular to the direction A of the reciprocal movement between the surface and the device);

^Figure 2 ^{is a schematic plan view from above of Figure} 1 ^;

Figure 3 is a detailed top plan view of a printing device having four groups ^{of heads, such as the device of Figure} 1 ^;

Figure 4 is a perspective view of the lower part of the device of Figure 3.

Best Mode of Carrying Out the Invention

The method of the invention is for printing on tile surfaces 10 with reliefs or recesses.

The method is typically suitable for printing on surfaces 10 that have a transverse profile kept constant by moving the section in the direction of advance A, parallel to the relative movement between the surface and the device; a classic case is the surface of an object obtained by extrusion.

The invention is typically to decorate the visible surface of ceramic tiles known as structured, that is, provided with recesses or reliefs, having at least one section with a transverse profile in a geometric arc, preferably an arc of circumference, ellipse or parable.

With reference to the figures of the drawings, 10 denotes in its entirety a surface to be printed on, for example, a tile B, on which the printing device of the invention acts.

The illustrated surface 10 has, in cross section, as represented in FIG. 1, a first ^end point 10 a ^{and a second end point} 10 ^{b: the surface to be printed is the area delimited between points} 10 a ^and 10 ^b. The surface comprises a substantially flat area 11 and a relief area 12, the cross section of which ^{has a geometric arc; Between the flat area} 11 ^{and the relief area} 12 ^{there is a concave area, with respect to a straight line (not shown in the figures) that passes through point} 10 a ^{and tangential to the relief area} 12 ^. Obviously, the invention is applicable to operate on surfaces with a shape other than that described hereinbefore, that is, that have a non-constant cross section, which presents reliefs and / or recesses of a relevant entity.

The method comprises the use of an ink jet printing device 20 that has at least one group of printing heads 21, 22, 23, independent of each other, where each head comprises a plurality of ejector nozzles 25 capable of emitting jets 27 of ink microdroplets, the nozzles of which are aligned to form a line of action 26. The direction of the ink jets 27 emitted by the nozzles 25 is perpendicular to the line of action 26, and the lines of action 26 of the various heads 21, 22, 23 are arranged, ^{according to the plan view (see figure} 2 ^{) parallel to each other and staggered to each other so as to present} end sections that are parallel, two by two and flanked each other.

In the example of Figure 2, the head 22 is located in an intermediate transverse position between the heads 21 and 23; head 21 has an end portion 21b that is parallel and flanked by an end portion 22a of head 22; the end portion 21b has a second end portion 22b, parallel and flanked by an end portion 23a of the head 23.

A displacement means is provided for displacing the surface to be printed 10, adapted to move the surface relative to the printing device 20, in a direction of longitudinal advance (A) (transverse with respect to the direction of the lines of action 26) , internally of the field of action of the device 20. For example, the means of movement is defined by a conveyor belt, with a horizontal conveyor belt 41, capable of moving the tile B (and therefore the surface 10 thereof ) in the field of action of the device 20.

The method comprises assigning to each head 21, 22, 23, a respective area of action by the jets 27 coming out of the head, on the surface 10, so that the group of heads 21, 22, 23 is of interest to the ^{entire population. transverse dimension of the surface to be printed} 10 ^.

In detail, as illustrated in Figures 1 and 2, the head 21 presents an action strip F21 that develops over an indefinite length in a longitudinal direction (a direction that is parallel to the direction of advance A ^{of the surface} 10 ^{with with respect to device} 20 ^{), the width of which (dimension in the transverse plane) concerns a part of the width (dimension in a transverse plane) of the surface} 10 ^{; similarly, the head} 22 ^has an action band F22 and the head 23 has an action band F23; the three action bands are ^{complementary to each other and together they concern the entire surface to be printed} 10 ^{, without reciprocal overlaps.}

In the respective action strip, each head emits micro-jets of ink 27 (indicated symbolically, with gray circles of a much larger size than in reality, in figure 2) on the action strip F21, F22, F23 of the same . The nozzles 25 that are active are indicated in Figure 2 by a small circle barred with an x, while the inactive nozzles 25 are indicated by a small empty circle.

Normally, the length of the action lines 26 of the heads is not fully utilized, to avoid overlapping between the nozzles in the final sections of the heads.

The method comprises arranging each head 21, 22, 23 with an inclination so that, in at least one of the heads, the distances between the ejector nozzles 25 and the points of the surface 10 hit by them are different: in other words , the length of the ink jets 27 are different from the head; furthermore, ^{the respective line of action 26 is oriented, in the transverse vertical plane (as illustrated in figure} 1 ^{), in a} way that is roughly parallel to the mean tilt line (R22, R23), with respect to the horizontal plane, of the profile that is transverse to the surface portion 10 subjected to the action band F21, F22, F23 of the head itself 21, 22, 23.

For example, as illustrated in figure 1:

^{the line of action 26 of the head} 21 ^{is arranged with a zero inclination angle as the respective fringe} of action F21 operates on a surface portion (zone 11) whose profile in the transverse plane is horizontal or more or less horizontal;

^{the line of action 26 of the head} 22 ^{on the other hand is inclined with respect to the horizontal line, parallel to a} straight line R22 (imaginary) whose inclination represents an average of the inclinations of the tangential lines (imaginary) to the profile of the surface 10 in the portion subjected to the action band F22 produced by the ^head 22 itself ^;

the line of action 26 of the head 23 is also inclined with respect to the horizontal line, parallel to a straight line R23 (imaginary) whose inclination represents an average of the inclinations of the (imaginary) lines tangential to the surface 10 in the part subjected to the action band F23 produced by the head 23 itself.

The surface section 12 having an arched profile section is shared between at least two ^{consecutive action strips (F} 22 ^{, F23).}

The described method allows printing, through an ink jet printing device, on surfaces, in particular ceramic tiles or other modular elements, that have reliefs or recesses that have respective elevations or depths that are relatively large, obtaining results that so far they have not been available.

This is because the ink jets 27 emitted by the heads 21, 22, 23 can strike the various ^{transverse portions of the surfaces} 10 ^{differently, each at optimal angles (i.e.} perpendicularly), or so much so.

Figures 3 and 4 illustrate an embodiment of the printing device 20 in a version comprising four groups G1, G2, G3 and G4 of heads 21, 22, 23, each group G having the characteristics described above ^{with reference to Figures} 1 ^and 2 ^{, in particular, to allow printing with four different colors.}

The device 20 presents a support frame 3 having a fixed horizontal plate 30 arranged substantially parallel to the upper surface of the conveyor belt 41. All the heads 21, 22, 23 of the four groups G are fixed to the surface of the plate 30.

Each group G is formed by heads 21, 22, 23 arranged reciprocally as illustrated with reference to Figures 1 and 2, i.e. briefly, with each head comprising a plurality of ejector nozzles 25 aligned to form a line of action 26, the direction of the ink jets 27 emitted by the nozzles 25 is perpendicular to the line of action 26, and the lines of action 26 of the heads are arranged, according to the plan view, parallel to each other and reciprocally staggered so that have final sections of two that are parallel and flanked to each other.

The heads 21, 22, 23 are fixed to the plate 30 in the openings of the plate 30 which allow the heads to present their nozzles 25 on the lower surface of the plate 30, oriented downwards.

The heads 21 of the four groups G are aligned with each other in a longitudinal direction (parallel to direction A) and are fixed to a portion 31 of the plate 30, which is fixed.

The heads 22 of the four groups G are aligned with each other in the horizontal and transverse directions and are attached to a movable portion 32 of the plate (this portion is indicated by a series of crossed, horizontal and vertical lines in Figure 3) which are separates from the fixed part 31; similarly, the heads 23 of the four groups G are aligned with each other in a horizontal and transverse direction and are fixed to a movable part 33 of the plate (this part is indicated by a series of crossed lines and inclined at 45 ° in Figure 3) which is separated from the fixed portion 31.

Portion 32 is restricted, by hinge pins 42, to fixed portion 31 so that it can oscillate about a horizontal and transverse axis of rotation (parallel to the direction of advance A) defined by pins 42; similarly, the portion 33 is constrained by hinge pins 43 to the fixed portion 31 so that it can oscillate about a horizontal and longitudinal axis of rotation (parallel to the direction of advance A) defined by the pins 43.

The inclination of the part 32 of the plate can be varied to arrange the four heads 22, located in the same part of the plate 32, each one with an inclination such that it respects the aforementioned criterion relative to the head 22 ^{of figure} 1 ^{, that is, with the respective line of action} 26 ^{oriented, in the transverse vertical plane (as illustrated in figure} 1 ^{) so that it is practically parallel to the midline of inclination, with respect to the} horizontal plane, of the transverse profile of the portion 10 of the surface subjected to the action band F22 of the head 22 itself.

The same occurs with the portion 33 of the plate, whose inclination can be varied to arrange the four heads 23, located in the same portion 33 of the plate 33, each one with an inclination that is such that the criteria mentioned above are respected in relation to the head 22.

The movement of the surface 10 with respect to the device 20 is such that it brings each cross section of the surface under the action of each group G of heads 21, 22, 23 in succession.

Obviously, many modifications of a practical nature can be made to the invention without leaving the scope of the inventive idea as claimed hereinafter.

Claims (5)

1. A method for ink jet printing on ceramic tiles provided with recesses and / or reliefs, comprising: ^{providing an ink jet} recording device (20 ^{) having at least one group of recording heads} (21, 22, 23) having inclinations that can be arranged independently of each other, where each head (21, 22, 23) comprises a plurality of ink ejector nozzles (25), aligned to form a set of nozzles (26), a direction of the ink jets (27) emitted from the nozzles (25) being substantially perpendicular to the set of nozzles ( 26); subjecting the ceramic tiles (B) having a surface (10) to be decorated presenting reliefs and / or recesses to the ^{striking action of the printing device (} 20 ^); move the surface (10) of the ceramic tiles (B) to be printed with respect to the printing device (20), in an advance direction (A) that is perpendicular to the direction of the nozzle sets (26), within the printing field ^{of the device (} 20 ^{), said surface (} 10 ^{) having the dimension transverse to the direction of advance} (A); assign to each head (21, 22, 23) a respective printing band (F21, F22, F23) on the surface (10), ^{so that together the heads of the group cover the entire transverse dimension of the surface (} 10 ^{) to} print; arrange the heads (21, 22, 23) with said inclinations so that, in at least one of them, the distances between the ejector nozzles (25) and the points of the surface (10) to be impacted are different, and the respective sets of nozzles (26) are oriented practically parallel to a median line of inclination of a transverse profile of the portion (10) of the surface subjected to the printing band (F21, F22, F23) of the head. The method of claim 1, characterized in that the ceramic tiles that are to be subjected ^{to the striking action of the printing device (} 20 ^{) have surfaces (} 10 ^{) to be decorated that have at least one section} with a profile that is transverse and in a geometric arc, preferably an arc of circumference, ellipse or parabola. The method of claim 2, wherein the section with a profile arc is shared between at least two printing bands (F21, F22, F23) that are consecutive. The method of claim 1, wherein a mean slope (R22, R23) of the printing web (F21, F22, F23) is identified by a line joining two end points of the cross- ^{sectional profile of the surface (} 10 ^). 5. An ink jet printing device for carrying out the method of the preceding claims and for operating on ceramic tiles (B) having surfaces (10) having reliefs and / or recesses, the ceramic tiles (B) being activated to translate with respect to the device along a longitudinal advance direction (A), comprising: at least one group (G1, G2, G3, G4) of print heads (21, 22, 23), having inclinations arranged independent of each other, in which each head (21, 22, 23) comprises a plurality of nozzles (25) to eject ink, aligned to form a respective set of nozzles (26) for each head (21, 22, 23), so that a direction of the ink jets (27) emitted by said nozzles (25 ) is perpendicular to said sets of nozzles (26) which is transverse with respect to said longitudinal advance direction (A) and said sets of nozzles (26) of said heads being arranged, according to a plan view, parallel to each other and staggered to each other; each print head (21, 22, 23) having a respective print band (F21, F22, F23) on the surface (10) to be printed, so that together the print heads (21, 22, 23) of the group cover the entire ^{transverse dimension of said surface (} 10 ^{) to be printed, wherein said printing bands (F} 21 ^{, F} 22 ^{, F23) are complementary to each other and involve the entire transverse dimension of the surface to be printed (} 10 ^{) without reciprocal overlap,} the heads (21, 22, 23) are oriented with said inclinations which are such that in at least one of said heads (21, 22, 23) the distance between the ejector nozzles (25) from the points of the surface ( 10) beaten this way are different, and the respective sets of nozzles (26) are oriented practically parallel to the midline of inclination of the surface (10) subjected to the printing band (F21, F22, F23) of the head, characterized in that the heads (21, 22, 23) can be oriented with a variable inclination according to a respective axis of rotation that is parallel to the direction of advance (A) of the surface (10) with respect to the device, so that the respective sets of nozzles (26) of Each of said heads (21, 22, 23) can be oriented practically parallel to the midline of inclination of the surface (10) that can be subjected to the printing band (F21, F22, F23) of said head (21, 22, 23).