ES2861950T3 - Print head for decorating ceramic substrates - Google Patents

Abstract

Print head (20) comprising: a camera (52); a piezoelectric actuator element (64) disposed outside the chamber (52); a plug (68, 76) comprising an elongated connecting rod (68), secured with respect to the piezoelectric actuator element (64), and a valve head (76), secured with respect to the connecting rod (68) at a distal end ( 89) thereof, wherein the piezoelectric actuator element (64) is coupled to the shutter (68, 76); a compartment (63) for retaining the piezoelectric actuator element (64); wherein: the piezoelectric actuator element (64), the elongated connecting rod (68), and the valve head (76) deflect in the same first direction (Y) from a first non-deflected position to a second deflected position; the elongated connecting rod (68) and the valve head (76) deflect within the chamber (52) in the first direction (Y); a portion of the shutter (68, 76) being disposed within the chamber (52) and being able to be used to move from a first position within the chamber (52) to a second position within the chamber (52) during actuation of the element piezoelectric actuator (64); a separating element (53) for separating the chamber (52) and the compartment (63), the separating element (53) consisting of a flexible part; the separating element (53) being coupled with the shutter (68, 76) and being able to be used to provide movement of the shutter (68, 76) disposed within the chamber (52) during actuation of the actuator element in the compartment (63 ), wherein two elastomeric retention elements (86) are used to hold the piezoelectric actuator element (64) in place with respect to the chamber (52); wherein said valve head is formed as a cylindrical structure having a closed end (78) and an open end (80); wherein said print head (20) also comprises a diaphragm (88) and wherein said open end (80) is formed to receive the distal end of connecting rod (68) and is also formed to engage said diaphragm ( 88) to seal the connecting rod (68) inside the chamber (52).

Description

DESCRIPTION

Print head for decorating ceramic substrates

The present invention relates to inkjet print heads and, in particular, but not exclusively, relates to improvements in print heads for decorating ceramic substrates.

The decoration of ceramic substrates, for example ceramic tiles, involves depositing a glaze or slip on the surface of the tile. Enamel generally comprises an aqueous or solvent-based ceramic solution or suspension, or a suspension within a solution, composed of a liquid part that has a quantity of mineral particles / powders dispersed in it, so that the specific formulation of the enamel It depends on the requirements of the end user.

Common techniques such as screen printing, rotary printing, flexography and curtain printing or curtain hood deposition, are used to deposit the glaze on the surface of the tile. However, it is difficult to achieve controlled local effects on the tile using the techniques mentioned above; Furthermore, it is difficult and time-consuming to change from one design to another. Today's decorative and textural effects can be achieved using, for example, gravure printing, which involves rollers with a textured elastomeric coating, which is based on printing on a virtually smooth surface. However, rollers are expensive, require storage space, and cannot be used for a specific design alone. Also, tiles are never flat enough to allow easy control of roller pressure for even contact between tile and roller, essential for a good finish that does not break the tile.

Inkjet printing represents an attractive technique for depositing enamel that addresses the above problems. In a digital ink jet print head, the enamel in a chamber of the print head is expelled from the print head through a nozzle, by an actuator arranged inside the print head. In addition to glaze, digital slip printing, typically an aqueous suspension of clay, enables the printing of textural effects that would otherwise only be possible during the tile pressing stage.

However, conventional ink jet printers use nozzle diameters 0 <50 pm, which are not suitable for enamel or engobe, which are powder suspensions or suspensions within solutions, since these usually have particle sizes of 10 s microns, as well as high volume weights that far exceed 100g per square meter, and more commonly require up to 1kg per square meter to be deposited. Document EP1972450B discloses an example of a conventional print head 1 used to print enamel, as shown in section in Figure 1. The print head 1 comprises a fluid chamber 2, having a fluid inlet (not shown ) and a fluid outlet (not shown), whereby enamel 4 flows through chamber 2 from inlet to outlet under a pressure of, for example, 1 bar.

The print head 1 comprises an actuator 6 in the form of a piezoelectric rod having a shutter 7 coupled thereto and disposed within the chamber 2, while the print head 1 further comprises a nozzle portion 8 which has a surface 5 within of chamber 2 and having at least one through-hole nozzle 9 therein that provides a flow path from inside chamber 2 to a substrate 10 through nozzle 9.

A plug is any mechanical element that can be used to couple it with the nozzle portion 8 in order to provide a mechanical seal at the entrance to the nozzle 9, thus preventing / reducing the flow of enamel into the nozzle 9.

Such a shutter can be part of a shutter assembly comprising a shutter.

As plug 7 engages actuator 6, it moves in the same deflection direction as actuator 6, and is configured to engage surface 5 to lock nozzle 9 when actuator 6 is in a non-deflected position, and to disengage from surface 5 thus uncovering nozzle 9, when the actuator is in a biased position.

An electronic control unit (not shown) is used to drive the actuator with a certain voltage waveform, for example to drive the actuator 6 so that it is oscillatingly deviated at a certain frequency, for example 1 kHz . By oscillating the actuator 6 it is possible to control the expulsion of the fluid through the nozzle 9 in the form of droplets.

The chamber is provided with one or more gaskets 12, for example a sealing gasket, to prevent enamel from leaving the chamber 2 at any point other than the nozzle 9, and through the fluid inlet and outlet.

A problem with the conventional print head 1 is that the enamel or slip, over time, damages the actuating element 6 arranged inside the chamber 2, the shutter 7, the surface 5 and / or the gasket or gaskets 12, reducing thus significantly the useful life of the print head 1 when leaking from the chamber and / or creating pressure problems within the chamber.

Document EP0993951 discloses a solution for separating the actuator from the ink fluid. The solution refers to a print head having a specific shutter different from the shutter of the print head according to the present invention.

A further problem with conventional print heads is that they are generally only compatible with solvent-based enamels, which are expensive and can be highly toxic, requiring an oven to burn the solvent after deposition. However, the use of water-based enamels on conventional print heads clogs the nozzles and causes more wear on the internal components of the print head.

Therefore, it would be advantageous to provide an improved print head that overcomes the above-mentioned disadvantages.

In a first aspect, there is provided a recording head according to claim 1.

Preferably, the actuator element is mechanically coupled to the shutter, wherein the fluid chamber comprises at least one nozzle, and wherein the shutter can be used to open or close the inlet of the at least one nozzle during actuation of the actuator element. .

Preferably, the plug is part of a plug assembly.

In a second aspect, there is provided a printer according to claim 6 and an ink jet printing method according to claim 7.

Figure 1 shows in section an example of a conventional prior art print head used to print glaze;

Figure 2a shows in section a recording head according to an unclaimed example, whereby enamel is prevented from flowing through the nozzle;

Figure 2b shows in section the print head of Figure 2a, whereby enamel is not prevented from flowing through the nozzle;

Figure 3 shows in graphical form, an exemplary waveform of the voltage applied to an actuator of Figures 2a and 2b;

Figure 4 shows in a perspective view a cross section of a recording head of the present invention;

Fig. 5a shows a printer system, having a print head formed by a plurality of individual print heads according to a third embodiment of the present invention; and

Figure 5b shows a printer system, having a plurality of nozzles formed within a single fluid chamber.

Figure 2a shows in section a print head 20, whereby enamel is prevented from flowing through a nozzle 29 of a nozzle part 28, while Figure 2b shows in section the print head 20 by which no enamel is prevented from flowing through nozzle 29.

Although the operation of the print head is described below using enamel, it will be appreciated that any suitable fluid can be used depending on the specific application, for example, methyl ethyl ketone or acetone based ink for printing on cardboard / paper / food packaging. , or polymer / metallic based ink for 3D printing, or slip.

The enamel itself can contain pigment to give color after firing and have other additives such as clay to provide different finishes such as glossy, matte, opaque finishes that can be combined on the same surface, as well as special effects such as metallic tones. and luster. Textural or relief structures can be provided by printing a predominantly slip-containing solution. An exemplary digital enamel composition is described in ES2386267. The particle sizes within the enamel are generally in the range of 0.1 ± 50 µm, and preferably up to 30 µm, but will vary depending on the specific formulation.

Alternatively, slip can be used on the print head, whereby slip is used to prime ceramic tiles, in order to make the tile permeable to water after pressing; or to print embossed features on the tile for wood and stone effects.

The slip is a suspension of clay particles, while the glaze generally comprises a suspension of water-based or solvent-based glass frit, or a suspension within a solution formed by a liquid part having a quantity of mineral particles / powders. dispersed in it, so the specific formulation of the enamel depends on the requirements of the end user. A matte nail polish can also contain a slip.

The print head body 20 is formed of a tough material that has mechanical and chemical resistance to the specific fluids used for a particular print application. A suitable material is polyether ether ketone (PEEK), for example Victrex PEEK 150GL30, which has mechanical and chemical strength properties suitable for organic and aqueous fluids, including water-based enamel.

The print head 20 comprises a fluid chamber 22, which has a fluid inlet (not shown) and a fluid outlet (not shown), whereby enamel 24 flows through chamber 22 from the inlet to the outlet under a substantially constant pressure above atmospheric pressure, for example 1 bar. The inlet and outlets are fluidly connected to a closed loop enamel supply system. The closed loop supply system (CCSS) has a supply channel to supply the enamel to the inlets and outlets, a discharge channel and means to move and pressurize the enamel in the conduit, for example pumps, whereby the CCSS is controlled, for example, by an electronic ink supply system, as is known in the art. The printhead 20 further comprises a flexible parting component 26, for example, formed of 70 Shore A nitrile butadiene rubber (NBR), which can be used to seal an upper portion of the chamber 22, thereby providing a sealed gap between the chamber 22 and a compartment 23 of the print head 20. The compartment 23 is provided with an actuator 30 located therein.

The separating element 26 is held in place and provides sealing functionality by formations 27 formed therein that form a mechanical coupling with reciprocal formations formed on the print head 20, thus holding the sealing means in place. A sealant and / or adhesive can also be used to ensure that the flexible spacer 26 remains in place and / or to improve the seal at the interface 33 between the flexible spacer 26 and the printhead 20.

In the present embodiment, the spacer member 26 is formed of an elastic material, although it is not limited to being elastic only.

Actuator 30 can be used to deviate from a first position, as shown in figure 2a, whereby actuator 30 does not deviate to a second position, as shown in figure 2b, so actuator 30 is it deflects in a direction away from the nozzle portion 28 (in the y-plane) by applying an electric field to it (eg, a voltage across actuator electrodes). Actuator retainers 39 are used to hold the actuator in place relative to chamber 22 so that deflection of actuator 30 relative to chamber 22 is maximized.

In a preferred non-claimed example, the actuator 30 is formed of a piezoelectric element that is formed from, for example, lead zirconate titanate (PZT) but can be formed from barium titanate, potassium sodium niobate (KNN), and / or or sodium bismuth titanate (BNT) or any suitable material.

The functionality of piezoelectric elements is well known, according to which piezoelectric elements are deflected by applying an electric field to them, for example by applying a voltage differential across the layer or layers of the element.

In a preferred non-claimed example, actuator 30 is a piezoelectric element, in the form of a substantially flat rectangular plate comprising one or more piezoelectric layers, configured to function as a bimorph, wherein actuation and contraction of the ceramic element creates a bending moment that transforms a transverse change in length into a large bending displacement perpendicular to the contraction. Such functionality is achieved using known piezoelectric elements, such as, for example, a Picma® piezoelectric flex actuator (eg, PL112-PL140), which allows full differential control of displacement. It will be appreciated that the shape of the element is not limited to a rectangular plate, but can be square, disk-shaped, or any other suitable polygonal shape.

The actuator 30 has at least two associated electrodes or terminals for each piezoelectric layer, wherein the electrodes are configured to allow the supply of a controllable electric field to the actuator 30. In a preferred embodiment, a deflection is provided in the bending mode from about 30 pm.

However, the amount of deviation required will depend on the specific application, but generally the deviation will be on the order of 600 pm. Preferably, elements that can deviate from at least 20 pm to 60 pm will be used. Such a deviation can be obtained by applying a suitable voltage differential across the layer or layers of the piezoelectric element, for example up to about 600 V, but preferably they will be applied voltage differentials of up to between 20 V and 60 V between the layer or layers of the piezoelectric element, and preferably up to 30V.

It will also be appreciated that, although the actuator 30 can be used to deflect in a direction away from the nozzle portion 28 by applying an electric field to it, that is, in the Y plane, as shown by arrow 40, in embodiments Alternatively, the actuator 30 may be arranged to deflect in a direction toward the nozzle portion 28 by applying an electric field to it.

A plug assembly 31 is attached to the actuator 30 using a suitable adhesive that will not degrade in the presence of enamel, for example Loctite 438. The plug assembly 31 can be used to engage the nozzle portion 28, in order to open / close the inlet to a nozzle 29 formed therein.

The shutter assembly 31 comprises a connecting element, in which, in the present embodiment, the connecting element is a connecting rod 23, which is secured to the actuator 30.

It will be apparent to a person skilled in the art that the connecting element can take any suitable form for connecting a shutter assembly to the actuator.

Connecting rod 32 protrudes through flexible spacer component 26 into chamber 22, at the same time forming a seal between flexible spacer component 26 and seal assembly 31, thereby maintaining the seal between chamber 22 and compartment 23. connecting rod 32 is manufactured using a material with mechanical and chemical properties resistant to enamel or any other fluid used in the particular printing applications required by a user, for example, polyetherimide (PEI) such as Ultem 1000, or polyether ether ketone (PEEK) , etc.

In general, the nozzle portion 28 refers to a surface that has a nozzle 29 formed thereon. The nozzle portion 28 is formed of any suitable material, for example PEEK (KETRON), PEI, stainless steel (LS316) or silicon, whereby the nozzle 29 is formed by a suitable manufacturing technique, for example by electrical micro discharge machining (EDM) / laser machining / chemical engraving etc.

In the following non-claimed preferred examples, the nozzle has a diameter substantially equal to 400 µm. When enamel or slip printed, the nozzle preferably has a diameter between 100 pm and 600 pm, and substantially between 375 pm and 425 pm, and preferably the diameter is substantially 400 pm to ensure that the enamel particles do not block. the mouthpiece.

The nozzle portion 28 may be integrally formed with the chamber 22 during the manufacture of the chamber 22, or it may be a separate element that is mounted in the chamber 22 during the manufacture of the print head 1 and secured in place. using a suitable adhesive, eg Loctite 438.

In a preferred embodiment, distal end 35 of connecting rod 32 is inserted into a valve head 36 within chamber 22, wherein valve head 36 is formed to engage the substantially flat surface of nozzle portion 28 when the actuator 30 is in the first position. With the actuator in the first position, the valve head 36 engages in an area surrounding the nozzle inlet 29 of the nozzle portion 28 so that there is no path for fluid to flow from the chamber 22 to the nozzle 29.

It will be appreciated that, to close the inlet to the nozzle, the valve head 36 engages with the nozzle portion 28. Therefore, to reduce wear on the valve head 36, the valve head 36 is formed of a durable material., p. eg NBR 70 Shore A or grade 5 titanium, which can resist repeated exposure to cavitation and abrasion caused by actuation towards or against the nozzle portion 28. Similar aspects are also taken into account when selecting the material used for the nozzle portion 28, which may comprise a hard component in the form of a valve seat insert made of titanium to achieve good durability.

In alternative non-claimed examples, valve head 36 may not be present and connecting rod 32 or spacer 26 may be adapted to engage the surface surrounding the area of the inlet of nozzle 29 to prevent / restrict fluid flow. from chamber 22 when the actuator is in the first position.

The provision of a suitable voltage differential across the piezoelectric actuator 30 causes the actuator 30 to deflect to the second position, thus causing the plug assembly 31 attached to the actuator 30 and the spacer component 26 attached to it to move in the same direction. deflection direction of the actuator 30, such that the valve head 36 disengages from the surface surrounding the area of the inlet of the nozzle 29, thereby forming a path such that the enamel flows from the chamber 22 into the nozzle 29, that is, thus filling nozzle 29.

The subsequent elimination of the stress differential across the actuator 30 returns the actuator 30 to the first position from the second position in the compartment 23, which in turn causes the valve head 36 to re-engage the surface it faces. surrounds the area of the inlet of the nozzle 29 into the chamber 22. During the return of the actuator 30 to the first position, the downward movement of the valve head 36 relative to the valve assembly Nozzle 29 prevents fluid flow into nozzle 29 and ejects enamel from nozzle 29 onto a substrate 38 disposed below an outlet of nozzle 29 on the outside of printhead 20.

An electronic control unit (not shown) is used to provide actuator 30 with a voltage differential waveform, for example, to drive the actuator so that it is oscillatingly deviated at a certain frequency, for example, 1 kHz . By operating the actuator 30 in this way, it is possible to control the expulsion of the fluid from the nozzle 29 in the form of droplets.

It will be appreciated that the flexible spacer component 26 allows deflection of the actuator 30 in the compartment 23 to effect movement of the valve head 36 within the chamber 22 so that drops of enamel can be deposited on the substrate 38 through of the nozzle 29 in a controlled manner, without risk of the actuator 30 coming into contact with the enamel.

Figure 3 graphically shows an exemplary voltage differential waveform across piezoelectric actuator 30, according to which the element is arranged to deflect upon application of the voltage differential. At time 90, the voltage differential (AV) across actuator 30 increases from V0 (eg, 0 V) to V1 (eg, 30 V). During this time, the actuator 30 will deform and deviate (for example, 30 pm) from the first position, as shown in figure 2a, to the second position, as shown in figure 2b, resulting in a gap of the valve head 36 from the nozzle portion 28.

During the period 92, the voltage differential is maintained in the piezoelectric actuator 30, thus keeping the actuator in the second position, so that enamel enters the nozzle 29, thus the time 92 in which the differential of Voltage across actuator 30 is proportional to the desired ink drop volume entering nozzle 29 and, therefore, printed drop.

At time 94, the voltage differential across actuator 30 drops to V0 and actuator 30 returns to the first position, as shown in FIG. 2a.

During the return to the first position, the bottom surface 40 of the valve head 36 locks the nozzle 29 and the nozzle expels a drop onto the substrate 38 for the time 94.

For the present embodiment, the waveform shown in figure 3 is repeated at a frequency of 1 kHz, as long as it is necessary to expel drops through the nozzle. The drive frequency / time (90, 92, 94) can be increased or decreased as required by a user, for example, to increase or decrease the volume of the printed drop, or to increase the drop ejection frequency from the printhead. printing 20. When it is not necessary to print a drop, the differential is kept substantially at V0.

The print head 20 of the present invention has the advantage of being adjustable both mechanically and electronically, so that the print head 20 is flexible and versatile, and adaptable to various desired applications and to various ceramic glazes, for example, glazes with base. aqueous and solvent-based. It will also be appreciated that a variety of different inks with different fluid properties could be used by modifying various parameters of the print head 20, eg, actuator deflection, nozzle diameter, drive voltage, etc., as required. .

It will be appreciated that the values used for the above embodiments consider that the deviation of the piezoelectric elements is proportional to the variations in applied voltage / voltage differential, that is, a deviation of approximately 1 pm per 1 V differential, but, as As will be appreciated by the person skilled in the art, the ratio and the specific values used will vary depending on a number of factors including the material and the specific crystal structure / polish of the piezoelectric element and the geometry of the actuator device, e.g. length / width / height piezoelectric layers.

Furthermore, the relationship between deflection and applied electric field need not be linear.

Figure 4 shows in a perspective view a cross section of a printhead 50. The printhead 50 comprises a fluid chamber 52 having a flexible diaphragm-shaped separating component 53, a side wall 54, a wall upper 59 and a nozzle portion 56.

Side wall 54 comprises an enamel inlet 55 in fluid connection with an enamel collector (not shown), through which enamel enters chamber 52 from the collector, and an enamel outlet (not shown) at fluid connection to the manifold, through which fluid exits chamber 52 into the manifold.

The nozzle portion 56 is formed of KETRON®PEEK 100 NATURAL and is arranged to fit tightly into the chamber housing 52. In the nozzle portion 56 there is provided a nozzle 60 with a diameter 0 of about 400 pm. Nozzle 60 provides a fluid path from chamber 52 to atmosphere 51.

It will be appreciated that the specific diameter 0 of the nozzle is chosen depending, for example, on the specific fluid properties and the desired drop volume range.

However, depending on the specific application and / or the enamel or slip used, the diameter may be in the range 80 jm - 1000 | jm, whereas for applications using ink solutions, for example MEK-based ink or of acetone, the diameter may be in a much smaller range, for example on the order of 10-60 µm. In the present embodiment, the diaphragm 53 is formed as an annular structure of NBR 60 Shore A and is arranged to seal the upper wall of chamber 52 of an actuator compartment 63, having a piezoelectric actuator 64 disposed therein. Diaphragm 53 comprises at least one formation 62 formed around diaphragm 52 and mating with at least one formation 65 provided within chamber 52.

During assembly, an adhesive, for example, Loctite 438, is provided around formation 62, and when the diaphragm is inserted into chamber 52, formation 62 engages with formation 65, and the adhesive holds diaphragm 53 in place. position relative to chamber 52, thus providing a sealing functionality between chamber 52 and compartment 63. Diaphragm 53 is located within a central opening of top wall 59. Diaphragm 53 is further provided with a central opening 66 through which an elongated connecting rod 68 is inserted, formed, for example, of Ultem 1000. A formation 70 along the inside diameter of the central opening 66, such as a lip, which may comprise a recess or several recesses or a projection or several projections, engages the connecting rod 68, which may have features suitable to receive the recess or recesses or the projection or projections of the arrangement 70, to seal the opening 66 so that enamel does not drip from the chamber 52 to compartment 63. The formation can be secured with respect to elongated rod 68 using, for example, Loctite 438.

A first end of elongated connecting rod 68 is secured to actuator 64 using a suitable adhesive, eg, Loctite 438.

In the present embodiment, the valve head 76 is formed as a cylindrical structure having a closed end 78 and an open end 80, wherein the open end 80 is formed to receive the distal end of the elongated connecting rod 68.

The distal end of connecting rod 68 is inserted into valve head 76 and secured relative thereto using a suitable adhesive, for example, Loctite 438. Valve head 76 is formed of a material with high mechanical resistance to wear, for example NBR 70 Shore A or grade 5 titanium, although the use of a deformable material for valve head 76 such as NBR allows for reduced contact energy as valve head 76 will deform to correct alignment not flat between the valve head and the valve seat, so that the total impact energy is reduced.

The open end 80 of the valve head 76 is also formed to mate with a diaphragm 88, for example, an elastomeric O-ring to seal the connecting rod 68 from inside the chamber 52 and to ensure that no enamel drips from the chamber 52. to compartment 63.

Furthermore, in the present embodiment, a valve seat 82 is provided on top of nozzle portion 56 around the inlet to nozzle 60 within chamber 52. Valve seat 82 is formed as an annular insert that engages with the nozzle portion 56, such that the upper surface of the valve seat 82 is flush with the inlet 83 to the nozzle 60.

The valve seat 82 can be formed of a material having good mechanical resistance to wear, for example, titanium Ti-6Al-4V grade 5.

In addition, to prevent valve seat 76 from shifting during operation, it can be secured relative to nozzle portion 56 using a suitable adhesive, for example, Loctite 438, or a friction fit, for example, a " click adjustment ”.

The bottom surface 79 of the valve head 76 can be used to mate with the valve seat 82 to seal / close the inlet 83 to the nozzle 60 so that when the valve head 76 is in contact with the seat valve 82, the inlet 83 to the nozzle 60 is sealed with respect to the chamber 52, so as to prevent / prevent enamel from flowing from the chamber 52 to the nozzle 60, whereas when there is no contact between the valve head 76 and valve seat 82, nozzle 60 is not sealed with respect to chamber 52, and enamel is not prevented / impeded from flowing from chamber 52 to nozzle 60.

In the printhead shown in FIG. 4, the bias of the actuator 64 occurs in the y-plane. Two elastomeric retainers 86 are used to hold actuator 64 in place with respect to chamber 52, so that the deflection of actuator 64 from chamber 52 is maximized, although the number of retention elements 86 is dependent on specific user requirements and is not limited to two, and its specific design is not limited to allow it to provide retention and allow maximum deflection.

The operation of the print head 50 is similar to the operation of the print head 20, and a waveform similar to that shown in Figure 3 can be applied to the actuator 64. When a voltage differential is applied across the actuator 64, actuator 64 deflects in the Y direction from a first undeviated position to a second deflected position.

Elongated connecting rod 68 is secured with respect to actuator 64, while valve head 76 is secured with respect to connecting rod 68 at a distal end 89 thereof, and thus elongated connecting rod 68 and valve head 76 they will deflect into chamber 52 in the same direction as actuator 64, which is outside the chamber in compartment 63.

Such functionality is obtained using the flexible diaphragm 53. Although the flexible spacer components 26 and 53 are described as substantially annular components in the above embodiments, it will be appreciated that the components are not limited to being annular and may have any suitable shape, for example , they can be square, rectangular, cylindrical, etc.

For example, the flexible partition component 26 of the first embodiment forms substantially the entire upper wall of the chamber 22. However, the partition element 26 may be an element that does not form substantially the entirety of a wall, but which, For example, it may simply be an O-ring or several rubber O-rings that can be inserted into an annular groove of a diametral opening in a non-flexible upper wall of chamber 22, through which connecting rod 32 is inserted, by what the O-ring (s) are in contact with the spacer 26.

In such an embodiment, the O-ring or gaskets allow the same functionality as described above, in that the connecting rod, coupled to a valve head in a chamber and to an actuator outside the chamber, is made to be deflect due to actuator deflection thus opening / closing accordingly the inlet to the nozzle, while the O-ring disposed in contact with the connecting rod provides sealing functionality between the fluid chamber and the actuator, while allowing movement from the valve head by effect of the actuator. It will be noted that when the actuator 64 is in the deflected position, enamel may flow from chamber 52 to nozzle 60. When actuator 64 subsequently returns to the first position, the inlet to nozzle 60 closes with respect to chamber 52, while enamel in nozzle 60 is ejected from the nozzle onto a substrate (not shown)

In the present embodiment, a deviation of up to 20-60 pm is desirable, so that a gap of approximately 20-60 pm is provided between the bottom surface of the valve head 76 and the valve seat 82 when the actuator is deflected. Such spacing is sufficient for the water-based glaze to pass from chamber 52 to nozzle 60. However, although actuator 64 deviates approximately 20-60 pm in the present embodiment, a deviation of approximately 30 pm is preferred, but it will be seen that a deviation of up to 600 pm could be used in operation, depending on the specific properties of the fluid to be printed and the specific application. For example, MEK-based inks are less viscous than enamel and have a smaller particle size distribution, so they will flow more easily through a smaller gap than enamel.

The print head comprises a fluid chamber, designed to contain enamel to be deposited on a substrate, whereby enamel is supplied to chamber 52 from a controlled enamel supply system through an inlet and outlet to a pressure of, for example, 0.1 bar - 10 bar, and preferably, in which the pressure is preferably between 0.5 and 1.5 bar, and preferably is substantially equal to 1 bar. An electronically controlled closed fluid supply system 103 as shown in Figures 5a and 5b, having, for example, pressure control equipment 104, valves 105, etc., allows a modification of the enamel circulation rate inside the duct; and maintains a constant flow of enamel around the system at a controlled pressure, eg 1 bar. The continuous and controlled flow of the enamel prevents sedimentation of the components contained in the suspension, a vital condition for the good operation of the head, and provides a constant pressure in the print head.

Figure 5a shows a printer 100 having a print head 101 made up of several specific print heads 102, arranged side by side. The print heads 102 are as described above in connection with Figures 2a, 2b and 4. The print heads 102 are arranged in order and can be angled with the direction of substrate travel, to adjust the distance between the nozzles 29 of adjacent print heads 102. It will also be appreciated that more or fewer print heads 102 can be added to the print head 101.

In such an arrangement, the individual heads can be designed to interconnect so as to provide continuous fluid flow through each head, by providing means connecting the fluid inlets and outlets of adjacent chambers, so that the same system closed-loop supply system can control fluid flow through all heads.

Alternatively, as shown in Figure 5b, a single print head 101 can also be achieved, having a plurality of nozzles 29 formed within a single chamber, whereby a single fluid chamber is provided with a plurality of shutters. (not shown) to open / close the nozzles 29, whereby each shutter can be controlled by corresponding actuators arranged outside the chamber, in the manner described above.

Furthermore, it will be appreciated that the individual print heads 102 are independently addressable, so that they can be controlled, for example, to provide droplets of various sizes from a single print pass, for example, by controlling the time in the print run. that the nozzles 29 are filled with enamel while the inlet to the nozzle 29 is open with respect to the chamber.

The print heads 101, 102 described above can be used advantageously not only for decoration, finishing and texturing of ceramic tiles, but due to the size of the glaze drops that can be obtained, they can also be used in glazing. of the entire surface.

With the use of such functionality as described above, the enamel can be ejected from the print head in a controlled manner. Unlike conventional print heads, water-based enamel can be deposited using print head 50.

Furthermore, it will also be appreciated that the adjustment of the print head parameters can influence the final graphic effect and improve the functionality and performance of the head. For example, at a printhead design level, the diameter of the nozzle 29 can be varied to provide access to different ranges of droplet volumes and ejection frequencies.

The benefits of depositing larger diameter particles and high solids fluids, such as enamel and slip, are obvious. Furthermore, the ability to add large 20-30 pm pigment particles to an enamel results in high color density and total flexibility to apply colored enamel digitally. This cannot be achieved with print heads that have a nozzle diameter <50 pm where the pigment diameter must be kept low. Furthermore, by controlling the closed-loop supply system 103, the pressure at which the enamel is kept circulating within the print head can be adjusted in a controlled manner according to the density and viscosity of the enamel. In this way, the amount of enamel coming out of the nozzle can be controlled, for example, while maintaining a constant drive waveform, the volume of the printed droplets will increase with increasing pressure in the system, while the volume drops will decrease as the pressure in the system decreases.

Such functionality can also be obtained by maintaining a constant pressure and modifying the drive waveform. For example, reducing the time during which the drive voltage V1 is applied to the actuator (time 92 in Figure 3) to open the inlet to the nozzle, results in a reduced drop volume because the amount of fluid flowing to the nozzle and is available for ejection is limited to the time the nozzle is filling.

In alternative non-claimed embodiments, it will also be appreciated that actuators other than piezoelectric actuators could be used to provide the same actuation functionality in order to effect droplet ejection, for example, electrostatic actuators, magnetic actuators, electrostrictive actuators, elements could easily be used. uni / bimorph thermals, solenoids, shape memory alloys etc., to provide the functionality described above while obtaining the desirable functionality, as will be apparent to the skilled person when reading the above memory.

Claims (7)

1. Print head (20) comprising: a chamber (52); a piezoelectric actuator element (64) disposed outside the chamber (52); a plug (68, 76) comprising an elongated connecting rod (68), secured with respect to the piezoelectric actuator element (64), and a valve head (76), secured with respect to the connecting rod (68) at a distal end ( 89) thereof, wherein the piezoelectric actuator element (64) is coupled to the shutter (68, 76); a compartment (63) for retaining the piezoelectric actuator element (64); wherein: the piezoelectric actuator element (64), the elongated connecting rod (68), and the valve head (76) deflect in the same first direction (Y) from a first non-deflected position to a second deflected position; the elongated connecting rod (68) and the valve head (76) deflect within the chamber (52) in the first direction (Y); a portion of the shutter (68, 76) being disposed within the chamber (52) and being able to be used to move from a first position within the chamber (52) to a second position within the chamber (52) during actuation of the element piezoelectric actuator (64); a separating element (53) for separating the chamber (52) and the compartment (63), the separating element (53) consisting of a flexible part; the separating element (53) being coupled with the shutter (68, 76) and being able to be used to provide movement of the shutter (68, 76) disposed within the chamber (52) during actuation of the actuator element in the compartment (63 ), wherein two elastomeric retention elements (86) are used to hold the piezoelectric actuator element (64) in place with respect to the chamber (52); wherein said valve head is formed as a cylindrical structure having a closed end (78) and an open end (80); wherein said print head (20) also comprises a diaphragm (88) and wherein said open end (80) is formed to receive the distal end of connecting rod (68) and is also formed to engage said diaphragm ( 88) to seal the connecting rod (68) inside the chamber (52). A print head according to any one of the preceding claims, wherein the actuator element is mechanically coupled to the shutter. A print head according to claim 1, wherein the fluid chamber comprises at least one nozzle. A print head according to claim 3, wherein the shutter can be used to partially open or close the inlet of the at least one nozzle during actuation of the actuator element. A print head according to claim 1, wherein the separating element (53) can be coupled with a part of the chamber (52). 6. Printer having a print head according to any one of claims 1 to 5. 7. An ink jet printing method, the method comprising using the printer according to claim 6 to deposit a fluid on the substrate.