Inkjet head for enameling

Abstract

An inkjet head comprising: a dispensing unit (2) provided with: a main circulation duct (21) for circulating a ceramic enamel; two or more nozzles (3) placed in communication with the main duct (21) and distributed along a main direction (X); at least one shutter (4) activatable to close or release the nozzles (3); at least one actuator (5) arranged to activate the shutter (4); wherein the shutter (4) is movable between at least one closed configuration, in which it is able to close all the nozzles (3), and at least one open configuration, in which it releases at least one nozzle (3) to allow the ejection of the ceramic enamel.

Description

[0001] This invention relates to an inkjet head for glazing.

[0002] Specifically, the inkjet head according to the invention is advantageously configured to spread a uniform ceramic glaze layer on the ceramic tile.

[0003] In summary, the latest methods for producing ceramic tiles include the following operations.

[0004] Tiles are initially formed by pressing, starting with a soft layer of granular ceramic material. After pressing, the tiles undergo a glazing step, the purpose of which is to apply a uniform layer of ceramic glaze to the exposed surface of the tile. This uniform ceramic glaze of a predetermined color essentially forms the background for subsequent decorative applications, defining the color effect and final appearance of each tile. After the decoration is applied, the tiles undergo a firing process to permanently fix their shape and decoration.

[0005] Any useful but not necessary drying step can be included in the output of the press and between the glazing and decorative application steps.

[0006] As already mentioned, the glazing step involves applying a uniform layer of ceramic glaze to the exposed surface of the tile.

[0007] Currently, the glazing step is performed using a pneumatic distributor that sprays glaze from above along the direction of the underlying tile. Typically, the pneumatic distributor includes multiple pneumatic nozzles associated with a moving structure that move along predetermined paths configured such that the nozzles sweep across the entire exposed surface of the tile as a whole, ensuring complete glazing. The pneumatic distributor is usually contained within enclosed compartments through which the tiles are continuously passed by a conveyor plane with rollers or belts.

[0008] Current pneumatic distributors have many drawbacks.

[0009] First, the pneumatic distribution of the glaze means considerable waste. In fact, a continuous mist forms inside the compartment, and most of the mist is dispersed before reaching the tiles and must be recycled or disposed of.

[0010] Furthermore, pneumatic glaze distribution allows for the application of glaze layers of extremely limited thickness onto ceramic tiles. This is because the flow rate of the pneumatically dispensable glaze must be very limited to avoid the formation of droplets that would compromise the uniformity of the applied layer. Due to its thinness, the applied glaze layer inevitably exhibits non-uniformity in the form of streaks, essentially following the trajectory traversed by the dispensing nozzle. To limit this final drawback, a certain number of consecutive pneumatic dispensers must be arranged, each configured to apply its own glaze layer onto the tile overlapping the layer applied by the previous dispenser. This naturally leads to an increase in the size of the glazing compartments and a significant increase in the amount of glaze dispersed.

[0011] The purpose of this invention is to provide a tool that allows for a significant improvement in the glazing process of ceramic tiles, thereby allowing for the application of a continuous and uniform glaze layer while minimizing glaze waste and the time required for glazing.

[0012] In particular, the present invention fundamentally changes the principle of glazing compared to current technology. In fact, the present invention allows for the application of a continuous and uniform glaze layer not by means of a pneumatic distributor, but by means of an inkjet head advantageously configured for this purpose.

[0013] Additional features and advantages of the invention will become more apparent from the following detailed description of embodiments of the invention illustrated by way of non-limiting examples in the accompanying drawings, in which:

[0014] - Figure 1 An isometric view of the head according to the invention is shown;

[0015] - Figure 2 It shows Figure 1 The head is a cross-sectional view of the plane based on the trace AA;

[0016] - Figure 3 It shows Figure 1 The head is a cross-sectional view of the plane based on the trace BB;

[0017] - Figure 4 It shows Figure 2 The magnified area;

[0018] - Figure 5 It shows Figure 3 The magnified area.

[0019] The inkjet head according to the invention includes a dispensing unit (2) associated with an actuator (5).

[0020] The distribution unit (2) includes a main circulation conduit (21) for circulating ceramic glaze. In a known manner, the main conduit (21) has an inlet opening (21a) and an outlet opening (21b) connected to a glaze circulation loop (not shown in detail), which functions to keep the glaze itself in continuous motion, thereby preventing the formation of deposits.

[0021] The dispensing unit (2) comprises two or more nozzles (3) positioned in communication with the main channel (21) and preferably distributed along the main direction (X). Under normal use of the inkjet head, the main direction (X) is substantially horizontal. The term "nozzle" generally refers to a forming orifice designed to allow the dispensing of a certain amount of ceramic glaze. The forming orifice preferably has a cylindrical shape concentric with a central axis that substantially marks the dispensing direction of the ceramic glaze. Each nozzle (3) has: an inlet opening, arranged at the first end of the nozzle (3) and facing the main channel (21), i.e., positioned in communication with the main channel (21); and an outlet opening, arranged at the opposite end of the nozzle (3) and facing outward.

[0022] In the depicted embodiment, the central axis of the nozzle is substantially perpendicular to the main direction (X) and is substantially vertically oriented under normal use conditions.

[0023] Under normal inkjet head usage conditions (i.e., for glaze dispensing), the main channel (21) is maintained at a pressure greater than atmospheric pressure. In other words, the glaze circulation loop connected to the main channel (21) is under a pressure greater than atmospheric pressure.

[0024] In the depicted embodiment, the nozzles (3) are aligned in a single row along the main direction (X). In other embodiments not shown, the nozzles (3) can be arranged in multiple rows parallel to the main direction (X) or in another manner. Typically, the nozzles (3) are arranged to define a printing front (S), which is understood to be the width of a surface measured parallel to the main direction (X) on which the glaze dispensed by the nozzles (3) can be deposited. In other words, the printing front refers to the overall width of the nozzles (3) in a horizontal plane or in an orthogonal projection onto a plane parallel to the plane intended to receive the dispensed ceramic glaze. The plane intended to receive the ceramic glaze is typically the surface of a ceramic plate located in a horizontal plane.

[0025] The dispensing unit (2) also includes at least one baffle (4) that can be activated to close or release the nozzle (3). An actuator (5) is arranged to activate the baffle (4).

[0026] Unlike current inkjet heads, the baffle (4) is adapted to simultaneously close all nozzles (3) in at least one closed configuration. In other words, the baffle (4) is configured to be able to simultaneously close all nozzles (3) in a closed configuration. In essence, the baffle (4) is movable between such a closed configuration and at least one open configuration, in which the baffle is able to close all nozzles (3) and in the at least one open configuration, the baffle releases at least one nozzle (3) to allow the spraying of ceramic glaze.

[0027] By releasing at least one nozzle (3), the baffle (4) is deflected and the inlet opening of the nozzle (3), i.e. the opening of the nozzle (3) facing the main channel (21), is released. Under these conditions, the glaze present in the main channel (21) flows freely through the nozzle (3), especially if the main channel (21) is maintained at a pressure greater than atmospheric pressure.

[0028] The idea of ​​creating and using baffles (4) suitable for simultaneously closing all nozzles (3) avoids the need for a single baffle for each nozzle (3) and thus allows the nozzles (3) to be very close together to cover a substantially uniform printing front. In other words, the nozzles (3) are spaced apart at a distance whose length is measured along the main direction (X) to allow the glaze flow distributed by the nozzles (3) on the printing front to overlap, such that the glaze distributed by the nozzles (3) uniformly covers the entire printing front. This allows the inkjet head according to the invention to spread a uniform glaze layer on the surface below the nozzles (3).

[0029] The inkjet head according to the invention can be used in digital decorative elements for ceramic tiles. Essentially, the inkjet head according to the invention can replace current decorative heads used for decoration, which are unsuitable for glazing or distributing a uniform layer of ceramic glaze on tiles. This is because decorative heads are designed to create very specific and complex decorations, requiring very precise glaze distribution. For this purpose, each of these dispensing nozzles requires its own dedicated baffle, and thus cannot access the points where a uniform glaze layer can be spread, as is required for proper glazing.

[0030] As is known in the art, digital decorative elements include a transport plane movable along a forward direction on which the plates or tiles to be decorated are continuously placed. The transport plane guides the tiles to a printing unit, i.e., to an actual printing apparatus comprising a plurality of decorative heads positioned above the transport plane with their nozzles facing downwards. The decorative heads can be distributed in various ways. For example, the decorative heads can be arranged in parallel rows along a direction perpendicular to the forward direction. The decorative heads can be offset therebetween to cover sufficient printing front to distribute glaze in all areas beneath the plate.

[0031] In composite-type digital decorative parts, the inkjet head according to the invention is essentially replaceable. By means of a control module or computer-controlled actuator (5) known in the art, it is possible to activate or deactivate the glaze dispensing through the nozzle (3) as the tile or panel passes under the inkjet head, in a manner exactly similar to that occurring in digital decorative parts.

[0032] In the preferred but non-exclusive embodiment shown, the baffle (4) comprises: a body (41) made of an elastomeric material; and at least one side (41s) at which the baffle is associated with the main tube (21). An elastomeric material is a material capable of elastic deformation, even locally or in a limited volume region, such as rubber or silicone. In other words, an elastomeric material is a material that can deform if subjected to mechanical action or crushing and returns to its initial form once it is no longer subjected to mechanical action.

[0033] The body (41) faces the nozzle (3) and is designed to contact the nozzle in the closed position of the baffle (4), thereby preventing glaze dispensing. In this embodiment, the body (41) is movable between the aforementioned open and closed positions. In other words, referring to the depicted embodiment, the open or closed position of the baffle (4) can now be referenced to the open or closed position of the body (41).

[0034] Two or more spaced-apart magnetic elements (42) are associated with the body (41). The magnetic elements (42) are intended to be objects that include, are composed of, or are otherwise readily interacting with a magnetic field, thereby moving along at least one direction via the latter.

[0035] In the depicted embodiment, the actuator (5) comprises two or more solenoids (51), each solenoid acting on a corresponding magnetic element (42). Specifically, the actuator (5) and the baffle (4) are positioned relative to each other such that each magnetic element (42) is positioned substantially concentrically with respect to the corresponding solenoid. In a known manner, by activating each solenoid (51), the magnetic element (42) facing the solenoid (51) can be attracted or repelled. Particularly advantageous embodiments for the actuator (5) are described in Italian patent applications 102015000031664 and 102015000031675, the descriptions of which are intended to be incorporated herein.

[0036] By activating the solenoid (51) simultaneously, the magnetic element (42) can be moved simultaneously, thereby causing the main body (41) to move between the open and closed positions.

[0037] In the illustrated embodiment, the baffle (4) includes a plurality of magnetic elements (42) aligned along the main direction (X). The actuator (5) includes a corresponding number of solenoids (51), each solenoid aligned with a corresponding magnetic element (42) along a direction perpendicular to the main direction (X). In particular, each solenoid (51) has a longitudinal axis (Y), and the corresponding magnetic element (42) is concentric with respect to this longitudinal axis.

[0038] The magnetic element (42) is firmly bound to the body (41). Simultaneous activation of the solenoid (51) allows the magnetic element (41) to be translated simultaneously away from or toward the solenoid (51), and thereby the body (41) is translated according to the magnetic element (42). In this case, the body (41) moves substantially rigidly, thereby achieving the simultaneous opening or closing of all nozzles (3).

[0039] Preferably, the magnetic elements (42) are aligned parallel to the main direction (X) and separated by a regular spacing, that is, they are separated from each other by a constant distance along the main direction (X).

[0040] In embodiments where the inkjet head body (41) is made of an elastomeric material, non-uniform translation of the body (41) itself is also permitted. Specifically, the body (41) is deformable between a closed configuration and at least one partially open configuration, in which the body closes all nozzles (3) and in the at least one partially open configuration, a portion of the body (41) closes a portion of the nozzles (3), and another portion of the baffle (4) releases another portion of the nozzles (3). In other words, the body (41) made of an elastomeric material can adopt one or more deformable configurations in which the body can open some nozzles (3) and close others (3).

[0041] In a preferred embodiment of an inkjet head where the actuator (5) includes a solenoid (51), non-uniform translation of the body (41) (i.e., the deformation of the body (41) described above) can be achieved by means of non-simultaneous and / or non-uniform activation of the solenoid (51). Essentially, by activating only a portion of the solenoid (51), the corresponding magnet (42) can be translated and displacement of the corresponding portion of the body (41) can be generated.

[0042] If the inkjet head, particularly the dispensing unit (2), is positioned across the side edge of the surface to be glazed, the possibility of localizing the opening / closing of the nozzles (3) is very useful. In this case, a portion of the nozzles is located outside the surface to be glazed. Therefore, the glaze dispensed by such nozzles is essentially dispersed and should be recycled or disposed of. Due to the inkjet head according to the invention, and particularly due to the body (41) formed of the elastomeric material of the baffle (4), the nozzles (3) located outside the surface to be decorated can be closed, and the nozzles located inside the surface to be decorated can be opened. This allows for limiting or canceling the dispensing of glaze outside the surface to be glazed.

[0043] Preferably, but not necessarily, the inkjet head includes a ferromagnetic element (43) positioned to contact two or more magnetic elements (42). The ferromagnetic element (43) allows for a significant increase in the force that the solenoid (51) can apply to each magnetic element (42) using the same supply current. The greater force applied to each magnetic element (42) allows for improved control of the body (41). For example, in the closed position, a greater force can be applied to press the body (41) into contact with the nozzle (3), resulting in better closure. Furthermore, applying a greater force to the magnetic element (42) facilitates differentiated displacement of the body (41), i.e., facilitates deformation of the body (41) so that only some nozzles (3) are opened or closed relative to the other nozzles (3). Another advantage given by the use of the ferromagnetic element (43) is that it facilitates frequency activation of the magnetic element (42), i.e., it allows for the dispensing of enamel through the nozzles (3) not only by the stable positioning of the body (41) in the open position, but also by the cyclic movement between the open and closed positions, using a certain frequency established by the frequency activation through the solenoid (51).

[0044] In the depicted embodiment, the ferromagnetic element (43) is in the form of a relatively thin plate and is arranged to contact the magnetic element (42). The thickness of the ferromagnetic element (43) can be selected relative to the control intended to perform displacement of the body (41). If the aim is to provide rigid control of the body (41), even if the body (41) moves as a rigid body to achieve simultaneous closing or opening of the nozzles (3) and / or facilitate frequency control, it is preferable to use a ferromagnetic element (43) with a greater thickness. If the aim is to provide differentiated control of the body (41), i.e., including control of the possibility of deforming the body (41) to achieve the closing / opening of some nozzles (3) relative to other nozzles, it is preferable to use a ferromagnetic element with a lower thickness and greater flexibility.

[0045] In the preferred but non-exclusive embodiment shown, the magnetic element (42) and the ferromagnetic element (43) are housed within the body (41). In particular, the magnetic element (42) and the ferromagnetic element (43) are integrated within the body (41). This configuration is particularly advantageous when the body (41) is made of an elastomeric material, as it greatly improves the accuracy of control over the movement of the body (41).

[0046] In the preferred but non-exclusive embodiment depicted, the dispensing unit (2) includes a housing (22) in which a main tube (21) is defined. The inlet opening (21a) and outlet opening (21b) of the main tube (21) are located in corresponding fittings securely bound to the housing (22). A nozzle (3) is positioned on the lower wall of the housing (22) to connect the main tube (21) to the outside. Preferably, the nozzle (3) is obtained via a plate (31) associated with the lower wall of the housing (22). This plate (31), and thus the surface defining the nozzle (3), is made of an elastomeric material. The use of an elastomeric material, which is highly resistant to the abrasive action applied by ceramic glaze, allows for an increased duration of the nozzle (3), maintaining its initial shape for a longer time compared to ordinary nozzles made of hard materials. Furthermore, the use of an elastomeric material (and therefore elastically deformable) limits clogging of the nozzle (3). This is because the nozzle (3) is able to elastically deform, allowing any blockage to be expelled.

[0047] On the side opposite to the nozzle (3), the main guide tube (21) is at least partially closed by the baffle (4). For example, in Figure 2 As can be seen, the baffle (4) is associated with the housing (22) and connected to the body (41) at two side portions (41s). The latter protrudes toward the nozzle (3) inside the main channel (21). Preferably, the body (41) has a tapered shape in the direction of the nozzle (3). The body (41) also has a substantially flat front surface (44) which is designed to contact the nozzle (3) in the closed position of the baffle (4).

[0048] Apart from the inlet opening (21a) and outlet opening (21b) and the nozzle (3), the dispensing unit is isolated from the outside.

[0049] The actuator (5) is associated with the housing (22) on the opposite side of the nozzle (3). The actuator (5) is preferably made as a single body, as described in Italian patent applications 102015000031664 and 102015000031675, the descriptions of which are intended to be incorporated herein. The actuator (5) is associated with the top cover (22a) of the housing (22). The top cover (22a) has a plurality of openings, each aligned and / or concentric with a corresponding magnetic element (42). Furthermore, the openings of the top cover (22a) are positioned to align with the longitudinal axis (Y) of each solenoid (51). In particular, the actuator (5) is positioned such that the ferromagnetic core of each solenoid (51) faces the corresponding opening of the top cover (22a), thereby reducing the distance relative to the corresponding magnetic element (42). Furthermore, the longitudinal axis (Y) and the principal direction (X) of the solenoid (51) are in the same plane. The spray direction of the nozzle (3) is basically parallel to the plane.

[0050] Advantageously, the actuator (5) is removably associated with the dispensing unit (2), thereby allowing the dispensing unit (2) to be replaced with another dispensing unit (2). Since both the dispensing unit (2) and the actuator (5) are constructed as a single block, coupling devices can be used within the reach of those skilled in the art to removably bind one to the other. Replacement of the dispensing unit (2) allows, for example, the use of dispensing units (2) with different numbers of nozzles (3) and / or nozzles with different sizes and / or different distributions, or simply the replacement of the dispensing unit (2) with another similar dispensing unit in the event of maintenance or failure.

Claims

1. An inkjet head, comprising: - a dispensing unit (2) provided with: a main circulation duct (21) for circulating ceramic ink; two or more nozzles (3) placed in communication with said main circulation duct (21) and distributed along a main direction (X); a shutter (4) activatable to close or release said nozzles (3); - an actuator (5) arranged to actuate said shutter (4); wherein said shutter (4) is movable between at least one closed configuration, in which it is able to close all of said nozzles (3), and at least one open configuration, in which it releases at least one nozzle (3) to allow ejection of ceramic ink, wherein said shutter (4) comprises a main body (41) made of elastomeric material, two or more magnetic elements (42) are associated with said main body and are mutually spaced apart, and wherein said actuator (5) comprises two or more solenoids (51), each of which acts on a respective magnetic element (42), said inkjet head comprising a ferromagnetic element (43) placed in contact with said two or more magnetic elements (42). said magnetic elements (42) and said ferromagnetic element (43) are housed inside said main body (41).

2. The inkjet head according to claim 1, wherein said shutter (4) is deformable between said closed configuration and at least one partially open configuration, in which a portion of said shutter (4) closes a portion of said nozzles (3) and another portion of said shutter (4) releases other nozzles (3).

3. The inkjet head according to claim 1 or 2, wherein said dispensing unit (2) comprises a housing (22) inside which said main circulation duct (21) is delimited, and wherein said main circulation duct (21) is at least partially closed by said shutter (4) associated with said housing (22).

4. The inkjet head according to claim 1 or 2, wherein said nozzles (3) are placed on a lower wall of said housing (22) so as to put said main circulation duct (21) in communication with the outside, and are obtained by means of a plate (31) associated with the lower wall of said housing (22).

5. The inkjet head according to claim 4, wherein said plate (31) is made of elastomeric material.

6. The inkjet head according to claim 5, wherein said actuator (5) is removably associated with said dispensing unit (2), thus allowing replacement of said dispensing unit (2) with another dispensing unit (2).

7. The inkjet head according to claim 1 or 2, wherein ​

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