Printing unit and cleaning method

Description

71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) DESCRIPTION Attached to a patent application for an INDUSTRIAL INVENTION having by title “Printing unit and cleaning method” On behalf of: SYSTEM CERAMICS SPA VIA GHIAROLA VECCHIA 73 41042 FIORANO MODENESE MO ******* The present invention relates to a printing unit and a method of cleaning of said printing unit. The present invention finds advantageous application in the field of inkjet printing, in particular for sheet-shaped products; 5 preferred, but not exclusive, application of the present invention concerns inkjet printing for sheet-shaped products in the sector ceramic, such as tiles and slabs. When decorating substrates by inkjet printing, one or more print bars can be used to deliver a 10 plurality of inks, in order to achieve the desired decorative effects. Inkjet decoration printing bars are known to the sector and typically include one or more print heads, equipped with ink delivery nozzles, connected to an ink tank via a power line; furthermore, if the print heads are of the 15 ink recirculation type, these heads are further connected to the tank or to a chamber communicating with the tank through a recirculation line. Through the supply line, the ink is supplied to each head and made available for printing operations; through the recirculation line, the ink can return to the tank and be 20 advantageously kept in motion, avoiding phenomena of unwanted clumping or drying caused by ink stasis a prolonged time. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) Sometimes, however, one or more heads inside a print bar can suffer from malfunctions, mainly due to of the nozzles: the nozzles, due to their three-dimensional shape presenting a progressive narrowing of section, can 5 example, getting fillings due to an ineffective ink movement by the recirculation system, or due to of unwanted air entering the head from the environment surrounding air which causes the ink to dry. Consequence of the malfunction of one or more printheads 10 inside a print bar is that the pattern printed on the substrate has unprinted lines where the nozzles are clogged and, of consequence, a decoration that does not respect the decorative standards required for that item. In the known art there are widespread methods for cleaning clogged nozzles including: 15 phases of: -stop the ink flow by turning off the printing unit; -remove the damaged printhead or heads; -take the damaged printhead or heads to a separate headquarters, where specific operations, called regeneration, take place, aimed at 20 to restore the functionality of the head where possible; -replace the damaged head or heads with a new head or new heads of the same type, if available. However, this method is expensive, as it involves replacing of the malfunctioning head or heads; furthermore, this method requires 25 that the print bar remains inoperative for the time necessary to remove the heads and carry out the operations to replace them heads. In conclusion, this method is expensive in terms of time and costs. Alternatively, a further cleaning method is widespread in the art 30 clogged nozzles including the following steps: 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) -place an ink collection tray underneath the bar of print; -start a process called “purge”, in which the ink is put into pressure and forced under pressure through the nozzles, until it expels, 5 possibly, the filling created. Even in this case, the cleaning method has limitations: first of all place is not necessarily the solution and the pressure set is sufficient to free the clogged nozzles; furthermore, when effective, the method involves the consumption of a considerable amount of ink, which is 10 collected in the collection tray, but which cannot be placed in the collection container back into the tank, having come into contact with pollutants, such as solid particles. The object of the present invention is to provide a printing unit and a cleaning method for said printing unit capable of overcoming the obvious 15 limitations of the prior art. In particular, the purpose of the present invention is to provide a unit of printing and a cleaning method for said printing unit capable of restore nozzle functionality quickly and efficiently, limiting interruptions to printing operations as much as possible. 20 A further object of the present invention is to provide a printing unit and a method of cleaning the said printing unit which can avoid unnecessary waste of ink. Further features and advantages of the present invention better will appear from the following description, given purely for information purposes 25 exemplifying and non-limiting, of some illustrated embodiments in the attached figures, in which: -Figure 1 shows a front view of a printing unit comprising a print block in print configuration; -Figure 2 shows a front view of the printing unit of Figure 1 in which 30 the print block is in cleaning configuration; 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) -Figure 3 shows a bottom isometric view of the printing unit of figure 1; -Figure 4 shows a bottom isometric view of the printing unit of figure 2; 5 - Figure 5 shows a top isometric view of the printing unit of figure 1; -Figure 6 shows a top isometric view of the printing unit of figure 2. The numerical reference 10 indicates a printing unit according to the 10 present invention. In fact, the first object of the present invention is a unit of print 10 comprising a print block 20 and a cleaning block 30. With reference to figures 1-6, the printing block 20, in detail, 15 comprises a printing bar B having a plurality of nozzles N of ink delivery in a Y delivery direction to define, below said printing block 20, a dispensing plane P of the ink. Typically, the Y direction of flow is perpendicular to the flow plane. 20 ink supply P and ink is released from the N nozzles for dripping from the print bar B and, in particular, from the nozzles N towards a substrate that is intended to be decorated. The prior art B printing bars, in fact, typically comprise a plurality of printheads, each configured to deliver a 25 ink type in the Y-direction of delivery onto a substrate, such as example, but not exclusively a sheet-like substrate such as a ceramic tile or slab. Preferably, each print bar B or print head, comprising said plurality of nozzles N, is connected to one or more tanks 30 of ink through a respective supply line, configured 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) to power the print bar B or print head with a type of ink drawn from a reservoir. Additionally, preferably, each print bar B or print head includes one or more recirculation lines, configured to return to the 5 respective tank the ink not dispensed from the nozzles N. The N nozzles of the print bar B are operationally connected to a shutter element included in said printing bar B: the element shutter can be actuated first in a non-operating configuration obstruction, to allow ink to flow in the direction of 10 Y delivery, defining, below the printing bar B, the printing plane ink supply P. The shutter element, secondly, can be implemented in a shutter configuration, to prevent ink from flowing into the Y direction of flow. In other words, when the shutter element is 15 implemented in the shutter configuration no delivery occurs ink from the dispensing plane P in the dispensing direction Y. Shutter elements are, for example, implemented between the configuration of filling and non-filling configuration repeatedly and at a preset frequency in order to generate ink droplets of size 20 predetermined and subsequently delivered by the N nozzles in the direction of Y delivery, so that they are deposited on the substrate to be decorated. The shutter element preferably comprises a plurality of actuators mechanical or electro-mechanical, each operationally connected to one or more N nozzles and able to assume the clogging and non-closing configuration 25 blockage at said nozzle N or said plurality of nozzles To which it is operationally connected. Mechanical actuators of the type known to the industry include actuators piezoelectrics that assume the obturation or non-obturation configuration closure in response to electrical operating commands. 30 Even more preferably, the operational commands are sent from a control system control integrated into the printing block 20 and communicating with each 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) shutter element, mechanical actuator and / or piezoelectric actuator, al in order to obtain the clogging or non-clogging configuration on some or all of the N nozzles included in the print bar B. In other terms, each shutter element is independently actuable between the 5 shutter configuration and non-shutter configuration. The printing unit 10 according to the present invention further comprises the cleaning block 30, intended, as will be seen later, to perform Printing block cleaning operations 20. In other words, the cleaning block 30 is configured to allow cleaning, 10 partial or total, of the printing block 20 and, in particular, of the bar print B and, even more in detail, of one or more N nozzles during interventions for repair or maintenance. The cleaning block 30 comprises at least a first element of opening / closing 4 and one or more actuator means M of said element 15 opening / closing 4. The actuator means M can be operationally connected to the opening / closing element 4 and / or to the printing bar B, determining, directly or indirectly, the implementation of the element of opening / closing 4 between an open configuration and a closed configuration closed. 20 In detail, the opening / closing element 4, in detail, is achievable between the open configuration, in which it allows the delivery of ink from the N nozzles, and the closed configuration, in which at least partially prevents the ink from being dispensed by the nozzles N. 25 In other words, in the open configuration, the opening / closing element 4 is implemented in such a way as to allow one or more nozzles N belonging to the print bar B dispense ink in the dispensing direction Y from the dispensing plane P (Fig.1, Fig.3, Fig.5). Conversely, in the closed configuration, the opening / closing element 4 is actuated in a 30 such as to prevent one or more nozzles N belonging to the printing bar B 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) dispense ink in the Y dispensing direction from the dispensing plane P (Fig.2, Fig.4, Fig.6). The opening / closing element 4 can be actuated in different ways, corresponding to different embodiments of the present invention, 5 illustrated in the following paragraphs. The actuator means M are operationally connected to the element of opening / closing 4 and / or to the print bar B and are configured for implement the opening / closing element 4 between the open configuration and the closed configuration, and vice versa. In particular, the actuator means M are 10 configured to actuate the opening / closing element 4 between the open configuration and closed configuration, and vice versa, when the shutter element of each nozzle N is in the shutter configuration or non-filling. Preferably, the actuator means M of the opening / closing element 4 15 operate independently of the shutter element of each nozzle N. In other words, at least the following four modalities can be identified operational, defined by the open and closed configurations of the element opening / closing 4 and the shutter and non-shutter configurations obturation of the shutter element, and their combinations. 20 In detail, the opening / closing element 4 can be implemented in the open configuration when the shutter element of each nozzle N is in shutter configuration or when the shutter element of each nozzle N is in non-clogging configuration, identifying a first and a second operating mode. 25 In the first operating mode, in which the opening / closing element 4 is in open configuration and the shutter element is in the open configuration clogging, ink delivery through the nozzles is prevented from the shutter element: this flow can be prevented or interrupted or arrested for a more or less prolonged period of time, depending on the 30 needs. For example, during a decoration operation of a substrate the opening / closing element 4 is held in 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) open configuration and the shutter element is actuated in the shutter configuration, for example, when it is not required the delivery of a type of ink onto a substrate or a portion of the same. 5 In the second operating mode, i.e. with the element of opening / closing 4 in open configuration and the shutter element in non-clogging configuration, the N nozzles operationally connected to said shutter can dispense ink in the dispensing direction Y: This allows not only the decoration of the substrate you intend to 10 decorating, but also operations of discharging the ink present in a head and its collection in a containment tank, for particular process needs. Furthermore, keeping the opening / closing element 4 in the configuration open and repeatedly actuating the shutter element between the configuration 15 of filling and non-filling, at a predetermined frequency, is it is possible to deliver ink drops of optimal size onto a substrate pre-established and dependent, for example, on the composition, the consistency and viscosity of the ink released from the print bar B. 20 Furthermore the opening / closing element 4 can be implemented in the closed configuration when the shutter element of each nozzle N is in shutter configuration or when the shutter element of each nozzle N is in non-clogging configuration, identifying a third and a fourth mode of operation. 25 In the third operating mode, in which the opening / closing element 4 is in closed configuration and the shutter element is in the closed configuration blockage, no ink is dispensed from the nozzles N in the dispensing direction Y. In this way, the idi element opening / closing 4 acts as a second barrier to prevent 30 ink supply. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) In the fourth operating mode, i.e. with the element of opening / closing 4 in closed configuration and the shutter element in non-closing configuration, the opening / closing element 4 operates as the only barrier to prevent ink from flowing in the direction 5 of Y delivery. Furthermore, it is possible to implement the shutter element in the configuration of filling and non-filling, repeatedly and at a frequency preset, keeping the opening / closing element 4 in the closed configuration. 10 The third and fourth modes can be activated for particular needs or during cleaning, repair or maintenance operations, which will be referred to in more detail in the following paragraphs. In fact, for example, when a press bar B or a portion of the the same is affected by the opening / closing element 4 implemented in the 15 closed configuration, the ink, forced inside the N nozzles, can be recirculated directly into the recirculation line without being dispensed and / or can be agitated by repeated activations of the shutters to remove air bubbles present in the ink and / or can be agitated, always through repeated activations of the shutters, to break, 20 move or remove agglomerates of sedimented ink and solidified. Further details regarding cleaning, repair or maintenance operations maintenance will be provided later. Advantageously, thanks to the opening / closing element 4 actuated by the 25 actuator means M, the printing unit 10 according to the present invention is in able to both dispense ink, obtaining both the decoration of a substrate or ink discharge of print bar B, whether stop the ink supply quickly and efficiently, in order to to allow maintenance and cleaning operations or operations 30 interventions following breakdowns. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) As a result, not only the printing and unloading operations of ink, but also the aforementioned maintenance, cleaning and intervention can be advantageously performed while the bar is print B is placed in correspondence with the printing unit 10: in others 5 terms, unlike the devices from prior art, the operations of maintenance, cleaning and intervention can be performed without remove print bar B from print unit 10. Advantageously, the printing unit 10, comprising the printing block 20 and the cleaning block 30, is therefore versatile in operation. 10 The printing unit 10, finally, advantageously allows to bring to complete cleaning, maintenance and intervention operations quickly and efficient. Preferably, the printing block 20 or printing bar B and the block of cleaning 30 of the printing unit 10 according to the present invention are 15 mutually mobile with respect to each other. In other words, it is possible detect a relative motion between the print block 20 or the print bar B and the cleaning block 30 inside the printing unit 10 according to the present invention. In other words, the print block 20 or the print bar B are 20 mobile, while the cleaning block 30 is fixed; alternatively, the cleaning block print 20 is fixed, while the cleaning block 30 is movable; alternatively again, both the print block 20 or the print bar B, and the print block cleaning 30 are movable, for example along a support frame. Preferably, the print bar B is movable along the support frame 25 between a first position, corresponding to a print configuration, and a second position, corresponding to a cleaning configuration. Preferably, when the printing block 20 is in the printing configuration, the opening / closing element 4 is implemented in the open configuration, to allow ink to be dispensed into the 30 Y-direction of delivery to realize the decoration of a substrate. Preferably, when the printing block 20 is in the 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) cleaning configuration, the opening / closing element 4 is actuated in the closed configuration, to allow cleaning operations to be carried out, maintenance or repair of the print bar B, the print head print or nozzles N. 5 In detail, and even more preferable, the printing bar B is movable vertically along the support frame between the first position, placed below and corresponding to the printing configuration (Fig.1, Fig.3, Fig.5), and the second position, placed superiorly and corresponding to the cleaning configuration (Fig.2, Fig.4, Fig.6). 10 Therefore, when the press bar B is positioned lower, a substrate, placed underneath it or in transit on a conveyor placed underneath it, can be decorated for ink delivery from nozzles N. Conversely, when the print bar is positioned at the top and 15 the opening / closing element 4 is actuated in the closed configuration, the substrate, placed underneath it or in transit on a conveyor placed below it, or is only affected partially or not affected by ink delivery from the nozzles N, which are at least partially closed by the element of 20 opening / closing 4. In the following paragraphs we will go into detail about the components of the unit. of printing 10 according to the present invention: in particular, there will be some non-exclusive embodiments of the element are explained opening / closing 4 and the actuator means M included in the printing unit 25 10 according to the present invention. In a first embodiment of the printing unit 10, the cleaning block 30 includes an opening / closing element 4 having a surface S, in use at least partially positioned in correspondence of the dispensing plane P of the printing bar B, when the element of 30 opening / closing 4 is implemented in the closed configuration. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) The surface S of the opening / closing element 4 is, therefore, shaped in such a way as to at least partially prevent the ink from leaking from the nozzles N. The surface S can be, for example but not exclusively, placed in response to the N nozzles and, in particular, to a 5 respective ink outlet opening, physically preventing the ink leakage. The surface S, in other words, placed at check of the N nozzles and, in particular, of the respective openings of of the ink, acts as a physical barrier, preventing the ink be delivered in the Y delivery direction. 10 Preferably, but not exclusively, the surface S is flat. The surface S may have smaller dimensions than those identified by the print bar corresponding to the print plane P delivery: in this case, the surface S, implemented in the configuration closed, it prevents ink from leaking from some of the parts 15 N nozzles included in the print bar B. Therefore, for a plurality of nozzles N, affected by the surface S, is not permitted the ink supply and for another plurality of nozzles N, not affected From surface S, ink dispensing is allowed. Alternatively, the surface S may have dimensions at least equal to 20 or more than those identified by the print bar in correspondence of the dispensing plane P: in this case, the surface S, implemented in the closed configuration, it allows to prevent the leakage of ink from all N nozzles included in the print bar. Alternatively still, the opening / closing element 4 may have 25 two or more surfaces S, independently actuated by the actuator means M from open configuration to closed and conformed configuration each to prevent the leakage of ink from a respective plurality of nozzles N belonging to the print bar B. In other words, and advantageously, the cleaning block 30 comprising 30 the plurality of surfaces S allows to selectively block the leakage of ink from different portions of the same print bar, 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) allowing maintenance operations and cleaning interventions and targeted repairs. Intuitively, the opening / closing element 4 can take on a plurality of configurations and conformations. 5 In the preferred embodiment of the printing unit 10 according to the present invention, the opening / closing element 4 comprises at least a sheet of flexible material, shaped to adhere at least partially to the P delivery plan when implemented in the configuration closed. In other words, when the actuator means M actuate the element of 10 opening / closing 4 in the closed configuration, the flexible sheet is moved in correspondence with the dispensing plane P and is made adhere to the press bar B. Intuitively, two or more sheets of flexible material can be included in the opening / closing element 4. 15 Even more preferably, the opening / closing element 4 comprises a sheet of flexible material that is impermeable to the ink dispensed, in order to prevent the ink from permeating through the paper itself and being released in the Y dispensing direction. The printing unit 10 according to the present invention comprises, as 20 introduced in the previous paragraphs, the actuator means M configured for implement the opening / closing element 4 between the open and closed configurations closed configuration, and vice versa. The M actuators can be manual or automatic. The automatic type M actuators can be configured to 25 receive operational commands from the control system and implement the control element open / close 4 in open or closed configuration in response to said operational commands. The M actuators can be of various types, also depending on the type of opening / closing element 4 included in the cleaning block 30 30. Different types of M actuators and different combinations of M actuators 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) can be advantageously employed, as will be described in the paragraphs to follow. In a first embodiment, the actuator means M may comprise a device for moving the printing bar B between the 5 Cleaning configuration and printing configuration introduced in previous paragraphs. In particular, the movement device comprises a motor operationally connected to the print bar B. In other words, the motor, operationally connected to the printing bar B, 10 is configured to determine the movement of the print bar B between print configuration and cleaning configuration and vice versa. Preferably, the motor operationally connected to the print bar B It is configured to determine the movement of the print bar B vertically, between the first position, placed below and 15 corresponding to the print configuration, and the second position, positioned above and corresponding to the cleaning configuration, and vice versa. Additionally or alternatively, the actuator means M can include handling equipment configured to handle 20 the opening / closing element 4 moving away from the plane of P delivery, to obtain the open configuration, and / or approaching to the dispensing plane P, to obtain the closed configuration. In the preferred embodiment of the printing unit 10 according to the present invention, the actuator means M comprise elastic means, in 25 particular spring means, operatively connected to the element of opening / closing and configured to move the element of open / close 4 from open configuration to closed configuration, and vice versa. In particular, the elastic or spring means cooperate with the movement device and, in particular, with the motor connected to the 30 B press bar to allow switching between closed and closed configuration open configuration of the opening / closing element 4 and for 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) determine the return to the closed configuration of the element of opening / closing 4. The preferred embodiment of the printing unit 10, in fact, comprises the motor operationally connected to the press bar B and the spring means 5 operationally connected to the opening / closing element 4 and cooperating with said engine. In the cleaning configuration, the print bar is located at the top placed and the opening / closing element 4 is actuated in the configuration closed (Fig.2) by spring means: the opening / closing element 4 10 preferably comprises a sheet of flexible material, implemented or kept substantially horizontal and coplanar to the plane of P delivery of the printing bar B. In other words, the spring means, a rest, keep the flexible material sheet in configuration essentially horizontal. 15 When switching between the cleanup configuration and the configuration print, the motor moves the print bar B vertically from the first position, placed above, to the second position, placed lower down. In the transition from the first to the second position, the press bar B, 20 moved by the engine, exerts a force on the surface S of the opening / closing element 4 and, consequently, on the means to spring, causing it to shorten or compress. As a result of the further downward movement of the bar of printing B and the shortening of the spring means, the element of 25 opening / closing 4, in particular the flexible material sheet, is rotated moving away from the P delivery plane until reaching a substantially vertical configuration when the press bar B reaches the second position corresponding to the configuration of print (1). 30 The movement of the printing bar B vertically upwards, for return to cleaning configuration, determines the movement 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) opposite of the opening / closing element 4, which returns to configuration closed, or substantially horizontal, due to the elastic force exerted from the spring elements. Alternatively to the preferred embodiment described, the means of 5 M movement may include one or more types of devices of different types, as will be illustrated in the following paragraphs, provided that they are configured to move the opening / closing element 4 in moving away from the P delivery plan, to obtain the configuration open, and approaching the P delivery plane, to obtain the 10 closed configuration. In a first alternative embodiment the actuator means M include sliding means, configured to move the element of opening / closing 4 away from the dispensing plane P and in approaching the P delivery plan. 15 In a second alternative embodiment, the actuator means M include rotation means, configured to move in rotation the opening / closing element 4 between the closed configuration in proximity of the P dispensing plane and the open configuration, moving away from the delivery plan P, and vice versa. In this case, the actuators M 20 include rotation means and are operationally connected to a opening / closing element 4, preferably comprising the sheet in flexible material: the M actuators are therefore hinged to the frame support and determine the rotation of the flexible sheet in approaching the P delivery level, in the transition from 25 open configuration to closed configuration. Here, the flexible sheet is maintained in correspondence with the dispensing plane P, in contact with the N nozzles, to create a barrier to prevent ink leakage from the N nozzles, for a cleaning time: the cleaning time is variable at depending on the operation, cleaning, maintenance or repair, which 30 is intended to be completed. Therefore the actuators M, after the time has elapsed cleaning, determine the rotation of the flexible sheet away from 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) from the P dispensing plane, from the closed configuration to the configuration open, and the N nozzles of the print bar B can again dispense ink. The actuator means M of the sliding type or including rotation means 5 can also be cooperating with the handling device of the printing bar B including the motor, of the type described in the previous paragraphs. In conclusion, the printing unit 10 according to the present invention is in capable of both dispensing ink, decorating a substrate, and 10 stop ink supply quickly and efficiently, a allow the performance of cleaning, maintenance or repair. Advantageously, cleaning, maintenance or Repairs can be performed without removing the print bar B from the printing unit 10, simplifying said operations and shortening the 15 times needed to complete them. Advantageously, as a result, cleaning operations, maintenance or repairs can be carried out without any risk operator intervention is required to remove a printhead print belonging to the print bar B from the print unit 10 and the 20 subsequent repositioning of the same head in correspondence of the print bar B or a different head at the print bar B in print unit 10. As anticipated in the previous paragraphs, when the element of opening / closing 4 is implemented in the closed configuration, the ink does not 25 is dispensed in the dispensing direction and the print bar B or heads of printing or the N nozzles affected by the opening / closing element 4 implemented in the closed configuration can be subjected to cleaning, maintenance and repair operations. In fact, according to the object of the present invention, a method of 30 cleaning for a printing unit 10 comprising a printing block 20 and a cleaning block 30. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) Printing unit 10, printing block 20 and cleaning block 30 are preferably of the type described in the previous paragraphs. The method according to the present invention comprises, in particular, the phases of: 5 Prepare the printing block 20; Prepare the cleaning block 30 including the cleaning element open / close 4 in open configuration; Implement, by means of the actuator means M, the opening / closing element 4 from open configuration to closed configuration; 10 Perform a cleaning cycle of one or more N nozzles included in the cleaning bar print B of print block 20; Implement the opening / closing element 4 from the closed configuration to open configuration at the end of the cleaning cycle. The phases are reported in an unconstrained order and, therefore, can 15 be performed according to a different sequence of phases. Furthermore, not further steps are excluded from the method according to the present invention operational. In the Prepare print block 20 phase, for example, the block of press 20 can be moved from the first position, below 20 located and corresponding to the printing configuration, the second position, situated above and corresponding to the configuration of cleaning. In the Implementation phase, by means of the actuator means M, the element of open / close 4 from open configuration to closed configuration, 25 the opening / closing element 4, preferably the material sheet flexible, it is rotated towards the dispensing plane P until place in contact with the N nozzles of the print bar B. Opposite rotation of the flexible sheet is, conversely, performed by the means M actuators during the opening / closing phase 4 30 from closed configuration to open configuration at the end of the cycle of cleaning. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) Different types of cleaning cycles can be performed during the phase of Perform a cleaning cycle of one or more N nozzles included in the print bar B of print block 20. In fact with the end of the cycle cleaning means, in a broader sense, one or more of the following cleaning operations: 5 of the N nozzles, maintenance operation of the print bar B or of the N nozzles, N nozzle repair operations following malfunctions and / or other similar operations. Among the types of cleaning cycles that can be performed, the following is applied: The cleaning method for print heads is particularly advantageous 10 inkjet, subject of patent application number 102023000023100 in the name of the same Applicant and hereinafter briefly reported. Cleaning cycles or types of operations different from the one reported. The preferred, but not exclusive, cleaning cycle performed by the printing unit 15 10 includes the following phases: - Stop the ink supply to the supply line of the print bar B or print head; - Inject ink into the recirculation line at a flow rate predetermined, defining a recirculation operating mode; 20 - Maintain the recirculation operating mode for a cleaning time pre-established. Furthermore, said preferred cleaning cycle may include the phase of - Starting from an internal pressure value of the printing bar B or of the print heads, vary the internal pressure value. 25 In particular, starting from an internal pressure value of the bar print B or print heads, the cleaning cycle involves decreasing said internal pressure value to create such an internal depression to keep the opening / closing element 4 in the closed configuration, contact with the N nozzles of the print bar. This phase is 30 particularly effective in case the opening / closing element 4 includes a flexible sheet. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) In addition to or alternatively to the pressure variation phase internally, the cleaning cycle may include the phase of: - Wet the surface S of the opening / closing element 4. The phase of wetting the surface S precedes or is performed 5 simultaneously with the positioning of the surface S of the element opening / closing 4 in contact with the nozzles N or in other words, during the actuation of the opening / closing element 4 in the closed configuration. By wetting the surface S of the opening / closing element 4, it results improved adhesion capacity of the opening / closing element 4 10 compared to the printing bar B. This phase is particularly advantageous in the case in which the opening / closing element 4 includes the flexible material sheet, The cleaning cycle can also include the phase of - Change the value of the predetermined recirculation flow rate 15 of the ink. In particular, by increasing the recirculation flow rate, clogged heads large elements can be released by moving said obstructing elements. Finally, the preferred cleaning cycle may include the phases of 20 - Move or agitate the ink further in the operating mode of recirculation, for a handling time. The movement or agitation of the ink occurs preferably, but not exclusively, through mechanical actuators connected to the nozzles N. In other words, the movement or agitation of the ink can 25 occur by repeatedly actuating the shutter connected to the N nozzles, at a preset frequency, between the shutter configuration and the non-clogging configuration, maintaining the element of open / close 4 in closed configuration. The method according to the present invention advantageously allows to 30 free the nozzles N of the print bar B from dried ink, from unwanted impurities and / or air bubbles blocking the N nozzles themselves. 71.S0721.12.IT.196 Eng. Giovanni Casadei (Registered no. 1195 B) In conclusion, the method according to the present invention allows advantageously to perform a plurality of cleaning and maintenance cycles or different repairs, effectively and versatile, maintaining a printing bar B inside a printing unit 10, avoiding its 5 removal and reducing the time required to resolve any issues problems and faults that have arisen. THE AGENCY Eng. Giovanni Casadei (Registered no. 1195 B)

Claims

1. Printing unit 10 comprising: a printing block 20 comprises a printing bar B having a plurality of nozzles N operatively connected to a shutter element included in said printing bar B, and actuated between: a non-clogging configuration, to allow the dispensing of ink in a dispensing direction Y to define, below said printing block 20, an ink dispensing plane P; and a clogging configuration, to prevent the dispensing of ink in the dispensing direction Y, characterised in that it comprises a cleaning block 30 having at least one opening / closing element 4 actuable between an open configuration to allow the dispensing of ink by the nozzles N, and a closed configuration to at least partially prevent the dispensing of ink by the nozzles N;one or more actuator means M operatively connected to the opening / closing element 4 and / or to the printing bar B and configured to actuate the opening / closing element 4 between the open configuration and the closed configuration, and vice versa when the shutter element is in the closing or non-closing configuration.; 2. Printing unit according to claim 1 wherein the printing bar B is movable along a support frame between a first position corresponding to a printing configuration, in which the opening / closing element 4 is in the open configuration, and a second position corresponding to a cleaning configuration, in which the opening / closing element 4 is in the closed configuration, and vice versa, and wherein the actuator means M comprise a device for moving the printing bar B between the cleaning configuration and the printing configuration.

3. Printing unit according to claim 2 wherein the printing bar B is vertically movable between the first position, located below and corresponding to the printing configuration, and the second position, located above and corresponding to the cleaning configuration.

4. Printing unit according to one of claims 2 or 3 wherein the driving device comprises a motor operatively connected to the printing bar B.

5. Printing unit according to one of the preceding claims wherein the actuator means M comprise an elastic or spring means operatively connected to the opening / closing element 4 and cooperating with the movement device, said elastic means being configured to actuate the opening / closing element 4 between the open configuration and the closed configuration.

6. Printing unit according to claim 1 wherein the actuator means M comprise movement means configured to move the opening / closing element 4 away from the dispensing plane P, to obtain the open configuration, and towards the dispensing plane P, to obtain the closed configuration.

7. Printing unit according to claim 6 wherein the movement means comprise sliding means, configured to move the opening / closing element 4 away from and towards the dispensing plane P.

8. Printing unit according to claim 6 wherein the movement means comprise rotation means, configured to rotate the opening / closing element 4 between the closed configuration in the vicinity of the dispensing plane P and the open configuration, away from the dispensing plane P, and vice versa.

9. Printing unit according to at least one of the preceding claims in which the opening / closing element 4 has a surface S, in use at least partially positioned in correspondence with the dispensing plane P of the printing bar B when the opening / closing element 4 is actuated in the closed configuration; 10. Printing unit according to the preceding claim wherein the opening / closing element 4 comprises two or more surfaces S which can be independently positioned in correspondence with the dispensing plane P of the printing bar B when the opening / closing element 4 is actuated in the closed configuration.

11. Printing unit according to one of claims 9 or 10 wherein the opening / closing element 4 comprises at least one sheet of flexible material.

12. Printing unit according to at least one of the preceding claims wherein the printing block 20 and the cleaning block 30 are mutually movable relative to each other.

13. Cleaning method for a printing unit 10 comprising: a printing block 20 comprising a printing bar B having a plurality of nozzles N operatively connected to a shutter element included in said printing bar B, and implemented between: a non-clogging configuration, to allow ink delivery in a delivery direction Y to define, below said printing block 20, an ink delivery plane P;and a shut-off configuration, to prevent ink dispensing in the dispensing direction Y, a cleaning block 30 having: at least one opening / closing element 4 actuated between an open configuration to allow ink dispensing by the nozzles N, and a closed configuration to at least partially prevent ink dispensing by the nozzles N, actuator means M operatively connected to the opening / closing element 4 and configured to actuate the opening / closing element 4 between the open configuration and the closed configuration, and vice versa when the shut-off element is in the shut-off or non-shut-off configuration; 71 .S0721.12.IT.196 Ing. Giovanni Casadei (Register no. 1195 B) characterised by comprising the phases of: Preparing the printing block 20; Preparing the cleaning block 30 comprising the opening / closing element 4 in the open configuration;5. Actuate, by means of the actuator means M, the opening / closing element 4 from the open configuration to the closed configuration; Perform a cleaning cycle of one or more nozzles N included in the printing bar B of the printing block 20; Actuate the opening / closing element 4 from the closed configuration to the open configuration at the end of the cleaning cycle.