Printing unit and cleaning method

Abstract

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 comprised in said printing bar B, and actuated between: - a non-shut configuration, to enable the delivery of ink in a delivery direction Y in order to define, below said printing block 20, an ink delivery plane P; and - a shut configuration, to prevent the delivery of ink in the delivery direction Y; characterised in that it comprises a cleaning block 30 having at least one opening / closing element 4 that can be actuated between an open configuration to enable the delivery of ink by the nozzles N and a closed configuration to at least partly prevent the delivery 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 a shut or non-shut configuration.

Description

[0001] TRANSLATION (RULE 12.3) 10 October 2025

[0002] 1

[0003] PRINTING UNIT AND CLEANING METHOD

[0004] The present invention relates to a printing unit and a cleaning method of said printing unit.

[0005] The present invention finds advantageous application in the field of ink-jet printing, in particular, for slab-like products; a preferred but not exclusive application of the present invention relates to ink-jet printing for slab-like products of the ceramic sector, such as tiles and slabs.

[0006] When decorating substrates by ink-jet printing, one or more printing bars may be employed to deliver a plurality of inks, so as to obtain the desired decorative effects.

[0007] Printing bars for ink-jet decoration are known in the art and typically comprise one or more printheads, provided with ink delivery nozzles, connected to an ink tank by means of a supply line; furthermore, if the printheads are of the recirculating ink type, such 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 provided to each head and made available for printing operations; through the recirculation line, the ink can return to the tank and be advantageously kept moving, avoiding undesired aggregation or drying phenomena given by the stasis of the ink for a prolonged time.

[0008] Sometimes, however, one or more heads inside a printing bar may suffer malfunctions, mainly at the expense of the nozzles: the nozzles, due to their three-dimensional conformation having a progressive section narrowing, may, for example, suffer clogging due to an ineffective movement of the ink by the recirculation system, or due to the unwanted entry into the head of air coming from the surrounding environment, which air determines the drying of the ink.

[0009] A consequence of the malfunction of one or more printheads inside a printing bar is that the pattern printed on the substrate has unprinted lines at the clogged nozzles and, consequently, a decoration which does not meet the decorative standards required for that object. Cleaning methods for clogged nozzles are known in the art, comprising the steps of:

[0010] -interrupting the flow of ink, turning off the printing unit;

[0011] -removing the damaged printhead(s);

[0012] -bringing the damaged printhead(s) to a separate seat, where specific operations occur, called regeneration operations, aimed at restoring the functionality of the head, where possible;

[0013] -replacing the damaged head(s) with a new head(s) of the same type, if available.

[0014] However, this method is expensive, as it involves replacing the malfunctioning head(s); furthermore, such a method requires that the printing bar remains inoperative for the time necessary to remove the heads and perform the replacement operations of said heads. In conclusion, this method is time-consuming and expensive.

[0015] Alternatively, a further cleaning method for clogged nozzles is known in the art, comprising the steps of:

[0016] -positioning an ink collection tray below the printing bar;

[0017] -starting a purge procedure during which the ink is put under pressure and forced under pressure through the nozzles, until possibly expelling the clogging created.

[0018] Also in this case, the cleaning method has limits: firstly it is not necessarily decisive and the set pressure may not be sufficient to free the clogged nozzles; moreover, when decisive, the method implies the consumption of a considerable amount of ink, which is collected in the collection tray, but which cannot be introduced into the tank again, as it came into contact with pollutants, for example solid particles.

[0019] An object of the present invention is to provide a printing unit and a cleaning method for said printing unit capable of overcoming the obvious limitations of the prior art.

[0020] In particular, an object of the present invention is to provide a printing unit and a cleaning method for said printing unit capable of restoring the operation of the nozzles quickly and efficiently, limiting the interruption of the printing operations as much as possible.

[0021] A further object of the present invention is to offer a printing unit and a cleaning method for said printing unit capable of avoiding unnecessary wastes of ink.

[0022] Additional features and advantages of the present invention will become more apparent from the description that follows, provided purely by way of illustration and not limitation, of several embodiments illustrated in the appended figures, in which:

[0023] -Figure 1 shows a front view of a printing unit comprising a printing block in print configuration;

[0024] -Figure 2 shows a front view of the printing unit of Figure 1 in which the printing block is in a cleaning configuration;

[0025] -Figure 3 shows an isometric view from below of the printing unit of Figure 1 ;

[0026] -Figure 4 shows an isometric view from below of the printing unit of Figure 2;

[0027] -Figure 5 shows an isometric view from above of the printing unit of Figure 1 ;

[0028] -Figure 6 shows an isometric view from above of the printing unit of Figure 2;

[0029] -Figure 7 shows an isometric view from below of a printing unit according to the present invention, in a second embodiment, in print configuration;

[0030] -Figure 8 shows an isometric view from below of a printing unit according to the present invention, in a second embodiment, in cleaning configuration.

[0031] A printing unit according to the present invention is indicated by the reference number 10.

[0032] In fact, the first object of the present invention is a printing unit 10 comprising a printing block 20 and a cleaning block 30.

[0033] With reference to Figures 1 -6, the printing block 20, in detail, comprises a printing bar B having a plurality of nozzles N for delivering ink in a delivery direction Y to define, below said printing block 20, an ink delivery plane P. Typically, the delivery direction Y is perpendicular to the ink delivery plane P and the ink is released from the nozzles N by dripping from the printing bar B and, in particular, from the nozzles N towards a substrate to be decorated.

[0034] In fact, the printing bars B of the known art typically comprise a plurality of printheads, each configured to deliver a type of ink in the delivery direction Y on a substrate, for example, but not exclusively a slab-like substrate such as a tile or a ceramic slab.

[0035] Preferably, each printing bar B or printhead, comprising said plurality of nozzles N, is connected to one or more ink tanks through a respective supply line, configured to supply the printing bar B or the printhead with a type of ink taken from a tank.

[0036] Furthermore, preferably, each printing bar B or printhead comprises one or more recirculation lines, configured to return the ink not delivered by the nozzles N to the respective tank.

[0037] The nozzles N of the printing bar B are operatively connected to a shutter element comprised in said printing bar B: the shutter element can be actuated firstly in a non-shut configuration, to enable the delivery of ink in the delivery direction Y, defining, below the printing bar B, the delivery plane P of the ink.

[0038] The shutter element can secondly be actuated in a shut configuration, to prevent the delivery of ink in the delivery direction Y. That is, when the shutter element is actuated in the shut configuration, ink delivery from the delivery plane P in the delivery direction Y does not occur.

[0039] The shutter elements are, for example, actuated between the shut configuration and the non-shut configuration repeatedly and at a predetermined frequency in order to generate ink drops of predetermined dimensions and subsequently delivered by the nozzles N in the delivery direction Y, so that they are deposited on the substrate to be decorated. The shutter element preferably comprises a plurality of mechanical or electro-mechanical actuators, each operatively connected to one or more nozzles N and adapted to assume the shut and non-shut configuration at said nozzle N or said plurality of nozzles N to which it is operatively connected.

[0040] Mechanical actuators of the type known in the art comprise piezoelectric actuators that assume the shut or non-shut configuration in response to electrical-type operating commands.

[0041] Even more preferably, the operating commands are sent by a control system integrated with the printing block 20 and communicating with each shutter element, mechanical actuator and / or piezoelectric actuator, so as to obtain the shut or non-shut configuration on a part or on all the nozzles N comprised in the printing bar B. That is, each shutter element can be independently actuated between the shut configuration and the non-shut configuration.

[0042] The printing unit 10 according to the present invention further comprises the cleaning block 30, intended, as will be seen below, to perform cleaning operations on the printing block 20.

[0043] That is, the cleaning block 30 is configured to allow the partial or total cleaning of the printing block 20 and, in particular, of the printing bar B and, even more in detail, of one or more nozzles N during repair or maintenance operations.

[0044] The cleaning block 30 comprises at least a first opening / closing element 4 and one or more actuator means M of said opening / closing element 4. The actuator means M can be operatively connected to the opening / closing element 4 and / or to the printing bar B, causing, directly or indirectly, the actuation of the opening / closing element 4 between an open configuration and a closed configuration.

[0045] In detail, the opening / closing element 4, in detail, can be actuated between the open configuration, in which it enables the delivery of ink by the nozzles N, and the closed configuration, in which it at least partly prevents the delivery of ink by the nozzles N.

[0046] That is, in the open configuration, the opening / closing element 4 is actuated so as to enable one or more nozzles N belonging to the printing bar B to deliver ink in the delivery direction Y from the delivery plane P (Fig.1 , Fig.3, Fig.5). Conversely, in the closed configuration, the opening / closing element 4 is actuated so as to prevent one or more nozzles N belonging to the printing bar B from delivering ink in the delivery direction Y from the delivery plane P (Fig.2, Fig.4, Fig.6).

[0047] The opening / closing element 4 can be actuated in different manners, corresponding to different embodiments of the present invention, illustrated in the following paragraphs.

[0048] The actuator means M are operatively connected to the opening / closing element 4 and / or to the printing bar B and are configured to actuate the opening / closing element 4 between the open configuration and the closed configuration, and vice versa. In particular, the actuator means M are configured to actuate the opening / closing element 4 between the open configuration and the closed configuration, and vice versa, when the shutter element of each nozzle N is in a shut or non-shut configuration.

[0049] Preferably, the actuator means M of the opening / closing element 4 operate independently of the shutter element of each nozzle N.

[0050] In other words, at least the following four operating modes can be identified, defined by the open and closed configurations of the opening / closing element 4 and the shut and non-shut configurations of the shutter element, and by their combinations.

[0051] In detail, the opening / closing element 4 can be actuated in the open configuration when the shutter element of each nozzle N is in a shut configuration or when the shutter element of each nozzle N is in a nonshut configuration, identifying a first and a second operating mode.

[0052] In the first operating mode, in which the opening / closing element 4 is in the open configuration and the shutter element is in the shut configuration, the delivery of ink through the nozzles is prevented by the shutter element: said delivery can be prevented or interrupted or stopped for a more or less prolonged time, depending on needs. For example, during a decoration operation of a substrate the opening / closing element 4 is maintained in an open configuration and the shutter element is actuated in the shut configuration, for example, when the delivery of a type of ink on a substrate or on a portion thereof is not required.

[0053] In the second operating mode, i.e., with the opening / closing element 4 in the open configuration and the shutter element in the non-shut configuration, the nozzles N operatively connected to said shutter can deliver ink in the delivery direction Y: this allows not only the decoration of the substrate to be decorated, but also operations of discharging the ink present in a head and its collection in a containment tank, for particular process needs.

[0054] Furthermore, by maintaining the opening / closing element 4 in the open configuration and repeatedly actuating the shutter element between the shut and non-shut configuration, at a predetermined frequency, it is possible to deliver ink drops of predetermined optimal dimensions on a substrate and dependent, for example, on the composition, consistency and viscosity of the ink released from the printing bar B.

[0055] Furthermore, the opening / closing element 4 can be actuated in the closed configuration when the shutter element of each nozzle N is in the shut configuration or when the shutter element of each nozzle N is in the nonshut configuration, identifying a third and a fourth operating mode.

[0056] In the third operating mode, in which the opening / closing element 4 is in the closed configuration and the shutter element is in the shut configuration, no ink is delivered by the nozzles N in the delivery direction Y. Thereby, the opening / closing element 4 operates as a second barrier to prevent the delivery of ink.

[0057] In the fourth operating mode, i.e., with the opening / closing element 4 in the closed configuration and the shutter element in the non-shut configuration, the opening / closing element 4 operates as the only barrier to prevent the ink from being delivered in the delivery direction Y.

[0058] Furthermore, it is possible to actuate the shutter element in shut and nonshut configuration, repeatedly and at a predetermined frequency, keeping the opening / closing element 4 in the closed configuration.

[0059] 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.

[0060] In fact, for example, when a printing bar B or a portion thereof is affected by the opening / closing element 4 actuated in the closed configuration, the ink, forced inside the nozzles N, can be recirculated directly in the recirculation line without being delivered and / or can be stirred by means of repeated activations of the shutters to remove air bubbles present in the ink and / or can be stirred, always through repeated activations of the shutters, to break, move or remove agglomerates of settled and solidified ink.

[0061] Further details regarding cleaning, repair or maintenance operations will be provided below.

[0062] Advantageously, thanks to the opening / closing element 4 actuated by the actuator means M, the printing unit 10 according to the present invention is capable of delivering ink, obtaining both the decoration of a substrate or the discharge of ink from the printing bar B, and of interrupting the delivery of ink quickly and efficiently, in order to allow maintenance and cleaning operations or intervention operations following failures.

[0063] Consequently, not only the printing and ink discharge operations, but also the aforesaid maintenance, cleaning and intervention operations can be advantageously performed while the printing bar B is located at the printing unit 10: in other words, unlike the devices of the prior art, the maintenance, cleaning and intervention operations can be performed without removing the printing bar B from the printing unit 10.

[0064] Advantageously, the printing unit 10, comprising the printing block 20 and the cleaning block 30, is therefore versatile in operation. Finally, the printing unit 10 advantageously allows to carry out cleaning, maintenance and intervention operations quickly and efficiently.

[0065] Preferably, the printing block 20 or the printing bar B and the cleaning block 30 of the printing unit 10 according to the present invention are mutually movable with respect to each other. In other words, it is possible to identify a relative motion between the printing block 20 or the printing bar B and the cleaning block 30 inside the printing unit 10 according to the present invention.

[0066] In other words, the printing block 20 or the printing bar B are movable, while the cleaning block 30 is fixed; alternatively, the printing block 20 is fixed, while the cleaning block 30 is movable; still alternatively, both the printing block 20 or the printing bar B, and the cleaning block 30 are movable, for example along a support frame.

[0067] Preferably, the printing bar B is movable along the support frame 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 print configuration, the opening / closing element 4 is actuated in the open configuration, to enable the delivery of ink in the delivery direction Y to make the decoration on a substrate. Preferably, when the printing block 20 is in the cleaning configuration, the opening / closing element 4 is actuated in the closed configuration, to allow carrying out cleaning, maintenance or repair operations of the printing bar B, the printhead or the nozzles N.

[0068] In detail, and even more preferably, the printing bar B is vertically movable along the support frame between the first position, positioned below and corresponding to the print configuration (Fig.1 , Fig.3, Fig.5), and the second position, positioned above and corresponding to the cleaning configuration (Fig.2, Fig.4, Fig.6).

[0069] Therefore, when the printing bar B is positioned below, a substrate, positioned below it or in transit on a conveyor positioned below it, can be decorated by the delivery of ink from the nozzles N. Conversely, when the printing bar is positioned above and the opening / closing element 4 is actuated in the closed configuration, the substrate, placed below it or in transit on a conveyor placed below it, is only partially affected or is not affected by the delivery of ink from the nozzles N, which are at least partially closed by the opening / closing element 4.

[0070] In the following paragraphs, the components of the printing unit 10 according to the present invention will be detailed: in particular, some nonexclusive embodiments of the opening / closing element 4 and of the actuator means M comprised in the printing unit 10 according to the present invention will be explained.

[0071] In a first embodiment of the printing unit 10, the cleaning block 30 comprises an opening / closing element 4 having a surface S, in use at least partially positioned at the delivery plane P of the printing bar B, when the opening / closing element 4 is actuated in the closed configuration.

[0072] The surface S of the opening / closing element 4 is therefore shaped so as to prevent at least partially the outflow of ink from the nozzles N. The surface S can be, for example but not exclusively, placed against the nozzles N and, in particular, against a respective outflow opening of the ink, physically preventing the outflow of the ink. The surface S, in still other words, placed abutting the nozzles N and, in particular, the respective ink openings, acts as a physical barrier, preventing the ink from being delivered in the delivery direction Y.

[0073] Preferably, but not exclusively, the surface S is flat.

[0074] The surface S can have smaller dimensions than those identified by the printing bar at the delivery plane P: in this case, the surface S, actuated in the closed configuration, allows to prevent the outflow of ink from a part of the nozzles N comprised in the printing bar B. Consequently, for a plurality of nozzles N, affected by the surface S, the delivery of ink is not allowed and for another plurality of nozzles N, not affected by the surface S, the delivery of ink is allowed. Alternatively, the surface S can have dimensions at least equal to or greater than those identified by the printing bar at the delivery plane P: in this case, the surface S, actuated in the closed configuration, allows to prevent the outflow of ink from the totality of nozzles N comprised in the printing bar.

[0075] Still alternatively, the opening / closing element 4 can have two or more surfaces S, which can be independently actuated by the actuator means M from the open configuration to the closed configuration and each shaped to prevent the outflow of ink from a respective plurality of nozzles N belonging to the printing bar B.

[0076] That is, and advantageously, the cleaning block 30 comprising the plurality of surfaces S allows to selectively block the outflow of ink from different portions of the same printing bar, allowing maintenance operations and targeted cleaning and repair operations.

[0077] Intuitively, the opening / closing element 4 can assume a plurality of configurations and shapes.

[0078] In the preferred embodiment of the printing unit 10 according to the present invention, the opening / closing element 4 comprises at least one sheet of flexible material, shaped to adhere at least partially to the delivery plane P when actuated in the closed configuration. That is, when the actuator means M actuate the opening / closing element 4 in the closed configuration, the flexible sheet is moved at the delivery plane P and is made to adhere to the printing bar B.

[0079] Intuitively, two or more sheets of flexible material can be comprised in the opening / closing element 4.

[0080] Even more preferably, the opening / closing element 4 comprises a sheet of flexible material impermeable to the ink delivered, in order to prevent the ink from permeating through the sheet itself and being released in the delivery direction Y.

[0081] The printing unit 10 according to the present invention comprises, as introduced in the previous paragraphs, the actuator means M configured to actuate the opening / closing element 4 between the open configuration and the closed configuration, and vice versa.

[0082] The actuator means M can be of the manual type or of the automatic type.

[0083] The actuator means M of automatic type can be configured to receive operating commands from the control system and actuate the opening / closing element 4 in an open or closed configuration in response to said operating commands.

[0084] The actuator means M can be of various types, also depending on the type of opening / closing element 4 comprised in the cleaning block 30.

[0085] Different types of actuator means M and different combinations of actuators M can advantageously be employed, as will be described in the following paragraphs.

[0086] In a first embodiment, the actuator means M can comprise a movement device of the printing bar B between the cleaning configuration and the print configuration introduced in the previous paragraphs.

[0087] In particular, the movement device comprises a motor operatively connected to the printing bar B.

[0088] That is, the motor, operatively connected to the printing bar B, is configured to determine the movement of the printing bar B between the print configuration and the cleaning configuration and vice versa.

[0089] Preferably, the motor operatively connected to the printing bar B is configured to determine the movement of the printing bar B vertically, between the first position, positioned below and corresponding to the print configuration, and the second position, positioned above and corresponding to the cleaning configuration, and vice versa.

[0090] Additionally or alternatively, the actuator means M can comprise movement means configured to move the opening / closing element 4 away from the delivery plane P, to obtain the open configuration, and / or towards the delivery plane P, to obtain the closed configuration.

[0091] In the preferred embodiment of the printing unit 10 according to the present invention, the actuator means M comprise elastic means, in particular spring means, operatively connected to the opening / closing element and configured to move the opening / closing element 4 from the open configuration to the 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 printing bar B to allow the transition between the closed configuration and the open configuration of the opening / closing element 4 and to determine the return to the closed configuration of the opening / closing element 4.

[0092] In fact, the preferred embodiment of the printing unit 10 comprises the motor operatively connected to the printing bar B and the spring means operatively connected to the opening / closing element 4 and cooperating with said motor.

[0093] In the cleaning configuration, the printing bar is located above and the opening / closing element 4 is actuated in the closed configuration (Fig.2) by the spring means: the opening / closing element 4 preferably comprises a sheet of flexible material, actuated or maintained substantially horizontal and coplanar with the delivery plane P of the printing bar B. That is, the spring means, at rest, maintain the sheet of flexible material in a substantially horizontal configuration.

[0094] In the transition between the cleaning configuration and the print configuration, the motor moves the printing bar B vertically from the first position, located above, to the second position, located below.

[0095] In the transition from the first to the second position, the printing bar B, moved by the motor, exerts a force on the surface S of the opening / closing element 4 and, consequently, on the spring means, determining the shortening or compression thereof.

[0096] As a result of the further downward movement of the printing bar B and the shortening of the spring means, the opening / closing element 4, in particular the sheet of flexible material, is rotated away from the delivery plane P until it reaches a substantially vertical configuration when the printing bar B reaches the second position corresponding to the print configuration (1 ).

[0097] The movement of the printing bar B vertically upwards, to return to the cleaning configuration, determines the opposite movement of the opening / closing element 4, which returns to the closed configuration, i.e., substantially horizontal, due to the elastic force exerted by the spring elements.

[0098] Alternatively to the preferred embodiment described, the movement means M can comprise one or more types of devices of different type, as will be illustrated in the following paragraphs, as long as they are configured to move the opening / closing element 4 away from the delivery plane P, to obtain the open configuration, and towards the delivery plane P, to obtain the closed configuration.

[0099] In a first alternative embodiment the actuator means M comprise sliding means, configured to move the opening / closing element 4 away from the delivery plane P and towards the delivery plane P.

[0100] In a second alternative embodiment, shown in Figure 7 and Figure 8, the actuator means M comprise rotation means, configured to rotate the opening / closing element 4 between the closed configuration near the delivery plane P and the open configuration, away from the delivery plane P, and vice versa. In this case, the actuator means M comprise rotation means and are operatively connected to an opening / closing element 4, preferably comprising the sheet of flexible material: the actuator means M are therefore hinged to the support frame and determine the rotation of the flexible sheet towards the delivery plane P, in the transition from the open configuration to the closed configuration. Here, the flexible sheet is kept at the delivery plane P, in contact with the nozzles N, to create a barrier adapted to prevent the outflow of ink from the nozzles N, for a cleaning time: the cleaning time is variable depending on the cleaning, maintenance or repair operation which is intended to be carried out. Then the actuator means M, after the cleaning time, determine the rotation of the flexible sheet away from the delivery plane P, from the closed configuration to the open configuration, and the nozzles N of the printing bar B can again deliver ink.

[0101] The actuator means M of the sliding type or comprising rotation means can also be cooperating with the movement device of the printing bar B comprising the motor, of the type described in the previous paragraphs.

[0102] In conclusion, the printing unit 10 according to the present invention is capable of both delivering ink, decorating a substrate, and interrupting the supply of ink quickly and efficiently, allowing the execution of cleaning, maintenance or repair operations. Advantageously, the cleaning, maintenance or repair operations can be performed without removing the printing bar B from the printing unit 10, simplifying said operations and shortening the time necessary for their completion.

[0103] Advantageously, consequently, the cleaning, maintenance or repair operations can be carried out without requiring the intervention of an operator for the removal of a printhead belonging to the printing bar B from the printing unit 10 and the subsequent repositioning of the same head at the printing bar B or a different head at the printing bar B in the printing unit 10.

[0104] As anticipated in the preceding paragraphs, when the opening / closing element 4 is actuated in the closed configuration, the ink is not delivered in the delivery direction and the printing bar B or the printheads or the nozzles N affected by the opening / closing element 4 actuated in the closed configuration can be subjected to cleaning, maintenance and repair operations.

[0105] In fact, a second object of the present invention is a cleaning method for a printing unit 10 comprising a printing block 20 and a cleaning block 30.

[0106] The printing unit 10, printing block 20 and cleaning block 30 are preferably of the type described in the previous paragraphs.

[0107] The method according to the present invention comprises, in particular, the steps of:

[0108] Preparing the printing block 20; Preparing the cleaning block 30 comprising the opening / closing element 4 in the open configuration;

[0109] Actuating, by means of the actuator means M, the opening / closing element 4 from the open configuration to the closed configuration;

[0110] Carrying out a cleaning cycle to clean one or more nozzles N comprised in the printing bar B of the printing block 20;

[0111] Actuating the opening / closing element 4 from the closed configuration to the open configuration at the end of the cleaning cycle.

[0112] The steps are listed in a non-binding order and, therefore, can be performed according to a different succession of steps. Furthermore, further operating steps are not excluded from the method according to the present invention.

[0113] In the step of Preparing the printing block 20, for example, the printing block 20 can be moved from the first position, located below and corresponding to the print configuration, to the second position, located above and corresponding to the cleaning configuration.

[0114] In the step of Actuating, by means of the actuator means M, the opening / closing element 4 from the open configuration to the closed configuration, the opening / closing element 4, preferably the sheet of flexible material, is rotated towards the delivery plane P until it is in contact with the nozzles N of the printing bar B.

[0115] The opposite rotation of the flexible sheet is, conversely, performed by the actuator means M during the step of Actuating the opening / closing element 4 from the closed configuration to the open configuration at the end of the cleaning cycle.

[0116] Different types of cleaning cycles can be performed during the step of Carrying out a cleaning cycle of one or more nozzles N comprised in the printing bar B of the printing block 20. In fact, the term cleaning cycle means, in a broader sense, one or more among cleaning operations of the nozzles N, maintenance operation of the printing bar B or of the nozzles N, repair operations of the nozzles N following malfunctions and / or other similar operations.

[0117] Among the types of cleaning cycles that can be carried out, the cleaning method for ink-jet printheads, the subject of patent application number 102023000023100 in the name of the same Applicant and briefly reported below, is particularly advantageous. Cleaning cycles or types of operations other than the one reported are not intuitively excluded.

[0118] The preferred, but not exclusive, cleaning cycle carried out by the printing unit 10 comprises the following steps:

[0119] Interrupting the introduction of ink into the supply line of the printing bar B or the printhead;

[0120] Introducing the ink into the recirculation line at a predetermined flow rate, defining a recirculation operating mode;

[0121] Maintaining the recirculation operating mode for a predetermined cleaning time.

[0122] Furthermore, said preferred cleaning cycle can comprise the step of

[0123] - Starting from an internal pressure value of the printing bar B or the printheads, varying said internal pressure value.

[0124] In particular, starting from an internal pressure value of the printing bar B or of the printheads, the cleaning cycle involves decreasing said internal pressure value to create an internal depression such as to keep the opening / closing element 4 in a closed configuration, in contact with the nozzles N of the printing bar. This step is particularly effective if the opening / closing element 4 comprises a flexible sheet.

[0125] In addition or alternatively to the step of varying the internal pressure, the cleaning cycle can comprise the step of:

[0126] Wetting the surface S of the opening / closing element 4.

[0127] The step of wetting the surface S precedes or is carried out simultaneously with the positioning of the surface S of the opening / closing element 4 in contact with the nozzles N or in other words, during the actuation of the opening / closing element 4 in the closed configuration.

[0128] By wetting the surface S of the opening / closing element 4, the adhesive capacity of the opening / closing element 4 with respect to the printing bar B is improved. This step is particularly advantageous if the opening / closing element 4 comprises the sheet of flexible material,

[0129] The cleaning cycle can further comprise the step of

[0130] Changing the value of the predetermined ink recirculation rate.

[0131] In particular, by increasing the recirculation flow rate, heads obstructed by large elements can be released, moving said obstructing elements.

[0132] Finally, the preferred cleaning cycle can comprise the steps of

[0133] - Moving or further stirring the ink in the recirculation operating mode, for a movement time.

[0134] The movement or stirring of the ink preferably, but not exclusively, occurs through mechanical actuators connected to the nozzles N. In other words, the movement or stirring of the ink can occur by actuating the shutter connected to the nozzles N repeatedly, at a predetermined frequency, between the shut configuration and the non-shut configuration, keeping the opening / closing element 4 in the closed configuration.

[0135] The method according to the present invention advantageously allows to free the nozzles N of the printing bar B from dried ink, unwanted impurities or air bubbles blocking the nozzles N themselves.

[0136] In conclusion, the method according to the present invention advantageously allows to perform a plurality of different cleaning, maintenance or repair cycles, in an effective and versatile manner, keeping a printing bar B inside a printing unit 10, avoiding the removal thereof and reducing the time necessary to solve any problems and failures.

Claims

CLAIMS1. A 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 comprised in said printing bar B, and actuated between: a non-shut configuration, to enable the delivery of ink in a delivery direction Y so as to define, below said printing block 20, an ink delivery plane P; and a shut configuration, to prevent the delivery of ink in the delivery direction Y, characterised in that it comprises a cleaning block 30 having at least one opening / closing element 4 that can be actuated between an open configuration to enable the delivery of ink by the nozzles N and a closed configuration to at least partly prevent the delivery 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 a shut or non-shut configuration.

2. The printing unit according to claim 1 , wherein the printing bar B is movable along a support frame between a first position corresponding to a print 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 a 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. The printing unit according to claim 2, wherein the printing bar B is vertically movable between the first position, located below and corresponding to the print configuration, and the second position, locatedabove and corresponding to the cleaning configuration.

4. The printing unit according to one of claims 2 and 3, wherein the movement device comprises a motor operatively connected to the printing bar B.

5. The printing unit according to one of the preceding claims, wherein the actuator means M comprise an elastic means or a spring 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. The 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 delivery plane P to obtain the open configuration, and closer to the delivery plane P to obtain the closed configuration.

7. The printing unit according to claim 6, wherein the movement means comprise sliding means, configured to move the opening / closing element 4 away from and closer to the delivery plane P.

8. The printing unit according to claim 6, wherein the movement means comprise rotation means, configured to move the opening / closing element 4 in rotation between the closed configuration in proximity to the delivery plane P and the open configuration, away from the delivery plane P, and vice versa.

9. The printing unit according to at least one of the preceding claims, wherein the opening / closing element 4 has a surface S positioned at least partly, during use, at the delivery plane P of the printing bar B when the opening / closing element 4 is actuated in the closed configuration.

10. The printing unit according to the preceding claim, wherein the opening / closing element 4 comprises two or more surfaces S which can be independently positioned on the delivery plane P of the printing bar B when the opening / closing element 4 is actuated in the closed configuration.

11. The printing unit according to one of claims 9 and 10, wherein the opening / closing element 4 comprises at least one sheet of flexible material.

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

13. A 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 comprised in said printing bar B, and actuated between: a non-shut configuration, to enable the delivery of ink in a delivery direction Y in order to define, below said printing block 20, an ink delivery plane P; and a shut configuration, to prevent the delivery of ink in the delivery direction Y; a cleaning block 30 having: at least one opening / closing element 4 actuated between an open configuration to enable the delivery of ink by the nozzles N and a closed configuration to at least partly prevent the delivery of ink 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 shutter element is in the shut or non-shut configuration; characterised in that it comprises the steps of:Preparing the printing block 20;Preparing the cleaning block 30 comprising the opening / closing element 4 in the open configuration;Actuating, by means of the actuator means M, the opening / closing element 4 from the open configuration to the closed configuration;Carrying out a cleaning cycle to clean one or more nozzles N comprised in the printing bar B of the printing block 20;Actuating the opening / closing element 4 from the closed configuration to the open configuration at the end of the cleaning cycle.

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