METHOD

The present invention refers , in general , to an inkj et printing unit and to a printing method for cards , for example bank cards , identity documents or the like .

In the art , groups and printing methods for cards are known, for example cards with a CR 80 format or cards according to the ISO 7810 standard, in which a surface of paper is printed after being treated to make the surface more receptive to ink .

These known printing groups and methods have problems regarding quality of the printing process , ease of use for the end user, risks of machine downtime and in general overall ef ficiency of the system .

Obj ect of the present invention is solving the aforementioned prior art problems , by providing an inkj et printing unit for cards and a related printing method which are reliable and economical , and which allow the cards to be printed with a high quality, ease of use , reducing the risk of machine downtime .

The aforementioned and other obj ects and advantages of the invention, as will appear from the following description, are achieved with an inkj et printing unit and a related printing method for cards such as those described in the respective independent claims . Preferred embodiments and nontrivial variations of the present invention are the subj ect matter of the dependent claims .

It is understood that all attached claims form an integral part of the present description .

It will be immediately obvious that innumerable variations and modi fications ( for example relating to shape , dimensions , arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention as appears from the attached claims .

The present invention will be better described by some preferred embodiments thereof , provided by way of non-limiting example , with reference to the attached drawings , in which :

- Figure 1 is a schematic view of an inkj et printing unit for cards according to the present invention; and

Figures 2-4 are views of details of an inkj et printing unit for cards according to the present invention .

Referring to the Figures , the inkj et printing unit 100 for cards 30 according to the present invention comprises :

- a transport system 9 comprising at least one transport device , preferably several independent associated transport devices , which manage several cards at the same time , configured to move the cards 30 through the printing unit 100 and preferably comprising a plurality of side rollers with clutch acting on the edge of the paper 30 and/or a shuttle with air suction, moved for example by a screw motor and comprising a paper presence sensor and a vacuum sensor ; the side rollers allow not to touch the surface of the cards to be printed so as not to contaminate it , while the shuttle includes a surface for supporting the lower part of the cards and a vacuum system that ensures the retention of the cards in position during transport and during treatments ;

- a first inkj et printing head 3 , configured to automatically move between a rest position, in which it is protected from dust and light by a first automatic protection device 4 , and a print position, in which, after having moved the protection device 4 , for example by rotating it , to move it away from the first head 3 , it is brought closer to the paper 30 to print using a pigmented or transparent ink; for example , the first automatic protection device 4 is a movable or rotatable cover so as to move from a position in which it protects the first printing head 3 , in particular the noz zles , to a position in which the protection device 4 is moved away from the first printing head 3 , which is therefore free to move into the print position;

- a second inkj et printing head 5 , configured to move automatically between a rest position, in which it is protected from dust and light by a second automatic protection device 6 , similar to the first automatic protection device 4 , and a printing position, in which it is approached to the paper 30 for printing using a pigmented or transparent ink; the first 3 and the second 5 printing heads work independently from each other and can be activated alternately in order to print in the same area or in di f ferent areas , using the same color or di f ferent colors , allowing to use a second color simultaneously with the first , to make it possible to print two or more elements , each with a di f ferent ink, or combine them to obtain intermediate shades or create a tonal scale .

The devices and systems included in the inkj et printing unit 100 for cards 30 according to the invention are operated by drive means of a known type , comprising for example at least one electric motor, and driven by a control unit , also known, which is also configured to control the advancement speed of the paper 30 in the transport system 9 .

The printing head 3 , 5 is movable so as to adj ust the printing position by moving away and approaching the paper 30 to be printed in order to effectively and automatically calibrate the position with respect to the paper 30 , improving printing precision and reducing defects . The movement of the head in the rest position allows the automatic protection device 4 , 6 and an optional automated cleaning station to be integrated into the inkj et printing unit 100 according to the invention, making it possible to manually clean the noz zles of the printing head 3 , Each automatic protection device 4 , 6 , provided in a preferred embodiment of the inkj et printing unit 100 according to the invention, protects the respective printing head 3 , 5 in the rest position, avoiding contamination of the noz zles of the printing head 3 , 5 with the consequent blocking of the ink output itsel f , reducing printing imperfections and consequent downtime . Furthermore , in an embodiment of the invention which provides for the use of UV-curable ink, which will be explained later, the automatic protection device 4 , 6 also acts as a screen for ambient light , preventing the slow drying process of ink present on the surface of the printing head

3 , 5 when not in use .

The inkj et printing unit 100 for cards 30 according to the invention, in the embodiment which provides for the use of UV-curable ink, further comprises a polymeri zation unit 7 comprising an element for the emission of UV rays , for example a UV lamp, configured to cure the ink printed on the paper 30 so as to cover with the UV rays a polymeri zation area 8 having a width greater than or equal to one side L of the paper 30 , which is perpendicular to the advancement direction of the paper 30 m the transport system 9 so as to polymeri ze the ink on the surface of the paper 30 with only the movement of the paper 30 ; the advancement speed of the paper 30 in the transport system 9 during polymeri zation determines the amount of radiation absorbed by ink, while the emission angle of the radiation by the element for the emission of UV rays , controlled by the control unit , determines the point energy concentration .

The element for the emission of UV rays emits energy at a wavelength, defined by the ink speci fications , of about 400 nm, preferably of 395 nm in standard use .

The polymeri zation unit 7 is movable so as to adj ust its position by moving away from and approaching the paper 30 to be treated to effectively calibrate , preferably automatically, the position of the element for the emission of UV rays with respect to the paper 30 , and comprises means for regulating the intensity of the UV rays , for example ignition means with controlled voltage , and/or means for regulating the optical profile to create wide-range or focused emission windows which allow, together with the regulation of the position, to calibrate the exposure of ink printed on the paper 30 optimally .

During curing, the time between printing ink and curing determines the final print quality based on the time allowed for ink to spread over the paper 30 , amalgamate or mix with ink of other colors , while the intensity of irradiation and the exposure time determine the correct polymeri zation and adhesion to the substrate of the paper 30 on which it is printed .

The inkj et printing unit 100 for cards 30 , in a preferred embodiment of the invention, comprises a surface treatment unit 1 , comprising an element for the surface treatment of the paper 30 , for example an element for the plasma emission, such as a gas flame , an element for the surface treatment with corona ef fect or other known means , for the application of a " receptive" layer, said element for the surface treatment of the paper 30 being configured to treat , with a single linear movement pass of the paper 30 under the surface treatment unit 1 , the surface of the paper 30 to be printed on an area 2 having a width substantially equal to a side L of the paper 30 which is perpendicular to the advancement direction of the paper 30 in the transport system 9 ; the surface of the paper 30 to be printed is treated with only the movement of the paper 30 , while the surface treatment unit 1 remains stationary; in an alternative embodiment of the invention, the surface treatment unit 1 is also mobile .

The treatment of the entire surface of the paper 30 with a single passage with linear movement under the surface treatment unit 1 guarantees full control of the uni formity and intensity of treatment by simply varying the speed of passage of the cards , allowing to carry out a process of simple calibration .

The surface treatment unit 1 is movable vertically to adj ust its position, moving away and approaching the paper 30 to be treated, allowing the plasma application cone to be adapted to the surface of the paper 30 to be treated, to compensate for any di f ferences in thickness of the paper 30 , and vary the intensity of the treatment itsel f .

Preferably, the inkj et printing unit 100 for cards 30 of the invention comprises an air suction and filtering unit 10 positioned next to the surface treatment unit 1 , configured to ef fectively remove air in the treated area 2 , filter and remove contaminants m order to expel clean air .

The air suction and filtering unit 10 makes it possible to secure the process by removing any toxic gases , making the work environment safe . A further option is given by the presence of an extractor to bring air outwards .

Preferably, the inkj et printing unit 100 for cards 30 of the invention comprises a first 11 and a second 12 automatic cleaning systems configured to remove ink residues , dirt particles or contaminants from the surface of the respective first 3 and second 5 printing heads during the dif ferent phases of use , typically before and after each print ; for example , the cleaning system 11 , 12 comprises a deformable element , which can be made of plastic material , which rubs the surface of the head in correspondence with the noz zles to clean it .

The cleaning system 11 , 12 also provides for the possibility of ej ecting "disposable" ink to help detach any residues , replacing it with ink that can be used for printing .

The inkj et printing unit 100 for cards 30 of the invention further comprises a plurality of paper presence sensors , preferably of the electromechanical and vacuum type, controlled by the control unit, to check the presence of the paper 30 in all sections of the printing unit 100, allowing to identify critical issues in the process and to interrupt it in the event of problems that could cause damage.

The inkjet printing unit 100 for cards 30 of the invention can be used individually or with a second group in series to offer printing functionality on both sides of the paper 30.

A preferred embodiment of an automatic protection device 4, 6 and a cleaning system 11, 12 of an inkjet printing unit 100 according to the invention will now be described.

The automatic protection device 4, 6 comprises a shelf 42 movable with respect to a support 52, preferably sliding with respect to the support 52 on guide means 53 in a transverse direction X, preferably perpendicular, with respect to the movement direction Y of the printing head 3, 5, so as to move from the protective position of the printing head 3, 5, in particular of the nozzles, when the head is in the rest position, to the position away from the printing head 3, 5 to allow said head to move freely in the printing position. Preferably, the automatic protection device 4, 6 comprises a tray 41 for protecting the printing head 3, 5, in particular the nozzles, configured to protect it from light and dust and to collect any ink residues, said tray 41 being connected to the shelf 42 so that it moves with the shelf 42 from the protective position of the printing head to the position away from the printing head.

Preferably, the protective tray 41 has dimensions such as to cover the nozzles of the printing head 3, 5 when positioned in the protection position, following the movement of the movable shelf 42, in front of the nozzles of the printing head 3, 5 when this is in the rest position .

Preferably, the cleaning system 11, 12 of the printing unit 100 is connected to the shelf 42 so as to move with it in correspondence with the nozzles of the printing head 3, 5, preferably back and forth along the X direction in correspondence with the nozzles, when the head 3, 5 is in the rest position, and comprises a suction nozzle 43 connected to a hole 44, for example made on the wall of the hole 44, in turn connected for example by means of a tube to a vacuum pump configured to suck through the suction noz zle 43 residual ink from the printing head noz zles , typically before and after each print .

The printing method for cards according to the invention includes the following steps :

- a step in which the paper 30 to be printed is loaded into the inkj et printing unit 100 via the transport system 9 which can handle single or multiple pieces ;

- an optional step in which the paper 30 to be printed is moved by the transport system 9 in the surface treatment unit 1 to receive on the surface to be printed a treatment aimed at cleaning and facilitating printing on the surface of the paper 30 ; preferably, the treatment of the surface of the paper 30 to be printed is performed with a single linear movement passage of the paper 30 under the surface treatment unit 1 ;

- a step in which the paper 30 to be printed is trans ferred by means of the transport system 9 to the first printing head 3 and subsequently to the second printing head 5 , where it is printed using one or two separate and independent colors ; a step in which the first 4 and/or the second 6 automatic protection device is moved away from the first printing head 3 and/or from the second printing head 5 , which is therefore free to move into the print position;

- a printing step in which the first printing head 3 and/or the second printing head 5 automatically moves from the rest position, in which it is protected by the automatic protection device 4 , 6 , in the print position, approaching the paper 30 to be printed; an optional step of ink drying in the polymeri zation unit 7 which polymeri zes the ink printed on the paper 30 ;

- a step of expelling the printed paper 30 from the inkj et printing unit 100 , performed by the transport system 9 .

In a preferred embodiment , the printing method for cards of the invention comprises :

- an optional step, performed at the end of the printing step , in which the first printing head 3 and/or the second printing head 5 moves to the rest position, in which it is protected by the automatic protection device 4 , 6 ; a cleaning step, which is carried out periodically, in which the automatic cleaning system 11 , 12 removes ink residues , dirt particles or contaminants from the surface of the respective first 3 and second 5 printing heads during the dif ferent steps of use , typically before and after each printing stage . Preferably, the steps of the printing method according to the invention are performed without interrupting the movement of the paper 30 between the subsequent steps .

Advantageously, the inkj et printing unit for cards and the printing method of the invention allow printing cards with a high quality, reliably and economically, with ease of use and reducing the risk of machine downtime .