WO2008065222A1

WO2008065222A1 - Self-contained inkjet printing module

Info

Publication number: WO2008065222A1
Application number: PCT/ES2007/000680
Authority: WO
Inventors: José Vicente Tomas Claramonte; Rafael Vicent Abella; Pedro GASSÓ ARCAS
Original assignee: Kerajet, S.A.
Priority date: 2006-11-28
Filing date: 2007-11-26
Publication date: 2008-06-05
Also published as: EP2090439A1; ES2392951T3; EP2090439B1; ES2302634B1; ES2302634A1; EP2090439A4

Abstract

The invention relates to a self-contained inkjet printing module containing print heads (5) for printing the required width in a single passage, said heads including a system for the maintenance, pressurisation and thermal conditioning of the ink used. The number of modules required depends on the number of coloured inks used and the desired print resolution. The module also includes a mechanism which covers the injector plate and collects the ink poured during each draining operation, thereby cleaning said injector plates and preventing the ink from drying. The invention takes the form of an inverted metal T-section (4) to which the print heads (5) are mounted such that the injector plate (1) is exposed. The metal section (4) includes two lower horizontal cylindrical perforations (6) which are interconnected so that a heating liquid can flow therethrough. The section also includes another upper cylindrical perforation (8) for distributing the ink which travels to the print heads (5) through vertical holes (9).

Description

AUTONOMOUS PRINTING MODULE BY INK JET OBJECT OF THE INVENTION

The present invention, as expressed in the description of this specification, refers to an autonomous inkjet printing module which has been specially designed for the construction of inkjet printing machines in which different heads are assembled. Print until you get the print width and number of colors desired. Normally the number of injectors of each head is usually power of two (one, two, four, eight, sixteen, thirty-two, sixty-four, one hundred twenty-eight, etc.), being aligned and evenly distributed in a plane commonly called " nozzle plate ".

When you want to print on each pass a width greater than the separation between the first and last injectors, several heads are put together so that they cover the required width. Since, on the injector plate, before the first injector and after the last one there is an unusable area (without injectors), the heads cannot be placed side by side with the injectors in line and triplet arrangements or overlapping must be used in oblique arrangement, as we will see later in relation to the figures.

This arrangement must be repeated for each of the different inks (colors) used, so that the heads are arranged in different rows.

Each of the heads mentioned needs a system that keeps the plate, where the nozzle holes are housed, in an optimal state of cleanliness so that the print quality is not affected. Normally, these maintenance systems fulfill three basic functions:

- Keep the injector plate clean.

During normal operation of the printheads, ink splashes occur that are a function of the nozzle plate. During the priming and purging processes, ink spills occur that flood the nozzle plate. In addition, the external environment to which the injector plate is exposed causes it to become dirty with dust, threads, etc.

Mainly, two systems are used for cleaning: spatulation and / or blowing, always after an intentional flooding with fresh ink to avoid erosion of the nozzle plate. - Prime lowered injectors.

Normally, the inkjet printheads work by keeping the ink at a lower pressure than the environment, the ink being held in the nozzles by the meniscus formed thanks to the surface tension of the ink.

It happens, with some frequency, that the meniscus of some or some injectors is broken by sudden mechanical and / or hydraulic oscillations. This causes the affected injector (s) to breathe air and descend. To restore damaged menisci, the pressure of the ink is usually caused to be higher than the outside, so that a small amount of ink flows all the way to the nozzle orifice. This pressure increase is made by increasing the ink pressure and / or decreasing the external pressure by vacuum. After performing the described retraction, the injector plate is flooded and must be cleaned as we have already mentioned in the previous point.

- Prevent the ink from drying out. During the normal operation of an inkjet printhead, the ink flows through the nozzle holes so that the ink present in the nozzles always renews and maintains its properties even if it contains some very volatile component , whose evaporation can produce a variation in its properties. The main problem that may occur is that the evaporation of some volatile component, and consequently the increase in the concentration of the other components, causes the viscosity of the ink to reach the nozzles to increase so much.

This is normally avoided by tightly closing and / or keeping the area around the injectors wet with ink. BACKGROUND OF THE INVENTION

There are many patented systems on the market that perform the functions described above. Most of them have for each head used, a concave piece of soft elastomer that is used as a cover to prevent evaporation, to collect the remains of ink and to aspirate when you want to reduce the pressure in the area near the nozzle plate . In addition, these systems usually include a soft elastomer spatula that is used to remove traces of fresh ink that have been deposited on the nozzle plate after an ink purge. When inkjet printing machines are built for printing large formats in a single pass and / or with numerous inks, the number of heads to be installed is increasing to the point that the conventional solutions described above are difficult to build and drive.

DESCRIPTION OF THE INVENTION

In general, the autonomous inkjet printing module, which the invention proposes, includes the inkjet printheads arranged for printing in a single pass of the required width.

This module will include the maintenance system for the installed heads, as well as the pressurization and thermal conditioning system of the ink used. By including, this module, all the elements related to the conditioning of the heads and the ink they use, the construction of a machine is limited to the installation of as many autonomous modules as necessary depending on the number of inks and the resolution desired printing.

The autonomous module proposed by the invention offers a basic structure defined by a metal profile, extruded or machined, with an inverted "T" shaped section in which the printheads are mounted mounted, the plate being exposed from the bottom of injectors. This "T" shaped metal profile has, along its entire length, three cylindrical perforations, two of which are located at the bottom and that communicate with each other to determine a circuit to be traversed by the liquid to the desired temperature of the printing module, the other being - C. _

perforation arranged in the upper part, the three horizontal perforations being and the latter defining a collector or distributor conduit and thermal conditioning of the ink, from which a plurality of vertical holes as heads are to be installed, so that valves can be arranged manuals and tubes that supply the ink at the desired temperature to the printheads.

As we will see later, to supply the ink to the printheads at the appropriate pressure at all times (lower than that of the environment at the time of printing, and higher than that of the environment in the case of purges and primings), it may be used One of the three systems listed below: - In a first system the ink remains in the work tank with a certain level lower than that of the nozzle plates. During the printing phase, the pressurized air and pressure ink inlet solenoid valves remain closed, the tank being connected to the outside, so that the pressure with which the ink reaches the heads, through the distributor, It only depends on the level in the deposit.

As the ink is consumed by the heads, it is necessary to refill the work tank to maintain the level within the limits specified by the head manufacturer. During this refilling operation, the communication solenoid valves of the tank with the outside and the pressure ink inlet remain open, the one of the pressurized air inlet being closed, so that the ink thus flows into the tank without affecting the pressure of The ink on the heads. When it is necessary to increase the pressure for the purges and the primers, the solenoid valves for communication with the outside air and the inlet of the pressurized ink remain closed, and the one for the pressurized air inlet is opened so that said pressure makes the ink flow through the injector holes.

In the second system, during the printing phase, the pressure ink inlet solenoid valve remains closed and direct communication of the tank with the distributor is established. There is a peristaltic pump bypass with the solenoid valve intercalated in this last mentioned duct, which remains stopped, while the solenoid valve is closed, so that the ink pressure in the heads only depends on the level inside the work tank similar to the previous system .

During this refilling operation, the pressure ink solenoid valve is opened and the ink flows into the tank without affecting the ink pressure in the heads thanks to the fact that the tank communicates with the outside.

When it is necessary to increase the pressure for purges and priming, the solenoid valve is closed bypass with the bonba and the peristaltic pump is put into operation so that the air pressure flows the ink through the nozzle holes. East . The system admits that the refilling of the work tank can be done at the same time as the purges are carried out.

- In the third system, during the printing phase the pressure ink inlet solenoid valve remains closed and it is a centrifugal pump that can push the ink from the tank to the distributor, so that the ink pressure in the heads alone It depends on the level inside the work tank, the centrifugal pump being stopped since the ink flows through the channels of the impeller in the stop condition. During this refilling operation, the pressure ink inlet solenoid valve is opened so that the ink flows into the tank without affecting the ink pressure in the heads, thanks to the fact that the tank communicates with the outside. When it is required to increase the pressure for the purges and primers, the centrifugal pump is started so that the air pressure flows the ink through the injector holes. This system also admits that the filling of the work tank is done at the same time as the purges are carried out.

The autonomous inkjet printing module also includes a mechanism that is capable of covering the nozzle plate and being able to collect the ink that is poured into each purge and leave the nozzle plate as clean as possible to be able to print with good quality. This mechanism must also be able to prevent the ink from drying out when the module is not working.

The invention provides two solutions for the part that covers the nozzle plate, using one solution or another depending on the ink:

- In the first solution the print head is protected by fins that leave only a small slot for the nozzles visible. Between plates and fins an absorbent sponge sheet is inserted whose function is to collect the drops of ink that splash on the nozzle plate. This lengthens the period of time between cleanings. The remaining ink is collected by means of a concave lid that has another absorbent sponge in its cavity. During the cleaning process, said lid acquires the closed position and after purging, the remaining ink is drawn through a lower conduit in said lid. The air that in this operation is sucked by the slits around the lid dries the absorbent sheet.

In the second solution, the nozzle plate is completely uncovered and it is the concave lid that has absorbed sponges at the ends of its cavity that collect the excess ink and clean a mobile spatula at the end of each path, as we will see later in relation to the figures. The movement of the covers to acquire the working and resting position is obtained with the combined movement of displacement and rotation of some vertical axes to which different cranks linked to said covers are solidarity. To facilitate the understanding of the features of the invention and as an integral part of this specification, some sheets of drawings are attached in whose figures, for illustrative and non-limiting purposes, the following has been represented: BRIEF DESCRIPTION OF THE DRAWINGS

Figure la.- Shows the schematic arrangement of the inkjet printheads, for single-pass printing of the required width, according to a configuration in which the print width is increased while maintaining the native resolution of the printhead.

Figure Ib.- It is a schematic view similar to figure la, according to a configuration in which it has been increased print width and print resolution (by a factor equal to / s α).

Figure 2a.- Shows the head structure of figure la, repeated for each of the different inks (colors) used, arranged in different rows.

Figure 2b.- It is a view similar to that of Figure 2a in which the heads are repeated for each of the different inks. Figure 3. - It is a schematic cross-sectional view of the basic structure of the autonomous inkjet printing module according to the invention.

Figure 4, - It is a scheme of a first ink supply system to the printheads, according to the invention.

Figure 5.- It is a scheme of a second ink supply system to the printheads, according to the invention. Figure 6.- It is a diagram of a third ink supply system to the printheads according to the invention.

Figure 7.- It shows in two positions a) and b) the printhead and its closing lid in explosion and applied against the head, respectively, according to a first solution.

Figure 8.- It is a view similar to Figure 7, according to a second solution.

Figure 9, - It is a schematic view in longitudinal section, of that shown in Figure 8.

Figure 10. - It is a schematic view in longitudinal section similar to Figure 3 but including the protective caps and head cleaning, as well as its drive system, in the rest position.

Figure 11.- Shows in three positions a), b) and c) the sequence of movements to move from the rest / cleaning phase of Figure 10 to that of work or printing.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the numbering adopted in the figures and especially in relation to figures la and Ib, we can see schematically different plates of injectors 1 arranged in two different ways to print in each pass a width greater than that occupied by the injectors, remaining overlapping areas so that the injectors 2 can make a uniform sweep. In the figure the original resolution is maintained and in Figure Ib the resolution is increased since the scan lines are closer to each other, specifically according to a factor corresponding to l / sine α.

In figures 2a and 2b the repetition of these same structures of figures la and Ib is seen for each of the colors of inks used, four in the case shown.

In figure 3 you can see the basic structure of the printing module, referenced in general with the number 3 and materialized by the extruded or machined metal profile 4 in the form of an inverted "T", provided with mounting windows for the print heads 5 with its nozzle plates 1.

Reference 6 designates two of the three horizontal longitudinal perforations, the lowest, which communicate with each other with step 7 at one end, for circulation of the liquid at the desired temperature. The remaining drilling, referenced with 8 and plugged by the other end, acts as a distributor and is traversed by the ink at the temperature of the block, leaving the vertical ducts 9 to the respective printheads 5 through the valves 10 and tubes 11.

With special reference to Figure 4, the ink is supplied to the heads 5 at the correct pressure, from the tank 12 in which the level is maintained at a certain level 13 with respect to the nozzle plates 1, reaching the distributor 8. Reference 14 designates the pressurized air inlet controlled by solenoid valve 15 and reference 16 the pressurized ink inlet when solenoid valve 17 is open. During the printing phase the solenoid valves 15 and 17 are closed and the solenoid valve 18 that communicates with the outer line 19 is open. The pressure with which the ink reaches the heads through the distributor only depends on the level in the reservoir 12.

To fill the tank 12 and maintain its level within the limits specified by the manufacturer of the heads, during the filling operation the solenoid valves 18 and 17 remain open and the 15 closed so that the ink flows into the tank without affecting the ink pressure in the heads. For purges and primers, solenoid valves 18 and 17 remain closed and 15 open.

In the second system, schematically depicted in Figure 5, the ink 12 receives pressure ink through the conduit 16 through the solenoid valve 17. The solenoid valve 20 is bypass mounted with the peristaltic pump 21. During the printing phase the solenoid valve 17 remains closed, solenoid valve 2 open and the peristaltic pump 21 stopped. The pressure of The ink in the heads only depends on the level inside the work tank 12.

During the refilling operation, the solenoid valve 17 is opened so that the ink flows into the tank without affecting the pressure of the ink in the heads thanks to the duct 19 communicating the tank with the atmosphere.

When the pressure for purging and priming increases, the solenoid valve 20 is closed and the peristaltic pump 21 is started, the ink flowing through the injector holes.

In relation to Figure 6 where the third ink supply system to the printheads is shown schematically, the solenoid valve 17 remains closed and the centrifugal pump 22 is stopped, so that the ink pressure in the heads only depends of level 13 inside the work tank 12. In this system, the ink flows through the channels of the centrifugal pump impeller stopped. For filling, the solenoid valve 17 is opened so that the ink flows into the reservoir 12 as it is communicated with the outside through the conduit 19.

When it is necessary to increase the pressure to carry out purges and priming, the centrifugal pump 22 is put into operation. This system also supports simultaneous filling with the purges.

In figure 7 positions a) and b) the printhead 5 protected by the fins 23 can be seen leaving only the small groove 24 exposed. Between the bottom face of the nozzle plate 1 and the fins 23 the absorbent sponge 25 is arranged .

Reference 26 designates the concave lid with another absorbent sponge 27 which is the one that collects the ink surplus. During the cleaning process, the cover 26 goes to the position b) of figure 7 and after the purge the excess ink is sucked through the conduit 28, at the same time as the air sucked by the slits 29 dries the absorbent sheet 25. The mound 30 formed by pressing the sponge 27 on the groove 24 helps to remove the drops from the injector plate 1.

In the second solution, according to what figures 8 and 9 schematically show, the nozzle plate is completely uncovered when the printhead 5 is mounted on the window in the holder or profile 4.

Now, the concave lid 26 has absorbent sponges 31 housed at the ends of its cavity to collect the remaining ink, and also clean the spatula referenced with 32 at the end of each stroke. During the cleaning process, the lid goes to its position and after the purge the excess ink is drawn through the conduit 28. Subsequently, the spatula 32 collects the remaining drops in the injector plate in a longitudinal movement, depositing it on the extreme sponges 31. As can be seen, the spatula 32 can oscillate freely on the cylinder 33 in which it is mounted, which cylinder is attached to the rod 34 so that when the latter moves, the spatula can be tilted (rotating on the cylinder 33) so that it can slide more smoothly over the injector plate.

After describing the typologies of the cover that covers the nozzle plate, we will see how they are installed in the printing module and how these pieces move from the rest and cleaning position to the printing position. Figure 10 shows that the Heads 5 are installed on the profile 4 in the form of an inverted "T" in two parallel rows. Therefore the caps must also have this configuration of two parallel rows. In the scheme of figure 10 the caps of each row are constructed in a single piece as bars and are referenced with the number 35. They have a longitudinal conduit 36 that communicates the ink outlets of each. Each of the bars 35 joins several cranks 37 perpendicular to two vertical shafts 38 that have the possibility of turning, raising and lowering. The different cranks 37 cause the rotation of the shafts 38 to become a parallel displacement of the bars 35. In this figure 10 the system is shown in the rest / cleaning position in which all the actions aimed at priming the injectors and clean the nozzle plate.

To move from the rest / clean position to the work position, the following sequence of movements is performed, as shown in Figure 11 in three positions a), b) and e).

The vertical axes 38 rotate in the supports 39 and slide down starting from the position shown in figure 10, as shown in position a) of figure 11.

Then, the vertical shafts 38 rotate 90 ° by moving the bars 35 parallel to the location shown in position b). When the vertical axes 38 slide upwards as shown in position c) the working position is acquired.

Claims

1.- AUTONOMOUS INK JET PRINTING MODULE, which includes the printheads for single-pass printing of the required width, and a maintenance system for the installed heads, as well as a pressurization and thermal conditioning system of the ink used, there are as many modules as necessary depending on the number of inks and the desired print resolution, also including a mechanism capable of covering the nozzle plate and collecting the ink that is poured into each purge leaving said nozzle plate as clean as possible, also preventing the ink from drying out when the module is not in operation, characterized in that it is constituted by a metal profile (4), extruded or machined, in the form of an inverted "T" on which the heads are mounted of printing (5) exposing the nozzle plate (1) at the bottom, said metal profile (4) being provided l slight along the entire length of its soul, three horizontal cylindrical perforations (6, 8), the lowest being communicated with each other by one end through a conduit (7) defining a circuit of liquid circulation at the desired temperature, while the upper one (8) acquires functions of distributor and thermal conditioning of the incoming ink through one end, through the printheads (5) through vertical ducts (9) made in the upper part and by means of respective manual valves (10) and tubes (11).

2. AUTONOMOUS PRINTING MODULE BY INK JET, according to claim 1, characterized in that the ink is supplied to the printheads (5) under pressure adequate at all times, through a job deposit

(12) with a lower level than the injector plates

(1), the electrovalves (15, 17) of the pressurized air inlet (15) and the pressurized ink (17) being closed, and the solenoid valve (18) communicating with the outside, during the printing phase ; filling the work tank (12) to maintain the level as the ink is consumed, the pressure ink inlet solenoid valves (17) and the solenoid valve (18) communicating with the outside remain open.

3.- AUTONOMOUS PRINTING MODULE BY INK JET, according to claim 1, characterized in that during the printing phase, the ink is supplied to the printheads (5) through a distributor (8), by means of a work tank (12) with a lower level than the injection plates (1), the pressure inlet solenoid valve (17) being closed to the reservoir (12) and the bypass communication solenoid valve (20) open with a peristaltic pump (21) distributor power

(8) from the reservoir (12), said peristaltic pump (21) being stopped; filling the work tank

(12) to maintain the level, when the inlet solenoid valve (17) of the pressurized ink is open and the tank (12) being communicated with the outside through a conduit (19).

4.- AUTONOMOUS PRINTING MODULE BY INK JET, according to claim 1, characterized in that during the printing phase, the ink is supplied to the printheads (5) through a distributor (8) by means of a work tank ( 12) with a lower level than the nozzle plate (1), the ink inlet solenoid valve (17) being closed a pressure to the tank (12) and stop a centrifugal pump

(22) distributor supply (8), the ink flowing through the channels of the impeller thereof; filling the tank (12) to maintain the level, by opening the ink inlet solenoid valve (17) and the tank (12) being connected to the outside by a conduit (19).

5.- AUTONOMOUS PRINT MODULE BY JET OF

INK, according to claim 1, characterized in that the print head (5) is protected by fins

(23) that leave the injectors visible through a small slot (24) and there is an absorbent sponge sheet (25) between the injector plate (1) and said fins (23), also including a concave cap (26) movable with another absorbent sponge (27) that collects the excess ink, the excess ink being sucked through a hole (28) of its base, forming the absorbent sponge

(27) a mound (30) that closes and assists in cleaning the injectors.

6.- AUTONOMOUS PRINT MODULE BY JET OF

INK, according to claim 1, characterized in that the printhead (5) exposes the nozzle plate (1) when placed in a window made in the metal support or profile (4), also including a concave mobile cover (26) with two absorbent sponges (31) at the ends of its cavity, which collect the excess ink and clean a spatula (32) at the end of each path.

7. AUTONOMOUS PRINTING MODULE BY INK JET, according to claim 6, characterized in that the spatula (32) is freely oscillating in a cylinder (33) integral perpendicularly to a longitudinal rod (34) so that when it moves axially the spatula can lean and slide more smoothly over the injector plate (1).

8. - AUTONOMOUS PRINTING MODULE BY INK JET, according to claim 1, characterized in that the concave covers (26) are arranged in two parallel rows under the wings of the inverted "T" profile (4), in a single piece or bar side (35), with a longitudinal duct (36) as a collector of all ink outlets, both bars (35) being connected with several cranks (37) parallel to each other and connected to individual vertical shafts (38) animated rotating and axial, for the parallel displacement of both bars

(35) from the resting position to that of work and vice versa.