EP3256322B1 - Method and device for cleaning and protecting a hydraulic connection - Google Patents

Description

TECHNICAL AREA AND PRIOR ART

The invention relates to the field of printers, in particular of the continuous ink jet (CIJ) type.

It also relates to the architecture (the layout of the ink circuit) of a printer, for example of the CIJ type, in particular in order to prevent situations in which certain channels used by the ink may be blocked during their use. .

Continuous inkjet printers (CIJ) are well known in the field of coding and industrial marking of various products, for example for marking bar codes, the expiry date on food products, or even references or distance marks on cables or pipes directly on the production line and at high speed. This type of printer is also found in certain areas of decoration where the possibilities of graphic printing of technology are exploited.

These printers have several typical subsets as shown in the figure 1 .

First, a print head 1, generally offset relative to the body of the printer 3, is connected to the latter by a flexible umbilicus 19 gathering the hydraulic and electrical connections necessary for the operation of the head by giving it flexibility that facilitates integration into the production line.

• un circuit d'encre dans la partie basse du pupitre (zone 4'), qui permet d'une part, de fournir de l'encre à la tête à une pression stable et d'une qualité adéquate, et d'autre part de prendre en charge l'encre des jets non utilisée pour l'impression,
• un contrôleur situé dans le haut du pupitre (zone 5'), capable de gérer les séquencements d'actions et de réaliser les traitements permettant l'activation des différentes fonctions du circuit d'encre et de la tête.
• une interface 6 qui donne à l'opérateur le moyen de mettre l'imprimante en œuvre et d'être informé sur son fonctionnement.

The body of the printer 3 (also called desk or cabinet) usually contains three sub-assemblies:

• an ink circuit in the lower part of the desk (zone 4 '), which allows on the one hand, to supply ink to the head at a stable pressure and of a quality adequate, and on the other hand to take care of the ink of the jets not used for printing,
• a controller located at the top of the desk (zone 5 '), capable of managing the sequencing of actions and carrying out the processing allowing the activation of the various functions of the ink circuit and of the head.
• an interface 6 which gives the operator the means of implementing the printer and of being informed of its operation.

In other words, the cabinet has 2 sub-assemblies: in the upper part, the electronics, the power supply and the operator interface, and in the lower part an ink circuit supplying the ink, of nominal quality, under pressure at the head and the depression of recovery of the ink not used by the head.

The figure 2 schematically represents a print head 1 of a CIJ printer. It includes a drop generator 60 supplied with electrically conductive ink pressurized by the ink circuit 4.

This generator is capable of emitting at least one continuous jet through a small orifice called a nozzle. The jet is transformed into a regular succession of drops of identical size under the action of a periodic stimulation system (not shown) located upstream from the outlet of the nozzle. When the drops 7 are not intended for printing, they go to a gutter 62 which collects them in order to recycle the unused ink and return them to the ink circuit 4. Devices 61 placed along the jet (charge and deflection electrodes) allow, on command, to electrically charge the drops and deflect them in an electric field Ed. These are then deviated from their natural trajectory of ejection from the drop generator. The drops 9 intended for printing escape the gutter and will deposit on the support to be printed 8.

This description can be applied to continuous jet printers (CIJ) called binary or multi-deflected continuous jet. Binary CIJ printers are equipped with a head whose drop generator has a multitude of jets, each drop of a jet can only be directed towards 2 paths: printing or recovery. In multi-deflected continuous jet printers, each drop of a single jet (or a few spaced jets) can be deflected on various trajectories corresponding to different charge commands from one drop to another, thus carrying out a scanning of the area to be printed in a direction which is the direction of deflection, the other direction of scanning the print area is covered by relative movement of the print head and the print medium 8. Generally the elements are arranged so that these 2 directions are substantially perpendicular.

An ink circuit of a continuous inkjet printer makes it possible first of all to supply ink under regulated pressure, and possibly solvent, to the drop generator of head 1 and to create a vacuum to recover the fluids not used for printing back from the head.

It also allows the management of consumables (distribution of ink and solvent from a reserve) and the control and maintenance of the quality of the ink (viscosity / concentration).

Finally, other functions are linked to user comfort and automatic handling of certain maintenance operations in order to guarantee identical operation regardless of the conditions of use. Among these functions are the solvent rinsing of the head (drop generator, nozzle, gutter), assistance with preventive maintenance such as replacement of components with a limited life (filters, pumps).

These different functions have very different purposes and technical requirements. They are activated and sequenced by the printer's 5 'controller which will be all the more complex the greater the number and sophistication of the functions.

With regard to the inks used, those containing pigments, for example titanium oxide (rutile TiO ₂ or anatase), in the form of particles of sub-micron dimension, are particularly advantageous for their whiteness and their opacity. They are called pigment inks and are used for marking and identifying black or dark substrates.

But the dense particles of pigments have a natural tendency to sediment, in particular in the ink supply conduits, when the ink is at rest. The consequences of this sedimentation can be the formation, in these conduits, of solid plugs which can block them, partly or even completely. In addition, during essential maintenance operations, the venting of the connectors, in the presence of ink, can form plugs of dry ink. The same problem also concerns the cannula for connecting ink cartridges to the ink circuit: ink is supplied to the circuit from a cartridge, a consumable element that the user replaces when it is empty. The connection to the ink circuit is made by a cannula which fits into an adapted opening of the cartridge and which also constitutes an area for sedimentation of the ink and formation of solid plugs. The document FR 2618278 describes a method and a device for solving the problem of clogging of an ink ejection nozzle of an ink jet printer.

This can result, in particular, in ink supply difficulties as well as a loss of opacity of the markings.

These problems are critical and, since the ink cannot be brewed when it is in the conduits and connection means, require the intervention of a technician: the printer is then blocked, production is stopped, which generates user dissatisfaction as well as loss of time and costs.

In the specific field of inkjet printers, no technique is known which makes it possible to solve these problems of plugging connections, in particular conduits or pipes or of the cannula, in which the ink is caused to circulate, in particular from the ink cartridge to the main ink tank.

The problem therefore arises of producing an ink circuit, and a method of operating an ink circuit, which allows the cleaning of the hydraulic connection, at least between an ink cartridge and an ink circuit. , in particular in the case of a pigment ink.

In addition, in general, the consumables used in this type of device, and in particular the ink and the solvent, are expensive elements.

We therefore seek to minimize their consumption while eliminating the blockage of the conduits and connections of the ink circuit.

This same problem arises in the case of any ink, even non-pigmentary, which can dry and form deposits of dry matter in the conduits and connections of the ink circuit.

STATEMENT OF THE INVENTION

• a) une étape d'envoi de solvant, à une pression P1, vers la cartouche, par au moins une partie des moyens de connexion fluidique entre la cartouche d'encre et le réservoir,
• b) une étape de pompage d'au moins une partie du solvant, envoyé lors de l'étape a), vers le réservoir principal.

The invention firstly relates to a method for cleaning an ink circuit of an inkjet printer, comprising at least one reservoir, called main reservoir, at least one ink cartridge, a pump for pumping the ink from the cartridge and means for fluid connection between the ink cartridge and the reservoir, and means for controlling the printer, this method comprising at least:

• a) a step of sending solvent, at a pressure P1, to the cartridge, by at least part of the fluid connection means between the ink cartridge and the reservoir,
• b) a step of pumping at least part of the solvent, sent during step a), to the main tank.

The fluid connection means between the ink cartridge and the reservoir make it possible to supply a fluid (or a liquid, generally ink, but here also solvent), from the ink cartridge to the main reservoir.

Prior to step a), a method according to the invention may include a step of detecting the blocked state of at least part of the fluid connection means between the ink cartridge and the reservoir, for example by measurement of the ink level variation in the main tank, when pumping ink from the ink cartridge to the main tank.

During step a), the solvent can be sent to the cartridge by a part of the fluid connection means between the ink cartridge and the reservoir, the solvent circulating in the opposite direction to the direction of circulation of the ink, when it is sent from the ink cartridge to the tank.

Step b) can be carried out using said pump to pump the ink, from said ink cartridge to the main reservoir.

Steps a) and b) can be repeated.

The pressure P1 can be between 1 and 10 bars.

A method according to the invention can also include a step of sending solvent into the cartridge and into at least part of the fluid connection means, without step of pumping at least part of the solvent thus sent to the main tank.

According to one embodiment, a method according to the invention may include a step, prior to step a), of detecting the presence of the ink cartridge, for example by exchanging at least one piece of data, between an electronic circuit or electrical associated with the cartridge and the printer control means.

The solvent sent during step a) can be taken from part of the main tank. Prior to step a), a step of detecting the level of solvent in the main tank can be carried out. As a variant, the solvent can be removed in a removable cartridge. The solvent can be sent using pumping or pressurizing means, through a circuit which may be partly different from that used in step b).

A method according to the invention may include a step, prior to step a), of detecting the empty state of the ink cartridge, carried out for example from at least one measurement of a level of ink in the main tank.

During step b), at least part of the solvent can be transferred to an intermediate tank, separate from the main tank. The solvent thus stored in the intermediate tank can then be transferred to the so-called main tank.

After step a), the solvent can be kept under pressure P1, a measurement of the variation in pressure of the solvent or of the level or volume of the solvent being carried out. If a reduction in the pressure of the solvent, or in the level or volume of the solvent, for example greater than a threshold value, is measured, it may be concluded that a blockage or a blocked state has been eliminated from part of the circuit.

If a decrease in solvent pressure, or in the level or volume of the solvent, greater than a threshold value, is not measured, which may reflect the maintenance of a clogging situation, one or more variations of pressure from solvent. According to one embodiment, it is therefore possible to temporarily increase the pressure in the circuit, for example by several jerks (or variations or pulses) of pressure.

If the duration of the cleaning or unclogging operations is greater than a predetermined duration Δt, then it may be decided to stop the cleaning and, for example, to change the ink module. Otherwise, as long as the predetermined duration has not been reached, a test can be carried out again on the blocking of the circuit and the unclogging operations.

Advantageously, the measurement of variation in solvent pressure or in the level or volume of the solvent makes it possible to verify the effectiveness of the release, and, possibly if this is not the case, to carry out or reiterate one or more variations in pressure. solvent.

During step a), the solvent can be sent to the cartridge without passing through the pump to pump the ink from the cartridge, or by passing through said pump.

The invention also relates to an ink circuit of a continuous inkjet printer, comprising at least one reservoir, called the main reservoir, and means for controlling the printer, the latter being programmed to implement a method according to the invention.

• a) envoyer du solvant, à une pression P1, jusque dans lesdits moyens pour relier une cartouche d'encre au dispositif, par au moins une partie desdits moyens de connexion fluidique,
• b) pomper au moins une partie d'un solvant, présent dans lesdits moyens pour relier une cartouche d'encre au dispositif et dans au moins une partie desdits moyens de connexion fluidique.

The invention also relates to an ink circuit of a continuous ink jet printer, comprising a reservoir, called the main reservoir, a pump for pumping ink towards the reservoir, means for connecting an ink cartridge. to the circuit, means for fluid connection between said means for connecting an ink cartridge to the circuit and the reservoir, and means for controlling the printer, these means being provided for:

• a) send solvent, at a pressure P1, as far as said means for connecting an ink cartridge to the device, by at least part of said fluid connection means,
• b) pumping at least part of a solvent present in said means for connecting an ink cartridge to the device and in at least part of said fluid connection means.

The fluid connection means between the ink cartridge and the reservoir allow a fluid (generally ink) to be brought from the ink cartridge to the reservoir.

The printer control means can also be provided to detect, before sending the solvent, the blocked state of at least part of the fluid connection means between the ink cartridge and the reservoir.

These means comprise for example means for measuring the variation of a level of fluid (for example ink) in the main tank, for example following a, or during a pumping of ink from a cartridge ink to the main tank.

Means can be provided for maintaining a fluid (or a liquid, for example solvent) under pressure in the circuit, as well as means for measuring a variation in fluid pressure (for example solvent) or of a level or d 'a volume of this fluid.

Such means can make it possible to carry out one or more variations in pressure of the liquid (or of the solvent), in particular, in the case where the means for measuring a variation in pressure do not detect a decrease in pressure of the fluid, or of the level or of the volume of the fluid, greater than a threshold value.

Advantageously, a circuit according to the invention comprises means for effecting or reiterating one or more variations in fluid pressure in the circuit, for example if a variation in fluid pressure (or a liquid, for example solvent) or of a level or volume of this fluid is not detected.

Said fluid connection means can be connected to means making it possible to inject a solvent therein.

An ink circuit according to the invention may include means for measuring an ink level in the main tank, said printer control means making it possible to calculate, for example from a measurement of a level d ink in the main reservoir, a level of residual ink in an ink cartridge connected to the fluid connection means.

An ink circuit according to the invention may further comprise an intermediate reservoir, separate from the main reservoir and means for transferring, to said intermediate reservoir, at least part of a fluid (or a liquid, in particular solvent), present in said means for connecting an ink cartridge to the circuit and in at least part of said fluid connection means.

• des moyens pour envoyer un fluide (ou un liquide, par exemple du solvant), vers, ou jusque dans, lesdits moyens pour relier une cartouche d'encre au circuit, par au moins une partie desdits moyens de connexion fluidique, mais sans faire circuler ce fluide par la pompe pour pomper l'encre de la cartouche ;
• et/ou des moyens pour envoyer un fluide (ou un liquide, par exemple du solvant) vers, ou jusque dans, lesdits moyens pour relier une cartouche d'encre au circuit, par au moins une partie desdits moyens de connexion fluidique, en faisant circuler ce fluide par la pompe qui permet de pomper l'encre de la cartouche.

An ink circuit according to the invention can also comprise:

• means for sending a fluid (or a liquid, for example solvent), to, or into, said means for connecting an ink cartridge to the circuit, by at least part of said fluid connection means, but without circulating this fluid by the pump to pump the ink from the cartridge;
• and / or means for sending a fluid (or a liquid, for example solvent) to, or into, said means for connecting an ink cartridge to the circuit, by at least part of said fluid connection means, making circulate this fluid through the pump which allows the ink to be pumped from the cartridge.

Means may be provided for selecting one or the other of the paths for circulation of such a fluid, and therefore by the pump to pump the ink, or not.

• un circuit d'encre selon l'invention,
• une tête d'impression,
• des moyens de liaison hydraulique, pour amener, depuis le réservoir d'encre, une encre à imprimer à la tête d'impression et envoyer, vers ledit circuit d'encre, une encre à récupérer à partir de la tête d'impression,
• des moyens de liaison électrique pour alimenter électriquement ladite tête d'impression.

The invention also relates to an ink jet printer, comprising:

• an ink circuit according to the invention,
• a print head,
• hydraulic connection means, for bringing, from the ink tank, an ink to be printed to the print head and sending, to said ink circuit, an ink to be recovered from the print head,
• electrical connection means for electrically supplying said printhead.

The ink jet printer implemented in a method according to the invention, or in a device according to the invention can be a continuous jet printer (CIJ), in particular of binary type, or a multi continuous jet printer - deflected.

BRIEF DESCRIPTION OF THE FIGURES

• The figure 1 represents a known printer structure,
• the figure 2 represents a known structure of a print head of a CIJ type printer,
• the figure 3A is an example of a fluid circuit according to the present invention,
• the figure 3B is a variant of an example of a fluid circuit according to the present invention,
• the figure 4 represents an ink cartridge and the controller means of a printing machine,
• the figure 5 represents steps for carrying out a cleaning process according to the present invention,
• the figure 6A still shows an example of a fluid circuit structure using a circuit according to the present invention.
• the figure 6B shows a variant of an example of a fluid circuit structure using a circuit according to the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

The figure 3A shows a removable ink cartridge 30 and an example of a part of the ink circuit of the machine, between the cartridge 30, the main tank 10 and the solvent cartridge 40, also removable.

The reference 300 designates the cannula (or any equivalent means), which will make it possible to connect, from the fluidic point of view, the cartridge 30 to the rest of the circuit.

When the cartridge 30 is in place, ink can be pumped, using pumping means 31, towards the main reservoir 10 via fluid connection means, comprising conduits 320, 340, 341, 343, 344 and valves (or solenoid valves) 32, 33, 34, 35, which can be “3-way” type valves. Thus, the pump 31 pumps ink, from the cartridge 30, which passes successively, via the valves 32 and 34, via conduits 320, 340, 341, 343, 344, and then, via valve 33, be sent to the main tank 10 (path I on the figure 3A ).

Means 35, 345 make it possible to introduce solvent under pressure, for example at a pressure between 1 and 10 bars, or between 1 bar and 5 bar, in these fluid connection means. According to the illustrated embodiment, these means comprise, on the one hand, the valve 35, and, on the other hand, a conduit 345 disposed upstream of the valve 35. After opening of this valve 35 (in position NC on the figure 3A ), and depending on the opening or closing state of valves 32 and 34 (in the NC position on the figure 3A ), this solvent can be directed, successively through the conduits 341, 340, and 320, to the cartridge 30 (see circulation path II in figure 3A ); as a variant, the solvent can be passed through path III, successively through conduits 341, 343, 344, 320, up to cartridge 30 which also makes it possible to clean the pump 31. The solvent will therefore circulate in parts of the circuit which, as explained above, were previously used to inject, in a direction of circulation opposite to that of the solvent, ink into the main reservoir 10. This is the case of the conduits 341, 340, 320 and cannula 300.

A pressure sensor 47 can be arranged, in the diagram of the figure 3A , upstream of the valve 35, on the path of the solvent.

This pressurized solvent will make it possible to dissolve or destroy the ink residue plugs which may have formed in the conduits 341, 340, 320, or in the valves 35, 34, 32, or in the cannula 300. Advantageously , and as described more precisely below, this is done after detection of a blocked state of part of the circuit, on the path of the ink. It is thus possible to perform a cleaning of the fluidic connections, which is particularly advantageous to implement after detection of a blocked state of a part of the circuit and / or after the cartridge 30 has been emptied, but before it is removed for be replaced with a full cartridge.

The reservoir, called the main reservoir 10, can be structured in several compartments 11-14, including a compartment 14 containing solvent.

The solvent can come from a removable solvent cartridge 40 (shown in dashed lines in figure 3A ), connected by means 400 of fluidic connection (shown schematically by broken lines in figure 3A ) at the main tank, these means 400 comprising in particular a pump (not shown in the figure 3A ). The main reservoir 10 can be provided with means 15 for detecting the level of the ink that it contains. In the main tank, the solvent is mixed with ink (the mixture itself being called "ink").

The pressurized solvent sent during the cleaning described above can come from the solvent compartment 14 of the reservoir 10. Means can be provided for detecting a level of solvent in this compartment. As a variant, the solvent can come directly from the cartridge 40. In all cases, it is pressurized by the pump dedicated to pumping the solvent.

As explained above in the case of an example, part of the path ( figure 3A , path I) taken by the ink, at the outlet of the cartridge 30 and towards the main tank 10, can then be taken, in a reverse direction of circulation ( figure 3A , path II), with solvent, coming from the solvent cartridge 40 or from part 14 of the main tank 10 containing solvent.

The solvent under pressure, sent to the cartridge 30, can then be pumped to the main tank 10. The path of the solvent is then that usually used by the ink ( figure 3A , path I), from the cartridge 30 to the main tank 10: after cleaning, the valve 35 is closed (in the NO position in figure 3A ) and the pump 31 is activated to send the cleaning solvent to the reservoir 10. The solvent therefore makes it possible to clean the conduits in which it will circulate, as well as the cannula 300; then it can be kept in the circuit, without being lost.

As already indicated above, this can be done when the cartridge 30 is empty, which can be detected, in particular, via the level measurement variations in the main tank 10: this is the case, for example, if the ink level variation is less than a threshold value (for example 5/10 mm) for a predetermined duration (for example 20 s), even when the pump 31 operates to inject ink into the main reservoir 10.

• -a) 1^er rinçage des conduits 341, 340, 320, des vannes 35, 34, 32 et de la canule 300 par du solvant sous pression (figure 3A, trajet II), puis récupération du solvant dans le réservoir 10 (figure 3A, trajet I) ;
• - b) 2^ème rinçage des conduits 341, 340, 320 et de la canule 300 par du solvant sous pression (figure 3A, trajet II), puis récupération du solvant dans le réservoir 10 (figure 3A, trajet I) ;
• - c) rinçage final des conduits 341, 340, 320 et de la canule 300 par du solvant sous pression (figure 3A, trajet II), sans récupération vers le réservoir 10 ; le fait de maintenir le solvant lors de cette étape permet d'éviter tout bouchage ultérieur en maintenant du solvant dans la cartouche, ce qui évite tout séchage.

An example of a cleaning sequence, implementing the method described above, may be the following:

• -a) ^1st rinsing of the conduits 341, 340, 320, of the valves 35, 34, 32 and of the cannula 300 with solvent under pressure ( figure 3A , path II), then recovery of the solvent in the reservoir 10 ( figure 3A , path I);
• - b) ^2nd rinsing of the conduits 341, 340, 320 and of the cannula 300 with solvent under pressure ( figure 3A , path II), then recovery of the solvent in the reservoir 10 ( figure 3A , path I);
• c) final rinsing of the conduits 341, 340, 320 and of the cannula 300 with solvent under pressure ( figure 3A , path II), without recovery to the reservoir 10; maintaining the solvent during this step makes it possible to avoid any subsequent clogging by keeping the solvent in the cartridge, which prevents any drying.

The printer control means (also called "controller") are made in the form of an electric or electronic circuit, or a processor or a microprocessor, programmed to implement a cleaning process according to the invention, for example as described above. It is this controller which controls the opening and closing of the valves, as well as the activation of the pumping means, in order to circulate the solvent according to what has just been described. The controller is also programmed to manage operations other than cleaning, including printing operations.

The detection, prior to the cleaning operations described above, of the “empty” state of the cartridge 30, is carried out from ink level measurements, for example level measurements made in the main reservoir 10 to using the means 15, and using the controller. The latter also takes the decision, and sends the instructions, to circulate the solvent under pressure in the direction of the cartridge 30, then to pump it in the direction of the main reservoir 10.

For safety, it can be ensured, prior to any sending of solvent under pressure to the cartridge 30, that the latter is still in place.

This verification, like the cleaning process, can also be performed using the controller.

To this end, as illustrated in figure 4 , one can use a cartridge 30 provided with a circuit 30a (hereinafter called "tag"), for example produced in the form of a processor or microprocessor. This circuit 30a is for example applied against a wall of the cartridge 30. It may further comprise communication means, for example an RFID type interface, which will allow dialogue with the printer controller, in particular to provide it one or more data which can be interpreted as reflecting the presence of the cartridge.

For its part, the controller is also provided with communication means 3a, for example an RFID type interface, which will make it possible to receive the data transmitted by the tag of the cartridge.

Alternatively, the communication between the body 3 of the printer and the cartridge 30 can be of the contact type. In this case, contacts are provided, on the one hand on the cartridge, on the other hand on the printer, to ensure the transmission of data between the cartridge 30 and the printer. The sending of an RFID signal from the tag to the controller, or the reading by the latter of the presence of the contacts of the tag, makes it possible to detect the presence of the cartridge. This verification can be carried out periodically, and / or again after detection of an empty state of the cartridge.

After the cleaning phases have been carried out, the cartridge 30 can be replaced by a full cartridge.

From the above description, it will be understood that, both the detection of the “empty” state of the cartridge 30 and the cleaning steps which follow this detection, are triggered by the machine itself, without the intervention of an operator, and without stopping the machine. The latter can simultaneously continue printing.

Another application of the invention relates to the case where the cartridge 30 is not empty, and where a clogging on the ink path is detected, from the cartridge 30 to the main reservoir 10.

The detection of a blockage situation of one of the ink circulation conduits, or of the cannula 300, can be carried out, based on pressure or solvent level measurements. This diagnosis can be carried out by the controller, who processes the pressure measurements, estimates the variation in level of the ink in the reservoir for a given duration and pumping power and compares it with what is normally expected under these conditions of pumping time and power.

• mesure de variation de pression lorsque l'on ouvre le circuit (par exemple les vannes 32, 34 et 35 de la figure 3A, la mesure étant réalisée par le capteur 47) ; si il n'y a pas de variation, alors on conclue au bouchage ;
• et/ou mesure du niveau de solvant de la réserve 14 lorsque l'on ouvre le circuit (par exemple les vannes 32, 34 et 35 de la figure 3A) : si il ne varie pas, alors on conclue au bouchage.

According to one embodiment, when the printer is started up, it is checked whether the connections are blocked. For this the following tests can be carried out, for example by the controller:

• pressure variation measurement when opening the circuit (for example valves 32, 34 and 35 of the figure 3A , the measurement being carried out by the sensor 47); if there is no variation, then one concludes with capping;
• and / or measurement of the solvent level of the reserve 14 when the circuit is opened (for example the valves 32, 34 and 35 of the figure 3A ): if it does not vary, then we conclude with blockage.

It is then possible, according to what has been described above, in particular along path II in the case of the circuit of the figure 3A , inject solvent under pressure Ps = P1, for example between 1 and 10 bars, in the direction of the cartridge 30. The pressure Ps can be detected by the sensor 47. This injection can be carried out periodically.

If there is no blockage, or if an obstacle on the path taken by the solvent is removed by the latter, then the pressure Ps of solvent decreases, to a value P2 <P1. The solvent can then be reinjected into the main tank 10, as explained above.

On the contrary, if the solvent pressure Ps remains stable, a clogging situation is still diagnosed by the controller. The pressure P1 is then maintained, for a certain duration Δt1, for example a few seconds, in order to remove the obstacle. This can optionally be combined with one or more “surges” (or variations or pulses) of pressure, for example by cycles of opening and closing of the solenoid valve 35, to reach a pressure P3> P1, each of these "Jolts" being generated for example during a short period, of duration Δt2 <Δt1. Following this, if the pressure Ps decreases, at the value P2 <P1, it is because the obstacle has been eliminated, and the solvent can be reinjected into the main tank 10, as explained above. If the pressure Ps still does not decrease, for example after a certain period which can be of the order of a few tens of seconds, one solution is to carry out a manual intervention and / or to change the cannula 300 or the module ink itself (which includes part of the fluid connections between the cartridge 30 and the main reservoir).

In the cases presented above, the solvent under pressure, sent to the cartridge 30, can then be pumped to the main tank 10. The circuit is then that usually used by the ink, from the cartridge to the main tank : after cleaning, the clearance of the valves 32-35 is reconfigured to send the cleaning solvent to the main tank 10. The solvent therefore makes it possible to clean the conduits in which it will circulate, as well as the cannula 300, then to be maintained in the circuit, without being lost.

• prendre la décision, et envoyer l'instruction, de faire circuler du solvant sous pression en direction de la cartouche 30 ;
• traiter l'information en provenance du capteur 47, pour qu'il procède au pompage du solvant, en direction du réservoir principal 10, ou au maintien de la pression de celui-ci dans les conduits considérés comme bouchés.

As indicated above, the detection of a blockage situation of one of the conduits or the cannula can be carried out using the machine controller. This same controller will:

• make the decision, and send the instruction, to circulate the solvent under pressure in the direction of the cartridge 30;
• process the information coming from the sensor 47, so that it proceeds to pump the solvent, in the direction of the main reservoir 10, or to maintain the pressure of the latter in the conduits considered to be blocked.

As in the case of a cartridge explained above, for safety, it can be ensured, prior to any sending of solvent under pressure to the cartridge 30, that the latter is still in place. The means used for this can be those already explained above (tag 30a and controller).

Prior to this process, it can be checked whether the solvent level is sufficient, or even above a lower limit value. This step can also be carried out in the case of cleaning after detection of the empty state of the cartridge, explained above.

An exemplary embodiment of this process is illustrated in figure 5 .

In a first step (S1), the level of solvent in the solvent reserve 14 is checked.

If this level is below a predetermined threshold value, then the printing machine is immediately stopped, so that it does not operate without solvent. This step can also be carried out in the case of cleaning after detection of the empty state of the cartridge.

If it is greater than this threshold value, then the solvent can be pressurized (step S2), for example at a pressure P1 of between 1 bar and 10 bars, or between 1 bar and 5 bars. If it is not possible to reach this pressure, then a fault is detected. If this pressure can be reached, then we proceed (step S3) to send solvent in the direction of the ink cartridge 30, according to what has been described above, by opening the valves 35, 34, 32.

It is then possible (step S4) to carry out a test on the maintenance, or the reduction, of the solvent pressure for a certain duration Δt1. For example, it is tested whether, at the end of this period, the pressure has decreased by a predetermined value, for example between 1% xP1 and 50% xP1 or else (by measuring the solvent in the reservoir 14) if the level or the volume of solvent has decreased by a predetermined value Δh1 or ΔV1: if one of these questions is answered in the affirmative, then the circuit is considered to be unclogged, and the standard operating sequence of the machine can be resumed.

Otherwise, it is considered that the ink circuit is blocked; we can then try (step S5) to temporarily increase the pressure, for example by jerks (or variations or pulses) of pressure (as already explained above), which can be generated by one or more opening cycles and closing the valve 35.

A test can also be carried out over the duration of the cleaning or unclogging operations (step S6): if the cycle has a duration greater than a predetermined duration Δt, then it may be decided to stop the cleaning and, for example, to proceed to a change of the ink module. Otherwise, as long as the predetermined duration has not been reached, the test of the previous step S4 can be carried out again.

All the operations described above can be carried out by the machine controller, programmed for this purpose.

In other words, both the diagnosis concerning a blockage situation and the remedy provided can be formulated and triggered by the machine itself, without operator intervention, and without stopping the machine. The machine can simultaneously continue printing.

A variant of a circuit described above is shown in figure 3B ; it is identical to that of the figure 3A , except for the presence of an intermediate tank 110, in which the solvent which has allowed cleaning, as explained above, can be temporarily recovered before being sent to the main tank 10.

A 3-way valve 36 makes it possible to direct the solvent either directly to the main reservoir 10 (along the path I), or to the intermediate reservoir 110 (along the path la). A pump 31a subsequently makes it possible to pump the contents of this reservoir to the main reservoir 10. The reservoir 110 is therefore placed in parallel with the circuit followed by the ink when it is pumped from the cartridge 30 to the reservoir 10.

During cleaning by the circulation path I, the valve 36 is actuated so as to guide the solvent towards the valve 33, along this path I which therefore remains unchanged compared to the case of the figure 3A .

In this variant, the solvent which was used to clean the connections of the ink cartridge could be used to make the additions of solvent to the main ink tank 10 and thus maintain the quality of the ink, without suddenly adding solvent in this main tank 10 after such cleaning.

The additional tank is preferably placed at atmospheric pressure (PA) in order to avoid any overpressure, this can be achieved by connecting, by a conduit 111, the top of this tank to the top of the main tank 10.

The valve 36 and the pump 31a can be actuated by the machine controller, programmed for this purpose.

An ink circuit in which the circuit, described above in connection with the figure 3A , can be used, is illustrated in figure 6A . The structure of this circuit is close to that described in the document WO 2011/076810 .

In this figure, reference numerals identical to those of the preceding figures designate therein identical or corresponding elements.

The main tank is here divided into compartments 11, 12, 13, 14.

The compartment 11 forms an intermediate tank: it constitutes a buffer storage tank in which the ink is stored in a part of the circuit of fluids which is intermediate between the ink cartridges 30 and of solvent 40 (cartridges of removable consumables) and the print head 1 itself. The fluids returning from the head are recovered by this same intermediate tank 11.

Reference 19, which designates the umbilicus, which brings together the communication channels allowing the various fluids to be brought to the print head, as well as the electrical connections making it possible to bring the electrical signals for the operation of the head.

The ink contained in the reservoir 11 is maintained with the quality required for optimal operation of the printing, in particular adjusted in viscosity, as described below using the system according to the invention.

After being coarsely filtered by the filter grid 22, the ink taken from the intermediate reservoir 11 arrives at the inlet of the pump 20, for example a gear pump, which puts it under pressure. This pump 20 is driven by a motor controlled in speed (power) by the controller. The pump 20 can be short-circuited by an adjustable bypass 21 to adjust its operating range (pressure / flow or pressure / speed characteristic). Downstream of the pump 20, an anti-pulse device 23 is arranged, for the reasons explained in the document WO 2011/076810 .

A pressure sensor 24, and possibly a temperature sensor, can be provided, downstream of the anti-pulsating device 23: the data which it supplies are used by the controller to control the ink pressure to a set point, generally when the ink jet speed in the head is not available (for example when the jet ejection is stopped, or the jet speed is not measurable).

The ink is filtered by the main filter 25 downstream from the sensor 24 before being sent to the head 1.

Regarding the return of fluids not used for printing, these are sucked at the head (recovered by the gutter or in return for purging) through the umbilicus 19 using a hydro-ejector 26 which, for example, uses part of the flow rate of the pump 20 as motive energy to create a vacuum by the Venturi effect.

• à l'arrêt du jet, on envoie du solvant pour nettoyer le générateur de gouttes 2 et la buse, puis on rince les circuits de purge et de gouttière 3 (y compris leurs électrovannes 7 et 8) et, pour finir, on aspire le solvant du générateur de gouttes 2 et de la gouttière 3 avant de fermer toutes les électrovannes de tête ;
• au démarrage du jet, après ouverture de la gouttière 62 (figure 2) on alimente le générateur de gouttes 2 en solvant sous pression puis on fait passer progressivement l'alimentation du solvant à l'encre.

The general course of these operations in the circuit can be as follows:

• when the jet is stopped, solvent is sent to clean the drop generator 2 and the nozzle, then rinse the purge and gutter circuits 3 (including their solenoid valves 7 and 8) and, finally, we vacuum the solvent for the drop generator 2 and the gutter 3 before closing all the head solenoid valves;
• when the jet starts, after opening the gutter 62 ( figure 2 ) the drop generator 2 is supplied with solvent under pressure and then the supply of solvent is gradually switched to ink.

The container 10 is partially partitioned thus defining the four functional reservoirs 11, 12, 13, 14 connected together and to the two removable reserve consumable cartridges (ink cartridge 30 and solvent cartridge 40) by conduits or passages and a few active hydraulic components (controlled by the controller) such as four 3-way solenoid valves (18, 32, 33, 42), a 2-way solenoid valve 43 and two pumps, for example low capacity diaphragm pumps, 31, 41 . The ink cartridge 30 and the solvent cartridge 40 make it possible to replace the fluids consumed by the printer during its operation. These cartridges generally have no specific means for measuring or detecting the volume of fluid which they contain, the content of the cartridge 30 being able to be evaluated in the manner described above. The cartridges are connected to bases connected to the corresponding solenoid valves 32, 42.

More specifically, the single container 10, the bottom of which is flat and horizontal, comprises internal partitions present over only part of its height, dividing it into four reservoirs 11, 12, 13, 14 opening onto the top in a common volume . The four tanks 11, 12, 13, 14 are therefore balanced at an identical gas pressure. The common volume internal to the container 10 is in communication with the outside air through a vent 111. Thanks to this vent, air charged with solvent vapor coming from the discharge of the hydro-ejector 26 is allowed. sucked fluids (mixture of ink and air entering the gutter 62 of the print head 1), to escape towards the outside. Before reaching the open air, this air charged with solvent vapor passes through a passive condenser 16 consisting of a cavity provided with baffles which multiplies the contact surface between the charged air and the walls of the condenser. Such a condenser 16 makes it possible to condense, on its walls, part of the solvent vapors which return by gravity to the intermediate tank 11.

Each reservoir 11, 12, 13, 14 is more or less filled with fluid (or liquid). Because the partitions are not made up to the top of the container 10, a full tank may overflow into the adjacent tank. Thus, the reservoir 13 can be used as a constant level reservoir by overflowing into the intermediate reservoir.

As explained above, the intermediate reservoir 11 is the one which contains the ink intended to supply the print head 1 under pressure and to recover the fluids coming from the return thereof by the gutter 62.

The second reservoir 12 is the measurement reservoir because it is in this that the actual measurements of ink and solvent level are carried out by means of a preferably continuous level sensor 15, which equips it.

The third reservoir 13 is supplied, in a closed circuit, with ink coming from the intermediate reservoir 11 to constitute a constant level reservoir by overflowing towards the intermediate reservoir 11. More precisely, the ink is pumped thanks to the supply 20 of the intermediate reservoir 11 and reaches the reservoir 13 by delivery through the filter grid 28 and the solenoid valve 18 in the NC position (1-2). Thus, filled at constant level, the reservoir 13 supplies ink with a constant static pressure. The constant level tank 13 is in permanent hydraulic communication with the measurement chamber 12 using a conduit L3 connecting their bottom, equipped with a calibrated leak 17, for example a viscous leak with a length much greater than its diameter.

The fourth tank 14 constitutes a solvent tank used for rinsing the head during the start and stop operations of the jet. This reservoir 14 also makes it possible to prolong the operation of the printer when the cartridge of solvent 40 is empty, providing the solvent necessary for the viscosity correction and thus gives the user the possibility of postponing the replacement of the empty cartridge. This tank 14 can overflow into the measurement tank 12. This tank can also supply solvent for the cleaning operations according to the invention.

To transfer ink or solvent to the intermediate reservoir 11, two sub-assemblies are provided, each consisting of a pump associated with two solenoid valves constituting a sub-assembly dedicated to the transfer of one of the fluids.

Thus, for the transfer of the ink, a sub-assembly comprises the pump 31 associated with the solenoid valves 32 - 35. This allows, on the one hand, to transfer new ink from the cartridge 30 to the intermediate reservoir 11 and on the other hand, to empty the measuring tank 12 towards the intermediate tank 11.

For the transfer of solvent, another sub-assembly comprises the pump 41 associated with the solenoid valves 42, 43. This allows on the one hand to transfer determined quantities of solvent to the measuring tank 12, ie from the cartridge of solvent 40 to the solvent tank 14 by overflow into the tank 12, either from the solvent tank 14 to the measurement tank 12 and, secondly, to pressurize the solvent, coming from the solvent tank 14, for rinsing the head during stops and starts of the jet. The pump 41 also makes it possible to put the solvent under pressure for the purpose of the cleaning operations according to the invention. In this case, the fluid, taken from the compartment 14, is sent to the ink cartridge 30 via the conduit 345, the valve 35, then the conduits 341, 340 and 320.

In this exemplary embodiment, with the exception of the solvent supply (hydraulic line L4) coming from the solvent transfer pump 41, the hydraulic lines L1, L2, L3 are connected to the container 10 at its flat bottom. and horizontal, which is that of the four reservoirs 11, 12, 13 and 14, which allows fluid communications by communicating vessel.

The sensor 15 can be a continuous level sensor, capable of measuring, at least in a given range of levels, any level of the fluid present in the measurement tank 12. Thus, it is possible, by performing level measurements , for example cyclically, to know the evolution of the level over time. Such as shown, the continuous level sensor 15 further comprises a pressure sensor 151 connected in leaktight manner to one end of a tube 150, the other end of the tube being open. The tube 150 is arranged vertically in the measuring tank 12 so that the opening of the tube opens near the bottom. There are other devices making it possible to measure a level, in particular continuously, for example ultrasonic, capacitive or other sensors.

The pressure sensor 151 measures the static pressure of the column of fluid present in the measurement tank 12. The pressure of the gas above the surfaces of liquid in the container 10 is for this identical to the pressure of the outside air where there is sensor 151, which functions as a relative pressure sensor with external pressure reference. From the knowledge of the density of the fluid, the controller deduces the height of the column and therefore the level of the fluid.

The sensor 151 can be calibrated more or less periodically: the offset of the sensor, which determines the zero level, is measured after complete emptying of the measurement tank 12, that is to say after emptying to below the level of the opening of the tube 150. Complete emptying of the measurement tank 12 can be carried out using the solenoid valves 32, 33 and the ink transfer pump 31, as explained in WO 2011/076810 .

According to one example, the measurement tank 12 and the intermediate tank 11 are placed in hydraulic communication by their bottom by switching the solenoid valve 33 in the NC position (1-2). The ink taken out of the ink pressurization pump 20 is directed to the intermediate reservoir (solenoid valve 18 in the NO position (2-3)). As the constant level tank 13 is in permanent communication with the measurement tank 12, through the calibrated leak 17 by the line L3, the volume levels considered in the tanks 11, 12, 13 tend, after equilibrium, towards a single value which is measured by the sensor 15. Knowing the cross-sectional area of the three reservoirs 11, 12, 13, the controller deduces therefrom the exact volume of ink available; it is ink ready for printing, that is to say of adequate quality (viscosity).

The level measurement can be used, as already explained above, to estimate whether or not a cartridge 30 is empty.

A variant of the circuit described above in connection with the figure 6A is represented in figure 6B ; this circuit is identical to that of the figure 6A , but uses an intermediate tank 110, as in figure 3B , with the same advantages as those set out above in connection with this figure 3B : the 3-way valve 36 makes it possible to direct the solvent either directly to the main reservoir 10 (along path I), or to the intermediate reservoir 110 (along path la). The additional pump 31a subsequently makes it possible to pump the contents of this tank to the main tank 10. The valve 36 and the pump 31a can be actuated by the machine controller, programmed for this purpose.

The invention is of particularly advantageous application in the case of an ink containing dispersions of dense particles such as metals or pigments of metal oxides. For example, titanium, zinc, chromium, cobalt or iron, (such as TiO ₂ , ZnO, Fe ₂ O ₃ , Fe ₃ O ₄ , ...) in the form of micron or sub-micron particles. Such a pigment ink can, for example based on TiO ₂ , be used for marking and identifying black or dark supports.

But it is also advantageous in the case of any non-pigmented ink, which, as already explained, can dry and form deposits of dry matter in the conduits and connections of the ink circuit.

Claims (17)

1. A method for cleaning an ink circuit of an ink-jet printer, comprising at least one tank (10), referred to as the main tank, at least one removable ink cartridge (30), a pump (31) for pumping the ink from the cartridge and means (32-35, 320, 340, 341, 343, 344) for fluid connection between the ink cartridge and the tank, and means (3) for controlling the printer, this method comprising at least:

   - a) a step of sending solvent, at a pressure P1, to the cartridge (30), by at least a part of the means for fluid connection between the ink cartridge (30) and the tank (10), the solvent flowing in the reverse direction (II) to the flowing direction (I) of the ink, when the latter is sent from the ink cartridge (30) towards the tank (10);

   - b) a step of pumping at least a portion of the solvent, sent in step a), towards the main tank (10).
2. The method according to claim 1, wherein, step b) is carried out using said pump (31) for pumping the ink, from said ink cartridge (30) towards the main tank (10).
3. The method according to one of claims 1 or 2, further comprising at least a reiteration of steps a) and b).
4. The method according to one of claims 1 to 3, further comprising a step of sending solvent in the cartridge (30) and in at least a part of the means for fluid connection between the ink cartridge and the main tank (10), without a step of pumping at least a portion of the solvent thus sent towards the main tank.
5. The method according to one of claims 1 to 4, comprising a step, prior to step a):

   - of detecting the presence of the ink cartridge, for example by exchanging at least one datum, between a circuit (30a) associated with the cartridge and the means (3, 3a) for controlling the printer;

   - and/or of detecting the empty state of the ink cartridge, for example from at least one measurement of an ink level in the main tank (10).
6. The method according to one of claims 1 to 5, the solvent sent during step a) being taken in the main tank (10), the method possibly further comprising a step, prior to step a), of detecting the solvent level in the main tank (10).
7. The method according to one of claims 1 to 6, comprising a step, prior to step a), of detecting the clogged state of at least a part of the means for fluid connection between the ink cartridge and the tank, for example by measuring the variation in the ink level in the main tank, following or during, an ink pumping from the ink cartridge (30) towards the main tank (10).
8. The method according to claim 7, wherein, after step a), the solvent is maintained under pressure P1 and a variation in the solvent pressure or in the level or volume of the solvent is measured.
9. The method according to claim 8, wherein:

   - if a decrease of variation in the solvent pressure, or in the level or volume of the solvent, greater than a threshold value is not measured, one or more variations in the solvent pressure are performed;

   - and/or the measurement of variation in the solvent pressure or in the level or volume of the solvent is iterated, and possibly, one or more variations in the solvent pressure are performed.
10. The method according to one of claims 1 to 9, wherein:

    - during step a), the solvent is sent (II) to the cartridge (30) without passing through the pump (31) for pumping the ink from the cartridge, or (III) by passing through said pump (31);

    - and/or during step b), at least a portion of the solvent is transferred towards an intermediate tank (110), separated from the main tank (10).
11. The ink circuit of a continuous ink-jet printer, comprising a tank (10), referred to as the main tank, a pump (31) for pumping the ink towards the tank (10), means (300) for joining an ink cartridge (30) to said circuit, means (32-35, 320, 340, 341, 343, 344) for fluid connection between said means (300) for joining an ink cartridge (30) to the circuit and the tank (10), and means (3) for controlling the printer, these means being provided for:

    - a) sending solvent, at a pressure P1, up into said means (300) for joining an ink cartridge (30) to the circuit, through at least a part of said means for fluid connection, the solvent flowing in said part in the reverse direction (II) to the flowing direction (I) of the ink, when the latter is sent from the ink cartridge (30) towards the tank (10);

    - b) pumping at least a portion of a solvent, present in said means (300) for joining an ink cartridge (30) to the circuit and in at least a part of said means for fluid connection.
12. The ink circuit according to claim 11, comprising means (15) for measuring an ink level in the main tank, said means (3) for controlling the printer enabling a residual ink level in an ink cartridge connected to the means for fluid connection to be computed.
13. The ink circuit according to one of claims 11 or 12, further comprising an intermediate tank (110), separate from the main tank (10) and means (36, 31a) for transferring at least a portion of a fluid, present in said means (300) for joining an ink cartridge (30) to the circuit and in at least a part of said means for fluid connection, towards said intermediate tank (110).
14. The ink circuit according to one of claims 11 to 13, further comprising:

    - means (345, 35, 340, 32, 320) for sending solvent up into said means (300) for joining an ink cartridge (30) to the circuit, through at least a part of said means for fluid connection, but without circulating the solvent through the pump for pumping the ink from the cartridge;

    - and/or means (345, 35, 343, 320) for sending the solvent up into said means (300) for joining an ink cartridge (30) to the circuit, through at least a part of said means for fluid connection, by circulating the solvent through the pump for pumping the ink from the cartridge.
15. The ink circuit according to one of claims 11 to 14, further comprising means for detecting the clogged state of at least a part of SAID means for fluid connection between the ink cartridge and the tank, for example means for measuring the variation in the level of a fluid in the main tank.
16. The ink circuit according to claim 15, comprising:

    - means for maintaining a fluid under pressure in the circuit, as well as means for measuring a variation in fluid pressure or in a level or volume of this fluid;

    - and/or means for performing one or more pressure variations of the solvent, especially in the case where the means for measuring a variation in pressure do not detect a decrease in the fluid pressure, or in the level or volume of the fluid, greater than a threshold value;

    - and/or means for performing or reiterating one or more variations in fluid pressure in the circuit, for example if a variation in fluid pressure or in a level or volume of this fluid is not detected.
17. A continuous ink-jet printer, comprising:

    - an ink circuit according to one of claims 11 to 16,

    - a printing head (1),

    - hydraulic connection means, for bringing, from the ink tank, an ink to be printed to the printing head (1) and sending, towards said ink circuit, an ink to be retrieved from the printing head (1),

    - electrical connection means for supplying power to said printing head.

Images