EP0968831B1 - Ink circuit, ink jet printer and packaging machine or conveyor employing such a circuit - Google Patents

Description

Technical area

The present invention relates to a circuit inkjet, as well as an inkjet machine and packaging machine, or a conveyor, works such a circuit.

State of the art

A device of the known art is described in patent application EP-A-0 646 470.

Another device of the known art is described in US-A-4,862,192. This device is a inkjet dot printer, with one circuit ink system which includes a device for transferring thick ink from a first supply tank and, independently of this, of the additive of a second supply tank, in a room ink. Ink from this ink chamber is supplied under pressure to a writing head. Of the ink is returned to the ink chamber through a recovery channel, passing through the writing head and recovering the ink droplets that have not been diverted for writing purposes. The device transfer uses pressurized air to transport ink between an ink tank, connected to the writing head, a reservoir of mixture, connected to the feed tanks, and a recovery tank, connected to the recovery. The mixing tank can be alternately connected to a suction line or to a delivery line.

• il nécessite l'utilisation d'un régulateur de pression d'air qui doit avoir de nombreuses qualités: précision, rapidité, pas d'hystérésis pour ne pas modifier les conditions de fonctionnement de l'imprimante, avoir un diamètre de passage important à l'échappement pour ne pas entraíner une surpression lors des transferts d'encre venant avec un débit important de la pompe ;
• il ne permet pas une régulation de vitesse des gouttes du jet d'encre ;
• il comporte un régulateur de pression de précision, qui est manuel ;
• il comporte deux autres régulateurs de pression d'air, (ce qui porte à trois le nombre de régulateurs utilisés) ;
• il utilise une pompe (un volume) de transfert de cylindrée importante, qui est unidirectionnelle. Cette pompe non réversible ne permet pas de réaliser rapidement tous les cycles nécessaires pour une vidange ou un rinçage imprimante ou un changement de couleur d'encre ;
• il utilise un filtre principal, en aval de l'accumulateur, qui nécessite un ajustement permanent de la pression de fonctionnement pour compenser un colmatage de celui-ci ;
• l'ajout d'additif est fonction des conditions de fonctionnement et nécessite un réglage manuel ;
• la séparation électrique/hydraulique est réalisée en utilisant des électrovannes qui commandent des vannes à commande pneumatique. Ce principe de relayage augmente le nombre des composants (aspect fiabilité et coût) ;
• il comporte des composants intégrés à l'intérieur d'un bloc usiné ;
• il n'y a pas de capteur de température. Des variations de température peuvent donc être interprétées comme des variations de qualité d'encre ;

This device has many drawbacks:

• it requires the use of an air pressure regulator which must have many qualities: precision, speed, no hysteresis so as not to modify the operating conditions of the printer, have a large passage diameter to l 'exhaust not to cause an overpressure during ink transfers coming with a large flow of the pump;
• it does not allow speed regulation of the inkjet drops;
• it has a precision pressure regulator, which is manual;
• it has two other air pressure regulators (bringing the number of regulators used to three);
• it uses a large displacement transfer pump (volume), which is unidirectional. This non-reversible pump does not make it possible to quickly carry out all the cycles necessary for emptying or rinsing the printer or changing the ink color;
• it uses a main filter, downstream of the accumulator, which requires a permanent adjustment of the operating pressure to compensate for clogging of the latter;
• the addition of additive depends on the operating conditions and requires manual adjustment;
• electrical / hydraulic separation is achieved using solenoid valves which control pneumatically operated valves. This relaying principle increases the number of components (reliability and cost aspect);
• it includes components integrated inside a machined block;
• there is no temperature sensor. Variations in temperature can therefore be interpreted as variations in ink quality;

The subject of the invention is an ink circuit allowing to overcome these various drawbacks.

Statement of the invention

The present invention describes an ink circuit comprising in particular an ink cartridge, a additive cartridge, recovery tank, accumulator, main filter, solenoid valves, an ink transfer pump fitted with a pressure and temperature, which provides information on hydraulic and thermal conditions operation, an air pressure regulator; this ink circuit being characterized in that it comprises a double-sided support block comprising one side hydropneumatic and an electronic face allowing separate the hydraulic, pneumatic and electronic, all functional components being mounted outdoors on either of the two faces.

Advantageously, the relative provision of certain components helps improve the overall functionality of the ink system: air / ink separation is ensured by a provision components working in air in the upper part of the working circuit and components mainly in ink in the lower part of this same circuit (natural separation by gravity). Else hand, the pump is located below the recovery and accumulator so as to ensure naturally a purge of this pump.

In the accumulator, a first regulation of pressure is ensured in liquid by the pump then that a second regulation is ensured in air by means two solenoid valves, one being arranged between the accumulator and one (or more) pressurization (s) of head through one (or more) orifice (s) calibrated, and the other between the calibrated orifice (s) and the pressure regulator.

The first solenoid valve inflates or deflate the accumulator independently of the pump.

• pour avoir une pressurisation permanente de la tête, cette électrovanne étant en position ouverte (commande électrique en permanence) ;
• pour éliminer la pressurisation, la commande de cette électrovanne étant désactivée.

The second solenoid valve controls the head pressurization; this option being directly controlled by software:

• to have a permanent pressurization of the head, this solenoid valve being in the open position (permanent electrical control);
• to eliminate pressurization, the control of this solenoid valve being deactivated.

A third solenoid valve controls the supply of a venturi (generation of depression). This solenoid valve in particular makes it possible to stop the vacuum when stopping the ink jet (s). This avoids in particular the quality drift ink (unnecessary evaporation) that occurs when stopped inkjet on circuits that do not have the possibility of stopping the generation of depression.

Advantageously, the pressure sensor, which can be located in the pump, allows to control the driving pressure of the pump. The control cycle of the driving pressure is controlled by solenoid valves.

The pressure read by the pressure sensor / temperature is then very close to the pressure reigning in the room. This pressure is also very close to the pressure prevailing at the outlet of the pressure regulator. This sensor plays a role pressure switch and is also used for check the presence of the air network.

The pressure and temperature sensor allows, during the adjustment parameters phase machine operation, inquire about the regulated pressure at the regulator outlet and on the vacuum in the recovery tank. On other circuits of the prior art, these information is given by a needle pressure gauge (only to indicate the regulated pressure) and a needle vacuum gauge (only to indicate the operating vacuum). This sensor allows avoid the multiplicity of components and gives a more precise and simpler information (the level of pressure is read directly on the machine screen) than needle indicators. This information is directly exploitable by software.

Advantageously, the hydraulic connections and tires inside the circuit are done without pipe and without any connection and are directly integrated by molding in the block in the form of canals. The hydraulic connections with the head are made by self-sealing quick couplings. The air filters are mounted on the block by a system of quick fixing (screwing or bayonet type). No hose is only linked to these filters so the change of these elements becomes a simple and clean operation no tools required (assembly and disassembly possible by hand).

In addition, the accessibility of ink cartridges and additive and the main filter associated with the use of the reversible pump ensures a quick change in color.

Advantageously, the ink circuit includes a accumulator with double pressure regulation (by air or by liquid). The first regulation works in liquid by means of the pump and corresponds to ink supply of the jet; the second regulation works in air.

This air regulation allows in particular to take over from liquid regulation when the ink tanks are empty. We thus use all the ink contained in the machine (including that of the accumulator) before declaring a blocking fault for the machine. She permits also to maintain a stable pressure in this accumulator during the setting cycle cartridge atmospheric pressure. She permits also to supply the air pocket of the accumulator without going through the pump. She also allows to vary very quickly and on the full extent (ranging from the depression generated by the venturi up to the regulator outlet pressure) the pressure prevailing in this accumulator, these variations rapid and controlled pressure prevailing in the accumulator being used in particular for stop and start cycles of the jet (s) or for fill the accumulator quickly (possibility of vacuuming the accumulator). The air pressure regulation of the accumulator is associated with a power supply time of the control solenoid valve while the pressure in the control solenoid valve while the pressure in upstream of the solenoid valve is either the pressure atmospheric when the solenoid valve is closed and we want to reduce the accumulator pressure, either the regulated pressure present at the outlet of the regulator when the solenoid valve is open and you want to increase the accumulator pressure.

Advantageously, the ink circuit includes a main filter for the ink that is located between the pump and accumulator.

Advantageously, the ink circuit includes a only level detector which is non-contact (security intrinsic by construction); a condenser programmable efficiency (depending on type of ink, room temperature, cycles in progress ...) located at the outlet of the recovery tank to condense and recover the volatile components of the ink, this condenser being for example made from a Peltier cell.

Advantageously, the ink circuit includes a adjustable venturi (vacuum generation) protected by a coalescing filter. This coalescing filter located at the input of the control circuit and ensures the quality of air (levels of pollution, relative humidity and amount of oil). The purge of this filter is a purge permanent through a calibrated orifice. Such purge principle is without any moving parts, which gives it a level of reliability much higher than existing automatic systems.

Advantageously, the outputs of the filter 31 and of the venturi are placed nearby so as to achieve a phenomenon of dilution of the venturi discharges.

The electronic and fluidic assemblies are continuously swept by an air flow having a quality controlled by the coalescing filter. These sweeps creating a slight overpressure inside of the machine, this gives a protection index high for dust (IP6X for example).

The scans of the electronic parts and fluid remain present when the machine stops. The functioning of these scans is only conditioned by the presence of the air network at the inlet of the filter.

The outputs of the coalescing filter and the venturi are connected on the same "T" component. The third orifice of this "T" is connected to the outside of machine, which makes it possible to dilute the vapors of solvent released to the outside, resulting in very low well below tolerated levels. In variant of realization one can also obtain the same effect without connecting the two outputs (filter and venturi) but by connecting them individually lower part of the machine. The two connections will be then located close to each other.

Advantageously the ink cartridges and of additive are tight and kept at a pressure close to atmospheric pressure by air from the accumulator, thanks to an adapted cycle of several solenoid valves, the operation being controlled by the Pressure sensor.

The invention also relates to a inkjet using such an ink circuit and a packaging machine, or conveyor, using such an ink circuit.

• la réalisation d'un circuit électrohydropneumatique autonome intégrant l'ensemble des capteurs et actionneurs nécessaires pour son fonctionnement et l'électronique de pilotage associée. Le circuit d'encre constitue un ensemble autonome assimilable à un automate contrôlé par une liaison série de données bidirectionnelles. Cette architecture permet d'une part de monter et de tester de façon autonome l'ensemble du circuit, d'autre part d'utiliser ce circuit comme un composant dans des applications spécifiques (impression multicolore par exemple) ;
• la simplicité et la très bonne séparation des ensembles (hydraulique, pneumatique, électronique) : deux faces dont une face hydropneumatique et une face électronique. Cette séparation dans la disposition des composants permet de distinguer très facilement la zone fluidique (côté hydraulique) et la zone électronique avec un avantage évident pour la sécurité de fonctionnement ;
• la réalisation d'un circuit hydraulique double face avec facilités de fabrication, d'accès et de maintenance. Tous les composants fonctionnels (filtres, venturi, pompe, électrovannes, capteur de pression et niveau, condenseur, ...) sont montés à l'extérieur sur l'une ou l'autre des faces et donc rapidement accessibles;
• la réalisation d'un circuit fermé (isolé de l'air ambiant). A l'arrêt de la machine le circuit se trouve isolé de l'extérieur, ce qui permet d'éviter les phénomènes de séchage associés aux échanges air/encre ;
• l'utilisation d'un régulateur de pression d'air à commande numérique ;
• l'intégration d'un capteur de pression et de température dans la pompe de transfert d'encre ;
• l'utilisation d'un récupérateur de solvant (par exemple condenseur avec cellule à effet Peltier) à efficacité programmable ;
• la position particulière du filtre principal permettant d'envisager :
  • une régulation optimisée de la qualité de l'encre, on peut noter en particulier que le colmatage du filtre n'influence pas la qualité de l'encre,
  • une détermination automatisée du changement du filtre,
• l'utilisation d'un filtre à coalescence pour protéger le venturi qui est un élément sensible ;
• la détermination des niveaux d'encre dans les différents volumes par la pompe ;
• l'utilisation d'une pompe de transfert d'encre à commande entièrement pneumatique. Cette pompe réversible assure l'ensemble des échanges bidirectionnels de liquide entre tous ses voisins (cartouches et réservoirs) ;
• un bilan thermique très faible lié au fait que le "moteur" de l'imprimante est l'air sous pression du réseau usine, ce qui permet de prédire une élévation interne de température très faible ( <5°C ).

The advantages of the ink circuit of the invention are as follows:

• the realization of an autonomous electrohydropneumatic circuit integrating all the sensors and actuators necessary for its operation and the associated control electronics. The ink circuit constitutes an autonomous assembly comparable to a PLC controlled by a bidirectional serial data link. This architecture allows on the one hand to assemble and test the entire circuit autonomously, on the other hand to use this circuit as a component in specific applications (multicolored printing for example);
• the simplicity and very good separation of the assemblies (hydraulic, pneumatic, electronic): two faces including a hydropneumatic face and an electronic face. This separation in the arrangement of the components makes it very easy to distinguish the fluidic zone (hydraulic side) and the electronic zone with an obvious advantage for operational safety;
• the realization of a double-sided hydraulic circuit with manufacturing, access and maintenance facilities. All the functional components (filters, venturi, pump, solenoid valves, pressure and level sensor, condenser, ...) are mounted outside on one or the other of the faces and therefore quickly accessible;
• the creation of a closed circuit (isolated from the ambient air). When the machine stops, the circuit is isolated from the outside, which avoids the drying phenomena associated with air / ink exchanges;
• the use of a numerically controlled air pressure regulator;
• integration of a pressure and temperature sensor in the ink transfer pump;
• the use of a solvent recuperator (for example condenser with Peltier effect cell) with programmable efficiency;
• the particular position of the main filter to consider:
  • an optimized regulation of the quality of the ink, it can be noted in particular that the clogging of the filter does not influence the quality of the ink,
  • an automated determination of the filter change,
• the use of a coalescing filter to protect the venturi which is a sensitive element;
• the determination of the ink levels in the different volumes by the pump;
• the use of a fully pneumatic control ink transfer pump. This reversible pump ensures all bidirectional exchanges of liquid between all of its neighbors (cartridges and tanks);
• a very low thermal balance linked to the fact that the "engine" of the printer is pressurized air from the factory network, which makes it possible to predict an internal rise in temperature very low (<5 ° C).

• de réguler de manière continue la vitesse des gouttes du jet d'encre ;
• de réguler de manière électronique la pression, avec un asservissement permanent ;
• de transférer le liquide dans n'importe quelle condition. La pompe du circuit de l'invention a en effet de nombreuses fonctions :
  • transfert de liquide entre deux réservoirs ;
  • agitation, brassage d'un réservoir ;
  • mesure du volume transféré ;
  • mesure de la pression (dépression) dans un réservoir ;
  • mesure du niveau dans un réservoir. On mesure en particulier la quantité d'air dans le réservoir sous pression (accumulateur), connaissant le volume total de cet accumulateur, on en déduit par différence le volume d'encre et surtout le niveau d'encre dans cet accumulateur ;
  • contrôle de la pression du réseau ;
• de décorréler le niveau de colmatage du filtre principal, qui est situé entre la pompe et l'accumulateur, de la viscosité de l'encre, la pression étant compensée de manière automatique. Une mesure dynamique (calcul de l'énergie de transfert dans l'accumulateur) permet de savoir si le filtre est colmaté ;
• de ne plus avoir l'ajout d'additif dépendant des conditions de fonctionnement (tout passe par la pompe qui a un volume de chambre connu) ;
• de réaliser la séparation électrique/hydraulique à l'intérieur des électrovannes en utilisant des membranes séparatrices qui réalisent une séparation physique entre partie électrique et partie hydraulique, les électrovannes étant donc commandées directement ;
• d'utiliser un circuit double face avec deux compartiments isolés et pressurisés, la maintenance premier niveau ayant lieu seulement dans le compartiment hydraulique à l'avant de la machine ;
• d'utiliser un capteur de pression et de température intégré à la pompe, ce qui permet de maítriser la qualité de l'encre ;
• d'utiliser un détecteur de niveau sans contact disposé sur la paroi du réservoir de récupération. Ce capteur permet de connaítre (sortie analogique ou plusieurs valeurs de niveau) le niveau et donc le volume de l'encre contenue dans le réservoir de récupération ;
• d'utiliser la connaissance des volumes de l'encre contenue dans le réservoir de récupération , dans l'accumulateur et dans la chambre de la pompe pour pouvoir entièrement maítriser les corrections de concentration en additif nécessaires au maintien de la qualité de l'encre ;
• d'utiliser un condenseur (par exemple à effet Peltier) dont on peut piloter l'efficacité en fonction de la température selon les caractéristiques de fonctionnement de manière à rejeter moins de vapeurs des composants volatiles de l'encre.

Unlike the prior art device described above, the ink circuit of the invention allows:

• continuously regulating the speed of the drops of the ink jet;
• regulate the pressure electronically, with permanent control;
• to transfer the liquid in any condition. The pump of the circuit of the invention has indeed many functions:
  • transfer of liquid between two tanks;
  • agitation, mixing of a tank;
  • measurement of the transferred volume;
  • pressure (vacuum) measurement in a tank;
  • level measurement in a tank. We measure in particular the amount of air in the pressure tank (accumulator), knowing the total volume of this accumulator, we deduce by difference the ink volume and especially the ink level in this accumulator;
  • network pressure control;
• decorrelate the clogging level of the main filter, which is located between the pump and the accumulator, from the viscosity of the ink, the pressure being compensated automatically. A dynamic measurement (calculation of the transfer energy in the accumulator) makes it possible to know if the filter is clogged;
• to no longer have the addition of additives depending on operating conditions (everything goes through the pump which has a known chamber volume);
• to carry out the electrical / hydraulic separation inside the solenoid valves by using separating membranes which produce a physical separation between the electrical part and the hydraulic part, the solenoid valves therefore being controlled directly;
• to use a double-sided circuit with two insulated and pressurized compartments, first level maintenance taking place only in the hydraulic compartment at the front of the machine;
• use a pressure and temperature sensor built into the pump, which allows you to control the quality of the ink;
• use a non-contact level detector on the wall of the recovery tank. This sensor allows to know (analog output or several level values) the level and therefore the volume of the ink contained in the recovery tank;
• to use the knowledge of the volumes of the ink contained in the recovery tank, in the accumulator and in the pump chamber to be able to fully control the additive concentration corrections necessary to maintain the quality of the ink;
• to use a condenser (for example with Peltier effect) whose efficiency can be controlled as a function of the temperature according to the operating characteristics so as to reject less vapors of the volatile components of the ink.

• de diminuer le nombre de composants (tuyaux, raccords, petits blocs supports...) ;
• d'avoir un circuit compact ;
• d'intégrer directement au bloc support les réservoirs (tampon, accumulateur, condenseur) ;
• de diminuer les coûts de manière importante en obtenant directement par moulage le bloc support de l'ensemble des composants ;
• de bien séparer les parties électronique et hydropneumatique (aspect important pour les normes de sécurité) ;
• de limiter les interventions de maintenance premier niveau sur une seule face du circuit (face avant directement accessible par l'opérateur) ;
• de simplifier la maintenance (tous les composants sont accessibles de l'extérieur sans aucun démontage préalable ) ;
• d'obtenir un circuit d'encre autonome et intégrable dans d'autres unités que les imprimantes à jet d'encre : en effet, seuls sont nécessaires de l'énergie électrique, de l'air comprimé et des commandes adaptées (à travers la liaison série de pilotage) pour faire fonctionner le circuit. Ce concept d'autonomie permet de simplifier la fabrication (test d'intégration complet en air à partir d'un ordinateur).

These characteristics of the circuit of the invention allow:

• reduce the number of components (pipes, fittings, small support blocks, etc.);
• to have a compact circuit;
• directly integrate the tanks (buffer, accumulator, condenser) into the support block;
• to reduce costs significantly by obtaining directly by molding the support block of all the components;
• to properly separate the electronic and hydropneumatic parts (important aspect for safety standards);
• limit first level maintenance interventions on one side of the circuit (front side directly accessible by the operator);
• simplify maintenance (all components are accessible from the outside without any prior disassembly);
• to obtain an autonomous ink circuit that can be integrated into other units than inkjet printers: in fact, only electrical energy, compressed air and suitable controls are required (through the control serial link) to operate the circuit. This concept of autonomy simplifies manufacturing (complete integration test in air from a computer).

Brief description of the drawings

• Figures 1 and 2 illustrate the circuit ink of the invention respectively on a view front and rear view;
• Figure 3 illustrates the diagram hydropneumatic of the ink circuit of the invention;
• Figure 4 illustrates the electrical diagram of the ink circuit of the invention;
• Figures 5 and 6 illustrate a machine inkjet using the circuit of the invention.

Detailed description of embodiments

The ink circuit 9, as shown in Figures 1, 2 and 3 includes in particular a cartridge ink 10, an additive cartridge 11, a reservoir of recovery 12 and an accumulator 13, each of these different elements being connected to a pump ink transfer 14, air filters 31 and 44, one ink filter 24, a pressure regulator 30, a condenser 45 and its radiator 47, channels of connection on which are arranged solenoid valves 8 (or 20, 21, 22, 23, 25, 34, 37, 40, 43), and a card electronic control 27 for these various elements.

The front of the circuit, illustrated on the Figure 1, includes the hydraulic components and tires (filters 24, 31 and 44; pump 14; accumulator 13; cartridges 10 and 11; regulator 30) accessible from the outside, the hydraulic components being located in the lower part and the components tires in the upper part. The back side of the circuit, illustrated in Figure 2, includes the electrical and electronic components (solenoid valves 8, condenser 45, pressure / temperature sensor 53, level sensor 50, electronic card 27).

The lower parts of the ink cartridge 10, of the additive cartridge 11, the upper parts and accumulator 13 are connected to the same pump suction-discharge port 14 at through solenoid valves 20, 21, 22 and 23. A so-called "main" filter 24 is disposed between the bottom of accumulator 13 and solenoid valve 23. Bottom of the accumulator 13 is also connected to the head of ink splash. The lower part of the tank recovery 12 is connected to a second orifice discharge-suction of pump 14 through a solenoid valve 25.

• à la pressurisation de tête au travers d'une électrovanne 34 et d'un orifice calibré 35 ;
• à l'accumulateur 13 au travers d'une électrovanne 34, d'un orifice calibré 35a et d'une autre électrovanne 43 ;
• à la pompe 14 et à un orifice de décompression 38 au travers d'une électrovanne 37 ;
• à la pompe 14 ;
• à un rejet extérieur au travers d'une électrovanne 40, d'un orifice calibré réglable 41 et d'un venturi 42, le bas du filtre 31 étant également relié à ce rejet extérieur au travers d'un orifice calibré 46.

The ink circuit 9 also includes a pressure regulator 30 connected at the inlet to the compressed air network (5-10 bars) through an air filter 31 and at the outlet to the electronic scans and ink circuit through two calibrated orifices 32 and 33. The output of the pressure regulator 30 is also connected:

• at the head pressurization through a solenoid valve 34 and a calibrated orifice 35;
• to the accumulator 13 through a solenoid valve 34, a calibrated orifice 35a and another solenoid valve 43;
• to the pump 14 and to a decompression orifice 38 through a solenoid valve 37;
• to the pump 14;
• to an external rejection through a solenoid valve 40, an adjustable calibrated orifice 41 and a venturi 42, the bottom of the filter 31 also being connected to this external rejection through a calibrated orifice 46.

The upper part of the accumulator 13 is connected in common with the solenoid valve 34 and the orifice calibrated 35 by a solenoid valve 43 through the calibrated orifice 35a.

The upper part of the recovery tank 12 is connected to the venturi 42 through a filter 44 and of a condenser 45, and its lower part at the suction of the ink gutter located at the base of the head ink splash. A level sensor, for example a detector 50 is fixed to the wall of the reservoir recovery 12. A pressure / temperature sensor 53 is located in pump 14.

The pressure at the outlet of the pressure regulator 30 is slightly higher than the pressure in the battery 13.

The accumulator 13 is a double system regulation:

• In normal operation:

• the solenoid valve 43 is closed;
• ink is introduced in spurts into the accumulator 13 which has, thanks to its air pocket located in the upper part, an anti-impulsive role hydraulic and acts as a capacitor allowing to smooth the flow curve. The sizing of the pump chamber volumes 14 and the air pocket of the accumulator 13 are such that instantly adding a pump volume in the accumulator does not change so the pressure of this accumulator. Typically a ratio of 200 between the volume of the air pocket and the pump chamber volume is a acceptable lower limit;
• the pressure is constantly measured using of sensor 53;
• elementary ink is added to using pump 14 to replace cyclically the ink consumed by the jet.

• When the ink cartridge 10 and the recovery tank 12 are empty :

• we no longer go through the pump 14; we check the pressure using the sensor 53;
• since we can no longer add ink, because the cartridge 10 and the recovery 12 are empty, the accumulator is empty gently (jet flow) and pressure in it would tend to decrease. Also, in operation normal the solenoid valve 34 is open, we open the solenoid valve 43 intermittently for times very short, which keeps the pressure in the accumulator 13; we add as much air as loss of volume in liquid.

This system 13 makes it possible to obtain an autonomy of several hours, even with an empty ink cartridge. Thanks to these solenoid valves 34 and 43, a very precise pressure regulator whose cycle opening / closing is of the order of a few milliseconds. We can approach a precision of the order of a few millibars. We get a regulator with an accuracy better than one per thousand.

As an example, we obtain an operation optimum (print quality and ink autonomy) for an accumulator 13 comprising proportions of 1/3 air and 2/3 ink. If the proportion of ink increases, we can then use the regulation constituted by the solenoid valves 34 and 43.

When starting up the the invention, it is advantageous to start at high pressure to get the inkjet started properly. We can, to do so, "inflate" the accumulator to the maximum using solenoid valves 34 and 43. This inflation does not requires only a few seconds and therefore only comes practically not increase the start-up time of the machine.

The device of the invention makes it possible to measure the air pocket in the accumulator 13. The ink is repelled with the pump 14. The volume of the layer of air in the accumulator 13 then decreases by .DELTA.V. If the ink flow leaving it is neglected during this time, there is a pressure variation ΔP such that: .DELTA.P P = α .DELTA.V V

The coefficient α (close to 1) being known, ΔV being the displacement of the pump, V the volume of the bag of air, P and ΔP being measured using the sensor 53, we can deduce V. We can use a "magnifying glass" electronic for the measurement of ΔP if the resolution of the converter is not sufficient.

• un microprocesseur 55 par exemple de type µPD78F0058 muni de son programme de fonctionnement ;
• différentes interfaces 56,57 et 58 de sortie pour piloter :
  • les électrovannes 8 ;
  • le condenseur 45 ;
  • un agitateur 38 ;
  • et des voyants de contrôle situés sur la carte ;
• différentes interfaces 60 et 61 d'entrée pour recevoir des signaux en provenance notamment du capteur de pression / température 53.

The electronic card 27, illustrated in FIG. 4, makes it possible to control these different elements. She understands :

• a microprocessor 55 for example of the µPD78F0058 type provided with its operating program;
• different output interfaces 56, 57 and 58 to control:
  • the solenoid valves 8;
  • the condenser 45;
  • an agitator 38;
  • and control lights located on the card;
• different input interfaces 60 and 61 for receiving signals from in particular the pressure / temperature sensor 53.

The interface circuit 60 includes a pressure amplifier 70, magnifying amplifier 71 (the magnifying glass circuit can be deleted if the converter with sufficient resolution), and a temperature amplifier 72. The card electronics 27 is also connected to contacts security 73 (door opening), and at a terminal 74 by a bidirectional serial control link.

To recap, the circuit of the invention has the following specificities:

• An accumulator 13 with double pressure regulation

• au moyen de la pompe 14 avec des ajouts ou des retraits de liquide. Cette régulation est précise mais lente ;
• au moyen des électrovannes 34 et 43 par ajouts ou retraits d'air : cette régulation est précise et rapide.

The pressure prevailing in the accumulator 13 can be adjusted and maintained:

• by means of the pump 14 with additions or withdrawals of liquid. This regulation is precise but slow;
• by means of solenoid valves 34 and 43 by adding or withdrawing air: this regulation is precise and rapid.

This double regulation is very interesting because it allows you to decouple the use of the pump 14 of maintaining the inkjet speed. The first application is increasing autonomy circuit operation when there is no more ink in the tanks (ink cartridge and recovery tank). We can practically use all the ink in the circuit. Another possibility is the rapid change in the conditions of functioning (increase or decrease in pressure) thanks to air pressure regulation (with solenoid valves 34 and 43). We use this possibility for jet start operations (high pressure start for example), jet stop (low pressure stop for example), operation of maintenance (of the jet or of the machine).

• A temperature measurement (53) at the heart of the system (measurement of the ink temperature)

The pressure sensor 53 is located in the pump 14. In order to better translate the behavior of the circuit, we optimized this sensor by integrating the temperature measurement. This temperature measurement is particularly used for the regulation of ink quality as a function of its temperature (depending on the ambient temperature): you can work at constant concentration (or any other state between constant concentration and viscosity constant) by interpreting the two viscosity measurements and temperature relative to the ink curve "viscosity = f (temperature)"; this specific curve to each of the inks, or even dependent on the batch of manufacturing, is stored in the electronic part of the machine.

• The location of the main filter 24

• la mesure du colmatage du filtre 24 en mesurant l'évolution dans le temps de l'énergie nécessaire au transfert de l'encre de la pompe 14 vers l'accumulateur 13 à travers ce filtre 24 ;
• d'avoir une pression de fonctionnement (pression dans l'accumulateur 13) qui reste indépendante du degré de colmatage du filtre (mesure en statique de la pression accumulateur avec l'électrovanne 23 ouverte).

The main filter 24 is located between the pump 14 and the accumulator 13. This privileged location allows:

• measuring the clogging of the filter 24 by measuring the change over time of the energy necessary for the transfer of the ink from the pump 14 to the accumulator 13 through this filter 24;
• to have an operating pressure (pressure in the accumulator 13) which remains independent of the degree of clogging of the filter (static measurement of the accumulator pressure with the solenoid valve 23 open).

• The use of a traditional air pressure regulator 30

The circuit equipped with an air regulator adapting to network conditions (with solenoid valves 34 and 43), no performance specific to the input regulator 30. The only operating condition of the circuit is to have a pressure at the outlet of the regulator 30 higher than the operating pressure. The role of 30 input regulator is only to avoid strong variations in pressure (direct connection on the network would present this risk). On the other hand, a submicron filter, with permanent purge, associated with this regulator, allows to obtain an air quality (absence water, oil and impurities) compatible with the circuit functionality.

• A re-airing of the cartridges 10 and 11 by the accumulator 13

Pumping the liquid into the cartridges tight 10 and 11 leads to a depression of these last. To guarantee performance of suction of the pump 14 in the cartridges 10 and 11, it is necessary to maintain a pressure level in these cartridges close to atmospheric pressure. This is achieved by means of the air from the accumulator 13 via solenoid valve 22. The pressure 53 built into the pump 14 controls the maneuver with precision. This principle avoids an air intake to the atmosphere. Indeed, if by example solenoid valve 22 had its inlet port at atmospheric pressure, then we would risk drying phenomenon (therefore sticking) on this valve.

On the contrary, the circuit of the invention is a closed circuit for this type of sequence. We can also optimize the operating sequences so that the solenoid valve 22 has its two liquid orifices during practically the entire operation of the printer, the passage of air from the solenoid valves being very brief and being associated only with the cycle of "re-inflation" of the cartridges.

• Resuscitation of cartridges 10 and 11 by ambient air

A variant of refilling cartridges can be obtained by using the solenoid valve 22a. To to avoid the risk of sticking of this solenoid valve the latter is placed between the solenoid valve 21 and the additive cartridge. Indeed the additive dries without leave dry extract and therefore without the possibility of creating a sticking situation.

The re-airing of the additive cartridge is made by the opening of this solenoid valve 22a.

The refilling of the ink cartridge is done by simultaneous opening of the solenoid valves 22a, 21 and 20.

• The presence of a single level 50 detector

One of the main functions of this type of circuit is to avoid ink transfer to the air parts (risk of ink drying, therefore bonding of the solenoid valves). The only point no controllable by the pressure sensor 53 is the level ink in the recovery tank 12. To avoid any serious operating accident (tank 12 overflow), we fitted this tank recovery 12 of a level 50 detector.

In addition, this level 50 detector (type hall or capacitive effect with non-contact measurement at through the tank wall) provides security total. The technology of the sensor used allows the times an all or nothing measurement (for determining one or more thresholds for example) or a measurement in continuous (with an analog level image output liquid for example). Considering the high flammability of the inks used (risk explosion), the use of a contactless sensor (no electrical contact in the ink) allows to obtain by construction an intrinsic security of operation.

• A protective filter 44 for the venturi 42

This filter 44 is much smaller than that of the prior art device described above.

• A recovery circuit made with a controlled supply venturi

The depression of the reservoir of recovery is ensured by the venturi 42. This venturi is supplied with pressurized air when the solenoid valve 40 is open. A few seconds later stopping the jet, the solenoid valve 40 is closed, which avoids the risk of the tank drying out recovery for a long stop. Furthermore this solenoid valve 40 allows by being closed to avoid a evaporation of volatile components while the jet is not running. This avoids an evolution of the ink quality for waiting periods of using the printer. These more technical and economic justify the presence of this solenoid valve 40 not present on the known circuits of prior art.

• A Peltier cell condenser 45

The principle of such a condenser 45 is well known to those skilled in the art and consists in using the cold source of this system to condense and therefore recover volatile ink components (reduction additive consumption, therefore costs for the customer). Originality by compared to the same principle used in devices of known art consists in not supplying permanently this component, which allows to adapt its efficiency. When you want to reduce the effectiveness of system, its feeding time is reduced. The modulation of the power supply results in modulation of efficiency. This principle of modulation allows an adaptation of the efficiency according to the type of head used and the type of ink. This modulation also improves the time of response of the ink quality control.

• A central pump 14

Fluid transfers between different volumes is done by a pump 14 located in the center of the circuit. This pump 14 plays the role of sorting station. It is fitted with a pressure sensor 53. We have added temperature measurement functionality to sensor so that you can manage the ink quality (measures the ink temperature at heart of the system).

The ink circuit 9 of the invention can be included in an inkjet machine, as shown in Figures 5 and 6. In these Figures 5 and 6 are shown a frame 80 on which come position a front door 81, a rear cowling 82, an operator interface 83 which can be a screen + a touch screen, graphic screen + keyboard or alphanumeric or graphic screen + a few keys. In Figure 6 is shown a support area 84 or attaches the circuit 9 of the invention; this zone support allows to isolate inside the machine the hydraulic and electric compartment (standards aspect of security).

But it can also be sold in O.E.M. (or "Original Equipment Manufacturer") to manufacturers packaging machines, or conveyor, which want to integrate the inkjet function into their machine. The device of the invention can indeed be present in the form of an electronic block of ink circuit connected by a serial link (the messages conveyed can be interpreted by a multipoint protocol, electronics can drive two heads with two colors different). The electronic control unit and the ink circuit can be deported one relative to the other from a few centimeters to several meters.

The modularity of the circuit also allows "battery" use of n circuits (command remote multipoint by a single control unit type 74) for large print applications width black and white or color.

Claims (15)

1. Ink circuit comprising an ink cartridge (10), an additive cartridge (11), a recovery tank (12), a storage tank (13), a main filter (24), solenoid valves (8), an ink transfer pump (14) equipped with a pressure/temperature sensor (53), which provides information on the hydraulic and thermal operating conditions, and an air pressure regulator (30), said ink circuit comprising a double face support unit having a hydropneumatic face and an electronic face making it possible to separate the hydraulic, pneumatic and electronic assemblies, all the functional components being installed outside on one or other of the two faces.
2. Ink circuit according to claim 1, wherein the air/ink separation is ensured by an arrangement of the components functioning in air (30, 31, 32, 33, 34, 35, 35a, 37, 38, 40, 41, 42, 43, 44, 45, 56) in the upper part of the circuit and the components functioning mainly in ink (14, 20, 21, 22, 23, 24, 25, 53) in the lower part of said same circuit.
3. Ink circuit according to claim 1, wherein the hydraulic and pneumatic links take place without any piping and without any connection and are integrated into the support unit in the form of channels.
4. Ink circuit according to claim 1 comprising a double pressure regulation storage tank (13), the first regulation operating in liquid by means of the pump (14) and corresponding to the jet ink supply and the second regulation functions in air.
5. Ink circuit according to claim 1 comprising two solenoid valves (43, 34), one being positioned between the storage tank (13) and the head pressurization or pressurizations through one or more gauged orifices (35) and the other between the gauged orifice or orifices (35) and the pressure regulator (30).
6. Ink circuit according to claim 1, wherein the pump (14) is located below the recovery tank (12) and storage tank (13).
7. Ink circuit according to claim 1, wherein the main filter (24) is located between the pump (14) and the storage tank (13).
8. Ink circuit according to claim 1, comprising a regulatable venturi tube (42) protected by a coalescence filter (44).
9. Ink circuit according to claim 1, wherein the filters (24, 44) are installed on the support unit by a rapid fixing system.
10. Ink circuit according to claim 1 comprising a single, contactless, level detector (50) in the recovery tank.
11. Ink circuit according to claim 1 comprising a programmable efficiency condenser (45) located at the outlet of the recovery tank (12).
12. Ink circuit according to claim 8, wherein the outlets of the filter (31) and venturi tube (42) are positioned close to one another, so as to dilute the venturi tube discharges.
13. Ink circuit according to claim 1, wherein the ink (10) and additive (11) cartridges are tight and maintained at a pressure close to atmospheric pressure either by the air of the storage tank (13) by means of an adapted cycle of several solenoid valves (22; and 20 or 21), or by ambient air by means of an adapted cycle of several solenoid valves (22a, 20, 21), the operations being controlled by the pressure sensor (53).
14. Ink jet machine using an ink circuit according to any one of the claims 1 to 12.
15. Conditioning machine or conveyor using an ink circuit according to any one of the claims 1 to 13.

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