FR3048199B1 - SIMPLIFIED FEEDER OF AN INK CIRCUIT - Google Patents

Abstract

The invention relates to a device for supplying ink and solvent to the printhead (50) of an ink jet printer, comprising: a first reservoir (11) and a second reservoir (12), different from the first, means (60, 61, 64) for collecting in the first reservoir (11) a flow of recovery ink from a gutter of the print head, the first reservoir having a first output ( 111) of liquid, for sending a first liquid from this first reservoir to the printhead, the second reservoir having a second liquid outlet (112) for sending a second liquid from this second reservoir to the printhead, means (21, 22, 23) for selectively connecting the first output and / or the second output to a common pump (24) for pressurizing the ink and / or the solvent for sending to the head of printing (50).

Description

SIMPLIFIED FEEDER OF AN INK CIRCUIT

DESCRIPTION

TECHNICAL FIELD AND PRIOR ART The invention relates to the field of continuous inkjet (CIJ) printers.

It also concerns the architecture (layout of the ink circuit) of entry-level CIJ printers in order to minimize their cost.

It also relates to a means of extending the functional range of a membrane pump as a function of temperature.

Continuous ink jet printers (CIJ) are well known in the field of coding and industrial marking of various products, for example for marking barcodes or the expiry date on food products 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 the technology are exploited.

These printers have several standard subsets as shown in Figure 1.

Firstly, a print head 1, generally remote relative to the body of the printer 3, is connected thereto by a umbilicus 2 souplerassembling the hydraulic and electrical connections necessary for the operation of the head giving it a flexibility that facilitates integration on the production line.

The body of the printer 3 (also called a desk or cabinet) usually contains three subassemblies: - an ink circuit 4 in the lower part of the desk (zone 4 '), which allows, on the one hand, to provide ink at the head at a stable pressure and of an adequate quality, and secondly to take charge of ink jets not used for printing, - a controller 5 located at the top of the desk (zone 5 '), capable of managing the sequencing of actions and of carrying out the treatments enabling the activation of the various functions of the ink circuit and the head. an interface 6 which gives the operator the means to put the printer in operation and to be informed about its operation.

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

FIG. 2 schematically represents a printing head 1 of an ICJ printer. It comprises 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 aperiodic stimulation system (not shown) located upstream of the outlet of the nozzle. When the drops 7ne are not intended for printing, they go to a gutter 62 which retrieves it in order to recycle the unused ink through the ink circuit 4.Devices 61 placed along the jet (charge electrodes and deflection) allow, overcontrol, to electrically charge the drops and deflect in an Ed electric field. These are then deviated from their natural trajectory of ejection of the generator of drops. The drops 9 intended for printing escape the gutter and are deposited on the support to be printed 8.

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

An ink circuit of a continuous ink jet printers firstly makes it possible to supply ink under controlled pressure, and possibly a solvent, which augenerates drops of the head 1 and to create a depression to recover non-fluids. used for printing back of the head.

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

Finally, other functions are related to the comfort of the user and the automatic management of certain maintenance operations to ensure an identical operation regardless of the conditions of use. Among these functions we find the solvent rinsing of the head (drop generator, nozzle, gutter), the preventive maintenance aid such as the replacement of limited-life components (filters, pumps).

These different functions have different purposes and technical requirements. They are activated and sequenced by the controller 5 of the printer that will be all the more complex as the number and sophistication of functions will begreat.

Some current printers are designed in a modular way in order to facilitate the maintenance of the machine which is carried out by the rapid exchange and without special tools of certain modules. These can be more or less complex functional subassemblies of which one or more elements are components with a limited lifetime (eg wear components) or components whose performance degrades with the time of use (e.g. clogging of filters). This solution, in general, adds additional costs to the strict realization of the function performed by the module because it is necessary to provide an autonomous structure for the module, electrical connectors, hydraulic connection members possibly self-sealing to prevent the flow of fluids during the replacement of the module, and various other components that would not be necessary if the module was not present.

An example of a modular device is given in FIG. 1 of WO2012066356. The hydraulic circuit which is shown implements exchangeable modules (references 50, 60 in this Figure 1). This circuit is very complex, uses a large number of components; in particular, it uses many self-sealing connectors (73) for isolating the modules (50 and 60) of the body of the ink circuit at the moment of disconnection and thus to avoid fluid flows.

In other words, the presence of complex modules exchangeable in blockgenerates a high technical complexity and therefore additional costs incompatible.

Currently, facilitating maintenance leads to increased costs of the machine. The relative positioning of the components retaining fluids and interconnected with each other, brings constraints related to the gravitational flow of fluids.

More generally, to provide the user with a higher and higher level of user comfort, more and more sophisticated performances making it possible to address applications that are becoming increasingly difficult to satisfy, the current printers are seeing their complexity increase in terms of sophistication and quantity of components.

Another example is given in application WO2009049135.

According to another aspect of the known machines, the forced circulation of fluids and the control of their flow (closing / opening of conduits, switching) are functions which are expensive to carry out, in particular for questions of reliability of operation. They implement, in general, pumps and solenoid valves or valves, particularly to ensure the pressurization of ink and possibly solvent to the head, the creation of a depression for recovery and bleeding from the head, or transferring ink or solvent from one place to another in the ink circuit.

In yet another aspect of the known machines, the vast majority of them use gear pump technology for pressurizing the ink and, in some cases, for creating the recovery depression. These pumps of high performance and high capacity are very suitable from a technical point of view. In particular, they can handle difficult inks and they have a long life. But, they are very expensive. In general, the ink circuit of known machines is an expensive element, because of the many hydraulic components to implement.

There is therefore the problem of performing all or part of the functions of an ink circuit, in a type CIJ printer, at lower cost and with a reduced number of components, while ensuring a minimum of reliability. It is therefore sought to implement as few components as possible, especially for functions such as the management of consumables and / or the control and maintenance of the ink quality and / or solvent rinsing of the head.

In particular, a problem is to reduce the number of hydraulic components and simplify the interconnection of these components. Despite this, the satisfaction of the user must be ensured so that the effort on this reduction of the number of components does not affect performance or reliability.

Another problem, related to the complexity of currently known machines, is the need for highly qualified operators. For example, maintenance intervals can be very complex.

There is therefore a need for a printer suitable for handling by low-training operators.

In another aspect, the ink circuit has a large number of hydraulic, hydroelectric, sensor, and so on components. Indeed, modern printers have many more and more sophisticated and precise functions. The hydraulic components (pumps, solenoid valves, self-sealing connections, filters, various sensors) are present or are sized to meet a level of quality, reliability, performance and service to the user. And the maintenance functions consume components because they are often automated.

There is therefore also a need for an ink circuit architecture which minimizes the number of components while ensuring a good level of performance and reliability as well as an ease of maintenance allowing rapid interventions, minimizing the risk of fouling and achievable by operators with special training.

There is also the problem of finding an architecture for the regulation of fluids (solvent, ink) of the ink circuit of a printer. A telearchitecture should also minimize the number of components and allow the use of less expensive components while ensuring a good level of performance and reliability.

DISCLOSURE OF THE INVENTION The invention firstly relates to a device, or circuit, for supplying ink and solvent to the print head of an ink jet printer, comprising: at least one first reservoir and a second reservoir, different from the first, means for collecting in the first reservoir a stream of recovery ink from a gutter of the print head, the first reservoir having a first liquid outlet, for sending a first liquid of this first reservoir towards the print head, the second reservoir having a second liquid outlet, for sending a second liquid from said second reservoir to the print head, - selecting means for selectively connecting the first outlet and / or the second output to a second common pressurizing pump of the ink and / or solvent for sending to the print head.

This type of circuit makes it possible to use only one pump, to pump the two liquids, on the one hand the ink and, on the other hand, the solvent. The means selectively connect the first outlet and / or the second outlet to a common pressurizing pump comprises, for example, a valve associated with each reservoir and activated during opening or closing, for discharging or sending the selected liquid to the common pump.

At least one damping device, common to the ink circuit and the solvent circuit, may be provided for damping fluctuations or ripples of ink and / or solvent from the single pump. Preferably, such a damping device comprises means forming a nonreturn valve, to prevent a flow of ink and / or solvent to the common pump.

Such a device or supply circuit may comprise at least a third tank, provided with a third output, the selection means for selectively connect the first output and / or the second output and / or the third output to said common pump.

A pressure sensor may be provided, for measuring an ink pressure and / or solvent sent to the print head.

Means may also be provided for, by means of the selection means, adjusting the viscosity of the ink, depending on the pressure measurements. For example, means may be provided for adding at least a quantity of solvent, as a function of a measured pressure value or pressure variation.

Preferably, said amount of solvent takes into account the dilution of the ink with the solvent.

More preferably, said means make it possible to add a plurality of quantities of solvent, alternated with ink, in order to allow mixing of the solvent and the ink.

To adjust the additions of solvent, the device may furthermore comprise means for calculating a number and / or a frequency of sending (s) an elemental quantity, for example between 0.1 cc and 1 cc, of solvent to the pump and to send this amount of solvent, possibly at the calculated frequency, soternernte with ink shipments to the pump. Thus, a quantity of solvent is sent progressively, in small elemental amounts, which allows mixing with the ink sent between the elementary amounts of solvent.

A device according to the invention may advantageously comprise, below the pump: a first supply path of the ink and / or solvent printing head, this first path possibly comprising a damping device; supply, parallel to the first power supply, for supplying the print head with solvent.

By "downstream" is meant "in the flow direction of the fluid", reservoirs to the print head.

Means, for example a three-way valve, may be provided to select one or the other of the two feed routes, depending on the liquid. For example, the second channel can be reserved exclusively for solvent circulation and will be used during cleaning operations of the circuit with the solvent.

In addition, means may be provided for imposing a pressure of operation at the common pump, for example having at least one duct deretour, towards one of the 2 tanks, since at least one feed duct of the head of impression, this duct return member being disposed from a point downstream of the common pump, and possibly the damping device of the pressure variations or undulations, and comprising means forming a restriction of its flow. When the device comprises 2 feed channels, such a conduit deretour, provided with means forming a restriction, can be provided for each of 2 journeys.

Means may be provided for detecting a blocking of dithering.

Means may be provided to adjust the speed of the pump with a given pressure value, for example these means can proceed by parody to adjust the speed of the pump

Finally, means may be provided to achieve an air purge optionally present in the supply device. The invention also relates to a method for supplying ink and solvent to the printhead of an inkjet printer, comprising the implementation of a device or a circuit as described above. The invention also relates to a method for supplying ink and solvent to the printhead of an ink jet printer, comprising: the collection of ink or solvent, respectively from a first reservoir, containing ink, and a second reservoir, different from the first and containing solvent, using a common pressurizing pump ink and / or solvent, a recovery ink stream in from a printing head channel being sent to the first tank having a first liquid outlet, - sending ink and / or solvent to the print head using the common pump.

Thus, a single pump is used to pump solvent and / or ink and send it to the print head.

A stream of ink and / or solvent may be sent, at the outlet of said common pump, to means for damping ink and / or solvent pressure fluctuations.

An ink and / or solvent pressure measurement sent to the print head can be performed. The viscosity of the ink can be adjusted according to said ink pressure measurement. For example, an amount of solvent is added to the flow of ink which is sent to the print head as a function of a pressure value or a measured pressure variation.

Said amount of solvent may take into account the dilution of the ink with the solvent.

A plurality of amounts of solvent, alternating with ink, can be sent to the printing head in order to allow mixing of the solvent and the ink. Thus, a quantity of solvent can be sent gradually, in small quantities. elementary, which allows mixing with the ink sent between elementary quantities of solvent. To this end, it is possible to calculate a number and / or a frequency of sending (s) an elementary quantity of solvent to the pump and send this amount of solvent, possibly at the calculated frequency, alternately with shipments of ink to the pump. Advantageously, the elemental amount of solvent added to the volume of the ink circuit, allowing its mixing upstream of the head, produces a relative viscosity variation of less than 1% or a viscosity variation of less than 1% of the nominal viscosity. For example, the elemental amount of solvent added is between 0.1 cm3 and 1 cm3.

To ensure optimal circulation of the ink and / or the solvent, sselects, downstream of the pump: - a first supply path of the print head, for sending it to this ink and / or solvent, or a second feed path, parallel to the first feedstream, for supplying the printing head with solvent.

According to an advantageous embodiment, the speed of the pump is adjusted according to a given pressure value. This makes it possible to take into account the delays, on the supply line of the print head, of various elements, for example of a device for damping pressure variations. The invention also relates to a removable monoblock assembly for an ink circuit of a continuous inkjet printer, comprising at least one plate, of substantially planar shape and extending in a plane (XY) and a first pump, said pressure pump, and a second pump, said recovery pump, fluidic connection means, in order to achieve a fluid flow between, on the one hand, a first fluid inlet, the first pump and a first fluid outlet, and, on the other hand, between a second fluid inlet, the second pump and a second fluid outlet, - at least one connection element, which is fixed to, for example by overlying, said plate and which has a surface, called connection in whichthe said inputs and outputs are touched, this connection surface being substantially perpendicular to the plate, and the flow axis of a fluid through said inputs and outputs being parallel to said plane (XY), a plurality of conduits, passing through said plate for connecting said inputs and outputs.

Such an assembly can be used in, or in combination with, the device or power supply circuit described above or in this application, or still with other circuits in which a removable one-piece assembly is provided or could be used.

At least one of the first pump and the second pump may be a membrane pump.

Said connection element may comprise means for guiding said assembly in translation when it is mounted on the ink circuit.

According to one embodiment, said connection element comprises a groove having a "U" profile, said inlets and outlets opening into a surface which eliminates the bottom of the "U".

In a variant, said connection element forms a bracket defined by a first surface, into which said inlets and outlets open and a surface of support against said plate.

The plate may be part of a housing or enclosure that contains the first pump, the second pump, and fluid connection means. The plate can be removable from the housing. Said plate and the housing may comprise connecting members to allow the opening and closing of the housing by the plate.

Each of said fluid inlets and outlets may comprise an end of a duct provided with a seal.

Such an assembly may comprise at least one fixing element of the assembly on the ink circuit. The connecting element can be removable with respect to said plate. According to one embodiment, it comprises fastening elements against said plate.

Means may be provided for fixing the assembly on the ink circuit. The invention also relates to a device for damping pulsations or pressure variations of an ink in the ink circuit of a continuous inkjet printer, which device can for example be used in or in combination with, the device or supply circuit described above or in this application, or with other circuits in which a damping device is provided.

It comprises at least one input of the ink in this device and at least one output of the ink of this device, means for damping the fluctuations of pressure of the ink and means forming an anti-return valve being arranged inside the device. device.

According to a particular embodiment, the nonreturn valve meanscomprises a membrane which closes said outlet under the action of damping means of the pressure fluctuations of the ink.

Advantageously, said membrane may also form a seal at the periphery of the device.

For example, the device comprises an interior volume delimited in part by said membrane and in part by a surface in which the inlet and the outlet of the ink open, the outlet being provided with a peripheral lip contrelaquelle said membrane bears under the l action of damping means.

Advantageously, a pad is located near the inlet, to maintain the membrane at a distance from the latter when it closes the outlet.

Pressure fluctuations may be transmitted, via the diaphragm, to a rigid portion disposed between the latter and the damping means. The invention also relates to an inkjet printer, comprising an ink supply device and / or solvent as defined above, and / or implementing a method as defined above and / or comprising a removable one-piece assembly as defined above.

BRIEF DESCRIPTION OF THE FIGURES - FIG. 1 represents a known printer structure; FIG. 2 represents a known structure of a printer head of an ICJ type printer; FIGS. 3A-3E represent exemplary embodiments of FIG. 4A - 4D represent variants or other embodiments of supply circuits according to the invention, - Figures 5A and 5B show curves of evolution of the pressure of FIG. 6 schematically represents the alternation of addition of solvent, in elementary quantity, and addition of ink, - FIG. 7 represents a device for damping variations of depression depending on the temperature, 8A - 8C and 9 represent aspects of embodiment of a component or removable module according to the invention, - Figure 10 represents a removable component according to the invention, mounted in an impress device FIGS. 11A-13 show aspects of another embodiment of a removable component or module according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

According to an exemplary embodiment, illustrated in FIG. 3A, a fluidic circuit 10 according to the invention comprises a first reservoir 11, for containing a first liquid, and a second reservoir 12, for containing a second liquid.

According to one application, the first liquid is ink, and the second liquid is a solvent, for example MEK (methyl ethyl ketone). In another embodiment, the second liquid is ink diluted with solvent.

In the following, reference will be made indifferently to a first liquid or to ink, and to a second liquid, or to a solvent (but, again, the latter may be replaced by diluted ink. below, with reference to solvent, generally also applies to diluted ink). One and / or the other tanks 11, 12 can be filled, using a fluidic circuit or, more simply, by hand, pouring into the reservoir, the corresponding liquid, when the latter is missing. Means 13, 15 may be provided in each of these tanks for measuring the level of the liquid it contains. Such means are for example described in WO2011 / 076810.

Each of these tanks is provided with an outlet lli, 12i of the liquid it contains. The opening or the closing of this outlet can be regulated by means of a valve, respectively 21, 22: the duration of opening more or less great of each of these valves defines the quantity of liquid which is taken from the corresponding tank, in depending on the pressure and flow conditions at the outlet of these valves.

Each of these two outlets brings the sampled liquid to a single pump 24, common to both liquids, which will be able to pump, for exampleuccessively or alternatively, or simultaneously, depending on the open or closed state of the valves 21, 22, ink from the reservoir 11 and solvent from the reservoir 12. A single conduit 23, downstream of the valves, may cause bring to the pump 24 the liquids from the 2 tanks. In particular, the solvent of the tank 12 is pumped by this pump 24 without passing through the tank 11 to be mixed with ink; it can be sent to the print head without being mixed with ink, or by being mixed with ink which has itself been extracted from the reservoir 12.

According to a particular embodiment, a duct 21i (respectively 22i) connects the outlet of the tank 11 (respectively 12) to the inlet of the valve 21 (respectively 22) and a duct 212 (respectively 222) connects the outlet of the latter to the conduit entry 23.

The known systems use a pump for each liquid, so for each tank: there is then a pump for pumping the solvent, and a pump for pumping the ink. The pump for pumping the ink is constantly requested during the printing phases. On the other hand, the pump which sends the solvent operates in a less constant manner, since the sending of solvent is only necessary in certain phases of use of the machine (for example to adjust the viscosity of the ink, or to carry out operations rinsing or cleaning all or part of the circuit) .In the circuit illustrated in the context of the present invention, the single pump 24, common to the two liquids, will operate at the same rate as the pump, dedicated to the pumping of the ink used in the known systems, that is to say almost constantly during the printing phases. Therefore, although used to pump 2 liquids, it is no more solicited than the pump dedicated exclusively to the plumping of the ink in known systems.

A single conduit 25, at the outlet of the pump 24, then makes it possible to send the pumped liquid to the printing head, preferably via means 26 damping, or damper or "anti-pulse", which advantageously disposed at the pump outlet 24, dampen fluctuations or liquid pressure ripples caused by the operation of the pump24 and reduce these fluctuations or ripples to a few mb. Because of the pump 24, for example by the clearance of the opening and closing of the valves of this pump, the liquid flow can vary around a mean value, which can be between 2 and 6 bars and around which the fluctuations can be +/- 1 bar. This ripple can be significant and not very compatible with the operation of an ICJ printer. The drop charge system synchronizes with a phase of the stimulus signal that is stable with respect to the moment when the drop is separated from the jet. Now, this moment is defined for a given jet speed; a change in jet velocity, induced by pressure distortions still perceptible, desynchronize the load periodically relative to the time of separation of the drops, which would disrupt their trajectories and hence the print quality. The means 26 make it possible to eliminate or limit these effects. Such means 26 are for example described in WO 2014/154830. It may be noted that, as illustrated in FIGS. 3D and 3E, two such damping means 26 can be placed in series, or, according to a more complex architecture illustrated in FIG. 3D, on different destronances of the feed line of the head. A detailed description of an exemplary embodiment of the means 26 is given below.

An outlet of the means 26 may be provided with means 28 forming a check valve; alternatively, as explained below, it is the means 26 which can themselves integrate this function of non-return valve.

The means 28 make it possible to block any return of ink towards the means 26, the common line 25 and the pump 24. In the event of stopping the printing machine, ink, which would be returned to the means 26 and / or or to the pump 24et that would remain in these organs during the entire duration of the stop, could affect thefunctions of the latter, (by gluing and / or clogging of the pump or means 26) in particular in the case of the use of a pigment ink whose pigments tend to settle on it.

The fluid can then be sent to the print head 50 by means of one or more conduits 29. One or more filters 42 may be arranged on the fluid path, downstream of the means 26, 28. pressure 36 makes it possible to detect the variations in pressure of the fluid that supplies the print head. The measurement of the pressure in the circuit, downstream of the pump 24 and the means 26, reflects the pressure in the head, and makes it possible to identify the pressure variations in the circuit (therefore in the head). This measurement of the pressure will make it possible to detect, indirectly, the variations of concentration of solvent in the ink. Advantageously, the pressure is detected for a nominal speed of the jet (for example 20 m / s). The detected pressure is compared to a reference pressure for the same nominal speed. In the case of a lack of solvent, it is deduced the possible amount of solvent that must be added to compensate for the deviation from this theoretical measure. The detection of the pressure can be performed at regular intervals, for example between 5 and 10 minutes depending on the operating phases of the machine: this interval may be different depending on whether the printing machine is in the starting phase, or is permanently reg 'impression. It is chosen so that solvent, added to the ink after detection of a lack of solvent, can mix homogeneously with it before the next pressure measurement.

The sensor 36 is preferably disposed in the head 50, but, for reasons of space, can be arranged on the line 29, as shown in Figure 3A.

A circuit is also provided to return the ink, unused during printing, to the ink tank 11.

Thus, ink, recovered in the trough 51 is pumped, with the aid of a pump 64, through one or more ducts 58, 60, 61 and, optionally, a valve 54. filter 59 may be disposed on this return path, since the fluid will be returned to the ink tank 11, and then reused during the printing phases. A duct 56, connected to the head via a valve 52, and joining the duct 58 upstream of the pump 64 and the optional filter 59, can be used for the cleaning or rinsing phases of the head printing 50.

In the system described above, only 2 pumps 24, 64 are used, one for bringing ink and / or solvent to the print head, and the other for bringing unused ink back to the reservoir In addition, the pump 24 and the "anti-pulse" device 26 being common to both ink and solvent circuits, it results in an economy of means, and therefore cost, for this circuit.

As described below, all of the two pumps 24, 64 can be combined in a module 270, 270a (for example as described below and in FIGS. 8A to 13) which can be detached from the remainder of the circuit, thus allowing a change in set of two pumps simultaneously, and quickly.

Preferably, each of these pumps is a diaphragm pump, for example as described in WO 2014/154830. It is recalled that the performance of such a pump is characterized by a network of curves giving the pressure or depression obtained as a function of flow for different powers provided to the engine, an example of these curves is given in Figure 4 of the document. In other words, a network of curves defines the characteristic of the behavior of the pressure as a function of the flow rate of a diaphragm pump. For a given control voltage (which defines the speed of rotation of the pump), the characteristic of the pump is a decreasing function, which starts from a maximum pressure for zero flow to zero pressure for a maximum flow called free flow. .

Means may be provided on the supply line 29, to set the pressure to a certain value, which will allow to set the flow rate of the pump 24, particularly in the case of a diaphragm pump. These means may comprisea way, or a conduit, return 71. Through this conduit, it takes part of the fluid flowing in the line 29, and returns this fluid to the tank 11.This way back is provided a restriction 73, which locally reduces the duct section in which the liquid circulates and which makes it possible to pressurize the fluid sent to the head. Advantageously, this restriction is a stringular restriction, that is to say a point or localized narrowing of a fluid duct whose length is substantially smaller than its diameter, or small in front of its diameter, and which creates a loss of pressure insensitive to the viscosity of the fluid passing through it. A singular unerestriction is a localized narrowing of a fluidic duct whose length L is smaller than its diameter d or small in front of its diameter d. Advantageously, L / d <1/2; according to some examples, L / D is between% and Z (for example D = 0.3 mm and L = 0.1 mm). A restriction with singular behavior can be implemented for which L / D is greater than 1 and can be 10 (in other words, l <L / D <10). The flow rate Q of a singular restriction depends on the pressure difference ΔΡ at its terminals by the relation ΔΡ = Rh (p) × Q2, where Rh is the hydraulic resistance which depends on the density p of the fluid but does not depend on the flavor. Here, the restriction 73 comprises an orifice of diameter, for example 0.3 mm.

Pressure control can be achieved by other means than the combination of a return path and a restriction.

Means 3, for example comprising a processor or microprocessor or a computer and / or an electrical or electronic circuit, for example of a programmable type, make it possible to control and / or control the various hydraulic means of the circuit, in particular the opening and / or the closing the valves21, 22, for example to carry out one or more additions of solvent, the operation of the pump 24, the opening and / or closing of the valves 52, 54. They also make it possible to store and / or process data from level sensors 13, 15 and pressure sensor 36 and / or to identify a blockage of the pump 24. They therefore make it possible to control or control the supply of the circuit with liquids (in ink and / or solvent) as well as the recovering the mixture of ink and solvent from the head. They are therefore programmed for this purpose. These controller means, or these control means, are arranged in the part 5 'of the system or the desk. These means can also be used to transmit printing instructions to the head.

In FIG. 3A, as in FIGS. 3B and 3C, the circuit elements forming part of the umbilicus 19 are represented by a broken line: here, it is a part of the duct 29 and the ducts 56, 58.

The device described above has only 2 pumps and 2 tanks. There is no additional reservoir, downstream of the pump 24. A mixture of the 2 liquids pumped from the 2 tanks 11 and 12 is made in the fluidic ducts in which the two fluids flow: the conduits 23, 25 , the pump 24, and the "anti-pulse" device 26.

Another exemplary embodiment is illustrated in FIG. 3B, which includes all the elements described in connection with the preceding figure, which will not be described here. In this embodiment, means 30, for example a 3-way electromagnetic predictive valve, arranged downstream of the means 28, make it possible to select: a feed of the head 50 with the first liquid, or with a mixture of the first liquid and the second liquid, via a lle way 32d'alimentation of the print head, - or a supply of the head 50 with the only second liquid, through a 2nd channel 34 of the power supply printhead ; it is possible to send to the printing head a clean solvent which does not contain, or has little ink, traces of ink.

The means 30 can be activated (with the aid of the means 3) as a function of the fluid pumped by the pump 24.

The first channel may be provided with the pressure sensor 36, at the aid of which changes in the pressure of the liquid which feeds the head can be detected. As indicated above, it would preferably be disposed in the head 50, but for reasons of it can be positioned on the supply line32. The functions of this sensor are the same as those described above in connection with FIG. 3A.

Each of the two channels may be provided with means for filtering the liquid that it conveys: thus the channel 32 may be provided with filtering means 31, 42 and uses filtering means 44.

The print head may be provided with valves 46, 48 for allowing feeding, respectively by the first channel 32 or by the second channel 34. The opening and closing of these valves may be synchronized with that of the valve 30, but this is not necessary.

Each of the channels 32, 34 comprises one or more conduits connecting the means 30 and the head 50 while incorporating the possible elements (in particular the orle filters) described above.

In this embodiment, the means 28 make it possible to avoid the introduction of ink into the part of the circuit common to the two fluids (the means 26, the common line25 and the pump 24). Thus, during a cleaning or rinsing phase, the pumped solvent upstream of the non-return valve 28 will be preserved from any ink return and may be sent to the line 34 without being polluted with ink.

Another exemplary embodiment is illustrated in FIG. 3C, which comprises all the elements described in connection with the preceding figure, which will not be described here.

In addition, a channel, or a return duct 72, 74 can be provided for each of the channels 32, 34. Via this duct, a part of liquid is withdrawn which circulates, respectively in the channels 32, 34, and this liquid is returned to the tank 11, 12 corresponding. This return path is provided with a restriction 76, 78, which locally reduces the section of the corresponding conduit and which makes it possible to pressurize the liquid sent to the head. These are preferably singular restrictions, whose properties have already been explained above.

According to an exemplary embodiment, each of the restrictions 76, 78comporte an orifice, for example of diameter 0.3 mm.

These return pathways 72, 74 provide part of the security of the system: if there is an increase in pressure, for example due to a risk of clogging in the head 50, then the fluid that can no longer flow by the head iscanalised by way of return 72.

Blocking, even partial, of the restriction 76 can be detected by an increase in the pressure in the circuit, for example when the pressure reaches several bars, for example still 4 bars. The sensor 36 can detect this anomaly, or it is evidenced by a decrease in engine speed. If such an anomaly is detected, it can be signaled to an operator, and / or the machine can be stopped.

Moreover, in the case where the pump 24 is a diaphragm pump, the restrictions 76, 78 make it possible to fix the pressure at the outlet thereof, which constitutes one of the operating parameters of this type of pump (as already explained below). above).

When ink is sent through the pump 24 and the track 32, to the head 50, for example about 90% to 96% of the ink returns through the channel 72, 10% to 4% being sent to the head 'impression. The same proportions apply to the solvent, because of the return path 74, when it is sent to the head 50 by way 34.These proportions can be explained by the low flow rate in the head 50.

In FIGS. 3B and 3C, the umbilicus 19 comprises a part of the feed lines 32, 34 and a part of the ducts 56, 58.

FIGS. 3C and 3E show a structure similar to that of FIG. 3C, but with damping means which are doubled: in FIG. 3D, there are two damping devices 26a, 26b, ensembled on the portion of FIG. supply circuit which is common to the ink and the solvent, enamont the valve 28 and means 30, - in Figure 3E, there are 2 devices 26a, 26b amortization, but one arranged as in Figure 3C, in upstream of the valve 28 and the means 30, while the other is disposed on the line 32, downstream of the means 30. This configuration is justified by the fact that it is more important to achieve a damping pulsations in the ink than in the solvent.

Two damping devices 26a, 26b may be used in other circuit structures according to the invention, in particular in the structures of FIGS. 3A, 3B or 4A (for these 2 figures, the two devices 26a, 26b may be upstream of the valve 28, or one may be upstream of this valve, while the other is downstream means 30).

In the embodiments that have been explained above, at least a portion of the solvent circuit is identical with the ink pressurization circuit.

A single pump 24 makes it possible to supply the print head with the ink and / or solvent required. The solvent of the tank 12 is pumped by this pump 24 without passing through the tank 11 to be mixed with ink; it can be sent to the printing head without having been mixed with ink, or by being mixed with ink which has itself been extracted from the reservoir 12, the mixture then being made in the elements of the fluidic circuit common to the 2 liquids, namely the conduits 23, 25, the pump 24, theishibition device 26 damping. The device described has only 2 pumps and 2 tanks, without additional tank downstream of the pump 24.

Variations of the devices described above, or other embodiments, will be explained below, in particular in connection with FIGS. 4A-4D.

According to a first variant, one or more additional tanks are provided next to the two tanks 11, 12.

This third reservoir is intended to contain a third liquid, different from the first liquid and the second liquid. In one example, it contains a diluted ink, while the other two reservoirs contain, respectively, solvent and undiluted ink. Preferably, the dilution of the ink in this reservoir 12a remains stable over time.

This third tank can be filled using a fluid circuit or, more simply, by hand, pouring the corresponding liquid when it runs out.

This variant is illustrated in FIG. 4A, which concerns the structure of FIG. 3C, but it is also applicable to the structures described in connection with FIGS. 3A and 3B. In this variant, an additional reservoir 12a is provided, having an outlet 12a1, the opening or closing of which can be regulated by means of a valve 22a. This outlet and this valve bring the liquid taken from this reservoir to the pump 24, which is therefore common to all the liquids and which will be able to pump, for example successively or alternatively or simultaneously, depending on the opening state of the different valves, liquids from one or more reservoirs 11 12, 12a. The single conduit 23, downstream of the different valves, makes it possible to bring to the pump 24 the liquid or liquids coming from one or more tanks.

Means 15a for measuring the level of liquid in the third tank may be provided. Examples of such means are given in WO2011 / 076810.

The valve 22a can be controlled or controlled by the means 3, which can also collect and process the data from the level sensor 15a.

In this variant, as in the examples already described previously, the system uses a single pump for all liquids. The advantages already described above are therefore applicable to this variant.

According to another variant, illustrated in FIG. 4B, the different tanks are pressurized, for example by means of one or more air compressor (s) 24a, which means that it is not possible to use a pump 24 or any other device 26. The lavender illustrated in FIG. 4B relates to the structure of FIG. 3B, but the use of the decompressor (s), replacing the means 24, 26, may also concern the structures described with reference to FIGS. 3A or 4A.

The mixture of the two liquids is then made in the part of the fluid circuit that is common to them, namely the conduit 25. The device has only one pump, the pump 64, which allows to bring back ink not used for printing to the tank 11.

Another embodiment is illustrated in FIG. 4C, on which references identical to those of the preceding figures denote identical or corresponding elements thereto.

This time, the two tanks 11, 12 are pressurized, for example with an air compressor, and are connected to a supply conduit 29 without the use of a pump 24. The reservoir 12, designed to contain solvent, can be connected to the conduit 29 at any point 29a, which can be located very downstream with respect to the tank 11 and the valve 21.

As a variant of this FIG. 4C, illustrated in FIG. 4D, the reservoir 12, istrelated to the printing head 50, so that the injection of solvent can be carried out directly in the print head 50, upstream of the, or of the nozzle (s) of the head. Each ink used in an ink jet printer can be associated with a characteristic curve C which gives, for the geometrical characteristics of the nozzle of the print head and the ink circuit of the printer, and for a jet speed Vjet given (eg 20 m / s), the evolution of the pressure (eg nozzle nozzle) as a function of temperature. A schematic example of this curve C is given in FIG. 5A.

More particularly, the pressure, for example at the nozzle, is the result of the sum of: - the dynamic pressure of the jet (term 1), whose speed is constant and controlled, - regular pressure losses (term 2) involving laviscosity ink, singular pressure losses (term 3) involving the volumetric mass of the ink.

We can thus write that the pressure, at the nozzle, during the formation of the drops, results from the sum of the 3 terms above:

(D

With: - p (T) = density of the ink, expressed in kg / m3, - μ (T) = viscosity of the ink, expressed in Pa.s, - Lbuse = length (or depth) of the nozzle, expressed in m, - Rbuse = radius of the nozzle, expressed in m, - K is a characteristic coefficient (or coefficient of singularity) of the ink circuit, it can be determined experimentally or adjusted during calibration, it is without units.

Note that, if the pressure considered was not that at the nozzle, but at a point located at a distance from it, for example upstream of the umbilicus 19, as in the case of the sensor 36 of FIGS. 3A-4D, a similar formula would be obtained, adding to the above formula a pressure term corresponding to the difference in level between the 3 and the print head 1. This term of added pressure can be a parameterememorized in the printing machine, an operator selects when evaluating the elevation. The pressure then continues to reflect the pressure at the nozzle, or is representative of it. From an industrial point of view, it is difficult to guarantee the conservation of geometric and / or mechanical parameters of a printer. For this reason, for an ink circuit having a given structure, it is preferably proceeded to a calibration in order to overcome the geometric and / or mechanical tolerances variable from one ink circuit to another, same structure; or, in the course of time, following an exchange of components (for example a part between the sensor and the nozzle) of the ink circuit, or a change of electronic component of the controller, a calibration of a machine, which may already have been calibrated, may be desirable.

This calibration makes it possible to perform a correction, which consists inrepositioning the reference curve C by shifting it by a difference in pressure, equal to the difference between this curve C and a real operating point under reference conditions (nominal speed of the jet, defined during sizing of the print head (especially when sizing the pacing)) and taking into account characteristics of the ink), for which the curve C is given, and in particular a given concentration or viscosity. The operating point is obtained by at least one pressure measurement in the ink circuit, for example at the nozzle or at another point of the circuit, for a given temperature and for the rated jet velocity, for which the curve C is given . The pressure sensor 36 can be used for this purpose. The pressure measurement will give an image of the viscosity of the ink used, which directly reflects the concentration (or, more exactly, the dilution ratio) of the ink used. Control or control of the concentration can be achieved by following the viscosity parameter, which is the direct image of the quality of the ink.

The jet speed can be kept constant, at the jet speed, by means of the pump 24 which makes it possible to send the ink from the tank 11 to the nozzle or by means 24a in the case of FIGS. 4B-4D. The pump can be part of servo control means, comprising a sensor for measuring the jet velocity in the head, for example a sensor as described in application PCT / EP2010 / 060942.

Thus, FIG. 5A shows a measurement point (Pm, T) that results from a measurement of pressure, at a given temperature, for the selected ink and at the nominal jet speed (for example 20 m / s). for which the curve C is given. At the same temperature, the curve C gives a value P. It is thus possible to obtain a new curve C ', by translation of the initial curve C, of a value Pm-P. This difference is negative if the measuring point is under Curve C, it is pospositive if the measuring point is above the curve C. This correction makes it possible to take into account the variations or the evolution of the geometrical and / or mechanical parameters of the circuit.

Moreover, it can be seen that, according to formula (1) above, the viscosity μ of the ink intervenes in the first order, in the second term. The formula, valid for a given viscosity (known as nominal or theoretical), will therefore be all the less valid as the actual viscosity of the ink used is different from the nominal viscosity. However, differences in viscosity may exist from one batch of ink to another. In other words, the viscosity of the ink actually produced and used (visco_prod) may be different from so-called nominal, of a "theoretical" ink having the same composition.

It is therefore understood that the curve C, or even the curve C 'of FIG. 5A, corresponds to this "theoretical" ink, and not to the ink actually produced and used.

In order to take account of this shift in the actual viscosity with respect to the nominal viscosity, it is therefore possible to apply a correction, which consists of repositioning the curvature C (or C ') by shifting it by a pressure difference, proportional to the difference between the viscosity actually used (visco_prod) and visco_nominal nominal viscosity (cP) - visco_prod (cP):

Diff_pression (mbar) = A * (visco_nominal (cP) - visco_prod (cP))

In this formula, A is a coefficient of proportionality.

If one wishes to take into account the 2 corrections above, the curve C is shifted by a pressure difference which accumulates the 2 correction values: current pressure - reference pressure + Diff_pression.

A new curve C "is obtained, by translation of the Cinitiale curve, of a value equal to this pressure difference.

We can therefore perform a calibration that takes into account the viscosity of the ink actually produced and used.

A method of calibrating a device or a circuit as described in the present application can therefore, according to the teaching above for an encredonne and for a predetermined jet speed value (for example 20m / s), take the difference between the actual viscosity of the ink used and the so-called theoretical viscosity, which is the parameter usually used.

Preferably, such a method also takes into account the correction (equal to the difference between the current pressure and the reference pressure) which takes account of the variations of the geometrical and / or mechanical parameters of the circuit used.

Such a calibration can be carried out before starting the printing operations themselves, but, as regards the correction which takes account of variations of the geometrical and / or mechanical parameters, after having started the printing machine and producing a jet at the speed constant restraint (vitessenominale).

The instructions for performing at least one of the calibration steps above are implemented by the control means 3 (also called "controller"). In particular, it is these instructions that will make it possible to circulate solvent for measuring a pressure Pm, to memorize this measured value, to calculate the pressure difference Pm-P, and / or to calculate the difference in Proportional pressure at visco_nominal (cP) - visco_prod (cP).

The control means 3, already presented above, can ensure the memorization of data relating to the curve C (for example a set of pairs of values (P, T) associated with a nominal jet speed) and / or of data which results from the, or correction (s), as explained above, data relating to the curve. The physical and / or chemical data relating to the ink actually used, and in particular its viscosity (referred to above as "visco-prod"), can be stored in a memory of these same means 3.

Several curves such as the curve C, for example corresponding to several inks, and / or several sets of data, can be stored, for example in the control means 3. A preliminary step before the operation of a printing machine can be check the validity of the memorized or selected curve and / or the stored or selected data set. If a curve or set of data has not been stored or selected, or if a stored or selected curve or set of data does not match the currently used, then an alarm can be triggered to allow correction.

A calibration as described above may be followed by printing by the printer, the ink jet being formed at a reference speed, or the ink pressure being servocontrollable to achieve the resulting pressure. preferably, curve C ".

Once a calibration has been performed, there is a reference curve Cref such as that of FIG. 5B, which gives the evolution of the pressure as a function of the temperature. It may be one of the curves C 'or C "mentioned above, and in broken lines the limits of acceptable fluctuations of the pressure, for example +225 mbar, on either side have been represented. of this curve.

During the use of the machine, the viscosity of the ink used evolves.

Measurements of the pressure variations occurring in the ink circuit will make it possible to measure variations in this viscosity. Indeed, at constant temperature and constant jet speed, a pressure variation is essentially proportional to a change in viscosity, as explained above.

It is therefore possible to estimate, at a given temperature, and for a fixed jet speed, pressure variations in the circuit. The pressure sensor 36 may be used for this purpose, it is preferably the same as that used for the calibration, as explained above, if it is previously implemented.

Such a variation in pressure will translate, the other parameters of the circuit, and in particular the jet speed, being constant, a change in viscosity. Beyond a deviation from the Cref curve (when it is positive) the solvent is injected.

A pressure difference between the value of the pressure sensor and the cell given by the reference curve Cref is due to a difference in viscosity (or deconcentration), according to the following relation:

When the pressure is no longer that of the nozzle, but at another point of the duct, we can take into account additional viscous terms (which result for example from the umbilicus, ...) but these terms are negligible in front of the difference to the nozzle. This is particularly the case when the sensor is positioned on the jet line, in particular downstream of an anti-pulsation device 26. The sensor being on the line of the jet, the additional head losses are low and taken into account in FIG. self-calibration.

This relation (2) makes it possible to measure the variation of the quality of the ink.

As a first approximation, the density varies little with the temperature and the jet speed is controlled continuously, for example by means of pumping the ink taken from the main reservoir (as indicated above, the pump may be part of servo means, comprising a sensor for measuring the jet velocity in the head, for example a sensor as described in application PCT / EP2010 / 060942).

To ensure good ink quality, or consistent quality, a viscosity deviation, detected with the pressure sensor, can then be corrected by a volume of solvent to be added to the ink of the circuit. This volume can be calculated by taking into account the dilution coefficient, which is specific to each ink and can be formulated as follows:

It represents the relative viscosity variation μ which results from a relative variation of the volume of the ink Vr, this relative variation resulting for example from a solvent addition.

In the case of the structures described above in connection with FIGS. 3A-4A, the quantity of solvent to be added can result for example from the following relation (4), which gives the opening time T of the valve 22:

- A and B depend on the actual ink volume ,. A = 1000 / ink volume, B = 2290 / ink volume (in the tank 11) (these coefficients are hydraulic coefficients), - Pref = reference pressure at the nozzle temperature, expressed in mbar, for a speed nominal jet of, for example, 20 m / s,

- ΔΡ = difference between the pressure and the reference pressure, expressed in mbar, - Q is the transfer rate of the pump 24, it depends on the fluid levels in each of the tanks 11 and 12 (the latter, Hu and H12, are shown schematically enfigure 3C.

It can be seen that the amount of solvent to be added takes into account the effects of dilution on the viscosity of the ink via the dilution coefficient.

However, excessive pressure variations can lead to variations in jet velocity that are also too great, and thus to jet instability.

Solvent additions are made in small amounts to limit pressure buildup. In order not to disturb the jet, it is sought to limit the depression variation to less than 1% of the reference pressure. Equation (2) translates this limit of pressure variation into the limit of viscosity variation. For example at 10% of the nominal viscosity. Equation (3) then translates it into a volume of solvent AVr which can be added in a volume Vr in which it will be mixed before being sent to the print head.

For example, for: Cd = 2.6 then AVr / Vr = 3.2%.

For a volume in which mixing can be done, before passing through the head of: V = 10 cc, then: AVr = 0.3 cc.

According to one example, the additions are made in a small quantity, or elemental volume, for example between a few tenths of a cc and 1 cc or a few cc, for example still between 0.1 cc and 1 cc, which makes it possible not to disturb the speed of the jet.

Given the flow rate of the pump, it deduces the opening time tede the valve 22 to obtain this amount. More precisely, the flow in the line connecting the reservoir 12 to the conduit 23 is determined, taking into account the flow rate between the reservoir 11 and the conduit 23, as well as the flow rate of the pump 24, the pressures in the conduits 2I2 and 222 being considered as equal (because these 2 conduits are identical and both connected to the same conduit 23). They are calculated according to the heights Hu and H12 in each of the tanks 11 and 12.

The duration T (s) above, divided by this duration of opening gives the number of openings of this valve 22.

According to one example, the elemental volume, 0.2 cc, is calculated so that a variation of 0.19 cps of the viscosity is obtained, ie a pressure variation of about 12.9 mbar (which does not disturb the operation of the printhead).

The time at which the ink and solvent added are correctly mixed in the circuit, for example 15 s, is also known. This mixing time makes it possible to determine the duration between 2 injections of a small amount of solvent.

Preferably, the calculation of this mixing time takes account of the fact that, in the case of the circuits presented above in connection with FIGS. 3A-4A, the means 26 and 31 advantageously contribute to the mixing of the ink and the added solvent ( this is also the case in the other circuits presented, if these contain damping means). These damping means of the pressure fluctuations contain an internal volume which allows mixing of ink and a small amount of solvent added. Whether or not there are means 26, it will also be possible to take into account the possible presence of circuit components which may contribute to the mixing of the ink and the added solvent.

A plurality of elementary additions of solvent can thus be made to compensate for a pressure variation detected in the circuit, in the form of successive pulses, for example periodic pulses of duration ts and of period t + ts. This is represented in FIG. the slots, when at level "1", represent solvent shipments S, between which ink shipments E are made.

In one example: the elemental addition of solvent is 0.2 cm 3;

- Vajout (refers to the total volume of added solvent) = 29 cm3;

Ncycies (denotes the number of solvent addition cycles) = 144;

In the case of the structures described above in connection with FIGS. 4B-4D, the explanations given above, concerning the link between the variations of depression and the variations of viscosity, up to and including formula (3) , remain valid. A formula similar to formula (4) above can therefore be established, based on the flow rates that result from the action of compressor (s) 24a, the amount of solvent to be added, preferably taking into account the effects of dilution. on the viscosity of the ink via the dilution coefficient. Again, excessive pressure variations can cause jet speed variations too large and therefore instability of the jet speed. In order not to disturb the latter (because of printing operations in progress), the additions are made in small quantities, or by addition of elementary volumes, for example between a few tenths of a cc and 1 cc or a few cc, for example still between 0 , 1 cc and 1 cc. The elementary volume is calculated so that an addition of this volume of solvent disturbs the speed of the jet as little as possible, or that it changes a lower value than a given limit value, for example + 1% of the jet velocity. The inkjet, sent to a print medium, is thus little disturbed by the change in the quality of the ink and / or its pressure which result from the addition of the solvent.

Given the flow rate resulting from the action of the means 24a, the opening time ts of the valve 22 is reduced to obtain this quantity. More specifically, the flow rate in the line connecting the reservoir 12 to the conduit 25 (FIG. 4B) or 29 (FIG. 4C) is determined, taking into account the flow rate between the reservoir 11 and the conduit 25 or 29, as well as the flow rate imposed by the means 24a, the pressures in the ducts212 and 222 being considered equal (because these 2 ducts are both connected to the same duct 25.

The duration T (s) above, divided by this duration of opening gives the number of openings of this valve 22.

Therefore, during printing operations on one or more printing medium (s), it is possible to realize, for example by means of the various devices which have been described above, solvent additions in a very small quantity (still called "micro additions"); each micro-addition has for example a volume less than a few cubic centimeters, or 1 cm3; or alternatively, it is between 5 cm3, or 1 cm3 and 0.01 cm3 or 0.05 cm3. Such micro additions are made successively, with a temporal gap that preferably takes into account the capacity of the circuit to make a mixture of the ink and the solvent. For example, a better homogeneity of the mixture is obtained for a solvent addition in the print head, using a device such as that of FIG. 3A, 3C or 4A. In general, the duration ts may be between a few fractions of a second and a few seconds, for example between 0.1 s and 1 s or 5 s.

We will now describe steps of certain phases of operation of a printing machine according to the invention.

During the start-up phase, the print head 50 can be cleaned. For this purpose, solvent is sent to the head, the valves 22, 48 and 52 are open, and the pumps 24 and 64 (or the means 24a and the pump 64) are activated. Lavanne 52 can also be closed, in which case it is a jet of solvent that is produced by the head 50, which will clean the trough 51, the valve 54 being open.

In the case of the device of FIG. 3C (or 3D-4A), a cancellation blocking 78 (or 76) is detected if the pressure increases until reaching several bars, for example 4 bars.

If the pressure decreases below the lower limit of a run range, a fault can also be reported and / or the system shut down. At the end of this cleaning step, the valve 30 can be tilted to send ink to the print head, via the feed path 32. Thus, the ink can be pressurized and sent to the head 50.

Without a purge step, air, which would then remain in the circuit, could cause pressure fluctuations, and consequently malfunctions of the machine. A purge phase can therefore be carried out, using pumps 24 (or means 24a) and 64, in order to eliminate the air that remains present, for example in damping means 26, and / or in the filter and / or in the umbilicus 19.

To eliminate air, the valve 30 is switched to send ink to the feed path 32. The pump 24 (or the means 24a) is started, circulating ink through the means 26, the valve 30, the filters 31, 42, possibly the restriction 76, and through the umbilicus 19. The air that would eventually be removed in these various elements is then removed.

In yet another aspect, the speed of the pump is adjusted to reach the reference pressure given by the reference curve (FIG. 5B). In fact, the speed of the pump can depend on several parameters, such as viscosity and temperature. In addition, a delay is introduced by the presence of means 26 for attenuating pressure fluctuations.

An example of a method for adjusting the pressure (or the speed of the engine) proceeds by dichotomy, or iteratively, to find the speed adapted to the reference pressure.

These steps make it possible in particular to take into account the influence of the damping means, which introduce a delay.

When the reference pressure is reached, an ink jet can be produced by the head 50. The ink circuit maintains or adjusts the pressure to the reference value.

During the start of the jet, the speed of the motor of the pump 24 can be adjusted.

As already explained above, the pressure can be controlled to detect a blockage of the restriction 76. The pressure can also be controlled to detect a possible pressure drop. If this decreases below a certain limit, for example 1.5 bar, a fault can be reported and / or the printing machine can be stopped.

Finally, to prepare a stop, or after stopping an impression or machine, the common line ink and solvent can be put in solvent (the valve 22 is then activated), using the pump 24 (or means 24a). This makes it possible to prevent the ink remaining in the circuit, and therefore in the pump 24 and / or the damper 26.

An embodiment of the means 26 will be detailed, in connection with FIG. 7. Such an anti-pulsation device may for example be used in a circuit as described above, but also in any other fluid flow circuit. especially for an inkjet printer, in which fluid pressure variations can occur. Such another circuit is for example described in WO2014 / 154830.

This device 26 may have, in view from below or below, a substantially circular shape or that of a regular polygon. It comprises 2 parallel plates 110, 120, assembled together, at their periphery, by means 112, 122, for example a set of threaded or threaded holes and screws, preferably regularly distributed at the periphery of the device. Each of these plates may have the substantially circular shape or a regular polygon mentioned above; it is also seen in Figure 7, the polygonal shape, hexagonal here, of the plate 120.

Each of the plates has an inner face 113, 123 whose peripheries 113p or the flat side portions are opposite one another when the two plates are assembled using means 112,122.

The inner face 113 of the plate 110 is hollowed, its central surface or its central portion 113c, preferably flat, being lowered relative to sapériphérie 113p, an intermediate portion 113i gradually leading from thisperiphery to the central portion. The inner face of the plate 120 may also be hollowed out, for example in the same manner as the inner face 113 of the plate 110, to receive a spring 114 spring.

Between these plates is defined a reception volume 121 of the fluid that enters a 1st opening 124 (which passes through the plate 110) and leaves this volume by an 2e opening 126 (which also passes through the plate 110) and an outlet fitting 128. Levolume home is about a few cubic centimeters, for example between 1cm3 and 10 cm3, for example still 4 cm3.

A spring 114, in spiral, serves to damp the pressure variations of the fluid when it is in the cavity. Other means may be employed, in the place of a spring, to provide this function, for example a mass of material having elastic properties or an air bubble, enclosed in the cavity; for these other means, the structure of the cavity may remain the same as that described above .. In the case of the spring, one end thereof bears against the inner wall 123 of the plate 120. Its other end is turned towards inside the cavity. But the pressure variations are transmitted by a rigid lower plate, or cover. This spring will allow to dampen the pressure variations, the device ensuringansi role "anti pulsations".

Between this plate 115 and the interior of the cavity is disposed a membrane 116, made of a flexible or flexible material, for example an elastomeric material. Preferably, this membrane extends over the entire surface of the cover 115, and even beyond the periphery of the latter, so as to bear against the periphery 113p of the lower plate 110. This periphery may comprise a joint port 113j against which the membrane 116 bears when the elements122 hold the two plates 110,120 assembled. Thus, this membrane 116 may form a seal to seal the device.

A reception volume 121 of the fluid is delimited by this membrane 116 and by the central surface 113c of the plate 110, this surface forming the bottom of the volumed'accueil.

In addition, an annular lip 126a is provided around the orifice 126. This annular lip has a certain height relative to the bottom 113c of volumed'accueil. Its upper part is flat, so that the membrane 116 will be able to bear against it, under the action of the spring 114. Furthermore, a stud 124a is located close to the orifice 124. This stud has a height equal to that the annular lip 126 relative to the bottom 113c. The membrane 116 will bear against the upper surface of this stud, under the action of the spring 114. But, this stud being located next to the orifice 124, the latter then remains open, which allows the introduction of a fluid in the inner volume, even when the membrane 116 bears against the upper surface of each of the elements 126a, 124a.

This configuration makes it possible to oppose to the fluid, which would return from the downstream part of the circuit by the element 128 (and which would thus circulate in the opposite direction of the direction of normal circulation of the fluid in the circuit), the presence of the membrane 116, which is supported against the element 126a with a pressure that depends on the characteristics duressort 114. This fluid must have enough pressure to lift theembrane 116, before being able to enter the interior volume of the device.

On the other hand, fluid flowing from the reservoir 11, 12 to the exhaust duct can enter through the orifice 124, without it being closed off by the membrane 116. This fluid, which thus comes under pressure in the interior volume 121 of the device, can repel the membrane 116 and compress the spring 114, which will thus absorb the pressure variations, then it will flow through the orifice 126, which is released by the action of the fluid pressure on the membrane 116. Therefore, this fluid first enters the interior of the device and can then lift the membrane 116 to release the outlet orifice and flow in the direction normal circulation of the fluid in the circuit.

The anti-pulsation device also designed comprises or contains means to enable it to function as a non-return valve, while damping the pressure fluctuations of the fluid that enters through the orifice 124. As already described above, several devices Anti-pulsation can be in series, or chained, to obtain a greater damping.

An exemplary embodiment of a pumping module, comprising the 2pompes 24, 26, will be detailed, in connection with FIGS. 8A-13.

Such a pumping module can be used in a device as described above. But it can be achieved independently of this device and used in other ink and solvent supply circuits of an inkjet printer.

As we have seen previously, the two pumps 24, 64 are highly reliable and operate continuously as soon as the machine is in a state of printing. It has been designed a maintenance module (or component) 270, 270a comprising a housing that contains essentially or only these 2 pumps and their hydraulic connections 23, 25, 60, 61. We know about the life of each of the pumps. As a result, a given lifetime can be assigned to the module tomorrow itself. Practically, a user of the printer will be able to exchange the maintenance module, for example as a preventive measure, at each period corresponding to the standard life of the module.

This module 270, 270a is shown and described here as comprising a substantially parallelepipedal housing. But it can also be a plate, such as the plate 273, 273a to which the pressure pump 24 and the recovery pump 64 sontreliés, without other side walls. In another variant, the plate 273, 273a is associated with flexible walls, the assembly being thus closed, only the plate 273, 273a is solids. The realization with a closed housing is advantageous because the housing plays a role of mechanical protection of the components it contains. It is this embodiment which is described below, but the other embodiments are easily deduced, especially since the plate 273, 273a remains substantially the same for each of them.This plate 273, 273a can be removable by relation to the case; FIGS. 11A and 13 show lateral elements of this plate, in the form of tabs 301i, 3012, for detachably fixing the plate 273, 273a against the housing, which comprises corresponding elements, here notches 302i, 3022, to accommodate said lateral elements, for example by clipping. A similar embodiment can be implemented for the housing of Figure 8A. As can be seen in FIGS. 11A, 11B and 13, the housing and the plate may comprise lateral enlargements comprising these means for fixing (lateral elements of the plate, in the form of tabs and corresponding elements of the housing, here notches). FIGS. 8A-11B show a direct orthogonal reference OXYZ, the plate 273, 273a and / or its upper surface extending in the XY plane.

The maintenance module has a compact connection interface with the rest of the ink circuit. This interface is provided with inlet and outlet ports 2711-2714 which allow the inputs and outputs of the two pump elements collected in the module to be connected to the inputs and outputs of the rest of the ink circuit.

This interface is advantageously made in at least one element or part 275, 275a which is in elevation or projecting with respect to the plate 273, 273a and / or at its upper surface.

This element or part 275, 275a may be removable relative to the plate 273, 273a; FIGS. 8B-8C and 11B, 12B, 12C show openings 291 -2913 making it possible to removably fix the corresponding element 275, 275a against the plate 273, 273a, for example using elements or means 2911-2913 forassembling, for example by screwing, the element or part 275, 275a with the housing. It is therefore possible first to fix the element 275, 275a against the plate 273, 273a, and then to assemble it with the rest of the housing. The element 275, 275a then comprises a connecting face 275i, 275ai connected to the housing, provided with means 2611-2614 of hydraulic connections to the conduits 23, 25, 60, 61, as illustrated in FIGS. 8C and 12C.

In order to allow an easy connection of the module to the rest of the device, the inlet and outlet ports 2711-2714 are arranged in a plane parallel to the plane YZ and perpendicular to the extension plane XY of the plate 273, 273a and / or at least a portion of its upper surface and / or plane or face 275i, 275ai of connection to the housing. This is illustrated more precisely in FIGS. 8B and 11A on which the positioning and the orientation of the inlet orifice 271i are shown in a detailed manner: this orifice extends in a substantially circular manner, perpendicular to the plane of the Figure 8B or the XY plane, and is located in the YZ plane or in a plane (Pl) parallel to the YZ plane, itself perpendicular to the upper surface of the plate 273,273a.

In the embodiments illustrated in FIGS. 8A and 8B or 11A-13, the holding element 275, 275a is in the form of a crossbar or a beam (FIGS. 8A and 8B), or a bracket (FIGS. 11A-13 ) and is in elevation or projection with respect to said surface 273, 273a. It is provided with inlets and outlets 2711-2714. 8A and 11A, these inlets and outlets, which make it possible to connect the 2 pumping elements collected in the module to the rest of the ink circuit, are seen: the input 271i for the input into the pump 24, the output 2712 for the output of the pump 24, the inlet 2713 for the fluid inlet into the pump 64, the outlet 2714 for the fluid outlet of the pump 64, in the direction of reservoir 11.

The fluid entering or exiting through each of these inputs or outputs flows through said inlet or outlet substantially parallel to plate 273 or 273a. The flow direction of the fluid, at the inlet of the orifice 271i, in FIGS. 8B and 12D, is represented by an arrow. This is a fluid inlet, in the direction of pump 24.

Finally, the module 270, 270a also contains the fluid connection means between each of the elements it contains (the pressure pump 24 and the recovery pump 26) and the input and the output 2711-2714 associated with this element. These fluidic connection means correspond to the ducts 23, 25, 60, 61 of FIGS. 3A-4A. The element 275, 275a is provided with conduits 27 21-27 24 which connect the leads 23, 25, 60, 61 to the inputs and outputs 2711-2714., Possibly via the connections 2611-2614. These conduits may be bent to join the corresponding conduit (see conduit 23 of Figure 8B) and the inlet or outlet port disposed and oriented as explained above. By way of example, FIGS. 8B and 12D show the duct 272i, which connects the duct 23 to the inlet orifice 271i. In the embodiment illustrated in FIGS. 8A-9, these ducts pass through element 275; in the embodiment illustrated in Figures 11A-13, these conduits are projecting from the square. The element 275, 275a has, in the embodiments illustrated in FIGS. 8A-9 and 11A-13, a substantially longitudinal direction OY, itself substantially perpendicular to the direction OX of alignment of the two pumps 24, 64. The inputs and outputs 2711- 2714 are arranged aligned along a surface 275 ', 275'a which is, itself, substantially perpendicular to the plate 273, 273a or on its surface. Thus, the fluid entering or exiting through each of these inlets or outlets flows, through said inlet or outlet, substantially parallel to this plate 273 and mannerally perpendicular to said surface 275 '., 275'a.

In the case of FIGS. 8A-9, the element 275 may comprise a longitudinal groove 279, in which the inputs and outputs 2711-2714, which have the direction and the orientation indicated above, will be arranged, but will also allow a displacement in translation (according to the double arrow of FIG. 9), substantially parallel to the plate 273, of the assembly of the module, facilitating the installation and dismantling of the latter.

More specifically, in this embodiment of FIGS. 8A-9, this element may comprise, in section perpendicular to this direction of longitudinal extension, a recessed portion, in "U", the inlet and outlet ports 2711-2714 being disposed along of the surface 275 'which forms the bottom of the "U" and which is delimited, on both sides, by 2 lateral surfaces 279i - 2792. Between the ends of these two lateral surfaces opposite the surface 275' an opening 280 will allow to accommodate a connection element 285 (for connection with the other elements of the ink circuit), complementary to the element 275. The 2 lateral surfaces 279i-2792 will allow to guide, in translation, one with respect to the other, the element 275 and the connection element 285. This opening is in a plane (P2) parallel to the plane YZ.

In this embodiment of FIGS. 8A-10, the section, in a plane XZ, of the element 275 thus has the shape of a tab, or a claw, which will make it possible to ensure both the fluidic connections and the link Mechanical Module 270.

In the case of FIGS. 11A-13, the element 275a, in the shape of a square, has two surfaces 275b, 275ai at 90 ° to each other, the connecting face of which is provided with inlet and outlet openings 2711 -2714, and the face intended to be pressed against the plate 273a.

An embodiment of the connecting element 285, adapted to the embodiment of FIGS. 8A-8B, is shown in FIG. 10. This interface is advantageously made in an element or part, for example in the form of a cross member or a backing, which extends according to the Y direction and is in elevation or projection with respect to a surface 283 (which extends along the YZ plane). This connecting element 285 is intended to be inserted in the volume defined by the "U" of the element 275. On an upper surface of this element 285 are disposed orifices 2811-2814, each of them being intended to be aligned and contact with one of the holes 2711-2714. The element 285 is traversed by conduits 2821-2824 which fluidly communicate the orifices 2811-2814, and thus the conduits 23, 25, 60, 61, with the rest of the circuit.

In the embodiment illustrated in FIGS. 11A-13, connection elements 2811-2814 and 2871-2872 corresponding to the elements 2711-2714 and 2771-2772are arranged on the surface 283, each of them being intended to be aligned and encontacted with the one of the orifices 2711-2714, ΤΙΊγ-ΤΙΊτ.

The elements of the remainder of a circuit such as that of FIG. 3C, which are contained in the housing 270 mainly comprise the anti-vibration device 26, and the tanks 11, 12, as well as the means 21, 26, 30, 42, 44 ( already described above) are visible in FIG. 9; in this figure, the means 12 and 22 are hidden by the means 11, 21.

Means for fixing the element 275, 275a against an element 285 of the plate 283 (FIGS. 9, 10) or against the plate 283 can be provided for fixing the assembly in a simple manner, for example by screwing; for this purpose, the plate 275, 275 can be provided with holes 277i-2772 in which screws or dowels or trivets can be inserted and then introduced into corresponding members, for example in holes, which can be threaded or tapped, made in the rest of the device, in particular in holes 287i - 2872 of the element 285 or 283 (FIG. 13). Other fastening means may be used, for example by lateral claws, the element 275, 275a being then be provided with elements, for example pins, misfeeding or centering, to assemble with the element 285 or 283.

Electrical connection wires (not shown in the figures), in order to bring the supply voltages of the pumps 24, 64 (pressure pump, recovery pump) can leave the housing 270, 270 a in order to be connected, when the module is mounted to printer power means. These son can for example be connected to a connector (not shown in the figures) of the printer.

A module such as the module 270, 270a described above can be replaced in a simple and fast manner, after having removed the fixing means (screw or other means) against the element 283 and / or 285. In the configurations illustrated in FIGS. 9 and 13, the module 270, 270a is then raised, and a new module can be positioned by applying its connection element 275, 275a against the element 285 or the surface 283 and then fixing the two elements with each other .

As understood here, it is possible to avoid, between the maintenance module 270, 270a and the other components of the ink circuit, the use of shut-off connections, or self-sealing, which are expensive.

Each of the inputs / outputs 2711-2714 and 2811-2814, may comprise an end of a conduit, itself provided with a seal. For example, each of the inputs / outputs is provided with an O-ring which bears, in operating position, against a concentric seal surface, of the corresponding input / output 2811-2814 of the fixed part 283-285. One of these litters 311i is shown in FIG. 12D. The inputs and outputs of the fixed portion 283-285 have the same type of configuration as the inputs and outputs of the module 270, 270a with deconducting ends, each of which has a concentric seal range. The invention may be implemented in a printer such as that described above in conjunction with FIG. 1. This comprises in particular a print head 1, generally offset relative to the body of the printer, and connected thereto. by means, for example in the form of a flexible umbilicus 2, gathering the hydraulic and electrical connections for the operation of the head.

Controller means or control means have been mentioned above.

These means comprise for example a microcomputer or a microprocessor and / or an electronic or electrical circuit, preferably programmable, that can transmit the printing instructions to the head but also control the pumps 24, 64 or the motors and / or the valves 21, 22, 52, 54 of the system for managing the feed of the ink and / or solvent circuit and the recovery of the ink and solvent mixture from the head.

They can also collect the level information provided by the level measuring means 13, 15, 15a in the tanks 11, 12, 12a and possibly trigger the corresponding alarms. They can also collect the pressure information provided by the sensor 36 and, optionally, adapt the sending of solvent, for example in quantities and a predetermined frequency or calculated as explained above, in order to adapt the viscosity of the ink in the circuit.

The means 3 are programmed according to the functions that must be managed in the printer. These controller means, or these control means, are arranged in the part 5 'of the system or the desk.

Claims (3)

A device for supplying ink and solvent to the printing head (50) of an inkjet printer, comprising: - at least a first reservoir (11) and a second reservoir (12), different from first, means (60, 61, 64) for collecting in the first reservoir (11) a stream of recovery ink from a gutter of the printing head, the first reservoir having a first outlet (11i), for sending ink from this first reservoir to the printhead, the second reservoir having a second liquid outlet (112) for sending solvent from the second reservoir to the printhead; means (21, 22, 23) for selectively connecting the first output and / or the second output to a common ink and / or solvent pressurizing pump (24) for sending to the print head (50); and, downstream of the common pump (24): a first feed path (32) of the ink and / or solvent printing head, this first path possibly comprising a damping device (26b); a second supply path (34), parallel to the first power supply, for supplying the print head with solvent. 2. Device according to claim 1, further comprising at least a damping device (26, 26a, 26b) for damping fluctuations or uncompressed pressure of ink and / or solvent from the common pump (24). 3. Device according to claim 2, at least one damping device comprising means (28,16,126a), forming a non-return valve, to prevent a flow of ink and / or solvent to the common pump (24). 4. Device according to one of claims 1 to 3, further comprising a third reservoir (12a) provided with a third output (12ai), the deselecting means for selectively connecting the first output and / or the second outputet and / or the third output to said common pump (24). 5. Device according to one of claims 1 to 4, further comprising a pressure sensor (36) for measuring a pressure of ink and / or solvent sent to the print head. 6. Device according to the preceding claim, furthermore comprising means (3) for, with the aid of the selection means, adding at least a quantity of the solvent, as a function of at least one pressure or pressure variation value measured by said sensor (36). 7. Device according to the preceding claim, said amount of solvent taking into account the dilution of the ink with the solvent. 8. Device according to claim 6 or 7, said means for adding a plurality of amounts of solvent, alternated with ink, to allow a mixture of solvent and ink. 9. Device according to one of claims 6 to 8, further comprising means (3) for calculating a number and / or frequency of sending (s) an elementary quantity of solvent to the common pump (24) and for send this quantity of solvent, possibly at the calculated frequency, alternately with ink shipments to the pump. 10. Device according to one of claims 1 to 9, further comprising means (71 - 74, 76, 78) for imposing an operating pressure to the common pump (24). 11. Device according to one of the preceding claims, comprisingat least one duct (71, 72, 74) back, from at least one supply duct (32, 34) of the print head to one of the two reservoirs (11, 12), said return duct being disposed from a point downstream of the common pump (24) and having means forming a restriction (73, 76, 78) of the flow in said return duct. 12. Device according to one of claims 1 to 11, comprising 2conduits (71, 72, 74) back to one of the two tanks (11,12), each being associated with a supply path (32, 34) of the print head and being disposed from a point downstream of the common pump (24) and including unerestriction means (73,76,78) of the flow in this return conduit. 13. Device according to claim 11 or 12, furthermore comprising means (3) for detecting a blockage of said restriction. 14. Device according to one of claims 1 to 13, further comprising means (3) for adjusting the speed of the common pump (24) as a function of a given pressure value. 15. Device according to the preceding claim wherein the means (3) for adjusting the speed of the common pump (24) proceed by dichotomy. 16. Device according to one of the preceding claims, furthermore comprising means (3) for performing an air purge possibly present in the power supply device. 17. A method for supplying ink and solvent to the printing head (50) of an ink jet printer, comprising: - the drawing of ink, or solvent, respectively, from at least a first reservoir (11), containing ink, respectively a second tank (12), different from the first and containing solvent, using a pump (24) communeaux two tanks, pressurizing the ink and / or solvent, a stream of recovered ink from a gutter of the printhead being sent to the first reservoir (11), - the sending of ink and / or solvent to the head d printing (50) with the aid of said pump (24) common to both tanks; - and the selection, downstream of the common pump: * is a first supply path (32) of the print head, for sending, to it, ink and / or solvent, * or a second supply path (34), parallel to the first feed path, for supplying the print head with solvent. 18. Method according to the preceding claim, wherein an ink flow and / or solvent is sent at the output of said common pump (24) to at least one means (26) for damping ink pressure fluctuations and / or of solvent. 19. Method according to one of claims 17 or 18, wherein is measured a pressure of ink and / or solvent sent to the print head. 20. Method according to the preceding claim, wherein is sent to the print head at least a quantity of solvent, depending on a pressure value or a measured pressure variation. 21. Method according to the preceding claim, said amount of solvent taking into account the dilution of the ink by the solvent. 22. The method of claim 20 or 21, wherein a plurality of amounts of solvent, alternated with ink, are sent to the print head to allow mixing of the solvent and the ink. 23. Method according to one of claims 20 to 22, whereincalcule a number and / or a frequency of sending (s) an elementary amount of solvent to the common pump (24) and sends this amount of solvent, optionally at the calculated frequency, alternately with ink shipments to the common pump. 24. The method as claimed in the preceding claim, in which the elemental amount of solvent added to the volume of the ink circuit for mixing it into a head produces a relative viscosity variation of less than 1%. 25. Method according to one of claims 17 to 24, wherein the speed of the common pump (24) is adjusted according to a given pressure value. I