FR3048199A1 - 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 area of a membrane pump as a function of temperature.

Continuous Inkjet (CIJ) printers are well known in the field of coding and industrial marking of various products, for example to mark 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 some areas of decoration where the graphic printing capabilities of the technology are exploited.

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

First, a print head 1, generally remote from the body of the printer 3, is connected thereto by a flexible umbilical 2 gathering the hydraulic and electrical connections necessary for the operation of the head by giving it flexibility that facilitates integration on the production line.

The body of the printer 3 (also called 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 the ink to the head at a stable pressure and of adequate quality, and secondly to support ink jets not used for printing, - a controller 5 located in the top of the desk (zone 5 '), capable of managing the sequencing of actions and of performing the processes enabling the activation of the various functions of the ink circuit and the head. - An interface 6 which gives the operator the means to implement the printer 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 providing the ink, of nominal quality, under pressure to the head and the vacuum recovery of ink not used by the head.

Figure 2 schematically shows a print 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 a periodic stimulation system (not shown) located upstream of the outlet of the nozzle. When the drops 7 are not intended for printing, they go to a gutter 62 which recovers them to recycle the unused ink through the ink circuit 4. Devices 61 placed along the jet (electrodes loads and deflection) allow, on command, to electrically charge the drops and deflect them in an electric field Ed. These are then deviated from their natural ejection path of the drop generator. The drops 9 intended for printing escape the gutter and will be deposited on the print medium 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 drop of a jet can be oriented only to 2 paths: printing or recovery. In multi-deflected continuous jet printers, each drop of a single jet (or a few spaced jets) can be deflected on different paths corresponding to different charge commands from one drop to another, thus performing a scan of 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 displacement of the print head and the print medium 8. Generally the elements are arranged in such that these two directions are substantially perpendicular.

An ink circuit of a continuous inkjet printer first makes it possible to supply ink under controlled pressure, and possibly solvent, to the drop generator of the head 1 and to create a depression to recover the unused fluids for back printing of the head.

It also allows the management of consumables (dispensing of ink and solvent 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 support of certain maintenance operations to ensure the same operation regardless of the conditions of use. These functions include solvent rinsing of the head (drop generator, nozzle, gutter), assistance with preventive maintenance such as the replacement of components with limited lifespan (filters, pumps).

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

Some current printers are designed in a modular way to make the maintenance of the machine easier, thanks to the quick exchange and without special tools of certain modules. These can be more or less complex functional sub-assemblies of which one or more elements are components with a limited lifetime (eg wear components) or components whose performances degrade with the time of use ( eg 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 flow fluids during module replacement, and various other components that would not be needed if the module concept was not present.

An example of a modular device is given in Figure 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) to isolate the modules (50 and 60) of the body of the ink circuit at the time of disconnection and thus avoid fluid flows.

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

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 the fluids.

More generally, to provide the user with an increasingly high level of user comfort, more and more sophisticated performances making it possible to address applications that are 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 perform, 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 purging from the head, or the transfer of 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 high performance, high capacity pumps are very well suited 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 remains 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 the least possible components, especially for functions such as the management of consumables and / or the control and maintenance of the quality of the ink and / or solvent rinse of the head.

In particular, a problem is to reduce the number of hydraulic components and to simplify the interconnection of these components. Despite this, user satisfaction must be ensured so that the effort on this reduction in 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 sequencing can be very complex.

There is therefore a need for a printer adapted to handling by low training operators.

In another aspect, the ink circuit comprises a large number of hydraulic, hydroelectric, sensor, etc. components. Indeed, modern printers have many functions more and more sophisticated and precise. 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 that minimizes the number of components while ensuring a good level of performance and reliability as well as an easy maintenance allowing rapid interventions, minimizing the risk of contamination and achievable by operators without 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. Such an architecture 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 feeding 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 from this first tank to the print head, the second tank having a second liquid outlet, for sending a second liquid from this second tank to the print head, - selection means for selectively connecting the first output and / or the second output to a common pump for pressurizing the ink and / or the solvent for sending to the print head.

This type of circuit makes it possible to use only one pump, for pumping the two liquids, on the one hand the ink and, on the other hand, the solvent. The means for selectively connecting the first output and / or the second output to a common pressurizing pump comprise, for example, a valve associated with each reservoir and activated on opening or closing, to flow or send the selected liquid to the common pump. .

At least one damping device, common to the ink circuit and the solvent circuit, can be provided for damping fluctuations or ripples of ink pressure and / or solvent from the single pump. Preferably, such a damping device comprises means forming a non-return valve, to prevent ink circulation and / or solvent to the common pump.

Such a device or supply circuit may comprise at least a third reservoir, provided with a third output, the selection means for selectively connecting 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 a pressure of ink and / or solvent fed to the print head.

Means may also be provided for, by means of the selection means, adjusting the viscosity of the ink, as a function of the pressure measurements. For example, means may be provided for adding at least a quantity of solvent, depending on 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 amounts of solvent, alternated with ink, to allow a mixture of the solvent and the ink.

To adjust the additions of solvent, the device may further comprise means for calculating a number and / or frequency of sending (s) an elementary 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, alternately with ink shipments to the pump. Thus, a quantity of solvent is sent gradually, 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, downstream of the pump: a first supply path of the printing head in ink and / or in a solvent, this first channel possibly comprising a damping device, second feed path, parallel to the first feed path, for supplying the print head with solvent.

By "downstream" is meant "in the flow direction of the fluid", tanks 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 may be reserved exclusively for the circulation of solvent and will be used during cleaning operations of the circuit with the solvent.

In addition, means can be provided for imposing an operating pressure on the common pump, for example having at least one return duct, towards one of the two tanks, since at least one supply duct for the print head. , this return duct being disposed from a point downstream of the common pump, and possibly the device for damping variations or pressure ripples, and comprising means forming a restriction of its flow. When the device comprises two feed channels, such a return duct, provided with means forming a restriction, can be provided for each of the two channels.

Means may be provided for detecting a blockage of said restriction.

Means may be provided for adjusting the speed of the pump according to a given pressure value, for example these means may proceed by dichotomy to adjust the speed of the pump

Finally means may be provided to achieve an air purge may be present in the supply device. The invention also relates to a method for supplying ink and solvent to the print head of an inkjet printer, comprising the implementation of a device or a circuit as described hereinabove. above. The invention also relates to a method for supplying ink and solvent to the printhead of an inkjet 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 pump for pressurizing the ink and / or the solvent, a flow of recovery ink from a gutter of the print head being sent to the first reservoir having a first liquid outlet, - sending ink and / or solvent to the print head using of the common pump.

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

A flow of ink and / or solvent may be sent, at the output 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 by the solvent.

A plurality of amounts of solvent, alternating with ink, may be sent to the print head to allow mixing of the solvent and the ink. Thus, a quantity of solvent can be sent progressively, in small elemental amounts, which allows mixing with the ink sent between the elementary amounts of solvent. For this purpose, it is possible to calculate a number and / or a frequency of sending (s) an elementary quantity of solvent to the pump and to send this quantity 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.

In order to ensure optimum circulation of the ink and / or the solvent, downstream of the pump is selected: - a first feed path of the print head, for sending it to the latter, ink and / or solvent, or a second feed path, parallel to the first feed path, for supplying the print 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 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 detachable one-piece assembly for an ink circuit of a continuous ink jet printer, comprising at least one plate, of substantially planar shape and extending in a plane (XY) as well as a first pump, said pressure pump, and a second pump, said recovery pump, fluidic connection means, for producing a fluid flow between, on the one hand, a first fluid inlet, the first pump and a first fluid outlet, and, secondly, between a second fluid inlet, the second pump and a second fluid outlet, - at least one connecting element, which is fixed to, for example by overhanging, said plate and which comprises a so-called connection surface in which said inlets and outlets open, this connecting surface being substantially perpendicular to the plate, and the axis of flow of a fluid through said inlets and outlets being parallel 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 the present application, or 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 diaphragm 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 connecting element comprises a groove having a "U" profile, said inlets and outlets opening into a surface which delimits 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 bearing surface 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 relative to 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 connection element can be removable relative to said plate. According to one embodiment, it comprises fastening elements against said plate.

Means may be provided to secure the assembly to the ink circuit. The invention also relates to a device for damping the pulsations or pressure variations of an ink in the ink circuit of a continuous ink jet printer, this device being for example suitable for use in, or in combination with with, the device or the supply circuit described above or in the present application, or with other circuits in which a damping device is provided.

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

According to a particular embodiment, the nonreturn valve means comprise a membrane which closes said outlet under the action of the 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 against which said membrane comes into contact. support under the 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 can be transmitted, via the membrane, 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 a CIJ type printer; FIGS. 3A-3E represent exemplary embodiments. FIG. of a supply circuit according to the invention, - Figures 4A - 4D represent variants or other embodiments of power supply circuits according to the invention, - Figures 5A and 5B show evolution curves of the pressure of the ink as a function of the temperature, - Figure 6 shows schematically the alternation of addition of solvent, in elementary quantity, and addition of ink, - Figure 7 shows a damping device of pressure variations according to the invention, - Figures 8A-8C and 9 show aspects of embodiment of a component or removable module according to the invention, - Figure 10 shows a removable component according to the invention, mounted in a device 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 solvent, for example MEK (methyl ethyl ketone) type. 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 an 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 of the tanks 11, 12 can be filled, by means of a fluid circuit or, more simply, by hand, by pouring into the reservoir, the corresponding liquid, when the this is missing. Means 13, 15 may be provided in each of these tanks to measure 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 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 reservoir corresponding, depending on the pressure conditions and flow output of these valves.

Each of these two outlets brings the sampled liquid to a single pump 24, common to the two liquids, which will therefore be able to pump, for example successively or alternatively, or simultaneously, depending on the open or closed state of the valves 21 , 22, the ink from the tank 11 and the solvent from the tank 12. A single conduit 23, downstream of the valves, can therefore 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 having been mixed with ink, or by being mixed with ink which has itself been extracted from the tank 12.

According to a particular embodiment, a conduit 21i (respectively 22i) connects the outlet of the tank 11 (respectively 12) to the inlet of the valve 21 (respectively 22) and a conduit 212 (respectively 222) connects the outlet of the latter to the duct inlet 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 used to pump the ink is constantly requested during the printing phases. On the other hand, the pump that 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 perform rinsing or cleaning operations of all or part of the circuit). In the circuit illustrated in the context of the present invention, the single pump 24, common to both 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 say almost constantly during the printing phases. Therefore, although being used to pump 2 liquids, it is not more solicited than the pump dedicated exclusively to the pumping of the ink in the known systems.

A single conduit 25, at the outlet of the pump 24, then makes it possible to send the pumped liquid towards the printing head, preferably via means 26 of damping, or damper or "anti-pulse", which , advantageously arranged at the pump outlet 24, allow damping fluctuations or liquid pressure ripples caused by the operation of the pump 24 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 flow of liquid can vary around a mean value, which can be between 2 and 6 bars and around from which the fluctuations can be +/- 1 bar. This ripple can be significant and not very compatible with the operation of an ICJ printer. Indeed, the drops loading system is synchronized to a phase of the stimulation signal calibrated with respect to the moment when the drop separates from the jet. Now, this moment is defined for a given jet speed; a variation in jet velocity, induced by pressure ripples still perceptible, periodically desynchronize the load with respect to the moment of separation of the drops, which would disrupt their trajectories and therefore 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 damper means 26 may be arranged in series, or, according to a more complex architecture illustrated in FIG. 3D, on different sections of the supply 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 non-return 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 to the means 26, the common line 25 and to the pump 24. In the event of stopping the printing machine, ink, which would be returned to the means 26 and / or to the pump 24 and which would remain in these organs throughout the duration of the stop, could affect the functions of the latter, (by gluing and / or plugging the pump or means 26) in particular in the case of the use of a pigment ink, the pigments tend to be deposited there.

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 in the path of the fluid, downstream of the means 26, 28. Optionally, a pressure sensor 36 makes it possible to detect the pressure variations 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 as well). This measurement of the pressure will make it possible to detect, indirectly, the solvent concentration variations 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 with 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 carried out at regular intervals, for example between 5 and 10 minutes depending on the operating phases of the machine: this interval can be different depending on whether the printing machine is in the starting phase, or is in steady state printing. 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 measurement of pressure.

The sensor 36 is preferably disposed in the head 50, but, for reasons of space, may 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, using a pump 64, through one or more ducts 58, 60, 61 and, optionally, a valve 54. A filter 59 may be disposed on this return path, since the fluid will be returned to the ink tank 11, 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 print head 50.

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

As will be described later, all of the two pumps 24, 64 can be combined in a module 270, 270a (for example as described later and in FIGS. 8A to 13) which can be detached from the rest of the circuit, thus allowing a change of all the 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 the flow rate for different powers supplied to the engine, an example of these curves is given in Figure 4 of the aforementioned 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 a zero flow to a 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, in particular in the case of a diaphragm pump. These means may comprise a path, or a return line 71. Via this conduit, a part of the fluid circulating in line 29 is withdrawn and this fluid is returned to the reservoir 11. This return path is provided with a restriction 73, which locally reduces the section of the conduit in which the liquid circulates and which makes it possible to pressurize the fluid sent to the head. Advantageously, this restriction is a singular restriction, that is to say a point or localized narrowing of a fluidic duct whose length is substantially smaller than its diameter, or small in front of its diameter, and which creates a pressure drop. insensitive to the viscosity of the fluid passing through it. A singular restriction is a localized narrowing of a fluid 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 1 / ί (for example D = 0.3 mm and L = 0.1 mm). It is possible to implement a restriction, having a singular behavior, for which L / D is greater than 1 and can reach 10 (in other words, 1 <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 its viscosity. Here, the restriction 73 comprises an orifice of diameter for example 0.3 mm.

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

Means 3, for example comprising a processor or a microprocessor or a computer and / or an electrical or electronic circuit, for example of 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 of the valves 21, 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 to process data from the level sensors 13, 15 and the 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 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 parts of the fluid circuit in which the 2 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 again here. In this embodiment, means 30, for example a valve, preferably electromagnetic, 3-way, arranged downstream of the means 28, can be selected: - 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 32 supplying the print head, - or a supply of the head 50 with the only second liquid, via a second channel 34 supplying the print head; it is thus possible to send to the printing head clean solvent, not containing, or little, traces of ink.

The means 30 can be activated (using 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, by means of which variations in the pressure of the liquid which feeds the head can be detected. As indicated above, it would, preferably, be arranged in the head 50 but, for reasons of space, it can be positioned on the supply line 32. The functions of this sensor are the same as those which have been described above in connection with Figure 3A.

Each of the two channels may be provided with means for filtering the liquid it conveys: thus the channel 32 may be provided with filtering means 31, 42 and the channel 34 with filtering means 44.

The print head may be provided with valves 46, 48 to allow it to be fed, 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 it 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 or filters) described above.

In this embodiment, the means 28 make it possible to prevent the introduction of ink into the part of the circuit common to the two fluids (the means 26, the common line 25 and the pump 24). Thus, during a cleaning or rinsing phase, the solvent pumped upstream of the non-return valve 28 will be preserved from any ink return and may be sent to line 34 without being polluted by water. ink.

Another embodiment is illustrated in Figure 3C, which includes all the elements described in connection with the previous figure, which will not be described here.

In addition, a channel, or a return duct 72, 74 may be provided for each of the channels 32, 34. Via this duct, a portion of the liquid that circulates is taken, respectively in the channels 32, 34. and this liquid is returned to the corresponding reservoir 11, 12. 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, 78 comprises an orifice, for example of diameter 0.3 mm.

These return channels 72, 74 provide part of the safety of the system: if there is an increase in pressure, for example because of a risk of clogging in the head 50, then the fluid that can no longer 'flow through the head is channeled through the return path 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 makes it possible to detect this anomaly, or it is evidenced by a reduction in the speed of the motor. 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 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 printing. 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 includes a part of the feed channels 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: FIG. 3 shows two damping devices 26a, 26b in series on FIG. portion of the supply circuit which is common to the ink and solvent, upstream of the valve 28 and means 30, - in Figure 3E, there are two damping devices 26a, 26b, but one arranged as in 3C, 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 only 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 in upstream of the valve 28, or one may be upstream of the 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 provides the ink head and / or the necessary solvent to the print head. 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 having been mixed with ink, or by being mixed with ink which has itself been extracted from the tank 12, the mixture then being made in the elements of the circuit fluidic common to both liquids, namely the conduits 23, 25, the pump 24, the device 26 damping. The described device comprises only 2 pumps and 2 tanks, without additional reservoir 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 with reference to FIGS. 3A and 3B. In this variant, an additional reservoir 12a is provided, comprising 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 alternately or simultaneously, depending on the opening state of the different valves, liquids from one or more of the tanks 11 12, 12a. The single conduit 23, downstream of the various valves, allows to bring to the pump 24 the liquid or liquids from one or more of the tanks.

Means 15a for measuring the level of liquid in the third tank may be provided. Examples of such means are given in WO 2011/076810.

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 above, 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 reservoirs are pressurized, for example by means of one or more air compressor (s) 24a, which makes it possible not to use a pump 24 or any other means The variant illustrated in FIG. 4B relates to the structure of FIG. 3B, but the use of compressor (s), replacing the means 24, 26, can also relate to the structures described with reference to FIGS. 3A. or 4A.

The mixture of the two liquids is then made in the part of the fluidic circuit which is common to them, namely the conduit 25. The device has only one pump, the pump 64, which makes it possible to bring back unused ink for printing to the tank 11.

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

This time, the two tanks 11, 12 are pressurized, for example with an air compressor, and are connected to a supply duct 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 may be located very downstream with respect to the reservoir 11 and the valve 21.

As a variant of this FIG. 4C, illustrated in FIG. 4D, the reservoir 12 is connected 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 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 geometric characteristics of the nozzle of the print head and the ink circuit of the printer, and for a speed given Vjet jet (for example 20 m / s), the evolution of the pressure (for example at the nozzle outlet) as a function of the 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) making to intervene the viscosity of the ink, - singular pressure losses (term 3) involving the density of the ink.

We can therefore write that the pressure, at the nozzle, during the formation of the drops, results from the sum of the 3 terms above: (1)

With: - p (T) = density of the ink, expressed in kg / m3, - μ (T) = viscosity of the ink, expressed in Pa.s, - Uuse = 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 the calibration; he is without units.

Note that, if the pressure considered was not that to the nozzle, but at a point located at a distance from it, for example upstream of the umbilical 19, as in the case of the sensor 36 of Figures 3A - 4D , a similar formula would be obtained, adding to the formula above a pressure term corresponding to the difference in level between the desk 3 and the print head 1. This term of added pressure can be a parameter stored in the printing machine , which an operator selects when evaluating the elevation gain. 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, a calibration is preferably carried out in order to overcome the geometric and / or variable mechanical tolerances of one ink circuit to another, of the same structure. ; or, over time, following a change 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 can have already been calibrated, may be desirable.

This calibration makes it possible to carry out a correction, which consists of repositioning the reference curve C by shifting it by a difference in pressure, equal to the difference between this curve C and a real working point under reference conditions (nominal speed of the jet, defined during sizing of the print head (in particular when sizing the stimulation) and taking into account the characteristics of the ink), for which the curve C is given, and in particular a concentration, or a viscosity, given. The actual 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 nominal jet velocity, for which the curve This 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 ink quality.

The jet speed can be kept constant, at the nominal 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 Figures 4B-4D. The pump may be part of servo means, comprising a sensor for measuring the speed of jet in the head, for example a sensor as described in application PCT / EP2010 / 060942.

Thus, FIG. 5A shows a measuring point (Pm, T) which 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 therefore 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 the curve C, it is positive 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.

Furthermore, it can be seen that, according to formula (1) above, the viscosity μ of the ink is first-order, in the second term. The formula, valid for a given viscosity (called nominal or theoretical), will therefore be all the less valid that the actual viscosity of the ink used is different from the nominal viscosity. However, differences in viscosity can 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 that, 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 in repositioning the curve C (or C ') by shifting it by a difference in pressure, proportional to the difference between the viscosity actually used (visco_prod) and the 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 translating the initial curve C by a value equal to this pressure difference.

We can therefore perform a calibration that takes into account the actual 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 above teaching for a given ink and for a predetermined jet speed value (for example 20m / s) take into account 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 into account the variations of the geometrical and / or mechanical parameters of the circuit used.

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

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 pressure proportional to visconominal (cP) - visco_prod (cP).

The control means 3, already presented above, can store data relating to the curve C (for example a set of pairs of values (P, T) associated with a nominal jet speed) and / or data. resulting 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 may be to check the validity of the stored 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 actual ink used, then an alarm can be triggered to allow the alarm to occur. correction.

A calibration as described above may be followed by printing by the printer, the inkjet being formed at a reference speed, or nominal, the pressure of the ink being able to be servocontrolled to reach the pressure which results, preferably, from the 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 temperature. It can be one of the curves C 'or C "mentioned above. The lines of acceptable fluctuations of the pressure, for example + 225 mbar, have been represented in broken lines on either side 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 can 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 such 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 that given by the reference curve Cref is due to a difference in viscosity (or concentration), according to the following relation: (2)

When the pressure is no longer that of the nozzle, but at another point of the circuit, one can take into account additional viscous terms (which result for example from the umbilicus, ...) but these terms are negligible in front of the pressure difference at 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 jet line, the additional pressure losses are low and taken into account. in 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 continuously controlled, 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 speed of jet in the head, for example a sensor as described in PCT / EP2010 / 060942).

To ensure good ink quality, or consistent quality, a viscosity difference 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 taking into account the dilution coefficient, which is specific to each ink and can be formulated as follows: (3)

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: 4)

- 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 nominal jet speed 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, Hn and H12, are shown schematically in Figure 3C.

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

However, excessive pressure variations can also cause jet speed variations that are too great and therefore instability of the jet speed.

Solvent additions are made in small amounts to limit the pressure variation. In order not to disturb the jet, it is sought to limit the pressure variation to less than 1% of the reference pressure. Equation (2) makes it possible to translate this limit of variation of pressure into the limit of variation of viscosity. For example at 10% of the nominal viscosity. Equation (3) then makes it possible to translate it into a solvent volume ΔΝ / r that can be added in a volume Vr in which it will be mixed before sending to the print head.

For example, for: Cd = 2.6 then ΔΝ / r / 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 elementary 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 jet speed.

Given the flow rate of the pump, it deduces the opening time te of the valve 22 to obtain this amount. More precisely, the flow rate in the line connecting the reservoir 12 to the pipe 23 is determined, taking into account the flow rate between the reservoir 11 and the pipe 23, as well as the flow rate of the pump 24, the pressures in the pipes 2I2 and 222. being considered equal (because these two ducts are identical and both are connected to the same duct 23). They are calculated according to the heights Hn 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 print head).

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

Preferably, the calculation of this mixing time takes into account 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 solvent added (this is also the case in the other circuits presented, if they contain damping means 26). These pressure fluctuation damping means contain an internal volume which allows mixing of ink and a small amount of added solvent. 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 mixing the ink and the added solvent.

A plurality of elementary additions of solvent can thus be made to compensate for a variation of pressure detected in the circuit, in the form of successive pulses, for example periodic pulses of duration ts and of period te + ts., Which is represented in FIG. 6, where 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; Cd = 2.6. - A = 1, 63 and B = 3.74. - Vajout (refers to the total volume of added solvent) = 29 cm3; N cycles (denotes the number of solvent addition cycles) = 144; - Pref = 2.7 bar; -ΔΡ = 50 mbar.

In the case of the structures described above in connection with FIGS. 4B-4D, the explanations given above, concerning the link between pressure variations and viscosity variations, up to and including the formula ( 3), remain valid. A formula similar to the above formula (4) can therefore be established, on the basis of the flow rates which result from the action of the compressor (s) 24a, the amount of solvent to be added, preferably taking into account the effects of the dilution on the viscosity of the ink via the dilution coefficient. Again, excessive pressure variations can cause jet speed variations too great and therefore instability of the jet speed. In order not to disturb the latter (due to printing operations in progress), the additions are made in small quantities, or by adding 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 undergoes a variation less than a given limit value, for example + 1% of the speed of the jet. The inkjet, sent to a print medium, is thus undisturbed by the change in the quality of the ink and / or its pressure which result from the addition of solvent.

Given the flow rate resulting from the action of the means 24a, the opening time U of the valve 22 is deduced 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 imposed flow rate. by the means 24a, the pressures in the ducts 212 and 222 being considered equal (since these two 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 media, it is possible, for example with the help of the various devices which have been described above, to add very small quantities of solvent. (still called "micro additions"); each micro-addition has for example a volume less than a few cubic centimeters, or 1 cm3; or else, it is between 5 cm3, or 1 cm3 and 0.01 cm3 or 0.05 cm3. Such micro additions are made successively, with a time difference te which 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 startup phase, the print head 50 can be cleaned. For this purpose, solvent is sent to the head, the valves 22, 48 and 52 being open, and the pumps 24 and 64 (or the means 24a and the pump 64) being activated. The valve 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 blocking of the restriction 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 an operating 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 toggled to send ink to the printhead, by the supply path 32. Thus, ink will be able to be pressurized and be 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 remove air, valve 30 is switched to send ink to feed path 32. Pump 24 (or means 24a) is started, circulating ink through means 26, the valve 30, the filters 31, 42, possibly the restriction 76, and through the umbilicus 19. The air that would have possibly remained in these various elements is then driven out.

In yet another aspect, the speed of the pump is adjusted to reach the reference pressure given by the reference curve (FIG. 5B). Indeed, 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 motor) 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 26, which introduce a delay.

When the reference pressure is reached, an ink jet may 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 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 the machine, the line common to the ink and the 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 ink from 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 circuit. fluid flow, particularly for an ink jet printer, in which fluid pressure variations can occur. Such another circuit is for example described in WO 2014/154830.

This device 26 may have, in view from below or below, a substantially circular shape or that of a regular polygon. It comprises two 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 flat lateral portions are facing each other when the two plates are assembled using means 112,122.

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

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

A spring 114, in spiral, makes it possible to damp the pressure variations of the fluid when it is in the cavity. Other means may be used, in place of a spring, to perform 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 the inside of the cavity. But the pressure variations are transmitted to it by a rigid lower plate, or cover 115. This spring will allow to dampen the pressure variations, the device thus ensuring a 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 scope seal 113j against which the membrane 116 bears when the elements 122 hold the two plates 110,120 assembled. Thus, this membrane 116 can form a seal to seal the device.

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

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 the reception volume. 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 near the orifice 124. This stud has an equal height to that of 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 interior 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 pressed against the element 126a with a pressure that depends on the characteristics of the spring 114. This fluid must have enough pressure to lift the membrane 116, before being introduced into the interior volume of the device.

On the other hand, fluid flowing from the reservoir 11, 12 towards the downstream of the circuit can enter through the orifice 124, without it being blocked by the membrane 116. This fluid, which enters thus under pressure in the internal volume 121 of the device, will be able to push 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 from the fact of 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 anti-pulsation devices can be in series, or chained, in order to obtain greater damping.

An exemplary embodiment of a pumping module, comprising the two pumps 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 realized independently of this device and used in other ink and solvent supply circuits of an ink jet printer.

As we have seen previously, the two pumps 24, 64 are highly stressed and operate continuously as soon as the machine is in a state of printing. It has therefore been conceived a maintenance module (or component) 270, 270a comprising a housing which essentially or only contains these two pumps and their hydraulic connections 23, 25, 60, 61. The service life of each of these is known approximately. shoes. As a result, a given lifetime can be assigned to the maintenance module 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 are connected, 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 being solid. The embodiment 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, in particular because the plate 273, 273a remains substantially the same for each of them. This plate 273, 273a may be removable relative to the housing; FIGS. 11A and 13 show lateral elements of this plate, in the form of tabs 301i, 3012 making it possible to removably fix 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 fastening means (side members of the plate, in the form of tabs and corresponding elements of the housing, here notches). In each of FIGS. 8A-11B, there is shown 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 inlets and outlets 271i-27l4 ports that 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 carried out 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 can be removable relative to the plate 273, 273a; FIGS. 8B-8C and 11B, 12B, 12C show openings 291i-2913 making it possible to removably fix the corresponding element 275, 275a against the plate 273, 273a, for example using elements or means 291i-29l3 for assembling, for example by screwing, the element or portion 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 the latter with the rest of the housing. The element 275, 275a, then comprises a face 275i, 275ai of connection to the housing, provided with means 261i-26l4 of hydraulic connections to the conduits 23, 25, 60, 61, as shown in Figures 8C and 12C.

In order to allow an easy connection of the module to the rest of the device, the inlet and outlet ports 271i-27l4 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 represented in detail: this orifice extends in a substantially circular manner, perpendicular to the Figure 8B plane or XY plane, and is located in the YZ plane or in a plane (PI) 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 square (FIGS. 11A -13) and is in elevation or projection relative to said surface 273, 273a. It is provided with inlets and outlets 271i-27l4. FIGS. 8A and 11A show these inputs and outputs, which make it possible to connect the two pumping elements assembled in the module to the rest of the ink circuit: the input 271i for the input into the pump 24; the outlet 2712 for the outlet of the pump 24, the inlet 2713 for the inlet of the fluid in the pump 64, the outlet 2714 for the outlet of the fluid of the pump 64, towards the reservoir 11.

The fluid entering or exiting through each of these inlets or outlets flows, through said inlet or outlet, substantially parallel to the 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, towards the pump 24.

Finally, the module 270, 270a also contains the fluidic connection means between each of the elements it contains (the pressure pump 24 and the recovery pump 26) and the inlet and outlet 271i-27l4 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 272i-2724 which connect the conduits 23, 25, 60, 61 to the inputs and outputs 271i-2714, possibly via the connections 261i-2614. These ducts may be bent to join the corresponding duct (see the duct 23 of Figure 8B) and the inlet or outlet orifice arranged 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 FIGS. 11A-13, these ducts project 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 Outlets 271i-27l4 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 that enters or exits through each of these inputs or outputs flows, through said inlet or outlet, substantially parallel to the plate 273 and substantially 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 inlets and outlets 271i-27l4, 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 Figure 9), substantially parallel to the plate 273, of the entire module, thus facilitating the installation and disassembly thereof.

More precisely, 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 271i-27l4 being arranged along 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 to 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, relative to each other, the element 275 and the connection element 285. This opening lies 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 and the mechanical connection of the 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, whose connection face provided with the inlet and outlet orifices 271i-27l4, and the face intended to be pressed against the plate 273a.

One embodiment of the connection 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-beam or a beam, which is extends in the Y direction and is in elevation or projection with respect to a surface 283 (which extends along the YZ plane). This connection element 285 is intended to be inserted into the volume delimited by the "U" of the element 275. On an upper surface of this element 285 there are holes 281i-28l4, each of which is intended to be aligned and in contact with one of the orifices 271i-27l4. The element 285 is traversed by conduits 282i-2824 which fluidly communicate the orifices 281i-28l4, and thus the conduits 23, 25, 60, 61, with the rest of the circuit.

In the embodiment illustrated in FIGS. 11A-13, connecting elements 281i-28l4 and 287i-2872 corresponding to the elements 271i-27l4 and lllvllh are disposed on the surface 283, each of them being intended to be aligned and in contact with one of the orifices 271i-2714, 277i-2772

The elements of the remainder of a circuit such as that of FIG. 3C, not contained in the case 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 may be provided for fixing the assembly in a simple manner, for example by screwing; for this purpose, the plate 275, 275a may be provided with holes 277i-2772 in which screws or studs or rivets may be inserted and then inserted into corresponding members, for example into holes, which may be threaded or tapped, made in the rest of the device, including holes 287i - 2872 of the element 285 or 283 (Figure 13). Other fastening means can be used, for example by lateral claws, the element 275, 275a can then be provided with elements, for example pins, locating 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 to be connected, when the module is mounted, means for feeding the printer. 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 simply and quickly, after having removed the fastening holding 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 one with the other.

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

Each of the inputs / outputs 271i-27l4 and 281i-28l4 may comprise one end of a duct, itself provided with a seal. For example, each of the inlets / outlets is provided with an O-ring which bears, in the operating position, against a concentric seal surface, of the corresponding inlet / outlet 281i-28l4 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 conduit ends, each of which has a concentric seal range. The invention can be implemented in a printer such as that described above in connection with FIG. 1. This includes in particular a print head 1, generally offset relative to the body of the printer, and connected to it by means, for example in the form of a flexible umbilicus 2, bringing together 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, which will transmit the printing instructions to the head but also drive the pumps 24, 64 or motors and / or the valves 21, 22, 52, 54 of the system to manage the supply of the circuit in ink and / or solvent and the recovery of the mixture of ink and solvent from the head.

They can also collect the level information provided by the level measurement means 13, 15, 15a in the reservoirs 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 (27)

A device for supplying ink and solvent to the printhead (50) of an inkjet printer, comprising: - at least a first reservoir (11) and a second reservoir (12), different first, means (60, 61, 64) for collecting in the first reservoir (11) a stream of recovery ink from a gutter of the print head, the first reservoir having a first output (lli ), for sending ink from this first reservoir to the printhead, the second reservoir having a second liquid outlet (II2), for sending solvent 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 delivery to the dispenser head. printing (50). 2. Device according to claim 1, further comprising at least one damping device (26, 26a, 26b) for damping fluctuations or ripples of ink pressure 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 ink and / or solvent circulation 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 selection means for selectively connecting the first output and / or the second output 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, further comprising means (3) for, using the selection means, adding at least a quantity of solvent, as a function of at least one pressure value or pressure variation. 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 amount of solvent to the pump (24) and to send this amount 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, downstream of the pump: - a first supply path (32) of the print head in ink and / or solvent, this first path possibly comprising a damping device (26b), - a second supply path (34), parallel to the first feed path, for supplying the printing head with solvent. means (30) for selecting said first feed path (32) or said second feed path (34). 11. Device according to one of claims 1 to 10, further comprising means (71 - 74, 76, 78) for imposing an operating pressure to the common pump (24). 12. Device according to one of the preceding claims, comprising at least one conduit (71, 72, 74) back, from at least one supply line (32, 34) of the print head to one of the two reservoirs (11, 12), this 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 this duct back. 13. Device according to claim 10, comprising two ducts (71, 72, 74) back to one of the two tanks (11, 12), each associated with a feed path (32, 34) of the head and being disposed from a point downstream of the common pump (24) and having means forming a restriction (73, 76, 78) of the flow in this return duct. 14. Device according to claim 12 or 13, further comprising means (3) for detecting a blockage of said restriction. 15. Device according to one of claims 1 to 14, further comprising means (3) for adjusting the speed of the pump (24) according to a given pressure value. 16. Device according to the preceding claim wherein the means (3) for adjusting the speed of the pump (25) proceed by dichotomy. 17. Device according to one of the preceding claims, further comprising means (3) for performing an air purge may be present in the supply device. 18. A method for supplying the ink and solvent of the print head (50) of an inkjet printer, comprising: - the taking of ink or solvent, respectively from at least one first reservoir (11), containing ink, and a second reservoir (12), different from the first and containing solvent, using a common pump (24) for pressurizing the ink and / or solvent, a stream of recovery ink from a gutter of the print head being sent to the first reservoir (11), - sending ink and / or solvent to the head printing (50) using said common pump (24). 19. 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. 20. Method according to one of claims 18 or 19, wherein measuring a pressure of ink and / or solvent sent to the print head. 21. 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. 22. Method according to the preceding claim, said amount of solvent taking into account the dilution of the ink by the solvent. A method according to claim 21 or 22, wherein a plurality of amounts of solvent, alternating with ink, are sent to the print head to allow mixing of the solvent and the ink. 24. Method according to one of claims 21 to 23, wherein a number and / or a frequency of sending (s) of an elementary quantity of solvent to the pump (24) is calculated and this quantity of solvent is sent. , possibly at the calculated frequency, alternately with ink shipments to the pump. 25. Method according to the preceding claim, wherein the elementary amount of solvent added to the volume of the ink circuit for mixing it upstream of the head produces a relative viscosity variation of less than 1%. 26. Method according to one of claims 18 to 25, wherein downstream of the pump is selected: - a first supply path (32) of the print head for sending to it , ink and / or solvent, - or a second feed path (34), parallel to the first feed path, for supplying the print head with solvent. 27. Method according to one of claims 18 to 26, wherein the speed of the pump (24) is adjusted according to a given pressure value.