• 专利附录
  • 专利说明
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    • 专利摘要:
    The invention firstly relates to a print head of a continuous inkjet printer, comprising a first reservoir (12) and a second reservoir (22), arranged on both sides of at least one jet ejection nozzle (30) to which they are connected, and means (16) for applying a first pressure to the first reservoir, a second pressure to the second reservoir, the difference between these two pressures being variable.
    公开号:FR3065394A1
    申请号:FR1753509
    申请日:2017-04-21
    公开日:2018-10-26
    发明作者:Bruno Barbet
    申请人:Markem Imaje Industries SAS；
    IPC主号:
    专利说明:

    DESCRIPTION
    TECHNICAL AREA AND PRIOR ART
    The invention relates to the print heads of printers or printers with deviated continuous ink jet, possibly of the type provided with a multi-nozzle drop generator. It relates more particularly to a printhead or a printer with continuous jets in which the sorting of the drops is carried out according to a new principle.
    Continuous inkjet printers (CIJ) are well known in the field of coding and industrial marking of various products, for example for marking bar codes, the expiry date on food products, or even references or distance marks on cables or hoses directly on the production line and at high speed. This type of printer is also found in certain areas of decoration where the possibilities of graphic printing of technology are exploited.
    These printers have several typical subsets as shown in Figure 1.
    First of all, a print head 1, generally offset relative to the body of the printer 3, is connected to the latter by a flexible umbilicus 2 gathering the hydraulic and electrical connections necessary for the operation of the head by giving it flexibility that facilitates integration into the production line.
    The body of the printer 3 (also called desk or cabinet) usually contains three sub-assemblies:
    - an ink circuit in the lower part of the desk (zone 4 '), which allows on the one hand, to supply ink to the head, at a stable pressure and of an adequate quality, and on the other share to take care of the ink of the jets, not used for printing,
    - a controller located at the top of the desk (zone 5 '), capable of managing the sequencing of actions and carrying out the processing allowing the activation of the various functions of the ink circuit and of the head. The controller 5 may for example comprise a microcomputer or a microprocessor and / or one (or more) electronic card and / or at least on-board software, the programming of which ensures (s) the control of the ink circuit 4 and the print head 1. This controller makes it possible to transmit the print instructions to the head but also to drive the motors and the valves of the system in order to manage the supply of ink and / or solvent to the circuit as well as the recovery mixture of ink and air from the head. It is therefore programmed for this purpose,
    - 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 sub-assemblies: in the upper part, the electronics, the power supply and the operator interface, and in the lower part an ink circuit supplying the ink, of nominal quality, under pressure at the head and the depression of recovery of the ink not used by the head.
    FIG. 2 schematically represents a print head 1 of a CIJ printer. It comprises a drop generator 60 supplied with electrically conductive ink, pressurized by the ink circuit.
    This generator is capable of emitting at least one continuous jet through a small orifice called a nozzle. The jet is transformed into a regular succession of drops of identical size under the action of a periodic stimulation system (not shown) located upstream from the outlet of the nozzle. When the drops 7 are not intended for printing, they go to a gutter 62 which collects them in order to recycle the unused ink and return them to the ink circuit. Devices 61 placed along the jet (charge and deflection electrodes) make it possible, on command, to electrically charge the drops and to deflect them in an electric field Ed. These are then deviated from their natural path of ejection of the drop generator. The drops 9 intended for printing escape the gutter and will deposit on the support to be printed 8.
    This description can be applied to continuous jet printers (CIJ) called binary or multi-deflected continuous jet. Binary CIJ printers are equipped with a head whose drop generator has a multitude of jets, each drop of a jet can only be directed towards 2 paths: printing or recovery. In multi-deflected continuous jet printers, each drop of a single jet (or a few spaced jets) can be deflected on various trajectories corresponding to different charge commands from one drop to another, thus achieving a scan of the area to be printed in a direction which is the direction of deflection, the other scanning direction of the area to be printed is covered by relative displacement of the print head and the support to be printed 8. Generally the elements are arranged in such that these 2 directions are substantially perpendicular.
    An ink circuit of a continuous inkjet printer makes it possible, on the one hand, to supply ink under controlled pressure, and possibly solvent, to the drop generator of head 1 and, on the other hand hand, to create a depression to recover the fluids not used for printing and which then return from the head.
    It also allows the management of consumables (distribution of ink and solvent from a reserve) and the control and maintenance of the quality of the ink (viscosity / concentration).
    Finally, other functions are linked to user comfort and automatic handling of certain maintenance operations in order to guarantee constant operation whatever the conditions of use. Among these functions are the solvent rinsing of the head (drop generator, nozzle, gutter), assistance with preventive maintenance, for example the replacement of components with a limited life, in particular filters, and / or pumps.
    These various functions are activated and sequenced by the printer controller, which will be all the more complex the greater the number and sophistication of the functions.
    The voltages implemented by the charge and deflection electrodes 61 are high. They can be of the order of kV, requiring the use of “high voltage” type means. This sorting device therefore has manufacturing costs and requires specific maintenance; moreover, it is bulky. Furthermore, the fluid used must be electrically conductive. And the load carried by a drop must be able to be estimated, as well as the shape of the drop itself, the separation of which is preferably done without a satellite drop.
    The possibility is also known of deflecting jets using heating means arranged at the outlet of a nozzle, as described for example in document US 2003/0043223. This technique is complex to implement because it requires carrying out, around each nozzle, a heating resistor which goes all around the nozzle. In addition, the deflection angle obtained is not sufficient to carry out a correct sorting of the drops.
    The problem therefore arises of finding a new device for new methods of carrying out sorting of the drops, at the outlet of a print head, in a simpler, less costly and less bulky manner.
    STATEMENT OF THE INVENTION
    The invention relates firstly to a print head of a continuous inkjet printer, comprising a first reservoir and a second reservoir, arranged on either side, preferably symmetrically, with respect to at least one jet ejecting nozzle to which they are attached, and means for applying a first pressure tank 1, a 2 nd pressure on the 2nd tank, the two pressures may be different from one another, or alternatively equal then different from each other (or the difference between these 2 pressures being variable as a function of time).
    The pressure difference between the pressures of the 2 tanks makes it possible to create a specific orientation for a jet produced by the nozzle.
    The invention also relates to a print head of a continuous ink jet printer, comprising a reservoir (or a single reservoir), connected to at least one jet ejection nozzle by a channel, the junction between said channel and the nozzle having a non-zero radius of curvature, and means for applying a variable pressure to the reservoir as a function of time.
    Preferably, this radius of curvature R c is between 0.5 Db and 1.5 Db, where Db denotes the outlet diameter of the nozzle.
    Whatever the embodiment of the invention, a hydrodynamic deflection is thus created in order to sort out the drops to be printed and those which go to recycling.
    Such a print head does not require a high voltage applied to a charging electrode, then to a deflection electrode, such electrodes not being used. It also does not require a sorting system downstream of the nozzle plate.
    Nor does such a printhead require the use of a heating resistor at the outlet of a nozzle.
    A device according to the invention is therefore also much simpler than the structures known from the prior art.
    According to one embodiment, the means for applying pressure to one and / or the other of the reservoirs (whether it is a printhead according to the invention comprising one, or only one, reservoir or 2 tanks) comprises piezoelectric means for applying the pressure to the 1 st tank, and optionally the piezoelectric means for applying a 2 nd pressure on the 2nd tank.
    The activation of these means can be controlled by the printer controller.
    According to a particular embodiment, the piezoelectric means are arranged on the side of the reservoir (s) into which the nozzle (s) opens, or on the opposite side.
    Control means can make it possible to apply (or are provided for, or programmed to apply), successively or alternately, different pressures at the 2 tanks, then an identical pressure at the two tanks. In the case of a structure with a single reservoir, control means make it possible to apply (or are provided for, or programmed to apply) a variable pressure to this reservoir.
    Whatever the embodiment considered, the or each reservoir can be connected to the nozzle by at least one conduit and / or a chamber.
    For example, the, or each, tank can be connected to the nozzle by a chamber, then a column, then a conduit.
    A printhead according to the invention can comprise a plurality of jet ejection nozzles, and means associated with each nozzle, for applying:
    - a first pressure to a portion of the tank 1, a 2 nd pressure to a portion of the 2nd tank, the two pressures being different from each other;
    - or (in the case of an embodiment with a reservoir) to apply variable pressure to the reservoir or to part of the reservoir.
    Preferably, the portion of fluid situated at the inlet of a nozzle of diameter Db has a height Hc, H c / Db being between 0.5 and 1.5.
    More preferably, the portion of conduit which brings the fluid located at the inlet of a nozzle has a curvature.
    The invention also relates to an ink jet printer comprising a printhead according to the invention, means for supplying ink and / or solvent for this print, and means for recovering unused ink for the impression.
    The invention also relates to a method of operating a print head of a continuous ink jet printer, comprising a first reservoir and a second reservoir, arranged symmetrically with respect to a jet ejection nozzle, to which each of the reservoirs is connected, a process in which different pressures are applied to the 2 reservoirs, thereby producing a deflection of the ink jet which leaves the nozzle.
    The invention also relates to a method for operating a print head of a continuous inkjet printer, comprising a reservoir (or a single reservoir), connected to at least one jet ejection nozzle by a channel, the junction between said channel and the nozzle having a non-zero radius of curvature, a method in which a pressure variation is applied to the reservoir, thus producing a deflection of the ink jet which leaves the nozzle.
    According to one embodiment, as already explained above, the different pressures applied to the reservoirs, or the pressure variations applied to the reservoir, are obtained using piezoelectric means.
    The deflection of the jet can be between 3 ° and 10 °, relative to the axis of a jet which leaves the nozzle while being non-deflected.
    The nozzle clearance exit speed can be of the order of 10 m / s, or between 2 m / s and 15 m / s.
    In the case of two tanks, after applying different pressures to the 2 tanks, the same pressure can be applied to the two tanks, thus producing an undeviated ink jet.
    The embodiment with two tanks on either side of a nozzle offers the advantage of being able to circulate a liquid, for example a cleaning liquid such as solvent, from one of the tanks to the other without feed the nozzle and therefore not clog it when transporting large debris (or debris of a size comparable to that of the diameter of the nozzle). Conversely, in the embodiment with a reservoir, a liquid, for example solvent, is drained by the nozzle, which can become clogged if large debris (in the sense above) is present.
    BRIEF DESCRIPTION OF THE DRAWINGS
    An exemplary embodiment of the invention will now be described with reference to the accompanying drawings in which:
    FIG. 1 represents a known structure of a printer,
    FIG. 2 represents a known structure of a print head of a CIJ type printer,
    FIG. 3 represents a sectional view of a printing head according to one aspect of the invention, the section being made along a parallel to the plane YZ and containing the axis Z of a nozzle,
    FIG. 4 represents the production and the deflection of drops using a printing head having a structure according to FIG. 3,
    FIG. 5 represents the evolution of the pressure generated by piezoelectric means as a function of the amplitude of the oscillation applied to these means,
    FIGS. 6A and 6B represent a sectional view and a top view of another print head according to the invention,
    FIG. 7 represents a top view of a variant of a printing head according to FIGS. 6A and 6B,
    FIGS. 8A and 8B show a sectional view and a top view of another print head according to the invention,
    FIG. 9 represents a top view of a variant of a print head according to FIGS. 8A and 8B,
    FIGS. 10A - 10C and 11A - 11B represent simulation and test results for a print head according to the invention,
    FIGS. 12A - 12B represent other aspects relating to a printhead according to the invention,
    FIGS. 13A and 13B show other simulation results for a print head according to the invention,
    FIG. 14A represents a sectional view of a printhead according to another aspect of the invention, the section being made along a parallel to the plane YZ and containing the axis Z of a nozzle,
    FIG. 14B - 14G represent sectional and top views of other embodiments of a print head according to the invention,
    FIG. 15 represents a structure of an ink jet printer to which the present invention can be applied,
    - Figure 16 shows a functional view of the printer.
    In the figures, similar or identical technical elements are designated by the same reference numbers.
    DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS
    A printhead structure according to the invention, and its operation, are shown in FIGS. 3 and 4.
    The print head comprises a first and a second reservoir 12, 22 arranged on either side, of a flow axis of an ejection nozzle 30, to which they are each connected by a conduit 14, 24. The two tanks are supplied by an ink supply circuit, for example of the type described in FR-2954216, from a main tank of the printer, using a pump.
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    Other elements associated with the head can be those described above in connection with FIGS. 1 and 2.
    Preferably, the 2 tanks are arranged symmetrically (which is the case for the systems shown in the figures and in general for those presented below) with respect to the flow axis of the ejection nozzle 30. A plane parallel to the plane OXZ is then a plane of symmetry from a geometry and flow point of view.
    In a variant (not shown in the figures), the 2 tanks are arranged asymmetrically with respect to the flow axis of the ejection nozzle 30. The parameters or the operating conditions, mentioned above, are then adapted. below or in the present application for a symmetrical structure, and in particular the volumes, distances and pressures, in order to obtain the desired operation of an asymmetrical structure.
    The direction of flow, inside the conduits 14, 24, is advantageously substantially perpendicular to the flow axis of the ejection nozzle 30. As a variant, it is possible to have an inclination of these conduits 14 , 24 with respect to this direction perpendicular to the axis of flow of the nozzle.
    Under the effect of the pressures in the reservoirs, a jet is formed, which may or may not be deviated from a rectilinear trajectory, the axis 41 of which is an axis of symmetry for the ejection nozzle 30. The direction followed by the jet is a function of the difference between the pressures in the 2 tanks. The hydrodynamics of the system (in fact: the action of surface tension forces) causes the formation, from the jet, of drops 32, 34, which may therefore be deflected, or not. The deviation is caused neither by the effect of an electric field on the charges contained in the drops, nor by the effect of heating at the outlet of the nozzle, nor by an air flow. In particular, the system does not use any charging electrode and no deflection electrode to act on the path of the ink section which leaves the nozzle 30 or on the drops 32, 34. It does not use any more heating means at the outlet of the nozzle. It also does not use means to produce an air flow for the deflection. The system is therefore, compared to known systems, greatly simplified.
    A recovery gutter 37 makes it possible to receive the non-deviated drops 32, while the deviated drops 34 will be used for printing on a printing medium 150. The gutter is, itself, connected to a hydraulic circuit 370 for recovery ink. According to another embodiment, it is the deflected drops which could be recovered, while the non-deflected drops would be used for printing.
    The pressure in the reservoir 12 is designated by PI and the pressure in the reservoir 22 by P2.
    When PI = P2, the jet formed is not deflected and only drops, the trajectory of which is aligned on the axis 41 of the nozzle, are produced.
    When PI * P2, the jet formed is deflected and only drops, the trajectory of which deviates from the axis of the nozzle, are produced.
    When, successively, the pressures satisfy the equality PI = P2, then differ between them (PI * P2), there occurs, successively, the emission of a jet aligned with the axis 41 of the nozzle, then l 'emission of a jet which deviates from the axis of the nozzle.
    For a certain time t1, it is therefore possible to orient the jet in one direction (for printing for example) and for another time t2, the jet is oriented in the other direction to recycle the ink.
    More generally, a static pressure is initially applied to the 2 reservoirs, which makes it possible to produce a jet, preferably continuous, aligned on the axis 41 of the nozzle. The application of pressure variations to one and / or the other reservoir will make it possible to deflect the jet with respect to its initial trajectory aligned on the axis 41.
    According to a particular embodiment, the pressures and their variations in each of the reservoirs can be produced by piezoelectric means 16 (16 '), 26 (or 26'). Means of this type can be controlled:
    - with activation voltages of the order of a few tens of volts, for example between 5 V and 50 V;
    - And / or with one or more high frequency (s), for example between 50 kHz and 500 kHz; in comparison, the frequencies obtained using solenoid valves reach at best 1 kHz.
    As illustrated in FIG. 3, piezoelectric means 16 (or 16 ′) are formed above the upper wall of the reservoir 12 (or below the reservoir 12 and possibly of the channel 14) while piezoelectric means 26 ( or 26 ') are formed above the upper wall of the reservoir 22 (or below the reservoir 22 and possibly the channel 24).
    The pressure generated by each of the piezoelectric means follows a curve, as a function of the amplitude of the oscillation applied to these means, which is illustrated in FIG. 5: below a certain critical threshold Ac of the amplitude, the pressure varies little and remains stable. Above this threshold, a non-linear regime appears and the pressure increases as a function of amplitude A.
    Consequently, by applying oscillations of different amplitudes to the means 16 (16 '), 26 (26'), it is possible to generate pressure differences between the two reservoirs. For example, the piezoelectric means 16 are activated so as to cross the threshold Ac of appearance of the non-linear regime, while the piezoelectric means 26 are activated so as to remain below this threshold.
    It is therefore possible, by this system, to produce a pressure difference between the reservoirs, which leads to a deflection of the jet formed at the outlet of the nozzle.
    To enhance the effect, the actuator, or each piezoelectric element can work at its resonant frequency, which is preferable to promote a greater amplitude of deformation.
    As illustrated in FIG. 4, the activation of the means 16 (16 '), while the means 26 are not activated, leads to a deflection of the jet in the direction 44; conversely, the activation of the means 26 (26 '), while the means 16 (16') are not activated, leads to a deflection of the jet in the direction 42. In both cases, activation means the application of '' an oscillation of amplitude greater than the threshold Ac for triggering the non-linear regime.
    The invention makes it possible to deflect a jet, with respect to the axis 41 of the nozzle, by an angle which can be of the order of a few degrees, for example between 3 ° and 10 °. This is sufficient for application to a continuous inkjet printer.
    Another example of a printhead structure is illustrated in Figures 6A and 6B. FIG. 6A is a sectional view of this structure, produced along a parallel to the plane OYZ of a tri-rectangular reference frame OXYZ, the axis X being directed perpendicular to the figure.
    References 12 and 22 also designate the 2 reservoirs into which 2 two chambers 52, 62 open, oriented along a plane parallel to the OXY plane. Piezoelectric means 16, 26 can be formed above the upper wall of the chamber 52, 62, in order to produce the pressure variations which allow the jet to be deflected, as explained above in connection with the figures 3-5 (in this figure and the following figures, means 16 ', 26' are also mentioned in the lower part of the device; we will not systematically refer to this variant in the following, but it should be understood that it is covered by the various structures described below). Each tank can be supplied from the outside via a conduit 121,
    221.
    Each of these chambers is followed by a cylindrical column 54, 64, of height H + H c (this column is directed along the axis Z), connected to the corresponding chamber 52, 62 by a 1st bend.
    Finally, a conduit 56, 66 (directed parallel to the axis Y), of height H c , connects each cylindrical column 54, 64 with the inlet orifice of the nozzle 30, of length hb (this length being measured according to the Z axis or along the flow axis 41). This conduit 56, 66 is also connected to the corresponding cylindrical column by a 2 nd bend.
    The nozzle 30 has a diameter Db (measured in the OXY plane, that is to say in a plane which extends perpendicular to the Z axis or to the axis 41) for example between a few 10 pm and 100 pm.
    Preferably, H c / Db is between 0.5 and 1.5: this condition allows the fluid to be diverted (or even: when the fluid flow is diverted from the OXY plane towards the axis 41 or towards the axis Z) in a satisfactory manner when it passes from the conduits 56 or 66 to the nozzle 30.
    FIG. 6B shows a top view of the structure of FIG. 6A. As can be seen in this FIG. 6B, the tanks 12, 22 and the chambers 52, 62 have the same depth along the axis X. In this figure, there is shown a single nozzle 30 disposed between the two tanks and the assembly means 50, 56, 62, 66 which make it possible to bring the ink from these reservoirs to the nozzle 30.
    FIG. 7 is another top view of a variant of the previous structure, the section of which, according to an OYZ plane, is identical to that of FIG. 6A; according to this variant, it is also possible to have a plurality of nozzles 30i, 30 2 , ... 30 n (for example: n = 2 or 8, or 16, or 32, or 64 ...) aligned along an axis parallel to the X axis. Again, on each side of a plane of symmetry which passes through the orifices of the nozzles 30i - 30 n and which parallel to the plane OXZ, a single reservoir 12, 22, opens into the chamber 52, 62 , which opens into the corresponding conduit 56, 66.
    In the structure of FIG. 7, piezoelectric means
    16i, 16 2 , 16 3 16 n , 26i, 26 2 , 26 3 ..... 26 n , can be formed above the upper wall of the chamber 52, 62, a pair of piezoelectric means 16 ,, 26, being associated with the nozzle 30 ,, the means 16 ,, 26, being arranged on either side thereof, to activate the portion of the chamber 52, 62 which leads to said nozzle, substantially along an axis parallel to OY. There is therefore, along the axis OX, on the one hand a succession of piezoelectric means 16i, 16 2 < 16 3 16 n , and, on the other hand, a succession of piezoelectric means 26i, 26 2 < 26 3 ...., 26 n .
    Another print head structure according to the invention is illustrated in FIGS. 8A and 8B. FIG. 8A is a sectional view of this structure, produced along a parallel to the plane OYZ of a tri-rectangular reference frame OXYZ, the axis X being directed perpendicular to the figure.
    References 12 and 22 also designate the 2 tanks which open directly onto the nozzle 30. Piezoelectric means 16, 26 can be formed above the upper wall of each tank, in order to achieve the pressure variations which allow deflect the jet, as explained above in connection with Figures 3-5.
    Each tank has a height H c . The nozzle 30 has a diameter Db for example of between a few 10 pm and 100 pm.
    Preferably, H c / Db is between 0.5 and 1.5: this condition allows the fluid to be diverted satisfactorily when it passes from the reservoir 12, 22 to the nozzle 30.
    FIG. 8B shows a top view of the structure of FIG. 8A. As can be seen in this FIG. 8B, the reservoirs 12, 22 have the same depth along the axis X. In this figure, a single nozzle 30 is shown arranged between the two reservoirs.
    But, as illustrated in FIG. 9, which is another top view of a structure whose section, according to an OYZ plane, is identical to that of FIG. 8A, it is also possible to have a plurality of nozzles 30i, 30 2 , ... 30 n (for example: n = 8, or 16, or 32, or 64 ...) aligned along an axis parallel to the X axis. Again, there is a single reservoir 12, 22 of each side of the axis along which the nozzles 30i - 30 n are aligned. The entire device therefore has symmetry with respect to a plane parallel to OXZ and which passes through the axis along which the nozzles are aligned.
    In the structure of FIG. 9, piezoelectric means
    16i, 16 2 , 16 3 16 n , 26i, 26 2 , 26 3 ..... 26 n , can be formed above the upper wall of each tank 12, 22, a pair of piezoelectric means 16 ,, 26, being associated with the nozzle 30 ,, the means 16 ,, 26, being arranged on either side thereof, to activate the portion of each reservoir 12, 22 which leads to said nozzle, substantially along an axis parallel to OY.
    Again, each reservoir has a height H c , each nozzle having a diameter Db for example between a few 10 pm and 100 pm; preferably, H c / Db is between 0.5 and 1.5, with the same technical effect already mentioned above.
    In the above embodiments, the means 16, 26 for piezoelectric activation are shown above each of the reservoirs 12, 22. Alternatively, these means can be arranged on the opposite side, as shown in broken lines in Figures 3, 6A, 8A. The thickness of the bottom wall, on which the corresponding means are positioned, is adapted to the presence of these means.
    From the structure of FIGS. 8A and 8B, a simulation has been carried out, the result of which is illustrated schematically in FIGS. 10A-10C.
    The reservoir 12 is under pressure (2 to 3 bars), the reservoir 22 is closed. The nozzle 30 is the only outlet for the ink. The jet flows from the nozzle, in air at atmospheric pressure, with an average speed Vb = 10 m / s.
    In FIG. 10A, the state of a jet coming out of the nozzle 30 is shown when the pressures between the two reservoirs 12, 22 are not identical.
    We can therefore effectively obtain a deflection of the jet, with a deflection angle, between the direction of flow of the deflected jet and the axis 41 of the nozzle 30, of several degrees, as explained above in connection with FIGS. 3 -5.
    FIG. 10B shows speed profiles in the reservoir 12 (the reservoir 22 being closed), then in the nozzle 30 and in the air, at the outlet of the nozzle. There is a parabolic profile of the speed in the tank. The speed of the jet in the air (approximately 10m / s) is slightly lower than its value at the outlet of the nozzle. This difference is among other things due to the drag in the air. It can be seen, moreover, that the speed profile is gradually deflected towards the left part of the figure.
    FIG. 10C represents curves which give, as a function of the spacing with respect to the axis 41 of the nozzle, the speed of the ink entering the nozzle 30 (curve I), in the middle of the nozzle (curve II), and at the outlet of the nozzle (curve III).
    The asymmetry of the curve I with respect to the axis 41 of the nozzle reflects the fact that the pressure in one of the tanks is greater than the pressure in the other tank. As a result, at the outlet of the nozzle 30, a speed profile which is not symmetrical with respect to the axis of the nozzle (curve III), which results in a deflection of the jet. A perfectly parabolic speed profile at the input of
    0 nozzle 30 would give rise to a jet aligned with the hydraulic axis 41 of the nozzle.
    The angle of deflection of the jet is approximately 3.25 ° for a jet speed, at the outlet of the nozzle, of approximately 10 m / s.
    Another aspect of the invention is illustrated in FIGS. 11A and 11B, the latter being an enlargement of part of FIG. 11A. These figures
    5 show the static pressure field of the structure of FIGS. 8A and 8B, under the conditions already mentioned above in connection with FIGS. 10A - 10B. We see in these figures that the pressure gradually decreases in the duct and becomes almost zero in the air. In the angular zone designated by the letter A, which corresponds to the zone where the reservoir 12 joins the nozzle 30, the pressure is negative. This area can therefore be subject to cavitation phenomena, sources of jet instability. To limit this problem, it is preferable to make a junction, between the cavity 12 and the inlet of the nozzle 30, which has a non-zero radius of curvature (the center of curvature being located on the side external to the device, and not on the side of the reservoir 12), as illustrated with the broken line 31 in FIG. 11B. This result, presented within the framework of a particular structure (FIG. 12A) can be transposed into each of the other structures (FIGS. 6A-6B, 7).
    According to an exemplary embodiment, the structure of FIG. 12A has the following geometric characteristics:
    L c = 125 µm (length of the conduit); d c = 50 pm (height of the duct); hb = 50 µm (nozzle height); db = 50 µm (diameter of the nozzle);
    L zm = 15 pm (length of the dead zone).
    For a structure such as that of FIG. 12A, in FIG. 12B, the deflection angle is presented as a function of the radius R c of curvature of the part 31 of the nozzle for a variant in which the nozzle is only supplied 'a side. The ink has a density p of 870 kg / m 3 , a viscosity p = 0.004 Pa.s, a surface tension σ = 0.023 N / m, the properties of air being a density p of 1.2 kg / m 3 and a viscosity p = 0.001 Pa.s.
    By varying the value of the speed of entry into the nozzle (for example successively by 2 and 8 m / s), the continuous ink jet admits two directions separated by an angle of 8.5 °. The continuous jet at 8 m / s has an angle of 8.5 ° relative to the geometric axis of the nozzle (see Figure 13A). The speed transition to 2 m / s for a period of 100 ps makes it possible to form a drop with a direction almost coincident with that of the hydraulic axis of the nozzle.
    A desired objective is to be able to sort drops intermittently, that is to say, for a certain time, to orient the jet in one direction (for printing, for example) and, for another time, to orient the jet in the other direction (for example to recycle the ink).
    To obtain drops from a continuous jet, the jet is broken into portions of jets which are not too long and which eventually become drops under the action of surface tension.
    An example of a process implemented with the structure of FIG. 12A, can be as follows:
    • An ink jet is ejected at a speed of 8 m / s continuously; This jet is deflected and collected by a gutter (not shown);
    • The ejection speed is reduced for the duration of 100 ps, the jet then being substantially in the axis of the nozzle.
    • A new jet is ejected with a speed of 8m / s while being deflected.
    Modeling, illustrated in FIG. 13A, made it possible to calculate an angle of the hydrodynamic deflection of the jet of 8.25 °. At a distance of 5 mm from the outlet of the nozzle, the differential deflection is typically 750 μm, which makes it possible to easily place a gutter spout to collect the continuous jet and allow the drop (intermittent) to flow towards the printing medium. formed in the continuous stream.
    FIG. 13B shows an example of variations in speed as a function of time to obtain an effect as described above. The maximum speed here is around 6 m / s and then is greatly reduced for around 100 ps.
    As explained above, a structure such as that of FIG. 12A, comprising a radius R c of curvature of the part 31 of the nozzle can be applied to a variant in which the nozzle is supplied only on one side.
    Thus the structure illustrated in FIG. 14A, which has only one reservoir 12, also makes it possible to carry out a deflection of a jet as a function of the pressure in this reservoir.
    In this embodiment, the print head comprises only a reservoir 12 and an ejection nozzle 30, which are connected together by a conduit 14, which preferably has a direction of flow substantially perpendicular to the axis d natural flow from the nozzle 30. The reservoir is supplied by an ink supply circuit, for example of the type described in FR-2954216, from a main reservoir of the printer, using a pump.
    Other elements associated with the head can be those described above in connection with FIGS. 1 and 2.
    The junction 31 between the nozzle 30 and the duct 14 has a non-zero radius of curvature, the center of curvature of which is situated on the side external to the device, and not on the side of the duct 14.
    Under the effect of the pressure variations in the reservoir 12, a jet is formed, which may or may not be deviated from a rectilinear trajectory, the axis 41 of which is an axis of symmetry for the ejection nozzle 30. The direction followed by the jet is a function of the pressure in the reservoir 12. The hydrodynamics of the system (in fact: the action of surface tension forces) causes the formation, from the jet, of drops which can therefore be deflected, or not. Again, the deviation is caused neither by the effect of an electric field on the charges contained in the drops, nor by the effect of heating at the outlet of the nozzle, nor by an air flow. In particular, the system does not use any charging electrode and no deflection electrode to act on the path of the ink section which leaves the nozzle 30 or on the drops. It also does not use heating means at the outlet of the nozzle. Nor does it use any means to produce an air flow for the purpose of deflection. The system is therefore, compared to known systems, greatly simplified.
    Similarly to what has been described above in connection with FIG. 4, a recovery gutter 37 makes it possible to receive the non-deflected drops, while the deflected drops will be used for printing on a printing medium. The gutter is itself connected to a hydraulic circuit 370 for recovering the ink. According to another embodiment, it is the deflected drops which could be recovered, while the non-deflected drops would be used for printing.
    For a certain time t1, it is therefore possible to orient the jet in one direction (for printing for example) and for another time t2, the jet is oriented in the other direction to recycle the ink.
    More generally, a static pressure is initially applied to the reservoir 12, which makes it possible to produce a jet, preferably continuous, aligned with the axis 41 of the nozzle. The application of a pressure variation will make it possible to deflect the jet with respect to its initial trajectory aligned on the axis 41.
    The pressure variations in the reservoir 12 can be produced by piezoelectric means 16, which can be controlled with activation voltages and / or with frequencies which have already been indicated above.
    As illustrated in FIG. 14A, the piezoelectric means 16, 16 ′ can be formed above the upper wall of the reservoir 12 or below the reservoir 12 and possibly the channel 14.
    The pressure generated by the piezoelectric means follows the curve illustrated in FIG. 5 as a function of the amplitude of the oscillation applied to these means.
    Consequently, by applying oscillations of variable amplitudes to the means 16 or 16 ′, it is possible to generate pressure differences in the reservoir 12. For example, the piezoelectric means 16 or
    16 ′ are activated so as to cross the threshold Ac for the appearance of the nonlinear regime, then to remain below this threshold.
    It is therefore possible, by this system, to produce a pressure variation in the reservoir 12, which alternately leads to a deflection of the jet formed at the outlet of the nozzle and then to a jet aligned on the axis of the nozzle.
    To enhance the effect, the actuator, or each piezoelectric element can work at its resonant frequency, which is preferable to promote a greater amplitude of deformation.
    Here again, the invention makes it possible to deflect a jet, with respect to the axis 41 of the nozzle, by an angle which can be of the order of a few degrees, for example between 3 ° and 10 °. This is sufficient for application to a continuous inkjet printer.
    A deflection effect with a structure such as that of FIG. 14A is more sensitive if the radius of curvature R c of the part 31 is between 0.5 Dbet 1.5 Db, where Db denotes, as above, the diameter of the nozzle.
    Structures such as those of each of FIGS. 6A-9 can be produced with the structure of FIG. 14A. Thus, FIGS. 14B - 14G show the structures, respectively of FIGS. 6A - 9, truncated on one side along a plane parallel to the plane OXZ, located slightly beyond the nozzle 30. The reference numerals of FIGS. 6A - 9 denote in Figures 14B - 14G the same elements as in Figures 6A - 9 and the explanations given above in connection with these Figures 6A-9 also apply to these Figures 14B - 14G. Likewise, the indications already given for each of FIGS. 6A-9 with regard to the various parameters H, H c , Db, H c / Db, hb also apply here. In these figures, the junction 31 (visible in FIGS. 14B and 14E) between the nozzle 30 and the conduit 56 or the chamber 12 has a non-zero radius of curvature, the center of curvature of which is situated on the side outside the device, and not on the side of the duct 14. And, for reasons already indicated above, the radius of curvature R c of the part 31 is preferably between 0.5 Db and 1.5 Db, where Db denotes, as above , the diameter of the nozzle.
    A device according to the invention is supplied with ink by an ink tank not shown in the figures. Various means of fluid connection can be used to connect this reservoir to a print head according to the invention, and to recover the ink which comes from the recovery gutter. An example of a complete circuit is described in US 7,192,121 and can be used in combination with the present invention.
    Whatever the embodiment envisaged, the instructions for activating the means 16, 26, 16i-16 n , 26i-26 n for producing ink jets and the means for pumping the gutter are sent by means of control (also called "controller"). It is also these instructions which will make it possible to circulate ink under pressure in the direction of the print head, then to generate the jets according to the patterns to be printed on a support 8. These control means are for example produced in the form of a processor or a microprocessor, programmed to implement a method according to the invention.
    It is this controller which also controls the pumping means of the printer, and in particular of the gutter, as well as the opening
    0 and the closing of valves on the path of the various fluids (ink, solvent, gas). The control means can also ensure the storage of data, for example data for measuring ink levels in one or more reservoirs, and their possible processing.
    In Figure 1 we have represented the general structure of the main
    5 blocks of an inkjet printer which can implement one or more of the embodiments described above. The printer comprises a console 300, a compartment 400 containing in particular the circuits for conditioning the ink and the solvents, as well as reservoirs for the ink and the solvents (in particular, the reservoir from which the ink recovered by the gutter is brought back). Generally compartment 400 is in the lower part of the console. The upper part of the console contains the command and control electronics as well as display means. The console is hydraulically and electrically connected to a print head 100 by an umbilicus 203.
    A gantry not shown makes it possible to install the print head facing a print medium 8, which moves in a direction materialized by an arrow. This direction is perpendicular to an alignment axis of the nozzles.
    An example of a fluid circuit 400 of a printer to which the invention can be applied is illustrated in FIG. 16. This fluid circuit 400 comprises a plurality of means 410, 500, 110, 220, 310, each associated with a specific functionality. We also find the head 1 and the navel 203.
    This circuit 400 is associated with a removable ink cartridge 130 and a solvent cartridge 140, which is also removable.
    The reference 410 designates the main tank, which can accommodate a mixture of solvent and ink.
    The reference 110 designates the set of means which make it possible to withdraw, and optionally to store, solvent from a cartridge 140 of solvent and to supply the solvent thus withdrawn to other parts of the printer, whether it involves supplying the main tank 410 with solvent, or cleaning or maintaining one or more of the other parts of the machine.
    The reference 310 designates the set of means which make it possible to withdraw ink from an ink cartridge 130 and to supply the ink thus withdrawn to supply the main reservoir 410. As can be seen in this figure, according to the embodiment presented here, the sending, to the main tank 410 and from the means 110, of solvent, passes through these same means 310.
    At the outlet of the reservoir 410, a set of means, generally designated by the reference 220, makes it possible to pressurize the ink withdrawn from the main reservoir, and to send it to the print head 1. According to one embodiment, illustrated here by the arrow 250, it is also possible, by these means 220, to send ink to the means 310, then again to the reservoir 410, which allows a recirculation of the ink inside of the circuit. This circuit 220 also makes it possible to empty the reservoir in the cartridge 130 as well as to clean the connections of the cartridge 130.
    The system shown in this figure also includes means 500 for recovering fluids (ink and / or solvent) which returns from the print head, more precisely from the gutter 7 of the print head or of the circuit. head rinse. These means 500 are therefore arranged downstream of the umbilicus 203 (relative to the direction of circulation of the fluids which return from the print head).
    As can be seen in FIG. 16, the means 110 can also make it possible to send solvent directly to these means 500, without passing either through the umbilicus 203 or through the printing head 1 or through the recovery gutter.
    The means 110 can comprise at least 3 parallel solvent supplies, one towards the head 1, the 2nd towards the means 500 and the 3rd towards the means 310.
    Each of the means described above is provided with means, such as valves, preferably solenoid valves, which allow the fluid concerned to be directed towards the chosen destination. Thus, from the means 110, solvent can be sent exclusively to the head 1, or to the means 500 or to the means 310.
    Each of the means 500, 110, 210, 310 described above can be provided with a pump which makes it possible to treat the fluid concerned (respectively: 1st pump, 2nd pump, 3rd pump, 4th pump). These different pumps perform different functions (those of their respective means) and are therefore different from each other, even if these different pumps can be of the same type or similar types (in other words: none of these pumps n 'provides 2 of these functions).
    In particular, the means 500 comprise a pump (1st pump) which makes it possible to pump the fluid, recovered, as explained above, from the print head, and to send it to the main reservoir 410. This pump is dedicated the recovery of fluid from the print head and is physically different from the 4th pump of the means 310 dedicated to the transfer of the ink or from the 3rd pump of the means 210 dedicated to the pressurization of the ink in tank outlet 410.
    The means 110 comprise a pump (the 2nd pump) which makes it possible to pump the solvent and to send it to the means 500 and / or the means 310 and / or to the printing head 1.
    Such a circuit 400 is controlled by the control means described above, these means are generally contained in the console 300 (FIG. 16).
    权利要求:
    Claims (14)
    [1" id="c-fr-0001]
    1. Print head of a continuous inkjet printer, comprising a first reservoir (12) and a second reservoir (22), arranged on either side of at least one nozzle (30, 30i_ 30 n) jet ejecting to which they are attached, and means (16, 26, 16i, 16 _ n, 26i, - 26 n) for applying a first pressure tank 1, a 2 nd pressure 2nd tank, the difference between these 2 pressures being variable.
    [2" id="c-fr-0002]
    2. A printhead according to claim 1, comprising piezoelectric means (16, 26, 16i, 16 _ n, 26i, - 26 n) for applying the pressure to 1 st tank, a 2 nd pressure 2nd tank.
    [3" id="c-fr-0003]
    3. Printhead according to claim 2, the piezoelectric means (16, 26, 16i, _ 16 n , 26i, - 26 n ) being disposed on the side of the tanks into which the nozzle or nozzles (30, 30i_30 n ), or on the opposite side.
    [4" id="c-fr-0004]
    4. Print head according to one of claims 1 to 3, comprising control means (3) for successively applying different pressures to the 2 tanks, then an identical pressure to the two tanks.
    [5" id="c-fr-0005]
    5. Printhead according to one of claims 1 to 4, each reservoir being connected to the nozzle by at least one conduit (56, 66) and / or a chamber (52,62).
    [6" id="c-fr-0006]
    6. Printhead according to one of claims 1 to 5, each reservoir being connected to the nozzle by a chamber (52,62), then a column (54, 64), then a conduit (56, 66).
    [7" id="c-fr-0007]
    7. Printhead according to one of claims 1 to 6, comprising a plurality of nozzles (30i _ 30 n ) for jet ejection, and means (16, 26,16i, _ 16 n , 26i, - 26 n) associated with each nozzle for applying a first pressure to a portion of the tank 1, a 2 nd pressure to a portion of the 2nd tank, the two pressures being different from each other.
    [8" id="c-fr-0008]
    8. Printhead according to one of claims 1 to 7, the portion of fluid located at the inlet of a nozzle (30, 30i _ 30 n ) of diameter Db having a height Hc, H c / Db being between 0.5 and 1.5.
    [9" id="c-fr-0009]
    9. Printhead according to one of claims 1 to 8, the portion of conduit which supplies the fluid located at the inlet of a nozzle (30, 30i _ 30 n ) having a curvature (31).
    [10" id="c-fr-0010]
    10. Ink jet printer comprising a printing head according to one of the preceding claims, means (220, 410) for supplying ink and / or solvent for this printing, and means (500, 410 ) to recover ink not used for printing.
    [11" id="c-fr-0011]
    11. A method of operating a print head of a continuous inkjet printer, comprising a first reservoir (12) and a second reservoir (22), disposed on either side of a nozzle jet ejection, to which each of the reservoirs is connected, a process in which a variable pressure difference is applied to the 2 reservoirs, thereby producing a deflection of the ink jet leaving the nozzle.
    [12" id="c-fr-0012]
    12. The method of claim 11, wherein the deflection of the jet is between 3 ° and 10 °, relative to the axis of a jet which emerges from the nozzle being non-deflected.
    [13" id="c-fr-0013]
    13. Method according to one of claims 11 or 12, wherein the outlet speed of the nozzle clearance is of the order of 10 m / s.
    [14" id="c-fr-0014]
    14. Method according to one of claims 11 to 13, in which, after having applied a non-zero pressure difference to the 2 reservoirs, a zero pressure difference is applied, thereby successively producing a deflected ink jet then a jet not deflected.
    S.60683
    1/11
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    同族专利:
    公开号 | 公开日
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    US20180304619A1|2018-10-25|
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    法律状态:
    2018-04-26| PLFP| Fee payment|Year of fee payment: 2 |
    2018-10-26| PLSC| Search report ready|Effective date: 20181026 |
    2019-04-29| PLFP| Fee payment|Year of fee payment: 3 |
    2019-11-29| TP| Transmission of property|Owner name: DOVER EUROPE SARL, CH Effective date: 20191022 |
    2021-01-15| ST| Notification of lapse|Effective date: 20201214 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1753509A|FR3065394B1|2017-04-21|2017-04-21|METHOD AND DEVICE FOR HYDRODYNAMIC INKJET DEFLECTION|
    FR1753509|2017-04-21|FR1753509A| FR3065394B1|2017-04-21|2017-04-21|METHOD AND DEVICE FOR HYDRODYNAMIC INKJET DEFLECTION|
    EP18168081.0A| EP3392043A1|2017-04-21|2018-04-18|Method and device for the hydrodynamic deflection of an ink jet|
    US15/957,031| US10589518B2|2017-04-21|2018-04-19|Method and device for the hydrodynamic deflection of an ink jet|
    CN201810360309.XA| CN108724943A|2017-04-21|2018-04-20|The method and apparatus that fluid dynamic for black jet flow deflects|
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