Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/001—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means incorporating means for heating or cooling, e.g. the material to be sprayed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
  • B05B5/04—Discharge apparatus, e.g. electrostatic spray guns characterised by having rotary outlet or deflecting elements, i.e. spraying being also effected by centrifugal forces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field

Definitions

• the present invention relates to a method and a device for the emission of a liquid in a controlled manner.
• the invention finds applications in particular in the field of printing.
• the invention is in particular used for producing ink jet printheads.
• an oo and to be marked is located at a great distance from the print head, this distance being able to go from one to several centimeters.
• a high initial speed is therefore necessary to limit the effect of aerodynamic disturbances on the drops.
• This jet is fragmented into drops of ink using a piezoelectric crystal.
• the uncharged drops are not deflected and are recovered by a gutter before being recycled inside the printer where this process is carried out.
• the individual charge of a drop determines the amplitude of its deflection and therefore its position on the object to be marked in the direction of the electric field.
• the formation, the charge and the deflection of the ink drops are done in the same way as in the deflected continuous jet method, except that the amplitude of the deflection is identical for each drop.
• a row of regularly spaced nozzles is used, each corresponding to a position to be printed.
• the nozzle is a critical element because:
• a rotating cylinder or disc is impregnated with liquid and generates a cloud of small drops over its entire periphery.
• the cylinder can also be electrified to charge the drops of liquid, which makes it possible to obtain a better distribution of the drops on the objects to be covered and possibly to control the number or the size of the drops projected.
• Such devices have also been used for printing objects. There is then interposed, between the cylinder and an object to be printed, a screen which lets the ink drops pass only at predefined locations.
• a magnetic or electric field is used to deflect the drops of ink when it is desired to print a character.
• the only function of the electric or magnetic field is the deflection of the ink drops. As a result, the shape of the characters that can be printed is limited.
• the cylinder rotates inside a tube and has cavities arranged longitudinally to generate periodic pressure waves passing in front of orifices which are formed in the tube and through which flows
• This ink is channeled to form regularly spaced jets above an object to be printed.
• the pressure variations cause the jets to break into drops and, insofar as the pressure waves are synchronous in the different jets, the instant of separation of the drops is substantially identical for all the jets.
• the drops are then loaded and then deflected by means similar to those used in the continuous jet process (deflected or binary).
• the drops are also emitted continuously but, in this case, under the effect of centrifugal force. These drops are electrically charged and then deflected.
• a printing press each comprising an ink impregnated roller above which is an electrode provided with parallel grooves. Once detached from the roller by the action of the electrode, the ink drops are guided by the grooves in order to achieve the precision required for an office application.
• One effect of this guidance is to absorb part of the kinetic energy of the drops, which requires having the object to be printed at a very short distance (200 ⁇ m) from the end of the electrode and is not not compatible with most industrial printing applications.
• the object of the present invention is to remedy the above drawbacks.
• the present invention aims to send a liquid in a controlled manner towards an object on which one wishes to deposit this liquid, while allowing this object to be placed at a distance greater than those authorized by the known techniques, mentioned more high.
• the present invention relates to a method of emitting liquid to an object, this method being characterized in that one rotates a cylinder, in that one impregnates with a liquid at least the surface lateral side of this cylinder, and in that one applies, at least at one point of this external lateral surface and at predetermined times, a force which cooperates with the centrifugal force resulting from the rotation of the cylinder to cause a substantially tangential emission of a portion of liquid towards the object at these predetermined times, so as to project this portion of liquid directly onto the object.
• the liquid is supposed to be sensitive to the force applied.
• the present invention also relates to a device for emitting liquid to an object, this device being characterized in that it comprises:
• impregnation means provided for impregnating at least the external lateral surface of this cylinder with a liquid
• this device is intended for printing the object, said liquid is an ink and said force is able to cooperate with said centrifugal force to cause a substantially tangential emission of a drop of ink towards the object at said predetermined times, so as to project this drop of ink directly onto the object.
• a device is in particular usable for producing ink jet printheads.
• the external lateral surface of the cylinder comprises cavities capable on the one hand of promoting the accumulation of ink in these cavities to initiate the formation of drops and on the other hand of controlling the size of these drops.
• the part of the external lateral surface which is between the cavities with respect to the ink has a lower wettability than that of the bottom of these cavities in order to further promote the accumulation of ink in these cavities and to better control the size of the drops.
• the cavities can form circular grooves whose axis is the axis of the cylinder.
• said force is an electrostatic force and the ink has a non-zero electrical conductivity.
• the device can also comprise means for applying another electrostatic force capable of preventing the emission of the ink drop when no printing is desired.
• the external lateral surface of the cylinder comprises a first electrically conductive layer and a two: th layer which covers the first layer and has, vis-à-vis the ink, a lower wettability than that of this first layer, cavities being formed through this second layer, the first layer forming the bottom of these cavities, the means for applying said electrostatic force comprising at least one electrode intended to be brought to an electrical potential different from that to which the first layer is worn.
• the external lateral surface of the cylinder comprises a first electrically conductive layer, a second electrically insulating layer which covers the first layer and a third electrically insulating layer which covers the second layer and has, opposite ink, wettability lower than that of this second layer, cavities being formed through this third layer, the second layer forming the bottom of these cavities, the means for applying said electrostatic force comprising at least one electrode intended to be brought to an electrical potential different from that to which the first layer is worn, the device further comprising means capable of electrically charging the drops.
• the device may further comprise an ink tank through which the outer lateral surface of the rotating cylinder passes, and means for removing excess ink from this surface.
• the cylinder is hollow and contains ink as well as a porous layer which surrounds the ink contained in the cylinder and through which the ink diffuses towards the outside of the cylinder.
• the hollow cylinder may contain a removable ink cartridge, the porous layer of which constitutes an outer envelope.
• the ink may be hot-melt and the device may further comprise means for heating this hot-melt ink.
• the means for applying said force are provided for applying this force to a plurality of points arranged along a generatrix of the cylinder, in order to allow the simultaneous tangential emission of a plurality of drops towards the object, the trajectory of each of these drops from the cylinder to the object being direct.
• the means for applying said force may also be capable of varying the time of application and the amplitude of this force so as to vary the quantity of ink contained in each drop emitted and / or the number of drops. emitted and therefore the intensity of the shade obtained on the object.
• FIG. 1 is a schematic view of a particular embodiment of the device which is the subject of the invention, intended for spraying ink,
• FIG. 2 schematically illustrates a cylinder usable in the invention and provided with surface cavities where the ink accumulates
• FIG. 3A schematically illustrates another cylinder usable in the invention and provided with surface cavities forming circular grooves admitting the axis of the cylinder as a common axis
• FIG. 3B schematically illustrates another cylinder usable in the invention
• Figure 4 is a schematic and partial cross-sectional view of another cylinder usable in the invention and provided with surface cavities
• Figure 5 is a schematic and partial cross-sectional view of an alternative embodiment of the cylinder in Figure 4,
• FIG. 6 is a schematic view of another particular embodiment of the device which is the subject of the invention.
• FIG. 7 schematically illustrates a device according to the invention
• FIG. 8 is a schematic and partial cross-section view of a cylinder usable in the invention, and • Figure 9 schematically illustrates a printer comprising devices according to the invention.
• the ink is rotated by a cylinder of suitable diameter, the outer lateral surface of which is impregnated with ink.
• This ink is in equilibrium under the effect of the centrifugal force resulting from the rotation of the cylinder around its axis and from the capillary forces.
• Drops are emitted from the surface of the cylinder by the application, at predetermined times and at one or more points, of a force cooperating with the centrifugal force.
• the size of the drops is controlled by limiting, by various means, the quantity of ink separated from the cylinder.
• an electric field is created locally and a drop of ink is detached by electrostatic attraction, the ink used having a non-zero electrical conductivity.
• a uniform electric field in the opposite direction can be used to oppose the centrifugal force in places where no ink emission is desired.
• This uniform opposite field can be adjusted to variations in the parameters involved in the balance of the ink surface.
• the drops are driven at an initial speed substantially equal to the tangential speed of the cylinder towards the object to be printed, which moves perpendicular to the axis of the cylinder, in synchronization with the emission of the drops.
• the size of the drops is mainly determined by a spatial factor and by a temporal factor.
• the spatial factor notably involves the geometry of the external lateral surface of the cylinder. This surface can be provided with cavities to facilitate the accumulation of ink in certain places, in order to initiate the formation of the drops and to limit their volume. We can also play on local differences in wettability of this surface.
• the temporal factor involves the form and the duration of application of the electric extraction field. This second factor conditions the kinetics of a drop formation until it separates from the cylinder and the first moments of its path in the air.
• One of the advantages of the invention is that the entire height of the cylinder (counted parallel to the axis thereof) can be used to generate drops.
• the printing width is only limited by the technical possibilities of producing the cylinder and the electrodes. It is thus possible to achieve printing widths of the order of a few tens of centimeters or even more.
• the resolution of the device depends on the minimum space necessary on the one hand to form the drops on the surface of the cylinder and on the other hand to juxtapose the electrodes.
• the invention has several intrinsic advantages: simplicity of production, writing over a long distance, variation in the size or number of drops, large printing width.
• Figure 1 is a schematic cross-sectional view of a device according to one invention.
• this device is intended to project drops of ink onto a support to be printed 2.
• the device of FIG. 1 comprises a cylinder 4 whose external lateral surface 6 is impregnated with ink by means not shown.
• This cylinder is driven in a rotational movement along arrow F, around the axis X ⁇ e this cylinder 4, by means not shown.
• the print medium 2 which is for example a strip of paper, moves in translation, by means not shown, along the arrow FI, in a plane parallel to the axis X of the cylinder 4.
• the device of FIG. 1 also comprises means intended to apply an electrostatic force at a point A of the surface 6 impregnated with ink.
• These means for applying the electrostatic force comprise at least one electrode 8 which is in a plane containing the axis X of the cylinder and parallel to the plane of the support to be printed 2, as seen in FIG. 1.
• the means d application of the electrostatic force also comprise means for controlling each electrode 8 referenced 10 which are capable of bringing this electrode 8 to an appropriate electrical potential which cooperates with the centrifugal force resulting from the rotation of the cylinder to extract a drop of ink from the surface 6 when the ink arrives at point A located opposite the electrode 8.
• a drop of ink 12 is then projected towards the support 2 along a path T substantially tangent to the surface 6 of the cylinder whose tangential speed (equal to the pro ⁇ uit of the angular speed of the cylinder by the radius thereof) is sufficiently large for this purpose.
• the tangential speed of the cylinder is determined so that the radial speed initially communicated to the drop 12 is much lower than this tangential speed.
• FIG. 2 is a schematic top view of the cylinder 4 of FIG. 1 showing that this cylinder comprises surface cavities 16 intended to promote the formation of the drops of ink which it is desired to project onto the support 2.
• FIG. 3A schematically illustrates a top view of another cylinder 18 according to the invention, provided with surface cavities 20 also intended to promote the formation of ink drops.
• these cavities 20 are circular surface grooves which all have the same axis, this axis being the axis XI of the cylinder 8.
• the unused ink can be continuously refreshed during its passage through a reservoir (not shown in FIG. 3A).
• the grooves 20 comprise on the one hand enlarged zones 20a so as to promote the accumulation of ink and of control the size of the drops and on the other hand of the thinned areas 20b in order to promote the refreshment of the unused ink.
• Figure 4 is a schematic and partial cross-sectional view of the cylinder 4 of Figure 1 in the vicinity of the area of emission of the ink drops.
• the cylinder comprises a first layer 22 and a second layer 24 which covers the layer 22.
• Layer 22 is electrically conductive.
• the layer 24, which covers the layer 22, can be electrically conductive but it is preferably electrically insulating.
• the wettability of the layer 22 with respect to the ink is greater than the wettability of the layer 24.
• This layer 24 is perforated to define the cavities 16 which are mentioned in the description of FIG. 2 and the bottom of which is then constituted by the layer 22. It can be seen that the ink portions 26 are thus kept in contact with the layer 22 in the cavities 16 arranged in the layer 24.
• the conductive layer 22 is maintained at an electrical potential VO by suitable means, not shown.
• Each electrode 8 is, in turn, brought to an electrical potential VE by means of control 10 when it is desired to project a drop of ink with this electrode 8.
• the potential VE is chosen different from VO.
• a drop 26 is extracted from its cavity by the electric field resulting from the potential difference VE - VO which cooperates with the centrifugal force of the cylinder.
• the drop is then projected substantially tangentially to the surface of the cylinder whose tangential speed is determined for this purpose.
• FIG. 5 schematically illustrates an alternative embodiment of the cylinder shown in FIG. 4.
• the cylinder does not comprise two super layers here as in the case of FIG. 4 but three surface layers respectively referenced 30, 32 and 34.
• Layer 30 is the innermost of the three and this layer 30 is electrically conductive.
• Layer 32 covers this layer 30 and it is made of an electrically insulating material.
• the layer 34 itself covers this layer 32 and it is made of an electrically insulating material whose wettability with respect to the ink is less than that of the layer 32.
• the cavities 16 are formed through this layer 34 and the bottom of these cavities is also formed by the underlying layer 32.
• the layer 30 is brought to the potential VO by suitable means, not shown.
• the ink drops 26 are still formed in the cavities 16. Electric charges are deposited in these ink drops 26 by suitable means not shown in FIG. 5.
• scraper which will be discussed later.
• an electrically conductive scraper is used.
• This scraper is then brought to a potential of the same polarity as VO.
• the drops 26 thus charged are still extracted when they pass under the electrode 8 brought to the potential VE different from VO and ejected substantially tangentially in the direction of the support (not shown in FIG. 5).
• the choice of the form and the duration of application of the electric field generated by the electrode 8 makes it possible to control the separation of the drops and to control the size and / or the number thereof.
• FIG. 6 is a schematic view of another device according to the invention comprising the cylinder 4 of FIG. 2.
• the means for applying the electrostatic force comprise a row of electrodes 8 arranged opposite the cylinder 4 parallel to the axis X thereof.
• the device of FIG. 6 also comprises means 10 for controlling this row of electrodes 8 making it possible to subject these electrodes, independently of one another, to electric potentials making it possible, in cooperation with the centrifugal force of the rotating cylinder, to 'emission of a set of drops following trajectories T1 substantially tangential to the surface of the cylinder 4 and parallel to each other.
• FIG. 7 is a diagrammatic cross-section view of a device according to the invention.
• This device of FIG. 7 also comprises a cylinder of the kind of that of FIG. 1 referenced 4.
• the device in FIG. 7 also includes a motor 42 which rotates a first pinion 44.
• a second pinion 46 driven in rotation by the pinion 44 by means of a belt 48, itself drives the cylinder 4 in rotation about the axis X thereof.
• This device also comprises a frame 50 in which there is a cylindrical space where the cylinder 4 is housed.
• This space constitutes an ink reservoir 52 through which the rotating cylinder 4 passes, which thus becomes charged with ink on the surface.
• a scraper 54 is also provided above this ink tank so as to remove the excess ink on the surface of the cylinder 4.
• an electrically conductive scraper 54 is used which is brought to a potential of the same polarity as VO by appropriate means 56.
• one of the electrodes 8 of the row of electrodes mentioned above which is parallel to the axis X and extends substantially over the entire height of the cylinder (counted parallel to the axis X) .
• an electrode 60 forming a cylinder portion of axis X spaced from the cylinder 4 and facing it and electrically isolated from the row of electrodes 3 and the scraper 54 by dielectric elements 62.
• This electrode 60 is brought to a potential VR by appropriate means 64.
• the potential VR of the electrode 60 is chosen so as to generate an electric field which opposes the centrifugal force.
• This electrode 60 can be used both in the case where the drops are charged (for example by means of a conductive scraper) and in the opposite case.
• the potential VR and the potential to which the scraper 54 is carried (if the drops are to be charged) have the same polarity as VO. •
• this electrode 8 is brought to a potential VE of polarity opposite to VO (and therefore to VR).
• FIG. 8 This is schematically illustrated in Figure 8 where we see the cylinder 4 in cross section.
• This cylinder 4 of FIG. 8 is hollow and provided, on one of its sides, with a removable cover 66 allowing the introduction into this cylinder 4 of an ink cartridge 68 also removable so that it can be replaced.
• the outer envelope of this ink cartridge 68 is constituted by a porous layer 70 allowing the diffusion of the ink 71 towards the outside of the cylinder.
• the side wall of the cylinder 4 is pierced with a multitude of holes 72 allowing the passage of ink.
• FIG. 8 is particularly advantageous when the object to be printed moves horizontally, the axis of the cylinder 4 then being vertical.
• the surface of the ink contained in the cartridge takes substantially the shape of a portion of paraooloid of revolution around the X axis.
• a hot-melt ink can be used.
• another ink tank 74 can be provided, the bottom of which communicates by a pipe 76 with the bottom of the tank 52.
• This pipe allows the ink to be brought into the tank 52 from the tank 74.
• means 78 for heating the ink contained in the tanks 74 and 52 and in the pipe 76 are provided.
• FIG. 9 schematically and partially illustrates a printer using devices conforming to mvent_on, in which the application time and the amplitude ⁇ e of the electrostatic force generated by each electrode 8 are varied, so as to vary either the quantity of ink contained in each drop emitted or the number of drops emitted or both and therefore the intensity of the shade obtained on the support to be printed 2 from each device.
• Three devices 80, 82 and 84 are used which are arranged one after the other and which allow the printing of three-color images on the support 2 which passes in front of these devices, by the superimposition, on this support 2, of three images respectively formed by these devices 80, 82 and 84.
• the present invention is not limited to the use of a force of the electrostatic type.
• the invention can be implemented with liquids other than inks.

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• Ink Jet (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9496621

Family Applications (1)

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• 1996
  • 1996-10-14 FR FR9612491A patent/FR2754471B1/fr not_active Expired - Fee Related
• 1997
  • 1997-10-14 AU AU47097/97A patent/AU4709797A/en not_active Abandoned
  • 1997-10-14 CA CA002268364A patent/CA2268364A1/fr not_active Abandoned
  • 1997-10-14 EP EP97909405A patent/EP0934167A1/de not_active Ceased
  • 1997-10-14 CN CN 97198823 patent/CN1233214A/zh active Pending
  • 1997-10-14 JP JP51807098A patent/JP2001505495A/ja active Pending
  • 1997-10-14 WO PCT/FR1997/001832 patent/WO1998016389A1/fr not_active Application Discontinuation

Non-Patent Citations (1)

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