Patent Application
20190389214
This application claims priority from French Patent Application No. 1855503 filed on Jun. 21, 2018. The content of this application is incorporated herein by reference in its entirety.
The invention relates to the print heads of printers or continuous ink jet printers, in particular, binary continuous ink jet printers provided with a multi-nozzle drop generator or with a multi-jet generator.
Continuous ink jet printers comprise a print head, which comprises a generator of drops of ink associated with a cavity for forming jets which contains means, most often one or several electrodes, in order to separate the trajectories of drops produced by the generator and direct them to a printing support or towards a gutter for recovering.
A technical problem with this type of head is to be able to recover the fluids, solvent and/or ink, used during the cleaning phases of all or a portion of the inside of the cavity and/or testing the nozzle or nozzles that emit a jet or jets of ink.
Another technical problem is to be able to control the atmosphere of the cavity in order to prevent the ink from drying out during stopping phases of the machine.
Preferably it is also sought to detect the state of correct or incorrect operation of each nozzle and/or of the means for supplying the print head with ink.
The invention first has for object a print head of a continuous binary ink jet printer comprising:
The cavity for the circulation of jets can be delimited by a 1st side wall and a 2nd side wall, both at least partially parallel to a direction of flow of the jets in the cavity.
The print head further comprises:
The inlet slot of the 2nd gutter then comes in the extension of the outlet slot of the cavity.
The 2nd gutter, in the closed position, makes it possible to recover any fluid used during the cleaning phases of all or a portion of the inside of the cavity and/or testing the nozzle or nozzles that emit a jet or jets of ink. There is therefore no need to allow the ink or solvent to exit through the outlet slot and everything that is recovered in the 2nd gutter (ink and/or solvent) is not dissipated in the outside atmosphere and can be recycled.
In the closed state, the 2nd gutter makes it possible to control the atmosphere of the cavity so as to prevent the ink from drying pout during the stopping phases of the machine, for example by leaving in the cavity solvent that has not been sucked which will make it possible to prevent residual ink from drying out.
The outlet slot of the cavity can be made in said outer surface of the cavity, which can be inclined, for example by an angle between 10° and 80° (for example 45° or about 45°), in relation to a jet trajectory produced by the means for producing a plurality of ink jets; the input slot of the 2nd gutter for recovering is then made in a surface, able to bear against said outer inclined surface in which the outlet slot is made. This embodiment with inclined faces bear against each other is favourable to a good sealing of the cavity when the 2nd gutter is in this closed position.
Advantageously, said 1st gutter and/or 2nd gutter for recovering comprises a circuit, or means for, sucking a liquid present in the latter. Said circuit or means can the common to both gutters, which saves components and space; however, they are preferably different, which is particularly useful to avoid flooding of the 2nd gutter (in the closed position), for example when both gutters are receiving liquid.
According to an embodiment, the actuator, or means for, actuating of the 2nd gutter comprise an electric motor and a transmission, or means for, transmitting between this motor and the 2nd gutter. For example, these means for transmitting comprise a transmission axis on which a portion of a spring is wound of which one end is connected to the 2nd gutter.
A print head according to the invention can further comprise a guide, for example at least one lug or bump, or means for, guiding the 2nd gutter against an outer surface of the cavity and/or a guide, for example at least one lug or bump, or means for, guiding the 2nd gutter against at least one inner surface of a cover.
Advantageously, a print head according to the invention further comprises a detector, or detection means, such as conductive means:
A same detectors can perform all 3 detections, for example comprising a conductive element like a plate, and the shape of which makes it possible to perform all 3 detections.
More generally, a print head according to the invention can further comprise a detector, or detecting means, for example conductive means in order to detect the presence of conductive ink forming a contact between these means and another conductive portion of the head. This detector, or these conductive means, can be the detector, or means, that make it possible to carry out a detection without contact of charged drops that pass in the vicinity of the 2nd gutter when the latter is in the open position. The 2nd gutter can therefore comprise a detector, or detection or conductive means, in order to detect the presence of conductive ink forming a contact between said a detector, or detection or conductive means, and another conductive portion of the head.
A print head according to the invention can further comprise a sensor, or means, associated with said detector or detection means, for detecting or counting or measuring charges and/or currents and/or current variations and/or for detecting or measuring voltage variations, detected by said detection means.
The 2nd gutter of a print head according to the invention can comprise a slot or a ring made from a part that is at least partially conductive, with drops exiting from the cavity passing in this slot or this ring when the 2nd gutter is in the open position.
Preferably the slot or the ring can be formed between 2 conductive portions in said at least partially conductive part.
In an embodiment of a print head according to the invention, the latter further comprises:
For example the at least one electrode, or means for sorting drops or segments of one or several of said jets intended for printing drops or segments that are not used for printing, is/are formed in or on the 1st side wall; at least one spraying nozzle can be for example formed or positioned in the 2nd side wall, for projecting at least one cleaning fluid into the cavity, for example at least in the direction of the 1st side wall.
Such a print head can further comprise an actuator, or means, for driving said spraying nozzle in rotation about an axis (x), for example an axis perpendicular to a direction of flow of the jets in the cavity or perpendicular to a direction parallel to the direction of flow of the jets in the cavity and/or parallel to a plane in which a plurality of jets flow and/or parallel to the plane of the nozzle plate for forming jets (or means for producing an ink jet.
The invention also relates to an ink jet printer comprising:
Advantageously, this printer comprises a controller, or means for controlling means for actuating the 2nd gutter for recovering.
The invention also relates to a method of cleaning a print head according to the invention, comprising:
In the case where the print head comprises at least one spraying nozzle, for example in the 2nd side wall, for projecting at least one cleaning fluid, for example a gas, such as air, and/or solvent, into the cavity, for example at least in the direction of the 1st side wall, a method of cleaning the head can comprise:
Embodiments of the invention shall now be described in reference to the accompanying drawings wherein:
In the figures similar or identical technical elements are designated by the same reference numbers.
An example of structure of a print head to which the invention can be applied is explained here below, in liaison with
The head comprises a drop generator 1. This generator comprises a nozzle plate 2 on which are aligned, along an axis X (contained in the plane of the figure), a whole number n of nozzles 4, of which a first 41 and a last nozzle 4n.
The first and last nozzles (41, 4n) are the nozzles that are the farthest apart from each other.
Each nozzle has an axis of emission of a jet parallel to a direction or an axis Z (located in the plane of
In the figure, the nozzle 4x is shown. Each nozzle is in hydraulic communication with a pressurised stimulation chamber. The drop generator comprises as many stimulation chambers as there are nozzles. Each chamber is provided with an actuator, for example a piezoelectric crystal. An example of the design of a stimulation chamber is described in document U.S. Pat. No. 7,192,121.
Downstream of the nozzle plate are means, or sorting block, 6 that make it possible to separate the drops intended for printing from the drops or segments of jets that are not used for printing.
The drops emitted or segments of jets, emitted by a nozzle and intended for printing, follow a trajectory along the axis Z of the nozzle and will strike a printing support 8, after having passed through an outlet slot 17. This slot is open onto the exterior of the cavity and allows for the exiting of the drops of ink intended for printing; it is parallel to the direction X of alignment of the nozzles, the axes of direction Z of the nozzles passing through this slot, which is located on the face opposite the nozzle plate 2. It has a length at least equal to the distance between the first and the last nozzle.
In the rest of this application as well as in the claims, the term “cavity” designates the zone of the space in which the ink circulates between the nozzle plate 2 and the outlet slot 17 of the drops intended for printing or between the nozzle plate and the gutter for recovering. The nozzle plate 2 forms in fact an upper wall of the cavity.
The drops emitted or segments of jets, emitted by a nozzle and not intended for printing, are deviated by the means 6 and are recovered by a gutter for recovering 7 then recycled. The gutter has, in the direction X, a length at least equal to the distance between the first and the last nozzle.
A cross-section view of this structure of a print head is shown in
P0 is used to designate the plane which passes through the nozzle 4x and which is parallel to the plane XZ. This plane is perpendicular to
The upper portion of the cavity is delimited by the wall 2, which also forms, or comprises, the nozzle plate or comprises the nozzles. The lower portion of the cavity is delimited by a lower wall 21, passed through by the slot 17, and by a portion of the gutter 7. Walls 9 and 10 limit the lateral extension, according to the Y axis. It can be noted that the notion of a portion or of “upper” or “lower” wall is to be understood in relation to the flow direction of the jet or jets in the cavity: indeed, the print head can be used to print a substrate arranged under the print head, as shown in
The cavity comprises in addition, on one side of the plane P0, a side wall 9, preferably parallel to the plane P0 and joining with the nozzle plate 2. A wall 10, located on the other side of the plane P0, faces the wall 9. The cavity is therefore delimited, on either side of the plane P0, by these 2 walls 9 and 10. By convention the side of the plane P0 where the wall 10 and the gutter 7 are is called the first side of this plane, the other side (where the wall 9 is), is called the second side.
The wall 10 has ends, in the direction X, which are joined with the nozzle plate 2. In the portion close to the nozzle plate 2 and over a length that is, preferably, slightly greater than the distance between the first 41 and the last nozzle 4n, this wall can comprise a slot 14, that will make it possible to suck the ink that has just been deposited on the nozzle plate or in the vicinity thereof.
At the bottom of this wall 10 is the input slot of the gutter for recovering 7 in order to make it possible to recover the drops which are deviated so that they do not pass through the slot 17.
The gutter can be placed in hydraulic communication with the slot 14, using a duct 13 that opens into the gutter and which is located at the rear of the wall 10 in relation to the plane P0.
On the wall 10, are means 6, which are preferably flush with wall 10, for selecting and for deviating the drops that are not intended for printing. These means mainly comprise an electrode or electrodes. They are intended to be connected to means for supplying voltage, not shown in figure.
Preferably, the distance between the wall 10 and the plane P0, measured in the direction Y, perpendicular to the plane P0, is, starting from the plate 2, first of all constant; this corresponds to a 1st portion 101 of the wall 10, which is substantially parallel to P0.
Then, in a second portion 102, farther from the plate 2 than the 1st portion 101, starting from a point 61 of inclination of the wall 10, the distance between the wall 10 and the plane P0 increases with the separation of the nozzle plate.
This structure allows the wall 10 to be close to the plane P0, and parallel to the latter, in a 1st portion of the cavity located in the vicinity of the nozzles 4x, where the path of the drops is hardly modified, even when the drops located farther downstream on this path are deviated in order to enter into the gutter for recovering 7. This is what is seen in
A lower portion of the wall 10 and a wall 12, located at the rear of the wall 10 in relation to the plane P0, define, by facing a wall 11, a duct, or gutter 7 for evacuating drops that will not be used for printing.
The walls 10 and 12 are, preferably, joined together, with the reference 18 designating the junction line of these two walls 10 and 12; this line is parallel, or substantially parallel, to the direction X. They form an upper wall of the gutter.
The wall 11 forms a lower wall of the gutter. It comprises a 1st portion 111, the most upstream in the direction of circulation of the drops in the duct 7, 70 and a second portion 112, the most downstream.
The possible duct 13 can open into the upper wall 12 and hydraulically connect the gutter for recovery 7 to a duct 141 hydraulically connected to the slot 14.
The reference 28 designates a junction line of the portions 111 and 112 of the wall 11; this line is parallel, or substantially parallel, to the direction X and to the line 18.
The portion 111 the most upstream, at the inlet of the duct 7 of the lower wall 11, ends with an end portion 15, which, advantageously, forms its apex (or top). This is the point of the surface 11 which is the closes to the plane P0.
Preferably, this apex 15 is also part of a wall 16 which is parallel to the plane P0 and which forms one of the walls surrounding or delimiting the outlet slot 17. In other words, the point the farthest upstream of the gutter is in line with the outlet slot 17 of the cavity. This makes it possible to optimise the recovery of the drops: thanks to this configuration, any deviated drop, even slightly, will be recovered by the gutter.
The slot 17 forms an opening of the cavity 5 through which pass the drops intended for printing.
Another wall of the cavity is formed by the wall 21: it is substantially parallel to the plate 2, but the farthest away from the latter in the cavity 5. In other terms, it is located on the side of the outlet slot 17. An end of this wall can form an entry edge of the slot 17, facing the wall 16 already mentioned hereinabove.
A wall 210, substantially perpendicular to the wall 21, delimits, with the wall 16, the outlet slot 17: the drops will circulate between these 2 walls, before exiting from the slot 17 and becoming crushed on the printing support 8.
The reference 211 designates the outer surface of the cavity, into which the outlet of the slot 17 opens.
An example of the operation of this cavity is as follows.
A continuous jet of ink is emitted by the drop generator. The deflection of this jet is carried out or controlled by the electrode or electrodes 6 in order to create, according to a pattern to be printed and the position of the support 8, drops intended or not for printing.
According to an embodiment, segments of ink are generated, which are intended to not be printed, adjacent segments are able to be separated by a drop, which is intended to be printed. This technique is explained in document FR2906755 or U.S. Pat. No. 8,162,450. In such a case, the cavity:
In other embodiments, and in particular in the case of continuous ink jet printers (of which examples are given further on in liaison with
The drops intended for printing are displaced along the axis Z (in the plane P0) and pass through the slot 17.
The drops, or the segments of ink, not intended for printing are deviated from the axis Z (or from the plane P0), and follow a trajectory that leads them to strike the lower wall 11 of the gutter 7.
As the gutter is connected to a source of a vacuum, the ink that struck the wall 11, leaves, with air, the cavity 5 by the gutter.
Moreover, the duct 13 and the slot 14 can maintain a slight vacuum on the nozzle plate 2. This vacuum makes it possible to absorb ink that, via capillarity, is deposited on the nozzle plate 2.
A problem linked with this type of print head is the detection of the good or bad working condition, or of the state of correct or incorrect operation, of the nozzles and/or of the means for supplying the print head with ink.
An example of a structure of print head which can be combined with the invention is shown in
This example includes most of the elements presented hereinabove in liaison with
In the example shown in
In the body of the spraying nozzle 24, a channel 24c for supplying with gas and/or with solvent makes it possible to bring cleaning fluid to the nozzle 20. This channel is interior to the body of the spraying nozzle 24, and it is itself supplied by a side feed channel 28a (
Preferably, the means for supplying 28, 30, 32, made in the print head, comprise one or several channels, for example several channels for introducing air and/or solvent 30, 32; one and/or the other of these channels can for example be closed off by a valve, for example of the plunger type. For example, the channel 30 and the channel 32 can bring different fluids (one able to bring a gas, for example air, and the other solvent): means for closing off, for example a valve, for example also of the plunger type, make it possible to close off the channel 32 when using the fluid that passes through the channel 30, and/or means for closing off make it possible to close off the channel 30 while when using the fluid that passes through the channel 32. According to an embodiment, a common channel 28 is supplied by channels 30, 32. The channel 28 joins, at one of its ends, the channel 28a of the part 48. The outlet orifice of the nozzle 20 is preferably such that the cleaning jet 22 that exits therefrom is divergent: it is projected, in a plane perpendicular to the X axis, by widening from the nozzle 20, the jet is symbolised by broken lines in the cross-section view of
The nozzle makes it possible to project the solvent along a substantially rectangular surface, extended according to the length of the nozzle plate (therefore along the axis x); in other terms, each cross-section, according to a plane perpendicular to the X axis, is identical or substantially identical to the cross-section shown in
The walls of the nozzle 20 are therefore preferably oriented in order to obtain a shape of the jet 22 that is diverging, widening from the outlet of the nozzle 20, in the plane yz (
In
According to an embodiment, at least two of the nozzles 20, 20′, 20″ of
Preferably, all of the nozzles make it possible to reach all the walls of the inside of the cavity; this can depend on the shape of the interior walls of the cavity. The embodiment shown in
Preferably, each one of the nozzles of
The fluid introduced into this system is then sent inside the spraying nozzle 24 (as symbolised by the arrows 24f of
As indicated hereinabove, preferably, the spraying nozzle 24 is rotating about an axis which is, preferably, parallel to the X axis, i.e. substantially perpendicular to a direction of flow of the jets in the cavity (but other orientations of this axis of rotation are possible, for example parallel to said flow direction of the jets and/or parallel to a plane in which a plurality of jets flow and/or parallel to the plane of the nozzle plate for forming jets (or means for producing an ink jet); an actuator, or means, in particular an electric motor, are provided to drive the nozzle in such a movement of rotation; it is therefore possible to carry out a rotation of the spraying nozzle 24 over a certain angle, for example at least 30° or at least 60° or 90°. According to an embodiment, the movement of rotation makes it possible to project a cleaning liquid, successively towards the N nozzles 41-4n for forming jets, then towards the means 6 of deflection, then towards the gutter for recovering 11 (or in a different order). The entire cavity, or a substantial portion of the latter, can then be cleaned. It is also possible to carry out a rotation of the spraying nozzle 24 over an angle greater than 180°, for example up to 360°, so as to also be able to clean the portions of the system arranged behind the spraying nozzle 24 (when the nozzle is turned towards the cavity 5).
The spraying nozzle 24 is inserted into a cavity 24k made in the print head, with a substantially cylindrical shape. If the spraying nozzle can be driven in rotation according to a sufficient angle, the inside of this cavity 24k can be cleaned by the jet coming from the nozzle 20. Means of sealing 52 can be provided between the spraying nozzle 24 and the surface of the cavity 24k in which it is arranged.
A motor 40 is arranged in a cavity 40c made also in the print head. Means of transmission 42 makes it possible to drive in rotation an axis 46, of which one end is inserted into an opening 24o with a substantially cylindrical shape made in the body of the spraying nozzle 24 itself. The axis 46 is also press-fitted into a part 44 present in the cavity 50i (between the cavity 24k and the cavity 40c), preferably with a general cylindrical exterior shape. This part 44 makes it possible to provide the seal with respect to the motor: for this purpose, the outer surface of this part 44 can advantageously be provided with means 50 that make it possible to provide the seal at the interface between its outer surface and the inner surface of the cavity 50i.
The part 44 can be driven in rotation by the axis 46 in the cavity 50i. Preferably, this part 44 is glued or brazed on the axis 46, the gluing or the brazing contributes to the seal of the system.
The axis 46 is enlarged, at its base, by a plate 46p, which is driven in rotation by a reduction box 42 which retransmits the movement imposed by the motor 40.
The movement of the latter is therefore transmitted to the axis 46 by the intermediary of the set 42, 46p, with the part 44 being driven in rotation while still ensuring a seal with the means 50.
The cleaning fluid is injected into the spraying nozzle 24 (more exactly into the cavity 24c) by the end of the latter opposite that located on the side of the means 40, 42, 46 for driving it in rotation. The cavity 24c extends along a portion of the spraying nozzle 24, while the opening 24o extends along another portion of the spraying nozzle 24.
If the device comprises the means of sealing 50, 52, liquid that would escape from the circuit for supplying with cleaning fluid would first be blocked by the means 52 for sealing, then by the means 50 and by the gluing or the brazing of the part 44 on the axis 46.
This duct is arranged in fact in the part 48, which forms both a closure cap of the end of the body of the spraying nozzle 24 as well as a connector between the latter and the means for supplying 28, 30, 32. Means of sealing 49 can be provided between this cap 48 and the cavity 48c in which it is arranged. Here again, these means of sealing 49 makes it possible to obstruct any flow of the cleaning liquid outside of the channels wherein it circulates.
Means can be provided for carrying out a suction of the solvent projected into the cavity.
First of all, according to an embodiment, this suction is carried out by the gutter 7. Possibly, as shall be seen hereinbelow, a 2nd gutter can be provided, which can also contribute to the suction of the cleaning solvent that streams in the cavity. Moreover, solvent can be sucked by a suction slot 14 made at the top of cavity (
Finally, solvent can be sucked by a suction slot 15 made in the wall wherein the spraying nozzle 24 is positioned; this slot is shown in
Means for suction, for example a pump (not shown in the figures) can be specific to each suction channel, but can be common to the various evacuation channels.
The presence of the 3 evacuation routes mentioned hereinabove makes it possible to use the head in any position whatsoever, with the cleaning liquid able to be evacuated by the intermediary of any one of them whatsoever. Indeed, as already indicated hereinabove, the print head can be used as shown in
In order to reinforce the effectiveness of the means of suction, it is possible, during the operations of cleaning the inside of the cavity, to close the slot 17, for example with a plate 17p, shown in
An example of the method of cleaning is as follows:
During each orientation of the nozzle 20, the cleaning liquid can be sent by pulses, for example pulses between 10 ms and 5 s, with each pulse being separated from the following one by a duration that can be about a few seconds, for example between 500 ms and 5 seconds. Possibly, these pulses can be synchronised with solvent ejection pulses by the printing nozzles 4x. Indeed, the latter emit jets which are much more powerful than the jet emitted by the cleaning nozzle 20. It is then possible to carry out, successively: the emitting of a cleaning jet by the nozzle 20, then of jets by the nozzles 4x, then again the emitting of a cleaning jet by the nozzle 20 . . . etc. Furthermore, it is possible, after a projecting of cleaning liquid by the nozzle 20 towards the nozzles 4x, to suck solvent by these same nozzles 4x, which makes it possible to remove the impurities (that can result from the deposition of ink or of particles contained in the ink) which may have entered into the stimulation changers and in the ducts which are upstream of these same nozzles 4x.
The duration of separation of 2 successive pulses of cleaning liquid emitted by the nozzle 20 is preferably chosen in such a way that the mixing of solvent and of ink that is flowing due to the pulse of the preceding cleaning liquid has not yet dried. In other terms, this duration of separation is chosen so that said mixture has already been able to flow from the walls on which the cleaning liquid was projected (thus, the following pulse will not be ineffective) but also so that this mixture is not yet dry. Indeed, the drying can intervene rather quickly after a single pulse, in particular in the case of a solvent of the MEK (methyl-ethyl-ketone) type.
A cavity and a print head were described hereinabove with the presence, in the wall of the cavity, of a movable or fixed spraying nozzle, and provided with one or several nozzles for projecting cleaning fluid.
But the cavity can comprise several spraying nozzles, with each one being one of the types described hereinabove.
For example, the cavity can comprise at least one movable spraying nozzle and at least one fixed spraying nozzle. In particular, at least one fixed spraying nozzle can be positioned in order to direct a cleaning jet towards a specific zone, for example the gutter for recovering.
In the case, disclosed further on, wherein the print head further comprises a movable gutter:
During a stopping phase of the machine, as no nozzle 4x is producing any jet of ink, it is possible to carry out a cleaning, for example by at least one spraying nozzle (fixed or movable) and/or by ejecting solvent by the printing nozzles 4x. The above described aspects, in connection with
A device according to the invention comprises a 1st gutter which is fixed as explained in connection with
An example of an embodiment of the 1st gutter 7 was given hereinabove, in liaison with
It also comprises a 2nd gutter 70 which is mobile in translation with respect to the printing head. It is shown in
As can be seen in
An actuator, or means, can be provided to actuate this 2nd gutter in translation, between a position, referred to as “closed” in which its input slot comes into the extension of the outlet slot 17 of the cavity, and a position, referred to as “open”, of which the outlet slot 17 of the cavity is cleared.
For example, in the closed position, the inlet orifice 71 of the 2nd gutter, mobile, is bearing against the outer surface 211 of the cavity, in such a way that its inlet slot 71 comes in the extension of, or in front of, the outlet slot 17 of the cavity, both slots facing each other (so that a drop or a jet flowing or circulating through the outlet slot 17 then flows through the inlet slot 71 and into the 2nd gutter); preferably, the outer surface and/or the 2nd gutter comprises means for sealing 152 in such a way that the liquid cannot exit via the support zone of the 2nd gutter against the outer surface 211 of the cavity; for example the 2nd gutter comprises one or several seals that bear against this outer surface, in the vicinity of the outlet slot 17.
For example, this second gutter makes it possible to recover, at the start-up of the print head, both the initial solvent then the curtain of ink. It has, preferably, the same characteristics, in particular geometrical, as the main gutter.
The 2nd gutter (or, in the embodiment that has just been described, its second portion 74) is also connected to means for sucking a fluid which is present in this 2nd gutter, for example by the intermediary of a suction channel connected to the 2nd portion 74. The means for sucking of the 2nd gutter and those of the 1st gutter can be connected to the same means of pumping. Preferably, as explained below, they are separated. Possibly, one or several solenoid valves make it possible, or not, to individually activate the operation of each one of these gutters. This second gutter, when it is in the closed position, can also form, like the 1st gutter, a means for sucking cleaning solvent that streams or flows in the cavity; it can therefore come as a supplement of the various channels for recovering already mentioned hereinabove. The solvent can be projected by the nozzles 4x which are usually used for forming the ink jets: temporarily, for example between two printing operations, they inject solvent, instead of ink, into the cavity.
According to an embodiment (
The 2nd gutter can be placed into a movement of translation according to a direction substantially perpendicular to the flow direction z of the jets in the cavity, in one direction, to its closed position, then in the other direction, from its closed position to its open position; for example an electrical motor (not shown on the figures) can be located in the bulk of the material in which the walls of the cavity are made. This motor makes it possible, by the intermediary of means of transmission (also not illustrated), to displace the 2nd gutter to the position in which its inlet orifice 71 comes into the extension of the outlet slot 17 of the cavity (as explained above, so that a drop of a jet flowing or circulating through the outlet slot 17 then flows through the inlet slot 71 and into the 2nd gutter); when it is no longer necessary to maintain the 2nd gutter in the closed position, it is placed into movement in the opposite direction by the same means in order to return to its open position.
Means of return, for example a spring 80 (
Preferably, for reasons of space, the 2nd gutter is arranged, in relation to a plane such as the plane P0 of
Its inlet slot 71 is surrounded by a seal 152 which makes it possible to provide the seal when it comes facing the outlet 17 of the cavity, in the closed position (as in the
As already indicated hereinabove, it is possible to carry out a print head with 2 gutters, one fixed and the other movable, without means for projecting a cleaning jet into the cavity (i.e. without the elements described hereinabove in liaison with
The 2nd gutter can be brought into a closed position:
An example of a method of cleaning that implements a cleaning nozzle 20, according to one of the embodiments described hereinabove in liaison with
This type of cleaning can be carried out regularly and/or in the presence of dirt, and/or during stopping and restarting phases of the printer.
During these operations, one and/or the other gutter can be cleaned using a spraying nozzle (for example the spraying nozzle 24 of
However, when the 2nd gutter 70 is in the closed position and both gutters 7, 70 are receiving drops or liquid, the 2nd gutter 70 can flooded.
For example, at startup, solvent jets are sent to moving gutter 70 (also called maintenance gutter), which is in the closed position. Then, solvent is replaced by ink, still without any deflection. Once all ink jets are collected by moving gutter 70, the print head starts jets deflection and ink jets are captured by static gutter 7 (also called printing gutter). To make suction easier, jets are deflected one by one or by groups of X jets but not simultaneously. Alternatively, for measurements applications, it could be useful to deflect the jets one by one for evaluating their presence.
During this transient phase, both gutters 7, 70 are receiving liquid. This situation is a potential issue if a same means for sucking or a same actuator generating depression (or a same pump) is connected to both gutters 7, 70, exhibiting different pressure drops. Indeed, a first channel (e.g. related to printing gutter 7) can suck 1 jet together with air while second channel (e.g. related to maintenance gutter 70) can suck at the same time all other jets, for example 63 jets, together with air. The suction force will be mainly applied to the channel with only 1 jet (i.e. related to printing gutter 7) and suction force will not be strong enough to collect the other, for example 63, jets in the other channel (i.e. related to maintenance gutter). A negative consequence of this is a flooding of maintenance gutter 70.
To solve this problem, it is possible to use two different means for sucking or two different actuators generating depression (or two different pumps, for example diaphragm pumps), one for each of the channels or for each gutter, and drive and/or control them in a separate manner. Alternatively it is possible to use a twin-head diaphragm pump with appropriate hydraulic control. Thus, each gutter has dedicated suction means, which avoids the flooding problem.
The 2nd gutter can be provided with conductive means in order to detect electrical charges carried by drops or segments of ink jets that it will recover.
Thus, it can be seen in
These means for detecting are therefore active when the gutter is in the closed position and, for example, charges are detected although all of the jets should be deviated towards the 1st gutter, which is fixed.
Furthermore, means can be included to apply a voltage to the drops generator 1 so that drops which are emitted by one or more of the nozzles are charged. Accordingly
Alternatively, or in combination with the conductive means 101 of detection described hereinabove, it is possible to provide means which will make it possible to detect the presence of a jet or of a charged drop or drops, even when the 2nd gutter is in the open position.
Thus, in
Alternatively, and as shown in
With this 2nd detector, which is preferably linked to the 2nd gutter and is therefore mobile with the latter, it is possible, for example, to detect the presence of a jet that exits via the slot 17 although it should be deflected towards the 1st gutter.
Preferably, the conductive means 103 in the form of a slot or ring have a conductive portion 103d, 103g (
Means 103 can be combined with means 101 as illustrated in
In this embodiment the drops can be charged using the means 313 (
Regardless of the embodiment chosen for these conductive means 101a, 103, the latter can be connected, for example via the conductive means 101, to means for detecting, for example means for counting induced charges detected (for example an ammeter). It is thus possible to measure the charge induced by the charges contained in the jet of drops that pass in the vicinity.
Consequently, even in the open position, the 2nd gutter can play the role for a measurement of the jets.
In the present invention, as explained above, means 101, 103 can be implemented, based on conductive means, to:
1. detect jet presence in gutter 70 when it is in closed position (means 101); this measurement can be performed at the beginning of printing operations, before printing on a printing support;
2. and perform a contactless detection of ink presence near gutter 70 when it is in open position (means 103); this measurement can be performed during printing on a printing support, to check the presence of the jets;
In order to perform measurement 1 above, the 2nd gutter being in the closed position, it is possible to collect a current to detect presence of charges in contact with means 101 (which for example comprises a sensor plate as illustrated on
In order to perform measurement 2 above, the 2nd gutter being in the open position, it is possible to collect a current induced by capacitive effect, when charged ink travels inside means 103 (for example sensor ring 103). Said means 103 can be combined with means 101 as can be seen on
Additionally or alternatively, means 101 (for example: a sensor plate) can be implemented to perform a third measurement (measurement 3) in order to detect, for example during printing on a printing support, ink which is deposited inside the print head or inside its cover as explained in EP3415323; such ink deposition can result from projection of ink on any surface inside the print head. An electrical potential, preferably a constant electrical potential, is applied to means 101 potential variations are detected that would correspond to impedance variations. A strong reduction of the potential can be detected, which corresponds to a short circuit between means 101 and another part, for example a grounded part, of the print head. This informs about abnormal presence of ink corresponding to pollution and can generate a default. Thus, the same means 101 can provide different information. As illustrated on
This operating example, with 2nd gutter closed (such as those hereinbelow with 2nd gutter closed), can be carried out just after the start-up of the printer.
In order to check that all of the jets are present, the following operation can be implemented of a device according to the invention, comprising at least means for detecting 101 by contact, the 2nd gutter being in the closed position:
This makes it possible to completely verify the effective presence of each jet and therefore to guarantee the printing quality.
Another operating example of a device according to the invention, comprising at least means for detecting 101 by contact, the 2nd gutter being in the closed position, is the following:
Another operating example of a device according to the invention, comprising at least means for detecting 101a or 103, 103d, 103g by induction, the 2nd gutter being in the open position, is as follows:
This operating can be carried out during the start-up of the stopping of a print head or between 2 printings.
The other operating modes, with 2nd gutter closed, can be carried out just after the start-up.
If, after having carried out a method according to the invention, the incorrect operating state of at least one nozzle is concluded, then it is possible to proceed with a step of maintenance, for example of cleaning the nozzles. If the 2nd gutter is still in the closed state, it is possible to carry out:
When it is concluded that all of the nozzles are in good operating condition, the 2nd gutter is opened and a printing can be carried out.
A method according to the invention, with the detection of charges by conductive means for detection 101 (detection via contact) or 101a, or 103, 103d, 103g (detection by induction), associated with the movable gutter, supposes a charge of the ink drops, contrary to conditions wherein a printing is carried out.
A method according to the invention, with the detection of charges by the conductive means of detection associated with the movable gutter, then optionally cleaning of a nozzle or of the nozzles, is therefore implemented before or after a print. The latter is stopped, then such a method according to the invention is carried out (with the drops being charged) and/or such a method according to the invention is carried out then a printing is carried out (with the drops not being charged).
Regardless of the embodiment of a device or of a method according to the invention, the voltage applies using means 313 is preferably a sinusoidal voltage, for example at 60 kHz.
Alternatively, this can be a voltage of which the time change is in pulses, with a zero mean (
Generally, the application of a zero-mean signal makes it possible to prevent the electrochemical effects in the drops. Another advantage of the application of a voltage in pulses is the presence of detection peaks at a level that is higher than on a “sine” signal in the charge signal detected by the means 101-103 (the amplitude due to the square of the signal is indeed then greater than that of the sine).
Whether the print head is of the type described hereinabove, for example according to one of the
An accelerometer makes it possible in particular to provide information on the orientation of the print head (as already indicated, the latter can be in the position shown in
This information makes it possible to adapt the cleaning strategy according to the orientation of the head by acting:
An accelerometer also makes it possible to detect movements of the print head, and to then implement cleanings that are more frequent than when no movement is detected.
Finally, such an accelerometer allows for the detection of high vibrations and/or accelerations, that can explain printing quality problems.
In the case of means such as the means for closing 17p (
The second gutter according to the invention and possibly the means for cleaning the inside of a cavity, using at least one nozzle 20 arranged inside the latter were described hereinabove in the case of a binary continuous ink jet printer.
However, one and/or the other of these means can be implemented in the framework of a continuous ink jet printer (CU).
Such a print head can possibly comprise at least one device for detecting the directivity of the trajectories of the drops and/or at least one electrostatic sensor, such as described in document WO 2011/12641.
The generator 201 comprises in addition means for stimulation of the ink, for example a piezoelectric actuator.
It can be seen, according to
The charging electrode or electrodes 230 and the deviation electrode or electrodes 260 are fixed to, or arranged against, the wall 111.
The left portion of
It can be seen that the device already described hereinabove, in particular with the use of one or several cleaning nozzles, is entirely compatible with a print head architecture of the CIJ type. Furthermore, if there is at least one spraying nozzle inside the cavity, the jet thus projected with the spraying nozzle makes it possible in effect to clean the portions of the head which are arranged against the wall 111.
The various aspects already described hereinabove and relating to the method or methods of cleaning and/or relating to the methods for detecting the working conditions of a printing head according to the invention can be applied to the print head structure of the CIJ type, such as the one of
The fixed gutter 270 of a print head of the CIJ type, such as the one of
It is thus possible, for example, to detect the presence of a deviated jet although it should not be and be sent to the fixed gutter 270.
These conductive means 103 are for example in the form of a slot or ring and have a conductive portion 103d, 103g (
The fixed gutter 270 of a CIJ print head, even if the latter is not provided with means forming a cleaning device, including the spraying nozzle 24, the nozzle 20, the jet 22 . . . etc., can be provided with these means 103 of detection. This realisation is shown in
A device according to the invention is supplied with ink by a reservoir of ink not shown in the figures. Various means of fluidic connection can be implemented to connect this reservoir to a print head according to the invention, and in order to recover the ink that comes from the gutter for recovering. An example of a complete circuit is described in U.S. Pat. No. 7,192,121 and can be used in combination with this invention.
Regardless of the embodiment considered, the instructions, in order to activate the means 41-4n for producing ink jets and the means for pumping the gutter, and/or for controlling a cleaning in the cavity and/or for controlling the displacement of the movable gutter 70, are sent by the means for controlling (also called “controller”). It is also these instructions that will make it possible to circulate the ink under pressure in the direction of the means 41-4n, then to generate the jets according to patterns to be printed on a support 8. These means for controlling are for example carried out in the form of an electric or electronic circuit or a processor or a microprocessor, programmed to implement a method according to the invention.
It is this controller that controls the means 41-4n for producing one or several jets of ink and/or of solvent, and/or the means for pumping of the printer, and in particular of the gutter, and/or the cleaning spraying nozzle or nozzles 24 of the cavity (in particular their orientation) and/or the opening and the closing of valves on the path of the various fluids (ink, solvent, gas).
This controller, or these means for controlling, can also memorise data, and possibly process it, for example:
This controller can also receive the data from an accelerometer and control the cleaning and/or the suction of cleaning solvent according to the orientation of the print head.
A door not shown makes it possible to install the print head facing a printing support 8, which is displaced according to a direction materialised by an arrow. This direction can be perpendicular to an axis of alignment of the nozzles. For certain applications, the angle between the direction of the displacement of the printing support and the direction of alignment of the nozzles can differ from 90°, it can be for example between 10° and 90°, in order to increase the resolution obtained.
The drop generator comprises nozzles and a cavity of the type according to one of the embodiments described hereinabove.
The invention is particularly interesting in applications where the flow rate of air or of gas, in the cavity, is substantial, because a substantial flow rate of air generates a risk that is all the more so high of allowing solvent to escape.
For example, the flow rate can be about several hundred l/h, for example between 50 l/h or 100 l/h and 500 l/h, for example about 300 l/h. These values are applied in particular in the case of a nozzle plate of 64 nozzles, but the invention also applies in the case of a nozzle plate with a lower number of nozzles, for example 32, or in the case of a nozzle plate with a higher number of nozzles, for example 128. The speed of the jets can be between 5 m/s and 20 m/s, for example it is about 15 m/s.
An example of fluidic circuit 400 of a printer to which the invention can be applied is shown in
To this circuit 400 are associated a removable ink cartridge 130 and a cartridge 140 of solvent, also removable.
The reference 410 designates the main reservoir, which makes it possible to receive a mixture of solvent and of ink.
The reference 110 designates the set of means that make it possible to sample, and possibly store, solvent using a cartridge 140 of solvent and to provide solvent thus sampled to other portions of the printer, whether it entails supplying the main reservoir 410 with solvent, or cleaning or maintaining one or several of the other portions of the machine.
The reference 310 designates the set of means that make it possible to sample ink from an ink cartridge 130 and to provide the ink thus sampled to supply the main reservoir 410. As can be seen in this figure, according to the embodiment shown here, the sending, to the main reservoir 410 and using the means 110, of solvent, passes through these same means 310.
At the outlet of the reservoir 410, a set of means, globally designated by the reference 220, makes it possible to pressurise the ink sampled from the main reservoir, and to send it towards the print head 1. According to an embodiment, shown here by the arrow 250, it is also possible, by the means 220, to send the ink towards the means 310, then again towards the reservoir 410, which allows for a recirculation of the ink inside the circuit. This circuit 220 also makes it possible to drain the reservoir in the cartridge 130 as well as to clean the connections of the cartridge 130.
The system shown in this figure also comprises means 500 for recovering fluids (ink and/or solvent) that comes back from the print head, more exactly from the gutter 7 of the print head or from the rinsing circuit of the head. These means 500 are therefore arranged downstream of the umbilical cord 203 (in relation to the flow direction of the fluids that come back from the print head).
As can be seen in
The means 110 can comprise at least 3 parallel supplies with solvent, one towards the head 1, the 2nd towards the means 500 and the 3rd towards the means 310.
Each one of the means described hereinabove is provided with means, such as valves, preferably solenoid valves, that make it possible to orient the fluid concerned towards the chosen destination. Thus, using the means 110, it is possible to send solvent exclusively towards the head 1, or towards the means 500 or towards the means 310.
Each one of the means 500, 110, 210, 310 described hereinabove can be provided with a pump that makes it possible to treat the fluid concerned (respectively: 1st pump, 2nd pump, 3rd pump, 4th pump). These various pumps provide different functions (those of their respective means) and are therefore different from one another, although these different pumps can be of the same type or of similar types (in other words: none of these pumps provides 2 of these functions).
In particular, the means 500 comprise a pump (1st pump) that makes it possible to pump the fluid, recovered, as explained hereinabove, from the print head, and to send it to the main reservoir 410. This pump is dedicated to the recovery of fluid coming from the print head and is physically different from the 4th pump of the means 310 dedicated to the transfer of ink or of the 3rd pump of the means 210 dedicated to the pressurising of the ink at the outlet of the reservoir 410.
The means 110 comprise a pump (the 2nd pump) that makes it possible to pump solvent and to send it towards the means 500 and/or the means 310 and/or towards the print head 1.
Such a circuit 400 is controlled by the means for controlling described hereinabove, these means are generally contained in the console 300 (
| Number | Date | Country | Kind |
|---|---|---|---|
| 1855503 | Jun 2018 | FR | national |
