FR2740728A1 - Ink jet printer with prevention of ink refilling - Google Patents

Abstract

The ink jet printer has a reservoir filled with ink and multiple jets that deliver jets of ink in accordance with the instructions from the printing controller. The level of the ink in the reservoir is monitored, and when it falls below a set level an electrical signal is generated. The electrical signal triggers generation of a surge of current that irreversibly destroys some essential part of the ink jet printing system contained in the ink reservoir. The heating resistances (25) associated with each ink jet are preferred as the parts to be destroyed. Alternatively a fuse supplying the print cartridge can be destroyed.

Description

 The invention relates to an image transfer device, used to transfer an image onto a support, with a cartridge containing an interchangeable and non-refillable ink supply; it as more particularly an improvement making it possible to avoid unauthorized ink refills.

 There are known, for example, ink jet printing devices in which a print head associated with an ink reserve moves opposite a sheet to be printed. The print head and its reservoir move from left to right then from right to left while the sheet of paper scrolls perpendicular to the direction of movement of the head this last process of ejecting the ink during the movement of head to reproduce the information on the paper backing.

 In such a device, the quality of the printing is linked to the value of a certain number of parameters determined by the manufacturer, such as for example the scanning speed of the printing device, the frequency of ejection of the associated ink. at the speed of ejection thereof and the very composition of the ink. The physical and chemical characteristics of this last influence the quantity of ink ejected and consequently on the quality of printing. Ink that does not have the required characteristics can cause clogging of the print head which prevents use and which can in some cases cause ink leaks. Such leaks can cause damage to the printing device; they can in particular cause short-circuits on neighboring electronic cards.

 In addition, the composition of the ink has a decisive influence on the drying time of the ink deposited on the support. If the ink dries more slowly than expected, smears may appear on the reproduced documents. These burrs can be transferred to the media's drive rollers and therefore soil the following sheets. On the contrary, an ink that is too viscous can block the ink ejection holes and therefore prevent any printing.

 For all these reasons, printing devices are proposed, for office printers or fax machines, for example, whose ink tank, generally associated with a print head and movable with it, cannot be recharged. In this context, the print head and the reservoir form an interchangeable cartridge. To avoid the problems mentioned above, it is necessary to prevent unauthorized ink refills.

 The document WO 90/00971 describes an ink tank in which the ink level is monitored by measuring a potential difference noted at the level of the tank. A zero potential difference indicates a sufficient presence of ink. On the other hand, when the ink level drops below a minimum value, the electrical measurement circuit is interrupted and a voltage signal is recorded at the terminals of a resistance. This signal is used to develop a current pulse of sufficient intensity to cause the destruction of a fuse placed in series with the detection line connected to the resistor.

 In this way, the device is irreversibly modified by cutting off the power line for monitoring the ink level. If an unauthorized ink refill is carried out, the voltage signal delivered by the detection line does not return to its initial state (O volt) and the printing device still behaves as if the reservoir were empty, I ' printing continues to be prohibited by the electronic monitoring and control circuits of the printing device. Such a system has a number of drawbacks.

 First, when the reservoir and the print head form an interchangeable cartridge, the price thereof is increased by the elements of the system described above which must be incorporated therein. The price of the printing device as a whole is also increased because it is necessary to provide a pulse generator capable of destroying a fuse placed in the cartridge. It is also necessary to provide a device for measuring the voltage representative of the ink level.

 Finally, the means used are easily circumvented because it suffices to shunt, outside the cartridge, the fuse of the interchangeable cartridge in order to be able to recharge the reservoir thereof indefinitely, at the risk of causing the drawbacks mentioned. above. One of the aims of the invention is to prevent any distribution of ink by a print head when the associated ink tank has been refilled in an unauthorized manner.

 Another object of the invention is to propose an image transfer device with an interchangeable cartridge comprising means for preventing unauthorized refilling of ink and designed in such a way that no cost increase results, and preferably, no modification of the interchangeable cartridge.

 The basic idea of the invention consists in modifying the electrical signals applied to the print head so as to permanently modify the operating characteristics of one or more components of the ink distribution means, for example by destroying them in such a way that the print quality is deteriorated.

 More specifically, the invention relates to an image transfer device on a support, comprising an ink reserve and means for distributing the ink coming from the reserve, controlled by signals representative of images to be transferred, said signals distribution means operating according to characteristic relationships between image representative signals applied to them and an image portion formed by the ink dispensed, so-called "operating characteristic" relationships, characterized in that it comprises means for control suitable for applying to said ink distribution means electrical signals lastingly modifying the operating characteristics of one or more constituent elements of at least one of the distribution means.

 Thanks to these provisions, it is the ink distribution means themselves, and no longer a fuse, which see their operation modified so that the print quality is degraded.

 Preferably, said electrical signals permanently modify operating characteristics.

 Thanks to these provisions, the modification of the operating characteristics is not reversible and no manipulation can restore an element of ink distribution means.

 According to a particular embodiment, the control means are suitable for applying to said ink supply means electrical signals having sufficient energy to destroy one or more constituent elements thereof.

 Thanks to these provisions, the ink distribution means can be totally or partially destroyed to render the print head itself unusable, when an ink refill is carried out.

 According to a particular embodiment, in the image transfer device as briefly explained above, the ink distribution means comprise means for ejecting ink drops comprising a plurality of ejection channels of ink drops and a corresponding number of resistors forming electrothermal converters, installed in said channels, characterized in that said constituent elements capable of being applied a modification of their operation are such resistors.

 The control means are arranged to apply to such resistors current pulses of energy sufficient to destroy them by heating, current pulses of prolonged duration with respect to the duration of the current pulses applied to the same resistors to control the ejection of ink drops in normal operation or of current pulses of greater intensity than that of current pulses applied to the same resistors to control the ejection of ink drops in normal operation.

 Thanks to these provisions, the invention is easily applicable to ink jet or ink bubble printing devices.

 According to a preferred embodiment, in the device according to the invention, said control means are controlled by means for detecting an ink level in the ink reserve, the application of the electrical signals lastingly modifying characteristics of operation of one or more constituent elements of the ink distribution means being controlled when the detection means detect that the ink level of the ink reserve is lower than a predetermined level.

 Thanks to these provisions, the refilling of the ink tank is prevented. In fact, the modification of the operating characteristic is carried out automatically when the ink reserve is empty or practically empty.

 Thanks to the particularly advantageous characteristics of the invention, the means necessary for the implementation of the invention do not imply any modification of the interchangeable cartridge and do not increase the cost of that. In particular, it should be noted that said electrical signals modifying operating characteristics durably and preferably permanently, are applied to the ink distribution means by the same conductors and switching elements which serve to control them in normal operation. Finally, the print head itself being destroyed, it is not possible to make the cartridge operational again using makeshift means such as for example a shunt.

 The invention also relates to an image transfer method consisting in distributing ink on a support via a print head comprising means for distributing ink from a reserve, said means for distribution operating according to characteristic relationships between representative image signals applied thereto and an image portion formed by the ink dispensed, so-called "operating characteristic" relationships; characterized in that the level of ink remaining in the reserve is compared to a predetermined level and in that, if this is lower than said predetermined level, electrical signals are applied to the means of distribution for lasting modification at least one operating characteristic of one or more constituent elements of at least one of the ink distribution means.

 This method has the same advantages as those described above with regard to the brief description of the device according to the invention. These advantages are therefore not recalled here.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of a non-refillable ink cartridge printing device conforming to its principle, given solely by way of example and made with reference to the accompanying drawings, in which:
- Figure 1 is a simplified schematic view of a print head of the ink drop ejection type, to which the invention advantageously applies;
- Figure 2 is a diagram of the electrical part of the ink ejection means, located in the print head;
- Figure 3 is a block diagram of part of the control means of said ink ejection means;
- Figure 4 is a timing diagram illustrating the operation of the control means during printing;
- Figure 5 is a timing diagram comparable to that of Figure 4 illustrating the operation of the control means at the time of destruction of the ink ejection means;
- Figure 6 is a flow diagram of the program residing in a read-only memory of the printing device and making it possible to implement the invention;
- Figure 7 shows a top view of a printer incorporating the device according to the invention, the print head of which comprises piezoelectric crystals; and
- Figure 8 shows in elevation view, a fax machine incorporating the device according to the invention, the printing means of which use a laser source.

 A non-refillable ink cartridge printing device of the type to which the invention applies comprises an ink tank and a printing head 11 constituting the same interchangeable unit commonly called an ink cartridge, mounted movably on a reciprocating device integrated in a printer. In Figure 1, only the print head has been shown.

 There is a junction conduit 12 connected by a filter to said reservoir (not shown) and connected to ink ejection means 13 comprising a plurality of ejection conduits 20 parallel. These latter are arranged on a silicon plate 14 itself supported by a base plate 15 of aluminum. Said conduits are further integrated into a glass structure 16 covering the silicon wafer. The latter comprises the electronic components and connections shown in FIG. 2. The ejection conduits 20 are arranged parallel and regularly spaced in the same plane parallel to that of the silicon wafer. They are connected to the ink tank and terminate in respective ink ejection orifices 21, defined in a front plate 22 facing the sheet of paper to be printed. All the orifices 21 are arranged side by side. coast, and evenly spaced along a line segment.

 Figure 1 is a simplified schematic view in which only six ejection channels have been shown. In fact, the ejection head has 64; it moves perpendicularly to the alignment of the ejecffon channels. Each ejection channel 20 contains a resistor 25 forming an electro-thermal converter. The operation is as follows: for each position of the printhead relative to the sheet of paper, according to the information to be printed, a certain number of resistors is supplied during a given time interval. The energy dissipated in this resistor vaporizes a small amount of ink located in the corresponding ejection channel 20. This vaporization generates the formation of a bubble 26 of ink vapor. A drop of ink is ejected from the corresponding orifice under the effect of the pressure exerted by the bubble. The invention applies particularly but not exclusively to this type of print head.

 The device further comprises means for detecting an ink level in said reservoir.

 For example, one can use a known absence of ink detection such as that described in Japanese patent application No. 126951, relating to a fax printer. According to this known principle, the head of printing is controlled to print a black mark at the bottom of each page and includes detection means with a photocell or the like, capable of detecting the presence or absence of this black mark.

If the mark has been printed, it means that the printing device has had enough ink to print the document including the mark. On the other hand, if this is absent, it means that the ink is missing in the cartridge. The device according to the invention is controlled by a signal read after printing a page and corresponding to the presence or absence of this black mark.

 Referring to FIG. 2, it will be recalled that the print head carries 64 heating resistors 25 forming the electro thermal converters integrated into the ejection channels and 64 diodes 28. Each resistor 25 is in series with a diode 28 and this serial connection forms a branch of a sort of matrix network established between 8 connection points CM1-CM8 and 8 connection points SG1-SG8. In the following text, a connection point CM1-CM8 is called "common connection point" while a connection point SG1-SG8 is called "segment connection point".

 The resistors are connected together in groups of eight and each group of 8 is connected to a common connection point CM1-CM8.

The other pole of each resistor is connected to the anode of an associated diode. The cathodes of these diodes are connected together in groups of 8. Each group is connected to a segment connection point. The branches (25, 28) connected to the same segment connection point belong to the aforementioned different groups of branches, each group corresponding to a particular common connection point. This ensures the supply of each resistor by passing a current between a common connection point
CM1-CM8 and a segment connection point SGl-SG8. FIG. 3 represents the switching and amplification means 30 capable of supplying current pulses to the resistors 25. This block is carried by the printer and not by the interchangeable cartridge. There is a preamplifier 32 with 8 inputs and 8 outputs. The outputs of the preamplifier are connected to respective inputs of an amplifier-switch 34 connected to a current source 36. The outputs of the amplifier-switch are respectively connected to the points CM1-CM8 connection.

Another amplifier-switch 38 has 8 inputs and 8 outputs, each of which is respectively connected to a segment connection point. This amplifier has a common ground connection and makes it possible to connect one of the points SG1-SG8 to ground when a signal is applied to its corresponding input. Thus, a current can be established through a resistance selected in response to the control signals produced by print control means 40 comprising only 8 outputs COM1-COM8 connected to the inputs of the preamplifier 32 and 8 outputs
SEG1-SEG8 connected to the inputs of the amplifier 38. FIG. 4 represents a timing diagram of the control signals produced by the print control means 40 which have just been mentioned.

The COM1-COM8 signals follow each other cyclically so that at a given moment a group of 8 resistors may be crossed by a current. At the same time, the signals SEG1-SEG8 are produced selectively in correspondence with the information to be reproduced. In the example in Figure 4, it is assumed that the information to be reproduced at a given time requires the printing of the 64 points available. Each pulse appearing at a SEG output lasts about half the duration of a pulse applied to a COM output. The impulses
Odd SEGs are generated during the first half of the corresponding COM pulse while even SEG pulses are generated during the second half of the corresponding COM pulse.

 Thus, the resistance 25 accessible between the common connection point CM1 and the segment connection point SG1 can be crossed by a current during the time interval of which 1, the resistance connected between the points CM2 and SG3 can be crossed by a current during the time interval t3-t4, the resistance connected between the points CM1 and SG2 can be traversed by a current during the time interval t-t2, etc.

The control means 40, more particularly here the print control circuit, are controlled by ink detection means associated with the ink tank. If these ink detection means emit a signal representative of a lack of ink, the print control circuit is programmed to modify the control signals delivered to the SEGI outputs.
SEG8 and at the COM1-COM8 outputs. According to a remarkable characteristic of the invention, it is therefore possible, by this simple means not involving any additional connection, to apply to the means for ejecting ink drops current pulses having sufficient energy to destroy one or more constituent elements of these, in this case the resistors 25 themselves.

 By current pulse, we mean here that a current flows in the resistance during a given time interval. Indeed, the signals delivered to the outputs SEG1SEG8 and COM1-COM8 are modified to extend the time during which each resistance is traversed by a current, until it is destroyed by heating. The print control means 40 are therefore arranged and / or programmed to apply to said resistors current pulses of extended duration with respect to the duration of the current pulses applied to the same resistors, in normal operation, to control the ejection of the drops. ink.

 FIG. 5 illustrates the modification of the control signals. We see that the COMI-COM8 signals as well as the SEGI-SEG8 signals extend throughout the duration of a COM1-COM8 cycle, at least. This authorizes the passage of a current simultaneously through 8 resistors and this during the whole time when the corresponding COM control signal is active. This results in a much greater heating than in the case of normal operation which causes a rapid rise in temperature of the resistors. Maintaining the cycles in accordance with FIG. 5 makes it possible to reach a temperature sufficient to destroy the resistances. By way of example, if the signals SEG1 to SEG8 and COMI to COM8 are applied continuously as shown in FIG. 5, the heating resistors 25 are destroyed in about one second.

 The so-called destruction operating mode, illustrated in FIG. 5, is implemented by the printing control means 40 when the level detection means emit a signal representative of a low ink level in said reservoir. This operating mode is controlled by a program written in a read only memory associated with the processor of said control means.

The transition to the so-called destruction operating mode and its unfolding are carried out according to the flowchart of FIG. 6. Periodically the printing device checks whether or not ink remains in the cartridge composed of the head. print and tank. According to the detection mode indicated above, the device prints a black square at the bottom of each sheet for reading thereafter. This verification phase is carried out in step 41. If the device detects a black job, this means that there is still ink remaining and that the printing device is functioning correctly. In this case, the central processing unit of the printer performs the normal conventional tasks of a printer. is positive,
The central unit of the device goes to the next step, known as destruction of the print head. This step 43 consists for the central unit in modifying the control signals SEG1ZEG8 and COM1 to COM8 in accordance with what is shown in FIG. 5. This operating mode is maintained for a predetermined time sufficient to cause the destruction of the resistors by heating of these. Once the destruction operation is complete, the process generates the information necessary for the activation of a light-emitting diode (step 44) to signal the user that he has to change the ink cartridge.

 It appears from the foregoing description that, in the particular embodiment, the cartridge is in no way modified since the print head is destroyed by a simple modification of the duration of the signals which are applied to it in normal operation; The energy necessary for destroying the resistors 25 is therefore supplied by the same conductors which supply them normally. In the example, the value of the current is also not modified. It is also possible to modify the control means external to the cartridge in a simple and inexpensive manner so that they are able to apply to said resistors current pulses of higher intensity than that of the current pulses applied to the same resistors 25 for controlling the ejection of the ink drops. This can be obtained, for example, by increasing, at the time of the so-called destruction operation, the voltage applied via the amplifier-switch 34.

In Figure 7 are shown, in a printer 6 ,:
an ink reserve 1, which contains the ink drawn for printing and which gradually empties during printing, having a mass which decreases progressively between two predetermined values;
- A print head it comprising ink distribution means 13 with piezoelectric crystals 2, operating, thanks to control members not shown, according to known techniques;
- displacement means 3 jointly moving the print head II and the ink reserve 1, and comprising acceleration means 4.According to the normal operating specifications of the printer, the acceleration means are adapted to communicate to the reserve of normal operating accelerations for printing, accelerations whose intensities are below a given threshold. Outside the printing operating range, that is to say beyond this threshold, the accelerations given by the acceleration means are only partially respected, depending on the inertia of the head. printing and ink reserve 1. We choose a commanded acceleration value which is beyond the threshold and for which:
when the ink reserve I is full, the acceleration is weakly transmitted and, the displacement of the reserve is less than that which is commanded.

 when the ink reserve 1 is empty, the acceleration is fully transmitted and the displacement of the reserve is that which has been ordered.

 - Means for detecting the position of the ink reserve 5 provide a signal representative of the position of said reserve.

 The operation of this embodiment of the invention is as follows: the reserve is placed in position opposite the position detection means, the acceleration greater than the threshold described above is controlled and, after at least one such acceleration, stops the engine according to normal operating specifications. The ink reserve changes the less the position the ink reserve is full. A return of the reserve is then commanded in front of the position detection means, according to the normal operating specifications, assuming that the acceleration has been fully respected. The detection means then provide a signal representative of the position of the reserve and therefore of the quantity of ink in the reserve.

 If the position detection means indicate that the reserve has then returned in front of them, it is known that the ink reserve 1 is empty and the final and at least partial destruction of the piezoelectric crystals or of their organ is ordered. control, for example of fuses inserted in their control circuits.

In FIG. 8 are represented, in a facsimile machine 7,
- an ink reserve 1;
- Ink distribution means 13 comprising on the one hand a fixed laser source 8, and on the other hand a photosensitive surface 9. These ink distribution means are known in the field of so-called laser printers. In the present case, the interchangeable and non-rechargeable part consists of the reserve 1 and the photosensitive surface 9.

 The laser beam is adapted, according to known techniques, to scan at least a part of the photosensitive surface 9, during the movement of the latter. As it moves, the photosensitive surface 9 changes its physical state at the places where it is exposed to the laser beam, according to known physical principles, becomes charged with ink, generally called thunder, at the places where its physical state has changed. The photosensitive surface 9 deposits this ink on a sheet of paper on which the photosensitive surface rolls and where this ink is then fixed by heating.

 According to the present invention, the energy applied by the laser source 8 can be sufficient, at a point on the photosensitive surface, for local physical state modifications to be lasting, even irreversible, the photosensitivity of the photosensitive surface thus being modified. , and as a result, the fax machine can no longer function properly since repetitive marks mark the printed sheets.

 The invention is not limited to the embodiments described, or even to the only type of resistance printhead. The principle of the invention is applicable to any printing device using a reservoir and a print head, including other inkjet printing technologies, laser cartridges, color, etc. Likewise, the invention applies to any type of lasting or final modification of the constituent elements of the printhead deteriorating its print quality for example by limiting its operation to a very small quantity of ink dispensed.

Claims (14)

 1. Image transfer device on a support, comprising an ink reserve and means for distributing (13) the ink coming from the reserve, controlled by signals representative of images to be transferred, said means of distribution operating according to characteristic relationships between representative image signals applied to them and an image portion formed by the ink dispensed, so-called "operating characteristic" relationships, characterized in that it comprises control means (40 ) suitable for applying to said ink distribution means electrical signals lastingly modifying the operating characteristics of one or more constituent elements (25) of at least one of the distribution means.  2. Device for transferring an image onto a support according to claim 1, characterized in that the control means (40) are suitable for applying to said ink distribution means electrical signals definitively modifying operating characteristics of one or more constituent elements (25) of at least one of the distribution means.  3. Image transfer device according to claim 2, characterized in that the control means (40) are adapted to apply to said ink distribution means electrical signals having sufficient energy to destroy one or more constituent elements (25) of these.  4. Image transfer device according to one of claims 1 to 3, in which the ink distribution means comprise means for ejecting ink drops (20) comprising a plurality of ejection channels for ink drops (20) and a corresponding number of resistors (25) forming electrothermal converters, installed in said channels, characterized in that said constituent elements capable of being applied a modification of their operation are such resistors (25).  5. An image transfer device according to claim 4, characterized in that the control means (40) are arranged to apply to such resistors (25) pulses of current of energy sufficient to destroy them by heating.  6. Image transfer device according to any one of claims 4 or 5, characterized in that said control means (40) are arranged to apply to said resistors (25) current pulses of extended duration relative to the duration of the current pulses applied to the same resistors to control the ejection of the ink drops in normal operation.  7. Image transfer device according to any one of claims 4 to 6, characterized in that said control means are arranged to apply to said resistors current pulses of greater intensity than that of the applied current pulses at the same resistors to control the ejection of the ink drops in normal operation.  8. Image transfer device according to any one of claims 1 to 7, characterized in that said control means (40) are controlled by means for detecting an ink level of the ink reserve , The application of the electrical signals permanently modifying the operating characteristics of one or more constituent elements of the ink distribution means being controlled when the detection means detect that the ink level of the ink reserve is less than a predetermined level.  9. Image transfer device according to claim 8, characterized in that the ink level detection means consist of acceleration means (4) of the ink reserve (1) and detection means (5) of the position of said reserve after at least one acceleration, the ink reserve changing all the less in position, during a given acceleration, that the ink reserve is full, the detection means providing a signal representative of the position of the reserve and therefore of the quantity of ink in the reserve.  10. Image transfer device according to any one of claims 1 to 3 characterized in that the ink distribution means (13) comprise piezoelectric crystals (2).  11. Image transfer device according to any one of claims 1 to 3 characterized in that the ink distribution means (13) comprise a laser source (8) and a photosensitive surface (9). of the laser being sufficient for at least one point of the photosensitive surface (8), the photosensitivity thereof to be modified.  12. Printer (6) comprising a printing device according to any one of claims 1 to 11.  13. Fax machine (7) comprising a printing device according to any one of claims 1 to 11.  14. Image transfer method consisting in distributing ink on a support by means of a print head comprising means for distributing ink from a reserve, said distribution means operating according to characteristic relationships between representative image signals applied thereto and an image portion formed by the distributed ink, so-called "operating characteristic" relationships; ; characterized in that the ink level remaining in the reserve is compared to a predetermined level and in that, if this is less than said predetermined level, electrical signals are applied to the distribution means in order to modify at least durably an operating characteristic of one or more constituent elements (25) of at least one of the ink distribution means.