EP0013296A2 - Multiple speed ink jet printer - Google Patents

Abstract

Multi-speed inkjet printer. An increase in printing speed is obtained by suppressing the printing of a column of dots out of two, by suppressing the printing of every second point in a column or by a combination of the two.

Description

Technical area

The present invention relates to an inkjet printer capable of operating at different speeds, with concomitant modification of the resolution of the characters.

State of the art

The IBM 6640 inkjet printer uses the principles described in the U.S. patent. No. 3,596,275. In this machine, a continuous jet of pressurized ink from a nozzle is disturbed and splits into droplets at a predetermined distance from the nozzle. These droplets receive a charge which is applied to them by a charging electrode and then pass between two deflection electrodes to which a high voltage is applied, the value of the charge thus applied to the ink droplets determining their vertical deviation with a view to formation. of characters or other symbols on paper or other similar support placed in the immediate vicinity of the deflection electrodes. If no character or symbol is to be formed on the support, the droplets receive no charge, or receive only a minimal charge; they are therefore not deflected when they pass between the deflection electrodes and are intercepted by a gutter, from where they are brought back to their starting point for reuse.

It appears from the above that the vertical deflection of the droplets makes it possible to form or trace a column of ink stains or dots on the plane of the paper. Each of the droplets of a given column receives a slightly greater charge than the droplet which precedes it, so that the column is formed, in the example cited, from bottom to top. The characters are therefore formed, in a given matrix, by means of a series of columns of ink stains. In principle, the various elements of the print head are arranged on a mobile carriage which carries out a predetermined path along the paper so as to allow the printing on the latter of characters or other symbols.

The IBM 6640 printer has a resolution of characters which makes it possible to obtain a print quality practically equal to that of a conventional typewriter, this resolution being of 94.5 pixels (hereinafter called "PELS"") / cm. In the case of an inkjet printer, a peel is defined as being a point formed on the sheet of paper or other support by an ink droplet. For example, in the case of a resolution of 94.5 pels / cm, of a character printing frame with a height of 4.23 mm (height of the character matrix), and a printing carried out in steps of ten (i.e. ten characters per inch or 3.94 characters per cm), you can form a matrix with a width of 94.5 / 3.94 = 24 pels and a height of 94.5x4.23mm = 40 pels. In this respect, in the IBM 6640 printer, the tolerance relating to the positioning of the peels is only _± 0.033mm, however the tolerance relating to the height and width of the characters is + 0.076mm, which is necessary. to obtain the required print quality. The height of the matrix requires a maximum deflection of the droplets of 0.51cm since it takes about 0.09cm to prevent them from being intercepted by the gutter.

The printing speed of the IBM 6640 is around 90 characters per second and the character resolution is close to that obtained with a classic typewriter of excellent quality. However, it often happens that such a high resolution is not essential, especially if the document that is printed is for internal use or, for example, an advertising circular, an address list or any other document of the same type. .

Currently in the prior art there are two US patents which are analogous to the present invention. The first of these two patents, No. 3,878,517, relates to an ink-jet printer of the type in which the magnitude of the charge is controlled and the printing speed of which is either high or low, the control circuit located in the character generator generating a signal which controls the drive speed provided by a servo motor connected to the carriage. On the other hand, although the frequency of ink droplet formation remains constant, the control circuit, depending on whether the printer operates at high speed or at low speed, transmits a control signal to an adjustable frequency divider which changes the ratio of the number of droplets receiving a video signal to the total number of droplets formed, so as to compensate for variations in speed. In the printer of the present invention, the ratio of the number of charged droplets to the number of uncharged droplets remains essentially the same whether the machine is operating in coarse printing modes or in fine print mode. There is no change in the frequency of appearance of the number of charged droplets or in the ratio resulting from the number of charged droplets to the total number of droplets formed.

The second patent, No. 3,938,641, describes a sequential dot matrix printer provided with a step-by-step drive. In this latter printer, the printing speed of the dot columns is controlled by modifying the printing speed signal. In either of the two operating modes described above, the frequency is not subject to any variation to modify the carriage speed or the printing speed.

Statement of the invention

One of the objects of the present invention is therefore to provide an ink projection printer making it possible to obtain a variable character resolution with a corresponding increase (or, if necessary, a decrease) in the printing speed.

In a first embodiment of the present invention, the printer operates in a first mode known as coarse printing (compared to the fine or high quality printing previously mentioned), in which the signal for the start of column printing is deleted regularly or periodically, so that if you delete, for example, one of these signals out of two, the machine only prints a column of dots out of two also, which makes it possible to approximately double the carriage speed. In this respect, one can avoid having to modify the pre angle determined deflection electrodes, if the inclination of these electrodes is undesirable in the case where the machine operates in the coarse printing mode, by implementing the method described in French patent application No. 7833644 filed on November 23 1978 by the plaintiff which allows the inclination of the deflection electrodes to be automatically modified as a function of the speed of movement of the carriage. In a second embodiment of the present invention, the printer operates in a second coarse printing mode, in which only one dot out of two is printed in each column, which has the effect of deleting a row of dots on of them. However, in the latter case, it is necessary to correct the aerodynamic effects specific to the droplets and to compensate for the interactions between the charged droplets. Thus, in the first embodiment of the invention, in which only one column of dots is printed out of two, although the width and the height of the frame in which each character is printed do not vary, the maximum number of pels in each row, in the case of a printing carried out, for example, in the step of ten, is twelve (24/2), however - the maximum number of pels that each column contains remains forty. In the second embodiment of the invention, in which only one row of pels is printed out of two, the maximum number of pels in each row of said frame is 24 (in the case, as before, of a printing in steps of ten), but only 20 pels in each column, this achievement, like the first, to accelerate the speed of movement of the carriage, while maintaining the predetermined ink flow. On the other hand, it is easy to combine the removal of one column out of two with the removal of a row of points out of two in order to increase the speed of the carriage, so that it is equal, for example, to four times that obtained in the case where the printer operates in the so-called fine printing mode. In this regard, it should be noted that only minor modifications to the existing IBM 6640 printer and its electronic circuits are necessary for the machine to be able to operate at least in the coarse printing mode in which only one column out of two is printed.

It will also be noted that, in the case of the IBM 6640 printer, the average diameter of the ink droplets is 0.06 mm.

In the fine print mode, the dots or pels of the print matrix are separated by a center-to-center distance of 0.1mm. However, since the ink tends to spread on the printing medium (which is generally constituted by paper), there is an increase in the diameter of the dots or of the peels, the value of which then becomes approximately equal to 0, 15mm, which results in an overlap of dots or peels on the paper. In this context, in the first coarse printing mode of the present invention, which is the preferred mode, the dots are separated horizontally by a distance of 0.2mm center-to-center, and by a vertical distance of 0.1mm center-to-center; in the second coarse printing mode (deleting every other row of dots), the dots are separated horizontally by a center-to-center distance of 0.1 mm and vertically by a center-to-center distance of 0, 2mm. In the case where the two modes are combined, the points are obviously separated, vertically and horizontally by a center-to-center distance of 0.2mm. In summary, the resolution is sacrificed in favor of an increase corresponding to the speed, without however the predetermined ink flow rate being modified.

Other objects, characteristics and advantages of the present invention will emerge more clearly from the following description, made with reference to the drawings appended to this text, which represent a preferred embodiment thereof.

• La Figure 1 représente schématiquement une imprimante à projection d'encre incorporant la présente invention.
• La Figure 2 représente un agrandissement d'un caractère imprimé au moyen de la machine de la Figure 1 fonctionnant dans le mode d'impression fine et utilisant une première résolution, des signaux de réseau appropriés et un signal de début d'impression de colonne étant représentés sous ledit caractère.
• La Figure 3 est analogue à la Figure 2 et montre le même caractère formé lorsque l'imprimante fonctionne dans le premier mode d'impression grossière en utilisant une seconde résolution.
• La Figure 4 est analogue à la Figure 3, mais le caractère représenté est celui obtenu lorsque l'imprimante fonctionne dans le deuxième mode d'impression grossière.
• La Figure 5 représente schématiquement les circuits électroniques d'une imprimante à projection d'encre incorporant les dispositifs de la présente invention.
• La Figure 6 est un schéma logique illustrant une première logique afférente au premier mode d'impression grossière.
• La Figure 7 représente les circuits afférents au positionnement des gouttelettes d'encre ainsi qu'un schéma logique afférent à la logique du premier mode d'impression grossière.
• La Figure 8 représente schématiquement la mémoire de données de correction utilisée dans le deuxième mode d'impression grossière.
• La Figure 9 est un diagramme des temps relatifs aux différents signaux représentés de façon mnémonique sur les Figures 6 et 7, aux fins d'un fonctionnement correct de l'imprimante dans le premier mode d'impression grossière (qui est le mode de fonctionnement préféré).

Brief description of the Figures

• Figure 1 schematically shows an ink jet printer incorporating the present invention.
• Figure 2 shows an enlargement of a character printed using the machine of Figure 1 operating in the fine print mode and using a first resolution, appropriate network signals and a column start print signal being represented under said character.
• Figure 3 is similar to Figure 2 and shows the same character formed when the printer operates in the first coarse printing mode using a second resolution.
• Figure 4 is similar to Figure 3, but the character shown is that obtained when the printer is operating in the second coarse printing mode.
• Figure 5 schematically shows the electronic circuits of an inkjet printer incorporating the devices of the present invention.
• Figure 6 is a logic diagram illustrating a first logic relating to the first printing mode coarse.
• Figure 7 shows the circuits relating to the positioning of the ink droplets as well as a logic diagram relating to the logic of the first coarse printing mode.
• Figure 8 schematically shows the correction data memory used in the second coarse printing mode.
• Figure 9 is a time diagram relating to the various signals represented in mnemonic form in Figures 6 and 7, for the purposes of correct operation of the printer in the first coarse printing mode (which is the preferred operating mode ).

Description of the invention

In the ink-jet printer schematically represented in FIG. 1, ink 1 maintained at a determined pressure is expelled from a nozzle 2a, by means, for example, of a droplet generator 2, under the form of a jet. In order to prevent the latter from dividing into droplets having quasi-random dimensions and spacing, the ink contained in the nozzle cavity is vibrated at a fixed ultrasonic frequency by means, for example, of d a circuit 3 which excites a piezoelectric crystal placed inside the droplet generator 2. The pressure waves thus generated cause the jet 1 to be divided into a series of droplets having uniform dimensions and spacing, at a distance well defined nozzle 2a. A typical droplet generator is described in the publication "IBM Technical Disclosure Bulletin", Vol. 21, No. 5, October 1978, pages 1949-1950.

Each droplet thus formed receives an electric charge of a predetermined size when a voltage is applied to a charging electrode 4 which surrounds the point where the ink jet divides into droplets. The droplet retains this charge for the duration of its flight to a support 5 consisting, for example, of a sheet of paper. The different droplets pass through an electro-static field obtained by applying a fixed high voltage across the terminals of a pair of deflection plates 5 arranged horizontally. Each droplet receiving a separate charge, it can be deflected vertically by a desired distance. In the case of the IBM 6640 printer, the droplets are deflected vertically from bottom to top, so as to form on the sheet of paper a column entirely or partially composed of dots or peels. The droplets which are not used for the purpose of printing a character and which therefore must not appear on the paper receive no charge and are not deflected. These latter droplets are intercepted by a gutter 6 and brought back to the droplet generator 2 for a new use, via an ink tank 6a, a filter 6b, an ink supply 6c and a pump 6d, which continuously supplies ink to the generator 2. A typical ink recirculation system is described in US Pat. No. 3,929,071. On the other hand, since the height at which a charged ink droplet is deflected and projected onto the sheet of paper 5a is a direct function of the time interval during which it remains between the deflection plates 5 (the longer this time interval, the higher the droplet is projected), the speed of droplets or inkjet must be ordered accurately. US Patent No. 3,787,882 describes several servo systems for controlling this speed by detecting the speed and then controlling the pump so as to obtain the desired pressure in the droplet generator 2. Another method for determining the speed of the droplets is described in French patent application No. 7826224 filed on September 8, 1978 by the applicant.

The droplet generator 2, the charging electrode 4, the deflection plates 5 and the gutter 6 are mounted on a carriage 7 which is driven horizontally and follows a predetermined path which brings it towards or away from the plane of the paper of the Figure 1, at a relatively constant speed during the printing operation. The droplets are therefore deposited on the paper at suitable locations inside a character frame or a frame so as to form the desired character or symbol. The carriage 7 is coupled to a drive device 7a, comprising for example a motor operating in direct current, which is excited by signals delivered, for example, by an excitation device 7b (in the preferred embodiment) under control electronic circuits 8 of the system.

When the printer is operating, ie in the continuous printing mode, it is essential that means are provided to indicate the position of the carriage at any given time so that the start of each column printing can be determined and that the charging electrode can receive the correct data or the appropriate voltage level to deflect the ink droplets in the correct way quise. On the other hand, means must be provided to determine the direction in which the carriage moves. In this regard, the printer comprises a detector 9 comprising a matrix 9a which emits and which receives and a concave mirror 9b arranged on the carriage on either side of a fixed network 9c of markers (mounted on the chassis of the machine), which network makes it possible, in conjunction with the matrix and the mirror, to generate signals which are transmitted to the electronic circuits of the system, both for applying a voltage to the charging electrode and for controlling the drive device 7b and, therefore, the device 7a connected to the carriage 7. The detection method and device used are described in more detail in European patent application No. 79 101 561 filed on May 22, 1979 by the applicant. The detection circuits used are also described in European patent application No. 79 101 719 filed on June 1, 1979 by the applicant. The network 9c consists of two parts offset by 90 ° with respect to each other and includes opaque and transparent marks. The array 9a includes a pair of light sources and a pair of detectors; the light which crosses the network is reflected by the mirror 9b and strikes the detectors which, by means of the circuits which are associated with them, generate alternating signals, such as those represented under the letter "B" in Figures 2, 3 and 4 (for the sake of clarity, the signals generated by the two detectors are respectively referenced "Det. A" and "Det. B"). The output of one of the two detectors can be used in conjunction with a counter to count the transitions (opaque to transparent) and, the network comprising a predetermined number of marks, to indicate with precision the position occupied by the carriage 7 the along its course. In the example shown on the In Figures 2, 3 and 4, the output of detector B is used to indicate the position of the carriage and provides the related information at the start of printing of each column.

The pulses indicated in FIGS. 2, 3 and 4 and designated SOS indicate the start of printing of a column by means of a series of droplets. For example, if the network associated with detector B has 23 divisions per cm, and if the resolution is 94.5 pels / cm, each of the divisions of the network must be divided by four to obtain the resolution required to form a character such as the letter "B" shown in Figure 2. (The output of the second detector, such as detector A, is used for comparison with the output of detector B to inform electronic circuits of the direction in which moves the cart).

According to the present invention, the resolution of a character can be modified so that it becomes that of, for example, the character represented in FIG. 3, this latter resolution being defined below as corresponding to the first printing mode. coarse. This result is obtained, in the case of character "B" in FIG. 3, by increasing the speed of movement of the carriage and by simultaneously suppressing one of the column printing start signal (or SOS signal) out of two, this signal being used to apply a voltage to the charging electrode 4. The second coarse printing mode can be obtained by printing only one row of dots out of two when plotting a column. In this regard, account should be taken of the fact that normal aerodynamic repulsions should be corrected and the interactions between charged droplets should be compensated for, example by means of a modified correction memory. The first and second coarse printing modes can also be combined, in which case the resolution of the printed character is reduced, such as the character "B" shown in Figure 4. In the latter case, an increase can be obtained of the printing speed, an increase which can be equal to four times that used to print the character "B" shown in Figure 2 and which corresponds to the fine printing mode.

FIG. 5 shows the electronic circuits 8 of the printer incorporating the present invention. The circuits schematically represented in FIG. 5 are essentially the same as those used in the IBM 6640 printer, with the exception of block 30, representing the logic relating to the coarse printing mode, and some modifications made to block 19, relative to the positioning of the ink droplets, blocks which are respectively described below with regard to FIG. 6 and of FIG. 7.

In FIG. 5, a microprocessor or other similar device 10 comprising other input devices 10a, such as a typewriter, a disk drive device, etc., functions as the main system vis-à-vis screw of the inkjet printer schematically shown in Figure 5. An input / output channel consisting of 14 lines is connected to the printer, namely eight (in the example shown) data lines, four control lines, an interrupt line and a line for transmitting signals from a main clock. The printer interface 11 provides, in a conventional manner, the transfer, logic and amplifier functions and the signals provided by the main clock are applied to the system clock 12, in which frequency division circuits divide the frequency received from the main clock, which is converted into four clock frequencies, T1 to T4, shown in Figure 9. The signals from the input / output channel can be amplified and stored appropriately so that serial instructions can be received from microprocessor 10.

The data received by the electronic circuits of the printer and relating to the printing instructions consist of three bytes, as explained below. As an example, if we assume that the printing line has a maximum length of 35.5cm and has 23.6 divisions per cm, as previously indicated with respect to the network 9c of the Figure 1, a total of 840 divisions, a single byte of data will give only 2 ⁸ or 256 bits, which is insufficient. Since it takes at least 840 bits to give the position code to the printer, in the case of a 35.5cm print line, and since ₂ ¹⁰ = ₁₀₂₄ bits is the value closest to the code effective position, two bytes are necessary for the position signals transmitted to the printer by the microprocessor. On the other hand, in the system actually used, an additional byte is necessary to identify the signal defining the character to be printed, or the function to be executed, and the interface 11 therefore includes a buffer memory associated with these three bytes coming from the microprocessor. . In the IBM 6640 printer, the first byte of a printing instruction is an address which is applied, via the interface 11, to the character generator 13, defining the character to be printed. (In assuming it is recognized as a print instruction). The generator 13 transmits the full or partial address of this character, via the common line "address", to the memory 14, and receives from the latter the data relating to said character via common lines of data. 15. The data thus extracted from memory 14 relate to the printing of a single column of dots forming part of this character.

The second and third bytes of the signal received from the microprocessor are applied to a logic circuit 16 called mechanism control, to inform the latter of the position of the first column of dots of the character to be printed.

In the case of an instruction relating to the execution of a function, the first byte is applied via the interface 11 to the logic circuit 16 in order to be decoded and to trigger the execution of the function whose it's about; for example, bit configuration 11010101 is decoded as representing a tabulation function and configuration 10110101 is decoded as defining a backspace function. The second and third multiples can also be applied to logic circuit 16 to perform appropriate actions when the carriage occupies the position specified by these bytes; for example, if a tabulation instruction has been decoded, the second and third bytes specify the point where the carriage should stop after the tabulation function is executed.

The functional block 16 can be used to perform many functions. For example: (1) control and synchronize the operation of circuit 18 of the request French Patent No. 7,828,298 filed September 26, 1978 by the Applicant, which circuit performs a periodic check of the series of ink droplets to determine if the height at which they are deflected is within prescribed tolerance limits; (2) serve as an instruction decoder for the synchronization and servo operations of an ink pump such as that described in US Patent No. 3,787,882; (3) controlling the operation of the drive device 7a of the carriage and consequently the horizontal speed (in the present example) of the carriage 7 in the case in particular of the use of the excitation device 7b; (4) serve as a motor drive control device and receive the network position signals emanating, for example, from the detector 9 shown in FIG. 1 (cf. European patent applications No. 79 101 561 and 79 101 The variable speed drive device can obviously take the form described in the publication entitled "IBM Technical Disclosure Bulletin", Vol. 20, No. 10, March 1978, pages 3993-3994, but it is preferable that it is of the type described in US patent application No. 954,374 indicated above.

When the data extracted from memory 14 and relating to the printing of a column of dots has been loaded into the shift register 39 (see Figure 7) of the character generator, a signal is transmitted via the line control common 13a to circuit 16, which then puts the associated mechanism in a position in which it is ready to proceed with printing, that is to say in the printing position. When the data thus extracted is in the character generator-13 and a print signal has been applied to the circuit 16, a signal indicating that the printing of a column can begin (or PIC signal) is transmitted via the common line 13b to the logic circuits 19 for positioning the ink droplets. A second signal called start of column printing (MCSOS) emanating from the circuit 16 and coinciding with the movement of the carriage to a predetermined point of the network 9c (Figure 1), this displacement being carried out in accordance with the data contained in the second and the third byte of the signal initially received from the microprocessor 10, causes the generation by the circuits 19 of an output which is applied via a common line 19a to a digital / analog converter 20, so that a charging voltage is applied to the charging electrode 4 (Figure 1) of the printer, in order to load the various ink droplets so that a column to be printed _"in accordance with data retrieved from the memory 14 and transmitted to the character generator 13.

The generator 13 continues to receive data relating to the printing of a column of the character designated by the first byte and to transmit via the common line 13a a print signal to the circuit 16 so that the cycle printing of this character continues until a so-called end of character printing signal is transmitted by the generator 13 to the circuit 16 via the line 13a. Furthermore, the circuits 19 generate another signal which opposes the transmission of the signals until the said circuits are ready to accept from the character generator 13 new data which will be used to apply the required voltages to the electrode. charging the printer. On the other hand, if new data relating, for example, to another character, must be printed immediately after those preceding them, the print signal transmitted on line 13a takes precedence over the end of character signal, so that the column start print signal continues to be generated, and that the data continues to be extracted from memory 14, etc., so that the required voltages can be applied to the charging electrode. In this regard, it will be noted that the memory 14 can comprise several unalterable memories, the selection of a determined assortment of characters being a function of the input received from the microprocessor 10. A method making it possible to change the assortment of characters by selecting different parts of memory is described in US Patent No. 3,963,591.

In the so-called fine printing mode, which makes it possible to obtain characters such as "B" represented in FIG. 2, the machine operates essentially in the manner described above, which is that used in the case of the IBM 6640 printer.

However, it often happens that one can be satisfied with a coarser resolution in order to obtain, in return, an increase in the printing speed. In this case, the first coarse printing mode can be used to produce characters such as "B" shown in FIG. 3. To this end, logic circuits 30 known as coarse printing are inserted between circuits 16 and 19 (Figure 5). These circuits 30 only intervene in the case where it is desired to obtain a rough impression. When fine printing is required, by appropriate instruction received from microprocessor 10, an SOS signal, which is actually a converted MCSOS signal (see below), can directly access the circuits 19, avoiding circuits 30.

For the purposes of implementing circuits 30 (see Figure 6), a signal (part of the three-byte signal from microprocessor 10) being decoded by circuit 16 and indicating that the speed of the machine must be increased and the resolution reduced so as to form characters of the type represented in FIG. 3, the decoding of, for example, 11110100 gives a first signal (COARSE PRINT or IG) whose first appearance indicates a change to the coarse print mode. The signal IG (see FIG. 9) is applied to one of the inputs of a flip-flop of the master / slave type or of a pair of flip-flops 31 so as to produce several signals at different clock times, T1 to T4, as shown in Figure 9. In Figure 6, the flip-flop 31 consists of NI gates, designated 31A to 31H in the particular embodiment shown, and a single inverter 31j, to obtain the "locking" signals (INLK), "not locked" (INLK), "sequence" (SEQ), "not sequenced" (SEQ), and "not coarse printing" (IG). The signals "restoration of power-up" (POR) or "non-restoration of power-up" (POR) are the conventional signals obtained from the logic used to start or initialize the machine. As shown in the figure, the input signals applied to the flip-flop 31 are the clock pulses T1 and T4 as well as the first signal IG coming from the decoding part of the circuit 16. These signals are applied to a second flip -flop or to a second pair of flip-flops 32 whose output consists of a so-called "coarse printing speed" (VIG) signal which is applied to the motor control device to increase the speed of the motor 7a associated with the carriage 7 of the printer. As shown in the figure, the master / slave flip-flop or the pair of flip-flops 32 also consists of NI gates 32a at 32h and includes an inverter 32j at its output. Some of the inputs of the flip-flop 32 are generated by this pair of flip-flops, for example the signals known as "excitation of the high-speed master flip-flop" (HSPM) and "non-excitation of the high-speed master flip-flop" (HSPM), which has the effect of bringing the inputs known as "high speed slave flip-flop excitation" (HSPS) and "non-excitation of high-speed slave flip-flop" as inputs to the gates NI 32a and 32b. "(HSPS), as well as the clock pulse T4. The signals SEQ and INLK are obtained from flip-flop 31.

A third master / slave flip-flop or pair of flip-flops 33 receives an MCSOS signal from the carriage position logic that comprises the circuit 16. As previously explained, this MCSOS signal is obtained from the detector 9 of Figure 1 and the circuits associated with it. On the other hand, as will be seen below, the MCSOS signal and the SOS signal are one and the same signal when the printer is operating in the so-called fine print mode, which allows characters such as that shown in Figure 2. As previously indicated, the MCSOS signals generated are a multiple of the number of lines or divisions in the network. Thus, in the example cited, if the network has 23.6 divisions per cm, 94.5 MCSOS signals will be generated per cm of displacement. When the speed of the carriage increases, the frequency of repetition of these signals obviously increases, but the distance traveled, which is representative of each of these signals, will always remain the same. In this regard, the master / slave flip-flop or the pair of flip-flops 33 acts as divider by two circuit generating a column printing signal from the "master" part of the flip-flop (SCNM) and an analog signal supplied by the "slave" part (SCNSM), as well as the logic inverses of these signals, all this in relation to the clock instants T2 and T4 which constitute the inputs of the flip-flop 33. The latter consists of NI gates 33a at 33h and an AND gate 34 of which a first input receives the SCNS output of the wears 33h. The AND gate 34 has a second input which completely avoids the flip-flop 33 and is constituted by the MCSOS signal. In this way, when the signals SCNS and MCSOS are both at the high level and coincide, the AND gate 34 generates an output, which is the SOS signal. Since the flip-flop 33 functions as a divider by two circuit, when the machine operates in the coarse printing mode, the SCNS signal is at the high level only half the time and, therefore, the signal SOS has only half the frequency of the MCSOS signal. The SOS signal shown in Figure 3 therefore has only half the frequency of the SOS signal shown in Figure 2, so that, in comparison with the fine print mode, every other column is not printed . On the other hand, in the fine printing mode, the SCNS signal is always at the high level, and therefore, when this signal coincides with the MCSOS signal, the SOS signal is generated by the AND gate 34 at a frequency which is necessarily the same as that of the MCSOS signal. The different inputs received by the flip-flop 33 are generated by the HSPS signal emanating from the flip-flop 32, and by the flip-flop 33 itself, as it emerges of the Figure.

The SOS signal thus generated is applied to the logic circuit 19 for positioning the droplets which, as previously indicated, is excited during that it receives this signal from circuit 16 at the same time as a "ready to print column" signal (PIC) emanating from the character generator 13 and generated in the manner described below. As can be seen in FIG. 7, the logic circuit 19 comprises an input flip-flop or flip-flop of the RS 35 type, which is coupled to a second flip-flop or to a second flip-flop RS 38, and a third flip-flop or a third flip-flop 37, suitable input signals being applied to a pair of flip-flops and to a flip-flop of the master / slave type 38. Flip-flops 35 to 37 consist respectively of NI gates 35a to 35d, 36a at 36d, 37a to 37c, while the pair of flip-flops 38 consists of NI doors 38a at 38h. A shift register 40 which is controlled by a control circuit 41 makes it possible to transfer the data relating to the printing of the columns, as described in more detail below, to the digital / analog converter 20 (FIG. 5), via the common line 19a, and to the charging electrode 4 associated with a nozzle 2a which comprises the droplet generator 2.

Logic circuit 19 operates as follows. When the column start printing signal (SOS) is applied to the input flip-flop 35, if the rest of the circuit composed of flip-flops 38, flip-flops 37 and 36 has completed the operations relating to the printing of the column of previous points, the flip-flops generate a loading signal of the shift register, or LDSR signal (see output from gate NI 37b) allowing the transfer of the data relating to the printing of a column, from the forty-bit shift register 39 contained in the character generator 13, at the forty-seven bit shift register 40. As shown in the figure, the shift register 39 has an SDI serial data input which receives from memory 14 the data relating to the printing of a column. Once the register 39 has been loaded, a signal is generated and applied to the circuit 39a for decoding the PIC signals (which circuit is an AND gate with multiple inputs) which, when it simultaneously receives the LDSR signal emanating from the gate 37b, generates a PIC signal to indicate that the printing of a column is ready to be carried out. When it receives this same LDSR signal as well as the "column pulse" signal (SCN) emanating from the pair of flip-flops 38 (NI gate 38h), the control circuit 41 authorizes the transfer of the data relating to the printing of a column, via the common line 39d, to the shift register 40, and subsequently via the common line 19a, to the digital / analog converter 20.

The flip-flop or flip-flop 35 allows you to store the SOS signal until the printing of the previous column is complete (note that the NI 35a gate receives as inputs a delayed SOS signal (SOSD) and a signal T2 clock however that the NI gate 35b receives in particular a signal SCNST, meaning "non-SCN stored" ", and a clock signal T4). The signal" SCN stored "(SCNST) is obtained at the output of the pair flip-flops 38, while the SOSD signal comes from flip-flop 36. In this way, the circuit shown in FIG. 7 makes it possible to process column impression data presented in series and of exceptional length which can overlap the signal Next SOS, a catch-up can take place if these data are longer than those relating to the printing of the previous column and the next column.

In the IBM 6640 printer, it is necessary to com think of the aerodynamic effects specific to ink droplets, as well as the interactions that can occur between charged droplets, so that the droplets hit the sheet of paper at the desired relative positions. The method used in the IBM 6640 printer is described in US Patent No. 4,086,601. In accordance with said method, the least significant bits from the shift register 40, for example the last seven or more bits, are used as the address of the main memory 42 of a correction data memory, as shown in FIG. 8. The output of the main memory 42 is applied to a common line called memory data and transmitted to the digital / analog converter 20 by via the common line 19a so that the appropriate voltage can be applied to the charging electrode for each bit representation of a droplet forming part of the printing of a column. The correction data memory uses a threshold voltage to prevent the droplets intended to be printed from being intercepted by the gutter. Further details can be found in the aforementioned US patent.

directement appliqué au flip-flop RS 35 de la Figure 4, ce dernier signal étant alors équivalent au signal SOS. Cependant, le reste du circuit de la Figure ε peut être employé pour obtenir le signal dit de vitesse d'impression grossière (VIG) qui est appliqué au dispositif de commande du moteur associé au chariot afin d'augmenter la vitesse de déplacement de ce dernier.The present invention also makes it possible, instead of printing only one column out of two, to skip a row of printing points out of two or to print only one point out of two when printing a column (although this printing mode is not the preferred mode, the visual impression obtained may be more pleasant in the case of certain types of character). For example, omitting one in two droplets increases the printing speed so that it approximates the same as in the case of omitting one in two columns. double that obtained in fine print mode. In this regard, the pair of flip-flops 36 in Figure 6 is unnecessary and the MCSOS signal can

directly applied to the RS 35 flip-flop in Figure 4, the latter signal then being equivalent to the SOS signal. However, the rest of the circuit in Figure ε can be used to obtain the so-called coarse printing speed (VIG) signal which is applied to the motor control device associated with the carriage in order to increase the speed of movement of the latter. .

The second modification required to print only a row of dots out of two in each column consists in ensuring that the signal VIG is applied to the control circuit 41 of the shift register (this signal being designated VIG so that the 'only one in two data relating to the printing of a column is loaded into the shift register 40 via the common line 39b, for example under the control of the loading pulse generated by the circuit 41. In this way, the shift register receives only binary data out of two, which indicates that one ink droplet out of two is not intended for printing and must be intercepted by the gutter. The third necessary modification, once again supposing that the process used to compensate for the interactions between charged droplets as well as the aerodynamic effects is that described in the aforementioned patent No. 4,086,601, consists in selecting the memory 43, relating to u coarse printing mode, so that the required corrections can be made to the droplets via the common line "memory data" from this memory, instead of being from the main memory 42.

In a variant of the present invention, the techniques for printing a column of dots out of two and a row of dots out of two described above can be combined so as to obtain a character similar to that shown in the Figure 4 in the coarse print mode. In this case, the MCSOS signal should be at the high level to allow the printing of a column on two and the VIG signal "should be applied both to the control circuit 41 of the shift register 40 and to the memory 43 for the needs of the selection of the correction data memory. On the other hand, the microprocessor 10 should obligatorily inform the control circuits of the machine that, in the coarse printing mode requested, the operating speed should be approximately equal four times that achieved in the fine print mode, and this by means of a signal obtained from the VIG signal in FIG. 6, and would also transmit a second signal for which the AND function would be produced, for example to indicate the speed increase required by the microprocessor.

The present invention therefore provides an ink-jet printer capable of varying the resolution of the characters which it prints while making a corresponding variation in the printing speed, this result being able to be obtained by making minor modifications to the material. existing.

Although the essential characteristics of the invention applied to a preferred embodiment of the invention have been described in the foregoing and represented in the drawings, it is obvious that a person skilled in the art can provide all of them. modifications of form or detail which he considers useful, without however going out of the scope of said invention.

Claims (10)

1.- Continuous ink projection printer of the type in which a carriage comprises a nozzle emitting a series of ink droplets at a predetermined flow rate, an electrode for charging the ink droplets and electrodes for deflecting the droplets of ink, said carriage being driven in movement relative to a printing medium by a variable speed drive device for printing on said character medium by forming thereon columns of dots, a first predetermined resolution of characters being defined by a predetermined maximum number of image elements per unit of width and height in a character frame of predetermined dimensions, said printer being characterized in that it comprises: means making it possible, in response to the reception of an input signal, to increase the speed of said variable speed drive device, and other circuits making it possible, in response to the application of said input signal, reduce the number of image elements in said frame so as to produce characters having a second predetermined resolution, whereby an increase in printing speed is obtained while maintaining the ink flow rate at the predetermined value. 2.- ink-jet printer according to claim 1, characterized in that the reduction in the number of image elements is carried out per unit of width. 3.- ink projection printer according to claim 1, characterized in that the reduction in the number of image elements is carried out per unit of height. 4.- ink projection printer according to claim 1, characterized in that the reduction in the number of picture elements is carried out per unit of width and per unit of height. 5.- ink-jet printer according to one of claims 1 to 4, characterized in that it further comprises: a character generator making it possible to generate data representative of the charge to be applied to selected droplets forming part of the printing of a single column, and detection means making it possible to indicate at any time the position and the direction of the movement of the carriage and of generating a first signal known as the start of column printing indicating the instant of the start of printing of each column of picture elements forming part of a given character; a variable speed carriage driving device, a droplet positioning circuit for receiving said data and said first signal and which is coupled to said charging electrode for applying a charge to the ink droplets according to said data to form a single character having a first resolution and at a first speed of the carriage, the following means being employed to obtain an increase in the printing speed on said support while maintaining the ink flow rate at a predetermined value; a first circuit for receiving a second signal indicating a modification of the speed of formation and of the resolution of a character and of the circuit comprising means making it possible to generate a third signal upon reception of said second signal to modify the speed of said driving device so that it drives the carriage at a second speed higher than the first, and a second circuit making it possible, in response to said second signal, to form a given character at a second resolution and at a second speed of movement of the carriage which is higher than the first. 6.- ink projection printer according to claim 5, characterized in that said second circuit comprises means rendering inoperative certain selected column printing start signals. 7.- ink-jet printer according to claim 5, characterized in that said second circuit comprises means making it possible, in response to said second signal and to said first signal to start column printing, to regularly or periodically suppress the signal column start. 8.- Inkjet printer according to the revenue dication 6, characterized in that it comprises means making it possible to avoid said second circuit, so that said first signal can be applied to said circuit for positioning the ink droplets in the absence of said second signal. 9. An ink projection printer according to claim 5, characterized in that it comprises means making it possible to apply said third signal to said positioning circuit of the ink droplets, and means making it possible to delete the data representing the load to be applied to one droplet out of two forming part of the printing of a single column. 10.- inkjet printer according to claim 9, characterized in that said means allow, in response to the reception of said third signal, to delete the data representing the charge to be applied to one droplet out of two forming part of the printing of a single column.

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