Method of high speed printing multiple droplets

Abstract

A method of high speed printing of multiple ink drops is disclosed, in particular a method of forming at least multiple print dots on a surface by means of at least multiple ink drops (24) generated by a print head of a continuous inkjet printer, the method comprising for each of the multiple print dots: a) determining whether all of the at least multiple ink drops (24) are protected from disturbance caused by air resistance or whether at least one of the at least multiple ink drops is unprotected from disturbance; b) generating and charging each of the at least multiple ink drops in dependence on whether each of the at least multiple ink drops is protected from disturbance or unprotected from disturbance; c) printing the at least multiple ink drops on the surface.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of printing ink drops and to a printer, in particular a method of printing ink drops at high speed and to a printer. BACKGROUND

[0002] Continuous inkjet ("CIJ") printers are particularly used to print characters (letters and / or numbers and / or symbols) on a surface, in particular on a non-flat surface such as a cable or a bottle or a can.

[0003] As shown in FIG. 1A and FIG. 1B , the printing mode of a CIJ printer is generally a dot-matrix mode in order to print a character such as the character shown in FIG. 2 . FIG. 1A A succession of ink drops generated by a generator of the printer is shown, which is used to print a dot column (or printing ink drops) of the character shown in FIG. 1B : FIG. 2 the first or the last column of the character shown in FIG. 1A : the ink drops of said dot column fly towards a support on which the character has to be printed; FIG. 2 The printing of a character is shown to consist of successive printing columns 2, the printing columns 2 being separated by a predetermined distance d, each column comprising a plurality of printing ink drops, each printing ink drop being located at a specific pixel. In a dot-matrix mode, each column is processed and printed one after the other and independently of each other, a column being printed each time the support moves by a predetermined distance or pitch d (the distance or pitch d corresponding approximately to the distance between the middle of two adjacent columns of the printed character shown in FIG. 2 ): the printing substrate travels along a direction X and the position of the printing substrate relative to the printing head is detected by a detector or a device detecting the travel distance, said detector or device emitting a position signal each pitch d. This signal is received by a controller of the printer and the emission of a group of ink drops for printing a column can be synchronized with the displacement of the substrate each time by a distance d.

[0004] The group of ink drops of each column comprises as many ink drops as possible as the dots in the column, some of said ink drops being used for printing, some of the ink drops possibly not participating in the printing and the group of ink drops further comprising guard ink drops.

[0005] Any ink drop generator, in particular those implementing piezoelectric devices, works at a fixed frequency. Thus, ink drops are generated at a constant rate. The number of ink drops generated at a low speed is sufficient to print a character in a dot-matrix mode, but when the printing speed increases (in particular in the case of extruded products such as cables or pipes or tubes or conduits), the number of ink drops generated is insufficient.

[0006] However, aerodynamic perturbations (between the ink drops and the aerodynamic interaction of the ink drops with the environment) disturb the trajectory of the ink drops and affect at least the first printed character: the first ink drop of the first character is slowed down by this perturbation; therefore, the first printed character is crooked.

[0007] The aerodynamic perturbations can also affect other printed characters, or other ink drops in a string or group or succession, which are not sufficiently protected by the preceding ink drops. Again, this can result in printed characters which are crooked.

[0008] The problem is even more serious when printing on uneven surfaces, such as cables or bottles or cans, or extruded products, such as catheters or tubes or pipes or conduits, because of the curvature or bending of the product, resulting in different ink drops having different flight times.

[0009] The problem is even more serious when printing at high speed, for example, at a speed of 5 to 10 m / s or higher than 10 m / s or higher than 17 m / s.

[0010] One problem is to improve the print quality of all characters (letters, numbers, etc.), in particular at high speed. SUMMARY

[0011] The invention provides a first method of forming at least a plurality of printed points on a surface by means of at least a plurality of ink drops generated by a print head of a continuous inkjet printer, said method comprising, for each character:

[0012] a) determining whether all of the at least a plurality of ink drops are protected from a perturbation caused by air drag or whether at least one of the at least a plurality of ink drops is unprotected from said perturbation;

[0013] b) charging each of the ink drops depending on whether it is protected from said perturbation or unprotected from said perturbation;

[0014] c) printing the ink drops.

[0015] In particular, the invention provides a method of forming at least a plurality of printed points on a surface by means of at least a plurality of ink drops generated by a print head of a continuous inkjet printer, said method comprising, for each character:

[0016] a) determining whether all of the at least a plurality of ink drops are protected from a perturbation caused by air drag or whether at least one of the at least a plurality of ink drops is unprotected from said perturbation;

[0017] b) for each of the at least a plurality of ink drops, selecting charge data from at least a first set of data or database of charge data of ink drops that are protected from the disturbance, or from at least a second set of data or database of charge data of ink drops that are not protected from the disturbance, according to the result of step a);

[0018] c) generating and charging an ink drop of the at least a plurality of ink drops according to the charge selected from the at least first set of data or database (DB1) or from the at least second set of data or database (DB2);

[0019] d) printing the at least a plurality of ink drops on the surface, thereby forming the character.

[0020] For each ink drop, the charge data can be selected one by one from the at least first set of data or database of charge data (DB1) or from the at least second set of data or database of charge data (DB2). Alternatively, for a plurality of ink drops (or printable ink drops) to be printed, the charge data can be selected from the at least first set of data or database of charge data (DB1) or from the at least second set of data or database of charge data (DB2) to form:

[0021] - a plurality of points or all points of the same column (direction of travel perpendicular to the substrate), these points forming for example a part of a character or a message;

[0022] - a plurality of points, for example all points, of several columns (each column being perpendicular to the direction of travel of the substrate), the several columns forming for example an entire character or an entire message.

[0023] In the method according to the application, each ink drop of the plurality of ink drops can be used to form a part of a character or an entire character (in particular in the "character mode" as defined below).

[0024] In the method according to the application, the step of determining whether all ink drops of the at least a plurality of ink drops are protected from the disturbance caused by air resistance or whether at least one ink drop of the at least a plurality of ink drops is not protected from the disturbance can be based on whether at least another printable ink drop (or ink drop to be printed), i.e. a so-called previous ink drop to be printed or printable ink drop, or a previous plurality of ink drops to be printed or printable ink drops, precedes the at least a plurality of ink drops.

[0025] In particular, the step of determining whether all ink drops of the at least a plurality of ink drops are protected from the disturbance caused by air resistance or whether at least one ink drop of the at least a plurality of ink drops is not protected from the disturbance can be based on:

[0026] - if there is only one previous printable or to-be-printed drop before said at least multiple drops, based on the number or duration of non-printable drops between the generation of said one previous printable drop and the generation of the first drop of said at least multiple drops.

[0027] - if there are multiple previous printable or to-be-printed drops before said at least multiple drops:

[0028] * based on the number of said previous multiple to-be-printed or printable drops; and

[0029] * the number or duration of non-printable drops between the generation of the last drop of said previous multiple to-be-printed or printable drops and the generation of the first drop of said at least multiple drops, non-printable drops not being used for printing or being non-printable.

[0030] In both cases, said step of determining can be based on:

[0031] - comparing the number of previous multiple to-be-printed or printable drops to a minimum number of to-be-printed or printable drops considered sufficient to protect drops of said at least multiple drops,

[0032] - and / or comparing said number or said duration of non-printing drops between the generation of a previous to-be-printed drop or the generation of the last drop of a previous multiple to-be-printed drops and the generation of the first drop of said at least multiple drops to a maximum number or maximum duration of non-printing drops, said previous to-be-printed drop or previous multiple to-be-printed drops not being protected if said maximum duration or maximum number is exceeded.

[0033] The charge data can be selected from a plurality of first groups of data, each group of data being associated with a charge range, and / or from a plurality of second groups of data, each group of data being associated with a charge range.

[0034] In particular, the charge data are preferably selected from:

[0035] - a plurality of first groups of data of drops protected from said perturbation, each of said first groups of data comprising charge data within a certain charge or voltage range; for example, a first group of data comprises charge data within a first range V 1- - V 1+ , and at least a second group of data comprises charge data within a first range V 2- - V 2+ (V 1+ < V 2-- and / or, a plurality of second groups of data of drops not protected against said perturbation, each of said second groups of data comprising charge data within a range of charges or voltages; for example, the first group of data comprises charge data within a first range V i- - V i+ , and at least a second group of data comprises charge data within a first range V (i+1)- - V (i+1)+ , V i+ < V (i+1)- ;

[0036] - and / or, a plurality of second groups of data of drops not protected against said perturbation, each of said second groups of data comprising charge data within a range of charges or voltages; for example, the first group of data comprises charge data within a first range V 1- - V 1+ , and at least a second group of data comprises charge data within a first range V 2- - V 2+ , V 1+ < V 2- ; more generally, charge data of drops not protected against said perturbation can be chosen from N' groups of data, each group of data i (1 < i < N') comprising charge data within a range V i- - V i+ , this group of data i+1 comprising charge data within a range V (i+1)- - V (i+1)+ , V i+ < V (i+1) .

[0037] These different groups of data with different ranges of charges are adapted to print drops at different ranges of distances with respect to a fixed reference, for example to print drops at different ranges of distances with respect to the trajectory of an undeflected drop or with respect to the slot, for example to print the same character or a set of points, the charge data being different according to the distance of the character or point with respect to a fixed reference, for example according to the distance of the character or point with respect to the trajectory of an undeflected drop or with respect to the slot.

[0038] Each of said groups of data preferably forms a database.

[0039] In a particular embodiment of the application, said plurality of printing points can form a plurality of printing lines, for example printing lines parallel to each other and located at different distances from the trajectory of an undeflected drop or at different distances with respect to the slot, the different lines being printed with different ranges of charges. In this case, the charge data can advantageously be chosen from a plurality of first groups of data, each group of data being associated with a range of charges, and / or the charge data can be chosen from a plurality of second groups of data, each group of data being associated with a range of charges.

[0040] The method according to the application is particularly suitable for printing on a surface having a curvature, for example the surface of a cable or a bottle or a can or a duct or a tube or a pipe, and / or on a surface having a speed higher than 1 m / s or higher than 5 m / s or higher than 15 m / s or 17 m / s with respect to the speed of the continuous inkjet printer.

[0041] If the surface that has to be printed has a varying speed with respect to the continuous inkjet printer, for example, the speed varies from a low speed lower than 5 m / s to a high speed higher than 5 m / s or higher than 10 m / s or higher than 15 m / s or 17 m / s, it is possible to first print at low speed in dot matrix mode and then to print at higher speed according to a different mode, in particular the so-called "character mode" described in the present application.

[0042] The application also provides a second method, also called printing "character mode", for printing a set of pixels or dots aligned along different columns between a first print column and a last print column on a surface, the method comprising:

[0043] a) generating, by a print head of a continuous inkjet printer, a set of ink drops for printing said set of pixels or dots, the first ink drop of said set of ink drops being the first printable ink drop or drop to be printed of a first column and the last ink drop of said set of ink drops being the last printable ink drop or drop to be printed of a last column;

[0044] b) charging all said ink drops from said first ink drop of said set of ink drops to the last ink drop of said set of ink drops;

[0045] c) printing the ink drops.

[0046] Said set of pixels or dots not aligned along the same column can form a character, for example a letter or a number.

[0047] Said set of pixels or dots not aligned along the same column can be formed each time the surface moves a certain predetermined distance with respect to said print head.

[0048] Said second method can implement the above-mentioned first method according to the application.

[0049] In said character mode, one or more of the points of a column can be printed before all the points of the preceding column are printed. For example, at least one column i between said first column and said last column can start to be printed before the printing of the preceding column i-1 is finished. This allows flexibility to minimize the electrostatic interaction between the ink drops used to print said preceding column and having the highest charge.

[0050] In an embodiment of the first method according to the application:

[0051] - the plurality of ink drops can be charged and printed according to a dot pattern;

[0052] - or, the plurality of ink drops can be charged and printed according to a character pattern as defined above.

[0053] The present invention also relates to a continuous inkjet printer comprising:

[0054] - means for forming a plurality of ink drops from a continuous ink jet;

[0055] - means for or programmed to determine for each of the plurality of ink drops whether each ink drop is protected from a disturbance caused by air resistance or not protected from the disturbance;

[0056] - means for charging each ink drop according to whether each ink drop is protected from the disturbance or not protected from the disturbance.

[0057] In particular, the present invention also relates to a continuous inkjet printer comprising:

[0058] - means for forming a plurality of ink drops from a continuous ink jet;

[0059] - means for or programmed to determine for each of the plurality of ink drops whether each ink drop is protected from a disturbance caused by air resistance or not protected from the disturbance;

[0060] - means for storing a first set of data or database (DB1) of charge data of ink drops protected from a disturbance caused by air resistance and a second set of data or database (DB2) of charge data of ink drops not protected from a disturbance caused by air resistance;

[0061] - means for or programmed to select, for each of the plurality of ink drops, charge data from the first set of data or database (DB1) and / or the second set of data (DB2);

[0062] - means for charging the ink drops according to the charge data selected from the first set of data (DB1) or from the second set of data (DB2).

[0063] In the continuous inkjet printer according to the present invention, the controller can determine whether all ink drops of the at least plurality of ink drops are protected from a disturbance caused by air resistance or not protected from a disturbance caused by air resistance based on whether there is at least another ink drop to be printed before the at least plurality of ink drops, i.e. a so-called preceding printed ink drop or a preceding plurality of printed ink drops.

[0064] For example, the controller can determine based on:

[0065] - if there is one preceding printed drop before the at least multiple drops:

[0066] - the number or duration of non-printed drops between the generation of the one preceding printed drop and the generation of the first drop of the at least multiple drops;

[0067] * the number of preceding printed drops; and

[0068] * the number or duration of non-printed drops between the generation of the last printed drop of the preceding multiple printed drops and the generation of the first drop of the at least multiple drops.

[0069] In a particular embodiment, the continuous inkjet printer according to the application can comprise means for selecting the printing method in dot mode and in character mode; the selection of the printing method in dot mode and in character mode can depend on the speed of the surface that has to be printed relative to the continuous inkjet printer; alternatively, the operator can also decide on the printing method in dot mode and in character mode.

[0070] The continuous inkjet printer according to the application can comprise means for storing:

[0071] - a value of the minimum number of printed drops considered sufficient to protect a number of subsequent printed drops,

[0072] - and / or, a maximum number or a maximum duration of non-printed drops, beyond which a preceding printed drop or a preceding multiple printed drops does not protect one or more printed drops.

[0073] The continuous inkjet printer according to the application can comprise means for or programmed to:

[0074] - compare the number of printed drops to the minimum number of printed drops considered sufficient to protect a drop or drops of a number of subsequent drops,

[0075] - and / or, compare the number or duration of non-printed drops between the generation of a preceding printed drop or the generation of the last printed drop of a preceding multiple printed drops and the generation of the first drop of the at least multiple drops to the maximum number or the maximum duration of non-printed drops, beyond which a preceding printed drop or a preceding multiple printed drops does not protect.

[0076] The continuous inkjet printer according to the application can store:

[0077] - a plurality of first sets of data of ink drops protected from aerodynamic disturbances, each of said first sets of data comprising charge data over a range of charges or voltages;

[0078] - and / or a plurality of second sets of data of ink drops not protected from said disturbances, each of said second sets of data comprising charge data over a range of charges or voltages.

[0079] Each of said sets of data can form a database.

[0080] The continuous inkjet printer according to the application can comprise means for or programmed to select charge data one by one from said at least first set of data or database (DB1) of charge data or said at least second set of data or database (DB2) of charge data. Alternatively, said means for or programmed to select charge data allow to select, for a plurality of ink drops to be printed, from said at least first set of data or database (DB1) of charge data or said at least second set of data or database (DB2) of charge data, the charge data to be printed for said plurality of ink drops to form:

[0081] - a plurality of dots, for example a part of a character or message;

[0082] - a plurality of dots, for example an entire character or an entire message.

[0083] The printer or printer controller implemented according to the application or in the method according to the application comprises means according to the application for receiving an instruction to print a plurality of ink drops and selecting the appropriate charge data of the ink drops. BRIEF DESCRIPTION OF DRAWINGS

[0084] FIG. 1A and 1B represents ink drops generated by a CIJ printer for printing a character in dot-matrix mode;

[0085] FIG. 2 represents a character printed in dot-matrix mode;

[0086] FIG. 3 represents a series of ink drops generated by a CIJ printer;

[0087] FIG. 4 represents a step of an example of the method according to the application;

[0088] FIG. 5A and FIG. 5B represents ink drops generated by a CIJ printer for printing a character in character mode;

[0089] FIG. 6A represents a character printed according to a protected character mode; FIG. 6B represents a character printed according to an unprotected character mode;

[0090] FIG. 7A represents a letter to be printed, FIG. 7B and FIG. 7C gives the charge applied to the ink drops in order to print said letter in dot matrix mode FIG. 7B and in character mode FIG. 7C ;

[0091] FIG. 7D to FIG. 7E represents a set of ink drops flying under a protected mode FIG. 7D and an unprotected mode FIG. 7E towards a surface on which a character has to be printed in character mode FIG. 7A ;

[0092] FIG. 7F and FIG. 7G represents a letter "E" printed in dot matrix mode at a first speed and a letter "E" printed in character mode at a second speed higher than the first speed;

[0093] FIG. 8A represents a letter to be printed, FIG. 8B and FIG. 8C gives the charge applied to the ink drops in order to print said letter in dot matrix mode FIG. 8B and in character mode FIG. 8C ;

[0094] FIG. 8D to FIG. 8E represents a set of ink drops flying under a protected mode FIG. 7D and an unprotected mode FIG. 7E towards a surface on which a character has to be printed in character mode FIG. 8A ;

[0095] FIG. 9 represents a printed message comprising three printed lines;

[0096] FIG. 10 represents a printed message, the printed message comprising a first part printed on one line and a second part printed on three lines;

[0097] FIG. 11A and FIG. 11B respectively a letter printed in character mode, in unprotected mode FIG. 11A (upper part) and in protected mode FIG. 11A (lower part) at a low speed (6 m / s, FIG. 11A ), and a letter printed in character mode, in unprotected mode FIG. 11B (upper part) and in protected modeFIG. 11B The lower part) descends at a higher speed (12m / s). FIG. 11B A comparison example of printed letters;

[0098] FIG. 12A This is a schematic diagram of the printhead of an offset continuous jet printer to which the present invention can be applied;

[0099] FIG. 12B This represents the main unit of an inkjet printer to which the present invention can be applied;

[0100] FIG. 13 This describes the structure of an inkjet printer to which the present invention can be applied. Detailed Implementation

[0101] First, the method according to an embodiment of the present invention is explained to determine whether the ink droplets used to form printed characters are protected from disturbances caused by aerodynamic effects or are unprotected and subject to disturbances caused by aerodynamic effects.

[0102] like FIG. 3 As shown, the droplet generator of the CIJ printer generates continuous droplets or continuous strings or groups of droplets 20, 22, and 24. A group of droplets 20 (printable droplets) will form at least a portion of, for example, a first printed character (“previous character”), or form the first portion of a printed character. Immediately following the group of droplets 20 are non-printable droplets 22, followed by another group of droplets 24 (printable droplets). This other group of droplets 24 will form at least a portion of, for example, a second printed character (“next (or subsequent) character” or “new character”) or the second portion of a printed character.

[0103] If the number of ink droplets 24 is higher than the predetermined minimum number (N) s,protec If the continuous ink droplets 20 (not ink droplets 22, since ink droplets 22 are not deviated) can protect ink droplets 24 from aerodynamic disturbances. By generating ink droplets 20, 22, and 24, printing ink droplets 20 and 24, and determining whether a series of printable ink droplets 24 are skewed or have a regular shape, the minimum number can be estimated experimentally; for example, if ink droplets 20 and 24 as described above belong to the previous character and the next character respectively (they belong to the first and second parts of the same character respectively), by determining whether the new character is skewed or has a regular shape (determining whether the second part of the character is skewed).

[0104] The ink drops 20 can only provide some protection against aerodynamic disturbance for the ink drops 24 during a certain time: after the last ink drop of the ink drops 20, the ink drops 24 are no longer protected after a certain amount of time (maximum protection duration). The maximum duration can be estimated or calculated: as the frequency of generation of ink drops is constant, the amount of time corresponds to the number of non-printing ink drops 22 (N max,npd ) generated during the amount of time; in other words, the ink drops 22 are those ink drops separating the two groups of ink drops 20, 24: the ink drops 22 are immediately after the last ink drop of the consecutive ink drops 20 and immediately before the first ink drop of the ink drops 24.

[0105] The number of consecutive ink drops 20 forming at least a part of a first printed character or a first part of a printed character, for example, and preceding the consecutive ink drops 24 (Meas(N p,d ) can be counted or measured, for example by the controller of the CIJ printer. The measured number of ink drops 20 can be compared to a predetermined minimum number (N s,protec ).

[0106] The number of non-printing ink drops 22 following the ink drops 20 and preceding the ink drops 24 (Meas(N np,d ) can also be counted or measured. The measured number of ink drops 22 can be compared to a predetermined maximum number (N max,npd ).

[0107] Based on the above comparisons, it can be determined whether the ink drops 24 are protected against aerodynamic disturbance or not.

[0108] If the ink drops 24 are not protected against aerodynamic disturbance (which would be the case, for example, if there are no other ink drops preceding the ink drops), the charge of the ink drops 24 can be modified with respect to the case where the ink drops are protected against aerodynamic disturbance.

[0109] For the above reasons, at least a first set of data or a first database (DB1) can be created, comprising, for each ink drop 20, 24 generated for forming at least a part of each character or one or more parts of a character, the charge to be applied in the case where the ink drop is protected against aerodynamic disturbance. To create the first set of data or database, ink drops 24 can be generated and a number of ink drops 20 are present preceding the ink drops 24, the position and number of ink drops 20 can be varied to determine how the ink drops 20 can protect the ink drops 24 against aerodynamic disturbance. The charge applied to the ink drops 24 to obtain a high quality print can be identified or measured. This can be done for each character in a set of characters.

[0110] A second set of data or second database (DB2) can be created, comprising for each drop 20, 24 generated for forming at least one part of each character or one or more parts of a character, the charge to be applied in the case where said drop is not protected from suffering aerodynamic perturbations. To create the second set of data or database, drops 24 can be generated but without the presence of a previous drop 20, 22: thus, drops 24 are subject to the interference of aerodynamic effects and the charges applied to drops 24 to obtain a high quality print can be identified or measured. These charges (and the number of protecting drops or shielded drops) are different from the charges applied to the same drops 24 when they are protected.

[0111] In other words, depending on whether a drop is protected or not by a previous drop (for example, a drop used to print a previous character or a part of the same character), the charge can be selected from the appropriate set of data or database.

[0112] Since the drops are generally charged by one or more charging electrodes 64 FIG. 12A ), the charges of the set of data or database can be identified by the corresponding voltages applied to said electrodes to generate the required charges.

[0113] In summary, the number of previous printable drops 20 (N p,d ) and the number of previous non-printable (and non-printed) drops 20 (N np,d ) are counted or calculated. For any new group or string of drops 24: N p,d and N np,d (N p,d and N np,d can be counted by the printer) are measured, giving the measured values meas(N p,d ) and meas(N np,d ).

[0114] If:

[0115] meas(N p,d ) ≥ N s,protec

[0116] and if:

[0117] meas(N np,d ) ≤ N max,npd ,

[0118] then the charge of the drop 24 is selected from the first set of data or database (DB1).

[0119] If one of the above conditions is not met: the charge of the drop 24 is selected from the second set of data or database (DB2).

[0120] During the printing operation, the charge can be selected from one or the other of said data sets or databases, depending on whether one or more of the plurality of droplets 24, which are used to form, for example, a new character or part of a character, are protected.

[0121] FIG. 4 The printing step of the method according to the application is outlined:

[0122] - first (step S1), it is determined whether one or more of the plurality of droplets 24 are protected;

[0123] - if the droplets 24 are protected, the charge is selected from the first data set or database (step S2);

[0124] - if the droplets 24 are not protected, the charge is selected from the second data set or database (step S3);

[0125] - the droplets 24 are generated and the charge from the respective data set or database is applied to the droplets 24 (step S4); it must be noted that the droplets are charged at the same time as they are generated, as can be understood from FIG. 12A - the droplets are separated from the inkjet while they are in the charging electrode 64; FIG. 12A

[0126] - the droplets or the character are printed (step S5);

[0127] - for example, the printing operation can continue with the next droplet or droplets for the next character or the same character (step S6).

[0128] The first plurality of droplets, which are not protected and which are generated and charged to form, for example, a character or a message, can be followed by a second plurality of droplets, which are protected and which are generated and charged to form, for example, a character or the same message, the charge data of the first plurality of droplets being selected from the second data set or database (DB2) and the charge data of the second plurality of droplets being selected from the first data set or database (DB1).

[0129] The first plurality of droplets, which are protected and which are generated and charged to form, for example, a character or a message, can be followed by a second plurality of droplets, which are not protected and which are generated and charged to form, for example, a character or the same message, the charge data of the first plurality of droplets being selected from the first data set or database (DB1) and the charge data of the second plurality of droplets being selected from the second data set or database (DB2).

[0130] ​Thus, depending on the protected or unprotected nature of the ink drops to be charged, the printer can switch from one set of said data or database to another set of data or database, in any order, during printing, for example during the printing of the same message, or even during the printing of the same character or part of a character.

[0131] In a particular embodiment, N s,protec = 1 : a single generated ink drop 20, or a first ink drop protecting the formation of a print dot (". ") on the surface, is followed by an ink drop 24 of said first ink drop.

[0132] In a more particular embodiment, the number (N np,d ) of non-printing ink drops 22, after said first protecting ink drop 20 and before said ink drop 24, can be equal to zero: in this case, any white space generates an aerodynamic disturbance, and any ink drop following a white space of a set of ink drops 24, immediately after said white space (or without previous ink drop) must be charged by a charge from a second set of data or database (DB2).

[0133] Another aspect of the invention will now be explained in connection with FIG. 5A and FIG. 5B , which can or not be combined with the first aspect described above.

[0134] This aspect of the invention relates to a new printing mode, different from the dot-matrix mode described above.

[0135] Another printing mode, the so-called "character" printing mode, allows to reduce the number of ink drops used to print each character, see FIG. 5A and FIG. 5B , FIG. 5A shows a set of ink drops generated by the generator of the printer according to this "character" printing mode: the ink drops fly towards the support where the character has to be printed, FIG. 5B shows the printed ink drops.

[0136] In the "character" printing mode, the whole character is considered as a single row of ink drops, and the charge of all the printable ink drops of the whole character is computed together to obtain a good printing. No non-printing ink drops are generated, except for some protecting ink drops.

[0137] In the "character" printing mode, a succession of ink drops is generated to print the whole character, or more generally, a set of pixels or ink drops aligned along different columns between a first printing column and a last printing column; in the dot-matrix mode given above in connection with FIG. 1A to FIG. 2 , successive strings or sets of ink drops are generated or selected, charged and deviated, and the columns of the character are printed one after the other.

[0138] In other words, in the new "character" printing mode, whenever the print head moves forward a predetermined distance or spacing, all the ink droplets necessary to form a character or group of pixels, or any printed dots, are generated and charged, even if these dots are not aligned along the same column or belong to different columns. As described above, the print substrate travels along direction X, and its position relative to the print head is detected by a detector or a device for detecting this travel, which sends a "stroke" (or position signal) received by the printer's controller at each step. Therefore, the emission of all ink droplets for printing a group of dots or an entire character that are not aligned along a row perpendicular to direction X can be synchronized with a single step of the substrate's travel.

[0139] In the new printing mode, ink droplets are preferably printed not in the order they appear in the printed characters. Specifically, a column can be started before the previous column is finished printing. This provides the possibility of separating the droplets with the highest charge, thus reducing electrostatic interactions between them. In one example, if the characters have N columns i (1 ≤ i ≤ N), and each column has n... ic Point j (1≤j≤n) ic If, before printing at least one point in column i, for example, before printing a point in column i using an ink droplet having the largest charge in the ink droplet used to print column i, at least one or more points in column i+1 can be printed. Therefore, an ink droplet used to print a point in column i and having the second largest charge in the ink droplet used to print column i will interact less with the ink droplet having the largest charge in the ink droplet used to print column i+1.

[0140] FIG. 6B This illustrates how characters printed according to the "character" pattern become distorted due to aerodynamic disturbances. FIG. 6A The same character with a regular shape is shown.

[0141] Now combine FIG. 7A to FIG. 8C Examples of generating characters in bitmap mode and character mode are given.

[0142] FIG. 7A and FIG. 8A Each figure in the diagram represents a letter, which can be printed in either dot matrix or character mode (if the number of ink droplets printed is the same for the same substrate speed, the result is usually the same in both modes).

[0143] FIG. 7B It provides an application to ink droplets for printing in unprotected dot matrix mode. FIG. 7A The charge of the letter "E", FIG. 7C The method involves applying ink to the ink droplet to print in protected character mode. FIG. 7Athe same letter (using only 14 drops). The charge for each group of drops used to print dots 25-30, 31-33, 34-36, 37-39, 40-41 and the next group of drops used to print dots 31-33, 34-36, 37-39, 40-41 is separated by a group of uncharged drops and a group of drops that are not shown in FIG. 7A . FIG. 7B and FIG. 7C These charges are input into data sets or databases, respectively, for printing the letter "E" in dot-matrix mode and character mode, respectively. FIG. 7A .

[0144] It is understood that the character mode can be based on FIG. 7C One aspect of understanding the character mode is: FIG. 7A The multiple dots 25-30 of the letter "E" are printed with charged drops as shown in FIG. 7C ; the last dot 30 of the first column of E is not printed immediately after dot 29, but after dot 31, so that drops with higher charge can be separated more efficiently (e.g. drop 30 is not printed immediately after drop 29, so that the drops used to print the two dots 29, 30 are separated by the drops used to print dot 31). For the same reason, the last dot 33 (36, 38) of the second column (third column, fourth column) of E is not printed immediately after dot 32 (dot 35), but after dot 35 (dot 37). In other words, the printing of a column can start before the printing of the previous column is completed. From FIG. 7C It can also be seen that the number of charged drops used for the character mode can be smaller than the number of charged drops of the dot-matrix mode.

[0145] FIG. 7D and FIG. 7E indicates the drops used to print the letter "E" in character mode under protected mode FIG. 7D and unprotected mode FIG. 7E . FIG. 7A .

[0146] FIG. 7F and FIG. 7G indicates the letter "E" printed with 17 drops at a first speed in unprotected dot-matrix mode FIG. 7F and with 14 drops at a second speed higher than the first speed in protected character mode FIG. 7G .

[0147] FIG. 8B gives the charges applied to the drops to print the letter "E" in unprotected dot-matrix mode FIG. 8A , if the number of drops used to print is the same in both modes, the result is the same, FIG. 8CThe method involves applying ink to the ink droplet to print in protected character mode. FIG. 8A The charge of the letter "W" (using only 13 ink droplets), FIG. 8A Points 33 and 34 were not printed. FIG. 8B , FIG. 8C These charges are input into a data set or database for printing in dot matrix and character modes, respectively. FIG. 8A The letter "W".

[0148] from FIG. 8C It can be seen that the number of charged ink droplets used in character mode can be less than the number of charged ink droplets used in dot matrix mode.

[0149] FIG. 8D and FIG. 8E This indicates that during the ink droplet's flight, in protected mode ( FIG. 8D ) and unprotected mode ( FIG. 8E (Under this setting, used for printing in character mode) FIG. 8A The ink droplet is the letter "W".

[0150] from FIG. 7D , FIG. 7E , FIG. 8D , FIG. 8E It is clear that the single set of ink droplets used to print an entire character in character mode does not have the same aspects as the continuous set of ink droplets generated, charged, and deflected in dot matrix mode, where columns of characters are printed one after another.

[0151] exist FIG. 7B to FIG. 7E , FIG. 8B to FIG. 8E No protective ink droplets are shown on any of the graphs. FIG. 7B and FIG. 8B No non-printing ink droplets are shown on any of the graphs. However, the number of ink droplets generated when printing characters in character mode is less than the number generated when printing characters in dot matrix mode.

[0152] For both character and dot matrix modes, the charge of any letter (in any known alphabet) or any character (number, graphic, etc.) or graphic symbol (e.g., &, %, μ, etc.) can be calculated, evaluated, or measured. These charges are input into the corresponding data set or database for printing the relevant letter, character, or symbol.

[0153] The charge data applied to the protected ink drops and the charge data applied to the unprotected ink drops can depend on the charge range: the ink drops with higher charges also have a longer time of flight before printing on the surface and therefore are subject to more perturbations, in particular aerodynamic perturbations. For this reason, in the case of a plurality of charge ranges, preferably there is a different set of data or database for the protected ink drops of each charge range and a different set of data or database for the unprotected ink drops of each charge range. When printing a plurality of lines (preferably parallel to each other) from the same origin (identified by the Y axis perpendicular to the axis of advancement X of the printing substrate), this is particularly the case. FIG. 9 This is particularly the case when printing a plurality of lines (preferably parallel to each other) from the same origin (identified by the Y axis perpendicular to the axis of advancement X of the printing substrate).

[0154] In connection with FIG. 9 the example of printing a plurality of lines of characters is explained, FIG. 9 a message is represented comprising three parallel lines 30, 31, 32 having the same Y origin along the X axis identification:

[0155] - the ink drops of the first line 30 are printed with a charging voltage comprised between 30 and 70 volts (the charges are generated by the action of the electrodes 64, therefore the voltages are referred to);

[0156] - the ink drops of the second line 31 are printed with a charging voltage comprised between 80 and 120 volts;

[0157] - the ink drops of the third line 32 are printed with a charging voltage comprised between 130 and 160 volts.

[0158] In this example, and in the more general case of a plurality of parallel lines side by side having the same origin along the axis of advancement X, the columns of different lines located at the same position Xi are printed consecutively before the columns of different lines located at X2 are printed; in other words, for N parallel lines (as mentioned above, having the same origin along the X axis), the first column in all N lines is printed first, then the second column in all N lines is printed, and so on, before the (i + 1)th column in all N lines (1 < i < N).

[0159] Different sets of data or databases are generated due to the different charge ranges:

[0160] - a first set of data or database of charge data of the ink drops protected from aerodynamic perturbations in the first line 30 (DB11), and a second set of data or database of charge data of the ink drops not protected from said aerodynamic perturbations in the first line (DB12);

[0161] - a first set of data or database of charge data of ink drops protected from aerodynamic disturbance in the second row 31 (DB21), and a second set of data or database of charge data of ink drops not protected from said aerodynamic disturbance in the second row (DB22);

[0162] - a first set of data or database of charge data of ink drops protected from aerodynamic disturbance in the third row 32 (DB31), and a third set of data or database of charge data of ink drops not protected from said aerodynamic disturbance in the third row (DB32).

[0163] For example, the printing starts from the first left-hand portion of all three rows.

[0164] The left-hand portion of the letter "P" of the first row is not protected from aerodynamic disturbance, so the charge of the ink drops used to print this portion is selected from the second set of data or database of the first row (DB12).

[0165] The left-hand portion of the letter "F" of the third row is not protected from aerodynamic disturbance, so the charge of the ink drops used to print this portion is selected from the second set of data or database of the third row (DB32).

[0166] The left-hand portion of the letter "N" of the first row is not protected from aerodynamic disturbance (because the number of ink drops used to print the right-hand portion of the first "L" of the third row is insufficient), so the charge of the ink drops used to print this portion is selected from the second set of data or database of the first row (DB11).

[0167] The left-hand portion of the second letter "L" of the third row is not protected from aerodynamic disturbance, so the charge of the ink drops used to print this portion is selected from the second set of data or database of the third row (DB32).

[0168] Similar reasoning can be applied to FIG. 9 The other portions of the message shown are reasoned similarly.

[0169] The ink drops used to print different portions of the same character can require charges from different sets of data or databases, the ink drops used for certain portions of said character being protected from aerodynamic disturbance, while the ink drops used for certain other portions of the same character are not protected from aerodynamic disturbance.

[0170] The combination of FIG. 10 An example of the generation of such a character is explained.

[0171] The printed information extends over 3 lines 30', 31 ', 32'; a part of the message ("w25478") is printed only on the middle line 32', the high character "R" extending over the 3 lines.

[0172] The left-hand part of the first line of the letter R is not protected from aerodynamic perturbations, the charge of the drops used to print this part being therefore selected from a first set of data or database (DB12) of the first line.

[0173] The left-hand part of the middle part of the "R" character (on line 31 ') is protected by the drops used to print the left-hand part of "R" on line 30'. The charge of the drops used to print this middle part of "R" is selected from a first set of data or database (DB21) of the second line.

[0174] The left-hand part of the third line of the letter "R" is protected from aerodynamic perturbations by the drops used to print the right-hand part of "R" on the second line, the charge of the drops used to print this part being therefore selected from a first set of data or database (DB32) of the third line.

[0175] FIG. 11A and FIG. 11B Examples of printing of letters are given.

[0176] FIG. 11A The letter "R" is printed at low speed in character mode (6 m / s), in unprotected mode (upper part) and in protected mode (lower part).

[0177] FIG. 11B The letter "R" is printed at higher speed in character mode (12 m / s), in unprotected mode (upper part) and in protected mode (lower part).

[0178] In both cases, the print quality in protected mode is much better than in unprotected mode.

[0179] The above description applies to dot-matrix printing mode and character printing mode and / or to printing operations performed at low speed (< 5 m / s or < 10 m / s).

[0180] At start-up of the printer, the speed can increase from 0 to low speed (e.g. < 5 m / s or < 10 m / s) and then to higher speed (e.g. > 5 m / s or > 10 m / s or even between 15 m / s and 20 m / s) and the printing mode can change from dot-matrix mode (low speed) to character mode (high speed).

[0181] FIG. 12A to FIG. 12B A printer implementing the above-described invention is shown.

[0182] In a multi-deflection continuous jet printer, each drop of a single jet (or spaced from several jets) can be deflected on different trajectories corresponding to different commands. Thus, a succession of drops subjected to different commands can scan the region to be printed along a deflection direction, the other scanning direction of the region to be printed resulting from the relative movement of the print head and the support 800 to be printed (see FIG. 12A ). Generally, the elements are arranged so that the two directions are substantially perpendicular.

[0183] The deflected continuous inkjet print head has different operating sub-assemblies. FIG. 12A A print head of a multi-deflection CIJ printer is specifically illustrated. The printer comprises:

[0184] - means 21, 23 for generating a jet of drops, called drop generator or stimulator;

[0185] - means 64 for charging the drops (typically one or more electrodes);

[0186] - means 62 for recovering the ink not used for printing (or "slot");

[0187] - means 65 for deflecting the charged drops for printing (typically one or more electrodes);

[0188] - means possibly for monitoring and controlling the deflection of the drops (synchronization of drop formation and deflection commands).

[0189] In the drop generator 21, the cavities are supplied with electrically conductive ink. This ink, maintained under pressure by an ink circuit 27, typically outside the print head, escapes from the cavities through at least one metering nozzle 6, thus forming at least one jet of ink 11.

[0190] The periodic stimulation means 23 are associated with the cavities in contact with the ink upstream of the nozzles 6; the stimulation means 23 transmit a periodic modulation (pressure) to the ink, which thus causes a modulation of the jet radius and velocity from the nozzles. When the dimensions of the elements are suitable, this modulation is amplified in the jet under the effect of surface tension, which leads to capillary instability of the jet, up to the breaking of the jet. This breaking is periodic and occurs at a precise distance from the nozzle, at the so-called break-off point 13 of the jet, this distance depending on the stimulation energy.

[0191] In the case where the stimulation means, called actuator, comprise a piezoelectric ceramic in contact with the ink of the cavities upstream of the nozzles, the stimulation energy is directly related to the amplitude of the electrical signal used to drive the ceramic. Within the framework of the invention, other jet stimulation means (thermal, electro-hydrodynamic, acoustic...) can also be implemented. The use of a piezoelectric ceramic to implement the stimulation remains the preferred embodiment because of its efficiency and relative operability.

[0192] At its break point 13, the continuous jet issuing from the nozzle is transformed into a train of identical and uniformly spaced drops 11. The drops are formed at the same temporal frequency as the frequency of the stimulation signal; for a given stimulation energy, any other parameter being stable, there is a precise (constant) phase relationship between the periodic stimulation signal and the break instant, which itself is periodic and has the same frequency as the stimulation signal. In other words, an exact instant of the stimulation signal cycle corresponds to an exact instant of dynamic separation of the jet drop.

[0193] In the absence of further action (which is the case for drops not used for printing), the drop train travels along a trajectory 7 which is collinear with the drop ejection axis (the nominal trajectory of the jet), which is connected by the geometry of the printhead to a recovery slot 62. This slot 62 serves to recover non-printing drops, to absorb unused ink, which is returned to the ink circuit 27 for recycling.

[0194] For printing, the drops are deflected and deviate from the nominal trajectory 7 of the jet. The drops thus follow an oblique trajectory 9 which meets the support 800 to be printed at different desired impact points. All these trajectories lie in the same plane. The placement of the drops on the drop impact matrix to be printed on the support, to form a character, is achieved, for example, by combining the individual deflection of the drops in the deflection plane of the printhead with the relative movement between the printhead and the support to be printed, generally perpendicular to the deflection plane. In the case of deflected continuous jet printing technology, the deflection is achieved by charging the drops and by subjecting them to an electric field. In practice, the means for deflecting the drops comprise at least one charging electrode 64 for each jet, located in the vicinity of the break point 13 of the jet. The aim is to selectively charge each drop formed with a predetermined charge value, which is generally different from one drop to another. To this end, the ink is maintained at a fixed potential in the drop generator 21, a voltage tank with a determined value, driven by a control signal, being applied to the charging electrode 64, which value is different at each drop cycle. The charging electrode is connected to the control signal of the printhead, which is itself connected to the control unit 23.

[0195] In the control signal of the charging electrode, the voltage application instant is shortly before the jet fragmentation, to take advantage of the electrical continuity of the jet and to attract at the jet tip a given charge quantity which is a function of the voltage value. The variable charging voltage providing the deflection is generally between 0 and 300 volts. The voltage is then maintained during the fragmentation process, to stabilize the charge until the separated drop is electrically insulated. The voltage is maintained applied for a certain time after the drop separation, to take into account the problem of instantaneous breakage.

[0196] The ink drop deflection device generally comprises a set of 2 deflection plates 65, located on either side of the trajectory of the ink drops upstream of the charging electrode. These two plates are placed at a high fixed relative potential to create an electric field Ed substantially perpendicular to the trajectory of the ink drops, thus enabling the deflection of the charged ink drops engaged between the plates. The deflection amplitude is a function of the charge, mass and speed of these ink drops.

[0197] The CIJ printhead can also comprise a plurality of ink ejection cavities for generating a plurality of ink jets, each cavity having its own nozzle and activation means, or the same cavity can comprise a plurality of nozzles to produce a plurality of ink jets. As mentioned above, a charging electrode and a deflection electrode can be associated with each jet.

[0198] The instructions for activating the means 21, 23 for generating ink jets, and / or for activating the pumping means, for example the tank, and / or for opening and closing the valves in the different fluid (ink, solvent, gas) paths, can be sent by control means, also called "controller". It is also these instructions that will make it possible for the ink to circulate under pressure in the direction of the means 21, 23, then to generate jets according to the pattern to be printed on the support 800. These control means are implemented, for example, in the form of a processor or microprocessor, or in the form of a circuit or electronic circuit, programmed to implement the method according to the application, or software designed to implement the method according to the application. The control means can also ensure the storage of data, for example, the measurement of the level of ink in one or more reservoirs and potential processing thereof.

[0199] The control means can also store data of at least a first set of data or database (DB1) and at least a second set of data or database (DB2) in order to implement the method according to the application in dot matrix mode or in character mode. More precisely, said sets of data or databases can be stored in one or more memories, for example FPGAs, the data being read by the processor or microprocessor or electronic circuit mentioned above. The control means also control the voltage applied to the charging electrode and / or to the deflection electrode.

[0200] FIG. 12B The main units of an inkjet printer that can implement one or more embodiments of the application are represented. The printer comprises a console 300, in particular containing a compartment (or fluid circuit) 400 for regulating the circuits of the ink and the solvent, and reservoirs of ink and solvent (in particular, reservoirs to which the ink recovered by the tank is returned). Generally, the compartment 400 is in the lower part of the console. The upper part of the console comprises the command and control electronics and the visualization means. The console is connected to the printhead 100 by a umbilical 203, both hydraulically and electrically.

[0201] A not shown gantry enables the printhead to be mounted facing the print carriage 800, which moves in the direction indicated by the arrow. This direction is perpendicular to the axis of alignment of the nozzles or to the axis of deviation of the ink drops (see FIG. 12A The carriage moves continuously along the direction X. The position of the carriage relative to the printhead is detected by the detector 401.

[0202] Such a printer can be integrated into a packaging machine.

[0203] The printer according to the application is an industrial printer, for example, capable of printing on uneven surfaces such as cables or bottles or cans. Another aspect of such a printer is the distance between the printhead and the substrate that has to be printed, which is higher than for a conventional desktop printer. For example, this distance is at least 5 mm, for example, between 10 mm and 30 mm.

[0204] Another aspect of such a printer is the speed: the maximum speed is between 15-20 m / s, and typically, the nominal printing speed is between 1-5 m / s.

[0205] Another aspect of such a printer is that it can print on very different surfaces such as glass or metal or bubble or packaging material.

[0206] FIG. 13 An example of a fluid circuit 400 of a CIJ printer implementing the application is shown. This fluid circuit 400 comprises a plurality of devices 410, 500, 110, 220, 310, each of which is associated with a specific function. Also shown is the printhead 1 and the umbilical 203.

[0207] Associated with this circuit 400 are removable ink cartridges 130 and solvent cartridges 140, which are also removable.

[0208] Reference 410 denotes a main reservoir, which is capable of receiving a mixture of solvent and ink.

[0209] Reference 110 denotes a set of devices, which are capable of drawing solvent from the solvent cartridge 140 and possibly storing it and providing it to other parts of the printer, whether it concerns supplying solvent to the main reservoir 410 or cleaning or maintaining one or more other parts of the machine.

[0210] Reference 310 denotes a set of devices, which are capable of drawing ink from the ink cartridge 130 and providing it to the main reservoir 410. As can be seen from this figure, according to the embodiment presented here, solvent is sent from the devices 110 to the main reservoir 410 via these same devices 310.

[0211] At the outlet of the reservoir 410, a set of devices, globally denoted by the reference 220, can pressurize the ink drawn from the main reservoir and send it to the print head 1. According to the embodiment illustrated here by the arrow 250, it is also possible to send the ink, by these devices 220, to the devices 310, then to the reservoir 410, which makes it possible to recirculate the ink within a loop. This loop 220 also makes it possible to empty the reservoirs of the cartridge 130 and to clean the connectors of the cartridge 130.

[0212] The CIJ system illustrated in the figure also comprises devices 500 for recovering fluid (ink and / or solvent) returned from the print head, more precisely from the sump 62 of the print head or from the flushing circuit of the print head. These devices 500 are thus arranged downstream of the umbilical 203 (with respect to the direction of circulation of the fluid returned from the print head).

[0213] It can be seen from FIG. 13 that the devices 110 also make it possible to send the solvent directly to the devices 500, without passing through the umbilical 203 or the print head 1 or the recovery sump.

[0214] The devices 110 can comprise at least 3 parallel solvent supplies, one of which supplies the print head 1, a second of which supplies the devices 500 and a third of which supplies the devices 310.

[0215] Each of the devices described above is provided with means such as valves, preferably solenoid valves, which make it possible to direct the fluid concerned to the chosen destination. It is thus possible to send the solvent from the devices 110 either exclusively to the print head 1, or exclusively to the devices 500, or exclusively to the devices 310.

[0216] Each of the devices 500, 110, 210, 310 described above can be provided with a pump which makes it possible to handle the fluid concerned (first pump, second pump, third pump, fourth pump, respectively). These different pumps ensure different functions (the function of the respective device), and are thus different from one another, even if they can be of the same type or of a similar type (in other words: none of these pumps ensures two of these functions).

[0217] In particular, the devices 500 comprise a pump (first pump) which makes it possible to pump the fluid recovered from the print head as described above and to send it to the main reservoir 410. This pump is dedicated to recovering the fluid from the print head and is physically distinct from the fourth pumping device 310 which is dedicated to transporting the ink or from the third pumping device 210 which is dedicated to pressurizing the ink at the outlet of the reservoir 410.

[0218] The device 110 comprises a pump (second pump) able to pump and send solvent to the device 500 and / or to the device 310 and / or to the print head 1.

[0219] This circuit 400 is controlled by the control devices described above, which are usually contained in the console 300. FIG. 12B ).

[0220] The present application is advantageously applied to print characters on the surface of products having a curvature, for example, on the surface of cables or bottles or cans or conduits or pipes or ducts and / or of products produced at high speed, in particular extruded products such as, for example, cables or conduits or pipes or ducts.

Claims

1. A method for forming at least a plurality of print dots on a surface (800) by means of at least a plurality of ink droplets (24) generated by a printhead of a continuous inkjet printer (1, 300), the method comprising, for each of the plurality of print dots: a) Determine whether all of the at least plurality of ink droplets (24) are protected from disturbance caused by air resistance, or whether at least one of the at least plurality of ink droplets is unprotected from the disturbance, the determination being based on whether there was a previous ink droplet or a plurality of previous ink droplets before the plurality of ink droplets (24); b) Based on whether each of the at least plurality of ink droplets is protected from the disturbance or is unprotected and subjected to the disturbance, generate and charge each of the at least plurality of ink droplets, the charging being based on charge data selected from a suitable set of data, or by adjusting the charge previously defined for the ink droplets protected from the disturbance; c) Print the at least multiple ink droplets on the surface.

2. The method according to claim 1, wherein the method comprises, after step a): a1) For each of the at least plurality of ink droplets (24), based on the result of step a), select charge data from at least a first set of data DB1 of charge data of ink droplets that are protected from the disturbance, or select charge data from at least a second set of data DB2 of charge data of ink droplets that are not protected from the disturbance. Step b) includes generating each of the at least a plurality of ink droplets and charging each of the at least a plurality of ink droplets according to a charge selected from a first set of data DB1 or from a second set of data DB2.

3. The method according to claim 2, wherein, The charge data is selected from: - Multiple first sets of data of ink droplets protected from the disturbance, each of the first sets of data including charge data within a certain charge or voltage range; - and / or, multiple second sets of data of ink droplets that are not protected from the disturbance, each of the second sets of data including charge data within a certain charge or voltage range.

4. The method according to claim 2, wherein, Each of these data groups forms a database.

5. The method according to any one of claims 2 to 4, wherein, The multiple print points include multiple rows (30', 31', 32') of print points, with different rows printed using different charge ranges.

6. The method according to any one of claims 1 to 4, wherein, The multiple ink droplets are charged and printed according to either a dot matrix pattern or a character pattern.

7. The method according to any one of claims 1 to 4, wherein, The step of determining whether all of the at least plurality of ink droplets (24) are protected from disturbances caused by air resistance, or whether at least one of the at least plurality of ink droplets is unprotected and suffers from the disturbance, is based on the existence of at least one other ink droplet to be printed before the at least plurality of ink droplets (24), the at least one other ink droplet to be printed being the so-called previously printed ink droplet or the previous plurality of printed ink droplets.

8. The method according to claim 7, wherein, If there is a previously printed ink droplet (20) before the at least multiple ink droplets (24), the step of determining whether all of the at least multiple ink droplets are protected from disturbances caused by air resistance, or whether at least one of the at least multiple ink droplets is not protected from the disturbance, is based on the number or duration of non-printing ink droplets between the generation of the previously printed ink droplet and the generation of the first ink droplet among the at least multiple ink droplets.

9. The method according to claim 8, wherein, If multiple printing ink droplets (20) exist before the at least multiple ink droplets (24), the step of determining whether all of the at least multiple ink droplets are protected from disturbances caused by air resistance, or whether at least one of the at least multiple ink droplets is unprotected and subjected to the disturbance, is based on: - The number of the previously printed ink droplets (20); as well as - The number or duration of non-printing droplets between the generation of the last printed droplet among the previous plurality of printed droplets and the generation of the first droplet among the at least plurality of droplets.

10. The method according to claim 8 or 9, wherein, The step of determining whether all of the at least plurality of ink droplets are protected from disturbances caused by air resistance, or whether at least one of the at least plurality of ink droplets is unprotected and suffers from the disturbance, is based on: - Compare the number of previously printed ink droplets with the minimum number of printed ink droplets considered sufficient to protect the ink droplets in the at least multiple ink droplets. - and / or, compare the number or duration of non-printing droplets between the generation of the previously printed droplet or the generation of the last printed droplet among the previous plurality of printed droplets and the generation of the first droplet among the at least plurality of droplets with a maximum number or maximum duration of non-printing droplets, and if the maximum duration or maximum number is exceeded, then the previous printed droplets or the previous plurality of printed droplets will not provide protection.

11. The method according to any one of claims 1 to 4, wherein, The surface on which multiple dots are printed has curvature.

12. The method according to claim 11, wherein, The curved surface is the surface of a cable, bottle, can, conduit, pipe, or tube.

13. The method according to any one of claims 1 to 4, wherein, The surface on which multiple dots are printed has a speed of more than 5 m / s or more than 10 m / s relative to the continuous inkjet printer.

14. A continuous inkjet printer, comprising: - Devices (21, 23) for forming multiple ink droplets from a continuous ink jet; - Device (300) for determining, for each of the plurality of ink droplets, whether each ink droplet is protected from disturbance caused by air resistance or is unprotected and subjected to the disturbance, the determination being based on whether there is a previous ink droplet or a plurality of previous ink droplets preceding the plurality of ink droplets; - Device (64) for charging the ink droplet based on whether the ink droplet is protected from the disturbance or is unprotected and subjected to the disturbance, the charging being based on charge data selected from a suitable set of data, or by adjusting the charge previously defined for the ink droplet protected from the disturbance.

15. The continuous inkjet printer according to claim 14, wherein the continuous inkjet printer comprises: - Device (300) for storing a first set of data or database DB1 of charge data of ink droplets protected from disturbances caused by air resistance and a second set of data or database DB2 of charge data of ink droplets that are not protected from disturbances caused by air resistance; - Device (300) for selecting charge data from the first set of data or database DB1 and / or the second set of data DB2 for each of the plurality of ink droplets; - Device (300, 64) for charging the ink droplet with a charge selected from the first set of data DB1 and / or the second set of data DB2 based on whether the ink droplet is protected from the disturbance or is subjected to the disturbance without protection.

16. The continuous inkjet printer according to claim 14 or 15, wherein the continuous inkjet printer includes means for selecting a printing method in dot matrix mode and character mode.

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