AU620358B2 - Process for controlling the printing quality of an ink jet printer - Google Patents

Description

OiPT flni- 14/06/89 NI) i n 96999 88 6 2 A" OI 5 8 AOJP DATE 20/07/89 PCT NUMBER PCT/FR88/00523 DEIMANDE INTERNATIONALE PUBLLEE EN VERTU DIJ TRAITE DE COOPERATION EN MATIERE DE BREVETS (PCT)

I

(51) Classification internati onale des brevets 4 (11) Numno de publication internationale: WO 89/ 04764 B41J 3/04 Al (43) Date de publication internationale: Iler juin 1989 (01.06.89) (21) Numiro de la demnande internationale: PCT/FR88/00523 (74) Mandataire: DUBREUIL, Annie; Cabinet Dubreuil, Le Suffren, 17 D, rue des Peupliers, F-56100 Lorient (22) Date de dip6t international: 25 octobre 1988 (25.10.88) (FR).

(31) Numniro de la demande prioritaire: 87/16446 (81) Etats disignis: AU, JP, US.

(32) Date de priorite: 24 novembre 1987 (24.11.87) uie (33) Pays de priorit6: FR Avec rapport de recherche internationale.

(71) Diposant (pour tous les Etats d~sign~s sauf US): IMAJE S.A. (FR/FR]; 9, rue Gaspard-Monge, Z.A. de l'Armailler, F-26500 Bourg- L~s-Valence (FR).

(72) Inventeurs; et Inventeurs/Diposants (US seulement) MILLET, Jean- Claude [FR/FR]; 9, avenue Pierre-Benoit, F-26500 Bourg-L~s-Valence REGNAULT, Luc [FR/FR]; Les Trois Becs n' 4, F-26760 Monteleger (FR).

(54) Title: PROCESS FOR CONTROLLING THE PRINTING QUALITY OF AN INK JET PRINTER (54) Titre: PROCEDE DE CONTROLE, DE LA QUALITE DE L'IMPRESSION D'UNE IMPRIMANTE A JET D'EN-

GRE

(57) Abstract In the process described, a control matrix is printed independently of tile marked message. This matrix. consists for example of 15 points whose weight increases from the first to the fifteenth drops. The distances (GI, G 2

G

3 separating the drops and the drops and and the drops and respectively, are maintained so as to constantly satisfy two relations: G 2

/G

3 and G 2

/G

3 =k 2 where (kl) and (k 2 are constants. The invention is applicable to all ink jet marking installations.

(57) Abrege L'invention concerne un proc d6 de contr6le de Ia qualit6 de l'impression d'une imprimante A jet denmcre. Une trame de contr6le est imprim~e ind~pendamment du message de marquage. Cette trame est par exemple constituee de points dont la charge va croissante, de Ia premiere A Ia quinzi~me goutte. Les distances (GI, G 2

G

3 s~parant respectivement los gouttes et les gouttes et (15) et los gouttes et (15) sont en permanence maintenues pour r~pondre aux deux relat ions: G2/G 3 et G 2

/G

3 k, sachant que (k 1 et sont des constantes. L'invention s'applique A toutes les installations de marquage par la technique du jet d'encre.

II

VERIFIED TRANSLATION OF' aL2 a9 A METHOD OF CHECKING THE PRINTING QUALITY OF AN INK JET PRINTER The invention relates to a method of checking the printing of an ink jet printer.

The applications of this type of printer, in the industrial marking field in particular, increase regularly. Purely by way of illustration, there may in particular be mentioned the printing of "use by" dates on agro-alimentary products or batch numbers. Such marking is carried out more and more using ink jet printers of the "continuous deflected ink jet" type. The correct operation of such printers is governed by a number of relatively complex parameters which must be perfectly controlled if it is desired to obtain irreproachable printing quality.

Despite the numerous improvements introduced these latter years in such printers, they are not proof against drifting of one or other of the parameters governing their operation, which may result in degradation of the quality of the writing. It is further known that, in most cases, such degradation of the writing quality has a typology in relation with the defective parameter. For example, the absence of an impact of droplets on the support to be printed may mean that the printing head needs cleaning.

Similarly, to a fault in the positioning of the droplets there may correspond an abnormal ejection speed of the droplets or an incorrect speed of the movement of the head. Another problem may arise in so far as the size of the droplets is concerned. Furthermore, manufacturing or packing lines are more and more automated and permanency of the quality appears as of prime importance. Finally, since the marking function comes at the end of the production line, any defective marking results in unacceptable losses.

The object of the present invention is to overcome these problems by describing a method and device for i- 0_ -2- A METHOD OF CHECKING THE PRINTING QUALITY OF AN INK JET PRINTER The invention relates to a method of checking the printing of an ink jet printer.

The applications of this type of printer, in the industrial marking field in particular, increase regularly. Purely by way of illustration, one may in particular be mentioned the printing of "use by" dates on agro-alimentary products or batch numbers. Such marking is carried out more and more using ink jet printers of the "continuous deflected ink jet" type. The correct operation of such printers is governed by a number of relatively complex parameters which must be perfectly controlled if it is desired to obtain irreproachable printing quality. Despite the numerous improvements introduced in the last few years in such printers, they are not proof against drifting of one or other 15 of the parameters governing their operation, which may result in degradation of the quality of the writing. It is further known that, in most cases, such degradation of the writing quality has a typology in relation with the defective parameter. For example, the absence of an impact of droplets on the support to be printed may mean that the printing head needs cleaning. Similarly, to a fault in the position of the droplets there may correspond an abnormal ejection speed of the droplets or an incorrect speed of the movement of the head. Another problem may arise in so far as the size of the droplets is concerned. Furthermore, manufacturing or packing lines are more and more automated and permanency 25 of the quality appears as of prime importance. Finally, since the marking function comes at the end of the production line, any defective marking results in unacceptable losses.

The object of the present invention is to overcome these problems by describing a method and a device for substantially overcoming or ameliorating the above mentioned disadvantages.

According to one aspect of the present invention there is disclosed a method for checking print quality of an ink jet printer which comprises the steps of: creating a controlled frame for checking a marking operation at different times and positions wherein said control frame is formed of a plurality of dots printed at a frequency related to operating conditions of said printer wherein said creating step comprises forming said control frame comprising a matrix of three dots including a middle dot, a first end dot and a second end dot; and HRF/0345y ANNEXE AU RAPPORT DE RECHERCHE INTERNATIONALE RELATIF A LA DEMANDE INTERNATIONALE NO. FR 8800523 SA 25275 Lapresente annexe indique les mnembres de Ia lamile de brevets relatifs aux documents brevets cites dans le rapport de -2Areading said control frame so as to compare said control frame with a reference frame wherein said reading comprises measuring each distance separating said first end dot and said end dot, said middle dot and said first end dot, and said middle dot and said second end dot, respectively.

According to another aspect of the present invention there is disclosed a method for checking print quality of an ink jet printer which comprises the steps of: creating a control frame for checking a marking operation at different times and positions wherein said control frame is formed of a plurality of dots printed at frequency related to operating conditions of said printer, wherein said creating step comprises forming said control frame comprising a matrix of five dots including a central dot and four surroundings dots; and S 15 reading said control frame so as to compare said control frame with a reference frame, wherein said reading step comprises measuring a height of the matrixs and each distance separating said central dot and each of said surrounding dots, respectively, so as to detect any variation of the height of said matrix, and any variation in ratios of said respective distances separating said central dot and each of said four •surrounding dots.

According to a further aspect of the present invention there is disclosed a method for checking print quality of an ink jet printer which comprises the steps of: creating a control frame for checking a marking operation at different times and positions wherein said control frame is formed of a plurality of dots printed at a frequency related to operating conditions of said printer, wherein said creating step comprises forming said control frame comprising at least three droplets and wherein said at least three droplets are charged at minimum voltage, at an intermediate voltage and at a maximum voltage, respectively; and reading said control frame so as to compare said control frame with a reference frame.

Some embodiments of the invention will now be described in reference to the drawings in which: 4 HRF/0345y 0 j 3 -3- Fig. 1 is a schematic diagram illustrating one embodiment of the construction of a device for implementing the method of the invention, Fig. 2 is a schematic diagram illustrating another embodiment, and Fig. 3 is a schematic diagram illustrating a third embodiment.

For greater clarity, the same elements bear the same reference throughout the figures.

One of the features of the method according to the invention resides in the fact that it consists on the one hand in creating a specific control frame, at given times and/or positions and in reading same so as to compare it with a control frame of the same type serving as reference.

The control frame may be autonomous i.e. independent of the text to be printed, either connected to the printer or other control members of the line. The pattern to be checked is defined and specified to the control system in real time.

1 5 According to another feature of the invention, the control frame is formed of a series of dots which can be printed either systematically, or regularly at a frequency, or regularly at a frequency resulting from an known procedure related to the specific conditions of use. This control frame is therefore printed in addition to the useful message, in general, before the latter but not limitatively.

According to another feature of the invention, the control frame is defined as a frame formed of a succession of remarkable dots. These dots are positioned so that checking thereof makes it possible to guarantee that the printing is correct with sufficient probability. For a given 25 frame and under normal operating conditions, the position of the different impacts is perfectly well known and unique within a given tolerance. If the operating conditions of the head worsen (particularly at the printing head, ink, droplets of the charge voltage, deflection voltage levels), this causes a modification of the positioning of the different impacts outside fixed tolerances. This is detected by a control means, which allows 0 detection of incorrect operation of the printing machine.

According to a first embodiment of the Invention, a control frame Is formed, as shown in figure 1, of a matrix comprising respectively a column of three dots and, as shown in figure 2, five dots In the first case (figure variations of the distance (x) separating two end dots and variations In the two distances (d 1 and G ALDA (d 2 separating dot from dot and dot from dot are lYr3fk 4 at least one droplet charged at an intermediate voltage; a droplet charged at the maximum voltage.

The voltage of the droplets is sufficient to make a significant measurement possible.

Figure 3 is an illustration of such a control frame comprising fifteen dots, going then from 1 to 15, droplets being the least deflected and droplets 15 the most i deflected.

Such printing of the control frame, as was mentioned above, is for example periodic before each message. A conventional recognition device formed for example from a lighting source, a sensor (CCD) with its optical system and associated processing electronics is provided for reading this control frame. The sensor (CCD) is focussed on the printed support at the position of impact of the droplets. This arrangement makes it possible to read the control frame whether the support is moving or stopped. In the first case, a synchronization signal causes the image of the control frame to be picked up at the moment when it arrives on the support.

The results can be used for checking that printing of the control frame is correct or not under the operating conditions of the machine.

In normal use, the operator may adjust the deflection voltage of the droplets and cause the printing distance to vary, which results in both cases in expansion of the frame heightwards. However, the relative position of the different droplets is substantially maintained if a certain charging order is respected for example, if the droplets are sent in increasing charging order. By applying this property to the control frame illustrated in figure 3. the following results are obtained

G

1 distance between impact of droplets 1 and 8;

G

2 distance between impact of droplets 8 and

G

3 distance between impact of droplets 1 and 2 F 0I -e w, Under normal operating conditions (speed of the jet and charging correct), independently of the value of the deflection voltage (specific range) and of the specified printing distance, the following relationships can be written, provided that they remain within a specified range:

G

1/G 3 k and G 2 /G3 k 2 (kl) and (k 2 are known constants whose values are the image of a correct deflection, so correct printing.

If we add to said control frame a second control frame, the control means may measure the distance between the control frames, so the printing speed which depends on the speed of the conveyor if the head is fixed or the speed of the head if the conveyor is fixed. It may thus detect in addition to printing defects, an anomaly in the travelling speed.

The invention applies, as was said above, to any industrial marking installation using the ink jet technique.

4 U .0

Claims (5)

1. A method for checking print quality of an ink jet printer which comprises the steps of: creating a controlled frame for checking a marking operation at different times and positions wherein said control frame is formed of a plurality of dots printed at a frequency related to operating conditions of said printer wherein said creating step comprises forming said control frame comprising a matrix of three dots including a middle dot, a first end dot and a second end dot; and reading said control frame so as to compare said control frame with a reference frame wherein said reading comprises measuring each distance separating said first end dot and said end dot, said middle dot and said first end dot, and said middle dot and said second end dot, respectively.

2. A method for checking print quality of an ink jet printer which S 15 comprises the steps of: creating a control frame for checking a marking operation at S: different times and positions wherein said control frame is formed of a plurality of dots printed at frequency related to operating conditions of said printer, wherein said creating step comprises forming said control frame comprising a matrix of five dots including a central dot and four surroundings dots; and reading said control frame so as to compare said control frame with a reference frame, wherein said reading step comprises measuring a height of the matrixs and each distance separating said central dot and each of said 25 surrounding dots, respectively, so as to detect any variation of the height of said matrix, and any variation in ratios of said respective distances separating said central dot and each of said four surrounding dots.

3. A method for checking print quality of an ink jet printer which comprises the steps of: creating a control frame for checking a marking operation at different times and positions wherein said control frame is formed of a plurality of dots printed at a frequency related to operating conditions of said printer, wherein said creating step comprises forming said control frame comprising at least three droplets and wherein said at least three droplets are charged at minimum voltage, at an intermediate voltage and at a maximum voltage, respectively; and reading said control frame so as to compare said control frame with a 5 reference frame. N/0345y -7-

4. A method for checking print quality as defined by claim 3, wherein said creating step comprises printing fifteen dots of increasing charge such that each distance between an impact of a first droplet and an impact of an eighth droplet, between said impact of said eighth droplet and an impact of a fifteenth droplet, and between said impact of said first droplet and said impact of said fifteenth droplet, respectively, is maintained such that a first ratio of said distance between said impact of said first droplet and said impact of said eighth droplet to said distance between said impact of said first droplet and said impact of said fifteenth droplet is constant, and a second ratio of said distance between said impact of said eighth droplet and said impact of said fifteenth droplet to said distance between said impact of said first droplet and said impact of said fifteenth droplet, is also constant.

5. A method for checking print quality of an ink jet printer, said 15 method being substantially as described with reference to Fig. 1 or Fig. 2 or Fig. 3 of the accompanying drawings. DATED this FIFTH day of DECEMBER 1991 Imaje SA Patent Attorneys for the Applicant SPRUSON FERGUSON HRF/0345y F y^^ 1 U f/| tE/ 7