DE2941322C2 - Color jet printer - Google Patents

Description

The invention relates to a color jet printer according to the preamble of claim 1. Such a color jet printer is known from DE-OS 26 07 704.

Several print heads are arranged in the horizontal direction, namely in the direction of the line extension, so that they can print an entire line at a time at high speed can. The deflection electrodes are aligned so that they are shared by multiple printheads can be; such a print head with a multiple nozzle has a relatively simple structure.

In the known electrostatic ink jet printer according to DE-OS 26 07 704, the charged Drops of paint in the direction perpendicular to the line extension only deflected so far that they do not fall into the gutter reach. To do this, however, the ink jet must be broken down into the individual ink droplets be electrostatically deflected, which on the one hand leads to a further uncertainty factor for the operation leads, on the other hand, requires additional space and finally the point at which the color beam enters the dissolves single droplets, further away from the nozzle. However, for various reasons strived to make the distance between the nozzle and this point of resolution as small as possible.

The invention is therefore based on the object of providing a color jet printer of the specified type to allow the ink jets already dissolved into droplets with charged droplets in the second coordinate direction always by a specified

be deflected on a flat, constant route.

According to the invention, this object is achieved by the im characterizing part of claim 1 specified features solved

Appropriate embodiments are defined by the features of the subclaims

The advantages achieved by the invention are based in particular on the fact that each individual ink drop is so is charged so that the desired, constant deflection results. This charging takes place in connection with the »pictorial« charging, which results in a simple structure. In particular, it is not more is necessary to charge the entire ink jet that has not yet been resolved into individual ink droplets, whereby a greater flexibility and a better resolving power can be achieved.

There are already different embodiments of color jet printers with multiple nozzles have been developed in which the charged ink droplets are deflected perpendicular to the line extension, so that they »jump over« the drainage channel and thus onto the one behind the drainage channel Recording media can arrive; However, these embodiments all have the disadvantage that the vertical deflection of the ink droplets may and may not fluctuate from one printhead to another can be set exactly with high accuracy

In the case of the color jet printer, according to DF, -OS 24 31 077, the whole is deflected in advance Color beam for adjustment purposes.

From DE-OS 24 45 257 a color jet printer of a different type emerges in which evenly charged ink droplets are used.

From DE-OS 23 53 525 it is finally known to deflect the ink droplets with a constant potential in both directions, that is to say in the X as well as in the F direction.

The invention is illustrated below on the basis of preferred embodiments with reference to FIG attached drawings explained in detail.

It shows

1 is a schematic view to explain the idea on which the invention is based;

2 shows a sequence of eight color drops which are gradually charged by a sequence of charging pulses;

3 shows a deflection electrode system according to the invention, in which a pair of deflection electrodes of the second electrode means are arranged so that the Distance between them with the distance in the direction of deflection of the time extension of the charged Color drop increases while a pair of deflecting electrodes of the first electrode means so arranged so that the distance between them is constant;

Fig. 4 shows the relationship between the deflections of the charged color drops in the direction of the time extension and the field strength which they experience when they pass between the deflection electrodes shown in FIG. 3 for the direction perpendicular thereto;

Fi g. 5 and 6 are schematic representations of a first and second embodiment of a color jet print head with a multiple nozzle according to the invention, wob ', i one of the deflection electrodes of the second electrode device is skewed with respect to the other;

7 and 8 are plan views of a third and fourth embodiment according to the invention;

F i g. 9 shows the deflection in both directions of the charged color droplets in those shown in FIGS. 7 and 8, third and fourth embodiments;

FIG. 10 shows a multi-nozzle printhead incorporating an array of printhead units of the type shown in FIG or 8 shown type in the direction of the line stretching having;

11 and 12 representations for explaining an idea on which the invention is based;
13 shows a fifth embodiment of the invention or a print head with a multiple nozzle, which is designed according to the basic concept described with reference to FIGS. 11 and 12;

14 shows a schematic representation of a sixth Embodiment of the invention; and

FIG. 15 shows the waveforms of the deflection voltages applied to the deflection electrodes shown in FIG of the second electrode device are applied.

The same or corresponding parts are denoted by the same reference numerals in the individual figures. The principle on which the invention is based is described with reference to FIGS. As shown in Fig. 1, a print head unit has a nozzle 1, a charging electrode 2, a pair of deflection electrodes 3 and 3 'of a first electrode device for deflection in the direction of the line extension (CY direction), a pair of deflection electrodes 4 and 4' of a second electrode device Deflection in a direction (y-direction) perpendicular to the direction of the line extension and the direction of the nozzle recording material and a collecting channel 5 in front of a recording paper 6. Color A is fed to the nozzle 1 with a certain pressure, and charging pulses B are applied to the charging electrode 2. If the paint drops are free of both aerodynamic and electrostatic disturbances, even though they are in flight, the deflection x _{d of} a paint drop is given by:

m.

IF

ΐΛζ, -x-

where m, the mass of a color drop, Q ₁ the charge on a color drop, V _d a voltage applied to the deflection electrode, S ₀ the distance between the deflection electrodes, V _} the speed of a color drop, l _d the length of the deflection electrodes and Z. der Is the distance from the entrance of the deflection electrodes to the recording paper.

As shown in Fig. 2, z. B. 8 step-shaped charging pulses B, which are arranged at the same distance from one another, applied to the charging electrode 2 in order to charge _{eight drops of color Q 1} to Q _8. Since the charging pulses B are negative, the color drops Q _{n are} charged positively. In the printhead unit according to the invention, a collecting gutter 5 is arranged under the color dot printing line so that the ink droplets can be applied to any places on the recording sheet 6 behind the collecting gutter 5, whereas this was not possible with conventional ink jet printers with variable charge. As a result, the entire line of color dots can be printed across the sheet 6.

As shown in Fig. 3, the deflection electrodes 3 and 3 'can be arranged parallel to each other, while the deflection electrodes 4 and 4 'can be arranged so that the distance between them with the distance in the deflection direction of the color droplets

5 6

increases through electrodes 3 and 3 '. Hence learns and
each drop of color depending on its location in

Direction of line extension (^ direction) under- S ^ ₁ < S _dn <S _dn <... <S _äyi t

different forces, so that the charged color drops Q ₁

to Qt in the perpendicular direction (K direction) s, the distance S ,, _y between the F-Ablenkelek- can _t by a predetermined distance x deflected _dy will be determined trodes, which of the following Bedinkönnen. An uncharged drop of color Q ₀ is sufficient by:
does not affect the electric fields, so that he himself

moved in the intended direction and from the x _dy = x _äy ^ = X _in = ... x _iy% . '

Channel 5 is added. 10 %

The deflection x _{d of} the charged color drops can thus all charged color drops Q _x to Q ₈ %

from Eq. (1) Depending on the charge on each one who is deflected by the same distance in this direction - color droplets can be obtained. As a result, the den.

Color droplets in the direction of line extension in Fig. 5 shows a print head with a plurality of '

Depending on the charge Q ₁ to Q _{8 are arranged} on them around nozzles, the printhead _{units being} deflected from the \ x _dXl to x dxt. the type described above in an arrangement in the direction i

When a color drop, which is charged, is arranged between the line extension. A pair of deflecting electrodes of the second electrode device 3 and 3 'of the first electrode device passes through, the field strength, which device is provided for each printhead unit and one of the color drops is exposed, changes depending on the 20 of the deflection electrodes of the second electrode device deflection of the Ink droplets in the direction of the line generation, to which a high deflection voltage V _ay , which is applied to it by the deflection electrodes, is applied to all printhead units, the first electrode device, as in FIG. 4, while the electrodes 4 ', which are grounded is shown. The color droplets with the charge Q i are exposed to the field strength change from Ey ₀ to Ey _x , which is predetermined for the corresponding printhead units. The 25 hen are and, as shown, under a certain color drop with the charge Q ₂ is inclined at a field strength angle, so that the charged color change from £> ₀ to £) j exposed, etc. The color drop drips in the K- Direction can be steered by the same distance with the charge Q ₈ isi a field strength change of Ey ₀ , as exposed with reference to FIGS. 3 and 4 to Ey _1. The average field strength is described. The deflections of the charged color earth to which the color drop Q, is exposed, can drop 30 in the JT direction, are _{different depending on the (} are represented by the charge on each color drop; as a result, the entire line of color dots can be printed across the sheet 6 * gv will.

SdV ₁₁ + Sdy, The inclination of the grounded electrodes 4 'can

2 35 can be set individually so that changes in the

y-deflection from one unit to another eliminated

where S _d y _{h can become} the distance between the deflection electrodes. On the other hand, each printhead Indian can second electrode means at the entry unit with a single electrode 4 instead of the gemeinsteiie (ie, the distance at the point Q ₀ in Fig. 3) and seed electrode are provided so that the _dl to each S, the distance between the deflection voltage V _ay applied to the deflection electrodes for the electrode 4 corresponds to the K direction at the point Q ₁ . can be fine-tuned to make changes

As a result, in connection with Eq. (1) the deflection in the y-deflection from one unit to the other, depiction of the color drop Q ₁ perpendicular to the direction of the switch. As a result, all color droplets can be directed in the X-line extension and the axis nozzle-recording direction with a higher degree of accuracy, ie in the K-direction, 45, so that printed images of high quality

can be guaranteed.

Qi V _dv 1 / - 1 ± \ InFig. 6 is a second embodiment of the invention

^Xdy m S _d + S _dv ~ V ^T \ "T) shown in which one of the electrodes 3 'for

¹ —is_— £ L ^J _the deflection in the jp direction together on the

¹ 50 adjacent printhead units is distributed. As a result-

Similarly, the average field of which the adjacent electrodes 4 ', which are the strength to which the ink droplets Q _{2 is} exposed, are grounded so as to be approached symmetrically to that by the common electrode 3' for the Z- Direction are. at

However, this arrangement is the difficulty, Y _d y 55 that the locations on the sheet 6 in the shadow of electron

S _dii + S _dv trode 3, to which a high deflection voltage
^IJ ~ 2 - ~ cannot be printed with drops of color. This difficulty can be eliminated by moving the nozzle in the Z-direction by a corresponding

Substituting this value into Eq. (1) the 60 corresponding angle is inclined.

Deflection x ^ in the F direction perpendicular to the direction. Figs. 7 and 8 are plan views of a third and

the extension of time and the nozzle-recorded axis Fourth embodiment of the invention; In Fig. 9, voltage devices for the color drop Q ₂ are obtained. Represented in trajectories of the charged color drops, the deflections x _dn to x _dn are similarly obtained while in Fig. 10 an embodiment of a color is obtained for the color drops Q ₁ to Q ₈ . Because 65 jet printhead is shown with multiple nozzles

In the third embodiment shown in FIG.

Qi < Q2 <Qi <■ ■ ■ < Q ₈ form are the deflection electrodes 4 and 4 'for the X-direction

tion so curved that it satisfies the following conditions

suffice:

^x dy

(y - Jj !? l \ = _f ±
\ " ^y 2 J KQ,

KQ ₂

run exactly synchronously with the flight time _{intervals of the charged color drops Q to Q 8} between the Y deflection electrodes. The time-of-flight intervals are

ίο to t \

Uo + At) to t ₂

(I ₀ + 2 At) to / 3

for the color drop Q,
for the color drop Q ₂
for the color drop Q ₃

^x dy

(Z ₀ + 7 At) to Ig for the color drop Q ₈

where l _{dJ / l} to l _{dy% are} the distances which the corresponding color droplets with the charges Q \ to Qg cover between the K deflection electrodes 4 and 4 ', and K is a constant which is derived from Eq. Is obtained (1) when rrij, V _{dy, dy} S and Vj are constant.

If the deflection electrodes for the y-direction, 4 and 4 ', are curved, as described above, all charged color _{drops Q 1 to Q 8} can be deflected by the same amount in the y-direction, while the uncharged color drop Q 0 is not deflected at all is, consequently moves in the predetermined direction and is picked up by the channel 5, which is arranged below the color dot printing line.

In the fourth embodiment shown in FIG. 8, the shape of the electrodes for the y-direction, 4 and 4 ', is also fixed in the manner described above. The shape shown in FIG. 8 has the advantage that the charged color drops Q ₁ to Q _{8 more precisely cover} the corresponding predetermined distances I _dV] to I dyi between the} 'deflection electrodes 4 and 4'.

In the embodiments described with reference to FIGS the deflection electrodes for the y-direction are arranged so that the distance between them with the distance in the deflection direction of the charged ink droplets due to the deflection electrodes for the ^ 'direction increases, or that the deflection electrodes for the y-direction have a constant distance have between them so that the color drops in the vertical direction by the same value regardless of the charge can be deflected on the respective paint drop; however, they can have the same effects can be obtained when a sawtooth-shaped deflection voltage is applied to a pair of deflection electrodes for the y-direction is applied, which are arranged parallel to each other, as described in detail below will.

In FIG. 11, a predetermined deflection voltage + V _{dx is applied} to a pair of deflection electrodes for the X direction, X and Λ ", which are arranged in parallel with each other, while a sawtooth-shaped deflection _voltage V lly as shown in FIG. 12 is applied to a Pair of deflection electrodes for the y-direction, y and Y ', is applied, which are also arranged parallel to each other and perpendicular to the deflection electrodes X and X' , the charged color droplets being deflected in the (here: vertical) y-direction by the same value can.

However, an uncharged ink drop Q _{0 is} not deflected in the y direction, so that it moves in a predetermined direction and is picked up by the collecting chute 5.

In Fig. 12, the sawtooth-shaped deflection voltage V _{dy is} shown, which is applied to the y-deflection electrodes. The rise and fall intervals where At is the time interval between adjacent color drops. The time intervals between /, and t _2% between t ₂ and / 3, ... and between ti and / _g gradually increase because of the summation of the time interval between the color drops, and the time-of-flight intervals increase as the charge on the color drop increases since, if the speed is the same, the more the color drop is deflected in the X-direction, the higher the charge on a color drop, so that its trajectory between the deflection electrodes door the y-direction becomes longer. As a result, the color drop with the charge Q, is deflected in the y-direction by a value which is proportional to the hatched area S \ inFig. 12 is. The color droplets Q ₂ to Q _{8 are} deflected in a similar manner.

_{The deflection voltage} for the y-direction, V dyi, which is applied to the deflection electrodes for the y-direction from the times t ₀ to f], during which the color droplet Qi flies through between the electrodes, is given by:

65 h - Ό

Substituting this value into Eq. (1) a deflection in y-direction x _dyi is obtained as follows:

m,

IAz _n - ^ -

Similarly, the sizes up to x _dn can be obtained. As the charge on the ink drops increases from Q 1 to Q j, the deflection voltage for the y direction _decreases from V dyx to V _dy% . In this way, as described above, the deflection voltage V _dy can be changed linearly in synchronism with the flight time intervals of the charged ink drops, so that the following condition can be satisfied:

dy \

iVr> · · * Fl

dyt

That is to say, all charged color drops Q ₁ to Q ₈ can be deflected by the same amount in the y-direction regardless of the charge on the color drop. The deflections in the X (or here: the horizontal) direction change depending on the charge Qi to Q ₈ on the color drop.

In FIG. 13, a print head with a plurality of nozzles is shown schematically, in which the print head units of the type described above are arranged in an arrangement in the direction of the line extension. The ink droplets which are discharged from the nozzles C and which are charged are applied along the color dot printing line A , while the non -charged ink droplets remain at the level B and move towards the collecting chute 5. the

. _ -,. . - ■ ■ —— ' ■''■ - W

ίο

Deflection electrodes for the / direction 'Kund Y' are provided in common for all printhead units and the deflection voltage for the K direction, V _d} , is applied to them, as described with reference to FIG. 12, so that the charged ink drops in X-direction away from the collection level B can be deflected.

The fifth embodiment described so far has the advantage that, since the deflection electrodes for the A'- and y-direction are arranged parallel to each other, the manufacture of the print heads can be very simplified.

In Fig. 14, a sixth embodiment is shown of a print head with multiple nozzles which the fifth, in embodiment of FIG. 13 is similar in construction, except that one of the deflection electrodes for the K-direction, Y ', which shown grounded for all printhead units is common, while the other deflection electrodes for the F direction, Y] and Y ₂ , are provided for corresponding printhead units and are alternately connected to voltage sources V _dyi and V _d " for K deflection voltages, which, as in FIG shown have opposite phases.

One of the deflection electrodes for the jf direction, X, to which the deflection voltage + V _{dx is} applied as shown, is provided in common for the adjacent printhead units so that the charged ink drops are deflected in opposite directions by the adjacent printhead units. According to the invention, a color jet printer is thus created with which not only high quality images, but also each color point can be printed simultaneously along the color point print line. Furthermore, the arrangement of deflection electrodes can be very simplified, so that the arrangement of several nozzles is also very much easier.

In addition 6 sheets of drawings

40

45

50

55

60

65

Claims (7)

Patent claims: 1. Color jet printer for line-by-line printing, in which the points of impact of the droplets of the ink jet by the size of the on the droplets respectively current charge can be determined with a nozzle from which a jet of paint is emitted, a charge electrode assembly for charging the ink droplets with charges of different sizes corresponding to the deflection of the ink droplets in the direction of the pressure signals Line extension (JT direction), a first electrode device with a constant deflection voltage to deflect the ink droplets in the direction of the line extension (ΛΓ direction), second electrode means for deflecting the ink droplets in a direction to line extension and a direction (X direction) perpendicular to the direction of the nozzle recording material and a collecting chute for collecting uncharged droplets not used for printing, characterized in that, that the second electrode device (4, 4 ') behind the first in the beam direction Electrode device (3,3 ') is arranged and is shaped so that the electric field in the second Electrode device (4,4 ') and / or the flight time of a charged ink droplet through the second Electrode device (4, 4 ') with increasing distance in the Jf direction from the center line of the nozzle decrease and / or a time-variable deflection voltage to the second electrode device is applicable to cause the charged ink droplets of a series of in the like Line of the recording medium to be deposited droplets regardless of their charge the same value can be deflected in the y-direction. 2. color jet printer according to claim 1, characterized in that the deflection electrodes (3, 3 ') the first electrode means are arranged so that the distance between them is in Dependence on the length of the trajectory of the charged ink drop between the deflection electrodes changes in the direction of the extension of the line and is not perpendicular to the extension of the line changes. 3. color jet printer according to claim 1, characterized in that the shape of the deflection electrodes (4, 4 ') of the second electrode device is chosen so that the length of the trajectory of the charged Color drops between these deflection electrodes (4,4 ') depending on the charge on the charged one Color drop can be changed. 4. Ink jet printer according to one of claims 1 or 2, characterized in that a number Deflection electrodes (3. 3 ') of the first electrode device and a number of deflection electrodes (4, 4') of the second electrode means in an arrangement in the direction of time extension in the manner each printhead means are arranged to have their own pair of deflection electrodes of the first electrode means or one of the deflection electrodes adjacent to the first electrode device Print head units is shared and one of the deflection electrodes of the second electrode device can be assigned to all printhead units together. 5. color jet printer according to claim 4, characterized characterized in that further deflection electrodes (4 ') of the second electrode device for the corresponding Printhead units provided and with respect to the common deflection electrodes (4) the second electrode means are inclined in such a way that the electric fields the adjacent printhead units become symmetrical in both size and direction can. 6. Color jet printer according to one of the preceding claims, characterized in that a plurality of print heads are arranged in the direction of the line extension in such a way that the deflection electrodes (4,4 '; Y, Y') of the second electrode device are assigned to all print head units in common, while the paired deflection electrodes (3, 3 '; X, X') of the first electrode device are provided for the respective print head units, and that a sawtooth-shaped deflection voltage is applied to the second electrode device. 7. color jet printer according to one of claims 1 to 5, characterized in that a plurality of printheads are arranged in the direction of the line extension in such a way that one of the deflection electrodes (3, 3 '; X, X') of the first electrode device adjacent printhead units together it can be assigned that one of the deflection electrodes (4,4 '; Y, Y') of the second electrode device is provided for each printhead unit, and that sawtooth-shaped deflection voltages are alternately applied to the deflection electrodes (4,4 '; Y, Y') of the second electrode device whose pulse shapes have opposite phases.