An ink-jet recording apparatus wherein the ink jet is issued from an ink head or manifold and broken into drops. The selected ink drop is charged and made to pass through a first deflection means which deflects the charged ink drop in two mutually perpendicular directions, one being in parallel with a main scanning direction while the other being perpendicular to said direction. After leaving the first deflection means, the charged ink drop passes through a second deflection means which can cancel or nullify the deflection of the charged drop in said other direction, leaving the charged drop subject to the deflection in said main scanning direction so as to be steered to a predetermined point on a recording medium. The ink drops which are not used are not charged and travel a straight trajectory so as to be trapped by a gutter between the first and second deflection means.

BACKGROUND OF THE INVENTION 
The present invention relates to an ink-jet recording apparatus and more 
particularly a multiple-ink-jet recording apparatus having an array of 
print head units so that ink dots in one line may be printed 
simultaneously. 
There have been well known in the art various types of the multiple-ink-jet 
printers. In one type a continuous ink jet is issued from a nozzle of an 
ink head or manifold and breaks up into drops. The ink drop which is used 
or printed is charged at the instant when it is formed, and the charged 
drop is deflected by a pair of deflection electrodes by an amount 
proportional to its charge and strike a recording medium. The ink drops 
which are not used or printed are not charged so that they travel along a 
straight trajectory and are trapped for recirculation by a gutter disposed 
behind the deflection electrodes. 
Gutters must be provided for respective print head units and must be 
located in the ink drop trajectories so as to trap the unused and 
uncharged ink drops traveling the straight trajectories. As a result, each 
print head unit cannot print an ink dot at a point on a recording medium 
just behind its gutter by its own ink drop. Therefore in order to print 
the spot just behind the gutter, the adjacent print head unit must deflect 
the charged ink drop at a large angle so that the deflected ink drop may 
be placed correctly at that spot. However, in practice it is very 
difficult to deflect the charged drop at a large angle with a high degree 
of accuracy so that the deflected ink drop may be correctly placed at the 
very spot behind the gutter without merging with the adjacent ink dots. 
SUMMARY OF THE INVENTION 
One of the objects of the present invention is therefore to provide a 
multiple-ink-jet recording apparatus in which each of print head units may 
print an ink dot at a point on a recording medium just behind of a gutter 
which may be located at any suitable position. 
Another object of the present invention is to provide a single- or 
multiple-ink-jet recording apparatus in which each print head unit has a 
first deflection means for deflecting the charged ink drop in two mutually 
perpendicular directions, one being in parallel with a main scanning 
direction while the other being in the direction perpendicular to that 
direction, and a second deflection means for cancelling or nullifying the 
deflection in said other direction. 
According to one aspect of the present invention, the first deflection 
means comprises two pairs of horizontal and first vertical deflection 
electrodes and the second deflection means comprises a pair of second 
vertical deflection electrodes which are impressed with a vertical 
deflection voltage equal in magnitude but opposite in direction to that 
applied to the first vertical deflection electrodes. A gutter is located 
between the first and second deflection means in the straight trajectory 
of the ink drop. When the charged ink drop passes through the first 
deflection means, it is deflected not only in the horizontal direction so 
that it may be placed at a predetermined point on a recording medium but 
also in the vertical direction to such an amount as to be able to jump 
over the gutter if the gutter is in the vertically undeflected trajectory. 
When the charged ink drop passes through the second deflection means, its 
vertical deflection is cancelled or nullified by the vertical deflection 
in the same amount but in the opposite direction so that the charged ink 
drop seems to have been deflected only in the horizontal direction without 
being deflected in the vertical directions. Thus the ink drops may be 
placed at any points on the recording medium which are in the shadow of 
the gutter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Prior Art, FIG. 1 
Prior to the description of the preferred embodiments of the present 
invention, the print head of a prior art ink-jet printer will be described 
briefly in order to more specifically point out the problems thereof. In 
general, the print head comprises a plurality of print head units each 
comprising an ink head or manifold 1 from which the steam of ink drops is 
issued, a charge electrode 2 for charging the ink drops in response to the 
video signals, a detection electrode 3 for detecting the passage of the 
ink drops therethrough, a pair of deflection electrodes 4 for deflecting 
the charged ink drops in the horizontal direction and a gutter 6 for 
trapping the unused and uncharged ink drops for recirculation. When the 
charged ink drop passes through the deflection electrodes 4, to which is 
applied a DC voltage, it is deflected by an amount in proportion to a 
charge which is acquired to be steered to strike a recording paper 5 which 
is transported in the vertical direction, thereby leaving an ink dot at a 
predetermined position. The uncharged ink drops which are not used are not 
deflected by the deflection electrodes 4 so that they follow the straight 
trajectory and are trapped by the gutter 6 located between the deflection 
electrodes 4 and the recording paper 5. 
However in the multiple-ink-jet print head, the gutters 6 must be provided 
in number equal to the nozzles or ink heads or manifolds 1. As a result, 
the ink drops cannot reach the places on the recording paper 5 just in the 
shadows of the gutters 6 so that when it is desired to draw a continuous 
line segment, each print head unit must place an ink drop at the spot on 
the recording paper 5 just in the shadow of the gutter 6 of the adjacent 
print head unit. As a consequence, the angle of deflection of the ink drop 
must not only be increased but also maintained with a higher degree of 
accuracy so that the merging of the adjacent ink drops may be avoided. 
The Invention, First Embodiment, FIGS. 2-5 
Referring to FIGS. 2, 3 and 4, the print head of a first embodiment of the 
present invention has an ink head or manifold 11, a charge electrode 12 
and a detection electrode 13, the functions of all of which are described 
above. The print head further includes a pair of horizontal deflection 
electrodes 14, a pair of first vertical deflection electrodes 15 and a 
pair of second vertical deflection electrodes 16. The horizontal 
deflection electrodes 14 and the first vertical deflection electrodes 15 
constitute a first deflection means and are applied with the DC deflection 
voltages Vx and Vy, respectively. The second vertical deflection 
electrodes 16 which is a second deflection means is applied with the 
deflection voltage Vdy equal in magnitude to but opposite in direction to 
the vertical deflection voltage Vy applied to the first vertical 
deflection electrodes 15. 
When the ink drop which is to be used; that is, the ink drop charged by the 
charge electrode 12 passes through the electrostatic fields established by 
the horizontal deflection electrodes 14 and the first vertical deflection 
electrodes 15, it is subjected to the horizontal and vertical components 
Fx and Fy as shown in FIG. 3 and consequently is deflected obliquely 
upwardly in the direction of the resultant force F. After leaving the 
first deflection means consisting of the electrodes 14 and 15, the ink 
drop passes the electrostatic field established by the second deflection 
means or the second vertical deflection electrodes 16. This electrostatic 
field is opposite in direction but equal in strength to that established 
by the first vertical deflection electrodes 15 so that the charged ink 
drop is deflected downwards as best shown in FIG. 2. This means that the 
upward deflection of the charged ink drop by the first vertical deflection 
electrodes 15 is cancelled by the downward deflection by the second 
vertical deflection electrodes 16. As a result the charged ink drop 
travels along the curved trajectory indicated by the broken lines A in 
FIGS. 2 and 4 and strikes the recording paper 10. 
The ink drop which is not used is not charged so that it travels along the 
straight trajectory B shown in FIG. 2 or 4. Therefore, the gutter 19 may 
be positioned at such a height as to trap the uncharged ink drops 
traveling straight as best shown in FIG. 2. As a result, the accuracy 
imposed on the position of the gutter 19 may be considerably tolerated. 
As with the conventional ink-jet process, the horizontal deflection is 
controlled by varying the voltage applied to the charge electrode 12, 
thereby varying the charge on the ink drop in response to the signal. As 
to the horizontal deflections, the binary or on-off control becomes 
possible. 
As shown in FIG. 5, a plurality of the print head of the type described may 
be assembled as the print head units into a horizontal array to provide a 
multiple-ink-jet print head capable of printing the whole horizontal line 
simultaneously. The first and second vertical deflection electrodes 15 and 
16 and the gutter 19 may be shared in common by all the print head units. 
Second Embodiment, FIGS. 6 through 8 
In FIGS. 6 and 7 is shown a second embodiment of the present invention. 
While in the first embodiment the first deflection means comprises a pair 
of horizontal deflection electrodes and a pair of first vertical 
deflection electrodes, in the second embodiment the first deflection means 
comprises only one pair of deflection electrodes 17 inclined at an angle 
relative to the two directions or axes perpendicular to each other so that 
the force F to which the charged ink drop is subjected when passing 
through the electrostatic field established by the deflection electrodes 
17 may be resolved into the horizontal and vertical components Fx and Fy, 
respectively, as shown in FIG. 7. Therefore the second vertical deflection 
electrodes 18 are impressed with such a deflection voltage that the 
vertical component Fy may be cancelled. 
As with the first embodiment, a plurality of the print heads of the type 
shown in FIG. 6 may be assembled into a horizontal array to provide a 
multiple-ink-jet print head capable of printing the whole horizontal line 
simultaneously. The second vertical deflection electrodes 18 and the 
gutter 19 may be shared in common by all the print head units. 
In FIG. 9 is shown a block diagram of a control circuit of the print head 
consisting of 60 units spaced apart from each other by 5 mm, the print 
head being capable of printing one horizontal line with the dot density of 
8 dots/mm. Each print unit is capable of deflecting the charged ink drops 
at one of 40 discrete deflection angles. 
An exciting clock signal generator 21 generates the exciting clock signal 
C.sub.1 which is transmitted through a sinusoidal-wave shaping and 
amplification circuit 22 to the electromechanical transducers (not shown) 
mounted on the ink heads or manifolds 11. Video signals S are synchronized 
with the clock signals C.sub.2 and stored in a shift register 23 
consisting of 2400 stages (60.times.40) for each line. The output signals 
E.sub.1 through E.sub.60 from the detection electrodes 13 are applied to 
phase detection circuits 24.sub.1 through 24.sub.60 each of which is 
responsive to the detection signal B for detecting the phase at which the 
ink jet breaks off into ink drops and transmits to its corresponding 
charge circuit 25 the output signal representative of an optimum phase. 
After the phase detection, the shift register 23 is switched to the clock 
which is in synchronism with the exciting clock signal C.sub.1 from the 
exciting clock signal generator 21 so that its contents are read out from 
the output terminals each provided for every 40 stages and are applied to 
the charge circuits 25.sub.1 through 25.sub.60. Each charge circuit 25 in 
turn applies the charge signal V to its corresponding charge electrode 12. 
The charge signal V has a voltage selected from 40 stepped voltages 
between 55 and 250 V and has a pulse waveform whose center coincides with 
an optimum phase. 
According to the present invention, when the charged ink drop passes 
through the first deflection means it is deflected both in the horizontal 
and vertical directions, but when it passes through the second deflection 
means the vertical deflection is cancelled as described above. That is, 
the charged ink drops are deflected twice in the vertical directions in 
order to jump the gutter 19 and reach the spot just in the shadow of the 
gutter 19. Therefore after having passed through the second deflection 
means, the charged ink drop is deflected only in the horizontal direction 
at one of 40 discrete deflection angles. After one line consisting of 2400 
dots has been printed, the recording paper or the multiple-ink-jet print 
head is moved vertically relative to each other. This printing procedure 
is repeated until all the test is printed. 
In summary, according to the present invention it is not needed to provide 
a gutter for each print head unit and instead only one common gutter may 
be provided. The charged ink drops may jump the common gutter by two 
vertical deflections so that the charged ink drops may be deflected freely 
in the horizontal direction. In addition, the multiple ink jet print head 
can print all dots in one line simultaneously so that the ink-jet 
recording apparatus of the present invention may be used as the copies of 
facsimiles. Furthermore, the horizontal and vertical deflection voltages 
may be suitably selected independently of each other so that the 
horizontal deflection will not be adversely affected by the vertical 
deflections and consequently the horizontal deflection angles may be 
controlled with a higher degree of accuracy.