U.S. patent number 3,914,772 [Application Number 05/409,722] was granted by the patent office on 1975-10-21 for ink jet type printing device.
This patent grant is currently assigned to Casio Computer Co., Ltd.. Invention is credited to Toshio Kashio.
United States Patent |
3,914,772 |
Kashio |
October 21, 1975 |
Ink jet type printing device
Abstract
An ink jet type printing device is adapted to jet ink droplets
from a nozzle to print a character, pattern etc. on a recording
medium. The device includes a high tension generator connected to
the nozzle to supply electric charges to an ink to be jetted and a
heat sensitive element arranged in the neighborhood of the nozzle
to detect the temperature change of ink which causes the resistance
of the heat sensitive element to be varied to permit an output
voltage of the high tension generator to be variably controlled,
thereby making the size of the ink droplets uniform for accurate
printing.
Inventors: |
Kashio; Toshio (Tokyo,
JA) |
Assignee: |
Casio Computer Co., Ltd.
(Higashiyamato, JA)
|
Family
ID: |
14450734 |
Appl.
No.: |
05/409,722 |
Filed: |
October 25, 1973 |
Foreign Application Priority Data
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|
|
|
|
Oct 27, 1972 [JA] |
|
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47-107111 |
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Current U.S.
Class: |
347/82;
347/14 |
Current CPC
Class: |
B41J
2/072 (20130101); B41J 2/03 (20130101) |
Current International
Class: |
B41J
2/015 (20060101); B41J 2/07 (20060101); B41J
2/03 (20060101); G01D 015/18 () |
Field of
Search: |
;346/75,140 |
References Cited
[Referenced By]
U.S. Patent Documents
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|
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3653932 |
April 1972 |
Berry et al. |
3761953 |
September 1973 |
Helgeson et al. |
3787882 |
January 1974 |
Fillmore et al. |
|
Primary Examiner: Hartary; Joseph W.
Attorney, Agent or Firm: Flynn & Frishauf
Claims
What is claimed is:
1. An ink jet type printing device for ejecting ink droplets of
substantially uniform size, comprising:
a high voltage generator (20);
a nozzle (11);
means for supplying ink to said nozzle at substantially constant
pressure;
means coupled to said high voltage generator and responsive to the
high voltage supplied from said high voltage generator for creating
an electrostatic force in the vicinity of said nozzle for causing
ink particles to be ejected from said nozzle under the influence of
said electrostatic force at substantially constant ink pressure so
as to record characters, patterns, etc. on a recording medium;
a heat sensitive element (25) disposed adjacent to said nozzle (11)
to detect the temperature of the ink supplied to said nozzle and
for generating a detection output; and
control means (40) variably controlling the output voltage from the
high voltage generator (20) as a function of the detection output
of said heat sensitive element (25), which detection output
represents the ambient temperature of the ink supplied to said
nozzle (11).
2. An ink jet type printing device according to claim 1 wherein
said heat sensitive element comprises a variable resistance
element, the resistance of which varies with the temperature
thereof, said control means variably controlling the output voltage
from the high voltage generator as a function of the resistance of
said heat sensitive element.
3. An ink jet type printing device according to claim 2 wherein the
resistance of said heat sensitive element decreases with a rise in
temperature and increases with a drop in temperature.
4. An ink jet type printing device according to claim 1 wherein
said control means comprises a constant voltage circuit, the
constant voltage output of which is a function of the detection
output of said heat sensitive element.
5. An ink jet type printing device according to claim 4 wherein
said high voltage generator comprises a DC-DC converter, the input
of which is connected to the output of said control means whereby
when the constant voltage output of said control means decreases,
the high voltage output of said high voltage generator decreases,
and when the constant voltage output of said control means
increases, the high voltage output of said high voltage generator
increases.
Description
BACKGROUND OF THE INVENTION
This invention relates to an improved ink jet type printing device
adapted to effect an accurate printing by making uniform the size
of ink droplets jetted from a nozzle.
An ink jet type printing device is adapted to print characters etc.
on a recording paper by jetting ink droplets from a nozzle having
an inner diameter of about 100 .mu. and deflection controlling
them. In this case, the ink jetting is controlled by an ink feeding
pressure relative to the nozzle and a potential difference applied
in the ink jetting direction. An accelerating plate is disposed
between the nozzle and a platen on which a recording paper is
carried. For example, a high voltage is applied between the
accelerating plate and the nozzle to impart electric charge to an
ink present in the nozzle and ink droplets are jetted, under the
attraction of the accelerating plate, in the direction of a
recording paper carried on a platen connected at the same potential
as that of the accelerating plate. Then, the ink droplets are
deflection controlled through deflection electrodes and a desired
character is printed on a recording paper. To print an accurate
character, pattern etc. on the recording paper it is required that
the size of ink droplets jetted from the nozzle be made uniform. If
the ink feeding pressure is kept constant, the size of ink droplets
corresponds to the number of ink particles (ink jetting frequency)
jetted per unit time and the ink jetting frequency is influenced by
the viscosity of ink and the voltage applied to the nozzle. The
viscosity of ink is varied by the temperature of ink prevalent in
the nozzle, and a relation between the temperature and the ink
jetting frequency is such that, as shown in FIG. 2, the number of
ink droplets to be jetted per unit time i.e. the ink jetting
frequency is increased with a rise in temperature of ink. As a
result, the size of ink droplets is made smaller in proportion to
the raise of the ink jetting frequency and the ink particle is
strongly subjected to an action by the deflection electrode to
increase its deflection angle, failing to print an accurate
character etc. on a recording paper.
It is accordingly the object of this invention to provide an ink
jetting type printing device which is capable of controlling any
temperature variation of ink present in a nozzle due to ambient
temperature to permit ink droplets of uniform size to be jetted
from the nozzle which and is free from the variation of
concentration of ink due to a temperature change, so that an
accurate character etc. is printed on a recording paper.
SUMMARY OF THE INVENTION
The object of this invention can be achieved by providing an ink
jet type printing device comprising an ink jetting nozzle, a high
voltage generator for applying electric charges to an ink to be
jetted from the nozzle, a heat sensitive element for detecting the
temperature of ink present in the nozzle and a control section for
controlling an output voltage of the high tension generator in
response to the output of the heat sensitive element. According to
this arrangement, the variation of the viscosity of ink due to the
variation of temperature of ink present in the nozzle i.e. the
number of ink droplets jetted per unit time can be made constant.
This prevents ink droplets from being deflected to an unnecessary
extent, thus enabling an accurate character, pattern etc. to be
printed on a recording medium.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial block diagram showing one embodiment of this
invention;
FIG. 2 is a graphical representation showing a relation between the
ink jetting frequency and the temperature of ink present in the
nozzle;
FIG. 3 is a detailed circuit arrangement of a high tension
generator of FIG. 1;
FIG. 4 is a graphical representation showing a relation between the
ink jetting frequency and a voltage applied to the nozzle; and
FIG. 5 is a graphical representation showing a relation between the
temperature of ink present in the nozzle and an output voltage
impressed to the nozzle from the high tension generator when the
ink jetting frequency is made constant.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
There will be explained one embodiment of this invention by
reference to the drawings.
As shown in FIG. 1, ink is supplied from an ink tank 12 to an ink
jetting nozzle 11 by driving a pump 14 and jetted as ink droplets
17 through the orifice of the nozzle 11. A platen 16 on which a
recording paper 15 is carried is located at a predetermined
distance from the forward end of the nozzle. Deflection electrodes
18 are provided in the X-axis and Y-axis directions. An
accelerating plate 30 is arranged between the deflection electrode
18 and the forward end of the nozzle 11. An ink target 19 is
disposed in the neighborhood of the platen and adapted to introduce
ink droplets thereinto when printing is not effected. Ink present
in the ink jetting nozzle 11 is charged by application of an output
of a high voltage from a high tension (i.e., high voltage)
generator 20 connected to the nozzle. As the high tension generator
20 use may be made of a known DC-DC converter comprising a
collector tuned type oscillator 31 and a voltage doubler circuit 32
as shown, for example, in FIG. 3. The accelerating plate 30, platen
16 and ink target 19 are grounded relative to the nozzle to which
is applied a high voltage, so that a high potential difference is
created therebetween. In an input circuit of the high tension
generator 20 is provided a constant voltage circuit 40 having an
input potential control transistor 21 whose emitter terminal is
connected to the input of the high tension generator 20 and whose
collector terminal is grounded, a constant voltage diode 22, and a
comparison control transistor 23 for comparing a constant voltage
detected from the constant voltage diode 22 with an input voltage
of the high tension generator 20 to control the transistor 21. The
output of the constant voltage circuit 40 is set by the control of
a variable resistor 24.
A heat sensitive element 25 is provided in the neighborhood of the
ink jetting nozzle 11. One of the terminals of the heat sensitive
element is connected one to the input terminal of the high tension
(i.e., high voltage) generator 20 and the other to the base
terminal of the transistor 23 through a resistor.
The X-electrodes and Y-electrodes of the deflection electrodes 18
are respectively connected to a deflection circuit 41. The
deflection circuit 41 is connected through a character generator 42
to an input device 43. The character generator 42 issues, as
neccessary, a driving instruction to the pump driving circuit 13
for driving a pump 14. The detailed interrelation between the
deflection circuit 41, character generator 42 and pump driving
circuit 13 is disclosed in FIG. 2 of U.S. patent application Ser.
No. 314,999.
An ink jetting frequency corresponding to the number of ink
droplets jetted per unit time is increased with a rise in
temperature of ink present in the nozzle 11 as shown in FIG. 2,
and, as shown in FIG. 4, an increase in voltage applied to the
nozzle 11 results in an increase in the ink jetting frequency.
Therefore, the variation of the ink jetting frequency due to the
variation in temperature0105 of ink present in the nozzle can be
rectified by the control of a high tension output applied to the
nozzle from the high tension generator 20. The temperature of ink
present in the nozzle is detected by the heat sensitive element 25
arranged in proximity to, and in parallel with, the nozzle 11 as
shown in FIG. 1. The heat sensitive element 25 has one end
connected to one output terminal of the constant voltage circuit 40
and the other end connected between the resistors which are
serially connected to the variable resistor 24 of the constant
voltage circuit 40. Suppose, for example, that the temperature of
ink present in the nozzle is raised. Then, the heat sensitive
element 25 senses the rise in temperature to cause its resistive
value to be decreased to permit a base current of the transistor 23
to be increased, thereby decreasing the impedance between the
emitter and the collector of the transistor 23. Thus, the emitter
potential of the input potential controlling transistor 21 is
decreased and the input voltage of the high tension (i.e., high
voltage) generator is decreased. As a result, the output voltage
from the high tension generator 20 is decreased. When a voltage
applied to the nozzle 11 is decreased, then the ink jetting
frequency is decreased as is evident from FIG. 4. The relation
between a decrease in temperature of ink present in the nozzle 11
and decrease in output voltage is as shown in FIG. 5. Therefore,
the size of ink droplets jetted from the orifice of the nozzle 11
is controlled to be held uniform irrespective of the temperature
and the ink droplets are subject to a stable deflection through the
deflection electrode 18. This permits an accurate character to be
printed on a recording medium. Though in the above embodiment the
heat sensitive element 25 is arranged in the neighborhood of the
nozzle 11, it may be located in contact with the ink after a
sufficient insulation is effected. In a working embodiment:
a. Nozzle 11 is, for example, a glass nozzle;
b. Element 25 is a posister (Murata Seisakusho in Japan - TYPE
PTH60.T322M), positioned near the nozzle 11 within the housing of
the printer, the internal temperature within the housing being
substantially uniform throughout;
c. Pump 14 pumps ink at a constant pressure of 20 to 30 cm.
Aq.;
d. Field between plate 30 and nozzle 11 was about 2.4 kv;
e. Ink Viscosity was 3 c.p. at 20.degree.C;
f. Ink temperature was 0.degree.C to 50.degree.C;
g. Jetting frequency was 2.9 kHz at 25.degree.C (FIG. 2);
h. When temperature sensed by the posister rose to about
30.degree.C (FIG. 2), the jetting frequency would have risen to
about 3.0 kHz. However, the field voltage was decreased to about
2.6 kv which reduced the jetting frequency back to about 2.45 kHz
(FIG. 4).
This invention should not be taken in a restrictive way and it is
to be noted that this invention is capable of any modification
without departure from the spirit and scope of the invention.
* * * * *