Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-01-13
2001-07-10
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S092000
Reexamination Certificate
active
06257694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a liquid jetting device such as, for example, a humidifier for discharging water or vapor, a device for applying ink to an object and the like. More particularly, this invention relates to an ink jet printer for applying a jet of ink to a medium such as paper to be printed. Broadly, this invention is also concerned with a bubble detection circuit and method for use with such a liquid jetting device.
2. Description of the Related Art
FIG. 6
shows a conventional ink jet printer described in, for instance, Japanese Unexamined Patent Publication (Laid-Open) No. 6-336026.
In
FIG. 6
, reference numeral
1
designates a print head of the ink jet printer. This head
1
comprises a plurality of nozzles
2
, a pressure chamber
17
formed in a housing
18
, an ink path or passage
15
, piezoelectric elements (or devices)
16
a
and
16
b
for changing the capacity or volume of the pressure chamber
17
, and a heater
19
for heating the housing
18
.
Further, an ink cartridge
6
provided with an ink container
4
is mounted on the housing
18
. The ink container
4
communicates with the plurality of nozzles
2
. Moreover, porous elements
9
and
13
for absorbing and holding ink are contained in the ink container
4
. A heater
5
for heating ink is mounted on the outside surface of the ink container
4
.
Next, an operation of this conventional ink jet printer will be described hereinbelow.
Usually, the ink passage
15
is filled with ink which is in a solid state. When a voltage is applied to the heater
5
mounted on the ink container
4
and to the heater
19
provided in the head
1
, ink contained in the ink passage
15
and ink absorbed in the porous elements
9
and
13
are melted. Then, a voltage is applied to the piezoelectric elements
16
a
and
16
b
, which are in such a condition, to thereby vibrate these elements. Thus, the capacity of the pressure chamber
17
is changed, so that ink droplets are jetted out of the nozzles
2
. As a result, the ink absorbed in the porous elements
9
and
13
are gradually supplied to the pressure chamber
17
. Ink is jetted out of the head
1
by performing this operation, and is then caused to adhere to paper. Thus, printed matter is obtained.
The conventional ink jet printer has the following problem: when bubbles get into ink contained in the ink passage
15
, ink cannot be normally discharged from the plurality of nozzles
2
so that printed matter obtained is thereby streaked, thus making it impossible to provide stable and high-quality printed matter.
Moreover, the conventional ink jet printer has no means for checking the presence or absence of a bubble before printing an image and so on. Thus, the conventional ink jet printer has a problem in that there is necessity for printing a test pattern to be used for determining whether or not ink is normally discharged.
Furthermore, in the case that normal printed matter is not obtained owing to the presence of bubbles when the test pattern is printed, the conventional ink jet printer should repeatedly perform the following process. Namely, in such a case, this printer first performs an ink supply recovery or resumption operation as a recovery measure. Then, this printer prints the test pattern again so as to check whether or not ink is normally discharged. Thus, this conventional ink jet printer has another problem in that it takes much time and costs to perform such a process.
SUMMARY OF THE INVENTION
The present invention is intended to solve the aforementioned problems of the conventional ink jet printer.
Accordingly, an object of the present invention is to provide an ink jet printer which measures the impedance of a piezoelectric element of a head at an arbitrary frequency before printing, and obtains the impedance versus frequency characteristics of the element and then determines, based on the impedance versus frequency characteristics, whether or not a bubble adheres to the piezoelectric element (namely, a bubble is formed in an ink chamber), and automatically performs an ink supply recovery operation or process when a bubble adheres to the piezoelectric element, thereby removing the bubble.
Another object of the present invention is to provide an ink jet printer capable of eliminating the necessity for printing a test pattern, thereby reducing the printing time and cost.
A further object of the present invention is to provide a bubble detecting circuit and method which can detect the fact that bubbles adhere to a head.
Bearing the above objects in mind, according to one aspect of the present invention, there is provided an ink jet printer in which ink is jetted out onto a medium to be printed under the action of a piezoelectric element of a head, the printer comprising: impedance measurement means for measuring impedance of the head at frequencies within a predetermined range thereof; impedance versus frequency characteristics obtaining means for obtaining impedance versus frequency characteristics of the head based on the measured impedance; and determination means for determining, based on the impedance versus frequency characteristics, whether or not a bubble adheres to the piezoelectric element.
In a preferred form of the invention, the ink jet printer further comprises head driving means for driving the head and switching means for switching between the head driving means and the impedance measurement means.
In another preferred form of the invention, the ink jet printer further comprises means for removing a bubble adhering to the piezoelectric element when the determination means determines that the bubble adheres thereto.
In a further preferred form of the invention, the ink jet printer further comprises erasable and writable storage means for storing information representing the impedance of the head upon initialization of the printer.
Besides, according to another aspect of the present invention, there may be provided a bubble detecting circuit for use in an apparatus of jetting out liquid by driving a piezoelectric element of a head. The bubble detecting circuit comprises impedance measurement means for measuring impedance of the head at frequencies within a predetermined range thereof, impedance versus frequency characteristics obtaining means for obtaining impedance versus frequency characteristics of the head according to the measured impedance, and determination means for determining, based on the impedance versus frequency characteristics, whether or not a bubble adheres to the piezoelectric element.
Moreover, according to a further aspect of the present invention, there may be provided a bubble detecting method comprising: a measurement step of measuring impedance of a head at frequencies within a predetermined range thereof; and a determination step of obtaining impedance versus frequency characteristics of the head according to the measured impedance, and determining, based on the impedance versus frequency characteristics, whether or not a bubble adheres to the head.
Furthermore, the determination step comprises: a sub-step of obtaining the impedance versus frequency characteristics of the head according to the impedance thereof measured at the measurement step; a sub-step of performing a comparison between the impedance versus frequency characteristics obtained in this manner and predetermined impedance versus frequency characteristics; and a sub-step of determining according to the result of the comparison whether or not there is a bubble adhering to the head.
REFERENCES:
patent: 4308547 (1981-12-01), Lovelady et al.
patent: 4518974 (1985-05-01), Isayama
patent: 4973981 (1990-11-01), Bartky et al.
patent: 58-31763 (1983-02-01), None
patent: 63-166545 (1988-07-01), None
“Nozzleless Droplet Formation with Focused Acoustic Beams” by Elrod et al, J. Appl. Phys. 65(9), May 1, 1989.
Fukumoto Hiroshi
Iwashita Yoshitaka
Matsuo Hirohumi
Tokumaru Susumu
Barlow John
Hallacher Craig A.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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