Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2000-07-21
2001-11-06
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S010000, C347S069000
Reexamination Certificate
active
06312080
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a droplet deposition apparatus.
DESCRIPTION OF RELATED ART
Ink jet printers include an ink actuator for ejecting droplets of ink liquid on demand. Such an ink actuator is disclosed in U.S. Pat. No. 5,016,028. The actuator includes a plurality of channels having side walls which are displaceable in response to electric drive signals. When an electric drive signal is applied to a section of the wall, the wall will move, thereby causing the volume of corresponding channels to increase or decrease.
U.S. Pat. No. 4,275,402 describes a circuit arrangement for piezoelectric recording nozzles with control circuits providing control voltages to individual nozzles. A regulating circuit includes a temperature-dependent resistor sensing the environmental temperature to effect temperature regulation of the control voltages in accordance with the environmental temperature.
U.S. Pat. No. 5,631,675 describes an apparatus for driving an ink jet recording head having piezoelectric units which expand and contract as controlled by an electric field applied thereto. The apparatus according to U.S. Pat. No. 5,631,675 includes two constant current sources which operate to charge and discharge a capacitor. The voltage of the capacitor is amplified to provide the voltage for driving the piezoelectric units.
SUMMARY
A problem to which the present invention is directed is to improve print performance and increase the life time of the actuator.
This problem is addressed by providing a droplet deposition apparatus including:
an ink actuator having a plurality of spaced walls defining ink channels, said walls having opposed sides; said opposed sides being provided with electrodes being adapted to receive electric signals to deform said walls to cause ink in said channels to be ejected therefrom;
a control unit including a plurality of current sources for defining the wave forms of said electric signals;
a temperature sensor for generating an amplitude control signal in response to a sensed actuator temperature;
a power supply for providing a drive voltage to the control unit; said drive voltage having a voltage amplitude;
the power supply having means for adjusting the amplitude of the drive voltage in response to the amplitude control signal; wherein
said power supply is separated in space from said control unit and from said actuator and in that said electric signals include a controlled current.
This solution advantageously leads to reduced operating temperature of the actuator, and to an improved quality of the ejected ink. Since a high operating temperature leads to an accelerated ageing process of the ink in and near the actuator, which in turn leads to deteriorating print quality, this solution results in improved print quality. This solution provides particular improvement in print quality for printing conditions when the droplet deposition apparatus is turned on and operable for long times, but with small amounts of actual printouts. In such cases some ink remains in the actuator for long time periods before being deposited. With a droplet deposition apparatus as defined above, the heat generated by the power supply means is prevented from being transported to the actuator. Whereas an ink volume in the actuator of a prior art apparatus is kept warm for long time durations, such warming is avoided in a droplet deposition apparatus according to the above embodiment of the invention.
REFERENCES:
patent: 4275402 (1981-06-01), Kern
patent: 0 641 656 (1994-09-01), None
patent: 0 778 132 (1996-12-01), None
Boström Christer
De Roos Mike
Barlow John
Dudding Alfred
Fay Sharpe Fagan Minnich & McKee LLP
XaarJet AB
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