Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2003-01-15
2004-11-02
Meier, Stephen (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S014000, C347S012000, C347S006000, C347S005000
Reexamination Certificate
active
06811241
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid jetting head capable of ejecting various kinds of liquid in the form of droplets for use in an ink jet recording apparatus, a display manufacturing apparatus, an electrode forming apparatus, a biochip manufacturing apparatus, etc., and particularly relates to a method and an apparatus for measuring the natural vibration period concerning liquid stored in a pressure chamber, and a liquid jetting apparatus in which the waveform of a drive signal is established on the basis of the determined natural vibration period.
As a liquid jetting apparatus having a liquid jetting head capable of ejecting liquid in the form of a liquid droplet, for example, there has been proposed an image recording apparatus in which ink droplets are ejected to record an image or the like on recording paper, an electrode forming apparatus in which an electrode material in a liquid form is ejected onto a substrate to thereby form electrodes, a biochip manufacturing apparatus in which biological samples are ejected to manufacture biochips, or a micropipette for ejecting a predetermined amount of a sample into a vessel.
To eject a liquid droplet, the liquid jetting head uses a change of pressure in the liquid stored in the pressure chamber. In the liquid jetting head, pressure vibration is excited in the liquid in the pressure chamber with the change of pressure as if the inside of the pressure chamber were an acoustic tube. The period of the pressure vibration is also called a natural vibration period because it is fixed for each kind of liquid jetting head. Then, the natural vibration period can be varied among liquid jetting heads belonging to one and the same kind. This is because there occurs a variation in dimensions or setting accuracy of parts constituting the liquid jetting heads. In accordance with the variation of the natural vibration period, there occurs a variation in droplet ejecting properties such as droplet ejecting amount or flight velocity. This is because the change of liquid pressure differs in accordance with the natural vibration period when the heads are driven by one and the same drive signal, so that there occurs a difference in position or moving speed of a meniscus (free face of liquid exposed in the nozzle orifice) at the time of liquid droplet ejection.
Under such circumstances, there has been proposed an apparatus for measuring the natural vibration period of a liquid jetting head and controlling waveform elements forming a drive signal on the basis of the result of the measurement. Various methods for measuring the natural vibration period have been proposed. However, the productivity will be lowered if it takes long time to measure the natural vibration period. Taking this point into consideration, a method has been proposed in which three kinds of evaluation pulses set to have different time intervals between an excitation signal and an ejection signal are used to classify liquid jetting heads into a plurality of Tc ranks based on liquid ejection amounts corresponding to the respective evaluation pulses (for example, disclosed in Japanese Patent Publication No. 2002-154212A). In this related-art method, it will be sufficient if the ejected liquid amount is measured three times for one liquid jetting head. Accordingly, the work of measurement can be carried out efficiently. Thus, this method is suitable to mass production.
However, in order to further improve the productivity, it is necessary that the measurement of the natural vibration period is made more efficient. In addition, in order to control the amount or the flight velocity of an ejected droplet with higher accuracy, it is desired that the natural vibration period of a liquid jetting head itself is measured.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to make the measurement of the natural vibration period more efficient while improving the measuring accuracy of the natural vibration period. It is also one object of the invention to control the amount or the flight velocity of an ejected droplet with higher accuracy.
In order to achieve the above objects, according to the invention, there is provided a method of measuring a natural vibration period of a liquid jetting head provided with a nozzle orifice, a pressure chamber communicated with the nozzle orifice, a liquid supply port which supplies liquid into the pressure chamber, and a pressure generation element which causes pressure fluctuation in the liquid contained in the pressure chamber, the method comprising steps of:
providing a first evaluation signal including a first excitation element adapted to excite pressure fluctuation in liquid contained in the pressure chamber and a first ejection element which follows the excitation element after a first time period to eject a first liquid droplet from the nozzle;
providing a second evaluation signal including a second excitation element adapted to excite pressure fluctuation in liquid contained in the pressure chamber and a second ejection element which follows the excitation element after a second time period to eject a second liquid droplet from the nozzle, which is longer than the first time period;
supplying the first evaluation signal to the pressure generating element to measure a first ejected amount of the first liquid droplet;
supplying the second evaluation signal to the pressure generating element to measure a second ejected amount of the second liquid droplet;
calculating an ejected amount ratio of the first ejected amount and the second ejected amount; and
determining the natural vibration period of the liquid jetting head based on the ejected amount ratio.
According to the invention, there is also provided an apparatus for measuring a natural vibration period of a liquid jetting head provided with a nozzle orifice, a pressure chamber communicated with the nozzle orifice, a liquid supply port which supplies liquid into the pressure chamber, and a pressure generation element which causes pressure fluctuation in the liquid contained in the pressure chamber, the apparatus comprising:
a first evaluation signal generator, which generates a first evaluation signal including a first excitation element adapted to excite pressure fluctuation in liquid contained in the pressure chamber and a first ejection element which follows the excitation element after a first time period to eject a first liquid droplet from the nozzle;
a second evaluation signal generator, which generates a second evaluation signal including a second excitation element adapted to excite pressure fluctuation in liquid contained in the pressure chamber and a second ejection element which follows the excitation element after a second time period to eject a second liquid droplet from the nozzle;
a first evaluation signal supplier, which supplies the first evaluation signal to the pressure generating element to measure a first ejected amount of the first liquid droplet;
a second evaluation signal supplier, which supplies the second evaluation signal to the pressure generating element to measure a second ejected amount of the second liquid droplet;
a calculator, which calculates an ejected amount ratio of the first ejected amount and the second ejected amount; and
a natural vibration period determinant, which determines the natural vibration period of the liquid jetting head based on the ejected amount ratio.
In the above configuration, since it will be sufficient if the amount of liquid is measured twice for one liquid jetting head, it is simple and easy to support the automation of a manufacturing line. It is therefore possible to manufacture liquid jetting heads without reducing the productivity. Thus, the invention is suitable to mass production. Further, since there is a high correlation between the natural vibration period and the ejected amount ratio the natural vibration period of a liquid jetting head subjected to the measurement can be determined with high accuracy.
Preferably, the method further comprises steps of:
providing a plurality of
Hosono Satoru
Niishida Keisuke
Takahashi Tomoaki
Tanaka Ryoichi
Teramae Hirofumi
Meier Stephen
Seiko Epson Corporation
Stewart, Jr. Charles
Sughrue & Mion, PLLC
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