Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1997-10-02
2003-04-29
Hallacher, Craig (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S086000
Reexamination Certificate
active
06554380
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid detection method and a liquid discharging device in which, in an ink-jet recording head used in a liquid discharging apparatus for recording (printing) characters and/or images by discharging ink droplets, a mechanism for detecting the remaining amount of ink within an ink tank for supplying ink to be discharged, and for determining continuity of ink from the ink tank to a portion near a discharging port, i.e., “disconnection of ink”, is provided.
Recording (printing) is not necessarily performed on paper, but ink may be provided onto a recording medium such as cloth, string, film material, leather, metal, glass or the like.
More particularly, the present invention relates to a mechanism for detecting the state of ink used for recording in an ink tank for accommodating the ink, an ink channel for supplying a recording head with the ink, or a portion near a discharging port for discharging the ink.
2. Description of the Related Art
Recording apparatuses which utilize an ink-jet method of performing recording by discharging ink onto a recording material have been widely used due to ease of use.
An ink-jet recording apparatus includes an ink-jet head for discharging ink droplets, and an ink tank for accommodating ink to be supplied to the ink-jet head. The ink-jet head includes discharging ports for discharging the ink. A discharging-energy generation element for discharging the ink is provided near each of the discharging ports. A heating element for applying thermal energy to ink, a piezoelectric element for discharging ink by providing a mechanical pressure thereto, or the like is used as the discharging-energy generation element. The ink tank communicates with the discharging ports via an ink channel.
In the ink-jet recording apparatus, when ink within the ink tank decreases to a certain level, the ink cannot be supplied to the ink-jet head, so that normal discharge is disturbed and recording cannot be performed. Accordingly, in the ink-jet recording method, it is effective to provide a mechanism for detecting the remaining amount of ink and the absence of ink.
For example, the following methods for detecting the remaining amount of ink and a decrease in the remaining amount of ink have been known.
1. A method of detecting electric resistance and a state of conduction between two electrodes provided within the ink tank.
2. A method in which the ink tank is formed by a transparent material, an optical sensor is provided in the vicinity of the ink tank, and the presence of ink within the ink tank is detected by detecting the amount of light transmitted through the ink tank, or the amount of light reflected from a portion toward which the light is projected.
In order to detect the remaining amount of ink and a decrease in the remaining amount of ink, methods of detecting the presence of ink near the discharging ports have also been proposed. For example, the following method is disclosed in U.S. Pat. No. 4,853,718.
3. A method of detecting the electric resistance or the electrostatic capacitance between two electrodes provided in the vicinity of the discharging ports.
However, in method (1), in a recording apparatus in which the ink tank is exchanged by being separated from the head, when the remaining amount of ink in the ink tank becomes very small and the ink tank is replaced by a new ink tank, a portion relating to detection means, such as electrodes and the like, is also simultaneously replaced, thereby increasing the production cost of the ink tank, and the operating cost of the apparatus.
In method (2), a misoperation tends to occur due to stains on the surface of the ink tank or ink droplets adhered to the inner wall of the ink tank. In addition, a misoperation tends to occur in an ink tank having a light color, such as yellow.
In method (3), only ink near the discharging ports is detected, so that it is impossible to detect whether or not ink can be continuously supplied from the ink tank to the discharging ports, or the amount of ink within the ink tank.
When supplying ink from the ink tank to a discharging port of the ink-jet head, a bubble, in some cases, generates and grows in the liquid channel to the discharging port. When the bubble moves in accordance with the flow of ink and reaches the vicinity of the discharging port, the discharging port is filled with the bubble, even though the ink is present within the ink so as, to hinder the supply of the ink to the discharging port, thereby providing a state in which the ink is not discharged from the ink-jet head (this state will be hereinafter termed “nondischarge”). During a printing operation, a recording dot corresponding to the discharging port where nondischarge has occurred is not recorded (this state will be hereinafter termed “dot missing”) thereby causing a failure in recording. Such a failure in recording causes degradation in the image quality. In addition, if it is necessary to perform another printing operation, a loss of time and useless consumption of an additional recording medium result. In addition, the element for generating the discharging energy of the ink-jet head may be forced to continuously generate the discharging energy in the of absence ink, thereby causing, in some cases, destruction of the element. Such a phenomenon in which the communication of ink from the ink tank to the discharging port is disconnected due to a bubble or the like is termed “disconnection of ink”.
Such “disconnection of ink” cannot be detected according to the above-described methods (1), (2) and (3).
In order to prevent “disconnection of ink”, a method is considered, in which a recovery operation of sucking ink from the discharging port is automatically performed before recording or at a periodic timing. In this method, however, since an operation of sucking ink is performed even in the absence of disconnection of ink, the amount of consumption of ink which does not contribute to recording increases if ink is frequently sucked in order to prevent disconnection of ink, resulting in an increase in the operating cost per sheet. This method also results in an increase in the size of a unit for storing sucked ink, thereby hindering attempts to produce a small and light ink jet recording apparatus.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above-described problems.
It is an object of the present invention to provide a liquid detection method and a liquid discharging device capable of detecting whether or not a liquid can be supplied from a tank for accommodating the liquid to each discharging port of a recording head in a case that a liquid channel from the tank to each discharging port is not disconnected by a bubble.
It is another object of the present invention to provide a liquid detection method and a liquid discharging device capable of detecting the remaining amount of a liquid within a tank for accommodating the liquid and a state in which the remaining amount of the liquid, is very small.
The present invention which achieves these objectives relates to a liquid detection method in a configuration including a tank for accommodating a liquid, and a recording head for discharging the liquid supplied from the tank via a liquid channel from discharging ports onto a recording medium. The method includes the steps of inputting a voltage having a predetermined waveform to a first electrode provided at a portion near the discharging ports, detecting a waveform of a voltage generated at a second electrode provided at a portion near the tank, and determining a presence of the tank, the remaining amount of the liquid within the tank, or continuity of the liquid from the tank to a portion near the discharging ports based on the detected waveform of the voltage.
In one embodiment, the liquid is an ink having a coloring component for the recording medium, or a liquid having a component which has electric conductivity.
In another embodiment, the first electrode contacts the liquid, and the second el
Moriyama Jiro
Uchikata Yoshio
Canon Kabushiki Kaisha
Fitzpatrick, Cella, Harper & Scninto
Hallacher Craig
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