Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-06-15
2001-04-17
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S094000
Reexamination Certificate
active
06217157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid discharging head and a liquid discharging apparatus for discharging liquid by bubble generation for example by thermal energy, and more particularly to a liquid discharging head and a liquid discharging apparatus utilizing a movable separation membrane which is moved by the bubble.
The present invention is applicable to a printer for recording on various recording media such as paper, yarn, fiber, fabrics, leather, metal, plastics, glass, timber, ceramics etc., a copying machine, a facsimile apparatus having a communication system, a work processor having a printer unit, and an industrial recording apparatus combined in composite manner with various processing apparatus. In the present invention, the “recording” means not only forming a meaningful image such as a character or graphics on the recording medium but also forming a meaningless image such as a pattern.
2. Related Background Art
There is already known an ink jet recording method, so-called bubble jet recording method, for providing liquid such as ink with an energy such as heat to generate a state change involving a steep volume change (generation of a bubble), causing the liquid to be discharged through a discharge opening by the force based on such state change and depositing the liquid onto the recording medium to form an image. The recording head utilizing such bubble jet recording method is generally provided, as disclosed in the Japanese Patent Publication Nos. 61-59911 and 61-59914 (corresponding to the U.S. Pat. No. 4,723,129), with a discharge opening for discharging liquid, a liquid path communicating with the discharge opening, and a heat generating member (electrothermal converting member) positioned corresponding to the liquid path and serving as energy generating means for generating energy for discharging the liquid.
Such recording method is advantageous in various manners such as being capable of printing an image of high quality at a high speed and a low noise level, printing an image of a high resolution with a compact apparatus since the discharge openings can be arranged with a high density, and obtaining a color image in a simple manner. For this reason, the bubble jet recording method is recently utilized in various office equipment such as printer, copying machine, facsimile etc. and even in certain industrial applications such as fabric printing apparatus.
On the other hand, in the conventional bubble jet recording method, as the heat generating member repeats heating in direct or indirect contact with liquid, there may be formed, on the surface of the heat generating member, a deposit resulting from scorching of the liquid. Also, in case the liquid to be discharged is easily deteriorated by heat or cannot show sufficient bubble generation, satisfactory liquid discharge may not be achieved by the bubble formation by the aforementioned heat generating member.
On the other hand, the Japanese Patent Application Laid-Open No. 55-81172 proposed a method of separating a bubble generating liquid and a discharge liquid by a flexible membrane and generating a bubble in the bubble generating liquid by thermal energy thereby discharging the discharge liquid. In the configuration of the proposed method, the flexible membrane and the bubble generating liquid are so positioned that the flexible membrane is provided in a part of the nozzle, but the Japanese Patent Application Laid-Open No. 59-26270 discloses a configuration employing a large membrane separating the entire head into an upper part and a lower part. Such large membrane, being supported between two plate members constituting the liquid path, is so provided that the liquids in the two liquid paths are not mutually mixed. Also there are known configurations giving certain feature to the bubble generating liquid itself in consideration of the bubble generating characteristics, such as the one disclosed in the Japanese Patent Application Laid-Open No. 5-229122, employing liquid of a lower boiling point than that of the discharge liquid or the one disclosed in the Japanese Patent Application Laid-Open No. 4-329148, employing electrically conductive liquid as the bubble generating liquid.
SUMMARY OF THE INVENTION
The present inventors have found a novel issue, not known in the prior art, with respect to the displacement range of the movable separating membrane. The separating membrane in the liquid discharging head of the present invention is supported between a first liquid path wall and a second liquid path wall, and the movable area for each liquid path is limited by the liquid path walls. It is thus confirmed that the first and second liquid path walls define the displacement of the membrane and have significant influence on the characteristics of the head. Therefore the present inventors have concluded that it is important to define the displacement of the membrane by the membrane itself instead of the liquid path wall to achieve smooth membrane displacement thereby maintaining the highly reliable liquid discharging characteristics.
Therefore, the present inventors have made intensive investigation in order to provide a liquid discharging head excellent in durability and stability of liquid discharging regardless of the kind of the supplied liquid, while exploiting the effect of the separating function of the separating membrane. As a result, the present inventors have tried a membrane substantially free from elongation and having a recessed portion, and found that the amount of displacement of the recessed portion corresponds to the discharge amount of the liquid. Thus, it has been found that the stable discharge can be achieved regardless of the kind of the supplied liquid by defining the displacement amount of the recessed portion, as the discharge amount corresponds to the displacement amount of the recessed portion of the separating membrane. It has also been found that the durability of the separating membrane can be improved by defining the displacement amount of the recessed portion of the separating membrane in such a manner that such recessed portion does not elongate or contract at the maximum displacement. It has furthermore been found that the refiling of the discharge liquid can be improved by utilizing the self returning force of the membrane when the recessed portion is not given energy for the displacement.
From a different standpoint, in case various liquids are used as the discharge liquid, the amount of liquid discharged from the discharge opening for example by thermal energy fluctuates depending on the kind of the liquid. Such fluctuation tends to increase with the increase in the vicsocity of the liquid. However, a method of stabilizing the discharge amount in a given liquid discharging head, by varying the discharge energy according to the kind of the supplied liquid, is complex and is difficult to practice. Consequently it is important to provide a recording head capable, with a simple structure, of realizing stable liquid discharge regardless of the kind of the supplied liquid.
An object of the present invention, attained by such intensive investigation, is to provide a novel liquid discharging head and a novel liquid discharging apparatus, capable of improving the efficiency of liquid droplet discharge, excellent in the stability and durability of discharge and stabilizing and increasing the discharged droplet volume or discharge speed.
Another object of the present invention is to improve the discharge efficiency, discharge stability and durability in the liquid discharging head provided with a first liquid path for the discharge liquid communicating with a discharge opening, a second liquid path containing the bubble generating liquid in a suppiable or movable manner and including a bubble generating area, and a movable separating membrane for separating the first and second liquid paths, having a displacement area of the movable separating membrane at the upstream side with respect to the discharge opening.
Still another
Kashino Toshio
Kudo Kiyomitsu
Shimazu Satoshi
Yoshihira Aya
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stephens Juanita
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