Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-11-05
2001-05-01
Beatty, Robert (Department: 2852)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06224197
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a liquid jet recording apparatus wherein recording is effected by ejecting droplets of liquid through an ejection outlet, using thermal energy.
PRIOR ART
In a liquid jet recording apparatus using thermal energy, an electro-thermal transducer is used to eject droplets of the liquid. The thermal energy produced thereby is effective to vaporize the liquid and form a bubble, by which a pressure is produced to eject the liquid in the form of a droplet.
Such a system is advantageous because, among other reasons, the ejection outlets can be disposed at a high density so that high resolution images can be recorded.
The high density arrangement, however, requires narrow liquid passages communicating with the ejection outlets. The narrow passages have higher inertance and impedance, which requires a longer time period for the liquid to refill the passage from the liquid supply side. This prevents increase of the recording speed.
By the reduction of the length of the passage, the refilling time period can be reduced. If, however, this is done, the speed and the volume of the ejected liquid reduces, with the result that the stable recording is not possible.
Japanese Laid-Open Pat. Application No. 204352/1985 proposes, in an attempt to solve this problem to stabilize the liquid ejection with the short passage, that an ink jet recording head has a resistance to reduce flow of the liquid in the passage to the supply side from the electro-thermal transducer.
Japanese Laid-Open Pat. Application No. 87356/1989 proposes, in an attempt to increase a percentage of the energy of the bubble contributable to the ejection of the liquid, that the cross-sectional area of the passage adjacent the electro-thermal transducer increases toward the ejection outlet.
Japanese Laid-Open Pat. Application No. 195050/1989 proposes that the top wall of the passage is made higher in the neighborhood of the electro-thermal transducer than the other portion so that the liquid passage is not blocked by the bubble width (U.S. Pat. No. 4,410,899).
In the system disclosed in Japanese Laid-Open Pat. Application No. 204352/1985, there arise the following problems:
(1) the difficult in the provisions of the resistances in the passages increases with the increase of the density of the nozzles and with the increase of the number of the ejection outlets of the recording apparatus.
(2) If the resistance is too remote from the electro-thermal transducer, the effects of the resistances reduces; and if it is too near, the produced bubble develops to the clearance between the wall of the passage and the resistance with the result of the reduction of the effects of the resistances.
Therefore, the optimum design of the configuration, dimension and position or the like is difficult, and even if the optimum design is made, the effects are not sufficient.
The method disclosed in Japanese Laid-Open Pat. Application No. 87356/1989 involves a problem that the multi-nozzle structure is difficult, although the energy use efficiency is improved. In this method, the cross-sectional area of the passages is increased toward the ejection side with the result of the thin wall between the adjacent passage. If the wall is too thin, the strength may become insufficient, or the pressure of the bubble is transmitted to the adjacent passages, and therefore, the proper ejection is expected. For these reasons, the method is not suitable to increase the high density arrangement or to increase the number of the nozzles.
According to the arrangement disclosed in the Japanese Laid-Open Pat. Application No. 95050/1989, the liquid passage is not blocked by the bubble, and therefore, the liquid can be sufficiently supplied, so that the ejection is stabilized. However, the publication simply states that the top wall of the passage is made higher at the energy applying portion than the other portion.
SUMMARY OF THE INVENTION
Accordingly, it is a principal object of the present invention to provide a liquid jet recording head having plurality ejection outlets disposed at a high density.
It is another object of the present invention to provide a liquid jet recording head capable of ejecting a liquid droplet at a high speed.
It is a further object of the present invention to provide a liquid jet recording head capable of ejecting a liquid droplet having a sufficient volume.
It is a further object of the present invention to provide a liquid jet recording head capable of refilling the ejected liquid at a high speed.
It is a further object of the present invention to provide a liquid jet recording head wherein an impedance at the side downstream of a pressure producing portion in a liquid passage is different from that of the upstream side with respect to the flow of the liquid upon the liquid ejection, in consideration of the liquid flow upon ejection and during refilling liquid supply.
According to an embodiment of the present invention, the degree of width reduction is higher toward the ejection outlet than toward the supply inlet. That is, in a simple structure wherein the reductions toward the ejection outlet and the supply inlet are rectilinear, the inclination of the walls constituting the passage wall is higher toward the ejection outlet then toward the supply inlet.
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Hawkins et al; Sideshooter with High Frequency Response; Xerox Disclosure Journal, V14, No. 3, May/Jun. 1989, pp. 105-107.
Hirasawa Shin'ichi
Tachihara Masayoshi
Beatty Robert
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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