Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-07-30
2001-01-16
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S092000
Reexamination Certificate
active
06174049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bubble jet head arranged in opposition to a printing surface of a printing medium for ejecting an ink toward the printing surface by a pressure of a bubble, and an bubble jet apparatus employing such bubble jet head.
2. Description of the Related Art
In a bubble jet head, there are an edge shooter type and a side shooter type, in general. In the edge shooter type bubble jet head, ink ejection openings are provided on an edge portion as downstream portion with respect to heater portions as ink heating portions provided for respective of a plurality of branched ink passages for delivering an ink from an ink storage portion. On the other hand, in the side shooter type bubble jet head, the ink ejection openings are provided in opposition to the heater portions provided for respective of a plurality of the branched ink passages.
In the side shooter type bubble jet head, high work efficiency of an electrical energy to be supplied to the heater portion is achieved for relatively short distance between the ejection opening forming surface and heating surfaces of the heater portions. On the other hand, the side shooter type bubble jet head is advantageous in that even when it is left for a while without being actuated and then printing operation is resumed in such condition, possibility of ejection failure incapable of ejecting ink droplet for increased viscosity of the ink due to evaporation of volatile component contained in the ink, can be significantly reduced.
In the side shooter type bubble jet head, as disclosed in Japanese Patent Application Laid-open No. 152068/1989, for example, there has been proposed one, in which the heater portion is disposed within a receptacle portion, one end of which is opened to an ink supply passage, and surrounded in order to reduce vibration of meniscus upon ejection of the ink and not to interfere ejection of the ink droplet, and a narrow passage portion (in the publication, it is referred to as “local restricting portion”) is provided between a portion in the vicinity of an opening portion of a common ink supply passage and ends of respective ink supply passages.
On the other hand, as shown in Japanese Patent Application Laid-open No. 16365/1993, for example, there has been proposed one, in which bubble in expanded condition as heated by a heating surface of the heater portion is communicated with atmosphere in the vicinity of the ink ejection opening, and the ink covering the bubble and the ink in the vicinity of the ink ejection opening are continuous without being blocked by the bubble, so as to be employed in the side shooter type bubble jet head to efficiently eject relatively small ink droplet without spraying.
In such bubble jet head, for speeding up the printing operation, it becomes important to shorten a period for refilling of ink, as important factor for setting a driving frequency.
However, as in the foregoing example, when the heater portion is arranged within the receptacle portion and surrounded therein, and the descending cross sectional area passage portion (narrow passage portion) is provided between the opening portion of the common ink supply passage and the ends of respective ink supply passages, it is possible to increase flow resistance due to presence of the narrow passage portion. Thus, limitation should be caused in shortening of refilling period of the ink. On the other hand, upon high speed printing, residual bubble in the ink which should cause adverse effect of ejection speed of the ink droplet and ejecting direction of the ink droplet, can be retained within the ink supply passage due to presence of the narrow passage portion.
On the other hand, as noted above, when the bubble in the expanded condition as heated by the heating surface of the heater portion is communicated to the atmosphere in the vicinity of the ink ejection opening, and the ink covering the bubble and the ink in the vicinity of the ink ejection opening are continuous without being blocked by the bubble, since meniscus which becomes relatively large (after ejection of ink droplet (after cutting the ink droplet)) is caused, it becomes particularly necessary to reduce flow resistance. Therefore, influence of the narrow passage portion for the refilling period of the ink is significant.
SUMMARY OF THE INVENTION
In consideration of the above, it is an object of the present invention to provide a bubble jet head arranged in opposition to a printing surface of a printing medium for ejecting an ink toward the printing surface by a pressure of a bubble within the ink, and an bubble jet apparatus employing such bubble jet head, wherein a refilling period of the ink can be sufficiently shortened to permit speeding up of printing operation, and retention of residual bubble in the ink with in an ink supply passage can be avoided to enable stable ink ejecting operation.
In order to achieve the above object, there is provided a bubble jet head comprising:
a common ink supply passage having ink supply opening in one end portion and introducing an ink supplied from an ink storage portion through the ink supply opening;
branched ink supply passages, each having an opening end portion communicated with the ink supply opening of the common ink supply passage and supplying the ink to an ink heating portion via the opening end portion; and
an ink ejection opening forming surface arranged in opposition to the ink heating portion with a predetermined distance and having ink ejection openings for ejecting ink droplet formed by heating the ink supplied through the branched ink supply passages in the ink heating portion,
the branched ink supply passage has a region which a width of section of the branched ink supply passage in a direction perpendicular to a direction from the opening portion to the ink ejection opening in the branched ink passage is gradually narrowed from the opening end portion to the ink heating portion.
There is provided an bubble jet apparatus comprising:
a printing portion arranged in opposition to a printing surface of a printing medium, has having a head carrying portion selectively loaded the above bubble jet head;
a driving portion moving the printing portion along the printing surface of the printing medium;
a printing operation control portion for making the bubble jet head to perform printing operation.
As can be appreciated from the above, with the bubble jet head according to the present invention and the bubble jet apparatus employing the bubble jet head, since the width of section of the branched ink supply passage in a direction perpendicular to a direction from the opening end portion to the ink ejection opening, in the branched ink supply passage is gradually reduced from the opening end portion toward the ink heating portion, capillary effect in the vicinity of the ink heating portion is promoted to sufficiently shorten the refilling period of the ink to permit high speed printing operation. Also, retention of the residual bubble in the ink within the ink supply passage can be successfully avoided to stabilize ink ejecting operation.
On the other hand, in the case where the ink heating portion is surrounded by the wall portion of the receptacle portion formed continuously with the wall portion forming the circumferential edge portion of the branched supply passage, vibration of the ink ejection opening forming surface by the bubble generated in the ink can be restricted.
Furthermore, when the bubble formed in the ink is in the expanded state as heated by the ink heating portion, the bubble is in communication with the atmosphere in the vicinity of the ink ejection opening. Also, since the ink covering the bubble and the ink in the vicinity of the ink ejection opening are continuous, when the ink is ejected, ejection amount and the ejection speed can be stabilized without causing splash of the ink in the vicinity of the ink ejection opening.
The above and other objects, effects, features and advantages of the present invention will become more appa
Kaneko Mineo
Shioya Makoto
Tachihara Masayoshi
Tamura Yasuyuki
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stephens Juanita
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