Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-07-27
2003-03-18
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06533401
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid discharging apparatus for discharging liquid by generating a bubble by the application of heat energy on the liquid, and more particularly to a liquid discharging apparatus having a movable member which displaces by taking advantage of generation of the bubble.
In this respect, “recording” in the present invention is not only to impart a significant image such as characters and patterns onto a recording medium, but also to impart a meaningless image including any other than patterns or the like.
2. Related Background Art
Conventionally, there has been known an ink jet recording method, a so-called bubble jet recording method, in which, in a recording apparatus such as printers, the bubble is generated by imparting energy such as heat to liquid ink in a flow path, and the ink is discharged through discharging ports by means of an operating force based on a sudden volume change caused by the occurrence of the bubble to cause the ink to adhere onto a recording medium for forming an image. A recording apparatus using this bubble jet recording method is generally provided, as disclosed in specification of U.S. Pat. No. 4,723,129 or the like, with discharging ports through which the ink is discharged, flow paths communicated to these discharging ports, and electrothermal transducers as energy generating means for discharging the ink provided within the flow paths.
Such a recording method has many excellent advantages that it is possible to easily obtain a recorded image with high resolution and further, a color image with a small-sized apparatus because a high-quality image can be recorded at high speed and in low noise and a head in which this recording method is performed can be at high density provided with discharging ports for discharging the ink. For this reason, this bubble jet recording method has been utilized for many office equipment such as printers, copying machines and facsimile apparatuses in recent years, and further for industrial systems such as textile printing apparatuses.
As the bubble jet technique has been utilized for products in many fields as described above, the following various requests have been further increasing in recent years.
In order to obtain a high-quality image, there are proposed driving conditions for allowing a liquid discharging method in which excellent ink based on stable occurrence of the bubble can be performed at high speed, and a method in which the shape of flow paths has been improved in order to obtain a liquid discharging head having a faster refill speed of the discharged liquid within the flow paths in view of high-speed recording.
In addition to such a head, there has been disclosed, in Japanese Patent Application Laid-Open No. 6-31918, an invention having configuration to prevent back waves (pressure toward a direction opposite to the direction toward the discharging ports), which becomes loss energy in the discharging, focusing attention on the back waves for occurring with the generation of the bubble. The invention specified in this publication is that a triangular portion of a triangular plate-shaped member is caused to oppose to a heater for generating the bubble. According to this invention, the plate-shaped member restrains the back waves temporarily and slightly. This invention, however, does not touch on correlation between the growth of the bubble and the triangular portion, but the invention includes the following problems because it has no idea thereof.
That is, according to the invention specified in the above-described publication, the heater is located at the bottom of a concave portion and cannot be linearly communicated to the discharging ports, and therefore, the shape of liquid droplets cannot be stabilized. Further, since the growth of the bubble is allowed around the vertex of the triangle, the bubble grows from one side of the triangular plate-shaped member to the entire opposite side, with the result that normal growth of the bubble in the liquid is completed as if there existed no plate-shaped members. Therefore, the existence of the plate-shaped member would have nothing to do with growing the bubble. On the contrary, since the entire plate-shaped member is enclosed with the bubble, refilling to the heater located at the concave portion causes a turbulent flow in a shrinkage state of the bubble to thereby accumulate fine bubbles within the concave portion, thus violating the principle itself in which discharging is performed based on growing the bubble.
On the other hand, EP Patent Application Laid-Open No. 436047A1 has proposed an invention in which a first valve for intercepting a relation between a discharge port-neighboring area and the bubble generating unit and a second valve for completely intercepting a relation between the bubble generating unit and an ink supply unit are caused to be alternately opened and closed (FIGS. 4 to 9 of EP436047A1). In this invention, however, since these three chambers are partitioned into two chambers each, ink following the liquid droplet becomes large trailing during discharging, and there are a considerably multiplicity of satellite dots as compared with the normal discharging system in which growth of bubble, shrinkage (contraction) and bubble disappearance are performed (it is inferred that an effect of backward movement of meniscus by bubble disappearance could not be used). During refilling, although the liquid is supplied to the bubble generating unit with the bubble disappearance no liquid can be supplied to the discharge port-neighboring area until the next expanding is generated, and therefore, variations in discharged liquid droplets are not only large, but also the discharge response frequency is very small—being not at practical level.
There have been proposed, by the present applicant, a number of inventions using a movable member (a plate-shaped member having a free end closer to the discharge port side than a support, or the like) capable of effectively contributing to discharging of liquid droplets quite unlike the above described prior art. Of these inventions, a Japanese Patent Application Laid-Open No. 9-48127 discloses an invention in which the upper limit of displacement of the movable member is regulated in order to prevent behavior of the above described movable member from being slightly confused. Also, a Japanese Patent Application Laid-Open No. 9-323420 discloses an invention in which an upstream common liquid chamber is shifted on the free end side of the movable member, that is, on the downstream side by the utilization of the advantage of the movable member to enhance the refilling ability. These inventions do not focus attention on individual elements concerning formation of the liquid droplet by the entire bubble and correlation of those elements because, as a precondition for the invention, there has been supposed a form in which the growth of the bubble is released on the discharge port side at a stroke from a state in which it is temporarily wrapped by the movable member.
As the next stage, the present applicant has disclosed, in a Japanese Patent Application Laid-Open No. 10-24588, an invention in which a part of the bubble generating area is released from the movable member, as an invention (acoustic wave) in which attention is focused on the growth of the bubble due to propagation of pressure waves as an element relating to the discharging of liquid. Even in this invention, however, no attention has been focused on individual elements concerning formation of the liquid droplet itself by the entire bubble and correlation of those elements because attention is focused only on the growth of the bubble when the liquid is discharged.
Although it is known that the front portion (edge shooter type) of the bubble due to conventionally-known film boiling greatly affect the discharging, no one has focused attention on causing this portion to more efficiently contribute to formation of the discharged liquid droplet, but the present inventors
Ishinaga Hiroyuki
Matsumoto Nobuyuki
Sugama Sadayuki
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Mouttet Blaise
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