Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-02-08
2002-10-15
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S094000
Reexamination Certificate
active
06464345
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid discharging head, which discharges the liquid by acting a thermal energy on the liquid to generate bubbles, a method of producing the same, and liquid discharging apparatus which uses the same head.
The present invention is applicable to devices, e.g., a printer and copier recording images on a printing medium (e.g., paper, yarn, fiber, cloth, leather, metal, plastic, glass, lumber and ceramic), a facsimile having a communication system, a word processor having a printer, and an assembly in which an industrial recording device is combined with a varying processing device.
The term “recording” used herein not only refers to forming a meaning image (e.g., letter, pattern or the like) on a recording medium but also a meaningless image (e.g., pattern).
2. Related Background Art
The ink jet recording method is known for recording devices, e.g., printer. This method, also known as bubble jet recording method, gives energy (e.g., heat) to a liquid ink flowing in a flow passage to generate bubbles, rapid volumetric change as a result of which is used to discharge the ink from the discharge port onto a recording medium to form an image thereon. The recording device which is based on the bubble jet recording method generally has an ink discharge port from which the ink is discharged, an ink passage leading to the discharge port, and an electrothermal converter as the energy-generating means needed for discharging the ink in the passage, as disclosed by, e.g., U.S. Pat. No. 4,723,129.
This type of recording method has various advantages, e.g., giving a high-quality image quickly at low noise, and also easily giving a high-resolution recording image and color image by a compact device, because of its head being provided with ink discharge ports at a high density. Therefore, the bubble jet recording method recently has been massively going into various office devices, e.g., printers, copiers and facsimiles, and even into industrial systems, e.g., textile printers.
As the bubble jet techniques are finding wider use in various areas, they are increasingly required to have higher functions, for which various proposals have been made, e.g., driving conditions for improved liquid discharging methods which allow higher ink discharging speed and better ink discharging based on stable bubble generation for higher-quality images, and improved ink flow passage shapes for a liquid discharging head which secures faster refill of the discharged liquid into the passage.
For the head in which the bubbles are generated and grown in the nozzle to discharge the liquid, it is known that growth of the bubbles away from the discharge port and the resultant liquid flow deteriorate discharging energy efficiency and refill characteristics. The structures to improve discharging energy efficiency and refill characteristics are disclosed by European Patent Application Laid-Open Specification EP0436047A1.
The above invention has the first valve between the vicinity of the discharge port and a bubble generating section to completely cut off them from each other, and second valve between the bubble generating section and ink supply section also to completely cut off them from each other, wherein these valves open or close alternately (FIG. 4 to FIG. 9 in EP436047A1 specification). For example, referring to FIG. 14 in this specification, which is FIG. 7 in the EP436047A1 specification, the heat generating member
110
is provided almost at the center of the ink passage
112
running between the ink tank
116
and nozzle
115
, the ink tank
116
being on the base plate
125
which forms the inner wall for the ink passage
112
. The heat generating member
110
is encased in the totally closed compartment
120
in the ink passage
112
. The ink passage
112
is composed of the base plate
125
directly coated with the thin films
123
and
126
placed one on another, and tongue-like pieces
113
and
130
as the closing bodies. The tongue-like piece in the open condition is shown in
FIG. 31
by the dotted lines. The thin film
123
, running in the plane in parallel to the base plate
125
and terminating at the stopper
124
, covers the ink passage
112
. As the bubbles are generated in the ink, the free end of the tongue-like piece
130
in the nozzle area, in closely contact with the stopper
126
while it is stationary, moves upward, and the ink liquid in the compartment
120
is ejected from the nozzle
115
via the ink passage
112
. In this case, the ink liquid in the compartment
120
is prevented from moving towards the ink layer
116
, because the tongue-like piece
113
in the ink layer
116
area comes into close contact with the stopper
124
while it is stationary. The tongue-like piece
130
moves downward, as the bubbles in the ink disappear, and comes into close contact with the stopper
126
again. Then, the tongue-like piece
113
falls in the ink compartment
120
, allowing the ink liquid to flow into the compartment
120
.
SUMMARY OF THE INVENTION
The invention disclosed in EP0436047A1 has several disadvantages. For example, the ink following the bubbles significantly trails while it is discharged, because two out of the three compartments of near the discharge port, bubble generating section and ink supply section are separated from each other, producing a fairly larger quantity of the satellite dots than the conventional discharging method involving growth, shrinkage and disappear of the bubbles. This trouble conceivably results from loss of the effect of meniscus retreat accompanying disappear of the bubbles. Another disadvantage is dissipation of large quantity of energy for discharging the ink, when the valve on the bubble discharge side is closed. Still other disadvantages are large fluctuation of size of the discharged liquid droplets and extremely low discharge response frequency, which make the invention impractical. These problems come from its structure: the compartment is refilled to make up the ink to be supplied to the nozzle as the bubbles in the liquid disappear in the bubble generating section, and the vicinity of the discharge port cannot be supplied with the liquid until the new bubbles are generated.
The present invention provides an innovative method and head structures which simultaneously satisfy the characteristics running counter to each other; improved efficiency of controlling growth of the bubble component away from the discharge port, and improved refill efficiency and characteristics, based on the new concept. They also satisfy requirements for improved discharging efficiency.
The inventors of the present invention have found, after having extensively studied to satisfy the above requirements, that growth of the bubbles away from the discharge port (i.e., towards the rear side) is controlled by the special check valve function in the straight nozzle structure in the liquid-discharging head, where the liquid is discharged as the bubbles grow, and that the discharging energy towards the rear side can be effectively utilized for the discharge port side. They also have found that controlling growth of the bubble component towards the rear side by the special check valve function can increase discharge response frequency to an extremely high level.
It is an object of the present invention to simultaneously improve discharge power and discharge frequency by the nozzle structure and discharging method incorporating a novel valve function, and thereby to establish the novel discharging formula (structure) for a head which can produce higher-quality images at a higher speed than the conventional one can achieve.
In order to achieve the above objects, the liquid discharging head of the present invention is provided with a discharge port for discharging the liquid, liquid passage provided with bubble-generating means for generating the bubbles in the liquid supplied via a liquid supply port, and in communication with the discharge port at its one end, and movable member arranged apart f
Inoue Ryoji
Kubota Masahiko
Kudo Kiyomitsu
Takenouchi Masanori
Barlow John
Stephens Juanita
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