Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-05-06
2003-03-11
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S065000, C347S094000
Reexamination Certificate
active
06530648
ABSTRACT:
This application incorporates by reference of Taiwan application Serial No. 90110879, filed on May 7, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to an ink injector, and more particularly to an apparatus for using bubble as a virtual valve to eject ink and a fabricating method thereof.
2. Description of the Related Art
Over the years, electronic related industries have progressed as the technology advances. For various electronic products, such as computer systems, computer peripherals, appliances and office machines, their functions and appearances have improved greatly as well. For example, in the 1980s, impact-type dot matrix printers and monochrome laser printers were pre-dominant. Later in the 1990s, monochrome inkjet printers and color inkjet printers became popular for general-purpose use while color laser printers were available for professional use. For general use, users would probably choose color inkjet printers after considering the printing quality and price. Users with sufficient budgets would probably purchase a monochrome laser printer. Since the price and quality are critical to the users' decisions, printer manufacturers aggressively develop their products so that the products have lower cost and better quality, in order to increase the popularity and profit of their products. Therefore, developers are focusing on how to improve the performance of products under limited cost.
Most inkjet printers now use either a bubble inkjet printhead or a piezo-electrical inkjet printhead to eject ink droplets onto a recording medium, such as paper, for printing. The bubble inkjet printhead comprises a plurality of chambers adjacent one another. Each chamber comprises at least a heater, ink, and an orifice. Also, a manifold is adjacent to and in flow communication with the chamber. Ink from a reservoir is supplied to each chamber by passing through the associated manifold. The heater heats the ink of the chamber to create bubbles until the bubbles expand enough to expel the ink droplets through the orifice and onto the recording medium, such as a sheet of paper. When the activation of the heater is terminated, the bubbles collapse so that the ink in the reservoir refills into the chamber through the manifold. Adjusting the concentrations and locations of the droplets on the paper can form a variety of texts and graphics. The quality of the printing result is related to the resolution provided by the printer. Currently, entry-level color printers provide a good resolution of 720×720 dpi (dots per inch) or 1440×720 dpi. The finer size the droplet is, the higher resolution the printer has.
However, those bubble inkjet systems (also known as thermally driven bubble system) suffer from cross talk and satellite droplets. When the bubbles expand, the ink is pushed from all sides, so the ink in the chamber is not only ejected through the orifice, but is also pushed towards the manifold. Such effect will deteriorate the ink stability of the adjacent chambers. If the adjacent chamber with unstable ink performed ink ejection, some problems may arise. For example, the size of droplets may vary, or the droplets may hit the paper surface at slightly different locations. After the bubbles collapse, the refilling of the ink into the chamber may also interfere with the ink in the adjacent chambers. The phenomena described above are known as cross talk. Cross talk frequently occurs when the chambers are placed in arrays with close pitch, and the droplets eject from the adjacent orifices. Moreover, the unstable ink condition may affect the ink ejected through the orifice, causing satellite droplets. For example, the ink close to orifice could overflow, or the tail of ink droplet would not be cut off abruptly. The tiny ink droplets that trail the main droplets, known as satellite droplets, may hit the paper at locations slightly different than the main droplets and blur the printed image. The problems of cross talk and satellite droplets degrade the sharpness of printed image. Various technologies have been provided to solve these problems.
Generally, to increase the resolution of the print image, the orifices of the inkjet printhead for ejecting ink from the chamber are arranged in the form of arrays. In practical application, all ink chambers have identical, or very similar, structure; hence, only one ink chamber is illustrated in the following description and related drawings.
FIG. 1
is a cross-sectional view of a known ink chamber on the printhead (disclosed in U.S. Pat. No. 4,494,128), wherein the printhead is particularly applied in a gray scale inkjet printer. An ink reservoir and a vehicle reservoir (not shown in
FIG. 1
) are used for storing undiluted ink
10
and appropriate diluting vehicle
12
, respectively. Also, the ink reservoir and the vehicle reservoir are connected to a chamber
18
by ink capillary
14
and vehicle capillary
16
, respectively. The vehicle
12
can be a solvent employed to dissolve the dye in the undiluted ink
10
. Varying the ratio of the ink
10
and vehicle
12
produces a wide range of ink concentrations. A discharge orifice
22
is formed on the top surface
19
of the chamber
18
. Within the chamber
18
is a means of discharging the ink, such as a heater
20
, which heats the ink to create the bubble for expelling a droplet
23
through the discharge orifice
22
. The ink valve
24
and vehicle valve
26
are resistors set in the ink capillary
14
and vehicle capillary
16
for controlling the volume of ink
10
and vehicle
12
entering into the chamber
18
. When an electrical current is applied to the resistors, the valve bubble is generated in the ink capillary
14
and/or in the vehicle capillary
16
to stop the flow of ink
10
and/or vehicle
12
to enter the chamber
18
. The ink valve
24
and vehicle valve
26
can be turned on or off independently for any desired length of time. By appropriately determining the ratios of on/off times of the ink valve
24
and the vehicle valve
26
, a full gray scale range of printing is produced. This conventional method creates a narrow region in which a heater is placed. The bubble generated from the heater is able to block the flow of ink
10
or vehicle
12
, in order to reduce the effects of cross talk. However, after the droplet
23
has been ejected, the narrow region makes it difficult to refill the chamber
18
with the ink
10
and/or vehicle
12
quickly.
FIG. 2
is an enlarged view of another known ink chamber on the printhead (disclosed in U.S. Pat. No. 5,278,584). There is a discharge means such as the heater
32
on the substrate
29
of the chamber
30
. By applying the electrical current to turn on the heater
32
, the bubble is generated to expel the ink out of the orifice
34
. Subsequently, the chamber
30
is refilled by capillary action. The ink stored in the reservoir flows through the manifold, the channel
36
, and the chamber
30
, as shown by the arrow A.
According to this conventional method, the channel
36
between the manifold and the chamber
30
has a buffering effect on the ink in the chamber
30
. For example, the variation in ink pressure, due to ink ejection or bubble formation, can be blocked by the channel
36
. Therefore, the interfering effects of cross talk on the adjacent chambers, caused by the ejection of ink, can be reduced. However, the rate of refilling ink to the chamber
30
is subject to the cross-sectional area of channel
36
, and the ink jet frequency of the printer is decreased.
In other words, in
FIG. 2
when the bubble is generated and collapsed, the cross talk effects caused by the disturbed flow of ink can be reduced by building a channel between the manifold and the chamber. However, the existence of the channel also prolongs the time for refilling the chamber with ink.
Accordingly, the main goals for researchers and manufacturers are to prevent the cross talk phenomena, increase the flow rate of ink to refill the chamber, and enhance the resolution of inkjet printing. In
Chen Wei-Lin
Chou Chung-Cheng
Hsu Tsung-Ping
Hu Hung-Sheng
Lee In-Yao
Benq Corporation
Rabin & Berdo PC
Stephens Juanita
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