Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-01-12
2001-11-06
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S065000
Reexamination Certificate
active
06312109
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to an ink-jet head, and especially to an ink-jet head with bubble-driven flexible membrane.
B. Description of the Prior Art
The structure of a conventional bubble-driven ink-jet head is illustrated in FIG.
1
. Referring to
FIG. 1
, the ink-jet head comprises: a substrate
1
, a heating layer
2
with a resistor
3
formed on the substrate
1
, a dielectric layer
4
formed on the substrate
1
, a nozzle plate
5
formed on the dielectric layer
4
having a nozzle
6
formed therein, and an ink chamber
7
formed within said dielectric layer
4
and between the heating layer
2
and the nozzle plate
5
for containing ink, and an ink channel
8
communicating with an external ink cartridge (not shown).
When applied with a voltage pulse, the resistor
3
provides a sudden outburst of thermal energy to cause the adjacent ink to vaporize locally, and creating a bubble in the ink chamber
7
. The sudden expansion of the bubble creates a pressure wave in the ink and causes an ink droplet to be expelled from the nozzle
6
. Then, when the voltage pulse has vanished, the bubble collapses soon afterwards. Thus, the ink ejections can be generated repeatedly by controlling the application of voltage pulses to the resistor
3
.
A problem of the conventional bubble-driven ink-jet head is that it vaporizes the ink directly. In this case, it requires new kinds of ink which must be thermal-stable, of low electrical conductibility, and of low chemical activity. Moreover, when the bubbles are created and collapse near the resistor
3
, the impact caused by the bubbles can damage the resistor
3
, and the chemical properties of the ink can also cause damage to the resistor
3
, thus inevitably reduce the lifetime of the resistor
3
. In addition, since the creation and collapse of the bubbles are determined by temperature, rapid heat dissipation is required. Accordingly, when the resistor
3
vaporizes the ink, it has to be cooled down rapidly. Moreover, the printing quality may be impaired due to the ink droplets remained on the outer surface of the nozzle plate after ejection.
To overcome the above-mentioned problems, U.S. Pat. No. 4,480,259 disclosed an ink-jet printer with bubble driven membrane. Referring to
FIG. 2
, the ink-jet head of the ink-jet printer comprises: a substrate
11
; a heating layer
12
with a resistor
13
formed on the substrate
11
; a flexible membrane
14
formed on the heating layer
12
and forming a working fluid chamber
15
cooperating with the heating layer
12
to contain working fluid; a dielectric layer
16
formed on the flexible membrane
14
and forming an ink chamber
17
therein; and a nozzle plate
18
formed on the dielectric layer
16
with a nozzle
19
formed therein.
When the resistor
13
is applied with a voltage pulse, the resistor
13
provides a sudden outburst of thermal energy to cause the working fluid to vaporize locally, and creating a bubble in the working fluid chamber
15
. The sudden expansion of the bubble increases the pressure within the working fluid chamber
15
. The expansion of the bubble causes the flexible membrane to be deformed, resulting in a local deformation of the membrane and the propagation of a pressure wave to the ink in the ink chamber
17
. The pressure wave then ejects a droplet of ink from the nozzle
19
. By controlling the energy input to the resistor
13
, the bubble collapse quickly back onto or near resistor
13
so that repeated operations are feasible.
The advantage of the ink-jet head with bubble driven flexible membrane is that it is not necessary to directly heat the ink. Instead, a selected working fluid is heated. So, it can be used with any kinds of conventional ink and working fluid which do not cause damage to the resistor. However, the prior art still left a few problems unresolved yet including the problems of rapid heat dissipation, and ink droplets remaining on the outer surface of the nozzle plate. In addition, there is still a problem about erroneous operation of ink ejection caused by pressure wave propagation. Each working fluid chamber is communicating with one another via a working fluid channel and thus forming a closed working fluid channel system. In this case, when the working fluid creates a bubble within the working fluid chamber, since the working fluid itself is incompressible, a pressure wave will be transmitted to a neighboring working liquid chamber of an adjacent ink-jet head unit and causes ink droplets to be ejected from wrong ink-jet head units. Moreover, the membrane of the prior art is made of material that cannot prevent of vaporized working fluid and is not made of material durable enough to sustain high frequency operations of ink ejection.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an ink-jet head with a bubble-driven flexible membrane that is made of a material durable enough to sustain high frequency operations of ink ejection, and is capable of preventing infiltration of vaporized working fluid.
Another object of the invention is to provide an ink-jet head with a bubble-driven flexible membrane that does not cause ink droplets to be remained on the outer surface of the nozzle plate, thereby improving the printing quality.
Yet another object of the invention is to provide an ink-jet head with a bubble-driven flexible membrane that provides rapid heat dissipation, thereby increasing the working frequency and improving the printing quality.
Still yet another object of the invention is to provide an ink-jet head with a bubble-driven flexible membrane that prevents erroneous operations of ink ejection caused by a pressure wave transmitted from a working fluid chamber to other neighboring working fluid chambers, thereby improving the printing quality.
To achieve the above objects, the ink-jet head with a bubble-driven flexible membrane in accordance with the invention comprises: a dielectric substrate; a heating layer formed on said dielectric substrate, the heating layer comprising a resistor for converting electricity into thermal energy; a heat dissipating layer formed on the heating layer; a working fluid chamber formed in the heat dissipating layer and corresponds to the area above of the resistor for containing working fluid; a nozzle plate formed on the heat dissipating layer, the nozzle plate comprises a nozzle, and the surface that faces the exterior surrounding is the outer surface of the nozzle plate; an ink chamber formed in the nozzle plate for containing ink, and the peripheral surfaces of the ink chamber are the inner surfaces of the nozzle plate; and a flexible membrane formed between the heat dissipating layer and the nozzle plate to separate the working fluid chamber from the ink chamber.
When a voltage pulse is applied to the resistor, a sudden outburst of thermal energy causes the working fluid to vaporize locally and to create a bubble in the working fluid chamber. The expansion of the bubble causes the pressure within the working fluid chamber to increase, and thus pushes the flexible membrane outwards. The sudden expansion creates a pressure wave in the working fluid that is propagaged to the ink within the ink chamber, and causes an ink droplet to be expelled from the nozzle. After that, when the voltage pulse has vanished, the bubble collapses soon afterwards. Thus, the ink ejections can be generated repeatedly by controlling the application of voltage pulses to the resistor.
In accordance with the invention, the flexible membrane is of a stacked structure so that its durability is strong enough to sustain high frequency operations of ink ejection, and capable of preventing infiltration of vaporized working fluid.
In accordance with the invention, the heat dissipation layer surrounding the working fluid chamber has a good heat dissipation efficiency, thereby improving the operation frequency and printing quality.
In accordance with the invention, the inner surface of the nozzle plate is overlaid with a well-wettable layer so that th
Barlow John
Birch & Stewart Kolasch & Birch, LLP
Pamelan Company Limited
Stephens Juanita
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