Pressure control device

Details Pressure control device Pressure control device

2002-06-21

2003-09-09

Vo, Anh T.N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Fluid or fluid source handling means

C347S086000

Reexamination Certificate

active

06616272

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the priority benefit of Taiwan application serial no.91202654, filed Mar. 7, 2002.
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a pressure control device. More particularly, the present invention relates to a pressure control device inside the ink reservoir of an inkjet module.
2. Description of Related Art
In general, the print head of an inkjet printer has some mechanism for controlling the flow of ink from an ink reservoir to print media. To prevent ink from leaking out of the print head, a partial vacuum is usually created inside the ink reservoir so that the air pressure inside the reservoir is slightly smaller than external atmospheric pressure. Hence, a negative pressure permanently exists inside the ink reservoir and leakage of ink is prevented. Note that if the negative pressure inside the reservoir is too high, the inkjet print head may not provide sufficient force to spread out the ink. Thus, the negative pressure inside the ink reservoir must be maintained within a definite range for normal operation of the print head.
However, due to constant fluctuation of atmospheric pressure, negative pressure inside the ink reservoir changes correspondingly. To maintain the negative pressure within a defined range, a number of pressure regulators have been developed. For example, one such pressure regulator for controlling the negative pressure inside an ink reservoir is disclosed in Taiwan Patent No. 438684 (U.S. Pat. No. 6,213,598).
FIGS. 1A and 1B
are schematic cross-sectional views showing a portion of the internal layout of a pressure regulator as described in U.S. Pat. No. 6,213,598. As shown in
FIGS. 1A and 1B
, an air bag
136
is installed inside an ink reservoir
110
. The air bag
136
is connected to the external atmosphere through a pipeline
138
so that internal volume of the ink reservoir
110
may increase or decrease by expanding or contracting the air bag
136
. Ultimately, pressure inside the ink reservoir
110
also changes. Using this mechanism, negative pressure inside the ink reservoir is maintained within a permitted range. However, the air bag
136
must encounter a limit to expansion. When most of the ink inside the reservoir is used and the air bag has expanded so much that the negative pressure inside the ink reservoir is no longer regulated by the air bag
136
, negative pressure inside the ink reservoir gradually rises. To bring down the negative pressure again, a pressure control device
200
is often fitted inside the ink reservoir
110
so that external gases may rush into the ink reservoir
110
to increase the gas pressure inside the ink reservoir
110
. Hence, negative pressure inside the ink reservoir
110
is lowered and internal pressure is maintained within a permitted range.
As shown in
FIG. 1A
, the pressure control device
200
further includes a vent
210
, a plugging block
220
and a spring-loaded structure
230
. The vent
210
includes a hole
212
and a groove
214
. The hole
212
is a connective channel linking up both the interior and the exterior of the ink reservoir
110
. Furthermore, the groove
214
is at the upper end of the hole
212
while the plugging block
220
is placed inside the groove
214
. A first section
230
a
of the spring-loaded structure
230
presses against the upper portion of the plugging block
220
so that the plugging block
220
seals the hole. Hence, the interior of the ink reservoir
110
is isolated from the exterior. The plugging block
220
can be a spherical body such as a steel ball. When the air bag
36
continues to expand and moves a plate
134
in the B direction, the plate
134
pushes against a second section
230
b
of the spring-loaded structure
230
as shown in FIG.
1
B. In the meantime, such movement in the second section
230
b
of the spring-loaded structure
230
raises the first section
230
a
of the spring-loaded structure
230
. Ultimately, the first section
230
a
of the spring-loaded structure
230
no longer comes in contact with the upper edge of the plugging block
220
.
Since air pressure outside the ink reservoir
110
is greater than internal air pressure, an external pressure will exert on the plugging block
220
through hole
212
trying to raise the plugging block
220
. This will increase the air pressure inside the ink reservoir
110
and lower the negative pressure that exists between the interior and exterior of the ink reservoir
110
. The spring
132
of a pressure regulator
130
compresses the air sac
136
by exerting a force against the pressure plate
134
in direction A as shown in FIG.
1
A. However, when the plate
134
no longer touches the second section
230
b
of the spring-loaded structure
230
, the first section
230
a
of the spring-loaded structure
230
will return to an elastic state pressing against the upper edge of the plugging block
220
. Consequently, the plugging block
220
returns to the original position sealing the nozzle hole at the upper end of hole
212
and restores the partition between the interior and exterior of the ink reservoir
110
.
As shown in
FIGS. 1A and 1B
, the spring-loaded structure
230
of a conventional pressure control device
200
is a piece of metallic strip. When the pressure plate
134
of the pressure regulator
130
exerts too much pressure on the second section
230
b
or the ink module
100
vibrates too much, the first section
230
a
is raised to a high level moving the first section
230
a
away from the plugging block
220
. Thus, the first section
230
a
is unable to hold the plugging block
220
in position any longer. Sometimes, the plugging block
220
may jump out of the groove
214
forever so that the nozzle
212
is no longer sealed. In other words, the pressure control device
200
no longer works in tandem with the pressure regulator
130
to provide necessary negative pressure adjustment inside the ink reservoir
110
.
SUMMARY OF INVENTION
Accordingly, one object of the present invention is to provide a pressure control device capable of maintaining the negative pressure inside an ink reservoir within a definite range and limiting the moving range of an internal spring-loaded structure, in particular, the moving range of a first section of the spring-loaded structure so that the dislodging of a plugging block from functional position is prevented and pressure control is always maintained.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a pressure control device installed inside an ink reservoir. The pressure control device sets up a negative pressure between the interior and the exterior of the ink reservoir. The ink reservoir further includes a pressure regulator. The pressure control device at least includes a vent, a plugging block and a spring-loaded structure. The vent is positioned inside the interior wall of the ink reservoir. The vent has a groove near the upper end of the hole. The plugging block is placed within the groove for partitioning the ink reservoir into an interior and an exterior. The spring-loaded structure is also set up within the interior wall of the ink reservoir. The spring-loaded structure has a first section and a second section. The first section presses against the outer edge of the plugging block and exerts an elastic force on the plugging block. The second section is coupled to the pressure regulator so that any change in negative pressure is transformed into a corresponding movement of the second section of the spring-loaded structure. In this way, the first section of the spring-loaded structure is detached from the outer edge of the plugging block.
To prevent the first section of the spring-loaded structure from moving too far away from the plugging block so that the plugging block may jump out of the groove, the spring-loaded structure includes a third section connected to the second section of the spring-loaded structure. One end o

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