Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2002-05-08
2004-02-17
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S087000
Reexamination Certificate
active
06692120
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to a pressure regulation apparatus for an ink reservoir, and more particularly, to a pressure regulation apparatus for an ink reservoir, which applies an elastic bag and a porous filter for complementarily regulating the back pressure within the ink reservoir to reach a steady balance of a pressure difference within and outside the ink reservoir.
BACKGROUND OF THE INVENTION
Nowadays, the ink-jet printer has become a necessary accessory printing equipment of a computer in modern information time. Typically, there are two mechanisms for ejecting drops of the ink from the ink reservoir. One is the piezoelectric pressure wave type, and the other is the thermal bubble type. No matter which type is used, the pressure must be controlled from the interior of the ink reservoir so that the ink reservoir of an ink-jet printer is under the best usage without ink leakage or ink blockage. That is, the back pressure (which means the partial vacuum within the ink reservoir or the pressure within the ink reservoir is slightly smaller than the atmospheric pressure) within the interior of the ink reservoir has to be maintained at a proper and steady condition. Generally, the ink reservoir of the ink-jet printer can be divided into two types. One is the ink reservoir for holding the ink only, and the other is the ink reservoir with a printing chip. The former must be co-operated with a print head mounted in the ink-jet printer, which has a printing chip. The latter combines the ink reservoir and the printing chip together, which is called inkjet head (ink-jet pen). Nevertheless, it is to be understood that the description below is limited to neither of the two above types. On the contrary, it is intended to cover a pressure regulation apparatus for an ink reservoir, which can be used in every kind of ink reservoir when the pressure needs to be regulated.
U.S. Pat. No. 5,409,134 disclosed a pressure-sensitive accumulator for an ink-jet pen, as shown in FIG.
1
. The accumulator includes an expandable bag
11
which is mounted attachably to a spring
12
. The upwardly projecting boss
131
is mounted on the cap
13
of the ink reservoir
1
so that the interior of the bag
11
is in communication with the ambient air outside the ink reservoir
1
through the central duct
132
which passes through the projecting boss
131
. When the ink reservoir
1
is used for printing, the space of air increases (and hence, the back pressure increases) as the ink is consumed. The bag
11
expands as a result of the back pressure increase. Expansion of the bag
11
deflects the spring
12
. The spring
12
bent originally will tend to be straight and accumulate the recovery strength. Meanwhile, the ambient air outside the ink reservoir
1
enters the interior of the bag
11
through the projecting boss
131
so that the back pressure within the ink reservoir
1
and the outside ambient pressure reach a proper balance. Similarly, if some factors result in the ambient pressure outside the ink reservoir
1
smaller than the pressure within the ink reservoir
1
, the recovery strength of the spring
12
will make itself back to its original bent shape. The recovery strength of the spring
12
tends to contract the bag
11
. Therefore, the bag
12
volume decreases and the internal air within the ink reservoir
1
is squeezed out of the ink reservoir
1
so that the pressure within and outside the ink reservoir
1
can reach a balance.
In the operation of air regulation to maintain the pressure balance, a relative adjustment of the back pressure change within the ink reservoir
1
is accomplished by the relationship between the elasticity of the spring
12
and the expansion of the bag
11
mounted attachably thereto. Since the interior of the bag
11
has a big air capacity, the air capacity change generated by a bigger pressure difference is allowed. However, the spring
12
itself has a basic pressure requisite upon deformation, so it lacks the sensitivity of the pressure difference if the pressure difference is not big enough. On the other hand, in the respect of manufacturing technology, it is difficult to control the coefficient of elasticity of the spring
12
and the capacity change of the bag
11
accurately. It is easy to cause the spring
12
to be bent or relaxed while the pressure difference is just generated. However, the flexure and the deformation of the spring
12
, which are caused by the pressure difference, will be slow down if the spring
12
has been bent to a certain extent. In addition, the spring
12
and the bag
11
might not have a good attachment, and we must consider the possible malfunction upon the assembly of the projecting boss
131
. Therefore, the apparatus established according to this pressure regulation method might have a poor response to the pressure change after being used for a period of time. It might also cause a lower product pass rate when manufacturing.
Additionally, U.S. Pat. No. 5,526,030 disclosed another apparatus of the pressure regulation, as shown in FIG.
2
. An opening
21
is mounted at the bottom of the ink reservoir
2
. A sphere
22
is mounted concentrically within the opening
21
. The sphere
22
is maintained within the opening
21
by a number of raised crush ribs
23
formed around the interior of the opening
21
. The outside diameter of the sphere
22
is smaller than the inside diameter of the opening
21
to define an annular orifice
24
(as shown in FIG.
3
). Under the opening
21
, an inlet labyrinth
25
is provided, which is a path having a semicircular cross section between the hole
27
and the opening
21
. The whole length of the inlet labyrinth
25
is sealed from both the ambient air and the reservoir by a cover
26
. The proximal end of the inlet labyrinth
25
opens to the opening
21
and the distal end opens to the ambient air through a hole
27
mounted on the cover
26
. When the pressure within the ink reservoir
2
is lower than that of the outside, the ambient air passes through the inlet labyrinth
25
and the annular orifice
24
to enter the ink reservoir
2
to balance the pressure within and outside the ink reservoir
2
. When the pressure within the ink reservoir
2
is higher than that of the outside, the ink enters the inlet labyrinth
25
at the bottom of the ink reservoir
2
through the annular orifice
24
and is stored within the inlet labyrinth
25
temporarily. Nevertheless, when the pressure within the ink reservoir
2
returns to the normal, the ink stored within the inlet labyrinth
25
temporarily will reenter the ink reservoir
2
by the pressure difference and the capillarity.
This pressure regulation method is simpler than the former method which uses a bag and a spring. However, since the inlet labyrinth
25
at the bottom of the ink reservoir
2
can only keep a very small amount of ink, the inlet labyrinth
25
might not be able to completely keep the excessive ink if the pressure difference within and outside the ink reservoir
2
is too large. Therefore, the phenomenon of ink leakage, which means that the ink flows out from the ink reservoir
2
through the annular orifice
24
, will happen. On the other hand, the annular orifice
24
formed by the relative cooperation between the raised crush ribs
23
and the opening
21
must have a good accuracy, or the capillarity can not proceed smoothly. Accordingly, the product pass rate is reduced.
In view of how important the pressure regulation is and its serious affect to the smoothly ejecting drops of ink from the ink reservoir, a pressure regulation apparatus for an ink reservoir is provided. The ink reservoir described in the present invention covers both the type of ink reservoir for only holding ink and the type of ink reservoir with a printing chip.
SUMMARY OF THE INVENTION
The main purpose of the present invention is to provide a pressure regulation apparatus for an ink reservoir, which applies the elastic bag and the porous filter for complementarily regulating the back pressure within the in
Chang Cheng-Min
Yu Rong-Ho
Madson & Metcalf
Microjet Technology Co., Ltd.
Vo Anh T. N.
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