Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2000-08-16
2003-03-04
Nghiem, Michael (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06527381
ABSTRACT:
This application is based on Japanese Patent Application No. 11-236782 (1999) filed Aug. 24, 1999, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid container capable of maintaining a supply ability of ink, a liquid ejection mechanism employing the liquid container and a liquid ejection apparatus.
It should be noted that the present invention is applicable not only for a typical printing apparatus but also for a copy machine, a facsimile having a communication system, a wordprocessor having a printing portion, and so on, and further for an industrial printing apparatus composed with various processing systems.
2. Description of the Related Art
In general, a liquid container serving as an ink tank in a printing apparatus to be used in a field of an ink jet apparatus, is provided with a construction for adjusting a holding force of ink stored in the ink tank in order to satisfactorily perform ink supply for a printing head for ejecting the ink. This holding force is referred to as negative pressure since a pressure of an ink ejecting portion of the printing head becomes negative relative to an atmospheric pressure. (Such a member for generating the negative pressure will be hereinafter referred to as a negative pressure generating member.)
One of the easiest method for generating such negative pressure is to provide an ink absorbing body, such as a porous body including a urethane foam, felt and the like, within the ink tank to utilize capillary phenomenon (ink absorbing force) of the ink absorbing body.
For example, Japanese Patent Application Laid-open No. 6-15839 (1994) discloses a construction with choking up a plurality of ink absorbing bodies having mutually different density in the order of a high density absorbing body and a low density absorbing body toward a supply passage, over the entire tank, within the ink tank. The high density absorbing body has a longer total length of fiber per unit volume to have higher ink absorption capability, an d the low density absorbing body has a shorter total length of fiber per unit volume to have lower ink absorption capability. Joints between fibers are fitted under pressure so as to prevent interruption of ink due to admixing of air.
On the other hand, commonly owned Japanese Patent Application Laid-open Nos. 7-125232 (1995) and 6-40043 (1994) have proposed an ink tank having a liquid containing chamber which can increase an ink storage capacity per unit volume of the ink tank while the ink absorbing body is used and can realize stable ink supply.
In
FIGS. 14A and 14B
, shown are structural cross sections of the ink tank using the construction set forth above. As shown, ink tank
10
defines two spaces separated by a partition wall
13
serving as a separator wall provided with a communicating portion
20
, such as a communication hole. One space is a liquid containing chamber
12
being enclosed except for the communicating portion
20
of the partition wall
13
and directly holding ink. The other space forms a negative pressure generating member containing chamber
11
housing a negative pressure generating member
30
. In a wall surface forming the negative pressure generating member containing chamber
11
, an atmosphere communicating portion
14
, such as an atmosphere communication hole, for introducing atmospheric air into the container according to consumption of the ink, and a supply opening
16
having a pressure contact body
15
serving as ink leading member to a recording head not shown, are formed.
In
FIG. 14A
, a region where the negative pressure generating member holds the ink is shown by black dotted portion. On the other hand, the ink stored in the space is shown by cross-hatched portion. In order to prevent introduction of atmospheric air into the liquid containing chamber
12
through portions other than the atmosphere communication portion
14
, the negative pressure generating member
30
is required to be tightly fitted onto the inner peripheral wall of the negative pressure generating member containing chamber
11
.
Such ink tank achieving both of compact sizing and a high usage efficiency has been marketed by the assignee of the present invention and has been practically used. In the example shown in
FIG. 14A
, the pressure contact body
15
having a higher capillary force and a higher physical strength than the negative pressure generating member
30
, is provided in the supply opening
16
. The pressure contact body
15
is in contact with the negative pressure generating member
30
under pressure. In the vicinity of the communicating portion
20
between the negative pressure generating body containing chamber
11
and the liquid containing chamber
12
, an atmospheric air introduction groove
21
is provided in order to promote introduction of the atmospheric air into the liquid containing chamber
12
. In the vicinity of the atmosphere communicating portion, a space where no negative pressure generating member is present, namely a buffer chamber
18
is defined by means of a rib
17
.
However, the construction set forth above is premised on that a urethane foam is used as the negative pressure generating member. If the negative pressure generating member formed of fiber with maintaining the same shape, density distribution of the negative pressure generating member can be differentiated due to difference of elasticity and hardness thereof.
In certain density distribution, stable gas/liquid exchange can be disturbed to possibly cause failure of ink supply in spite of the fact that the ink is remained in the ink tank.
Therefore, the inventors have made an extensive study for the density distribution in the vicinity of the atmospheric air introduction groove. As a result, it has been found the following problems.
Namely, as shown in
FIG. 15A
, when the negative pressure generating member
30
in the peripheral portion
50
of the atmospheric air introducing groove
21
has higher density than that of other portion, a capillary force to be generated becomes higher so that the ink can be held in the vicinity of the negative pressure generating member
30
being in contact with the atmospheric air introducing groove
21
even when the ink is consumed so as not to be introduced into the communicating portion
20
. As a result, gas/liquid exchange is not initiated (
FIG. 15B
) or even if initiated, since the strength of the negative pressure upon gas/liquid exchange is determined by the portion
50
contacting with the atmospheric air introducing groove
21
of the negative pressure generating member
30
, negative pressure becomes strong. Then, most of the ink in the negative pressure generating member
30
can be consumed out before all of the ink within the liquid containing chamber
12
is consumed, resulting in interrupting an ink passage from the liquid containing chamber
12
to the ink supply opening
15
. It has been found that once the ink passage is interrupted, failure of ink supply can be caused.
The conventional atmospheric air introduction groove is formed into a buffer structure by providing a groove in a portion recessed in the partition wall. The density of the portion of the negative pressure generating member
30
in contact with the grooved portion is designed to be higher than the density of the portion in contact with the partition wall. In the case of the negative pressure generating member formed with a urethane foam, since the urethane foam has an appropriate elasticity, even when the urethane foam of the size greater than the volume of the negative pressure generating member containing chamber
11
is inserted thereinto to enhance tight contact with side walls, the urethane foam is compressed relatively uniformly so as not to cause substantial difference of density distribution.
However, the negative pressure generating member formed of fiber has low elasticity, particularly has little elasticity in the longitudinal direction of the fiber. Therefore, it has been found th
Iwanaga Shuzo
Shimizu Eiichiro
Udagawa Kenta
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