Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-03-01
2002-08-13
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06431672
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to ink jet printing devices. In particular, the present invention is an ink container having an ink reservoir fluidically coupled to an ink outlet. The ink reservoir is defined by a first capillary member positioned adjacent the ink outlet and a second capillary member spaced from the ink outlet by the first capillary member. The first capillary member has a high resistance to the flow of ink while the second capillary member has a low resistance to the flow of ink. An ink level sensing feature positioned adjacent the interface of the first and second capillary members provides a reliable and accurate indication of a low ink condition in the ink reservoir of the ink container.
BACKGROUND OF THE INVENTION
Ink jet printing systems frequently make use of an ink jet printhead mounted within a carriage that is moved back and forth across print media, such as paper. As the printhead is moved across the print media, a control system activates the printhead to deposit or eject ink droplets onto the print media to form images and text. Ink is provided to the printhead by a supply of ink that is either carried by the carriage or mounted to the printing system such that the supply of ink does not move with the carriage. For the case where the ink supply is not carried with the carriage, the ink supply can be in fluid communication with the printhead to replenish the printhead or the printhead can be intermittently connected with the ink supply by positioning the printhead proximate to a filling station to which the ink supply is connected whereupon the printhead is replenished with ink from the refilling station.
For the case where the ink supply is carried with the carriage, the ink supply may be integral with the printhead whereupon the entire printhead and ink supply is replaced when ink is exhausted. Alternatively, the ink supply can be carried with the carriage and be separately replaceable from the printhead or drop ejection portion.
Regardless of where the supply of ink is located within the printing system, it is critical that the printhead be prevented from operating when the supply of ink is exhausted. Operation of the printhead once the supply of ink is exhausted results in poor print quality, printhead reliability problems, and, if operated for a sufficiently long time without a supply of ink, can cause catastrophic failure of the printhead. This catastrophic failure results in permanent damage to the printhead. Therefore, it is important that the printing system be capable of reliably identifying a condition in which the ink supply is nearly or completely exhausted. In addition, the identification of the condition of a nearly or completely exhausted ink supply should be accurate, reliable, and relatively low cost, thereby tending to reduce the cost of the ink supply and the printing system.
One type of ink container including a capillary reservoir with a binary ink level sensor is disclosed in the U.S. Pat. No. 5,079,570 to Mohr et al. entitled “Capillary Reservoir Binary Ink Level Sensor” which is assigned to the same assignee as the instant application and which is incorporated herein in its entirety by reference thereto. As illustrated in prior art
FIG. 2
of the instant application, Mohr et al. is directed to an ink container
10
that includes a housing
12
within which is provided a capillary reservoir
14
for storing a quantity of ink. In prior art
FIG. 2
, the capillary reservoir
14
has dashed horizontal lines where there is ink and no dashed horizontal lines where there is no ink. On one end of the housing
12
is an ink outlet
16
.
An ink level sensor
18
is provided on one surface of the housing
12
. The sensor
18
comprises a C-shaped, transparent, ink level sensing tube
20
with first arm or port
20
a
a first distance above the outlet
16
and a second arm or port
20
b
a shorter distance above the outlet
16
. Both the first and second ports
20
a
,
20
b
are ported through the housing
12
to the capillary reservoir
14
. In operation, as long as the ink level
22
is above the first port
20
a
, the tube
20
of the ink level sensor
18
is full of ink and is in static equilibrium. However, when the ink level
22
reaches the top port
20
a
, the ink is sucked from the tube
20
of the ink level sensor
18
and into the capillary reservoir
14
due to an imbalance in the capillary pressures at the ink/air interfaces between the capillary reservoir
14
and the top port
20
a
. The resulting sudden (i.e., instantaneous) depletion of ink in the tube
20
of the ink level sensor
18
provides a binary fluidic indicator. Since the tube
20
of the ink level sensor
18
is transparent, a sensing device, such as light detector
24
, positioned adjacent to the tube
20
, can detect when the tube
20
is empty (i.e., detect the binary fluidic indicator), whereupon a printing system controller (not shown), coupled to the light detector
24
via transmission line
26
, can notify a user of the low ink condition of the ink reservoir
14
of the ink container
10
.
A drawback of the ink container
10
is that as ink is drained from the ink reservoir
14
, the ink level
22
, otherwise known as an ink front, since it forms a dividing line between an ink filled portion
28
of the ink reservoir
14
and an empty portion
30
of the reservoir
14
, is very uneven and ever-changing. This uneven ink front
22
(i.e., ink level) exhibits an ink front variation
32
defined by the difference between a highest point
34
of the ink filled portion
28
of the ink reservoir
14
and a lowest point
36
of the empty portion
30
of the ink reservoir
14
. This ink front variation
32
causes variation in the time at which the ink front
22
reaches the top port
20
a
of the ink level sensing tube
20
and the tube
20
drains. The greater the ink front variation
32
(i.e., unevenness), the greater the uncertainty in the amount of ink in the ink cartridge
10
at the time the ink level sensing tube
20
is drained. Moreover, because of this ink front variation
32
, the time required for the ink front
22
to reach the ink level sensing tube
20
(i.e., the timing of the binary fluidic signal indicating a low ink condition for the ink container
10
) can vary from one ink container
10
to the next. As such, it is relatively difficult for a printing system to precisely determine what the ink level is in any given ink container
10
.
There is a need for an ink container that allows a printing system to reliably and accurately determine the ink level within an ink reservoir of the ink container. The ink container design should substantially eliminate the container-to-container variation in the indication of a low ink condition with an ink container. In other words, the binary fluidic signal for a low ink condition produced by an ink level sensor should occur in each and every container at substantially the same targeted ink level (i.e., with substantially the same amount of ink remaining in each and every ink container). Lastly, the ink container should be relatively easy and inexpensive to manufacture.
SUMMARY OF THE INVENTION
The present invention is a replaceable ink container for providing ink to a printhead of a printing system. The ink container has a fluid outlet configured for connection with the printhead. The ink container includes an ink reservoir having a first capillary member having a first capillary pressure, and a second capillary member having a second capillary pressure that is different than the first capillary pressure.
In one aspect of the present invention, the second capillary pressure is greater than the first capillary pressure such that the second capillary member has a higher resistance to ink flow than the first capillary member. In another aspect of the present invention, an ink level sensor senses a low ink condition of the ink reservoir. The ink level sensor includes a C-shaped tube mounted to the ink container. The C-shaped tube has first and second ports that fluidically communicate wit
Ardito Michael S.
Thielman Jeffrey L.
Walker Ray A.
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