Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2002-01-30
2004-03-09
Vo, Anh T.N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06702433
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink supply mechanism for supplying ink to an ink jet head, and also, relates to an ink jet recording apparatus.
2. Related Background Art
Of the recording methods for a printer or the like, the ink jet recording method that records on a recording medium, such as a recording paper sheet, by discharging ink from the discharge ports (nozzles) has been widely adopted in recent years, because it performs recording operation at high speed in high density by use of the low-noise non-impact recording method.
In general, an ink jet recording apparatus comprises means for driving a carrier that mounts an ink jet head thereon; conveyance means for conveying a recording paper sheet; and control means for controlling them, among some others. Also, there is the one which uses electromechanical converting elements, such as piezoelectric elements, to exert pressure on ink in order to generate energy for discharging ink from the nozzle portion of an ink jet heat; irradiates electromagnetic waves, such as laser, to generate heat; generates heat for bubbling; or uses electrothermal converting elements each having heat resistive element for heating liquid for bubbling. Among them, the ink jet recording apparatus that adopts the method for discharging ink droplets utilizing thermal energy makes it possible to perform recording in high resolution with the nozzles that can be arranged in high density. Particularly, the ink jet head that uses electrothermal converting elements as energy generating elements can be made smaller with ease, and by the application of the IC technologies and micro-machining techniques, which have made remarkable technical advancement and enhancement of reliability in the field of semiconductor manufacturing in recent years, the ink jet head of the kind can be assembled in high density at lower costs utilizing the advantages of these technologies and techniques sufficiently.
Now,
FIG. 5
shows one example of the conventional ink jet recording apparatus that adopts the method of discharging ink droplets utilizing thermal energy, in which the discharge nozzle
101
g
of a recording head
101
is a fine hole. There is no particular valve mechanism provided for the nozzle. With the interior of the nozzle being kept in negative pressure, the nozzle enables ink to be given meniscus to prevent ink leakage from the nozzle, as well as to prevent the air from entering the nozzle from the atmosphere. Ink is discharged by pushing out ink in the discharge nozzle
101
g
by means of film-boiling energy of the heater arranged in the vicinity of the discharge nozzle
101
g
. After discharge, ink is filled again in the nozzle by means of capillary force of the discharge nozzle
101
g
. This cycle is repeated, and ink is absorbed from the main tank
104
through a tube
106
as required.
In the recording head
101
, there are arranged a filter
101
c
having a fine mesh structure to prevent the discharge nozzle
101
g
, which is a fine hole, from being clogged by dust particles; the flow path
101
f
that connects the filter
101
c
and the discharge nozzle
101
g
; and the sub-tank
101
b
for retaining ink in a given amount, which is arranged on the upstream side of the filter
101
c
, here, ink being supplied thereto by way of the tube
106
from the main tank
104
installed on the main body of the ink jet recording apparatus.
The main tank
104
and the supply base
105
are structured as disclosed in the specification of Japanese Patent Publication 2929804, and the liquid connector
104
b
on the bottom face of the main tank
104
is detachably installed on two hollow needles
105
a
and
105
b
fixed to the supply base
105
.
In the supply base
105
, there is arranged the ink chamber
105
f
which is released to the atmosphere by means of an atmospheric port
105
g
. The hollow needles
105
a
and
105
b
are arranged in such a manner that the height of the low end of the hollow needle
105
b
is made different from that of the hollow needle
105
a
so as to keep it in ink in the ink chamber
105
f
. The ink chamber
105
f
is structured to be communicated with the tube
106
from the bottom portion of the ink chamber
105
f
. Then, when the lower end of the hollow needle
105
b
appears on the liquid surface of the ink chamber
105
f
as the liquid surface of the ink chamber
105
f
is lowered following the reduction of ink in the ink chamber
105
f
due to ink consumption, the air enters the interior of the main tank
104
from the lower end of the hollow needle
105
b
. Thus, ink in the main tank
104
flows out to the ink chamber
105
f
to raise the liquid surface of ink in the ink chamber
105
f
to cause the lower end of the hollow needle
105
b
to be immersed again in ink. With the structure thus formed, ink in the main tank
104
is drawn out gradually.
Also, on the lower part of the main tank
104
, the electrode
104
e
is arranged to be in contact with ink, which is in conduction with the contact point
105
j
provided for the supply base
105
. To the contact point
105
j
and the hollow needle
105
b
, the detection circuit
105
h
, which measures the electric resistance of ink, is connected to detect the presence and absence of ink.
In the sub-tank
101
b
, the air that permeates the resin material of the tube
106
or the like to enter the sub-tank, and the air dissolved and retained in ink is accumulated as well. Therefore, the accumulated excessive air is sucked out together with ink periodically from the side wall of the sub-tank
101
b
by means of the exhaust tube
110
a
and the exhaust pump
110
c
. Then, the sub-tank is closed by the valve
110
b
when the exhaust is completed to maintain the ink discharge characteristics.
Also, if overly viscous ink causes the discharge nozzle
101
g
to be clogged or any excessive bubble that may be generated at the time of discharge ensues in clogging, the recovery of ink discharge characteristics is made by sucking ink intensively from the discharge nozzle
101
g
by means of the suction pump provided for the suction cap
107
a
of the recovery unit
107
.
Now, however, even if a step is taken to deal with any unexpected movement of ink (such as ink being returned from the head side to the ink chamber
105
f
) with the provision of a mechanism, which is additionally provided for the ink supply mechanism of the conventional structure exemplified as described above, to close the tube
106
on the midway when operation is at rest, there is still a possibility that ink flows out externally from the atmospheric communication port
105
g
if the apparatus shown in
FIG. 5
is inclined to make its right side higher, for example, due to the occurrence of unusual situation under which the apparatus shown in
FIG. 5
moves to change its installation site.
Further, when the ink liquid surface of the ink chamber
105
f
is caused to part from the end portion of the hollow needle
105
b
, the leading end of the hollow needle
105
b
is released to the atmosphere. In this state, the air is induced from the hollow needle
105
b
into the main tank
104
, and ink in the main ink tank
104
flows out to the ink chamber
105
f
along with the induction of the air. Thus, unless the leading end portion of the hollow needle
105
b
is clogged by ink, ink in the main tank
104
flows out continuously, and in the worst case, there may occur the event that all ink in the main tank
104
flows out into the ink chamber
105
f
. The ink chamber
105
f
is not capable enough to receive all ink in the main tank
104
. As a result, ink that flows out from the ink chamber
105
f
is allowed to flow out externally from the atmospheric communication port
105
g
eventually. In addition, if the volume of the ink chamber
105
f
is made large enough to receive all ink in the main tank
104
, the structure of the apparatus becomes extremely large, which is not practicable.
Meanwhile, it is an important technique to detect ink remainders in an ink jet recording appara
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