Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2002-07-26
2004-04-27
Nguyen, Thinh (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06726315
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid discharge recording apparatus that records on a recording material by discharging recording liquid. The invention also relates to a liquid supplying device used therefore.
2. Related Background Art
As a mode of a recording apparatus that forms images (characters, graphics, patterns, and the like are called images inclusively) on a recording material, such as recording sheet, there is an ink jet recording apparatus that discharges micro ink droplets from fine discharge ports. Generally, the ink jet recording apparatus provided with a recording head having nozzles used for discharge ink droplets, and an ink that contains ink to be supplied to the recording head. Then, ink is induced from the ink tank to the recording head, and the energy-generating element, such as heat generating element or piezoelectric element, which is installed near the discharge port of each nozzle of the recording head, is driven in accordance with recording signals to discharge ink droplets from each discharge port for recording by the adhesion thereof to a recording material. This ink jet recording apparatus is the so-called non-impact type recording apparatus that makes it possible to perform high-speed recording, and record on various kinds of recording mediums, and has an advantage, among others, that almost no noise is generated at the time of recording, thus being popularized and widely used.
For an ink jet recording apparatus of the kind, it is required to keep ink always under a negatively pressurized condition at the discharge port in order port, with the exception of a designated amount of micro ink droplets to be discharged, that is, to prevent ink leakage from the discharge port when driving is not given (recording on standby or the like), and also, to prevent any excessive ink flow out from the discharge port in the process of recording.
Conventionally, in order to keep ink under a negatively pressurized condition, a structure is adopted to make the height of the ink tank that contains ink lower than that of the discharge port for the utilization of water-level difference. Then, in order to keep the holding pressure of ink regulated by such water-head difference at a constant level under any circumstances, there is a need for the ink tank to be capable of changing the volume thereof in accordance with the amount of ink retained therein. For example, the structure should be arranged so that when the amount of ink inside the ink tank is reduced by a supply of ink to a recording head, the volume of the ink tank is reduced accordingly or when the amount of ink inside the ink tank is increased with a flow-in of ink from the recording head, the volume of the ink tank is increased accordingly. In generally, therefore, a flexible container, such as an aluminum-laminated bag, is used.
FIG. 8
is a view that schematically shows the structure of an ink jet recording apparatus provided with the conventional ink-supplying device. This apparatus has a recording head
110
of ink jet method that records by discharging ink, and an ink supplying device that supplies ink to the recording head
110
.
The ink supplying device is provided with an aluminum-laminated flexible bag (ink tank)
210
; a tank case
200
, which is a highly robust housing to cover the aluminum-laminated bag
210
; an ink supply tube
170
, which is a pipe type connecting member to supply ink from the aluminum-laminated bag
210
to the recording head
110
; and a joint
190
that couples the ink supply tube
170
with the aluminum-laminated bag
210
.
The recording head
110
is provided with nozzles
150
that discharge ink; a common liquid chamber
140
serving as a pool to supply ink evenly to each of the nozzles
150
; a sub-tank
120
that provisionally retains ink supplied from the ink supplying device before being supplied to the common liquid chamber
140
; a filter
130
for removing dust particles contained in ink supplied from the sub-tank
120
to the common liquid chamber
140
; and ink suction tube
180
for sucking ink by use of a pump (not shown) when ink is supplied for the first time to a recording head yet to be used.
For this ink jet recording apparatus, the aluminum-laminated bag
210
is filled with ink to form a closed space where no air is present. Ink is supplied to the recording head
110
from the aluminum-laminated bag
210
through the joint
190
and the ink supply tube
170
. Inside the recording head
110
, a certain amount of ink is retained in the sub-tank
120
. Then, from the sub-tank
120
, ink is supply to each of the nozzles
150
through the common liquid chamber
140
. The sub-tank
120
is not filled with ink up to its total capacity, but there is a remaining portion to enable the air to be accumulated. Also, a rubber plug, valve, or the like (not shown) is used here to airtightly close the ink suction tube
180
so as not to allow ink leakage. At the tip of each nozzle
150
, meniscus of ink
160
is formed, and by the surface tension of the meniscus
160
, ink is held near the discharge port at the tip of nozzle
150
so as not to allow it to drop down. At this juncture, the aluminum-laminated bag
210
is positioned lower than the recording head
110
to generate a water-head difference h between the discharge port at the tip of nozzle
150
and the ink outlet of the aluminum-laminated bag
210
(the portion where the joint
190
is installed) so that the meniscus of ink
160
is positioned appropriately inside the nozzle
150
, while making it possible to prevent ink from being dropped down by enabling the surface tension work appropriately.
In this conventional ink jet recording apparatus, when the inner temperature of the recording head
110
rises due to heat generation or the like along with the recording operation, the air in the sub-tank
120
expands to increase the inner pressure of the sub-tank
120
. Then, ink in the sub-tank
120
flows inversely to the ink tank
200
through the ink supply tube
170
, thus eliminating the pressure increase in the sub-tank
120
. The ink thus inversely flows is contained in the aluminum-laminated bag
210
. The aluminum-laminated flexible bag is deformed to swell. In this way, it deals with the increased amount of ink along with the inverse flow of ink form the recording head
110
. As a result, the negatively pressurized condition of ink in the recording head
110
is kept at a constant level, and no change occurs in the meniscus
160
that prevents ink from being dropped down.
Also, in the ink jet recording apparatus, when ink inside the recording head
110
is consumed by the recording operation, ink inside the sub-tank
120
is reduced to lower the pressure in the sub-tank
120
. Therefore, the ink inside the aluminum-laminated bag
210
flows in the sub-tank
120
through the ink supply tube
170
to eliminate lowering the pressure in the sub-tank
120
. In this way, ink in the aluminum-laminated bag
210
is reduced to deform the aluminum-laminated flexible bag
210
for the performance of smooth ink supply.
In this manner, by the flow of ink between the sub-tank
120
and the aluminum-laminated bag
210
, it is possible to keep the negatively pressured condition of ink in the recording head
110
at a constant level. In other words, the increase or decrease of pressure in the recording head
110
and in the entire system of the ink supplying device is absorbed by the increase or decrease of the capacity resulting from the deformation of the aluminum-laminated bag
210
.
As described above, for the conventional ink jet recording apparatus, pressure exerted on ink is adjusted by the deformation of the aluminum-laminated flexible bag
210
in order to prevent ink from dropping down, while making the smooth ink supply possible. Therefore, it is required for the aluminum-laminated bag
210
to be flexible and deformable. Further, in order not to impede the deformation of the aluminum-laminated bag
210
, particularly, not to impede increasing volume t
Koizumi Yutaka
Umeyama Mikiya
Yamaguchi Yukuo
Yamakubo Takeshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Huffman Julian D.
Nguyen Thinh
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