Liquid supply system, ink jet recording head, ink jet...

Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means

Reexamination Certificate

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Details

C347S093000

Reexamination Certificate

active

06805437

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording head, an ink jet recording apparatus employing such inkjet recording head, and a liquid supply system suitable for use therein.
2. Related Background Art
Among various recording methods in printers or the like, the ink jet recording method for forming a character or an image on a recording medium by discharging ink from a discharge port (nozzle) is widely employed in recent years because it is a non-impact recording method of now noise level capable of high-density and high-speed recording operation.
An ink jet recording apparatus is generally provided with an ink jet recording head, means for driving a carriage supporting such recording head, means for conveying the recording medium, and control means for controlling these components. An apparatus executing the recording operation under such carriage motion is called serial scan type. On the other hand, an apparatus executing the recording operation by the conveying of the recording medium only, without moving the ink jet recording head is called line type. In the ink jet recording apparatus of line type, the ink jet recording head is provided with a plurality of nozzles arranged over the entire with of the recording medium.
The ink jet recording head is provided with energy generating means for generating discharge energy to be given to the ink in the nozzle, in order to discharge therefrom an ink droplet. The energy generating means can be an electromechanical converting element such as a piezo element, an electrothermal converting element such as a heat generating resistor, an eletromagnetic wave-mechanical converting element or an electromagnetic wave-thermal converting element for converting electromagnetic wave such as electric wave or laser light into mechanical vibration or heat. Among these, a method for discharging ink droplet by thermal energy can achieve recording of high resolution because the energy generating means can be arranged at a high density. Particularly an ink jet recording head utilizing an electrothermal converting element as the energy generating means can be made compact more easily than a head utilizing the electromechanical converting element, and provides advantages of easily achieving high-density configuration and low manufacturing cost, utilizing the IC technology and the micro fabrication technology showing remarkable progress and improvement in reliability in the semiconductor area.
In the system of ink supply to the ink jet recording head, there are known so-called integral ink tank system in which an ink tank containing the ink is integrated with the ink jet recording head, so-called separated ink tank system in which the ink tank is separated from the ink jet recording head, so-called tube supply system in which the ink tank and the ink jet recording head are connected by a tube, and so-called pit-in system in which the ink tank and the ink jet recording head are provided separately but the ink jet recording head is moved to the position of the ink tank whenever required and is connected thereto for executing ink supply from the ink tank to the ink jet recording head.
When the capacity of the ink tank is increased in order to reduce the frequency of replacement thereof, the weight thereof increases. This means an increase in the weight of the carriage in the recording apparatus of serial scan type. In consideration of this fact, the ink jet recording apparatus of serial scan type requiring the ink tank of a large capacity for example for outputting a large sized recorded image often employs the tube supply system or the pit-in system. Among these, the tube supply system capable of continuous recording over a long period is often employed since, in the pit-in system, the recording operation has to be interrupted during the ink supply operation.
In the following the ink supply system of an ink jet recording apparatus of tube supply system will be explained with reference to FIG.
25
.
The ink supply system shown in
FIG. 25
is provided with a main tank
1204
containing ink therein, a supply unit
1205
on which the main tank
1204
is detachably mounted, and a recording head
1201
connected to the supply unit
1205
through a supply tube
1206
.
The supply unit
1205
is provided therein with an ink chamber
1205
c
, which is open to the air by an air communicating port
1205
g
at the upper portion and is connected at the bottom portion to the supply tube
1206
. On the supply unit
1205
, there are fixed a hollow ink supply needle
1205
a
and a hollow air introducing needle
1205
b
of which lower ends are positioned in the ink chamber
1205
c
and higher ends protrude from the upper face of the supply unit
1205
. The lower end of the ink supply needle
1205
a
is positioned lower than that of the air introducing needle
1205
b.
The main tank
1204
is provided at the bottom thereof with two connector portions composed for example of rubber stoppers for closing the interior of the main tank
1204
, whereby the ink tank singly has a hermetically closed structure. The mounting of the main tank
1204
to the supply unit
1205
is executed in such a manner that the ink supply needle
1205
a
and the air introducing needle
1205
b
respectively penetrate the connector portions and enter the interior of the main tank
1204
. Since the lower ends of the ink supply needle
1205
a
and the air introducing needle
1205
b
are positioned as explained in the foregoing, the ink in the main tank
1204
is supplied to the ink chamber
1205
c
through the ink supply needle
1205
a
and the air is introduced into the main tank
1204
through the air introducing needle
1205
b
so as to compensate the pressure decrease resulting in the main tank
1204
. When the ink is supplied into the ink chamber
1205
c
until the lower end of the air introducing needle
1205
a
is immersed in the ink, the ink supply from the main tank
1204
to the ink chamber
1205
c
is terminated.
The recording head
1201
is provided with a sub tank
1201
b
for containing ink of a predetermined amount, an ink discharge portion
1201
g
having an array of plural nozzles for ink discharge, and a flow path
1201
f
connecting the sub tank
1201
b
and the ink discharge portion
1201
g
. In the ink discharge portion
1201
g
, a face having the nozzle apertures is directed downwards, so that the ink is discharged downwards. Each nozzle in the ink discharge portion
1201
g
is provided with the aforementioned energy generating means. The sub tank
1201
b
is positioned higher than the ink discharge portion
1201
g
, and the supply tube
1206
is connected to the sub tank
1201
b
. Between the sub tank
1201
b
and the flow path
1201
f
, there is provided a filter
1201
c
having a fine mesh structure in order to prevent clogging of the nozzle resulting from the entry of fine foreign particles into the ink discharge portion
1201
g.
The area of the filter
1201
c
is so selected that the pressure loss in the ink does not exceed a tolerance value. The pressure loss in the filter
1201
c
increases as the mesh thereof is fiber or the ink flow rate through the filter is higher, but is inversely proportional to the area thereof. Since the pressure loss tends to become higher in the recent recording head of high-speed, multi-nozzle and small recording dots, the area of the filter
1201
c
is selected as large as possible to suppress the increase in the pressure loss.
Since the nozzle in the ink discharge portion
1201
g
is open to the air and directed downwards, the interior of the recording head
1201
has to be maintained at a negative pressure relative to the atmospheric pressure in order to prevent ink leakage from the nozzle. On the other hand, an excessively large negative pressure causes entry of gas into the nozzle, whereby the nozzle becomes incapable of discharging ink. Therefore, in order to maintain a suitable negative pressure in the recording head
1201
, the recording head
1201
is so positioned that the nozzl

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