Inkjet recording head and inkjet recording device

Details Inkjet recording head and inkjet recording device Inkjet recording head and inkjet recording device

2002-07-09

2004-04-20

Vo, Anh T. N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Fluid or fluid source handling means

Reexamination Certificate

active

06722761

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inkjet recording head which incorporates a tank for containing ink, and an inkjet recording device including ink supplying means for supplying ink to the inkjet recording head through a needle.
2. Description of the Related Art
Image recording devices are used in diverse applications, for example, printers, copying machines, or facsimile machines, or recording devices used as output devices of composite electronic devices (including, for example, computers or word processors), or as output devices of workstations. These recording devices are constructed so as to record an image (including characters, drawings, designs, etc.) on a recording material (recording medium) such as paper or a thin plastic plate, with the image being recorded based on image information. One form of such a recording device for forming an image on a recording medium is an inkjet recording device which discharges very small ink droplets from a very small ink-discharge nozzle or opening. In general, an inkjet recording head of the inkjet recording device comprises a recording head body which includes an ink-discharge nozzle or nozzles for discharging ink droplets and a tank for containing ink supplied to the recording head body. The ink is guided from the tank to the recording head body. An energy generating member, such as a heat-generating element or a piezoelectric element, disposed close to the ink-discharge nozzle is driven based on a recording signal, causing ink droplets to be discharged from the ink-discharge nozzle and to stick onto the recording medium, whereby a recording operation is carried out. The inkjet recording device is what is called a nonimpact recording device, and has the advantages of, for example, being capable of performing a recording operation with high speed and on various types of recording media and producing almost no noise during the recording operation. Accordingly the inkjet recording device is widely used.
Among the different types of inkjet recording devices, a bubblejet-type inkjet recording head which discharges ink using heat energy can perform a recording operation with high resolution because its ink-discharge nozzles for discharging ink can be disposed very close to each other. In particular, a bubblejet-type inkjet recording head which uses an electrothermal converting member as an energy-generating source can easily be made more compact. In addition, the advantages of integrated circuit (IC) technology and micro-fabrication technology, which have improved considerably and which have become very reliable in the semiconductor field in recent years, can satisfactorily be made use of, so that high-density mounting can be easily achieved, thereby causing the bubblejet-type inkjet recording head to be advantageous from the viewpoint of low manufacturing costs.
Many methods of supplying ink to the tank of the inkjet recording head, such as an on-carriage tank method, a pit-in method, and a continuous supplying method using a tube, have been proposed. Among these methods, the continuous supplying method using a tube is primarily used in large recording devices and business recording devices because the capacity of the tank incorporated in the inkjet recording head can easily be made large, running cost is low, and the tank does not need to be frequently replaced.
As mentioned above, the inkjet recording head of such an inkjet recording device comprises a recording head body (discharge unit) and a tank for storing ink. Ink in a main tank that is fixedly provided at the recording device body is supplied to the tank (which is hermetically sealed) of the inkjet recording head through a tube. From this tank, the ink is supplied to the recording head body disposed downstream from the tank.
When the inkjet recording device is constructed in this way, since the tube and the tank are hermetically sealed except from the main tank, if, for example, no air bubbles are produced due to ink discharge or expansion or coagulation of dissolved air inside the tank of the inkjet recording head, an amount of ink which is the same as the amount of ink discharged is automatically supplied from the main tank to the tank of the inkjet recording head.
However, even a very small amount of air mixed in the ink gradually accumulates over time, and very small amounts of air can pass through, for example, the wall of the tube and gradually accumulate in the entire ink path. Therefore, the amount of air in the tank of the inkjet recording head increases over time, causing the amount of ink in the tank to gradually decrease. When the amount of ink in the tank decreases in this way, it is necessary to forcefully supply ink by, for example, suction generating means.
Here, the most generally used means for forcefully supplying ink supplies ink by providing a pressure difference between the main tank and the tank of the inkjet recording head by generating negative pressure in the tank by a suction generating device such as a pump. In other words, as shown in
FIGS. 8A and 8B
, a total of two tubes, a tube
114
for supplying ink
128
from a main tank
116
and a tube
115
connected to a suction generating device, such as a pump
117
, are connected to one tank
111
.
Although there are slight differences depending upon the frequency with which the inkjet recording head
101
is replaced, connecting means used in the structure shown in
FIGS. 8A and 8B
is generally and optimally constructed by providing openings
119
and
120
in the tank
111
of the inkjet recording head
101
and by closing the openings
119
and
120
by corresponding resilient joints
121
and
122
, such as rubber plugs; and by mounting hollow needles
112
and
113
to ends of the corresponding tubes
114
and
115
and by passing the needles
112
and
113
through the corresponding resilient joints
121
and
122
and inserting them into the tank
111
. The connecting means does not cause the ink
128
to drip even if there is a small amount of ink remaining inside the tank
111
when the inkjet recording head
101
is replaced. Therefore, in the connected state, the connecting means can reliably seal the tank
111
in order to construct an ink supply path with no ink leaks, thereby providing various advantages such as a simplified structure.
In the structure for supplying the ink
128
to the inkjet recording head
101
, a carriage (not shown) which holds the inkjet recording head
101
is provided. The two hollow needles
112
and
113
are arranged vertically at a fixed position relative to the carriage. Holes
112
a
and
113
a
are formed in ends of or side surfaces near the ends of the corresponding needles
112
and
113
. The upper needle
113
is connected to the pump
117
through the tube
115
, and is constructed so that it can suck air in the tank
111
of the inkjet recording head
101
by operation of the pump
117
. The lower needle
112
is connected to the main tank
116
through the tube
114
, and is constructed so that it can supply the ink
128
in the main tank
116
into the tank
111
of the inkjet recording head
101
. Therefore, by the pump
117
, the air in the tank
111
of the inkjet recording head
101
is sucked through the tube
115
and the upper needle
113
. In addition, the ink
128
is supplied into the tank
111
from the main tank
116
through the other tube
114
and the lower needle
112
.
A mechanism for holding and securing the inkjet recording head
101
is provided at the carriage (not shown). By operating a carriage head lever, this mechanism can secure the inkjet recording head
101
to the carriage, and can allow removal of the inkjet recording head
101
from the carriage.
A mechanism for passing the two needles
112
and
113
through the resilient joints
121
and
122
of the inkjet recording head
101
and inserting them into the tank
111
is provided at the carriage. This mechanism may move in response to movement of the carriage head lever.
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