Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2000-05-08
2003-04-29
Vo, Ahn T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S086000
Reexamination Certificate
active
06554413
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink supply mechanism that supplies ink from an ink container to an ink jet recording head. The invention also relates to an ink jet cartridge and an ink jet recording apparatus, which are provided with the ink supply mechanism.
2. Related Background Art
The recording apparatus, which is used as a recording apparatus for a printer, a copying machine, or a facsimile equipment, or which is used as an output device for a complex apparatus that includes a computer, a word processor, or for a work station, among some others. The recording apparatus is then structured to record images (including characters, symbols, or the like) on a recording material (a recording medium) such as a recording sheet or a thin plastic sheet (an OHP or the like).
The recording apparatuses thus structured are classified into various types, such as a ink jet type, a wire-dot type, a thermosensitive type, or a thermal transfer type, by a recording method of recording means adopted by each of them. Of those mentioned here, the recording apparatus of ink jet type (ink jet recording apparatus) is the one that records by discharging ink to a recording material from the recording head serving as recording means. This recording means is easily made compact, and also, with such compact head, highly precise images are made recordable at higher speeds. Here, among many other advantages, there is the one that recording is possible at a lower running cost on an ordinary recording sheet without any particular treatment given to it. Also, this apparatus is of non-impact type, making a lesser amount of noises, while producing color images with ease using multiple colors.
Here, in particular, the ink jet type recording means that discharges ink by the utilization of thermal energy makes it easier to manufacture the one having a highly precise arrangement of liquid paths (discharge ports) with the formation of the electrothermal transducing elements, electrodes, liquid path walls, ceiling plate, and others, which are provided on a substrate produced by means of film formation through etching, vapor deposition, sputtering, and other semiconductor manufacturing processes. Thus, the recording means is made compact still more in this manner. Also, utilizing the advantages of the IC technologies and the micromachining techniques the recording means can be elongated easily or its surfacing (two-dimensional arrangement) can be effectuated easily to make the recording means available in full multiple condition or to assemble it in a higher concentration.
The recording means of an ink jet recording apparatus described above is generally provided with an ink discharge unit that creates fine ink droplets; an ink supply unit that leads ink to the ink discharge unit; and an ink tank unit that stores ink in it. The ink tank unit is provided with a porous absorbent formed by urethane form or the like. Ink is absorbed and retained in such absorbent. Ink thus absorbed in the absorbent is not allowed to leak by means of the capillary force generated by the fine holes of the absorbent irrespective of the posture in which the ink jet recording head is placed. The ink tank is usable without staining the interior of the recording apparatus, the desk, the hands, or the like. Ink stored in an ink container of the kind is supplied to the recording head from the ink supply port provided for the ink container.
Nevertheless, with the ink tank thus structured, pigments are sedimented if the ink that uses pigments as colorants is stored in it for a long time, although there is no problem when the ink that uses dyestuffs as colorants is stored in it. Then, the uneven concentrations, that is, the concentrations that become different depending on locations, are caused to occur in the ink which is stored in the ink container.
Usually, the pigment ink is obtained by crashing finely the colorant which is insoluble to water after being mixed with copolymeric resin or the so-called interfacial active disperse agent, and then, diluted with water, oil, or some other solvent. The pigment particles themselves are not soluble to water. Therefore, when coated on a printed object, the pigment ink is superior to the dyestuff ink in terms of the water resistance. Further, the pigment particles withstand light well. As a result, the pigment ink is not discolored even if exposed to light for a long time. It demonstrates an excellent performance particularly with the printed object which should be shown on the wall or the like for a long time. This is because the pigment ink is widely used for general printed objects. However, although the fine solid particles, such as pigments, are allowed to float on liquid, its sedimentation should take place inevitably if the specific gravity thereof is greater than that of the solvent liquid (medium).
Here, the sediment speed of the particles can be expressed as follows:
u=
2
r
2
(&rgr;
2
−&rgr;
1
)
g/
9&eegr; (1)
where r is the radius of the particle which is assumed to be spherical; &rgr;
1
and &rgr;
2
are the concentrations of the particle and medium, respectively; g is the gravitational acceleration; and &eegr; is the viscosity coefficient. The above expression (1) is called Stokes' formula.
Also, besides receiving the sedimental action brought by the gravity, the particles are influenced by the thermal motion of the medium molecules, thus continuing the Brawnian motion without interruption. By the Brawnian motion, there occurs the diffusion which is the action opposite to the sedimental one. With this diffusion, it is intended to implement the distribution of the particles uniformly.
The perpendicularly concentrated distribution of the pigment ink contained in an ink container is determined by the aforesaid sedimental action and the diffusion brought by the Brawnian motion. Now, given the concentration of pigment ink on the bottom of an ink container as Co, the concentration C at a height h from the bottom can be expressed as follows:
ln (
C/Co
)=−4&pgr;
r
3
(&rgr;
2
−&rgr;
1
)
g·h/
3
kT
(2)
where r is the radius of the particle which is assumed to be spherical; &rgr;
1
and &rgr;
2
are the concentrations of the particle and medium, respectively; g is the gravitational acceleration; k is the Boltzman's constant; and T is the temperature of the pigment ink designated by the absolute temperature.
Now, for example, if the radius r of the particle is 200 nm; the temperature of ink T is 27° C.; the concentration of the particle &rgr;
1
is 1,400 kg/M
3
; and the concentration of the medium &rgr;
2
is 1,000 kg/M
3
, the ratio of concentration of 2% occurs per difference of 1 mm high. Also, if the viscosity of ink in this case is assumed to be 0.037 poise, it is calculated that the particle is sedimented to approximately 5 cm in two months, that is, the sedimental speed of the particle is worked out to be approximately 2.5 cm/month.
In practice, however, there is no appearance of such abrupt changes of concentration as indicated by the sedimental speed as described above. Conceivably, it is because of the constant convection current given to ink (liquid) stored in an ink container, which results in an even mixture eventually, and functions to prevent the occurrence of sediment of the particles.
In other words, the environment where an ink tank is kept is such as on a shelf in a room or in the interior of a printer located in a room. Therefore, an ink tank is always affected by the changes of the environmental temperature. The changes of the room temperature following the turning on and off of the air conditioning, and further, the temperature changes in the interior of a printer following the turning on and off of the printer power source may easily bring about the temperature changes of 40° C. to 50° C. Then, when a printer is on standby or in operation, the heat generation from the interior of the printer changes constantly following the turning on and off of a motor to drive
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