Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2001-11-01
2003-07-15
Nghiem, Michael (Department: 2863)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06592215
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention and Related Art
The present invention relates to a liquid ejection recording head for placing liquid such as ink on a recording medium such as paper.
In the field of printing apparatuses, in particular, printing apparatuses which employ an inkjet method, improvement in quality and/or speed in color recording is one of the important considerations.
In order to improve recording quality, it is necessary for a recording head to eject ink droplets that are as small as possible. In order to improve recording speed, it is necessary for an ink supply path to be smooth and stable in its ink delivery performance.
The ink ejecting performance of a recording head which ejects small ink droplets is easily affected by foreign objects which have entered the recording head. Thus, in order to prevent foreign objects from entering the recording head, the recording head may be provided with a filter, which is placed in the ink path of the recording head.
It is common knowledge that, generally, when a recording head and an ink container are integrated in the form of a cartridge, a filter is placed in a certain position in the ink supply path between the ink container and recording head, whereas when a recording head is rendered independent from an ink container, a filter is placed at one end of the ink supply tube which connects the recording head and ink container.
Shown in
FIGS. 3 and 4
is the structure of the ink inlet (ink supply tube) portion of a conventional recording head, in which the recording head and ink container are independent from each other. Referring to
FIG. 4
, which is a sectional view of both the recording head
41
and ink container
42
, the ink container
42
comprises: an external shell with an air vent
422
and an ink outlet
421
; an absorbent member
423
stored in the shell; and a pressing member
307
placed in contact with the ink outlet
421
for guiding outward the ink within the ink container
42
. The recording head
41
is provided with an ink inlet
301
(ink supply tube), which is a part of an ink guiding path
302
for supplying ink to an ink ejecting portion
411
. The outward end of the ink inlet
301
(ink guiding path
302
) is provided with a filter
303
, the center portion from which protrudes slightly outward from the ink inlet
301
.
FIG. 3
is an enlarged sectional view of the outward end portion of the ink guiding path
302
, the ink outlet
421
, and their adjacencies. Referring to FIG.
3
(
c
), conventionally, the ink outlet
421
of the ink container is provided with the pressing member
307
, and the ink is supplied to the recording head through the contact between the filter
303
and pressing member
307
. Next, referring to FIG.
3
(
b
), generally, the filter
303
is located at the outermost end of the ink guiding path
302
, the periphery of the filter
303
being covered with resin, as disclosed in Japanese Laid-Open Patent Application 6-238910, to prevent the occurrences of such problems as the filter
303
becoming separated from the ink inlet
301
, and fiber ends exposed at the periphery of the filter damaging the pressing member. The filter
303
is fixed to the outermost end of the ink guiding path
302
by thermally bending inward the edge of the ink inlet
301
of the recording head, which is formed of a thermoplastic resin. When the filter is placed in a manner to directly press a highly elastic absorbent member as in the case of Japanese Laid-Open Patent Application 5-345425, there will be no problem. However, in the case of a structural arrangement in which the filter is placed in a manner to directly press the pressing member of an ink container, the following problem occurs. That is, if the thermoplastic resin portion of the ink inlet, covering the periphery of the filter, projects farther toward the pressing member than the filter, the resin portion comes into contact with the pressing member which is greater in diameter than the filter, thereby preventing the filter from coming into contact with the pressing member. Thus, in such a case, the filter is shaped so that the center portion of the filter spherically bulges outward to assure that the center portion of the filter comes into contact with the pressing member (FIG.
3
(
b
)). A conventional filter formed by weaving metallic fibers is flexible, but flat in its natural state. Thus, it is welded to the resin portion so that the center portion of the filter remains flexed outward of the liquid inlet. Since the filter is flexible, it deforms as it is pressed by the pressing member, preventing air from remaining (entering) between the filter and pressing member.
The filter grade should be selected according to the diameter of the orifices through which ink droplets are ejected. However, a conventional filter formed by weaving metallic fibers is not satisfactory in terms of foreign object removal performance. More specifically, in order to remove finer foreign objects, the metallic fibers must be made fine, but the finer the metallic fibers, the weaker the filter. In other words, it is difficult to make a filter which is strong and yet does not easily clog. Thus, in order to provide a filter which is strong and yet does not easily clog, it becomes necessary to replace the conventional filter material with a material that is stronger and yet is less likely to clog than the conventional filter material. Thus, a filter formed by sintered metallic fibers layered like the fibers in nonwoven fabric has come into use as a replacement for a conventional filter, due to its advantage that it is finer in mesh and its multilayer structure makes it less likely to clog. On the other hand, a sintered filter lacks flexibility, and therefore, it is difficult to make the center portion of a sintered filter permanently protrude outward of the ink inlet of a liquid ejection recording head when attaching the filter to the resinous portion of the ink inlet. Thus, a sintered filter must be shaped so that its center portion permanently protrudes in the direction corresponding to the outward direction of the ink inlet, prior to the attachment of the filter to the resinous portion of the ink inlet. As for the shape in which the center portion of a sintered filter protrudes, in the case of a sintered filter with a small diameter, for example, no more than approximately 5 mm, the center portion of the sintered filter will be in the form of a circular frustum, being flat on top, surrounded by the flat peripheral portion of the filter, in consideration of issues regarding the manufacture of the sintered filter, for example, the accuracy of the pressing process.
Further, in the case of an ink supplying member which uses capillary force to supply ink, the higher the speed at which ink must be supplied, the stronger the ink retaining force of the ink supplying member must be; and the stronger the ink retaining force of the ink supplying member must be, the stronger the capillary force the ink supply member generates must be. Conventionally, a pressing member formed by layering polypropylene fibers in the same manner as the fibers in felt are layered has been used as the aforementioned pressing member. In the case of this type of pressing member, however, the needle punch marks which were made while manufacturing this type of pressing member, and/or the density limit in the manufacturing process, made it difficult to increase the capillary force in this type of pressing member above a certain level. Thus, a pressing member formed by binding polypropylene fibers in parallel in such a manner that the fiber direction matches the ink flow direction has come into use as a replacement for a conventional pressing member, due to its advantage that it is higher in fiber density, therefore being capable of generating a stronger capillary force, and also, being capable of preventing the pressure loss from increasing.
However, the above-described filter formed by sintering is poor in flexibility compared to the woven filter; it is difficult to sinter a filter c
Hirosawa Toshiaki
Kanno Akifumi
Udagawa Kenta
Yoshinari Taiji
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