Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-15
2003-03-11
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06530642
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of cleaning a liquid nozzle-formed face of a print unit that performs printing on a surface of a recording medium, to a cleaning device for an ink jet printing apparatus having a plurality of cleaning members using this cleaning method, and to an ink jet printing apparatus having this cleaning device.
2. Description of the Prior Art
Conventional ink jet printing apparatus are provided with a cleaning device for cleaning the surface of a print head formed with a plurality of ink nozzles because contamination of the nozzle-formed face will lead to a failure of the print head to eject ink. The cleaning device includes a wiper blade as a cleaning member. The wiper blade is made, for example, of an elastic material and is moved relative to the nozzle-formed face of the print head to bring its wipe portion into a sliding contact with the nozzle-formed face to remove ink adhering to it.
During this process, a cleaning performance (wiping performance) of the wiper blade depends on an ink adhesion state of the nozzle-formed face of the print head and a contact width over which the wipe portion of the wiper blade contacts the nozzle-formed face.
The result of verification as to the effect which the contact width between the wipe portion of the wiper blade and the nozzle-formed face has on the wiping performance will be described in the following.
FIG. 20
shows a state in which the end of the wiper blade
1004
is brought into contact with one surface of a transparent body
1002
, such as a glass plate, of a predetermined width over a predetermined contact width Lc and is slid in a direction of arrow at a predetermined speed, for example 150 mm/s. The wiper blade
1004
is made of an elastic material (with Asca C scale hardness of 75) and is 10 mm in overall length and 0.7 mm in thickness.
In performing the verification, the contact width over which the wipe portion of the wiper blade
1004
contacts the nozzle-formed face is classified largely into three levels as shown in FIG.
21
.
A first level of the contact width (overlapping length) Lc represents a state in which a contact width L
1
is relatively small at about 0.3-0.7 mm when viewed directly from above, with only a widthwise edge of the end of the wipe portion in contact, as shown in
FIG. 21A. A
second level represents a state in which a contact width L
2
is slightly larger at about 0.8-1.2 mm, with the widthwise edge as well as a widthwise area of the front surface of the wipe portion near its end in contact, as shown in
FIG. 21B. A
third level represents a state in which a thicker widthwise area of the front surface of the wipe portion near its end than in the second level contacts the transparent body over a relatively large contact width L
3
of about 1.3-1.7 mm as shown in FIG.
21
C.
The verification is performed by contacting the end of the wipe portion of one wiper blade
1004
against the nozzle-formed face of the print head over a predetermined contact width and sliding it in the direction of arrow at a predetermined speed of, for example, 150 mm/s. In this verification, the amount of ink adhering to the nozzle-formed face of the print head is set in five levels. For each level of ink adhesion to the nozzle-formed face, the contact width is changed in three levels.
The five levels set for the amount of adhering ink are: an initial ink adhesion state E in which ink adheres uniformly to the entire area of the nozzle-formed face of the print head with no apparent effect of the liquid repelling ability of the nozzle-formed face; an initial ink adhesion state D in which a significant number of large and small grains of ink adhere to the nozzle-formed face, like a state found when a relatively high density (50% or higher) recording has been performed; an initial ink adhesion state C in which ink grains are uniformly scattered on the nozzle-formed face, like a state found when a relatively intermediate density (10-50%) recording has been performed; an initial ink adhesion state B in which ink grains are sparsely present on the nozzle-formed face, like a state found when a relatively low density (less than 10%) recording has been carried out; and a state A in which no ink is present on the nozzle-formed face, like a state immediately after the print head has been replaced.
The result of this, verification is tabulated in FIG.
27
. In
FIG. 27
, a solid black circular mark “&Circlesolid;” indicates that the surface wiped by the wiper blade
1004
is in good condition; a white circular mark “◯” indicates that a small amount of ink remains on the surface at positions spaced from the nozzles, with no adverse effect on the ink ejection performance; a triangular mark “&Dgr;” indicates that a small amount of ink remains near the nozzles leaving the possibility of affecting the ink ejection performance; a cross mark “x” indicates that a large amount of ink remains near the nozzles, giving rise to the possibility of an ink ejection failure; and a bar mark “-” indicates that there is no remaining ink.
As is evident from the table of
FIG. 27
, keeping the contact width (overlapping length) at the second level or an intermediate length of 0.8-1.2 mm produces good wiping results for the initial ink adhesion levels B, C, D. As to the initial ink adhesion level E in which the ink cannot be repelled at all by the liquid repelling ability of the nozzle-formed face and remains over the entire area of the nozzle-formed face, however, there is a limit to what the single wiper blade can do in wiping off the adhering ink.
Further, as shown in
FIG. 22A
, when the nozzle-formed face
1008
s
of the print head
1008
has been wiped a plurality of times by the wiper blade
1010
supported on a support mount
1012
, the wiping action is likely to be started with contaminating ink droplets
1006
adhering to the wipe portion of the wiper blade
1010
.
In that case, when the wiping is performed by the wiper blade
1010
with the contact width set to a relatively large amount, the dirty ink droplets
1006
are rubbed against the nozzle-formed face
1008
s
by the wiper blade
1010
, as shown in FIG.
22
B. After the wiping operation, the dirty ink droplets
1006
adhere to the entire area of the wipe portion of the wiper blade
1010
, as shown in FIG.
22
C.
Hence, the nozzle-formed face
1008
s
is likely to be smeared with the dirty ink droplets
1006
.
FIG. 23
shows the wipe portion (engagement surface) of the wiper blade
1016
wiping the nozzle-formed face
1014
s
of the print head
1014
having rows of nozzles
1018
X,
1018
Y and
1018
Z in such a manner that the wipe portion has a predetermined contact width. The nozzle rows
1018
X,
1018
Y and
1018
Z are arranged parallel to each other at predetermined intervals in the scan direction of the print head
1014
, i.e., in the direction of arrow in FIG.
23
. The print head
1014
is moved toward the scan direction indicated by the arrow of
FIG. 23
relative to the wipe portion of the fixed wiper blade
1016
. In
FIGS. 24 and 25
described later, ink already adhering to the nozzle-formed face
1014
s
is not shown.
When the wipe portion (engagement surface) of the wiper blade
1016
, after passing the nozzle row
1018
Z in the nozzle-formed face
1014
s
while wiping off the adhering ink as shown in
FIG. 24A
, reaches the nozzle row
1018
Y as shown in
FIGS. 24B and 25A
, a part (meniscus ME) of the ink
1020
in the nozzle row
1018
Y is drawn out in the direction of arrow as shown in
FIG. 25B
by a capillary attraction generated in a minute clearance CL between the end face of the wiper blade
1016
and the nozzle row
1018
Y in the nozzle-formed face
1014
s.
Then, the wipe portion (engagement surface) of the wiper blade
1016
moves past the nozzle row
1018
Y in the nozzle-formed face
1014
s
and advances further toward the direction of arrow, wiping the adhering ink, as shown in
FIGS. 24C and 25C
. The ink
1020
is attracted by the capillary attraction to both of the front
Edamura Tetsuya
Fujita Miyuki
Ishikawa Hisashi
Kawatoko Norihiro
Konno Yuji
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Pham Hai
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