Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-10-03
2003-06-10
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S035000
Reexamination Certificate
active
06575554
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording apparatus for recording an image by ejecting ink onto a recording medium. More particularly, the present invention relates to an ink jet recording apparatus for use in information processing equipment such as printers, copying machines, computers, and word processors.
2. Description of the Related Art
As one of conventional recording apparatuses, an ink jet recording apparatus is known in which a recording medium is intermittently fed in a recording section, and each time the feed is interrupted, ink droplets are ejected from a recording head over a certain width in a direction perpendicular to the feed direction, thereby recording an image.
In an ink jet recording apparatus, unless the spacing between a nozzle surface of a recording head, which ejects ink in a recording section, and a recording medium is maintained to be very small with high accuracy, there occur a deflection of an image due to an arrival failure of ejected ink droplets, and a smear due to contact between the recording head and the recording medium.
In some of ink jet recording apparatuses, therefore, a carriage holding a recording head is scanned with high accuracy using a guide shaft of good straightness, and a recording medium is attracted onto a flat platen under a vacuum sucking action. Generally, in the apparatus using such a sucking platen, a vacuum pump, a fan or the like is employed as a negative pressure generating source, and air in an enclosed space below the platen is evacuated to the outside to create a negative pressure in the space.
Recently, to meet a demand for recording an image in the frameless form without surrounding margins as with a borderless photograph, there has been proposed an apparatus in which ink is ejected over a range greater than the width of a recording medium to form a frameless image.
FIG. 9
is a perspective view of a platen and thereabout of such a conventional recording apparatus. Referring to
FIG. 9
, a recording medium
201
is supplied to a recording section in the apparatus from the direction of arrow K. A feed roller
202
is able to grip the recording medium
201
in cooperation with pinch rollers
203
,
204
and
205
, and to intermittently feed the recording medium
201
with high accuracy through coupling to a driving system (not shown) that rotates the feed roller.
A platen
206
is arranged such that its guide surface
206
a
supports thereon the recording medium
201
fed to the platen
206
by the feed roller
202
in a surface-to-surface contact relation. A plurality of openings
210
are formed in the guide surface
206
a
and communicated with a space formed within the platen
206
via air passages. When the space formed in the platen
206
below the guide surface
206
a
is evacuated to create a negative pressure by a vacuum pump or a fan, the recording medium
201
is attracted onto the guide surface
206
a
of the platen
206
through the openings
210
under a vacuum sucking action. Thus, the recording medium
201
can maintain a certain level of planeness.
A guide shaft
231
is arranged such that its axis extends in a direction, perpendicular to the feed direction of the recording medium
201
and parallel to the guide surface
206
a
of the platen
206
.
A carriage
232
is fitted over the guide shaft
231
and coupled to a linearly moving means (not shown) for movement in directions of arrows L and L′, i.e., in the main scan direction. An ink jet recording head is provided in the carriage
232
and has an ink ejection surface positioned to face the guide surface
206
a
of the platen
206
. During the movement of the recording head in the main scan direction, the spacing between the ink ejection surface and the recording medium
201
is maintained with high accuracy as long as the recording medium
201
is attracted onto the platen
206
to take a satisfactory flat posture.
The carriage
232
receives an electrical signal from a main control unit via a cable (not shown) and transmits the received signal to the recording head for ejecting ink. In accordance with the ejection signal received during the movement in the main scan direction, the recording head forms a long strip of image on the recording medium
201
lying over the platen
206
with a width corresponding to a row of ejection nozzles provided in the recording head. By repeating the above recording step the predetermined number of times whenever the recording medium
201
is intermittently fed by the feed roller
202
, an image of one page can be formed on the recording medium
201
.
The plurality of circular openings
210
formed in the guide surface
206
a
of the platen
206
are arrayed at an appropriate pitch so that the recording medium
201
is stably attracted onto the platen
206
through the plurality of openings
210
under vacuum suction. Further, ink recovery ports
211
,
212
for frameless recording are formed in the platen
206
at positions respectively corresponding to both ends
201
a,
201
b
of the recording medium
201
in the width direction thereof. Ink ejected outside the width of the recording medium
201
is recovered through the ink recovery ports
211
,
212
to prevent the ink from directly depositing on the guide surface
206
a
of the platen
206
.
FIG. 10
is a sectional view for explaining a situation in which the recording head ejects ink near the widthwise end
201
a
of the recording medium
201
in the frameless recording. Because the ends
201
a
of the recording medium
201
projects like a pent roof, there occurs an air eddy as indicated by one-dot-chain lines.
The conventional recording apparatus described above, therefore, has the following problems. The occurrence of an air eddy causes ink to scatter in the form of mists in addition to main ink droplets ejected from the recording head. The scattered mists may deposit on the backside of the recording medium and give rise to a backside smear.
Also, such ink mists move in a floating condition with the movement of the scanned carriage. When the recording medium
201
sometimes rises, even though slightly, away from the platen
206
, the ink mists are attracted to the left, as viewed in
FIG. 10
, by sucking forces acting through the suction openings
210
and deposit on the platen surface adjacent to the ink recovery port
211
. Then, the deposited ink mists adhere to the backside of the recording medium and also gives rise to a backside smear even slightly.
Further, when a leading end of the recording medium is positioned above the ink recovery port at the initial point of recording operation of one image, ink mists occur at the same time as ink ejection from the recording head and go around the leading end of the recording medium, thereby disturbing air streams. That tendency increases and intensifies turbulence as the recording medium is fed with the progress of recording and covers the ink recovery port at a greater rate. As a result, the ink mists may deposit on the backside of the leading end of the recording medium and give rise to a backside smear at the leading end of the recording medium.
Moreover, the recording head performs preliminary ejection for ejecting ink, which resides in nozzles and has an increased viscosity, before starting to eject the ink onto the recording medium. The ink is ejected in the preliminary ejection toward an ink receiver having the same structure as the ink recovery port. Upon the preliminary ejection, an air eddy occurs around an ejected ink stream due to air resistance and reaction caused within the ink receiver. This leads to a possibility that the ink may scatter to the surroundings of the ink receiver and give rise to a smear.
In addition, the ink mists and the ejected ink tend to deposit at corners of wall surfaces of both the ink recovery port and the ink receiver due to a capillary phenomenon, and gradually grow with the repeated recording operation to such an extent as impeding air streams in the ink recovery port and the ink receiver.
Barlow John
Do An H.
LandOfFree
Ink jet recording apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet recording apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet recording apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3137943