Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-11-05
2004-07-13
Meier, Stephen D. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S036000, C347S104000
Reexamination Certificate
active
06761430
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an inkjet printing apparatus and a preliminary discharge control method.
BACKGROUND OF THE INVENTION
An inkjet printer forms an image by discharging an ink droplet from a discharge orifice formed in a printhead and sticking the discharged ink droplet onto a printing sheet.
A printhead usually has a plurality of discharge orifices. If a discharge orifice not frequently used is present in these discharge orifices during printing, the ink viscosity in this discharge orifice rises owing to water evaporation to clog this discharge orifice. To avoid this phenomenon, ink droplets corresponding to a predetermined number of dots are discharged, at predetermined time intervals or in accordance with the calculated use ratios of the ink discharge orifices, while printing is executed, into an ink receptor (to be referred to as a preliminary discharge receptor) formed outside the scanning region of the printhead, thereby holding the state of each discharge orifice and its vicinity constant. This operation is called a preliminary discharge operation.
FIG. 7
is a perspective view showing an outline of the arrangement of a conventional inkjet printer.
Referring to
FIG. 7
, reference numeral
101
denotes a printing sheet;
102
, an automatic sheet feeding mechanism which feeds stacked printing sheets one by one into the printer and, as printing progresses, discharges each printing sheet forward (in the direction of an arrow);
103
, a carriage; and
104
, an ink cartridge containing a printhead which is so mounted as to discharge ink downward (toward the printing sheet).
The carriage
103
on which the ink cartridge
104
is mounted moves back and forth parallel to the printing sheet in a direction perpendicular to the conveyance direction of the printing sheet. An image is formed by discharging ink stored in the ink cartridge
104
toward the printing sheet.
Reference numeral
105
denotes a carriage motor; and
106
, a driving belt. The carriage
103
is interlocked with the carriage motor
105
by the driving belt
106
. When the carriage motor
105
is driven forward and backward, the carriage
103
moves forward and backward. Guide shafts
107
and
108
for mounting the carriage
103
support the forward and backward movements of the carriage
103
mounting the ink cartridge
104
.
Reference numerals
109
and
110
denote preliminary discharge receptors. In a preliminary discharge operation, the carriage
103
moves to a position above the preliminary discharge receptor
109
or
110
, and the printhead discharges ink droplets corresponding to a predetermined number of dots.
In this conventional inkjet printer, as can be seen from
FIG. 7
, a preliminary discharge receptor is generally formed on one or both sides of the scanning region of the printhead. When a preliminary discharge operation is to be executed, the printhead is moved from the printing end position to the position above the preliminary discharge receptor.
FIG. 8
is a schematic view showing the control of a printing operation and a preliminary discharge operation in this conventional inkjet printer.
As shown in
FIG. 8
, when an image such as “A . . . A” is to be printed on the printing sheet
101
, the carriage
103
mounting the printhead explained in
FIG. 7
scans within the range of a line
301
from a point x to a point y. This line
301
is made up of a printing region in which an image is formed by discharging ink onto the printing sheet, and acceleration (deceleration) regions a and b. To form an image in the printing region, the carriage
103
must be driven at a constant speed. When the carriage
103
is at rest at a point
302
, this carriage
103
is accelerated in the region a to move at the constant speed from a point
303
. Also, to stop the carriage
103
, which has moved at the constant speed to a point
304
, at a point
305
, this carriage
103
is decelerated in the region b.
When the image is to be printed by moving the carriage
103
in the opposite direction from the point y to the point x, the region b is an acceleration region, and the region a is a deceleration region. Therefore, printing region+region a+region b is the carriage moving range corresponding to a printing operation of one scan.
On the other hand, when a preliminary discharge operation is to be executed, the carriage
103
is moved to the position above the preliminary discharge receptor
109
or
110
to discharge ink. That is, when preliminary discharge is to be performed for the preliminary discharge receptor
109
, the carriage
103
is moved to a point
307
. A region d indicates a moving region from the carriage stop position to the preliminary discharge receptor
109
. When preliminary discharge is to be performed for the preliminary discharge receptor
110
, the carriage
103
is moved to a point
306
. A region c indicates a moving region from the carriage stop position to the preliminary discharge receptor
110
.
In the above prior art, however, if the width of the printing sheet is smaller than the maximum width of the scanning region, the actual scanning region of the printhead narrows in accordance with the width of the printing sheet. This increases the moving distance from the end of the scanning region to the preliminary discharge receptor when a preliminary discharge operation is to be performed. This undesirably prolongs the printing execution time.
FIG. 9
is a schematic view showing the control of a printing operation and a preliminary discharge operation of the conventional inkjet printer, when the width of a printing sheet is much smaller than the scan enable region. As is apparent from the comparison of
FIGS. 8 and 9
, the width of a printing sheet
400
is much smaller than the scan enable region shown in FIG.
8
.
When an image such as “A . . . A” is to be printed on this printing sheet
400
, the scanning range of the carriage
103
mounting the printhead explained in
FIG. 7
is the range indicated by a line
401
from a point x′ to a point y′. This line
401
is made up of a printing region in which an image is formed by discharging ink onto the printing sheet, and acceleration (deceleration) regions a′ and b′. To form an image in the printing region, the carriage
103
must be moved at a constant speed. When the carriage
103
is at rest at a point
402
, this carriage
103
is accelerated in the region a′ to move at the constant speed from a point
403
. Also, to stop the carriage
103
, which has moved at the constant speed to a point
404
, at a point
405
, this carriage
103
is decelerated in the region b′.
When the image is to be printed by moving the carriage
103
in the opposite direction from the point y′ to the point x′, the region b′ is an acceleration region, and the region a′ is a deceleration region. Therefore, printing region+region a′+region b′ is the carriage moving range corresponding to a printing operation of one scan.
When a preliminary discharge operation is to be executed, the carriage
103
is moved to the position above the preliminary discharge receptor
109
or
110
to discharge ink. That is, when preliminary discharge is to be performed for the preliminary discharge receptor
109
, the carriage
103
is moved to a point
407
. A region d′ indicates a moving region from the carriage stop position to the preliminary discharge receptor
109
. When preliminary discharge is to be performed for the preliminary discharge receptor
110
, the carriage
103
is moved to a point
406
. A region c′ indicates a moving region from the carriage stop position to the preliminary discharge receptor
110
.
As can be seen by comparing
FIGS. 8 and 9
, the width of the printing region decreases because the width of the printing sheet decreases. However, since the position of the preliminary discharge receptor
109
remains unchanged, the region d′ shown in
FIG. 9
which is the moving region, from the carriage stop position to
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Meier Stephen D.
Tran Ly T
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