Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-06-03
2003-07-22
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
C347S043000, C347S041000
Reexamination Certificate
active
06595614
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink-jet printer. More particularly, the present invention relates to an ink-jet printer which comprises a head in which plural ink injection nozzles (simply referred to as nozzles hereinafter) are arranged at substantially equal intervals in the vertical scanning direction and which performs small line feeds and large line feeds.
BACKGROUND OF THE INVENTION
An ink-jet printer is a printer that sprays tiny droplets of ink, from a nozzle, onto a medium such as paper and creates an image by the attached droplets of ink. In the case of a monochrome printer, only one color of ink is used but, in the case of a color printer, four or more kinds of nozzles that spray four or more colors such as cyan, magenta, yellow, and black are used.
FIG. 1
is a cross sectional view of an ink-jet printer. In response to the outset of printing, a send roller
11
starts to rotate and a medium (sheet of paper) stacked in a paper cassette
10
is sent out along a guide
12
. The sent-out sheet of paper is sent to the part under a head
20
under a roller
13
and interposed between paper feed rollers
14
and
15
. By driving the paper feed rollers
14
and
15
rotationally, it is possible to feed the sheet of paper by a desired amount. The head
20
comprises a nozzle
21
and ink is sprayed from the nozzle
21
by driving an actuator that is not shown. The head
20
can move along a guide
22
in the direction perpendicular to that in which the paper moves and, in general, the movement of the head is called the main scanning, its direction, the main scanning direction, and the direction perpendicular thereto, that is, the moving direction of the sheet of paper is called the vertical scanning direction. By spraying ink at the positions of dots to be printed during a single main scan, the dots of a row corresponding to a nozzle are printed. After printing by the single main scan, the sheet of paper is fed by the amount of a row and the dots of the row are printed again, then the dots of the next row are printed. By repeating the above-mentioned action, printing on the entire surface of the sheet of paper is achieved. The sheet of paper onto which printing has been completed is ejected to a tray
16
. The part denoted by reference number
3
is a member to prevent the tip of the nozzle
21
from drying and clogging and covers the tip of the nozzle
21
when it is not printing.
If printing of the dots of a row is performed by only one nozzle during a single main scan, it is necessary to perform the main scanning many times in order to print a sheet of paper, bringing about a problem that a long time is required for printing, that is, that the printing speed is slow. Therefore, plural nozzles are arranged in the vertical scanning direction and printing speed is improved by printing plural dot rows simultaneously during the single main scan.
FIG. 2
is a diagram that shows an example of an arrangement of the nozzles on the head of a color ink-jet printer.
FIG. 2
(
1
) shows an example in which each color nozzle is arranged in a column in the vertical scanning direction and a black ink head
31
K, a cyan ink head
31
C, a magenta ink head
31
M, and an yellow ink head
31
Y are arranged shifted to the right one by one in the main scanning direction. On each head, plural (m) nozzles
32
-
1
to
32
-m are arranged at intervals of a whole number multiple of the dot pitch. In order to spray ink of each color to the same dot, ink is sprayed from each color head delayed by the time determined by the distance between heads in the main scanning direction and the speed of the main scanning.
It is necessary to provide a mechanism, which is composed of materials such as piezo elements, to spray ink from each nozzle, and as a result a space of a certain extent is required. Therefore, it is impossible to arrange nozzles adjacently so as to correspond to each dot, but the nozzles are arranged in the vertical scanning direction at fixed intervals. Printing actions in the case where nozzles are arranged as described above are described later.
FIG. 2
(
2
) shows an arrangement in which plural columns of nozzles arranged at fixed intervals in the vertical scanning direction are arranged so that the intervals between arranged nozzles in the vertical scanning direction are substantially reduced. Similarly to
FIG. 2
(
1
), heads of four colors, black, cyan, magenta, and yellow are provided and two columns of nozzles
34
-
1
and
34
-
2
are provided. The two columns of nozzles are arranged in the vertical scanning direction, being shifted from each other by half the nozzle interval, and the nozzles of the two columns are arranged at equal intervals in the vertical scanning direction, when viewed from the main scanning direction. The interval is half the nozzle interval of one column of nozzles and this substantial interval is referred to as the arrangement interval in the vertical scanning direction. In order to spray ink onto the same dot column, ink is sprayed from the nozzle of each column, being delayed by the difference in time determined by the deviation in the main scanning direction and the main scanning speed. In this way, the same printing is achieved as that when nozzles are arranged at half the intervals of those of nozzles in each column. If the number of columns of nozzles is increased, the substantial arrangement interval can be reduced by the corresponding amount, and if, for example, six columns of nozzles, the arrangement pitch of which is six-dot, are provided, it is possible to print the adjacent dots simultaneously by a single main scan. The arrangement, however, in which nozzles are arranged densely in the vertical scanning direction, is difficult to realize, from the standpoints of the head size and cost. The present invention focuses on a head on which nozzles are arranged at intervals larger than a single dot in the vertical scanning direction. Although the head of a color ink-jet printer is shown in
FIG. 2
, the present invention can be applied to both a monochrome ink-jet printer and a color ink-jet printer. For simplicity, description is made below with reference to a monochrome ink-jet printer as an example, but the present invention is not restricted to this case.
FIG. 3
shows a head on which m nozzles
36
-
1
to
36
-m are arranged at fixed intervals (four-dot pitch) in the vertical scanning direction, and indicates the relative movement during printing using this head between the head and the medium (paper) in the vertical scanning direction. Here, a case where a belt-shaped vertical line is printed, is described. The head performs the main scanning at the position denoted by
35
a
and dots in m rows are printed by the m nozzles. In this way, m horizontal lines with one-dot width are printed at a four-dot pitch and a space corresponding to three-dot width is left between two adjacent horizontal lines. Next, the head moves in the vertical scanning direction relative to the medium to the position denoted by
35
b
. This movement is called the small line feed. The main scanning is performed at the position and m dot rows are printed. The m dot rows printed at this time are downwardly adjacent to the m dot rows previously printed, and they form m horizontal lines with two-dot widths. This time, a space corresponding to two-dot width is left between two adjacent horizontal lines. Similarly, the head is moved to the position denoted by
35
c
by the small line feed, performs the main scanning, and m dot rows are printed. By this, they form m horizontal lines with three-dot width and a space corresponding to a one-dot width is left between two adjacent horizontal lines. Furthermore, the head is moved to the position denoted by
35
d
by the small line feed, performs the main scanning, and m dot rows are printed. In this way, a rectangle with 4×m dot width in the vertical scanning direction is printed. Then, the head is moved to the position denoted by
35
e
. This is called the large line feed. The amount of movement of the
Morikawa Yukio
Moroo Jun
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
Nguyen Lamson
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