Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-11-04
2004-03-09
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06702420
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a liquid jetting apparatus having a head member capable of jetting a drop of liquid from a nozzle. In particular, this invention relates to a liquid jetting apparatus having a head member of jetting a plurality of drops of liquid from a nozzle while the head member is moved both forward and backward.
BACKGROUND OF THE INVENTION
In a ink-jetting recording apparatus such as an ink-jetting printer or an ink-jetting plotter (a kind of liquid jetting apparatus), a recording head (head member) can move in a main scanning direction, and a recording paper (a kind of medium onto which liquid is to be jetted) can move in a sub-scanning direction perpendicular to the main scanning direction. While the recording head moves in the main scanning direction, a drop of ink can be jetted from a nozzle of the recording head onto the recording paper. Thus, an image including a character or the like can be recorded on the recording paper. For example, the drop of ink can be jetted by causing a pressure chamber communicating with the nozzle to expand and/or contract.
The pressure chamber may be caused to expand and/or contract, for example by utilizing deformation of a piezoelectric vibrating member. In such a recording head, the piezoelectric vibrating member can be deformed based on a supplied driving-pulse in order to change a volume of the pressure chamber. When the volume of the pressure chamber is changed, a pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is jetted from the nozzle.
In such a recording apparatus, a driving signal consisting of a series of a plurality of driving-pulses is generated. On the other hand, printing data that define whether a drop of ink is jetted or not can be transmitted to the recording head. Then, based on the transmitted printing data, only necessary one or more driving-pulses are selected from the driving signal and supplied to the piezoelectric vibrating member. That is, whether a drop of ink is jetted from a nozzle is determined based on the printing data.
In order to conduct the recording operation to the recording paper faster, it is preferable that drops of ink are jetted from the nozzle of the recording head both while the recording head is moved forward in the main scanning direction and while the recording head is moved backward in the main scanning direction, to record an image including a character or the like on the recording paper. That is, preferably, after a recording operation for one line has been conducted during a forward movement of the recording head, the recording head is moved relatively to the recording paper in the sub-scanning direction by a width of line (including a gap between lines), and then a recording operation for the next line is conducted during a backward movement of the recording head. Such an ink-jetting recording apparatus, which can record while the recording head is moved both forward and backward, is called a double-direction type (Bi-D) of apparatus.
For such a double-direction type of ink-jetting recording apparatus, in order to enhance recording accuracy, it is preferable that a waveform of a driving signal for the forward movement of the recording head and a waveform of a driving signal for the backward movement of the recording head are separately generated. Generation of the waveforms of the driving signals is disclosed in detail in Japanese Patent Laid-Open Publication No. 2000-1001.
Herein, as shown in
FIGS. 21A
to
21
D, in the conventional driving signals for the forward movement of the recording head and for the backward movement of the recording head, a waiting time S from a timing signal for each image unit until a fall (or a rise) of each pulse-wave PW is fixed.
In the case, if the recording head is moved at a constant speed, there is no gap between a point (position) which a drop of ink jetted during a forward movement of the recording head reaches and a point which a drop of ink jetted during a backward movement of the recording head reaches. That is, no reaching-position gap (Bi-d gap) is generated.
In detail, as shown in
FIG. 21A
, if the speed of the recording head is constant at V
0
, the recording head passes through a plurality of predetermined passage-positions P
0
, P
1
, P
2
, . . . at respective times t
0
, t
1
, t
2
, . . . Herein, time gaps of t
1
−t
0
=&Dgr;t
0
, t
2
−t
1
=&Dgr;t
1
, . . . are always constant (see FIGS.
21
B and
21
C). Thus, the constant waiting time S is a necessary condition to prevent generation of the reaching-position gap (see FIGS.
21
C and
21
D).
However, if the recording head is moved at a variable speed, as shown in
FIGS. 22A
to
22
D, a reaching-position gap may be generated between a point which a drop of ink jetted during a forward movement of the recording head reaches and a point which a drop of ink jetted during a backward movement of the recording head reaches.
In detail, as shown in
FIG. 22A
, if the speed of the recording head is increased toward V
0
, the recording head passes through a plurality of predetermined passage-positions P
0
, P
1
, P
2
, . . . at respective times t
0
, t
1
, t
2
, . . . Herein, time gaps of t
1
−t
0
=&Dgr;t
0
, t
2
−t
1
=&Dgr;t
1
, . . . become shorter and then become constant (see FIGS.
22
B and
22
C). Thus, the constant waiting time S may generate a Bi-D gap, that is, jetted drops of ink may not be aligned in the sub-scanning direction (see FIGS.
22
C and
22
D).
SUMMARY OF THE INVENTION
The object of this invention is to solve the above problems, that is, to provide a liquid jetting apparatus such as an ink-jet recording apparatus that can suitably adjust positions which drops of liquid jetted from a nozzle reach, even when a forward and backward moving speed of the nozzle is changed.
In order to achieve the object, a liquid jetting apparatus includes: a head member having a nozzle; a pressure-changing unit for causing pressure of liquid in the nozzle to change in such a manner that the liquid is jetted from the nozzle; a reciprocating mechanism that can move the head member forward and backward at a variable speed in such a manner that the head member passes through a plurality of predetermined passage-positions; a forward-driving-signal generator that can generate a forward jetting-driving signal, based on a plurality of forward-timings respectively defined correspondingly to the plurality of predetermined passage-positions while the head member is moved forward; a forward-driving-pulse generator that can generate a forward driving pulse based on the forward jetting-driving signal; a backward-driving-signal generator that can generate a backward jetting-driving signal, based on a plurality of backward-timings respectively defined correspondingly to the plurality of predetermined passage-positions while the head member is moved backward; a backward-driving-pulse generator that can generate a backward driving pulse based on the backward jetting-driving signal; and a main controller that can cause the pressure-changing unit to operate based on the forward driving pulse while the head member is moved forward, and that can cause the pressure-changing unit to operate based on the backward driving pulse while the head member is moved backward; wherein a plurality of forward pulse-waiting-times are respectively defined correspondingly to the respective forward-timings, a plurality of backward pulse-waiting-times are respectively defined correspondingly to the respective backward-timings, the forward jetting-driving signal includes a plurality of forward pulse-waves that respectively rise up or fall down when the respective forward pulse-waiting-times have passed since the respective forward-timings, the backward jetting-driving signal includes a plurality of backward pulse-waves that respectively rise up or fall down when the respective backward pulse-waiting-times have passed since the respective backward-timings, and each forward pulse-wave and each backward pulse-wave have the same
Meier Stephen D.
Seiko Epson Corporation
Stewart, Jr. Charles
Sughrue & Mion, PLLC
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