Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-07-16
2003-05-20
Nguyen, Lamson (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S037000, C400S627000
Reexamination Certificate
active
06565171
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to inkjet printers. More specifically, the invention relates to a technique for substantially reducing vertical banding from printing operations performed by inkjet printers that utilize vacuum fans.
BACKGROUND OF THE INVENTION
FIG. 1
illustrates a conventional large format inkjet printer
110
having a pair of legs
114
, left and right sides
116
,
118
, and a cover
122
. This example will be used to illustrate some of the problems associated with known large format inkjet printers. As illustrated in
FIG. 1
, the printer
110
includes a carriage
100
supporting a plurality of printheads
102
-
108
. The carriage
100
is coupled to a slide rod
124
with a coupling
125
. As is generally known to those of ordinary skill in the art, during a printing operation, the carriage
100
travels along the slide rod
124
generally in a Y-axis direction
103
to make a printing pass. In addition, as the carriage
100
travels along the Y-axis
103
, certain of the printheads
102
-
108
drop ink onto a medium
130
, e.g., paper, through a plurality of nozzles (not shown). At certain times during the printing operation, the medium
130
typically travels generally in a X-axis direction
101
. By virtue of performing a plurality of printing passes over the medium
130
by the carriage
100
in the above-described manner, an image, e.g, plot, text, and the like, may be printed onto the medium.
Also illustrated in
FIG. 1
is a printer control panel
120
located on a right side
118
of the large format inkjet printer
110
. The printer control panel
120
typically functions as an interface between a user and the printer
110
to enable certain printer operations to be set (e.g., medium advance, printmode, etc.). In addition to housing the printer control panel
120
, the right side
118
of the printer
110
typically also houses printer components for performing printing operations (e.g., printer electronics, a service station for servicing operations on the printheads
102
-
108
, etc.).
During a printing operation, the accuracy of ink drop placement onto the medium
130
may be relatively compromised by virtue of a plurality of factors. For example, small inaccuracies due to uncontrolled movements, oscillations, etc., may cause faults in the printing output to become visible. In this respect, the printing quality may be adversely affected by operation of electromechanical components, e.g., vacuum fans, coupled to the printers. For example, operation of these types of electromechanical components may cause the printers to suffer from some of the above-stated inaccuracies. That is, during the operation of these types of electromechanical components, the electronic components may have a tendency to vibrate at certain frequencies, thus causing other components, e.g., printheads
102
-
108
, of the printers to undergo uncontrolled movements at a periodic rate. One result of the uncontrolled movements at a periodic rate is that vertical bands may be created in the printed image, e.g., plot, text, and the like.
In order to overcome some of the problems associated with misalignment of fired ink drops during printing operations, many inkjet printers have employed what is known as a multi-pass print mode. In a multi-pass print mode, instead of performing a single pass over a print swath, two or more passes are made with different nozzles to fire ink drops during each pass. In this respect, in a four pass print mode, for example, only one of four ink droplets may be missing or misdirected resulting in a much less catastrophic result. While the multi-pass printing technique has improved image quality for those situations in which failed nozzles are present, this technique has been relatively unsuccessful in removing vertical bands resulting from vibrations caused by operation of the above-described electromechanical components. In one respect, the source of vertical banding may not be successfully randomized with the increased number of passes. That is, the vibrations that are coupled to the carriage
100
may typically result in dot placement errors (DPE) of the same spatial frequency. Thus, the DPE have a tendency to accumulate when a multi-pass print mode is utilized, resulting in the formation of vertical bands.
Referring now to
FIG. 2
, which is an enlarged sectional view of the printer
110
illustrated in
FIG. 1
, with the cover
122
removed, an example of an electromechanical component that may cause vertical banding is shown. As shown in
FIG. 2
, a space is formed between the left and right sides
116
,
118
of the printer
110
defining an area in which the medium (not shown) may be printed upon. Generally extending along the print area is a serpentine-shaped opening
126
for applying vacuum pressure on a lower surface of the medium (not shown). In this respect, air is drawn in through the serpentine opening
126
to generally maintain the position of the medium in the print area.
Referring now to
FIG. 3
, which is a sectional view of the printer
110
generally below the print area, a vacuum fan
140
is illustrated. As stated hereinabove, the vacuum fan
140
is an example of an electromechanical component whose operation may cause the print quality to be adversely affected by its operation. As illustrated in
FIG. 3
, the vacuum fan
140
typically operates to draw air from the serpentine-shaped opening
126
and through an underside of the printer
110
. When the vacuum fan
140
is activated and is in operation, the vacuum fan typically rotates at a certain frequency, depending upon the amount of voltage supplied to the vacuum fan.
At least by virtue of the direct coupling between the vacuum fan
140
and the printer
110
, the rotation of the vacuum fan causes the printer to vibrate at a certain degree corresponding to the frequency of rotation of the vacuum fan. One result of the vibration is that the printheads
102
-
108
may undergo uncontrolled movements at certain times during a printing operation. Typically, the uncontrolled movements occur at a periodic rate, often due to the periodic nature of the vibrations, oftentimes resulting in the uncontrolled movements occurring at the same or substantially similar locations along each printing pass, thus resulting in the formation of vertical bands.
One solution to the above-stated problem of vertical band formation has been to attempt to substantially mechanically isolate the vacuum fan
140
from the printer
110
and thus attempt to prevent the vibrations caused in the operation of the vacuum fan from affecting the other components of the printer, namely the operation of the printheads
102
-
108
. However, even relatively substantial mechanical isolation of the vacuum fan
140
from the printer
110
has been found to be relatively insufficient in preventing the translation of the vibrations to other printer components. In addition, it has been found that the attempt to substantially mechanically isolate the vacuum fan
140
from the printer
110
typically increases the costs in fabricating the printer by relatively large amounts. Thus, even substantial mechanical isolation of the vacuum fan
140
from the printer
110
has not proven to be a substantially viable solution to some of the vertical band formation problems that may occur during printing operations.
SUMMARY OF THE INVENTION
According to one aspect, the present invention pertains to a method for reducing vertical banding in a printing device having a printhead for printing onto a medium and a voltage receiving component coupled to the printing device, in which, operation of the voltage receiving component may cause the voltage receiving component to vibrate at a frequency of oscillation that is configured to vary according to the degree of voltage supplied to the voltage receiving component. In the method, a first voltage is supplied to the voltage receiving component and a printing pass is performed over the medium. In addition, the first voltage supplied to the voltage receiving component is
Chanussot Fabien
Gil Miquel Antoni
Soto Jesus
Hewlett--Packard Company
Mouttet Blaise
Nguyen Lamson
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