Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-02-06
2003-01-14
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06505922
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the design and fabrication of inkjet printheads, and in particular to printheads configured to uniformly translate the position of printed ink drops on a receiver without altering the position of the printhead with respect to the receiver.
BACKGROUND OF THE INVENTION
Traditionally, digitally controlled inkjet printing capability is accomplished by one of two technologies. The first technology, commonly referred to as “drop-on-demand”, ejects ink drops from nozzles formed in a printhead only when an ink drop is desired to impinge on a receiver. The second technology, commonly referred to as “continuous”, ejects ink drops from nozzles formed in a printhead continuously with ink drops being captured by a gutter when ink drops are not desired to impinge on a receiver.
Referring to
FIG. 1
, a printhead
120
, typically includes an approximately linear row of nozzles
122
which define printhead length
124
(measured in a direction along the nozzle row). Printhead
120
is scanned across a stationary receiver
126
in a fast scan direction
128
. After fast scan
128
is complete, receiver
126
is moved in a receiver motion direction
130
relative to printhead
120
. Typically, receiver motion
130
is orthogonal or substantially orthogonal to fast scan direction
128
and receiver
126
is moved in receiver motion
130
rather than displacing printhead
120
in a slow scan direction
132
. Printhead
120
is subsequently scanned again in fast scan direction
128
with nozzles
122
having been physically displaced with respect to receiver
126
by an incremental amount (shown schematically so as to be easily compared to printhead length
124
). The overall result is displacement of printhead
120
is in slow scan direction
132
. Typically, displacement of printhead
120
with respect to receiver
126
in slow scan direction
132
is a fraction of nozzle to nozzle spacing
134
. Typically, slow scan direction
132
is also orthogonal or substantially orthogonal to fast scan direction
128
. Alternatively, printhead
120
can be physically stepped in slow scan direction
132
in order to physically displace printhead
120
with respect to receiver
126
. Receiver
126
can also be moved in slow scan direction
132
in order to accomplish displacement of printhead
120
with respect to receiver
126
. In either situation, either printhead
120
or receiver
126
is moved. Typically, the above-described motions are controlled by a controller
134
. Many commercially available desktop printers (drop-on-demand printers, etc.) operate in this manner.
In continuous inkjet printers, receiver
126
is typically moved in fast scan direction
128
rather than printhead
120
because of the size and complexity of printhead
120
. In many cases, printhead length
124
is pagewide and extends across the entire width of receiver
126
with fast scan direction
128
of receiver
126
being perpendicular to printhead length
124
. This type of printhead and/or printer is commonly referred to as a “pagewidth” printhead/printer. Alternatively, printhead
120
can be scanned in fast scan direction
128
, then stepped in slow scan direction
132
before printhead
120
scanned again in fast scan direction
128
.
In some continuous printing applications, it is desirable to move printhead
120
in slow scan direction
132
in order to translate the pattern of printed ink drops (with respect to receiver
126
) produced by nozzles
122
. For example, in several conventional pagewidth printers, printhead
120
is translated or dithered a small distance from side to side in a direction parallel to its length (slow scan direction
132
). This motion can be used to compensate for irregularities in nozzle to nozzle spacing
134
of printhead
120
. Typical nozzle to nozzle spacing
134
is a multiple of the desired distance between printed dots. As such, printhead
120
can be displaced slightly along its length and fast scan
128
is repeated one or more times in order to print all desired dots. Typically, translated printed drop patterns are created by translating printhead
120
in slow scan direction
132
with respect to receiver
126
. However, receiver
126
can be translated or displaced in slow scan direction
132
while printhead
120
remains stationary in slow scan direction
132
.
Translation of the printhead in the slow scan direction is very precise. As such, commercially available mechanical devices that perform this task increase overall printer costs, are complex, and are prone to failure. Additionally, commercially available printheads often perform poorly when translated or dithered rapidly due to fluid acceleration along the length of the printhead. This is particularly true for pagewidth printheads because pagewidth printheads have extremely long fluid channels, typically distributed over the entire length of the printhead. Rapidly displacing the printhead intensifies the adverse affects of the fluid acceleration. As such, there is a need for an improved printhead translatable along its length (typically, in the slow scan direction relative to the receiver).
Additionally, it is advantageous to adjust the location of ink drop patterns printed on a receiver in the slow-scan direction in order to improve image quality. In this regard, displacing, dithering, or translating the printhead by an integral spacing relative to nozzle to nozzle spacing (the distance between nozzles) allows selected nozzles to print different data, thereby reducing image artifacts. The printhead motion (translation) needs to occur quickly in order to accomplish this. Typically, this motion is completed in a time much shorter in duration than the time required to scan in the fast scan direction. Again, currently available mechanical devices that accomplish this motion increase system cost and complexity. As such, there is a need for an improved printhead capable of adjusting the location of ink drop pattern printed on a receiver.
It is also advantageous to adjust the location of ink drop patterns printed on a receiver so as to slightly change the angle of the printhead relative to the fast scan direction in order to suppress image artifacts. This situation typically arises, for example, when the angle of the receiver changes while passing under the printhead. In many of these situations, changing the angle of the printhead relative to the fast scan direction needs to occur rapidly in order to prevent printed ink drops from misregistering (being printed on the wrong location) on the receiver. Again, currently available mechanical devices for moving the printhead at an angle relative to the fast scan direction add expense and complexity. Additionally, these devices can interfere with printhead performance during printhead motion in the fast scan direction due to the additional weight of the devices. As such, there is a need for an improved printhead capable of changing the angle of drops printed from a row of nozzles.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved printhead translatable along its length.
Another object of the present invention is to provide an improved printhead rapidly translatable along its length that accurately and rapidly produces displaced printed drops in a direction parallel to the length of the printhead without interfering with the performance of the printhead.
Another object of the present invention is to provide an improved printhead capable of rapidly rotating the pattern of printed ink drops through an angle with respect to the receiver.
Yet another object of the present invention is to produce a displaced pattern of ink drops printed on a receiver without having to displace the receiver or the printhead.
Yet another object of the present invention is to provide an improved printhead having reduced cost and increased reliability.
According to a feature of the present invention, a continuous ink jet printing apparatus includes a nozzle array with portions of the nozzle array defining a leng
Hawkins Gilbert A.
Jeanmaire David L.
Eastman Kodak Company
Nguyen Judy
Zimmerli William R.
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