Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-10-26
2003-04-08
Pham, Hai (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06543873
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to printers, and more particularly, although not exclusively, to improving the image quality of a print job.
BACKGROUND OF THE INVENTION
It is generally known that inkjet printers utilize at least one printhead possessing a plurality of nozzles through which ink drops are fired onto a medium, e.g., fabric, paper, vinyl etc., to create an image on the medium, e.g., plot, drawing, etc. According to one type of inkjet printer, ink is typically supplied substantially continuously over a plurality of resistors generally located beneath the openings of the nozzles. In use, certain of the resistors are activated, i.e., heated, to vaporize a portion of the ink on the resistors, thereby causing a portion of the ink to be fired through the respective nozzle openings. According to another type of inkjet printer, ink is typically supplied substantially continuously over a plurality of piezoelectric elements located beneath the openings of the nozzles. In this type of printer, certain of the piezoelectric elements are caused to deform at a relatively rapid rate, thereby causing ink positioned thereover to be fired through the respective nozzle openings to produce pixels.
To create an image on the print medium, the printer typically controls the nozzles to produce a pattern of pixels corresponding to the image. The nozzles are generally arranged on one or more printheads that travel back and forth across the surface of the print medium. In this regard,
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
. 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, typically from the right side
118
to the left side
116
of the printer
110
. In addition, as the carriage
100
travels along the Y-axis
103
, certain of the printheads
102
-
108
drop or fire ink onto a medium
130
through a plurality of nozzles (not shown).
Typically, the medium
130
travels in an X-axis direction
101
at certain times during the printing operation. 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.).
In performing printing operations with inkjet printers, it is generally known that the print quality and the throughput, i.e., amount of time required to print a plot, may be inversely related. That is, to increase throughput, the print quality is oftentimes sacrificed, or vice versa. To maintain a preferred level of print quality, servicing operations are typically performed on the printheads
102
-
108
. In this respect, although not shown in
FIG. 1
, inkjet printers typically possess a service station located (“spittoon”) to perform the above-described servicing operations on the printheads
102
-
108
.
There are generally two ways in which the nozzles of the printheads
102
-
108
may be “refreshed”, i.e., cleaned. The nozzles may be refreshed by firing ink drops onto the medium
130
, i.e., printing, or by spitting ink drops into the spittoon. Thus, those nozzles of the printheads
102
-
108
that actively drop ink onto the medium typically are not required to spit into the spittoon during various printing passes.
If it is preferred to increase throughput, the number of servicing operations performed on the printheads
102
-
108
may be reduced. In this respect, the length of time between the servicing operations may also be increased. One problem associated with increasing the length of time between servicing operations is that the properties of fired ink drops may deteriorate, thereby compromising the print quality. For example, ink in position to be fired from the nozzle may become dried and thus not fired through the nozzle. This effect is generally referred to as “decap” and typically occurs when a maximum amount of time a nozzle may be idle (i.e., not firing or spitting ink drops) before an ink drop may be ejected from that nozzle is exceeded. In addition, “slewing decap” generally refers to the maximum amount of time a nozzle may be idle during a pass across a medium. Moreover, because the nozzles are moving, the effects of “slewing decap” on the nozzles are typically worse than “decap”. As a consequence, slewing decap times are generally shorter than decap times.
To reduce the negative effects of decap, the spittoon typically performs servicing operations on the printheads as well as capping the nozzles when the printheads are idle for a certain period of time. For example, the printheads typically spit ink into the spittoon at various times during a printing operation to substantially prevent the occurrence of decap. Additionally, the spittoon may also include a mechanism for wiping the nozzles of the printheads at various times to generally attempt to wipe off ink dried in the nozzles. Although the performance of the above-stated servicing operations on the printheads has been found to relatively increase the life of the printheads as well as the quality of the printed image, one disadvantage of performing a relatively large number of servicing operations is that the throughput may become compromised.
A typical workflow utilized by the large format (i.e., 40 inches or more) inkjet (e.g., thermal, piezoelectric cell, etc.) printing industry follows. A print job is initiated. For example, a poster, is sent to the printer. Some startup time may pass (e.g., a few seconds or so) as the job is being processed through the pipeline and the printer is getting ready to print the job. During the startup time, the printer typically takes this opportunity to perform actions that may result in lowering the rate of defects. For example, the servicing protocols mentioned above. In addition, the printer may have performed servicing at startup i.e., when the printer was turned on. To continue, the job is printed as described above. The job length is defined typically by the length of the file, for example the size of the poster. Once the job has finished printing, the print medium is typically cut and the printer may perform one or more servicing actions prior to the next job. This particular series of events (i.e., workflow) is generally utilized by the large format inkjet printing industry.
In the textile printing industry, however, a number of differences may be noted. For instance, the print medium is relatively larger. In this regard, fabric mills typically produce fabric five meters wide and several hundred meters long. Each of two sides or edges of the fabric are termed “selvage”. Typically, the selvage is woven differently to reduce tearing and fraying of the material. The fabric is generally rolled to facilitate transport and handling. The roll is then transported to a textile printing mill.
A typical workflow utilized by the textile printing industry follows. The textile mill receives the roll and load it into a processing machine. Typically the machine unrolls the fabric, washes and bleaches the fabric. As processing continues, a tensioner is utilized to remove wrinkles. The tensioner grasp
Hewlett--Packard Company
Pham Hai
Stewart Jr. Charles W.
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