Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-08-21
2003-04-29
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06554392
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to inkjet printers. More specifically, the present invention relates, to a technique for managing the spitting of printhead nozzles in an auxiliary spittoon to maximize print quality or throughput based upon selected preferences.
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
. 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 ink onto a medium
130
, e.g., paper, 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
18
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 (“main spittoon”) to perform the above-described servicing operations on the printheads
102
-
108
. Additionally, although not shown in
FIG. 1
, large format inkjet printers have also been known to possess a second service station (“auxiliary spittoon”).
The auxiliary spittoon may be provided to perform servicing operations on the printheads
102
-
108
in addition to those performed by the main spittoon. In addition, auxiliary spittoons may provide at least one specialized function, e.g., the application of primer on the printheads. Moreover, auxiliary spittoons may be provided in situations where the printer architecture calls for certain servicing operations to be performed in the auxiliary spittoons. For example, the auxiliary spittoon is oftentimes provided when the main spittoon has insufficient volume to contain ink spitted from the printheads. In addition, auxiliary spittoons may be utilized as part of a servicing routine before or after printing a page, during the printing process, and for specific servicing treatments, e.g., recoveries, cleaning, new printhead installation, etc.
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 main spittoon. Thus, those nozzles of the printheads
102
-
108
that actively drop ink onto the medium typically are not required to spit into the main 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 relatively reduce the negative effects of decap, the main spittoons typically perform 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 main spittoons at various times during a printing operation to substantially prevent the occurrence of decap. Additionally, the main spittoons 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.
In performing bi-directional printing operations, especially when the printmode is set for the printheads to perform a left to right sweep, the inverse relationship between print quality and throughput is more evident. In one respect, because the main spittoon is typically not utilized to perform the servicing operations of the main spittoon, if the width of the plot is relatively small, i.e., letter size, A4, etc., the printheads must travel the full length of the printer for the servicing operations on the printheads to be performed, thus decreasing throughput. Otherwise, if the servicing operations are more sparsely performed, then the print quality may be adversely affected.
In those situations where throughput is not relatively important, e.g., during printhead replacement, printhead recovery, etc., the amount of time required to perform these functions is not necessarily critical and thus the amount of time required to use the main spittoon is not relatively detrimental. However, in those instances where throughput is a relatively important factor, and the auxiliary spittoon must be utilized, e.g., the geometry and configuration of the main spittoon is configured for normal spitting but is unable to contain the amount of ink necessary for the certain spitting operation, the carriage must move to the auxiliary spittoon to perform these functions, thereby adversely affecting throughput of the printing operation.
SUMMARY OF THE INVENTION
According to one aspect, the present invention pertains to a method for operating a printer having a main spittoon, an auxiliary spittoon, and a printhead. The printhead is operable to perform a uni-directional or bi-directional printing pass. In the method, a selected printmode is received and a decap time is determined in response to the received printmode. Nominal times to complete a uni-directional sweep and a bi-directional sweep are estimated and a last time the printhead was refreshed is determined. A servicing operation is performed in response to the last time the printhead was refreshed ex
Bruch Xavier
Girones Xavier
Vega Ramon
Hewlett--Packard Company
Tran Huan
LandOfFree
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