Impact reduction of slew decap by multi-dotting

Details Impact reduction of slew decap by multi-dotting Impact reduction of slew decap by multi-dotting

2001-08-31

2003-06-10

Nguyen, Thinh (Department: 2853)

Incremental printing of symbolic information

Ink jet

Controller

C347S014000

Reexamination Certificate

active

06575545

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to inkjet printers, and more particularly to operations performed by a printhead of an inkjet printer to reduce slew decap effects.
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, 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
schematically illustrates a part of a known printer device (e.g., a large format inkjet printer) having an array of printheads
100
in a parallel row. More specifically,
FIG. 1
illustrates six printheads
102
-
112
. Each of the printheads
102
-
112
includes a plurality of printer nozzles (not shown) for firing ink
114
,
116
onto a print medium
120
. Although
FIG. 1
depicts the printer device as having six printheads
102
-
112
, printer devices have been known to possess any number of printheads, e.g., two, four, or more.
The printheads
102
-
112
are typically constrained to slew back and forth or move in a direction
170
with respect to the print medium
120
, e.g., paper, textile, and the like. In addition, the print medium
120
is also constrained to move in a further direction
160
. During a normal print operation, the printheads
102
-
112
are moved into a first position with respect to the print medium
120
and a plurality of ink droplets
114
,
116
are fired from the same plurality of printer nozzles contained within each of the printheads
102
-
112
. After completion of a print operation, the printheads
102
-
112
are moved in a direction
170
toward a second position and another print operation is performed. In a like manner, the printheads
102
-
112
are repeatedly moved in a direction
170
across the print medium
120
and a print operation is performed after each such movement of the printheads
102
-
112
. When the printheads
102
-
112
reach an edge of the print medium
120
, the print medium is typically moved a short distance in a direction
160
, parallel to a main length of the print medium
120
, and another print operation is performed. The printheads
102
-
112
are then moved in a direction
170
back across the print medium
120
and yet another print operation is performed. In this manner, a complete printed page may be produced.
A more detailed description of the printer device illustrated in
FIG. 1
may found in commonly assigned application Ser. No. 09/502,667 filed on Feb. 11, 2000, by Xavier Bruch et al., the disclosure of which is hereby incorporated by reference in its entirety.
As the printheads
102
-
112
move or slew, they create a current of air across the uncapped (or decapped) nozzles of the printheads
102
-
112
. Slew decap is a term of art used to identify this phenomenon in which the current of air causes evaporation of a solvent vehicle component of the ink. In general, evaporation of the solvent vehicle alters the chemical composition of the ink. More particularly, the change in chemical composition results in a less visible drop of ink on the print medium
120
. For example, evaporation may cause dye or pigment molecules to move from the nozzle, back into the firing chamber and thus diluting the solvent vehicle. Additionally, the rate of chemical change is relatively greater with lower drop volumes. Thus, as drop volumes generally decrease in order to improve image quality, the effects of slew decap may worsen.
In order to maintain the quality of the printed output, it is generally known to maintain the nozzles in substantially proper operating condition. In this respect, a service station
140
is typically provided along a travel path of the printheads
102
-
112
. The service station
140
is typically configured to maintain the health of the printheads
102
-
112
by performing servicing operations on the printheads, e.g., a means for wiping, collecting spit ink, capping the nozzles, etc. The service station
140
typically includes a plurality of service station units
142
-
152
for performing servicing operations on each of the printheads
102
-
112
. Generally speaking, a respective service station unit
142
-
152
is provided for each of the printheads
102
-
112
. The service station units
142
-
152
are typically housed within a service station frame
154
.
A servicing protocol is typically implemented to control the times and manner in which the printheads
102
-
112
are serviced. For example, in one respect, if it is detected that certain of the nozzles of the printheads
102
-
112
have not fired any ink drops for a certain period of time, the printheads are moved to a position over the service station
140
and caused to fire a normally set number of ink drops to thereby clean out the nozzles. In addition, a wiping mechanism positioned in the service station
140
may be caused to wipe excess ink off the nozzles to thereby increase the probability of their proper functionality. In another respect, the protocol may cause the printheads
102
-
112
to spit a set number of ink drops into the service station after each printing pass in an effort to substantially prevent ink from drying within the nozzles. The servicing protocol typically sets the number of times as well as the frequency of servicing operations based upon a set of normal values which are themselves typically set by the printhead or service station manufacturer. In addition, the normal values of the servicing protocol may vary according to the set printmodes. In general, servicing operations require some time to perform and thus decrease throughput.
The above-described servicing process is generally known as an open loop servicing technique. That is, the servicing protocol that determines when to service the printheads
102
-
112
as well as the degree of servicing to be applied, takes into consideration certain variables, e.g., time uncapped, drops fired during last printing pass, time in cap, etc. However, these types of servicing protocols typically apply a relatively heavy treatment to greater ensure proper printhead performance regardless of the age of the printheads
102
-
112
. One problem associated with the open loop servicing technique is that ink may be wasted by virtue of spitting more ink drops than is necessary, oftentimes resulting in faster aging of the printheads as well as the service station.
Printer devices have also been known to include a drop detector module
130
operable to detect whether the nozzles of the printheads
102
-
112
are properly firing ink. In these types of printer devices, servicing operations on the printheads
102
-
112
may be triggered by detected errors, e.g., clogged nozzles, and a user's expectations, e.g., desired print quality. It is generally known to position the printheads
102
-
112
over the service station
140
and spit a certain number of ink drops to clean out the ink in the nozzles. This servicing process is generally known as a closed loop servici

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