Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-10-01
2003-07-22
Nguyen, Judy (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S023000
Reexamination Certificate
active
06595611
ABSTRACT:
BACKGROUND OF INVENTION
The invention relates to tracking ink ejections from nozzles of a printhead in an ink recorder. It finds particular application in conjunction with controlling maintenance of nozzles of the printhead based on ink ejection tracking and will be described with particular reference thereto. However, it is to be appreciated that the invention is also amenable to other applications.
Ink recorders of the type frequently referred to as ink jet printers, acoustic ink printers, or liquid ink printers, have at least one printhead from which droplets of ink are directed to a recording medium. Common methods of directing the ink droplets include continuous jetting under pressure followed by electrostatic or magnetic control of the flight of the droplets; drop ejection on-demand by pressure pulse from a piezoelectric transducer, a thermally expanding liquid or solid member, focused acoustic energy, or an induced liquid-vapor transition; or, on-demand extraction of the ink from a nozzle or pool by electrostatic, magnetic or wetting forces. In the most prevalent drop-on-demand ink jet recorders, the ink may be contained in a plurality of channels within the printhead where pressure pulses that push ink out of the channels or extraction force pulses that pull ink out of the channels are used to selectively direct ink to the image receiving medium. In order to define small droplets of liquid so that high quality printing of an image may be done, the channels and, especially, the ink emitting ending nozzles of the channels, maybe narrow and have a cross-sectional area on the order of the cross-sectional area of the drops to be emitted.
In a thermal ink jet printer, pressure pulses are generated by rapidly heating ink in a small channel or chamber so that a component of the ink expansively vaporizes creating a pressure impulse that ejects ink from a nozzle in liquid communication with the channel or chamber. The ink heating pulses are usually produced by resistors located on an inner surface of the ink channels or chambers that are pulsed with sufficient electric voltage to vaporize an ink component in a portion of the ink adjacent the resistors, typically, water. Thermal ink jet printheads usually have a plurality of ink emitters and a corresponding plurality of ink heating resistors that are individually addressable by voltage pulses to heat and vaporize ink. Thus the emission of ink drops from the plurality of emitters can be electronically controlled by the timing of voltage pulses applied to the resistor heaters corresponding to each of the plurality of emitters. Following a short time duration voltage pulse to a heater, ink adjacent the heater vaporizes explosively, pushing ink out of a nozzle that is in close fluid communication with the channel or chamber where the vapor bubble has been generated. The vapor in the bubble quickly cools and transitions back to a liquid state. This transition causes the bubble to collapse to create partial vacuum pressure that pulls ink away from the emitting nozzle. This push-pull sequence causes a portion of the liquid at the nozzle to separate as a droplet and continue moving in a direction away from the nozzle and towards the recording medium. Capillary action of the ink in the narrow channels and constricted nozzle region draws ink from an ink supply reservoir thereby readying the thermal ink jet drop emitter for the next electronic command to print a drop. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774.
A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337. That printer has a plurality of printheads, each with its own ink tank cartridge, mounted on a reciprocating carriage. The channel nozzles in each printhead are aligned perpendicular to the line of movement of the carriage. A swath of information is printed on the stationary recording medium as the carriage is moved in one direction. The recording medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information.
It has been recognized that there is a need to maintain the nozzles and channels of a printhead in an ink recorder, for example, by capping the printhead when the printer is idle for extended periods of time. Capping the printhead is intended to prevent the ink in the printhead from drying out, which could prevent ink from being properly ejected from a nozzle. There is also a need to prime a printhead before use to ensure that the printhead channels are completely filled with ink and contain no contaminants or air bubbles, and to also periodically eject ink from the nozzles of an uncapped printhead to maintain proper ink characteristics and functioning of the drop ejection process. The periodic ejection of ink from the nozzles of an uncapped printhead, also known as ink purging, is done to counteract the effects of ink component evaporation at the ink-air surface located at the ink emitting nozzle. Especially in the case of thermal ink jet inks, some ink component is necessarily vaporizable and, therefore, somewhat volatile and subject to evaporation. Purging ink periodically from a nozzle subject to evaporation serves to eliminate ink whose properties have changed due to loss of a volatile component, thereby eliminating a potential source of poor ejection performance. Maintenance stations designed to maintain printheads of various types are described in, for example, U.S. Pat. Nos. 4,855,764; 4,853,717; and 4,746,938. Various methods and apparatus for maintaining the operation of printheads are also described in the following disclosures.
U.S. Pat. No. 5,404,158 to Carlotta et al. discloses a maintenance station for an ink jet printer having a printhead with nozzles in a nozzle face and an ink supply cartridge is mounted on a translatable carriage for concurrent movement therewith. When the printer is in a non-printing mode, the carriage is translated to the maintenance station located outside and to one side of a printing zone, where various maintenance functions are provided depending upon the location of the carriage mounted printhead within the maintenance station. The printhead nozzle face is cleaned by at least one wiper blade as the printhead enters and leaves the maintenance station. Adjacent the wiper blade is a location for collecting nozzle-clearing ink droplets, followed by a capping location where a carriage actuatable cap moves into sealing engagement with the printhead nozzle face and surrounds the nozzle to provide a controllable environment therefore. A vacuum pump is interconnected to the cap by flexible hose with an ink separator therebetween. Priming is conducted when continued movement of the carriage mounted printhead actuates a pinch valve to isolate the separator from the cap and enable a predetermined vacuum to be produced therein by energizing the vacuum pump. Once the carriage mounted printhead returns to the capping location, the pinch valve is opened subjecting the printhead to the separator vacuum and ink is drawn from the printhead nozzle to the separator. Movement of the carriage mounted printhead past the wiper blade uncaps the nozzle face to stop the prime, enable ink to be removed from the cap to the separator and cleans the nozzle. The vacuum pump is de-energized and the printhead is returned to the capping location to await the printing mode of the printer.
U.S. Pat. No. 5,850,237 to Slade discloses an apparatus and method for maintaining the proper operation of an ink recorder having an printhead that prints an image on a recording medium by selectively depositing ink drops from a plurality of ink nozzles in response to image data. The ink recorder supports a plurality of performance modes and may be a color image recorder having a plurality of color inks and a plurality of ink nozzles for each color ink. A time period during printing is determined and the number of print drop commands received by each of the
Brooke Michael S
Nguyen Judy
Xerox Corporation
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