Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-12-15
2003-08-12
Hsieh, Shih-wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06604811
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to printers such as ink jet printers, and more particularly to such a printer having a fast acting printhead maintenance assembly that quickly and immediately wipes, wicks and blots residual liquid ink from an ink jet printhead.
An ink jet printer of the type frequently referred to as drop-on-demand, has at least one printhead from which droplets of ink are directed towards a recording medium. Within the printhead, the ink is contained in a plurality of channels. Piezoelectric devices or power pulses cause the droplets of ink to be expelled as required, from orifices or nozzles located at the end of the channels. In thermal ink jet printing, the power pulses are usually produced by resistors also known as heaters, each located in a respective one of the channels. The heaters are individually addressable to heat and vaporize the ink in the channels. As a voltage is applied across a selected heater, a vapor bubble grows in that particular channel and ink bulges from the channel nozzle. At that stage, the bubble begins to collapse. The ink within the channel retracts and then separates from the bulging ink thereby forming a droplet moving in a direction away from the channel nozzle and towards the recording medium whereupon hitting the recording medium a spot is formed. The channel is then refilled by capillary action which, in turn, draws ink from a supply container of liquid ink.
The ink jet printhead may be incorporated into either a carriage type printer or a page width type printer. The carriage type printer typically has a relatively small printhead containing the ink channels and nozzles. The printhead is usually sealingly attached to a disposable ink supply cartridge and the combined printhead and cartridge assembly is attached to a carriage which is reciprocated to print one swath of information (equal to the length of a column of nozzles) at a time on a stationary recording medium, such as a sheet of paper or a transparency.
After each such swath is printed, the sheet of paper is transported or advanced forwardly (usually the movement involves stepping or indexing) a distance that is equal to the height of the printed swath or of a portion thereof so that the next printed swath is properly registered in an overlapping or contiguous manner therewith.
As is well known, in order to provide printhead long life, and to ensure continued high quality printing, ink jet printers usually include some type of a printhead maintenance assembly intended to clean the nozzles and prevent liquid ink from drying up and clogging such nozzles. Conventionally, such maintenance assemblies include a wiping only device and a capping device. Unfortunately, depending on the unpredictable amount of ink left as a meniscus or bubble at each nozzle and requiring cleaning, a wiping only device often merely disturbs such a meniscus, usually removes only some of that amount of ink. The result is ineffective cleaning of such nozzles, and hence poor quality prints for a while, and a reduced life for the entire printhead.
There is therefore a need for a fast acting printhead maintenance assembly that quickly and immediately scrapes, wipes, wicks and blots residual liquid ink from ink jet printheads in order to assure continued high quality printed images and a relatively longer printhead life.
SUMMARY OF THE INVENTION
In accordance with the present invention, there has been provided a fast acting printhead maintenance assembly that includes a support frame and a flexible wiping member mounted to the support frame. The flexible wiping member has a body portion, and a wiping edge adjoining the body portion for making wiping contact with a nozzle face of a printhead during relative motion between the printhead and the flexible wiping member. The fast acting printhead maintenance assembly also includes a liquid ink wicking and absorbing member attached to the body portion of the flexible wiping member for immediately and quickly wicking and absorbing liquid ink wiped by the wiping edge from the nozzle face of the printhead, thereby resulting in continued high quality printed images and a relatively longer printhead life.
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Hsieh Shih-wen
Nguti Tallam I.
Xerox Corporation
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