Original Publication Date: 1988-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
One of the major problems in maintaining the reliability of a thermal ink jet printer is the problem related to clogging of the nozzles of the printhead. Each printhead has a plurality of ink filled capillary channels. Each channel terminates at one end with a nozzle which confronts a recording medium, such as paper. The other end communicates with a relatively small ink holding manifold. For a carriage type printer, one or more ink supply carriages has fixedly mounted thereon a printhead with means for sealingly interconnecting the printhead manifold with the ink in the cartridge. The ink in the printhead is maintained at a slightly negative pressure so that a meniscus is formed at each nozzle to prevent weeping of the ink therefrom. Ink droplets are ejected on demand by selectively addressing a resistor located in each channel slightly upstream from the nozzle with a current pulse. Each current pulse causes the resistor to form a momentary vapor bubble which ejects the droplet during the bubble's growth and collapse. Clogging occurs whenever the ink meniscus is exposed to air for relatively long periods of time without droplets being ejected, such as during printer standby.