1. Field of the Invention
The present invention relates to ink jet cartridges used in ink jet printers and, more particularly, to ink filters for printheads of ink jet cartridges.
2. Description of the Related Art
Ink jet printers utilize cartridges that hold ink and which selectively dispense or eject the ink during printing through a printhead. The cartridges are filled with ink after assembly. Once the cartridge is filled with ink, the cartridge is closed and ready for use.
Ink jet cartridges typically include a body or housing defining a chamber or cavity for the ink, a printhead in fluid communication with the ink chamber including a plurality of ink emitting nozzles, and circuitry coupled to the printhead and adapted to allow controlled ejection of ink from selected nozzles of the printhead during printing. The printhead includes heating elements associated with each nozzle and coupled to the circuitry that allow the ink to be selectively ejected from the nozzle by forming drops. The number and spacing of nozzles in the printhead determines the resolution of the printing. Generally, ink jet printheads now have a resolution of between 300 dpi (dots per inch) to 1200 dpi with the trend towards 1200 dpi and greater. The greater the number of dots per inch, the smaller the holes or nozzles.
Ink cartridges may contain one or several colors and/or strengths of ink. In the case of multiple inks within a single ink cartridge, the ink cartridge includes a separate ink reservoir and printhead for each ink. Each ink reservoir is in fluid communication with a particular printhead by plumbing channels generally known as standpipes.
Because the nozzles are so small, particle contamination in ink jet cartridges is a problem. Particles in the ink, or originating elsewhere, can clog the various nozzle inlets and other parts associated with the printhead. If the nozzles become clogged with particles, print quality is degraded.
It is known to provide a fine mesh stainless steel filter at the ink inlet of a standpipe in order to filter or prevent particles that originate in the ink reservoir from reaching the printhead and possibly clogging the nozzles, vias, and/or bubble chambers. However, these fine mesh standpipe inlet filters are not effective in screening particles that originate in the plumbing channels or below from reaching and clogging the printhead. Therefore, if particles are shed in the ink plumbing or downstream thereof during manufacture, shipping, or field use, the ink cartridge may suffer from print degradation. In general, particles originating downstream of the ink reservoir are not filtered from the ink.
What is needed is a filter for particles originating downstream of the ink reservoir, such as in the plumbing channels below the wire mesh filter in an ink jet cartridge.