CARTRIDGE UNIT HAVING NEGATIVELY PRESSURIZED INK STORAGE

摘要

A cartridge unit (10) for an inkjet printer, with an ink storage compartment (46) and an ink feed system (30) for connection to a printhead (22). The ink storage compartment has a displaceable wall section (48) so that its variable storage volume (46) is variable. The displaceable wall (48) is biased (54) toward expanding the variable storage volume (46) so that there is a negative pressure in the ink storage volume (46), such that ink does not inadvertently leak from the ink ejection nozzles. Without negative pressure, an ink meniscus can bulge from the nozzles. The meniscus will 'pin' itself to the edge of the nozzle aperture and may be strong enough to stop ink leakage. However, paper dust or other contaminants will eventually stop the bulging meniscus from pinning itself on the nozzle rim and leakage occurs. A negative pressure in the ink storage volume makes the meniscus invert back into the nozzle aperture. As the meniscus does not bulge out of the nozzle, paper dust on the nozzle surface does not break the surface tension to cause leakage.