METHOD AND APPARATUS FOR EXTENDING THE ENVIRONMENTAL OPERATING RANGE OF AN INK JET PRINT CARTRIDGE

摘要

An ink jet print cartridge includes an ink reservoir (12), a print head (30) for ejecting ink from the reservoir and first and second pressure control mechanisms for limiting the reservoir underpressure. The first pressure control (36,38) mechanism limits reservoir underpressure by controllably introducing replacement fluid (i.e. air or ink) thereto. The second pressure (27) control mechanism limits reservoir underpressure by changing the volume thereof. The two pressure control mechanisms cooperate to regulate the underpressure in the reservoir at a desired value over a broad range of environmental excursions and permit use of a volumetrically efficient package.