Ink jet print head cartridge

An ink-jet printer cartridge having a center reservoir chamber and two side reservoir chambers for holding inks of three different colors is provided with ink flow pathways of special configuration for connecting the reservoir chambers to exit ports at the print element. The ink flow pathways are provided with ridges extending along substantially their entire lengths so that air bubbles cannot completely block ink flow through the pathways. The ink flow pathways are disposed such that they have a vertical component of direction over their entire length and the pathways connecting the side reservoir chambers to exit ports include duct portions disposed at compound angles relative to the axes of the cartridge so that air bubbles, because of their buoyancy, will naturally tend to drift upwardly through the inclined ducts toward the reservoir chambers during normal usage, or drift toward the exit openings when the cartridge is inverted for priming. The duct portions of the ink flow pathways are generally trapezoidal in cross-section, the side walls intersecting the top wall at acute angles so that air bubbles cannot completely block the duct portions. The duct portions have end surfaces for directing air bubbles toward the reservoir chambers during priming, the end surfaces being end faces of plugs.