Priming system for pagewidth print cartridge

An ink priming system for a cartridge unit having a pagewidth printhead assembly in fluid communication with one or more ink storage compartments, the system comprising:

• a priming inlet provided on the pagewidth printhead assembly, the priming inlet including a valve incorporating an elastomeric seal;
• an ink flow passage providing fluid connection between the pagewidth printhead assembly and each of the ink storage compartments, the ink flow passage terminating at each of the ink storage compartments to form an ink outlet;
• an ink filter provided across the ink outlet;
• a vent hole defined through a surface of each ink storage compartment, the vent hole being defined through a surface opposite the ink outlet;
• and
• an ink retaining member provided within each ink storage compartment for receiving and storing ink, the ink retaining member being interposed between the ink outlet and the vent hole, wherein
• ink is supplied to the priming inlet of the pagewidth printhead assembly to flow from the pagewidth printhead assembly into the ink storage compartment via the ink flow passage and across the ink filter, and
• the ink received via the ink flow passage primes both the printhead assembly and the ink retaining member of each ink storage compartment with ink substantially simultaneously the amount of priming ink being controlled so that the ink retaining member is not completely saturated and remains dry nearest the vent hole.