In an ink jet recording apparatus of the ink-on demand type, the recording ink is forcibly sent from a pressure chamber in the recording head to nozzles which jet the recording ink onto a recording medium. An ink cartridge is a closed-up rigid body having an opening therein which permits gas to flow...http://www.google.fr/patents/US4558326?utm_source=gb-gplus-shareBrevet US4558326 - Purging system for ink jet recording apparatus
