Abstract: A gravity ink return system for a continuous ink jet printer of the kind having droplet generator means for directing streams of ink droplets along a print path and ink supply means including an ink reservoir and means for supplying ink from said reservoir to said generator. The gravity return system includes a catcher having an ink return inlet located laterally adjacent the droplet print path for receiving non-print droplets deflected from said path and a discharge passage constructed and located to slope downwardly from said inlet to an outlet of the catcher. A return conduit slopes continuously downwardly from said catcher outlet to the ink reservoir.

Abstract: To protect critical operative portions (e.g. the orifice plate) of ink jet printing apparatus from airborne debris particles (e.g. paper dust), a wall is provided to substantially enclose a region around those critical operative portions and filtered air is induced to flow through the enclosed region from a location proximate the operative portions to a droplet outlet. In one mode the energy of printing droplet streams induces the air flow. In another embodiment the energy of printing substrate movement induces the air flow.