Abstract: The invention relates to an ink jet printer comprising at least one nozzle from which ink is adapted to issue under high pressure in the form of fine droplets, a charging apparatus for charging the droplets, a deflector unit, a collecting apparatus provided with a knife edge for collecting and discharging droplets of a specific charge, and a recording support arranged downstream of the movable knife edge wherein the collecting apparatus is provided with a cleaning device and an extraction device which are such that a new or freshly cleaned part of the knife edge always faces droplets being separated.