Ink mist type high speed printer

Claim 1

In an ink mist type printer for use in printing information on a printing medium, which printer includes means for generating an ion stream comprising a pair of spaced upper and lower electrodes to which a high voltage is applied, means positioned between said electrodes for modulating said ion stream including an electrically controlled aperture board having a plurality of apertures therein, said apertures being positioned in at least one aligned row through which the ion stream passes and is modulated, means for supplying an ink mist between the aperture board and the upper of said electrodes whereby the modulated ion stream charges the mist according to the pattern to be printed on a printing medium arranged parallel to the flow of said ink mist and between said upper electrode and the aperture board whereby characters are printed on said medium by the attraction to said upper electrode of the charged ink mist; the improvement which comprises a conductive dust protection board positioned above said aperture board and below said printing medium, said protection board having a plurality of apertures formed therein corresponding to and located in alignment with said apertures of said aperture board, thereby to prevent dust particles from falling downwardly from the printing medium onto said aperture board.