The present invention relates to a non-impact printing device for recording graphic symbols on ordinary paper by means of selective emission of ink particles by an ejector.
Devices of the aforesaid type are known wherein drops of liquid ink are emitted selectively through a nozzle by an ejector device actuated through the medium of a piezoelectric crystal and wherein to every electrical stress applied to the crystal there correspond a compression of the volume of the chamber containing the ink and a corresponding emission of drops through the nozzle.
Devices are moreover known wherein the emission of drops is caused by applying a potential difference between the conductive liquid ink and the mouth of the nozzle, as in the U.S. Pat. No. 1,958,406.
One of the problems which arise with the aforesaid devices known in the art is that the liquid ink encrusts the nozzle and ends by blocking it in the course of time. The choice of special water-based inks does not permit the problem of encrustation to be solved completely.