Ink droplet expelling apparatus

Abstract

Disclosed is an ink droplet expelling apparatus for expelling an ink droplet in response to an electric signal, compising a printing head provided with one or more ink chambers, electro-mechanical transducers disposed on the printing head corresponding to the ink chambers, and a driving signal generating circuit for producing electric signals for driving the electro-mechanical transducers. The elector-mechanical transducers are distorted by three different driving signals to reduce the volumes of the ink chambers to raise the pressure therein to thereby expel an ink droplet out of a nozzle formed at the front end of the head. The three driving signals are applied to the electro-mechanical transducers in a predetermined order, the first one giving the ink a velocity, the second one accelerating the ink to expel it in the form of an ink droplet out of the nozzle, the third one acting to suppress the pressure fluctuation in the ink chambers caused by the first and second driving signals as well as to supplement ink in the ink chambers from an ink tank.