Ink jet head

#The invention can be utilized in any pressure pulse drop-ejector system; however, the greatest benefits are realized when the heads of this invention are used in an ink jet recording system. Accordingly, the invention will be described in connection with an ink jet recording system.

#One problem with prior art ink jet heads is that air becomes ingested into the ink supply chambers, which slows or stops system response as explained herein. The present invention not only provides an ink jet head, which minimizes air ingestion but is also generally useful because of its ease of fabrication.

#FIG. 1 is a sectional view of a prior art pressure pulse ink jet head.

#FIGS. 2a-c show schematically how the operation of the FIG. 1 prior art ink jet head can ingest air.

#FIG. 3 is a sectional view showing a preferred embodiment of an ink jet head in accordance with the present invention.

#The invention relates to a head for use in an ink jet printer adapted to generate ink droplets on a recording paper sheet to form information thereon in accordance with, for example, a video signal.

#Several kinds of ink jet printers are well known in the art. The present invention is particularly well suited for use in a pressure pulse type ink jet printer of the drop-on-demand type; that is, a single droplet is expressed from the jet each time the driving force is stimulated in response to an input signal. The head could, of course, also be used in the kind of ink jet system wherein droplets of ink are continuously produced, and the droplets are, for example, electrostatically deflected to form an image.

#Referring now to FIG. 1, there is shown a prior art pressure pulse type ink jet printer, which comprises electrostrictive or piezoelectic member 1, also generally referred to as an electromechanical transducer element; a resilient member 2, which is in contact with ink in ink chamber 5; resilient member 2 forming a bimorph-type vibrator with electrostrictive element 1; an ink jet head base member 3 formed with an ink chamber 5; a front plate 4 formed with nozzle 6; and an inlet pipe 7 for supplying ink. When a voltage is applied to the electrostrictive element 1, the resilient plate 2, having its periphery fixed to the base member 3, is deformed with its center thrusting into the ink chamber 5 so as to reduce the inside volume of the ink chamber 5 and thus increase the pressure therein. This causes the ink level surface to project from the nozzle 6 and finally ink droplets to be expelled from nozzle 6. When the voltage is reduced, the resilient plate returns to its original position.