Ink ejection

An arrangement comprising, in combination:

• (a) an ink ejector head having an ink flow system incorporating
• (1) means forming a chamber capable of being supplied with ink from an ink reservoir and having a nozzle through which ink is ejected, and
• (2) a pressure producer capable of being subjected to pulses for applying pressure to the ink in said chamber so as to cause the ink to be ejected through said nozzle, said pressure producer being a ceramic oscillator comprising a ceramic oscillator element and first and second membranes, said second membrane being arranged in said ejector head and being spaced from said first membrane so as to divide the interior of said ejector head into an air chamber and an ink chamber;
• and
• (b) means for applying to said pressure producer a series of pulses consisting of alternating primary and secondary pulses of which only said primary pulses are pulses which cause the ink to be ejected through said nozzle, said secondary pulses occurring a predetermined time interval after the cessation of the application of the immediately preceding primary pulse and being pulses for counteracting the outside air pressure and preventing the entry of a column of air into said nozzle above the returning stream of ink when there is a pressure reduction in the ejection system, said secondary pulses being applied while said oscillator is at rest.