Air assisted ink jet head with single compartment ink chamber

An ink jet head comprising:

• a single compartment ink chamber which has an ink supply inlet for receiving ink under pressure, the ink chamber having an ink chamber wall with at least one valve free ink orifice passageway leading to an internal ink drop-forming orifice outlet;
• an actuator means for producing pressure pulses in the ink chamber so as to cause ink to flow through the ink passageway and produce ink drop at the internal ink drop-forming orifice outlet;
• the ink orifice passageway being the only ink outlet that is open for ink to exit the ink chamber during ink drop formation;
• an air chamber with an air chamber wall through which an external ink jet head orifice is provided in axial alignment with the internal ink drop-forming orifice outlet, the air chamber being adapted to receive pressurized air which flows inwardly from the sides of the air chamber to form a generally coaxial air stream surrounding the internal ink drop-forming orifice outlet and which air stream is directed out of the external ink jet head orifice, the air stream carrying ink drops produced at the internal ink drop-forming orifice outlet, in response to the pressure pulses, outwardly through the external ink jet head orifice and toward printing medium.

An ink jet head for generating ink drops at a predetermined maximum operating frequency, the ink jet head including an ink chamber which has an ink supply inlet for receiving ink under pressure, the ink chamber haivng an ink chamber wall with a valve free ink orifice passageway leading to an ink drop-forming orifice outlet;

• an actuator means for producing pressure pulses in the ink chamber so as to cause ink to flow through the ink orifice and produce ink drops at the internal ink drop-forming orifice outlet;
• the actuator means comprising a diaphragm plate in contact with ink in the ink chamber and a piezoelectric crystal mounted to the diaphragm plate, the actuator means having a natural resonance frequency which is greater than or equal to two and one-half times the maximum operating frequency;
• the ink orifice passageway and ink chamber being sized such that ink in the ink orifice passageway has a natural resonance frequency which is greater than or equal to seventyfive percent of the maximum operating frequency but which is not from ninety to one-hundred and ten percent of the maximum operating frequency;
• and
• the ink supply inlet having a cross-sectional area sized small enough so as to not significantly alter the magnitude, frequency and damping rate of the pressure pulses in the ink chamber and large enough to permit filling of the ink chamber as ink drops are produced.