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Abstract

Ink jet printing method and apparatus in which an ink stream is projected from an oscillating structure to a record member which moves relative to the oscillating structure, creating a trace on the record member. The ink jet printer includes a reed head assembly, which comprises a capillary tube, a metal reed attached thereto, and means for inducing macroscopic oscillations of the metal reed and attached capillary tube at a resonance frequency of the metal reed, in a direction transverse to the axis of the capillary tube. An alternative reed head assembly includes a capillary tube carrying a metal sleeve, with the capillary tube as the primary oscillating member. The reed head assembly may include an ultrasonic transducer for inducing microscopic longitudinal vibrations in the metal reed and capillary tube, thereby regulating the parameters of breakup of the ink stream emitted from the capillary tube. In another version, an externally supported ultrasonic transducer transmits microscopic longitudinal vibrations directly to the capillary tube. Closed loop feedback circuitry is included to maintain the frequency of macroscopic reed oscillation at or near the reed's resonance frequency. The ink jet system further includes a charging electrode for applying one of two charge levels to groups of ink droplets comprising 'character elements'. A deflection/interception structure causes the deflection of droplets bearing a 'deflection' charge level and interception of one of the two charge groups, while allowing the other group to form an image on the record member.

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First Claim