Color ink jet drop generator using a solid acoustic cavity

Abstract

The drop projection device has an array of nozzles communicating with an ink cavity fed from an associated pressurized ink reservoir and has an acoustic cavity closely associated with the ink cavity. The acoustic cavity is filled with a solid material, and may be separated from the ink cavity by a membrane that may be selected of any ink compatible material for transmitting disturbances from the solid material to the ink channel (the membrane is not required, however). A transducer is mounted to the rear of the solid filled cavity, essentially in air. The transducer is a block of piezoelectric material separated into a plurality of parallel fingers by slices made from one side of the block. The height-to-width or height-to-thickness ratios are less than 10:4. The solid acoustic cavity is filled with a material having an acoustic impedance which is substantially equal to the ink acoustic impedance. The cavity itself is defined by a material having a high acoustic impedance. The narrow, shallow ink channel across the face of the acoustic cavity is less than 2 sq. mm. in cross-section to easily expel air bubbles which form during start/stop of the ink streams. The height of the ink channel is less than 0.1 of an acoustic wavelength in ink so that the channel does not act as a separate acoustic cavity with its own standing wave pattern.