Ricoh Company, Ltd.

Ricoh Systems, Inc.

Ricoh Corporation

Mark A Culpepper

Marco Padalino

Stephen J Bolema

An inkjet printer applies symmetrical driver vibrations to the full length of a linear nozzle array. A nozzle array and nozzle support plate are supported on the end of a supporting housing which also supports a plate for defining an ink flow cavity. The housing also defines an acoustic cavity which extends from the ink cavity to an end of the acoustic transducer and is filled with acoustically transmissive material. A transducer is bonded to the distal end of this acoustic material, so that when the transducer is energized, the vibrations are transmitted uniformly through the acoustically transmissive material and the acoustic cavity to the ink cavity, symmetrically driving the ink out through the nozzles of the nozzle plate. It has been found that the acoustic cavity in fact has a critical length which is related to the frequency of operation of this system. Specifically, for a frequency of 110 KHz, the length of the acoustic cavity should be 4.7 mm; for an operating frequency of 120 KHz, the length of the acoustic cavity from the ink cavity to the face of the transducer should be 4.2 mm. In order to produce uniform vibrations at the face of the transducer, grooves extend up from the distal end of the transducer about 9/10 of the way to the surface of the transducer which is bonded to the aroustic cavity material. These grooves should have a width of about 0.56 mm.

Inkjet drop generator

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.

Color ink jet drop generator using a solid acoustic cavity

A method of assembling a stimulator for an inkjet printer by attaching separate piezoelectric elements to a plastic or metallic membrane sheet which sheet, after encapsulation of the piezoelectric transducers, may be cut into a plurality of stimulators. Each individual stimulator which now comprises a membrane, a piezoelectric element, and the encapsulating material can then be bonded to an ink fluid cavity.

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Santa Clara County, CA, United States of America

Mark A Culpepper