Scitex Digital Printing, Inc.

Eastman-kodak Company

Mark C Bowers

Michael Joseph Piatt

Mark E Brown

James Alan Katerberg

John M Schneider

A continuous ink jet printer employing conductive ink and having a main ink supply, a supplemental ink supply, and a replenishment carrier fluid supply includes a fluid system that replenishes ink or carrier fluid based on the resistivity of ink in the main ink supply.

Concentration control for a continuous ink jet printer utilizing

A system for controlling the formation of droplets in a fluid stream includes a continuously flowing fluid stream through a droplet generator. The system further includes both a sinusoidal drive voltage at a predetermined frequency and a plurality of piezo electric crystals for causing the droplet generator to resonate and inducing a series of uniformly sized droplets to separate at regular intervals from the droplet generator. Finally, the system includes a drive signal for adjusting to the resonance of the droplet generator to control the formation of the droplets. The drive signal is applied to the crystals by a digital phase lock loop.

Digital phase lock loop stimulation generator

An ink jet printing device has a drop generator for producing continuous streams of ink drops from at least one orifice and further has stimulation control electronics for maintaining desired stimulation conditions in response to a feedback from the drop generator. First and second feedback transducers measure the stimulation amplitude in the drop generator and generate feedback output signals in response to the stimulation. The feedback output signals are approximately equal in magnitude and opposite in sign to each other when the stimulation amplitude in the drop generator is a desired stimulation mode. An amplifier, whose inputs are the feedback output signals, provides an amplifier output signal to the stimulation control electronics which is the difference between the two feedback output signals.

Ink jet stimulation monitoring

In an ink concentration measuring circuit, a light emitting diode emits light toward an ink cell. A first photo diode receives reflected light from the ink cell and provides a reference signal and a second photo diode receives direct light through the ink cell and provides an ink signal. A ratio of the reference signal to the ink signal is then calculated and used to determine a concentration of ink in the ink cell. Since changes in the ink temperature affect the ink concentration, the ink temperature may be measured and the result used to modify the ratio, compensating for the changes in ink temperature. Also, ink pressure may be measured and used to modify the ratio, compensating for changes in the dimensions of the ink cell.

Ink concentration measuring and control and control circuit

A switching power supply converts DC to DC voltages. The switching power supply has multiple phase time delayed voltage generating circuits and a single switching power supply regulator circuit. The multiple phase time delayed voltage generating circuits are then synchronized with a pulse period of the switching power supply regulator circuit to achieve the conversion.

Multi-phase switching power supply

The length of an ink jet filament as a function of stimulation amplitude is measured in an ink jet printing apparatus by locating a narrow charging electrode near the drop break-off point of the ink jet filament, varying the stimulation amplitude to vary the filament length, and measuring the amount of charge imparted to the ink drops as the filament length is changed. Stimulation amplitude is automatically adjusted by as a function of the measured charge.

Ink jet filament length and stimulation amplitude assessment system

An ink jet print head includes a manifold defining a fluid receiving reservoir, and an orifice plate mounted on the manifold and defining a plurality of orifices which communicate with the reservoir. Fluid flows through the orifices and emerges as fluid filaments which break up into jet drop streams. A stimulator transducer contacts the orifice plate and, upon receipt of a drive signal, vibrates the orifice plate so as to cause bending waves to travel along the plate. The bending waves stimulate the breakup of the jet drop streams. A sensor transducer is mounted on the orifice plate at the opposite end thereof from the stimulator transducer. The sensor transducer produces an electrical feedback signal which is proportional in amplitude to the amplitude of the bending waves. This feedback signal is used by a drive circuit to control the amplitude of the drive signal applied to the stimulator transducer. The sensor transducer is calibrated by observing the breakup of jet drop streams as the drive signal is varied, and when an optimum breakup is observed, the output of the sensor transducer is adjusted to a predetermined amplitude level. This adjustment is made by applying D.C. pulses of proper polarity to the sensor transducer, poling the piezoelectric transducer.

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Vandalia, OH, United States of America

Mark C Bowers