Videojet Systems International, Inc.

Philip D Anderson

Robert I Keur

James E Clark

Michael J Rybicki

Resonator sensors namely piezoelectric benders are used for sensing fluid viscosity and density. The benders are inserted into a liquid to be monitored. An input voltage is applied to the bender causing it to vibrate in the liquid at a resonant frequency. Output voltage amplitude or frequency are monitored to determine changes in viscosity and density, respectively. The device may be used as a liquid level sensor and to control alteration of the viscosity of the fluid as, for example, by connection with a supply of ink or solvent in an ink jet printing device.

Resonator sensors employing piezoelectric benders for fluid property

A method and apparatus for accurately determining and setting the optimal nozzle drive voltage for an ink jet printer. The current carried by charged test drops is monitored by a sensing electrode and ammeter while the nozzle drive voltage is slowly varied between minimum and maximum points. A plot of drop current versus nozzle drive voltage provides an accurate determination of the good printing window for the particular nozzle under the operating conditions presented. This arrangement can be used for calibrating a new nozzle in an existing printer or for calibrating a new ink or font to ensure that operation will occur within the desired print window.

Method and apparatus for automatic setting of nozzle drive voltage in an

A control system is disclosed for an ink jet printer. The control system employs acoustic transducers to determine the velocity of sound in the ink and in a reference chamber containing only fresh ink. By comparing the two measurements it can be determined when to add additional solvent to the system to maintain solids concentration substantially constant.

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Wood Dale, IL, United States of America

Philip D Anderson