Liquid ejection system including drop velocity modulation

Abstract

A continuous liquid ejection system includes a liquid chamber in fluidic communication with a nozzle. The liquid chamber contains liquid under pressure sufficient to eject a liquid jet through the nozzle. A drop formation device is associated with the liquid jet and is actuatable to produce a modulation in the liquid jet that cause portions of the liquid jet to break off into a series of drop pairs traveling along a path. Each drop pair is separated in time on average by a drop pair period. Each drop pair includes a first drop and a second drop. A charging device includes a charge electrode associated with the liquid jet and a source of varying electrical potential between the charge electrode and the liquid jet. The source of varying electrical potential provides a waveform that includes a period that is equal to the drop pair period. The waveform also includes a first distinct voltage state and a second distinct voltage state. The charging device is synchronized with the drop formation device to produce a first charge state on the first drop and to produce a second charge state on the second drop. A drop velocity modulation device varies a relative velocity of a first drop and a second drop of a selected drop pair to control whether the first drop and the second drop of the selected drop pair combine with each other to form a combined drop. The combined drop has a third charge state. A deflection device causes the first drop having the first charge state to travel along a first path, causes the second drop having the second charge state to travel along a second path, and causes the combined drop having the third charge state to travel along a third path.

Description

technical field [0001] The present invention relates generally to the field of digitally controlled printing systems, and in particular to continuous printing systems in which a stream of liquid breaks up into droplets, some of which are electrostatically deflected. Background technique [0002] Inkjet printing is recognized as a prominent contender in the digitally controlled electronic printing arena due to, for example, its non-impact, low-noise characteristics, its use of plain paper, and its avoidance of toner transfer and fixation. Inkjet printing mechanisms can be classified by technology as drop-on-demand inkjet (DOD) or continuous inkjet (CIJ). [0003] The first technique, "drop-on-demand" inkjet printing, uses a pressurized actuator (such as a thermal, piezoelectric, or electrostatic actuator) to deliver ink droplets that impinge on a recording surface. One commonly practiced drop-on-demand technique uses thermal actuation to eject ink droplets from nozzles. A h...

AI Technical Summary

Problems solved by technology

This limits the density of nozzle spacing that can be exploited in such an approach and severely limits the ability to print high resolution images

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