Continuous Inkjet Printhead Mass Charging and Deflection
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Solution Overview
Problem
Existing continuous inkjet printing systems face challenges in achieving high resolution and print quality due to limitations in drop placement accuracy, complexity in charge electrode structures, and sensitivity to variations in nozzle spacing and ink properties, particularly in electrostatic deflection methods.
Innovation Solution
A continuous liquid ejection system using mass charging and electrostatic deflection with a CMOS-MEMS printhead, where drop formation is controlled via image data-dependent break-off and synchronized charge electrode waveforms to create pairs of drops with distinct charge-to-mass ratios, allowing for improved drop placement accuracy and reduced volume variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electrostatic deflection is used to selectively deflect drops, then printing capability is achieved, but sensitivity to variations in nozzle spacing and ink properties increases
Solution Approach 1:
The system applies a preliminary charge to all drops at a common charging location before deflection. This preliminary charging action occurs uniformly for all drops regardless of their eventual destination, reducing sensitivity to subsequent variations in nozzle spacing and ink properties during the deflection and printing phases.
2Ease of operation
If each nozzle has its own charging electrode, then individual drop charging is achieved, but device complexity increases
Solution Approach 1:
The patent merges the charging function from individual per-nozzle electrodes into a single common charging electrode located at a common charging position. This unified charging structure serves all nozzles simultaneously, dramatically reducing device complexity while maintaining the capability to individually charge drops from different nozzles through subsequent deflection mechanisms.
Solution Approach 2:
The system introduces an intermediary deflection mechanism between the common charging electrode and the recording medium. This intermediary structure enables individual drop routing and charging control without requiring individual charging electrodes for each nozzle, thus reducing complexity while preserving individual drop charging capability.
3Ease of operation
If break off length is varied to control printing, then drop selection is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The system replaces mechanical break-off length variation with an electrostatic field-based charging and deflection mechanism. Instead of precisely controlling mechanical drop formation at different break-off points, the system uses electric fields to charge and deflect drops, substituting mechanical precision requirements with electrical control that is more easily implemented and adjusted.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances system robustness, reduces control complexity, and increases nozzle spacing, resulting in higher resolution and improved print quality while maintaining drop placement accuracy.
Implementation Method 1
The stream of ink may be perturbed in a manner such that the liquid jet breaks up into drops of ink in a predictable manner
Implementation Method 2
A charging electrode structure is positioned at the nominally constant break-off point so as to induce a data-dependent amount of electrical charge on the drop at the moment of break-off
Implementation Method 3
The charged drops are then directed through a fixed electrostatic field region causing each droplet to deflect proportionately to its charge
Data Source
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AI summary
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. The drop forming device is actuatable to produce a modulation in the liquid jet to selectively cause portions of the liquid jet to break off into one or more pairs of drops traveling along a path. Each drop pair is separated on average by a drop pair period. Each drop pair includes a first drop and a second drop. The drop formation device is also actuatable to produce a modulation in the liquid jet to selectively cause portions of the liquid jet to break off into one or more third drops traveling along the path separated on average by the same drop pair period. The third drop is larger than the first drop and the 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 period of formation of the drop pairs or the third drops, the drop pair period. The waveform also includes a first distinct voltage state and a second distinct voltage state. The charging device and the drop formation device are synchronized to produce a first charge to mass ratio on the first drop of the drop pair, a second charge to mass ratio on the second drop of the drop pair, and a third charge to mass ratio on the third drop. The third charge to mass ratio is substantially the same as the first charge to mass ratio. A deflection device causes the first drop of the drop pair having the first charge to mass ratio to travel along a first path, and causes the second drop of the drop pair having the second charge to mass ratio to travel along a second path, and causes the third drop having a third charge to mass ratio to travel along a third path. The third path is substantially the same as the first path.