Time-Varying Electrostatic Field for Ink Drop Acceleration
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Solution Overview
Problem
Inkjet printers face challenges in minimizing the time of flight for ink drops while preventing printhead contamination due to electrostatic fields, which affect the quality of printed images and increase maintenance needs.
Innovation Solution
An inkjet printer employs a time-varying electrostatic field between the printhead and the image receiving surface, controlled by a controller and waveform generator, to manage the flight of ink drops and satellite drops, ensuring they maintain the same polarity as the printhead, thus preventing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a static electrostatic field is used to accelerate ink drops, then the time of flight is reduced, but satellite ink drops are attracted back to the printhead causing contamination
Solution Approach 1:
The patent applies a time-varying electrostatic field instead of a static field. The field strength is dynamically adjusted in three stages: initially strong to charge the ink drop positively, then reduced to prevent satellite drop attraction to the printhead, and finally increased near the media to accelerate arrival. This dynamic control resolves the contradiction by preventing printhead contamination while maintaining reduced time of flight.
Solution Approach 2:
The electrostatic field is applied periodically with specific timing sequences. The field is activated during ejection to charge drops, deactivated or reduced during the flight phase to prevent satellite drop contamination, and reactivated near the media to accelerate arrival. This periodic modulation eliminates the harmful attraction of satellite drops to the printhead while preserving the time of flight benefit.
2Manufacturing precision
If smaller ink drop sizes are used to improve image quality, then the time of flight increases due to lower initial velocity
Solution Approach 1:
The patent changes the velocity parameter of ink drops through electrostatic acceleration. By applying an electrostatic field that exerts force on the charged ink drops during flight, smaller drops that would normally have lower initial velocities are accelerated to achieve velocities comparable to or exceeding those of larger drops. This parameter change resolves the contradiction by enabling small drop sizes for image quality while maintaining short time of flight through electrostatic acceleration.
3Loss of time
If printheads are placed in close proximity to the image receiving member to reduce time of flight, then the risk of damage or contamination to the printhead increases
Solution Approach 1:
The electrostatic field acts as an intermediary force that enables the ink drops to be accelerated without requiring the printhead to be in close proximity to the media. The field provides the accelerating force throughout the flight path, allowing the printhead to be positioned at a safe distance while still achieving short time of flight. This intermediary mechanism resolves the contradiction by decoupling the time of flight from the printhead-media distance.
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 solution reduces the time of flight for ink drops and prevents printhead contamination, enhancing image quality and reducing maintenance requirements by ensuring satellite ink drops are attracted to the image receiving member rather than the printhead.
Implementation Method 1
The electrostatic field generated between the printhead and the image receiving member produces a charge with an opposite polarity on the image receiving member, and the attraction between the charged ink drop and the image receiving member accelerates the ink drop
Implementation Method 2
the attraction between the charged ink drop and the image receiving member accelerates the ink drop and reduces the time of flight
Implementation Method 3
ensuring they maintain the same polarity as the printhead, thus preventing contamination... ensuring satellite ink drops are attracted to the image receiving member rather than the printhead
Data Source
AI summary
An inkjet printer includes an electrode in either a printhead or an image receiving member that is operatively connected to a waveform generator. During operation, a controller operates the waveform generator to generate an electrostatic field between the printhead and the image receiving member during operation of inkjets in the printhead to eject ink drops. The controller operates the waveform generator to reduce an amplitude of the electrostatic field while the ink drops travel toward the image receiving member during a time when satellite ink drops can be formed from the ejected ink drops. The controller subsequently operates the waveform generator to generate the electrostatic field while the ink drops are in flight after formation of the satellite to accelerate the ink drops and satellites towards the image receiving member.