Common Charge Electrode for Continuous Inkjet Droplet Separation
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Solution Overview
Problem
Continuous inkjet printing systems face challenges in accurately separating droplets with small break-off length differences due to sensitivity to electrode variations and ink properties, leading to complex control requirements and difficulties in maintaining uniformity across an array of nozzles.
Innovation Solution
A continuous inkjet system utilizing a common charge electrode with a time-varying electrical potential, where droplets break off during high or low voltage phases, allowing for less complex control and larger electrode spacing, and enabling droplet selection independent of stimulation signal types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two sets of charge electrodes closely spaced along the drop trajectory are used to create high electric field gradients, then droplet separation precision is improved, but device complexity and sensitivity to electrode variations increase
Solution Approach 1:
The patent merges the charge electrode function into a single common electrode structure that serves all nozzles simultaneously, eliminating the need for multiple separate electrode sets. This common electrode is positioned to interact with droplets from all nozzles in the array, reducing structural complexity while maintaining separation capability through temporal control of the electric field.
Solution Approach 2:
The patent employs periodic stimulation pulses applied to the common charge electrode in synchronization with the droplet formation cycle. By timing the electric field application periodically, the system creates distinct break-off points for print and non-print droplets without requiring complex spatial electrode arrangements. The periodic action allows the same electrode to provide differentiated charging conditions at different times.
2Measurement precision
If electrode spacing is reduced to increase electric field gradient, then droplet selection accuracy is improved, but manufacturing precision requirements and sensitivity to electrode variations increase
Solution Approach 1:
The patent transitions from static electrode configurations to dynamic temporal control of the charge electrode. Instead of relying on precise spatial positioning and fixed electrode geometries, the system uses time-varying voltage applied to the common electrode to create the necessary electric field gradients. This dynamic approach decouples droplet separation accuracy from manufacturing precision requirements.
Solution Approach 2:
The common charge electrode serves multiple functions simultaneously: it charges droplets from all nozzles in the array, creates the electric field gradients necessary for separation, and operates independently of individual nozzle conditions. This universal electrode design reduces sensitivity to variations in electrode spacing and positioning across different nozzles.
3Manufacturing precision
If stimulation amplitudes are adjusted from nozzle to nozzle to compensate for variations, then droplet separation uniformity is improved, but control complexity increases
Solution Approach 1:
The patent segments the control approach by separating nozzle-specific stimulation control from the common charge electrode control. Each nozzle maintains its own stimulation pulse for droplet formation, while the common charge electrode receives a unified periodic signal that is synchronized across all nozzles. This segmentation allows independent optimization of droplet formation at each nozzle while using a simple common timing reference for charging.
Solution Approach 2:
The system uses feedback from the droplet break-off detection to synchronize the charge electrode timing with the actual droplet formation process. By monitoring when droplets break off at each nozzle and using this information to adjust the charge electrode pulse timing, the system maintains uniform separation performance across all nozzles without requiring complex amplitude adjustments.
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 simplifies the control of droplet separation and enhances the robustness of the system by reducing the need for precise electrode positioning and stimulation amplitude adjustments, improving the reliability of droplet selection across multiple nozzles.
Implementation Method 1
A charge electrode electrically connected to the source of varying electrical potential is operable to produce a charge differential between the first liquid droplet and the second liquid droplet
Implementation Method 2
The deflection mechanism is operable to cause trajectories of the first liquid droplet and the second liquid droplet to diverge so that a trajectory of one droplet of the first and second liquid droplets causes the one droplet to be directed for collection and prevented from depositing on the surface
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A continuous inkjet system includes a plurality of nozzles producing a respective liquid jet through each nozzle. A stimulation device (42) at each nozzle is responsive to different types of stimulation signals to produce a modulation in the respective liquid jet to selectively control droplet break off relative to phases of the cycle of a varying voltage source (51) that is connected to a charge electrode (44). The break off phase of a droplet relative to the voltage phase of the voltage source will determine whether the droplet is charged or not charged. Droplets that become charged may be deflected from their paths and a deflection mechanism including the charge electrode determines which droplets are allowed to reach a surface for say printing and which droplets are collected and not deposited upon the surface.