Variable Field Ink Jet Deflection for Short Circuit Protection
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Solution Overview
Problem
Existing ink jet printing technologies face limitations such as the inability to protect deflection electrodes from short circuits, constraints on ink conductivity, and the inability to create continuous gray shades due to fixed drop sizes, with transitions between deflection levels being difficult to manage.
Innovation Solution
A method and device for selective deflection of liquid jet segments using a set of deflection electrodes with variable, sinusoidal high voltage signals applied, ensuring the jet remains electrically neutral and allowing for common deflection control across multiple jets, with electrodes isolated and protected by an insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant high voltage is applied to the deflection electrode to enable jet deflection, then the jet can be deflected towards the substrate or gutter, but the electrode cannot be protected by an electrical insulator and is at risk of short circuits
Solution Approach 1:
The patent applies a dynamic, time-varying voltage signal (sinusoidal or square wave) to the deflection electrode instead of a constant high voltage. The voltage alternates between positive and negative polarities, which allows the electrode to be electrically isolated using an insulating layer while still achieving effective jet deflection during the active phases of the cycle. This dynamic approach resolves the contradiction by enabling both electrode protection and functional deflection.
Solution Approach 2:
The deflection electrode receives periodic voltage pulses with alternating polarity rather than continuous constant voltage. During each cycle, the voltage is applied only during specific time windows when deflection is needed, while the insulating layer protects the electrode structure during other phases. This periodic action allows the system to achieve reliable jet sorting without requiring the electrode to withstand constant high voltage stress.
2Reliability
If a constant high voltage is applied to the deflection electrode, then jet deflection is achieved, but costly electronic protection against short circuits is required
Solution Approach 1:
By using dynamic voltage signals with alternating polarity, the system eliminates the need for complex electronic protection circuits. The insulating layer provides passive, inherent protection against short circuits, replacing the need for expensive active electronic protection systems while maintaining reliable operation.
3Adaptability or versatility
If charging electrodes are placed close to each jet in a multi-jet system, then individual jet control is achieved, but each electrode must be connected and controlled individually increasing complexity
Solution Approach 1:
The patent merges the deflection control for multiple jets into a single common deflection electrode structure. Instead of requiring separate charging electrodes for each jet, the system uses one or more shared deflection electrodes that can control multiple jets simultaneously through the application of voltage signals. This combining approach reduces the number of individual connections and control lines needed while maintaining the ability to selectively deflect jets from multiple nozzles.
4Adaptability or versatility
If fixed drop sizes are used in continuous jet printing, then simple jet fragmentation is achieved, but continuous gray shades cannot be created
Solution Approach 1:
The patent changes the parameter of drop size by controlling the timing of jet fragmentation relative to the deflection electrode voltage cycles. By varying when drops are formed and deflected during the voltage cycle, the system can control both the size and trajectory of drops. This parameter control enables the creation of different gray shades through variable drop sizes and positioning without requiring complex additional mechanisms.
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 enables reliable and efficient ink jet printing with reduced risk of short circuits, allows for the use of less conductive inks, and enables the creation of continuous gray shades by varying drop sizes, improving print quality and reliability.
Implementation Method 1
The selection conventionally used is the electrostatic deflection of drops from the continuous jet: a first group of electrodes close to the break up point and called charging electrodes selectively transfers a predetermined electrical charge to each drop. All drops in the jet, some of which having been charged, then pass through a second arrangement of electrodes called the deflection electrodes generating an electric field that will modify the trajectory of the drops depending on their charge.
Implementation Method 2
The polarity of the potential applied to the deflection electrode always has the same sign, which means that the electrode cannot be protected by an electrical insulator to eliminate any risk of a short circuit between the jet and the electrode.
Data Source
AI summary
For printing, the principle of the continuous deflected jet is used: a device discharges a continuous stream of a liquid, which is deflected by an electric field created by a plurality of deflecting electrodes and directed toward a gutter. The printing of drops is performed by fragmenting the continuous jet into a segment formed opposite a shield electrode upstream of the deflecting electrode, so that the segment is not deflected and can be directed toward a substrate.The deflection electrodes are separated by an insulator and a variable potential is applied to each electrode; the potential for the entire set of electrodes cancels out such that the jet is not charged.