Active Biased Electrodes for Reducing Electrostatic Fields Under Print Heads
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Solution Overview
Problem
In direct-to-paper ink jet printing systems, the high electrostatic field created by electrostatic tacking of the media substrate to a transport belt can interfere with ink jetting, leading to print quality defects, as the media must be held extremely flat to ensure good print quality.
Innovation Solution
A system using active biased electrodes positioned in a conductive platen under the print heads, with a voltage source to reduce the electrostatic field on the media substrate, including a voltage sensitive charge device to stabilize the belt charge and electrically isolated biased electrodes to counteract the electrostatic field, ensuring the field is reduced to less than 1 V/micron.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If electrostatic tacking is used to hold media flat in the print zone, then media flatness is improved, but electrostatic field interference with ink jetting increases
Solution Approach 1:
The patent applies the principle of converting harm into benefit by using the electrostatic field that causes interference to also serve the useful function of holding media flat. Biased electrodes are positioned in the conductive platen to generate an electrostatic field that simultaneously tacks the media to the transport belt (maintaining flatness) and is controlled to minimize interference with ink jetting. This resolves the contradiction by making the harmful electrostatic field beneficial through controlled application.
Solution Approach 2:
The patent employs parameter changes by adjusting the voltage applied to biased electrodes to optimize the balance between media flatness and ink jetting interference. By controlling the electrostatic field strength through voltage adjustment, the system maintains sufficient tacking force while reducing the field intensity that causes jetting defects. This dynamic parameter adjustment resolves the technical contradiction.
2Force
If high voltage is applied to charged rollers for media tacking, then media acquisition is improved, but electrostatic charge buildup on transport belt increases
Solution Approach 1:
The patent applies the principle of extraction by separating the media tacking function from the transport belt surface. Instead of charging the transport belt directly, biased electrodes in the conductive platen generate the electrostatic field that tacks media to the belt. This extracts the charge generation function from the belt itself, preventing charge buildup while maintaining effective media acquisition through the controlled electrostatic field.
Solution Approach 2:
The patent uses biased electrodes as an intermediary between the power source and the media-belt interface. These electrodes mediate the electrostatic interaction by generating the necessary field for tacking without requiring the transport belt to accumulate charge. The intermediary electrodes transfer the tacking function while preventing direct charge accumulation on the belt surface.
3Stability of the object's composition
If electrostatic field is increased for media control, then media stability is improved, but print quality defects increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage on biased electrodes to maintain optimal electrostatic field strength. The system modifies the field parameters to provide sufficient media stability for quality printing while avoiding excessive field intensity that causes ink jetting defects. This parameter optimization resolves the contradiction between media stability and print quality.
Solution Approach 2:
The patent implements feedback control through field sensing that monitors the electrostatic field environment and adjusts biased electrode voltages accordingly. This feedback mechanism ensures media stability is maintained while preventing electrostatic interference with ink jetting, thereby resolving the contradiction between media control and print quality by continuously optimizing field conditions.
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
Significantly reduces the electrostatic field under the print heads, minimizing print quality defects by maintaining a stable and controlled electrostatic environment, even under varying media and environmental conditions.
Implementation Method 1
reduce the magnitude of the electrostatic field on a printing media substrate
Implementation Method 2
electrostatic tacking of the media substrate to a moving transport belt
Data Source
AI summary
Embodiments described herein are directed to a system for reducing electrostatic fields underneath print heads in a direct marking printing system. The system includes: one or more print heads for depositing ink onto a media substrate; a media transport for moving the media substrate along a media path past the one or more print heads; a conductive platen contacting the media transport belt; an electrostatic field reducer that includes an alternating current charge device positioned upstream of the one or more print heads; and one or electrically isolated biased electrodes in registration with the ink deposition areas of the one or more print heads. The media transport includes a media transport belt and, when the media is on the transport belt it has an electrostatic field, which can cause printing defects. The electrostatic field reducer and electrodes reduce the electrostatic field on the surface of the media and thereby reduce printing defects.