Variable Air Knife Drying Control for Ink Separations
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Solution Overview
Problem
In high-speed electro-photographic printing, existing systems face challenges in uniformly drying images across different separations and substrates, leading to issues like over-drying, under-drying, and non-uniform transfer quality, particularly with varying percent coverage and substrate absorbency, which can result in image rejection and blanket failure.
Innovation Solution
A ventilation system with an air flow switching unit and controller that adjusts air supply parameters such as pressure, slit width, and angle based on separation order, percent coverage, and substrate type, enabling precise control of ink drying levels for each separation and page, using high-speed air knives that can toggle air supply rapidly to prevent over-drying and eliminate the need for null cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dryer with air knives is used to dry the image on the ITM at high speed, then the drying efficiency is improved, but the uniformity of drying across different separations and substrates deteriorates
Solution Approach 1:
The patent applies dynamics by making the air supply system adjustable and variable rather than fixed. The controller dynamically modifies air supply parameters (pressure, flow rate, timing) based on real-time detection of separation order, percent coverage, and substrate type, enabling the drying process to adapt to different imaging conditions and achieve uniform drying across variations.
Solution Approach 2:
The patent implements parameter changes by systematically varying air supply conditions including pressure levels, flow rates, and timing sequences according to the specific separation and substrate characteristics. This allows the drying process to be optimized for each unique combination of separation order, coverage percentage, and substrate absorbency, resolving the uniformity issue while maintaining high-speed operation.
2Reliability
If null cycles are added to increase drying level for heavy images, then the drying completeness is improved, but the printing speed and productivity deteriorate
Solution Approach 1:
The patent applies preliminary action by detecting imaging parameters (separation order, percent coverage, substrate type) in advance and pre-calculating the optimal air supply sequence and parameters before the drying process begins. This allows the system to achieve complete drying in a single optimized pass without requiring additional null cycles, thereby maintaining high printing speed while ensuring drying reliability.
Solution Approach 2:
The patent implements feedback by using detected separation and substrate characteristics to continuously adjust air supply parameters during the drying process. This closed-loop control ensures that the drying level is precisely controlled to achieve complete drying for heavy images without over-drying, eliminating the need for null cycles while maintaining productivity.
3Reliability
If air supply is increased to prevent over-drying of early separations, then the risk of over-drying is reduced, but the drying effectiveness for later separations deteriorates
Solution Approach 1:
The patent applies dynamics by implementing time-variable air supply control where the air flow rate and pressure are automatically adjusted based on the separation order detected by the controller. Early separations receive lower air supply to prevent over-drying, while later separations receive increased air supply to ensure adequate drying, with smooth transitions between different supply levels.
Solution Approach 2:
The patent implements periodic action by dividing the drying process into distinct phases corresponding to different separation groups. The controller applies different air supply patterns to different time periods or separation sequences, creating a periodic modulation of drying intensity that matches the periodic nature of multi-separation printing processes.
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 ensures uniform drying across separations and pages, increasing printing efficiency by reducing null cycles, improving transfer quality, and enhancing productivity, especially for high percent coverage images without requiring additional drying cycles.
Implementation Method 1
The air facilitates removing carrier liquid, e.g. by evaporation, for drying the image prior to transferring to the desired substrate
Data Source
AI summary
A system for adjusting air supply applied to evaporate carrier liquid during a one shot process printing job, comprises at least one air supply unit, at least one air knife unit configured for directing air toward at least a separation of the image, wherein each separation includes a single color of a plurality of colors used to form the full colored image, and controller configured for adjusting at least one air supply parameter between separations.