Offset Printer Blanket Conditioning via Electrical Bias
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Solution Overview
Problem
In image forming apparatuses, ink smearing occurs due to inadequate ink-blanket adhesion, leading to poor print quality and variations in dot gain and optical density, which is exacerbated by the hydrophobic nature of the transfer blanket surface over time, especially after repeated use and exposure to contaminants.
Innovation Solution
Applying an electric bias of hundreds of volts to the transfer blanket during non-printing cycles at full press speed immediately after installation and periodically to increase the surface polarity, thereby reducing ink-blanket adhesion and preventing smearing by oxidizing the surface to make it more hydrophilic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transfer blanket surface becomes hydrophobic over time due to repeated use and contaminants, then ink-blanket adhesion increases, but this causes ink smearing and poor print quality
Solution Approach 1:
The patent applies electrical bias (hundreds of volts) to change the surface polarity parameter of the transfer blanket, transforming it from hydrophobic to hydrophilic state. This parameter change reduces ink-blanket adhesion and prevents smearing, thereby resolving the print quality degradation caused by hydrophobic surface development over time
2Object-generated harmful factors
If electrical bias is applied to increase surface polarity and reduce ink-blanket adhesion, then ink smearing is prevented, but excessive polarity may cause insufficient ink transfer from imaging plate to blanket
Solution Approach 1:
The patent applies electrical bias periodically during non-printing cycles rather than continuously. This periodic application maintains the blanket surface polarity within an optimal range, preventing both smearing (by avoiding excessive hydrophobicity) and ensuring adequate ink transfer (by avoiding excessive hydrophilicity). The periodic treatment balances the two competing requirements
3Productivity
If the transfer blanket is used repeatedly without conditioning, then productivity is maintained, but surface polarity degrades leading to variable dot gain and optical density
Solution Approach 1:
The patent applies electrical bias conditioning during non-printing cycles before the next printing operation. This preliminary action restores surface polarity and prevents degradation that would otherwise occur during repeated use, thereby maintaining dot gain consistency and optical density uniformity without sacrificing productivity
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 method enhances print quality by reducing ink smearing and maintaining consistent output by ensuring sufficient releasability of the transfer blanket, even with age, without causing permanent damage to the blanket.
Implementation Method 1
Applying an electric bias of hundreds of volts to the transfer blanket during non-printing cycles at full press speed immediately after installation and periodically to increase the surface polarity, thereby reducing ink-blanket adhesion and preventing smearing by oxidizing the surface to make it more hydrophilic
Data Source
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AI summary
According to an aspect there is provided a method for conditioning a blanket in an offset printer, the method comprising during a non-printing cycle of the offset printer, applying a first voltage to an intermediate transfer member of the offset printer, wherein the intermediate transfer member comprises the blanket, and maintaining the first voltage for a first period of time.