Patterned Preheat for Digital Offset Printing

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Solution Overview

Problem

Variable data lithography systems face high power consumption due to the need to evaporate a fountain solution, with existing technologies failing to effectively reduce energy usage, particularly in achieving wide cross-process widths and maintaining image quality.

Innovation Solution

A thermal printhead is used to selectively preheat a blanket surface, creating a patterned preheat that inhibits condensation of dampening solution vapor, allowing for the formation of a latent image with voids where ink can be applied, thereby reducing power consumption and improving image formation efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a high power laser is used to evaporate fountain solution for image formation, then image quality is maintained, but power consumption increases significantly

Engineering Contradiction:
Improveimage qualityVSAvoidpower consumption
Core Design Contradiction:
Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the high power laser system with a thermal print head that uses resistive heating elements to preheat the blanket surface. This substitution of the imaging mechanism eliminates the need for high power lasers while maintaining image formation capability through thermal control of dampening solution condensation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state and temperature parameters of the blanket surface by applying controlled preheat. By raising the blanket temperature in specific patterns before dampening solution application, the system prevents condensation in desired image areas, thereby forming the image through thermal parameter modification rather than laser evaporation.

Inventive Principle:
Principle #35Parameter changes

2Use of energy by moving object

If a conventional Raster Output Scanner is used instead of high power laser, then power consumption is reduced, but the ability to evaporate fountain solution at high speed is compromised

Engineering Contradiction:
Improvepower consumptionVSAvoidevaporation speed
Core Design Contradiction:
Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent applies preliminary heating to the blanket surface before the dampening solution is applied. By preheating the blanket in the desired image patterns, the system creates conditions that prevent dampening solution condensation in those areas, effectively forming the image before the actual printing process occurs. This preliminary thermal action replaces the need for high-speed laser evaporation during printing.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

Instead of using high energy to remove dampening solution (evaporation), the patent inverts the approach by using thermal preheat to prevent dampening solution condensation in the first place. This inverted logic—preventing condensation rather than removing liquid—enables high-speed operation with low power consumption.

Inventive Principle:
Principle #13The other way round (Inversion)

3Use of energy by moving object

If the blanket surface is heated to prevent condensation, then power consumption is reduced, but precise control of condensation patterns becomes critical

Engineering Contradiction:
Improvepower consumptionVSAvoidcondensation pattern control
Core Design Contradiction:
Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The system employs feedback control to monitor and adjust the thermal preheat patterns on the blanket surface. By sensing the actual temperature distribution and condensation patterns, the control system can fine-tune the heating elements to achieve precise image formation while maintaining energy efficiency.

Inventive Principle:
Principle #23Feedback

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

The solution significantly reduces power consumption by minimizing the need for high-power lasers and maintains image quality by ensuring precise ink placement on the substrate, addressing the limitations of existing systems in power efficiency and image formation.

Implementation Method 1

A thermal printhead is used to selectively preheat a blanket surface

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The thermal printhead is used to selectively preheat a blanket surface

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

creating a patterned preheat that inhibits condensation of dampening solution vapor

Methodology Applied
Scientific EffectCondensation: Condensation

Data Source

PatentEP3513971B1Patterned preheat for digital offset printing applications
Publication Date: 2020.07.29 XEROX CORP
  • EP3513971B1 patent drawingFigure 1
  • EP3513971B1 patent drawingFigure 2
  • EP3513971B1 patent drawingFigure 3

AI summary

A thermal printhead (TPH) is positioned to selectively preheat a blanket surface such as an arbitrarily reimageable surface of a variable lithography system. The blanket then immediately passes through a chamber containing dampening solution vapor. The vapor condenses only where the blanket has not been heated, thus developing an image ready for inking.