Air Bar Web Redirection for Duplex Inkjet Smudging
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Solution Overview
Problem
Existing duplex inkjet printing methods for webs face challenges in maintaining print quality due to the need for multiple contact points and drying stages, which can cause smudging and image damage, especially when transitioning between printing and drying processes.
Innovation Solution
The use of an air bar to facilitate a 180-degree turn of the web, maintaining an air cushion to prevent hard contact and using a single downstream drying unit, allowing the first printed surface to remain wet while the second surface is printed, and employing a stacked printhead configuration with downwardly oriented print heads for accurate ink droplet application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a printed surface contacts a roller in the course of paper feed, then the web can be transported and redirected, but the ink may smudge or spread degrading print quality
Solution Approach 1:
An air bar is introduced as an intermediary element between the printed web and the roller contact point. The air bar generates a cushion of air that allows the web to follow the roller contour without hard contact, eliminating smudging while maintaining the redirection function
Solution Approach 2:
The invention uses pneumatic principles by employing an air bar that blows air onto the web surface to create an air cushion. This pneumatic mechanism enables non-contact support and redirection of the web, preventing ink damage while achieving the necessary web path change
2Manufacturing precision
If the web is passed through a radiant heating station to dry the printed surface, then print quality is protected from smudging, but the device complexity and energy consumption increase
Solution Approach 1:
The invention extracts and eliminates the complex radiant heating station from the system. By using the air bar to prevent smudging during web handling, the patent removes the need for intermediate drying stations, simplifying the overall device structure while maintaining print quality
Solution Approach 2:
The air bar system provides self-service protection for the printed surface during web transport. Instead of requiring an external drying station to protect the ink, the air cushion itself prevents smudging during handling, allowing the web to remain wet without quality degradation
3Manufacturing precision
If the web is redirected upwardly from horizontal to vertical orientation for drying, then the printed surface can be dried effectively, but the productivity is reduced due to multiple orientation changes
Solution Approach 1:
The invention removes the vertical redirection and drying station from the web path. The air bar enables the web to maintain its horizontal orientation throughout the printing and transport process, eliminating the need for upward redirection and associated productivity losses
4Device complexity
If a single downstream drying unit is used after duplex printing, then the device complexity is reduced, but the first printed surface remains wet during second surface printing potentially causing smudging
Solution Approach 1:
The air bar serves as a protective intermediary between the wet printed surface and the web handling system. It allows the first printed surface to remain wet during second surface printing without smudging, enabling the use of a single downstream drying unit while maintaining print quality
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 enhances print quality by avoiding image damage during turns and reduces the need for intermediate drying and cooling stages, enabling efficient duplex inkjet printing with improved image registration and reduced risk of smudging.
Implementation Method 1
The air bar is configured to generate a cushion of air to support the web during a 180 degree turn
Implementation Method 2
employing a stacked printhead configuration with downwardly oriented print heads for accurate ink droplet application
Data Source
Figure 1~2
AI summary
In a method and apparatus for duplex inkjet printing on a web medium, a web medium is guided along an S-form transport path having generally horizontal top, middle and bottom spans and two turns linking the spans. One inkjet printhead is located to print onto a one surface of the web at the middle span and another inkjet printhead is located to print onto the opposite surface of the web at one of the other spans. To protect the printed surfaces before they are dried at least one of the turns in the S-form path is effected using an air bar to hold the printed web surfaces away from hard equipment surfaces.