Coaxial Vacuum Drum Inter-Copy Gap Tracking
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Solution Overview
Problem
Ink jet printers with vacuum drum transport systems face issues with air flow turbulence at the inter-copy gap, leading to degraded print accuracy and distorted images due to unwanted air flow past the print heads, as the vacuum technology creates air flow disturbances even when no media is present, causing ink droplets to be deflected and resulting in misdirected or missing jets.
Innovation Solution
A coaxial vacuum drum system is implemented, which creates a dynamic inter-copy gap that moves with the media, reducing or eliminating air disturbances by maintaining a closed vacuum environment under the print heads, thereby minimizing image quality defects near the leading and trailing edges of printed media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum technology is used to transport media under ink jet print heads, then media transport reliability is improved, but air flow turbulence is created at the inter-copy gap causing print accuracy to deteriorate
Solution Approach 1:
The vacuum drum surface is segmented into multiple vacuum zones with different vacuum levels. A first vacuum zone applies sufficient vacuum to hold media against the drum during transport, while a second vacuum zone (at the inter-copy gap location) applies reduced or zero vacuum to eliminate air flow turbulence. This segmentation allows the system to maintain reliable media transport while preventing print accuracy deterioration at critical locations.
Solution Approach 2:
Different regions of the vacuum drum are assigned different vacuum characteristics tailored to their specific functions. The transport zone maintains high vacuum for reliable media holding, while the inter-copy gap zone transitions to low or zero vacuum to eliminate harmful air flow. This local differentiation resolves the contradiction by optimizing each zone for its specific purpose rather than applying uniform vacuum across the entire drum surface.
2Stability of the object's composition
If vacuum is applied under the media to prevent separation from the drum, then media stability is improved, but air flow disturbance occurs at the inter-copy gap leading to distorted images
Solution Approach 1:
The vacuum drum is divided into distinct vacuum zones where the first zone maintains high vacuum for media stability during transport, while the second zone at the inter-copy gap location reduces or eliminates vacuum to prevent air flow disturbance. This segmentation enables the system to maintain media stability where needed while eliminating harmful air flow effects at the inter-copy gap.
Solution Approach 2:
The patent converts the potentially harmful continuous vacuum into a beneficial controlled vacuum distribution pattern. By strategically applying reduced vacuum at the inter-copy gap zone, the system eliminates air flow disturbance that would otherwise cause image distortion, while maintaining sufficient vacuum in transport zones to ensure media stability. The harmful continuous vacuum is transformed into a beneficial zoned vacuum pattern.
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 effectively reduces or eliminates air flow disturbances, enhancing print accuracy by ensuring a consistent vacuum under the media while maintaining a non-vacuum inter-copy gap, resulting in improved image quality and reduced misdirected ink jets.
Implementation Method 1
vacuum drum transport to transport media under ink depositing print heads
Implementation Method 2
The turbulent air generates eddy currents across the print head face plate
Data Source
AI summary
A media transport system provides full vacuum under media as the media traverses an entire print path of an ink jet printer while simultaneously providing for a no-vacuum inter-copy gap that moves along with the media past print heads of the ink jet printer. This is accomplished with a dual vacuum inner/outer vacuum drum system that includes a first drum that has a matrix of holes that allows for full coverage of vacuum with a second underlying drum that is shifted to align a second set of holes to match the sheet pitch. By shifting the second drum in relation to the first drum, a combination set of holes is aligned to provide full vacuum across the media while a column of holes is blocked to provide a non-vacuum inter-copy gap.