Passively-regulated vacuum plenum for inkjet printing airflow control
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Solution Overview
Problem
Inkjet printing systems using vacuum suction for media transport often experience image blurring due to air currents induced by the suction, particularly near the edges of the print media, leading to inaccurate droplet placement and potential jams.
Innovation Solution
A media transport assembly with a passively-regulated vacuum plenum system, utilizing two vacuum plenums to control airflow by adjusting the suction force across different groups of platen holes, reduces crossflows by distributing suction pressure more evenly across the vacuum platen, thereby minimizing airflow through the printhead group when an inter-media zone is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum suction is used to hold and transport print media, then media transport stability is improved, but image blurring occurs due to induced air currents
Solution Approach 1:
The vacuum plenum is divided into multiple separate plenums (first vacuum plenum, second vacuum plenum, third vacuum plenum) that can independently control suction in different regions. This segmentation allows the system to reduce suction in the inter-media zone while maintaining suction under the print media, thereby reducing air currents that cause blurring while preserving media transport stability.
Solution Approach 2:
Different regions of the vacuum platen are given different suction characteristics. The plenums are configured to provide reduced suction specifically in the inter-media zone where uncovered holes would otherwise create harmful air currents, while maintaining adequate suction in areas where print media are present. This local differentiation resolves the contradiction by addressing the harmful effect only where it occurs.
2Force
If vacuum suction force is increased to prevent media slippage, then media holding strength is improved, but air flow through uncovered holes increases causing more blurring
Solution Approach 1:
The vacuum system is segmented into multiple plenums that can independently regulate suction force. The first vacuum plenum serves the deposition region while the second and third plenums serve the inter-media zone. This allows the system to maintain strong holding force under media (first plenum) while reducing suction in uncovered areas (second and third plenums), preventing both slippage and excessive air flow.
Solution Approach 2:
The vacuum platen provides locally differentiated suction characteristics: high suction force where print media are present to prevent slippage, and reduced suction force in the inter-media zone to minimize air currents. This spatial variation in suction quality resolves the contradiction between holding strength and air flow control.
3Device complexity
If a single vacuum plenum is used to simplify the system, then device complexity is reduced, but airflow control precision deteriorates
Solution Approach 1:
Instead of a single vacuum plenum, the system uses multiple segmented plenums (first, second, and third vacuum plenums) each serving specific regions. This segmentation enables precise control over airflow distribution in different zones, allowing the system to reduce suction in the inter-media zone while maintaining it under media, thereby achieving the required airflow control precision.
4Device complexity
If vacuum suction is applied uniformly across the platen, then system simplicity is maintained, but image accuracy deteriorates due to crossflows in inter-media zones
Solution Approach 1:
The vacuum platen is segmented into multiple independently controlled plenums rather than using uniform suction. The first vacuum plenum serves the deposition region while the second and third plenums serve the inter-media zone. This segmentation allows non-uniform suction distribution that reduces crossflows in inter-media zones, thereby improving image accuracy without requiring overly complex active control mechanisms.
Solution Approach 2:
The system applies locally differentiated suction characteristics across the platen: uniform suction under print media for stable transport, and reduced suction in inter-media zones to minimize crossflows. This local quality approach improves image accuracy while maintaining relatively simple system architecture through passive flow regulation.
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 effectively reduces image blurring by ensuring ink droplets land closer to their intended deposition locations, maintaining printing accuracy and preventing jams, while maintaining efficient printing speeds.
Implementation Method 1
The vacuum source creates a vacuum state in the vacuum plenum, causing vacuum suction through holes in the movable support surface that are fluidically coupled to the vacuum plenum. When a print medium is introduced onto the movable support surface, the vacuum suction generates suction forces that hold the print medium against the movable support surface.
Implementation Method 2
Because these holes are uncovered, the vacuum of the vacuum plenum induces air to flow through those uncovered holes. This airflow may deflect ink droplets as they are traveling from a printhead to the substrate, and thus cause blurring of the image.
Data Source
AI summary
A printing system comprises a printhead to eject a print fluid to a deposition region. Print media are held by vacuum suction against a movable support surface, which moves over a vacuum platen to transport the print media through the deposition region. The vacuum platen has platen holes through which the vacuum suction is communicated. Multiple vacuum plenums are provided to supply the vacuum suction to different groups of the platen holes. A first vacuum plenum is fluidically coupled to a first group of the platen holes located at least partially in the deposition region, and to a second group of platen holes located upstream of the first group. A second vacuum plenum is fluidically coupled to a third group of the platen holes comprising at least some platen holes located between the first and second groups of platen holes.