Selective Head Purge for Liquid Ejecting Apparatus
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Solution Overview
Problem
Inkjet printers with multiple heads face issues of uneven ink discharge during pressurized purge, leading to ejection failures and excess ink consumption, as well as air bubbles entering nozzles, causing density unevenness in recorded images.
Innovation Solution
A method involving pre-pressurization of the ink reservoir, selective purge of individual heads by opening specific supply passages, and subsequent opening to atmosphere to reduce ink consumption and prevent air bubble entry, allowing for targeted maintenance of heads that require it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressurized purge is performed on all heads simultaneously, then ejection failures are prevented, but ink consumption increases and flow rate unevenness occurs
Solution Approach 1:
The patent divides the purge operation into head-specific segments. Each head is purged independently by controlling individual supply valves, allowing selective purge operations. This segmentation enables the system to purge only heads that need it, reducing overall ink consumption while maintaining ejection stability where required.
Solution Approach 2:
The patent applies different purge strategies to different heads based on their specific conditions. By monitoring each head's status and applying pressure selectively to specific heads through individual supply valves, the system provides localized quality control. This ensures reliable ejection where needed while minimizing ink waste in heads that are functioning properly.
2Reliability
If pressurized purge is performed on all heads simultaneously, then ejection failures are prevented, but image density unevenness increases
Solution Approach 1:
The patent segments the purge operation by head, with each head receiving independent pressure control through individual supply valves. This segmentation allows the system to monitor and adjust purge parameters for each head separately, ensuring uniform ink discharge across all heads and preventing image density unevenness while maintaining ejection stability.
3Ease of repair
If caps are separated after negative pressure purge, then maintenance is completed, but air bubbles enter nozzles causing ejection failures
Solution Approach 1:
The patent applies preliminary action by establishing positive pressure in the head before separating the cap. This pre-pressure condition prevents air bubbles from entering the nozzles when the cap is removed, thereby maintaining ejection stability during maintenance operations while still allowing cap separation for access.
Solution Approach 2:
The patent uses preliminary anti-action by counteracting the harmful effect of air bubble entry with a pre-established positive pressure state. This counter-pressure prevents air from being drawn into the nozzles during cap separation, thereby protecting against ejection failures while enabling maintenance access.
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 approach reduces ink consumption during purges, minimizes unevenness in image density, and prevents air bubbles from entering nozzles, ensuring stable ink ejection and improved image quality.
Implementation Method 1
pressurizing the liquid inside the liquid reservoir to a state of positive pressure higher than atmospheric pressure
Implementation Method 2
making the liquid reservoir open to the atmosphere
Data Source
AI summary
A sub-tank is pressurized by a pump, with head valves closed. Then, one of the head valves is opened to perform a first purge on a first head. After the one head valve is closed, a different one of the head valves is opened to perform a second purge on a second head different from the first head. After these purges, an open-to-atmosphere valve is opened, with the head valves closed, to decrease the pressures inside the heads which are increased by the purges. This allows a selective purge on only a head which requires a purge. As a result, the amount of ink forced out is suppressed during the pressurized purges. After the sub-tank is made open to the atmosphere, a depressurizing pump depressurizes the sub-tank to form ink menisci in the heads. This prevents air bubbles from being drawn into nozzles during the formation of the ink menisci in the nozzles after the purges.