Inkjet Printhead Purge Cycle Using Short Pressure Pulses
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Solution Overview
Problem
Inkjet imaging devices experience significant ink loss during printhead purging, with up to 10% of the total ink used for printing being lost during an 8-hour shift, due to the inefficiency of existing purging methods which involve prolonged pressure cycles and subsequent ink discharge.
Innovation Solution
A method and system for purging inkjet printheads that involves a controller-operated valve to build pressure in a conduit, monitor pressure thresholds, and apply this pressure briefly to the printhead, followed by a quick vent to atmosphere pressure, combined with bidirectional wiping to minimize ink loss, using a pressure sensor and accumulator to manage the purge cycle duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional purging methods are used with prolonged pressure cycles, then printhead operational status is restored, but ink loss increases significantly
Solution Approach 1:
The patent applies periodic action by using a pressure pulse of predetermined duration rather than continuous prolonged pressure. The controller applies pressure to the ink reservoir for a specific time interval (e.g., 0.5-2 seconds) then releases it, creating a periodic cycle that achieves printhead restoration while minimizing ink discharge. This contrasts with traditional continuous purging methods that maintain pressure for extended periods, resulting in significant ink loss.
Solution Approach 2:
The patent changes the parameter of pressure application duration from prolonged continuous pressure to a brief predetermined pressure pulse. By controlling the pressure duration parameter to be short (e.g., 0.5-2 seconds) rather than extended, the system achieves the necessary ink flow through printheads to restore operational status while dramatically reducing the total volume of ink discharged during purging operations.
2Reliability
If frequent purging is performed to maintain inkjet reliability, then inkjet operational status is improved, but ink consumption increases
Solution Approach 1:
The periodic pressure pulse method enables more frequent purging cycles to be performed within the same operational period. Since each pulse is brief and consumes minimal ink, the system can execute purging operations more frequently to maintain inkjet reliability without proportionally increasing overall ink consumption, unlike traditional methods where each purge cycle consumes significant ink.
Solution Approach 2:
By changing the pressure application parameter from extended duration to brief predetermined intervals, the ink consumption per purge cycle is reduced. This parameter change allows the system to perform purging operations more frequently while keeping total ink consumption lower than traditional methods, thereby maintaining inkjet operational status without excessive ink expenditure.
3Reliability
If prolonged pressure is applied during purging, then ink flows sufficiently to restore inkjets, but the purge cycle duration increases
Solution Approach 1:
The patent applies the skipping principle by rushing through the purging process with a brief high-intensity pressure pulse rather than maintaining lower intensity pressure for an extended period. The predetermined short duration pressure pulse (e.g., 0.5-2 seconds) delivers sufficient pressure to force ink through the printheads and restore inkjet operation quickly, then immediately releases pressure, thereby reducing overall purge cycle duration while achieving the necessary ink flow.
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 loss during purging by 95% compared to traditional methods, maintaining printhead operational status while conserving ink for printing, as illustrated by the reduced area under the pressure pulse graph and improved inkjet restoration efficiency.
Implementation Method 1
operating the pump with the controller to build a pressure in the conduit
Implementation Method 2
monitoring with the controller a signal from a pressure sensor operatively connected to the conduit between the valve and the pump
Implementation Method 3
The printhead controller generates firing signals that correspond to digital data for images. Actuators in the printheads respond to the firing signals by expanding into an ink chamber to eject ink drops onto an image receiving member and form an ink image that corresponds to the digital image used to generate the firing signals.
Implementation Method 4
operating the valve with the controller after a predetermined time has expired since the pressure was applied to vent the ink reservoir to atmosphere pressure
Data Source
AI summary
A purge cycle is performed with an ink delivery system of an inkjet printer by applying a pressure pulse to a printhead in the printer that is substantially shorter than pressure pulses previously used. A pressure at a predetermined threshold is generated behind a valve and then release to the printhead. The duration of the pressure application is in a range of about 150 milliseconds to about 250 milliseconds. This pressure pulse substantially reduces the amount of ink emitted during the purge. A bidirectional wipe of the printhead face is effective for restoring inkjets in the printhead even though the amount of emitted ink is substantially reduced.