Droplet Ejection Nozzle Cleaning via Thermal Contraction
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Solution Overview
Problem
Existing droplet ejection apparatuses, such as ink jet printers, face inefficiencies in nozzle cleaning due to clogging from dried ink, which requires frequent cleaning to maintain functionality.
Innovation Solution
Incorporating a heater in the droplet ejection units that is activated when moving towards a cleaning station, allowing the units to cool while immersed in cleaning liquid, creating suction pressure for enhanced liquid flow and penetration, and alternating heating and cooling cycles for intense cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the nozzles are cleaned by immersing them in cleaning liquid and relying on capillary forces, then the cleaning process is simple to operate, but the cleaning efficiency is insufficient because the cleaning liquid flows slowly and does not penetrate deeply into the liquid chambers
Solution Approach 1:
The patent changes the temperature parameter of the droplet ejection units by heating them before cleaning and allowing them to cool during cleaning. This temperature change causes thermal expansion and contraction of the medium in the liquid chambers, creating pressure differences that drive the cleaning liquid to flow faster and penetrate deeper into the chambers, thereby improving cleaning efficiency while maintaining operational simplicity
Solution Approach 2:
The patent implements periodic heating and cooling cycles of the droplet ejection units. The heater is activated during movement to the cleaning station and deactivated during immersion to allow cooling. This periodic thermal action creates repeated expansion and contraction of the medium, enhancing the suction pressure and cleaning liquid flow in cycles, which improves cleaning effectiveness
2Loss of time
If air flushing is used to remove cleaning liquid from the nozzles, then the cleaning process is quick, but air bubbles may be trapped in the process liquid causing operational disturbances
Solution Approach 1:
The patent uses temperature parameter changes (heating) to control the removal of cleaning liquid from the liquid chambers. By heating the droplet ejection units after cleaning, the medium expands and creates pressure that pushes the cleaning liquid out through the nozzles. This thermal-driven removal avoids introducing air bubbles into the system, maintaining operational reliability while achieving efficient cleaning liquid removal
Solution Approach 2:
The patent replaces the mechanical air flushing system with a thermal-driven fluid pressure system. Instead of using air pressure to force cleaning liquid out (which introduces air bubbles), the system uses thermal expansion of the heated medium to create pressure that expels the cleaning liquid. This substitution eliminates the harmful introduction of air bubbles while maintaining effective cleaning liquid removal
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 method improves nozzle cleaning efficiency by allowing the cleaning liquid to flow with increased velocity, reach deeper into chambers, and effectively dissolve contaminants, reducing the risk of air bubbles and enhancing the cleaning process compared to air flushing.
Implementation Method 1
a heater is provided for heating the droplet ejection units, and the control system is adapted to activate the heater when the droplet ejection units and the cleaning station are moved or have been moved towards one another
Implementation Method 2
When the droplet ejection units are allowed to cool down while the nozzles are immersed in the cleaning liquid, the medium that fills the liquid chambers will shrink in volume, thereby creating a suction pressure that helps to actively draw-in the cleaning liquid into the nozzles
Implementation Method 3
at least in the initial phase of the cleaning process, the elevated temperature will also help to clean the nozzles more efficiently because a part of the residual heat will be transferred to the cleaning liquid and the increased temperature of the cleaning liquid promotes the dissolution of contaminants
Data Source
Figure 1
Figure 2
AI summary
A droplet ejection apparatus comprising: a number of droplet ejection units (16) each of which has a nozzle (18) connected to a liquid chamber (20) and an actuator (28) for expelling droplets of a process liquid; a cleaning station (32); and a control system (44) arranged to control a relative movement of the droplet ejection units (16) and the cleaning station (32) and to immerse the nozzles (18) into a cleaning liquid (38), wherein a heater (30) is provided for heating the droplet ejection units (16), and the control system (44) is adapted to activate the heater (30) when the droplet ejection units (16) and the cleaning station (32) are moved or have been moved towards one another, and to deactivate the heater (30) to allow the droplet ejection units (16) to cool down while the nozzles (18) are immersed in the cleaning liquid (38).