Firing Chamber Check Valve for Backflow-Free Ink Ejection
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Solution Overview
Problem
In printhead firing chambers, backflow of jettable material through the inlet during a firing event results in lower ejection volume, increased printhead size, higher manufacturing costs, and slower refill and printing speeds, due to reduced suction pressure and increased fluid resistance.
Innovation Solution
A check valve with a free-floating plug and holding posts is used to prevent reverse flow, where the plug blocks the inlet during firing and unblocks it for refill, allowing capillary forces to fill the chamber before the event, effectively reducing backflow without compromising printing speed or increasing the printhead footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inlet is left open during firing, then refill speed is improved, but backflow of jettable material occurs reducing ejection volume
Solution Approach 1:
The check valve uses a movable plug that dynamically changes the inlet state from open to closed based on pressure conditions. During refill, the plug retracts allowing open inlet for high refill speed. During firing, the plug closes the inlet to prevent backflow, resolving the contradiction between refill speed and ejection volume.
Solution Approach 2:
The check valve plug acts as an intermediary element between the inlet and the firing chamber. It mediates the conflict between needing the inlet open for refill and closed to prevent backflow, automatically selecting the appropriate state based on operational phase without external control.
2Quantity of substance
If the inlet is closed during firing, then backflow is prevented increasing ejection volume, but refill speed decreases
Solution Approach 1:
The check valve transitions from a static closed state to a dynamic system where the plug automatically opens during refill phases. This dynamic behavior allows the inlet to be closed during firing (preventing backflow) while opening during refill (maintaining high refill speed), resolving the contradiction.
Solution Approach 2:
The check valve plug is designed to automatically respond to pressure differential changes without external actuation. It self-regulates the inlet state based on whether the chamber is pressurizing (close inlet) or depressurizing (open inlet), eliminating the need for external control mechanisms.
3Quantity of substance
If larger firing chambers are used to compensate for backflow, then ejection volume is maintained, but printhead size increases
Solution Approach 1:
The check valve extracts and removes the backflow problem from the system by actively preventing it at the inlet. This eliminates the need to compensate for backflow losses by increasing chamber size, allowing maintenance of compact printhead dimensions while ensuring adequate ejection volume.
Solution Approach 2:
The check valve applies preliminary anti-action by preventing backflow before it can occur during the firing event. By closing the inlet in advance when pressure rises, it stops the harmful backflow effect that would otherwise require larger chamber volumes to compensate for.
4Quantity of substance
If inlet fluid resistance is increased to prevent backflow, then backflow is reduced, but refill speed decreases
Solution Approach 1:
Rather than statically increasing inlet resistance, the check valve dynamically controls inlet openness. The plug fully opens the inlet during refill (low resistance, high speed) and fully closes it during firing (infinite resistance, zero backflow), achieving both goals without compromise.
Solution Approach 2:
The check valve plug serves as an intermediary that completely controls inlet openness based on operational phase. It eliminates the need to partially restrict the inlet, allowing full openness for rapid refill while providing complete closure for backflow prevention.
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 allows for a larger volume of jettable material to be ejected without affecting refill speed or printing speed, reducing manufacturing complexity and costs, while preventing cross-talk between adjacent chambers.
Implementation Method 1
During a firing event, a number of actuators disposed within the chamber create a relatively higher pressure within the chamber compared to pressure within the chamber before the firing event to force the free-floating plug to block the inlet
Implementation Method 2
allowing capillary forces to fill the chamber before the event
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A check valve for preventing reverse flow of jettable material within a jettable material firing chamber during a firing event includes a free-floating plug. The check valve further includes at least one holding post, wherein the free-floating plug is arranged between at least one wall of the firing chamber and the holding posts, the at least one wall and the holding posts restricting the movement of the free-floating plug within the chamber.