Inkjet Nozzle Pressure Control During Power Failure
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Solution Overview
Problem
In inkjet printing apparatuses, power shutdown during ink circulation can lead to a rise in nozzle pressure due to the positive pressure of the pressurizing tank remaining while the negative-pressure tank is opened to atmospheric air, potentially breaking the ink meniscus and causing leakage.
Innovation Solution
The apparatus includes a control unit that manages positive and negative pressures using air channels and valves, ensuring the nozzle pressure remains at or below the meniscus breakage pressure by adjusting the air chamber connections and valve states, even when power is shut off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a normally-open type electromagnetic valve is used for the negative-pressure tank to ensure it opens when power is shut off, then the valve can automatically open to atmospheric air, but the pressurizing tank remains sealed with positive pressure, causing nozzle pressure to rise and breaking the ink meniscus
Solution Approach 1:
The air supply system is segmented into two independent channels: one channel controls the pressurizing tank with a normally-closed valve, and another channel controls the negative-pressure tank with a normally-open valve. This segmentation allows each tank to have independent pressure control during power shutdown, preventing the harmful interaction that occurs when both tanks share the same air supply state.
Solution Approach 2:
Instead of using the conventional approach where both tanks use normally-open valves that open to atmospheric air when powered off, the invention inverts the valve type for the pressurizing tank to a normally-closed valve. This inversion ensures that the pressurizing tank maintains its positive pressure and remains sealed during power shutdown, while only the negative-pressure tank opens to atmospheric air, thereby preventing meniscus breakage.
2Productivity
If the pressurizing tank is kept sealed during standby state to maintain positive pressure, then ink circulation can be quickly restarted, but the positive pressure combined with opened negative-pressure tank causes harmful pressure rise at the nozzle
Solution Approach 1:
The system dynamically adjusts the pressure state of each tank based on operational requirements. During standby, the pressurizing tank remains sealed to maintain readiness for quick restart, while the negative-pressure tank opens to atmospheric air to prevent harmful pressure buildup. This dynamic configuration allows the system to balance productivity with harm prevention.
3Reliability
If power is shut off during ink circulation, the normally-open valve of the negative-pressure tank opens automatically, but the pressurizing tank valve remains closed, creating an unbalanced pressure state that breaks the ink meniscus
Solution Approach 1:
The air supply control is segmented into independent channels for each tank with different valve types. The pressurizing tank uses a normally-closed valve that remains sealed during power shutdown, while the negative-pressure tank uses a normally-open valve that opens to atmospheric air. This segmentation creates independent pressure control that maintains overall system stability during power interruptions.
Solution Approach 2:
The invention changes the fundamental parameter of valve default state from normally-open to normally-closed for the pressurizing tank. This parameter change transforms the pressure behavior during power shutdown, allowing the pressurizing tank to maintain its pressure while the negative-pressure tank equalizes with atmospheric pressure, thereby preserving pressure balance stability.
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 configuration prevents meniscus breakage and ink leakage by maintaining nozzle pressure within safe limits during power outages, allowing the apparatus to safely transition to a standby state.
Implementation Method 1
a positive pressure is applied to the pressurizing tank and a negative pressure is applied to the negative-pressure tank by using an air pump
Implementation Method 2
a normally-closed type electromagnetic valve is used which is open when being electrified and is closed when being non-electrified as a valve for switching the pressurizing tank
Implementation Method 3
supply of ink from the pressurizing tank to the ink jet head and recovery of the ink from the inkjet head to the negative-pressure tank are performed by a water head pressure based on a positional relation between the pressurizing tank, the negative-pressure tank, and the inkjet head
Data Source
AI summary
A common air chamber is connected to an air layer of a pressurizing tank and to an air layer of a negative-pressure tank. A pressurizing-side communication valve opens/closes an air channel in an air conduit between the pressurizing tank and the common air chamber. A negative-pressure side communication valve opens/closes an air channel in an air conduit between the negative-pressure tank and the common air chamber. A negative-pressure tank atmospheric air opening valve switches the negative-pressure tank between a state shut off from the atmospheric air and a state open thereto. The pressurizing-side communication valve and the negative-pressure tank atmospheric air opening valve are of a normally-open type closed when electrified and open when not. The negative-pressure side communication valve is of a normally-closed type open when electrified and closed when not. While not electrified, a nozzle pressure of an inkjet head becomes a meniscus breakage pressure or less.