Ink Circulation Control for Printing Head Back Pressure
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Solution Overview
Problem
Existing printing apparatuses face challenges in accurately controlling head back pressure during wiping operations due to variations in ink viscosity, leading to difficulties in maintaining the desired pressure range, especially when dealing with ultraviolet inks that have large viscosity changes with temperature.
Innovation Solution
A printing apparatus with an ink discharge head, a wiping member, an ink storage section, and an ink circulation flow path, where the ink storage section is pressurized to a higher pressure during wiping operations than during print operations, and ink circulation is stopped, allowing for precise control of head back pressure by using a first pressurizing section and optionally a second pressurizing section with a switching mechanism, including a pressure pump, buffer tanks, and sensors to manage pressure accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ink circulation speed is increased in wiping operation to increase head back pressure, then bubbles can be prevented from entering the ink discharge head, but head back pressure becomes difficult to control within desired range due to variation in ink viscosity
Solution Approach 1:
The patent changes the operating parameters of the circulation pump, specifically controlling it to operate at zero circulation speed during wiping operations. This parameter change eliminates the variability caused by ink viscosity changes at different circulation speeds, allowing precise control of head back pressure within the desired range while still preventing bubble entry through the increased pressure from the pressurizing section.
2Productivity
If ink circulation is maintained during wiping operation, then ink flow can be sustained, but head back pressure varies due to ink viscosity changes making accurate control difficult
Solution Approach 1:
The patent extracts the ink circulation function during wiping operations by controlling the circulation pump to operate at zero speed. This separates the wiping function from the circulation function, allowing the pressurizing section to provide the necessary pressure for preventing bubble entry without the interfering effect of ink circulation that causes viscosity-related pressure variations.
3Device complexity
If a single pressurizing section is used, then device complexity is reduced, but pressure switching between wiping operation and discharge cleaning operation becomes slow
Solution Approach 1:
The patent segments the pressurizing function into two separate pressurizing sections: a first pressurizing section for wiping operations and a second pressurizing section for discharge cleaning operations. This segmentation allows each pressurizing section to be optimized for its specific function and enables immediate pressure switching between operations without the complexity of a single adjustable system, as switching is achieved by simply activating or deactivating the appropriate pressurizing section.
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 effectively increases head back pressure during wiping operations above print operations, reducing variations due to viscosity changes, ensuring accurate control and preventing issues like bubble entry or foreign material ingress, particularly beneficial for ultraviolet inks.
Implementation Method 1
a first pressurizing section that pressurizes the inside of the ink storage section in wiping operation in which the ink discharge head is wiped with the wiping member to a first pressure that is higher than a pressure in the ink storage section in print operation
Implementation Method 2
a circulation section that causes the ink to circulate in the ink circulation flow path, wherein the circulation section stops the operation in the wiping operation
Implementation Method 3
a second pressurizing section that pressurizes the inside of the ink storage section to a second pressure that is higher than the first pressure
Data Source
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AI summary
A printing apparatus includes an ink discharge head that discharges ink, a wiper that wipes the ink discharge head, a sub tank that stores the ink to be supplied to the ink discharge head, an ink circulation flow path, a circulation pump that causes the ink to circulate in the ink circulation flow path, and a first pressurizing unit that pressurizes the inside of the sub tank in the wiping operation in which the ink discharge head is wiped with the wiper to a first pressure that is higher than the pressure in the sub tank in the print operation for discharging the ink toward a print medium with the ink discharge head. The circulation pump stops the operation in the wiping operation.