Inline Viscometer for Pad Printing Colorant Viscosity Control
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Solution Overview
Problem
Pad printing systems face challenges in maintaining consistent colorant viscosity and solvent-to-solids ratio, leading to poor printing performance and requiring frequent technician intervention, especially in the manufacturing of tinted contact lenses where solvent evaporation and ambient temperature variations affect viscosity measurements.
Innovation Solution
A self-contained cart with inline viscometers, solvent dispenser, and peristaltic pumps that circulate colorant under pressure, applying negative atmospheric pressure to return unused colorant and automatically adjust viscosity in feed conduits based on real-time measurements, ensuring consistent delivery to the printing cup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solvent is allowed to evaporate from the colorant film on the cliché, then tackiness of the colorant increases to enable transfer to the printing pad, but colorant viscosity increases and printing performance deteriorates
Solution Approach 1:
The system continuously monitors viscosity parameters and dynamically adjusts solvent addition to maintain optimal viscosity range, preventing both excessive evaporation (which increases tackiness) and excessive viscosity (which degrades printing performance). This dynamic parameter control resolves the contradiction by finding the optimal balance point.
Solution Approach 2:
The viscosity monitoring system provides real-time feedback on colorant viscosity, which is then used to control solvent addition. This closed-loop feedback mechanism ensures that viscosity remains within the optimal range for both transfer capability and printing performance, resolving the contradiction between these two requirements.
2Reliability
If manual viscosity monitoring and solvent adjustment is performed, then colorant viscosity can be maintained, but manufacturing time is reduced and technician intervention is required
Solution Approach 1:
The system performs self-monitoring of viscosity and self-adjustment of solvent addition without requiring technician intervention. The automated viscosity control system continuously monitors colorant properties and adjusts solvent flow rates automatically, eliminating the need for manual intervention while maintaining reliable viscosity control throughout production.
Solution Approach 2:
The patent replaces manual mechanical viscosity measurement and adjustment with automated electronic sensors and computer-controlled solvent delivery. This substitution of manual operations with automated systems eliminates downtime associated with technician intervention while maintaining or improving viscosity control reliability.
3Measurement precision
If spindle measurement is used for viscosity monitoring, then viscosity can be measured, but measurements fluctuate when colorant level falls and vortices are created
Solution Approach 1:
The patent extracts the viscosity measurement function from the colorant reservoir environment where vortices and low colorant levels cause fluctuations. By using a separate, dedicated viscosity sensor positioned in a controlled location, the system eliminates the harmful effects of vortex creation and variable colorant levels that plague spindle measurements taken directly in the reservoir.
4Reliability
If technician intervention is required for viscosity maintenance, then viscosity can be adjusted, but exposure to solvents occurs and operation complexity increases
Solution Approach 1:
The automated system performs viscosity monitoring and solvent adjustment without requiring technician intervention. The computer-controlled system automatically adds solvent based on viscosity sensor readings, eliminating technician exposure to solvents while maintaining reliable viscosity adjustment capability throughout the production process.
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 system maintains optimal colorant viscosity and solvent ratio, reducing the need for manual intervention, minimizing downtime, and ensuring consistent printing performance by continuously monitoring and adjusting the viscosity of the colorant during the printing process.
Implementation Method 1
peristaltic pumps that circulate colorant under pressure
Implementation Method 2
applying negative atmospheric pressure within the cup to facilitate the circulation of ink from the cup back to the colorant container
Implementation Method 3
inline viscometers, solvent dispenser, and peristaltic pumps that circulate colorant under pressure
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The present invention provides systems and methods for providing colorant to a colorant cup apparatus that is adjacent to a pad printing cliché. The fluid colorant is fed from a colorant container through a feed conduit to the cup and an inline viscometer external to the colorant container measures the viscosity of colorant within the feed conduit. A control mechanism can dispense colorant solvent into the colorant container based upon a viscosity measurement performed by the inline viscometer. The disclosed systems, colorant cups and methods are useful in the preparation of tinted contact lenses.