Silicone Hydrogel Lens Mold Assembly for Precise Heat Staking
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Solution Overview
Problem
Existing methods for producing silicone hydrogel contact lenses suffer from high defect rates due to misalignment and improper coupling of mold members, particularly in high-volume manufacturing, and are prone to defects when forming 'feather edge' designs.
Innovation Solution
A method and system for producing silicone hydrogel contact lens mold assemblies that involve precise alignment and coupling of mold members using a heat-staking process with controlled force application and delayed mold assembly, followed by a brief delay before pressing, to form a stable weld between mold members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat staking is used to couple mold members, then the mold members can be joined together, but the defect rate in lens member bodies increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the temperature, force, and time parameters during heat staking. The mold members are heated to a specific temperature range, pressed together with controlled force, and held for a defined duration to optimize weld strength while minimizing defects in the lens member bodies.
Solution Approach 2:
The patent replaces traditional mechanical coupling methods with a controlled heat staking process. Instead of relying solely on mechanical interference fits or external fasteners, the mold members are joined through localized thermal softening and welding, creating a more reliable and defect-free connection.
2Productivity
If mold members are placed together quickly for high volume manufacturing, then productivity increases, but alignment precision deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-aligning the mold members before the heat staking process. Alignment features and guides are incorporated into the mold design, ensuring that mold members are correctly positioned prior to heating and welding. This preliminary alignment maintains manufacturing precision even in high-volume production environments.
3Speed
If conventional heat staking is used without delayed pressing, then the process is faster, but weld quality deteriorates
Solution Approach 1:
The patent applies periodic action by implementing a multi-stage heat staking process with distinct phases: initial heating, delayed pressing after a specified time interval, and controlled cooling. This periodic approach allows the material to reach optimal temperature before applying pressure, ensuring high weld quality while maintaining reasonable process speed.
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
Significantly reduces defect rates in lens member bodies, achieving consistent quality with a standard deviation of less than 0.07 mm across batches of 100 lenses, particularly for 'feather edge' designs.
Implementation Method 1
inserting one or more heated elongate elements into the male and female mold members thereby causing a portion of the male and/or female mold members to become melted or softened
Implementation Method 2
Said melted or softened material then cools to form a weld between the male and female mold members
Data Source
AI summary
The present invention concerns methods and an apparatus for producing contact lenses, such as silicone hydrogel contact lenses, and further relates to methods and an apparatus for producing silicone hydrogel contact lens mold assemblies, methods and apparatus for producing silicone hydrogel contact lenses using such mold assemblies, and silicone hydrogel contact lenses and lens member bodies produced using such methods and apparatus.