Ophthalmic Lens Blocking with Flexible Bladder to Reduce Stress
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Solution Overview
Problem
Conventional lens blocking methods introduce mechanical stress and contamination issues, lead to lens distortions, and fail to accurately support larger lenses, resulting in thickness and prism errors due to inadequate support and positioning assumptions.
Innovation Solution
A two-stage method using a flexible bladder with thermoplastic material to shape and support the lens blank, eliminating direct bonding and allowing precise attachment with double-sided tape or light-cured adhesive, ensuring accurate positioning and reduced stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding material (low melting point metal alloy or wax) is used to hold the lens blank, then the lens blank can be securely held for surfacing, but mechanical stress is introduced causing lens distortions and requiring 40-60 minute stabilization time
Solution Approach 1:
The patent introduces a flexible membrane as an intermediary layer between the lens blank and the blocking assembly. This membrane distributes the clamping force uniformly across the lens blank surface, preventing localized stress concentrations that cause lens distortions. The membrane acts as a stress-distributing mediator that maintains secure holding while eliminating the mechanical stress problems of direct bonding contact.
Solution Approach 2:
The patent changes the physical state and distribution parameters of the bonding material by enclosing it within a flexible membrane. Instead of direct contact bonding that creates stress concentrations, the membrane-enclosed bonding material distributes force uniformly across the lens blank, changing the stress distribution parameter from concentrated to uniform, thereby eliminating distortions while maintaining holding stability.
2Reliability
If wax is used as bonding material, then it provides adequate holding, but it contaminates the laboratory and finished lenses making de-blocking time-consuming and problematic
Solution Approach 1:
The patent extracts the bonding material from direct contact with the lens blank by enclosing it within a flexible membrane. The membrane acts as a barrier that prevents the bonding material (whether wax or metal alloy) from contaminating the lens blank surface and laboratory environment. This extraction of the bonding material from direct contact eliminates contamination issues while maintaining the holding function through the membrane interface.
Solution Approach 2:
The flexible membrane serves as an intermediary barrier between the bonding material and the lens blank, preventing contamination transfer. The membrane allows the bonding material to provide secure holding while isolating it from direct contact with the lens blank and laboratory environment, thereby eliminating the harmful contamination effects of wax while maintaining adequate holding capability.
3Area of stationary object
If traditional blocking assembly is used, then it supports small lenses, but it fails to provide adequate support for larger lenses resulting in thickness and prism errors
Solution Approach 1:
The patent creates a universal blocking assembly design with a flexible membrane that can adapt to lens blanks of any size. The membrane can be stretched and shaped to conform to both small and large lens blanks, providing uniform support across the entire surface. This multi-functional design eliminates the need for size-specific blocking assemblies and ensures consistent manufacturing precision for lenses of all dimensions.
Solution Approach 2:
The patent introduces a dynamic, flexible membrane that can adapt its shape and support distribution to match the specific size and geometry of each lens blank. Unlike rigid traditional blocking assemblies, the flexible membrane dynamically conforms to the lens blank surface, providing optimal support distribution for any lens size, thereby preventing thickness and prism errors in larger lenses.
4Reliability
If blocking material is allowed to cool and contract, then it solidifies to hold the lens, but it introduces thermal stress requiring stabilization time before surfacing
Solution Approach 1:
The flexible membrane acts as a thermal intermediary between the cooling bonding material and the lens blank. It distributes thermal stresses uniformly across the lens blank during the cooling and contraction process, preventing localized thermal shock and stress concentrations. This intermediary protection allows the bonding material to solidify and secure the lens blank while minimizing thermal stress introduction.
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 approach minimizes thermal stress, eliminates contamination, and provides consistent support for larger lenses, reducing distortions and thickness errors while allowing precise surfacing without assumptions about lens positioning.
Implementation Method 1
a flexible bladder with thermoplastic material to shape and support the lens blank
Implementation Method 2
The common blocking materials also have significant expansion and contraction with temperature. As a result of these temperature variation characteristics, the bonding process introduces mechanical stress in the lens blank.
Implementation Method 3
attaching the lens blank to the shaped block assembly with light-cured adhesive
Data Source
AI summary
A method and associated implementing system eliminates much of the stress presently introduced by the bonding of ophthalmic lens blanks, or blanks to a holding device, namely a metal block. The method of attaching ophthalmic lens blanks to a blocking assembly comprises the steps of shaping a blocking assembly to take the shape of an ophthalmic lens blank surface of an ophthalmic lens, wherein the blocking assembly is not attached directly to the ophthalmic lens blank during shaping of the blocking assembly; and following the shaping of the blocking assembly, attaching the lens blank to the shaped blocking assembly.