Optical Element Mounting with Undercut Mechanical Lock
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Solution Overview
Problem
Brittle optical components used in air vehicles and munitions are prone to catastrophic failure due to stress concentrations and tensile stresses, especially during high gravitational forces and vibrations.
Innovation Solution
An optical assembly with a mounting structure and optical elements featuring circumferential undercuts that align to form voids, filled with a conformal filler material to create a resilient mechanical lock, minimizing stress concentrations and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive is used to hold optical elements in place, then ease of manufacture is improved, but reliability deteriorates due to adhesive breakdown over time causing catastrophic failure
Solution Approach 1:
The mounting structure is segmented into multiple functional zones: an undercut region for mechanical interlocking, a conformal filler region for stress distribution, and a vent region for air evacuation. This segmentation allows each zone to perform its specific function optimally, with the undercut providing immediate mechanical retention and the conformal filler providing long-term stress management.
Solution Approach 2:
The solution employs a composite mounting approach combining rigid structural elements (mounting structure with undercut), flexible conformal filler material, and venting mechanisms. This composite structure integrates the advantages of mechanical interlocking with the benefits of stress-distributing flexible material, creating a multi-functional mounting system that addresses both ease of manufacture and long-term reliability.
2Reliability
If optical elements are tightly secured to prevent movement, then reliability is improved, but stress concentrations increase causing fracture initiation
Solution Approach 1:
The mounting structure implements local quality by providing different mechanical properties in different regions: the undercut region provides strong mechanical interlocking to prevent movement, while the conformal filler region provides a compliant, stress-distributing interface that accommodates thermal expansion and vibration without creating stress concentrations on the optical element surface.
Solution Approach 2:
The conformal filler material acts as a pre-positioned cushioning layer between the rigid mounting structure and the brittle optical element. This cushioning layer is designed to absorb and distribute stresses before they can concentrate on the optical element, protecting it from fracture during vibration, thermal cycling, and acceleration events.
3Reliability
If conformal filler material is used to create mechanical lock, then reliability is improved, but device complexity increases
Solution Approach 1:
The invention merges multiple functions into a single conformal filler material component: mechanical locking through the undercut geometry, stress distribution through conformal contact, vibration damping through material compliance, and thermal management through heat transfer. This consolidation achieves high reliability without proportionally increasing device complexity, as the filler material performs multiple critical functions simultaneously.
Solution Approach 2:
The conformal filler material is designed to self-adjust and self-lock during the curing process. As the material cures, it naturally conforms to the undercut geometry and creates its own mechanical interlocking features, eliminating the need for additional complex fastening mechanisms or adjustment procedures. The material serves itself to create the mechanical lock.
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
The solution effectively secures optical elements within the mounting structure, reducing the risk of fracture and shattering, and extends the product's lifespan by maintaining mechanical lock integrity even when adhesive properties break down.
Implementation Method 1
aligned with corresponding ones of the plurality of undercuts in the mounting structure to define a void; casting a conformal filler material in place in the void to create a mechanical lock between the optical element and mounting structure
Data Source
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AI summary
An optical assembly (30; 130) comprises a mounting structure (32; 132), a plurality of optical elements (34; 134), and a conformal filler material (54; 154). The mounting structure (32; 132) has a plurality of axially spaced circumferentially recessed undercuts (44; 144) formed into an inner surface (42; 142) of the mounting structure (32; 132). The optical elements (34; 134) are axially spaced in the mounting structure (32; 132). At least one of the optical elements (34; 134) includes an undercut (38; 138) in a perimeter edge surface (40; 140). The undercut (38; 138) is aligned with one of the plurality of undercuts (44; 144) in the mounting structure (32; 132), such that the aligned circumferential undercuts (38; 138) define a void (48; 148). The conformal filler material (54; 154) is cast in place in the void (48; 148) to create a mechanical lock between the optical element (34; 134) and mounting structure (32; 132).