Overmolding Optical Element on Thermoplastic Frame
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Solution Overview
Problem
Existing methods of overmolding an optical element onto a frame fail to prevent movement between the molded element and the frame due to temperature differences and mechanical wear, leading to potential deformation and assembly failure, especially with materials like plastics that have high thermal expansion coefficients.
Innovation Solution
The frame is designed with holes or asperities that provide mechanical attachment to the optical element, limiting its movement by creating a reinforced physical adhesion, with through holes or non-constant sections that enhance the mechanical grip, even when the frame is made of thermoplastic and the optical element is made of silicone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the optical element is overmolded onto the frame to form a single piece, then the assembly simplicity and manufacturing efficiency are improved, but the movement and deformation between the optical element and the frame cannot be prevented
Solution Approach 1:
The frame is segmented into multiple zones including a reception zone for the optical element and distinct attachment zones with holes or asperities. This segmentation allows the frame to provide both mechanical support and secure attachment points, preventing movement while maintaining the single-piece overmolded structure.
Solution Approach 2:
The frame is pre-formed with holes or asperities before the overmolding process. These features are prepared in advance to receive and secure the optical element, ensuring proper positioning and preventing movement during and after the molding process.
2Adaptability or versatility
If the frame and optical element are made of materials with different thermal expansion coefficients, then the adaptability to different material properties is improved, but temperature variations cause deformation and movement between the components
Solution Approach 1:
The frame features locally differentiated zones with specific geometries (holes, asperities) that provide enhanced mechanical interlocking at critical attachment points. This local structural enhancement compensates for the differential thermal expansion between materials by providing fixed reference points that maintain relative positioning despite overall dimensional changes.
Solution Approach 2:
The invention combines different materials (frame material and optical element material with different thermal expansion coefficients) in a composite overmolded structure. The mechanical attachment features (holes/asperities) create a bonded composite structure that maintains integrity across material interfaces despite thermal expansion differences.
3Adaptability or versatility
If the optical element is made of flexible material like silicone, then the optical performance and shape variety are improved, but the element tends to move and maintain difficulty its geometry
Solution Approach 1:
The optical element is nested within the frame structure, with the frame's reception zone accommodating the optical element and attachment zones securing it. This nested configuration provides geometric stability to flexible optical elements by constraining them within the rigid frame structure while allowing the optical element to maintain its flexible material properties.
Solution Approach 2:
The frame is pre-formed with specific geometric features (holes, asperities, reception zones) that are prepared before the overmolding process. These pre-formed features provide the necessary geometric constraints to stabilize flexible optical elements during and after the molding process, ensuring they maintain their intended geometry.
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 design effectively limits the degrees of freedom between the optical element and the frame, maintaining the assembly's integrity by preventing separation and accommodating thermal expansion, ensuring a stable optical assembly for applications like motor vehicle lighting and signaling.
Implementation Method 1
said frame being shaped so as to provide mechanical attachment between the frame and the optical element following the molding of the optical element onto the frame
Implementation Method 2
The physical adhesion between the frame and the overmolded optical element is reinforced
Implementation Method 3
temperature variations can deform both the molded element and the frame serving as a support
Data Source
Figure 1~2
Figure 3~4C
Figure 5A~5C
AI summary
The invention relates to an optical assembly (100) of a light module, in particular for lighting and/or signaling, especially for motor vehicles, comprising: - an optical element (102); - a frame (101); said optical element being overmolded on the frame, said frame being shaped so as to achieve a mechanical connection between the frame and the optical element following the overmolding of the optical element on the frame.