Windshield Lens Stack Thermoforming With a Sacrificial Layer
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Solution Overview
Problem
The installation of flat transparent lenses on curved windshields, such as windshields, often results in uneven heating or overheating, leading to optical distortion and potential scratching due to the lack of even heat and pressure distribution during the drape forming process.
Innovation Solution
A method involving a moldable covering with a stack of lenses and a sacrificial layer, where the sacrificial layer is more heat-resistant and less scratch-resistant than the outermost lens, allowing for even heat and pressure application and distribution, and is peeled off to reveal the conforming lens stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If drape forming is used to install flat films on curved windshields, then the film can be installed on the curved surface, but uneven heating or overheating occurs causing optical distortion
Solution Approach 1:
A sacrificial layer is introduced as an intermediary between the heating element and the outermost lens. This sacrificial layer has different thermal properties than the lens stack, allowing it to absorb and distribute heat more uniformly, preventing direct overheating of the lens and resulting optical distortion while still enabling the drape forming process to conform the film to the curved surface
2Reliability
If pressure is applied to the film during installation, then the film adheres to the windshield, but the visible surface may be permanently scratched
Solution Approach 1:
The sacrificial layer is applied in advance to the outermost lens before the drape forming process. This preliminary action creates a protective barrier that will be present during the pressing operation, preventing scratches from occurring in the first place rather than attempting to remove or repair them later
Solution Approach 2:
The sacrificial layer serves as a mediator between the installation tools (cards or squeegees) and the lens surface. It absorbs the mechanical stress and friction during the pressing operation, allowing adequate adhesion to be achieved while protecting the lens from direct contact with potentially damaging tools
3Shape
If heat is applied to shrink or stretch the film, then the film takes the shape of the windshield, but optical distortion occurs due to uneven or excessive heating
Solution Approach 1:
The sacrificial layer acts as a thermal mediator during the heating process. Its different thermal conductivity and heat capacity compared to the lens material allows it to buffer and evenly distribute the applied heat, enabling the film to be heated sufficiently to achieve the desired shape transformation while preventing localized overheating that would cause optical distortion
Solution Approach 2:
The sacrificial layer changes the thermal parameters of the system being heated. By having different thermal properties (such as higher heat capacity or lower thermal conductivity), it modifies the heat transfer characteristics, allowing for more controlled and uniform temperature distribution across the film during the drape forming 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 method ensures even heat and pressure distribution, preventing optical distortion and scratching, while allowing for a more efficient and damage-free installation of the lens stack on curved substrates.
Implementation Method 1
The installer may then apply heat and pressure to the sacrificial layer
Implementation Method 2
The sacrificial layer may be more heat resistant than the outermost lens of the stack
Data Source
AI summary
Manufacturing a pre-molded stack of one or more lenses to be installable on a curved substrate such as a vehicle windshield includes placing a moldable stack of one or more lenses and adhesive layer(s) on a mold, applying heat and pressure to the moldable stack to produce a pre-molded stack of one or more lenses from the moldable stack, and removing the pre-molded stack from the mold. The pre-molded stack may have a compound curvature, which may match a curvature of the curved substrate. The mold may be formed using three-dimensional shape data derived from the curved substrate, such as by optically scanning the curved substrate.