Thermoformed Windshield Lens Stack With Sacrificial Heat Shield
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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 that is more heat-resistant than the outermost lens, allowing for even heat and pressure application without damaging the lenses, and can be peeled off to reveal the conforming lens stack, with the sacrificial layer serving as a female mold cavity to distribute heat and pressure evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If drape forming is used to install flat film on curved windshield, then the film can be installed on 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 source and the outermost lens. This sacrificial layer has higher heat resistance than the lenses and absorbs excess heat, preventing overheating of the lenses while still allowing heat transfer to achieve conforming. The sacrificial layer is later removed after serving its protective function during the heating process.
2Reliability
If pressure is applied to film during installation, then adhesion to windshield is improved, but visible surface may be permanently scratched
Solution Approach 1:
The sacrificial layer is applied in advance to the outermost lens before the pressure application step. This preliminary protective coating prevents scratching during the pressure application and squeegee operations needed to achieve proper adhesion. After adhesion is secured, the sacrificial layer is removed, leaving the lens surface intact and undamaged.
3Shape
If heat is applied to shrink or stretch film, then film takes shape of windshield, but optical distortion occurs due to uneven heating
Solution Approach 1:
The sacrificial layer serves as a thermal mediator between the heat source and the lenses. It distributes heat more evenly across the lens surface, preventing localized overheating zones that cause optical distortion. The sacrificial layer's higher heat resistance allows it to withstand the heating process while protecting the lenses, and it is subsequently removed after achieving uniform heat distribution.
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 installation of lenses on curved substrates with improved adhesion and scratch resistance.
Implementation Method 1
applying heat and pressure to the sacrificial layer... ensures even heat and pressure distribution
Implementation Method 2
The sacrificial layer may be more heat resistant than the outermost lens of the stack... the sacrificial lens may comprise a biaxially oriented polyethylene terephthalate film that may be able to withstand temperatures between room temperature and 220° C. for two hours
Implementation Method 3
applying heat and pressure to the sacrificial layer... allowing for even heat and pressure application
Implementation Method 4
a sacrificial adhesive interposed between the sacrificial lens and 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.