Thermoformed Windshield Lens Stack Using a Sacrificial Mold Layer
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Solution Overview
Problem
Existing methods for installing flat transparent lenses on curved substrates like windshields result in uneven heating, overheating, and potential scratching due to the lack of a female mold cavity, leading to optical distortion and inadequate adhesion.
Innovation Solution
A method involving a moldable covering with a stack of lenses, an adhesive layer, and a sacrificial layer that includes a sacrificial lens and adhesive, allowing for even heat and pressure application by acting as a female mold cavity, which is then peeled off to reveal the final stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If heat is applied to shrink or stretch the film to take the shape of the windshield, then the film conforms to the curved substrate, but uneven heating or overheating occurs causing optical distortion
Solution Approach 1:
A mold cavity is introduced as an intermediary between the heating source and the film. The mold cavity acts as a heat distribution medium that evenly transfers heat to the film surface, preventing localized overheating and optical distortion while still enabling the film to conform to the curved substrate shape
Solution Approach 2:
The mold cavity is designed as a negative copy of the desired windshield shape. By forming the film against this mold copy, the film automatically acquires the correct curvature and shape without requiring excessive heat or manual manipulation that could cause distortion
2Reliability
If pressure is applied with a card or squeegee to adhere the film, then adhesion improves, but the visible surface becomes permanently scratched
Solution Approach 1:
The mold cavity serves as a protective intermediary between the pressure application mechanism and the film surface. Pressure is applied through the mold walls rather than directly with a card or squeegee, ensuring adequate adhesion while preventing surface scratching
Solution Approach 2:
The mold cavity is prepared in advance with the exact shape and surface properties needed. This preliminary preparation allows the film to be formed and adhered without requiring subsequent manual manipulation that could damage the surface
3Ease of manufacture
If a flat film is used on a compound curved windshield, then installation is simpler, but uneven heating and inadequate adhesion occur
Solution Approach 1:
The mold cavity acts as a mediating structure that enables uniform heat and pressure distribution across the film surface. This intermediary system maintains installation simplicity while ensuring reliable, uniform adhesion by controlling the forming process
Solution Approach 2:
The mold cavity enables controlled changes in temperature and pressure parameters across the film surface. By systematically varying these parameters through the mold structure, the film achieves proper conforming and adhesion without complex installation procedures
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
Ensures even heat and pressure distribution, preventing scratching and optical distortion, while allowing for a smooth installation process without damaging the underlying lenses.
Implementation Method 1
The sacrificial layer may be more heat resistant than the outermost lens of the stack... applying heat and pressure to the sacrificial layer
Implementation Method 2
an adhesive layer interposed between each pair of adjacent lenses from among the two or more lenses
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.