Pin-Cavity Joint Assembly Using a Flexible Spacer Against Adhesive Shrinkage
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Solution Overview
Problem
Adhesive joints in lighting devices for motor vehicles face challenges due to volumetric shrinkage of adhesives during curing, which can alter the position of light sources or optical components, leading to a deterioration of the lighting effect.
Innovation Solution
A method involving the use of a flexible spacer positioned between the bottom surface of a cavity and the facing end of a pin, preventing the pin from repositioning during adhesive curing by eliminating adhesive volume below the pin and allowing only horizontal shrinkage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is filled into the cavity to join the pin to the carrier, then the pin is fixed in position, but the adhesive shrinkage during curing causes the pin to shift vertically towards the bottom surface of the cavity
Solution Approach 1:
A flexible spacer is introduced as an intermediary element between the pin and the bottom surface of the cavity. The spacer fills the gap completely, preventing adhesive from occupying the vertical space below the pin. This mediator eliminates the harmful vertical shrinkage effect while still allowing the adhesive to provide horizontal bonding.
Solution Approach 2:
The harmful element (adhesive in the vertical gap below the pin) is extracted from the system by replacing it with a flexible spacer. The adhesive is retained only in the horizontal bonding zone where it performs its useful function of joining, but is removed from the vertical space where it would cause detrimental shrinkage.
2Strength
If adhesive is used to fasten the pin, then the components are joined together, but the volumetric shrinkage during curing alters the adjusted position of the light source or optical component
Solution Approach 1:
The flexible spacer acts as a mediator that occupies the vertical space, preventing adhesive shrinkage from affecting the pin's vertical position. The spacer allows the adhesive to maintain horizontal bonding while eliminating the source of positional inaccuracy.
3Strength
If the cavity is filled with adhesive to ensure complete bonding, then joint strength is maximized, but the pin experiences vertical displacement towards the bottom surface during curing
Solution Approach 1:
The adhesive is extracted from the vertical gap below the pin and replaced with a flexible spacer. This eliminates the volume change that would cause vertical displacement, while the adhesive remains present in the horizontal bonding zone to provide joint strength.
Solution Approach 2:
The spacer provides localized support exactly where needed - in the vertical gap below the pin - without interfering with the adhesive's bonding function in the horizontal plane. This local intervention prevents vertical displacement while preserving horizontal joint strength.
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 solution stabilizes the pin in the target position, preventing both vertical and horizontal shifts due to adhesive shrinkage, thus maintaining the precise positioning of light sources and optical components in lighting devices.
Implementation Method 1
positioning a flexible spacer on the bottom surface of the cavity
Implementation Method 2
filling the adhesive into the cavity onto the flexible spacer
Implementation Method 3
The shrinkage of a conventional ultraviolet (UV)-light curable adhesive then typically yields an undesired subsidence of the pin during curing
Data Source
AI summary
A method is provided for joining a pin member of a first component to a second component with a cavity, using an adhesive, to fasten the pin in a target position extending at least partially into the cavity. A distance (D) is provided between the bottom surface of the cavity and the facing end of the pin. A flexible spacer is positioned on the bottom surface of the cavity. The thickness of the spacer equals or exceeds the distance (D) between the bottom surface of the cavity and the facing end of the pin in the target position. The adhesive is filled into the cavity onto the flexible spacer, and the pin is positioned in the target position. The adhesive is cured to obtain a joint between the pin and the second component.