Bendable Light Guide with Separation Space for Thermal Stress
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Solution Overview
Problem
Lighting devices with LED elements and light guides face mechanical failure due to significant mechanical stress caused by thermal expansion mismatch between light guide materials and electrical conductors, particularly evident in high aspect ratio devices.
Innovation Solution
A bendable lighting device design featuring a light guide divided into two portions with a separation space, where the first portion is in direct contact with the LED element for optimal optical coupling and mechanical stability, and the second portion is spaced to reduce thermal expansion effects, connected by a deformable spring structure to allow relative movement and decouple thermal expansion stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bendable light guide made of silicone or comparable material is used, then the light guide is easy to process and inexpensive, but thermal expansion mismatch with electrical conductors causes significant mechanical stress and increases risk of mechanical failure
Solution Approach 1:
The light guide is divided into multiple segments or portions along its length. Each segment can expand and contract independently in response to thermal changes, reducing the transmission of mechanical stress throughout the entire structure. This segmentation allows the light guide to accommodate thermal expansion while maintaining structural integrity and connection to LED elements.
2Reliability
If the volume of light guide material in contact with the LED element is reduced, then thermal expansion mismatch effects are minimized, but optical coupling may be compromised
Solution Approach 1:
The light guide features localized contact regions with optimized geometry and material properties at the LED interface. These contact regions are designed to provide sufficient optical coupling while maintaining a limited volume to reduce thermal expansion effects. The rest of the light guide structure has different properties optimized for light guidance and flexibility.
3Adaptability or versatility
If the light guide is made flexible and bendable, then adaptability to mounting surfaces is improved, but mechanical stability and thermal stress resistance may be reduced
Solution Approach 1:
The light guide incorporates dynamic elements such as hinges, joints, or flexible sections that allow controlled bending and movement. These dynamic features enable the light guide to adapt to different mounting surfaces while maintaining structural integrity during operation. The flexible portions are designed to accommodate thermal expansion and mechanical stress without compromising overall stability.
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
The design reduces mechanical stress and failure risk by limiting the volume of light guide material in contact with the LED element, allowing for flexible mounting and operation under changing environmental conditions while maintaining effective light guidance and distribution.
Implementation Method 1
the thermal expansion of silicone or other comparable light guide materials may be relatively high compared for example to the thermal expansion of electrical conductors connected to the LED element
Implementation Method 2
the light guide comprises at least two separate portions... connected by a deformable spring structure to allow relative movement and decouple thermal expansion stresses
Data Source
AI summary
A lighting device comprises at least one LED element for emitting light into an emission direction. A bendable light guide is arranged to guide light emitted from the LED element. The bendable light guide comprises at least a first portion formed of an elastic, light transmitting light guide material covering at least the emission direction of the LED element, and a second portion formed of an elastic, light transmitting light guide material. In order to be able to function under varying environmental conditions, the second portion is arranged spaced from the first portion in the emission direction by a separation space.