Laser-Welded Vehicle Light Assembly With Invisible Weld Zone
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Solution Overview
Problem
The existing laser welding process for motor vehicle lighting devices results in a non-optimized weld zone that can be visible through the first part, affecting the aesthetic appearance of the lighting device.
Innovation Solution
A method of laser welding between a first transparent polymer material and a second polymer material that absorbs the laser beam and is transparent to visible light, ensuring a high-quality weld that is not visible through the second part, using specific organic polymers like PMMA and PC, and a process involving irradiation with a laser beam and optional additional light beam for improved conformation and melting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional laser welding is used between a transparent part and an absorbing part, then the welding process is simple and efficient, but the weld zone becomes visible through the transparent part, degrading aesthetic appearance
Solution Approach 1:
The patent applies local quality by modifying only the local optical properties of the transparent part at the weld interface. A laser-absorbing layer is applied specifically at the welding zone of the transparent part, while the rest of the transparent part maintains its original transparency. This localized modification allows the laser beam to be absorbed at the interface for welding, while the visible light transmission through the main body remains unaffected, making the weld zone invisible from the external view.
2Reliability
If the laser beam is absorbed by the second part, then welding quality is improved, but the weld zone remains visible through the first transparent part
Solution Approach 1:
The patent introduces an intermediary laser-absorbing layer on the transparent part that acts as a mediator between the laser beam and the welding interface. This layer absorbs the laser energy locally at the welding zone, enabling high-quality welding without requiring the entire second part to be laser-absorbing. The intermediary layer ensures that only the weld zone interacts with the laser beam, preventing visible discoloration or damage to the broader visible surfaces while maintaining welding effectiveness.
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 method provides a high-quality weld that is aesthetically pleasing, particle-free, and toxic compound-free, with improved attachment of parts without particle emissions, enhancing the appearance and functionality of the lighting device.
Implementation Method 1
a first part transparent to at least one laser beam, said part comprising at least a first polymer material... the first polymer material can be transparent to one or more laser beam(s)... the beam thus passes through the polymer, the polymer material or the part with little or no energy loss
Implementation Method 2
at least a second part absorbing said laser beam and transparent to at least part of the visible light, comprising at least a second polymer material... the second polymer material can absorb one or more laser beam(s)... the second part heats up under the effect of the laser beam
Implementation Method 3
Welding is then carried out at the interface between the two parts when the laser beam reaches the second part absorbing said beam. In fact, at the interface, the second part heats up under the effect of the laser beam, which makes it possible to weld the two parts
Data Source
Figure 1~2
AI summary
The present invention relates to a motor vehicle light device (20) comprising: - at least a first part (2) transparent to at least one laser beam, said first part (2) comprising at least a first polymer material, and - at least a second part (6) absorbing said laser beam and transparent to at least a part of visible light, comprising at least a second polymeric material, said second part (6) being laser welded to said first part (2).