Pressure Equalized Lighting Subassembly with Hydrophobic Vent
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Solution Overview
Problem
In signage applications, light string assemblies with LEDs are prone to water ingress due to pressure differences between the internal and external environments, leading to compromised overmolding and potential water submersion issues, especially in damp or wet conditions.
Innovation Solution
A lighting subassembly with a printed circuit board featuring through-holes for airflow, a lens covered by an overmold body, and a vent that allows air to flow while preventing water ingress, creating a pressure equalization system to protect against water submersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lighting subassembly is sealed to prevent water ingress, then water resistance is improved, but heat dissipation deteriorates due to trapped heat from LEDs
Solution Approach 1:
The patent employs a hydrophobic membrane (thin film) that selectively allows heat and air to pass through while blocking water molecules. This membrane creates a flexible barrier that maintains thermal pathways for heat dissipation from LEDs while providing water resistance, thus resolving the contradiction between sealing for water protection and maintaining heat dissipation.
Solution Approach 2:
The hydrophobic membrane contains micropores that are sized to exclude water molecules while allowing air molecules to pass through. These porous structures enable controlled airflow for heat removal while preventing water ingress, simultaneously addressing both water resistance and heat dissipation requirements.
2Temperature
If through-holes are added to the printed circuit board for airflow, then heat dissipation is improved, but water ingress risk increases
Solution Approach 1:
The hydrophobic membrane is positioned to cover the through-holes in the printed circuit board, creating a selective barrier. This allows air to flow through the holes for heat dissipation while the hydrophobic properties of the membrane prevent water from entering through the same openings.
Solution Approach 2:
The solution applies local quality by making only the through-hole areas hydrophobic through the membrane coating, while other areas of the circuit board maintain their original properties. This localized treatment enables airflow where needed while protecting vulnerable areas from water ingress.
3Strength
If the overmold body is made tight to seal the lens, then structural integrity is improved, but pressure equalization deteriorates leading to water suction
Solution Approach 1:
The hydrophobic membrane acts as a flexible pressure-equalizing barrier within the overmold structure. It allows air to pass through during pressure changes (maintaining pressure equalization) while blocking water, thus preventing water suction during submersion while maintaining the tight seal needed for structural integrity.
Solution Approach 2:
The hydrophobic membrane serves as an intermediary element between the internal subassembly environment and the external water environment. It mediates the interaction by allowing pressure equalization through air flow while preventing water ingress, thus resolving the contradiction between tight sealing and pressure equalization.
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 solution effectively prevents water submersion while allowing airflow, enhancing the robustness of lighting subassemblies in wet environments by maintaining pressure equalization and ensuring the integrity of the overmolding.
Implementation Method 1
Pressure equalization of the lighting subassemblies 55 is desirable, thereby making the subassemblies 55 more robust to water submersion
Implementation Method 2
configured to only allow air to flow therethrough such that the through-holes and the vent together create a venting system to allow airflow through the lighting subassembly
Implementation Method 3
A vent is also included in the subassembly, and is disposed adjacent to the through-hole of the printed circuit board in between the overmold body and the printed circuit board, configured to only allow air to flow therethrough
Data Source
AI summary
Provided is a lighting subassembly that includes a printed circuit board having one or more lighting elements thereon and a single through-hole at a center region thereof for air flow, a lens to cover the one or more lighting elements, and an overmold body covering the lighting assembly. The overmold body secures the lens in place and covers a back surface of the printed circuit board opposite the one or more lighting elements and includes a plurality of through-holes corresponding to the through-hole of the printed circuit board. A vent is also included in the lighting subassembly and is disposed adjacent to the through-hole of the printed circuit board in between the overmold body and the printed circuit board, configured to only allow air to flow therethrough such that the through-holes and the vent together create a venting system to allow airflow through the lighting subassembly.