Pressure Equalizing Membrane for Oil-Resistant Housing Venting
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Solution Overview
Problem
Existing pressure equalizing devices with PTFE membranes face pore clogging issues due to oil presence, leading to decreased air throughput and increased pressure differences over time, and lack effective solutions for preventing oil leakage and moisture ingress across varying temperatures.
Innovation Solution
A pressure equalizing device featuring a gas-permeable membrane with fibers completely sheathed by an elastomer, such as a fluoroelastomer blend, which maintains high air permeability and oil-repellent properties, combined with a laminate barrier layer of nonwoven and expanded polytetrafluoroethylene (ePTFE) to prevent liquid penetration, ensuring consistent performance across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If porous PTFE membranes are used for pressure equalisation, then good pressure equalisation is achieved in the new condition, but the pores become clogged by oil over time leading to decreased air throughput
Solution Approach 1:
The invention uses a nonwoven material with controlled porosity (porosity between 30% and 80%) as the base membrane structure. This porous nonwoven material provides sufficient air throughput while the specific fiber structure and pore distribution prevent complete pore clogging by oil, maintaining performance over the service life.
Solution Approach 2:
The invention creates a composite membrane structure combining a nonwoven base material with a hydrophobic/oleophobic coating layer. This composite structure provides both the porosity needed for air throughput and the surface properties that prevent oil adhesion and pore clogging, resolving the contradiction between initial performance and long-term reliability.
2Object-generated harmful factors
If no pressure equalisation valves are used but ventilation ducts with labyrinth are used, then oil escape is prevented, but pressure equalisation effectiveness is reduced
Solution Approach 1:
The porous nonwoven membrane allows pressure equalisation through its controlled pore structure while the hydrophobic/oleophobic coating prevents oil passage. This eliminates the need for labyrinth structures that impede airflow, maintaining high pressure equalisation efficiency while preventing oil leakage.
Solution Approach 2:
The invention changes the surface energy parameters of the membrane material by applying a hydrophobic/oleophobic coating. This parameter change allows the membrane to differentiate between gas molecules (which pass through) and oil molecules (which are repelled), achieving both functions without mechanical labyrinths.
3Stress or pressure
If the membrane allows pressure equalisation between inside and outside, then mechanical load on housing is reduced, but moisture penetration from environment occurs
Solution Approach 1:
The hydrophobic/oleophobic coating changes the surface energy parameters of the membrane, creating a barrier that repels water and moisture while allowing gas permeability. This enables the membrane to maintain pressure equalisation function while preventing moisture ingress from the environment.
Solution Approach 2:
The controlled porosity of the nonwoven material (30%-80%) provides sufficient pathways for pressure equalisation while the hydrophobic coating on the pore surfaces prevents liquid moisture from penetrating through capillary action, allowing gas flow while blocking liquid moisture.
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 oil leakage and maintains excellent pressure equalization over a long service life, even at extreme temperatures, while ensuring reliable operation by retaining oil and preventing moisture ingress, thus avoiding mechanical stress and component failure.
Implementation Method 1
a gas-permeable membrane which comprises at least one nonwoven layer. The nonwoven layer comprises fibers which are substantially completely sheathed by a sheath of an elastomer
Implementation Method 2
fibers which are substantially completely sheathed by a sheath of an elastomer
Data Source
AI summary
A pressure equalising device for a housing, including an inside, an outside, and a lattice-like cage having a gas passage opening. The gas passage opening connects the inside and the outside in a differential pressure-dependent and flow-conducting manner. The gas passage opening is covered by a gas-permeable membrane which includes at least one nonwoven layer. The nonwoven layer includes fibers which are substantially completely sheathed by a sheath of an elastomer.