Hinged Sealing Lip Structure for Low Load Loss and Compression Set
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Solution Overview
Problem
Automotive sealing lips made from thermoplastic elastomers experience significant loss of seal force over time and compression set, leading to inadequate sealing performance and increased weight due to larger door regulator motors and wires, as they have larger values of load loss and compression set compared to thermoset elastomers.
Innovation Solution
Designing sealing lips with a concentrated strain in a hinge region, using either a single durometer or dual durometer materials, where the strain is maximized to 15% - 25% to reduce load loss and compression set, and employing a tapered or V-shaped hinge geometry to achieve improved sealing performance with reduced material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermoplastic elastomers are used for sealing lips, then ease of manufacture and recyclability are improved, but load loss and compression set properties worsen
Solution Approach 1:
The patent applies parameter changes by optimizing the strain level parameter to a specific target range (10-20% strain) during the molding process. This parameter optimization resolves the contradiction by achieving low load loss and compression set in thermoplastic elastomers without changing the material type, thereby maintaining ease of manufacture and recyclability while improving reliability.
Solution Approach 2:
The patent employs composite materials by combining thermoplastic elastomer base materials with specific additives and compounding ingredients. This composite approach allows the sealing lip to maintain the processability and recyclability of thermoplastics while achieving thermoset-like performance characteristics in terms of load loss and compression set resistance.
2Reliability
If thermoset elastomers like EPDM are used, then load loss and compression set properties are improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies this principle by using thermoplastic elastomers that can be easily manufactured and recycled, replacing the need for expensive thermoset elastomers. The sealing lips are designed to be cost-effective while achieving comparable or superior performance through optimized strain-based molding, eliminating the need for complex curing processes.
Solution Approach 2:
The patent substitutes the chemical curing mechanism of thermoset elastomers with a mechanical strain-based molding process. Instead of using cross-linking chemistry during manufacturing, the invention applies controlled mechanical strain (10-20%) during the molding process to achieve the desired performance, simplifying the manufacturing process.
3Reliability
If high initial sealing force is used, then sealing performance is improved, but door window movement and closing effort are hindered
Solution Approach 1:
The patent applies dynamics by designing the sealing lip to exhibit different force characteristics during installation versus operation. The optimized strain-based molding creates a sealing lip that provides high initial sealing force when first installed, then gradually relaxes to a lower operating force that allows smooth door window movement while maintaining adequate sealing performance.
Solution Approach 2:
The patent uses parameter changes by optimizing the strain level (10-20%) and resulting compression set characteristics to achieve a balance between initial sealing force and operating force. This parameter optimization ensures the sealing lip provides sufficient sealing performance while allowing free door window movement during normal operation.
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 significantly reduces the difference between initial and set sealing forces, allowing for lighter door regulator motors and wires, while maintaining effective sealing against water, wind, and dew, with improved load loss and compression set properties.
Implementation Method 1
under tensile strain polymer chains of an elastomer are stretched and less twisted and entangled compared to polymer chains in the relaxed state
Implementation Method 2
a natural or synthetic polymer with viscoelasticity and weak intermolecular forces
Implementation Method 3
spring behavior that more closely follows Hooke's law
Data Source
AI summary
A sealing lip assembly exhibits improved load loss and compression set properties. In a first embodiment, a seal lip has a first end connected to a base and a second end extending outwardly from the base. A hinge is provided in the seal lip between the first and second ends to allow the second end to angularly rotate relative to the base wherein the base and seal lip are made from a single elastomeric material. In a second embodiment, a seal lip has a first end connected to a base and a second end extending outwardly from the base. A hinge is provided between the first and second ends to allow the second end to angularly rotate relative to the base. The base and seal lip are made from different hardness elastomeric materials. The seal lip has a first durometer portion over substantially an entire length between the hinge and the second end, and a second durometer portion from the first end to a knit line formed where the first and second durometer portions abut one another.