Shielded Cable Assembly Dual Ferrule Terminal Design
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Solution Overview
Problem
Existing shielded electric cable assemblies face challenges in effectively managing electromagnetic interference (EMI) and securing connections due to limitations in the design of shield terminals and inner terminals, particularly in maintaining a secure grip on the conductive core and insulation jackets.
Innovation Solution
The shielded electric cable assembly employs an inner ferrule made of a softer material and an outer ferrule made of a harder material, positioned coaxially to securely trap the conductive layer between them, with the outer ferrule crimped to interlock with the inner ferrule, ensuring a tight grip on both the insulation jacket and the conductive layer, enhancing EMI shielding and connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single ferrule is used to grip the insulation jacket and conductive layer, then the structure is simple, but the grip reliability and EMI shielding effectiveness are insufficient
Solution Approach 1:
The shield terminal is divided into two separate ferrules: an inner ferrule that grips the insulation jacket and an outer ferrule that grips the conductive layer. This segmentation allows each ferrule to be optimized for its specific function, improving overall grip reliability while maintaining reasonable structural complexity
Solution Approach 2:
The inner ferrule is positioned inside the outer ferrule, creating a nested configuration. The inner ferrule grips the insulation jacket while the outer ferrule grips the conductive layer, with both ferrules working together to provide reliable mechanical attachment and effective EMI shielding
2Strength
If a harder material is used for the ferrule, then the structural strength is improved, but the grip on the softer insulation jacket deteriorates
Solution Approach 1:
The inner ferrule is made of a softer material specifically optimized for gripping the insulation jacket, while the outer ferrule is made of a harder material optimized for gripping the conductive layer. Each ferrule's material properties are locally optimized for its specific function rather than using a uniform material throughout
Solution Approach 2:
The shield terminal uses composite material construction with the inner ferrule made of a softer conductive material and the outer ferrule made of a harder conductive material. This composite approach allows each ferrule to have material properties optimized for its specific gripping function while maintaining overall structural integrity
3Reliability
If the conductive layer is not securely trapped, then the assembly process is simple, but the EMI shielding effectiveness deteriorates
Solution Approach 1:
The outer ferrule is designed with a crimpable structure that dynamically transitions from a larger diameter to a smaller diameter during assembly. This dynamic deformation allows the outer ferrule to securely trap the conductive layer between itself and the inner ferrule, ensuring effective EMI shielding while maintaining a relatively simple assembly process
Solution Approach 2:
The outer ferrule's diameter parameter is changed during the crimping process, transitioning from a larger initial diameter to a smaller final diameter. This parameter change enables the outer ferrule to tightly secure the conductive layer, improving EMI shielding effectiveness without requiring complex pre-assembly structures
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
This configuration effectively shields against EMI and provides a secure, reliable electrical connection by ensuring a tight interlock between the ferrules and the conductive layer, improving the overall performance of the shielded cable assembly.
Implementation Method 1
The inner ferrule grips the inner insulation jacket frictionally
Implementation Method 2
The outer ferrule is crimped about the end portion of the conductive layer so that the inner ferrule grips the inner insulation jacket frictionally and outer ferrule is interlocked axially with the inner ferrule
Data Source
Figure 1~3
Figure 4~8
AI summary
A shielded electric cable assembly comprises a shielded electric cable and a shield terminal. The shield terminal comprises an inner ferrule and an outer ferrule. The inner ferrule is disposed between an inner insulation jacket of shielded electric cable and an exposed end portion of a conductive layer surrounding the inner insulation jacket. The outer ferrule is crimped about the exposed end portion of the woven metal shield to clamp exposed end portion of the conductive layer between the inner ferrule and the outer ferrule. The material of the outer ferrule is harder than the material of the inner ferrule so that crimped outer ferrule interlocks with the inner ferrule in the longitudinal direction.