Press-Fit Stud Assembly for High-Current Electrical Connections
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Solution Overview
Problem
Existing stud assemblies used in electrical devices, such as fuse assemblies and switches, face disconnection issues when high currents are applied, limiting their current rating to around 250 Amps due to brazing methods, which are not suitable for higher amperage.
Innovation Solution
A stud assembly comprising a stud with a cylindrical cavity, a sphere, and a bi-metallic rivet with a neck and pad, where the sphere is inserted into the stud cavity followed by the rivet, which is press-fit to deform against the sphere, creating a permanent attachment without brazing, allowing for higher current conductivity up to 500 Amps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brazing is used to attach the rivet to the stud, then the assembly can be manufactured with conventional processes, but the current rating is limited to around 250 Amps due to disconnection issues at high currents
Solution Approach 1:
The patent replaces the thermal brazing process with a mechanical press-fit process. The rivet is inserted into the stud cavity and press-fit until it deforms against the sphere, creating a permanent mechanical attachment. This mechanical system eliminates the disconnection issues that occur with brazing at high currents while maintaining ease of manufacture through conventional pressing equipment.
Solution Approach 2:
The patent uses a bi-metallic rivet with a neck made of a first metal and a pad made of a second metal. The neck material is selected to be deformable against the sphere during press-fit, while the pad material provides electrical conductivity and structural support. This composite material approach enables the rivet to achieve both mechanical attachment and electrical conductivity suitable for high current applications.
2Reliability
If brazing is used to secure the stud to internal circuitry, then the assembly can be manufactured using conventional techniques, but the current rating remains limited due to disconnection at very high currents
Solution Approach 1:
The patent replaces the slow thermal brazing process with a rapid mechanical press-fit operation. The rivet is simply inserted and pressed into the stud cavity until it deforms against the sphere, creating an immediate permanent attachment. This eliminates the heating, cooling, and quality control steps required for brazing, significantly increasing manufacturing productivity while ensuring connection stability at high currents.
3Reliability
If a simple rivet without a sphere is used in the stud cavity, then the manufacturing process is simpler, but the rivet can be pulled out and does not create a permanent attachment
Solution Approach 1:
The patent introduces a sphere as an intermediary element between the rivet and the stud cavity walls. The sphere has a diameter slightly larger than the cavity diameter, creating interference fit conditions. When the rivet is press-fit, the neck deforms against the sphere, which transfers and distributes the mechanical stress, creating a permanent attachment that prevents pull-out while maintaining a relatively simple overall assembly structure.
Solution Approach 2:
The patent uses a spherical geometry for the intermediary element. The sphere's curved surface provides optimal contact with the rivet neck during press-fit, distributing forces evenly and preventing stress concentration points. This spherical shape is more effective than flat or angular geometries for creating a secure interference fit while maintaining manufacturing simplicity.
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 assembly withstands currents up to 500 Amps without disconnection, is faster to manufacture, and costs less than brazed assemblies, with potential for up to 2000 Amps for short durations, and maintains electrical conductivity.
Implementation Method 1
the pad of the rivet is press-fit until the neck partially deforms against the sphere inside the cylindrical cavity
Implementation Method 2
The rivet is bi-metallic, with the neck made of a first metal and the pad made of a second metal
Data Source
Figure 1A~1B
Figure 2
Figure 3A
AI summary
A stud assembly is assembled by inserting a sphere into a cavity of a stud, where the cavity is cylindrical in shape, inserting a neck of a rivet into the cavity until the neck touches the sphere, and press-fitting the rivet into the cavity until the neck melds with the sphere.