Nitinol Component Coupling by Interference Fit Without Heat
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Solution Overview
Problem
Existing methods for coupling nitinol components to dissimilar materials in medical devices face challenges due to the hard oxide layer of nitinol, which limits bonding and can deteriorate its thermal properties, often requiring filler materials that create weak points in the bond.
Innovation Solution
A method involving altering nitinol components by reducing their cross-sectional dimension, allowing them to fit into openings of dissimilar materials, and utilizing their shape recovery properties to securely couple without adhesives or heat exposure, using receivers with slots or openings to achieve an interference fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitinol components are coupled to dissimilar materials using traditional methods (adhesive bonding, welding, crimping, swaging), then coupling is achieved, but the hard oxide layer of nitinol limits bonding quality and may deteriorate thermal properties
Solution Approach 1:
The patent changes the physical state of the nitinol wire by transforming it from an annealed state to a work-hardened state through cold working. This parameter change in the material's mechanical properties enables the wire to be plastically deformed into crimp structures that mechanically interlock with dissimilar materials, achieving reliable coupling without adhesives or heat exposure that would compromise thermal properties
Solution Approach 2:
The patent creates dynamic coupling structures through crimping that allow for mechanical interlocking. The work-hardened nitinol wire can be deformed into crimp configurations that engage with the dissimilar material, providing a mechanical bond that maintains thermal properties while achieving reliable coupling
2Adaptability or versatility
If filler material is used to weld or solder nitinol to stainless steel, then coupling between dissimilar materials is achieved, but a weak point is created in the bond
Solution Approach 1:
The patent removes the need for filler materials by using work-hardened nitinol wire that can be directly crimped onto dissimilar materials. The cold-working process enables the nitinol to form mechanical interlocks without requiring intermediate filler materials, eliminating the weak points that would be created by such fillers while maintaining coupling capability between dissimilar materials
Solution Approach 2:
The patent replaces traditional thermal joining methods (welding, soldering) that require filler materials with a mechanical crimping system. The work-hardened nitinol wire is mechanically deformed to create interlocking crimp structures that directly engage with dissimilar materials, providing a reliable bond without the need for filler materials that would create weak points
3Strength
If nitinol wire is cold-worked to increase strength, then tensile strength and yield strength are improved, but ductility decreases
Solution Approach 1:
The patent deliberately changes the material parameters of the nitinol wire by cold-working it to achieve a work-hardened state. This parameter change increases tensile and yield strength while reducing ductility, but the reduced ductility is acceptable because the cold-worked wire is then formed into crimp structures that rely on elastic recovery rather than plastic deformation during operation
Solution Approach 2:
The patent performs preliminary cold-working and crimping operations during manufacturing to create the mechanical interlock structures. By pre-forming the crimp structures in the work-hardened state, the device achieves high strength coupling without requiring the nitinol to exhibit high ductility during device operation, thus resolving the contradiction between strength and ductility requirements
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 method enables robust and secure coupling of nitinol components to other materials without fillers or heat, maintaining the thermal properties of nitinol and ensuring a stable bond.
Implementation Method 1
stretching the wire so that a diameter of the wire is less than or equal to a width of the first opening
Implementation Method 2
allowing the second portions of the first medical device component to revert back to the natural state
Implementation Method 3
Nitinol has super-elastic properties that give it high flexibility, shape recoverability
Implementation Method 4
fitting a first portion of the first medical device component in the altered state into a first opening of the second medical device component
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 2D
AI summary
A method for coupling a first medical device component (100) to a second medical device (200) component comprising altering the first medical device component from a natural state to an altered state, by reducing a cross-sectional dimension of the first medical device, fitting a first portion of the first medical device component in the altered state into a first opening of the second medical device component, wherein the first medical device component includes second portions not within the first opening of the second medical device component, and allowing the second portions of the first medical device component to revert back to the natural state.