Nitinol Tube Lobe Joining Without Welding
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Solution Overview
Problem
The challenge lies in effectively joining Nickel Titanium (Nitinol) tubes to other tubular components without welding, as Nitinol's unique properties make welding with other metals problematic and costly, especially for complex product forms like tubing.
Innovation Solution
A mechanical joining method using complementary lobe features on Nitinol and other metallic tubes, allowing for interpenetration through translation, rotation, or hinging motions to form a snap-fit joint, eliminating the need for intermediate components and welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding is used to join Nitinol tube to stainless steel tube, then the tubes can be connected, but the process becomes complex and costly due to need for intermediate components and specialized welding procedures
Solution Approach 1:
The patent uses a mechanical intermediary structure (lobes with complementary geometry) to mediate the connection between Nitinol and stainless steel tubes, avoiding direct welding while achieving reliable mechanical joining through interlocking features
Solution Approach 2:
The patent replaces the welding process (thermal/chemical joining) with a mechanical joining system using interlocking lobe features, eliminating the need for specialized welding procedures and intermediate metal components
2Reliability
If welding with intermediate metal component is used, then reliable joint is achieved, but additional cost and lead time are incurred
Solution Approach 1:
The mechanical lobe structure serves as an intermediary that enables direct joining between dissimilar metals without requiring intermediate metal components, reducing material costs while maintaining joint reliability
Solution Approach 2:
The patent extracts and eliminates the intermediate metal component from the joining system, using only the tube materials themselves to form the connection, thereby reducing material quantity and cost
3Reliability
If welding procedure is used to join Nitinol to other metals, then connection is achieved, but the process time increases
Solution Approach 1:
The patent substitutes the time-consuming welding process with a rapid mechanical insertion process where lobes are simply pushed together to engage, dramatically reducing joining time while maintaining reliable connections
4Adaptability or versatility
If Nitinol is used throughout the entire drive tube, then flexibility is provided, but the cost increases significantly
Solution Approach 1:
The patent segments the drive tube into different material sections, using Nitinol only where flexibility is needed and joining it to lower-cost stainless steel for the remaining length, optimizing both performance and cost
Solution Approach 2:
The patent applies different material qualities to different locations along the drive tube, using expensive Nitinol locally where flexibility is required and cheaper stainless steel where structural support is sufficient
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 provides a cost-effective, self-aligning joint with torsional flexibility and strength, utilizing Nitinol's superelasticity to form a reliable connection without additional materials or complex processes, suitable for medical device applications.
Implementation Method 1
Nitinol is an alloy of approximately 50% Nickel and 50% Titanium. The difference of electronegativity between the two elements (Ni=1.9 and Ti=1.54 Pauling electronegativity) is large enough that they violate the Hume Rothery solubility criteria and combine when melted and cooled to room temperature as a NiTi body centered cubic intermetallic compound in which every nickel atom is surrounded by a titanium atom and visa versa. This gives the material unusual mechanical behaviors, including what is referred to as superelasticity.
Data Source
AI summary
The present invention relates to mechanical joining of Nickel Titanium tubes, also known as Nitinol, to other tubular components. Such mechanical joining may be achieved by interpenetration of lobe features between the respective tubes by translating the tubes together on a longitudinal axis, a transverse axis, by a combination of translation and rotational motion or by a hinging motion. The Nitinol superelasticity is used to accommodate the lobe deformation required for assembly and to snap the lobe back into its original shape to complete the mechanical joint.