Multi-layer Tube with Reverse Necking for Medical Deployment
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Solution Overview
Problem
Tubular structures, such as those made from flexible plastic materials, exhibit 'necking' when elongated, making it difficult to remove them from mandrels or deploy medical devices without significant tension, which complicates device design and deployment.
Innovation Solution
A tubular structure constructed with multiple layers of material that move relative to each other during axial elongation, increasing in diameter as axial force is applied, allowing for easier removal and deployment with reduced tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a plastic tube is used to contain or constrain a device, then the tube can provide structural support and containment, but the tube will neck down when elongated making it difficult to remove from the mandrel or deploy the device
Solution Approach 1:
The tube is constructed with multiple layers of material wrapped at different angles (first wrap at first angle, second wrap at second angle), creating segmented structural elements that behave independently during elongation. This segmentation allows each layer to contribute differently to the overall mechanical properties, providing strength while enabling easy removal.
Solution Approach 2:
The tube is designed with specific wrap angles (first angle and second angle) that are different from each other. When axial force is applied, the relative angles between the wraps change, causing the tube to expand diametrically rather than neck down. This parameter change in the wrap configuration transforms the tube's response to tension from contraction to expansion.
2Stability of the object's composition
If thicker and/or stiffer materials are used to resist necking, then the tube can maintain its diameter during elongation, but the device profile increases and flexibility is reduced
Solution Approach 1:
The tube is constructed as a composite structure with multiple material layers wrapped at different angles. Each layer contributes different mechanical properties, creating a composite that maintains diameter stability during elongation while preserving flexibility. The combination of layers with different wrap angles creates a material structure that is both stable and flexible.
3Ease of operation
If everting sheaths are used to reduce tension during deployment, then the removal process is facilitated, but significant tension is still required due to friction between the sheath and deployment line
Solution Approach 1:
The invention converts the harmful effect of friction during sheath removal into a beneficial effect. By designing the tube with multiple wrapped layers at different angles, the friction that would normally cause necking and require high tension is transformed into a mechanism that causes the tube to expand diametrically during eversion, reducing the required tension and facilitating easier deployment.
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 tubular structure effectively avoids necking issues, enabling easier removal from mandrels and deployment of medical devices with a smaller, more flexible profile, reducing the required tension and improving accuracy during deployment.
Implementation Method 1
the tube will contract in diameter if the tube is elongated longitudinally. This property is commonly referred to as 'necking.'... a tubular structure constructed with multiple layers of material that move relative to each other during axial elongation, increasing in diameter as axial force is applied
Data Source
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AI summary
An improved tubular structure adapted to increase in diameter upon application of axial force is provided. Increase in diameter is achieved by constructing the tube from multiple layers of material that move relative to each other during axial elongation of the tube. The tube of the present invention can be used both to avoid problems in "necking" found in many prior tube devices, and to provide additional benefits that increases in diameter of the tube during axial elongation can provide. As such, the tube of the present invention may be useful as a manufacturing aid, as a deployment sheath (for example, to deliver medical devices), and in other applications that may benefit from easier tubular sheath removal.