Variable-Diameter Spool Control for Precise Stent Release
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Solution Overview
Problem
Existing stent delivery systems require complex handling during the release of stents, which can be cumbersome and difficult to control.
Innovation Solution
A stent delivery system with a handling device featuring a thumbwheel and a winding spool with varying winding diameters, allowing for different transmission ratios between the thumbwheel rotation and the proximal displacement of the outer sheath, enabling precise control over the release of stents through rough or fine displacement modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant winding diameter is used on the winding spool, then the structure is simple, but the control precision during stent release is insufficient
Solution Approach 1:
The winding spool is designed with varying winding diameters along its axial length, transforming it from a static uniform structure to a dynamic one that provides different transmission ratios at different positions. This allows the outer sheath to be retracted with different speeds and precisions depending on the displacement stage, improving control precision without requiring multiple separate spools
Solution Approach 2:
The winding diameter of the spool is varied as a parameter along its length, with the pull member engaging at different radial distances from the rotation axis at different displacement positions. This parameter change creates different mechanical advantage ratios, enabling fine control during critical phases of stent release while maintaining simplicity through a single continuous spool structure
2Ease of operation
If a single transmission ratio is used between thumbwheel rotation and outer sheath displacement, then the mechanism is simple, but the handling during stent release is cumbersome
Solution Approach 1:
The transmission mechanism transitions from a single fixed ratio to a dynamic variable ratio system through the varying diameter spool. As the outer sheath retracts and the pull member moves to different positions on the spool, the transmission ratio automatically changes, providing rough control for initial retraction and fine control for precise stent deployment, thereby improving ease of operation
Solution Approach 2:
The transmission ratio is changed as a variable parameter during operation rather than being fixed. By varying the spool diameter at different engagement positions, the system automatically adjusts the mechanical advantage throughout the retraction process, making the device easier to operate without requiring complex external control mechanisms
3Productivity
If the outer sheath is displaced rapidly, then the stent release is faster, but the control precision is reduced
Solution Approach 1:
The system dynamically adjusts the transmission ratio during the retraction process. In early stages where rapid displacement is needed, the pull member engages with larger diameter portions of the spool providing faster retraction. As the sheath approaches the final release position, the pull member transitions to smaller diameter portions, automatically reducing the transmission ratio for precise control, thus achieving both speed and precision
Solution Approach 2:
The transmission ratio parameter is varied continuously or in stages during the displacement process. By changing the effective spool diameter at different displacement positions, the system optimizes the balance between retraction speed and control precision, allowing rapid initial movement followed by precise final positioning for accurate stent 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
Simplifies and enhances the handling of stent release by allowing for controlled, precise deployment of stents based on varying geometric properties of the catheter arrangement, ensuring efficient and controlled stent expansion.
Implementation Method 1
different transmission ratios result between the rotation movement of the thumbwheel and the proximal displacing movement of the outer sheath
Data Source
AI summary
A stent delivery system includes a handling device having a housing, a thumbwheel rotatably mounted in the housing, and a winding spool rotatable with the thumbwheel. A catheter arrangement has an inner shaft with an end fixed on the housing, an outer sheath disposed coaxially to the inner shaft, and a stent received radially between the inner shaft and outer sheath. A flexible pull member engages a proximal end of the outer sheath and is held on the winding spool to be windable. For release of the stent, the outer sheath is displaceable relative to the inner shaft by winding the flexible pull member on the winding spool. The winding spool has different winding diameters on which the flexible pull member engages and is windable in different displacement positions of the outer sheath. Different transmission ratios result between rotation of the thumbwheel and movement of the outer sheath.