Medical Device Drive Shaft Composite Coil Torsional Rigidity
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Solution Overview
Problem
Existing medical devices face challenges in maintaining structural integrity and preventing plastic deformation under strong torque loads during the treatment of stenosed blood vessels due to plaque or calcification, particularly in bifurcations, where traditional single-layer coil drive shafts fail to provide adequate torsional rigidity.
Innovation Solution
A medical device featuring a drive shaft with an inner coil and an outer coil, where the inner coil is wound in the direction of rotation and the outer coil is wound opposite to the rotation, with a wire ratio that balances the contraction and expansion powers to enhance torsional rigidity and prevent plastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer coil is used for the drive shaft, then the device complexity is reduced, but the torsional rigidity and resistance to plastic deformation under strong torque are insufficient
Solution Approach 1:
The drive shaft uses a composite coil structure consisting of an inner coil and an outer coil with different winding directions. The inner coil is wound in the rotation direction while the outer coil is wound opposite to the rotation direction, creating a composite structure that balances expansion and contraction forces to resist plastic deformation under torque
Solution Approach 2:
The drive shaft is segmented into multiple functional layers with the inner coil and outer coil serving distinct purposes. The inner coil (fewer wires) provides expansion power while the outer coil (more wires) provides contraction power, allowing each segment to contribute differently to the overall torsional performance
2Ease of manufacture
If the number of wires in inner and outer coils are equal, then the structure is symmetric and easy to manufacture, but the balance between expansion and contraction power is poor leading to plastic deformation
Solution Approach 1:
The coil structure deliberately uses asymmetric wire distribution where the outer coil has more wires than the inner coil. This asymmetric configuration creates a balanced force system where the contraction power of the outer coil (more wires) counteracts the expansion power of the inner coil (fewer wires), preventing plastic deformation while maintaining manufacturing feasibility
Solution Approach 2:
The invention changes the critical parameter of wire number distribution between coils. By setting the outer coil wire number greater than the inner coil wire number, the system achieves optimal balance between expansion and contraction forces, transforming the force equilibrium state to prevent plastic deformation under operational torque
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 device effectively maintains structural integrity and suppresses plastic deformation under strong torque, ensuring smooth rotation and high torsional rigidity, even in bent lesions, thereby effectively treating stenosed areas without compromising the drive shaft's structure.
Implementation Method 1
the wires of the inner coil are wound in the direction of rotation in the distal direction as viewed from the proximal side, the wires of the outer coil are wound in a direction opposite to the predetermined direction of rotation in the distal direction as viewed from the proximal side
Implementation Method 2
a balance between power of the outer coil to contract and power of the inner coil to expand is improved, and the torsional rigidity of the drive shaft can be improved
Data Source
AI summary
A medical device insertable into a living body lumen includes a drive shaft that rotates in a predetermined direction of rotation in response to a proximal side driving force to transmit a rotational force in a distal direction. The drive shaft includes: an inner coil of plural wires wound side-by-side in a circumferential direction of the drive shaft; and an outer coil of plural wires wound side-by-side in the circumferential direction of the drive shaft and surrounding the inner coil. The inner coil wires are wound in the predetermined direction of rotation in the distal direction as viewed from the proximal side, and the outer coil wires are wound in a direction opposite the predetermined direction of rotation n the distal direction as viewed from the proximal side. The number of wires constituting the inner coil is smaller than the number of wires constituting the outer coil.