Rotational Drive Shaft with Heat Shrinkable Polymer for Torque Stability

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Solution Overview

Problem

Existing rotational atherectomy devices face issues with drive shaft deformation and loss of control during high-speed operations, particularly when encountering blocked or calcified lesions, leading to potential tool release and vascular trauma.

Innovation Solution

A rotational drive shaft with a heat shrinkable polymer layer covering the middle portion, forming undulations that provide radial compression and prevent longitudinal elongation or shortening, combined with an unconstrained proximal section for strain relief and 1:1 motion control, to maintain torque stability and prevent shaft fracture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the drive shaft is made flexible to navigate stenotic lesions, then the device can be placed within the artery, but the drive shaft may deform and lose control during high-speed operations

Engineering Contradiction:

Improveflexibility for navigating stenotic lesionsVSAvoidcontrol stability during high-speed operations

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The drive shaft is segmented into three distinct sections with different properties: a flexible distal section for navigating lesions, a constrained middle section with heat shrinkable polymer for stability, and an unconstrained proximal section for strain relief. This segmentation allows each section to perform its specific function optimally.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the drive shaft have different qualities: the distal section remains flexible for navigation, the middle section gains radial compression and longitudinal constraint through heat shrinkable polymer, and the proximal section remains unconstrained for strain relief. This local differentiation resolves the contradiction between overall flexibility and localized stability.

Inventive Principle:

Principle #3Local quality

2Reliability

If the drive shaft is constrained to prevent deformation, then control is maintained, but the shaft may fracture under torque stress

Engineering Contradiction:

Improvecontrol stabilityVSAvoidresistance to fracture under torque

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The drive shaft is divided into constrained and unconstrained sections. The middle section with heat shrinkable polymer provides longitudinal constraint for control, while the proximal unconstrained section absorbs torque stress and prevents fracture propagation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The unconstrained proximal section acts as a cushioning element that absorbs torque stress before it can propagate to the constrained middle section, preventing fracture under high torque conditions.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Stability of the object's composition

If heat shrinkable polymer layer is applied to the drive shaft, then longitudinal elongation is prevented, but the proximal section needs to remain unconstrained for strain relief

Engineering Contradiction:

Improvelongitudinal dimension stabilityVSAvoidpartial coverage application complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The heat shrinkable polymer layer is applied selectively to the middle section of the drive shaft, leaving the distal and proximal sections unconstrained. This local application provides longitudinal stability where needed while maintaining flexibility and strain relief capabilities where required.

Inventive Principle:

Principle #3Local quality

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 solution enhances torque stability, reduces the risk of drive shaft deformation and fracture, and maintains precise control during high-speed operations, minimizing vascular trauma and improving the effectiveness of atherectomy procedures.

Implementation Method 1

a heat shrinkable polymer layer covering at least a middle portion of the drive shaft

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS20240115289A1Rotational drive shafts and intravascular medical devices thereof

Publication Date: 2024.04.11 CARDIOVASCULAR SYSTEMS INC

AI summary

Devices and systems comprising a rotational drive shaft formed of wire filars or one or more coils for use in high-speed rotational medical procedures, e.g., atherectomy, are disclosed. Generally, a preferred embodiment of the drive shaft for transferring torque and activating rotation of a tool such as an abrasive element that is attached near a distal end of the drive shaft may be constructed with a heat shrinkable polymer layer covering at least a middle portion of the drive shaft, wherein a proximal-most portion of the drive shaft is not covered by the heat shrinkable polymer layer. In certain embodiments, the drive shaft may also comprise a distal portion that is not covered by the heat shrinkable layer, most preferably the distal end of the heat shrinkable layer in this embodiment is configured to remain within a delivery catheter or sheath during a medical procedure.