Steerable Instrument Steering Wire Chain Link Segmentation
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Solution Overview
Problem
Steerable instruments for endoscopic and invasive applications face challenges in achieving a balance between strength and bending stiffness, particularly in the steering wires, which affects their maneuverability and tissue manipulation capabilities.
Innovation Solution
The implementation of steering wires in the form of strips cut from tubes, with flexible portions designed as shackled chain links, minimizes bending stiffness while maintaining strength. This design allows for improved flexibility and control in the deflectable distal end of the instrument.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If steering cables with sub 1 mm diameters are used as steering members, then the instrument can achieve steering capability, but the bending stiffness is excessive and maneuverability is reduced
Solution Approach 1:
The steering wire is segmented into multiple discrete elements (first steering element, second steering element, third steering element) arranged in parallel. This segmentation reduces the bending stiffness of individual elements while maintaining the overall structural integrity and steering capability through the collective arrangement of multiple elements.
Solution Approach 2:
The steering arrangement uses a composite structure combining multiple steering elements (cables or strips) made from different materials or with different properties, arranged in parallel within the intermediate cylindrical element. This composite approach allows optimization of the balance between strength and flexibility.
2Ease of operation
If the steering wire is made more flexible to improve maneuverability, then the bending stiffness decreases, but the strength and fatigue life are reduced
Solution Approach 1:
Dividing the steering wire into multiple segmented elements reduces stress concentration on any single element, distributing mechanical loads more evenly and improving fatigue life while maintaining flexibility.
Solution Approach 2:
The steering elements are designed with specific local properties (material selection, cross-sectional geometry) optimized for their function, allowing different parts of the steering system to have different characteristics suitable for their specific mechanical demands.
Data Source
AI summary
A steerable instrument has a tube (3) extending in a longitudinal direction. The steerable instrument has a proximal end and a deflectable distal end. The tube (3) has a steering wire (16(j); 120, 130) which is made from the tube (3), separated by a slotted structure from the remainder of the tube (3), attached to the deflectable distal end and is movable in a longitudinal direction of the tube (3) such as to deflect the deflectable distal end The steering wire (16(j); 120, 130) has flexible portion located in a flexible zone (13) of the steerable instrument which is implemented by a series of adjacent chain links (1301(k); 1401(k); 1501(k); 1601(k); 1701(k)).