Medical Manipulator Bending Mechanism for Axial Stress Control
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Solution Overview
Problem
Existing medical manipulators face challenges in managing stress and axial forces at varying pivot angles, leading to potential damage and increased cross-sectional dimensions due to excessive forces on the flexion joint components.
Innovation Solution
A bending mechanism with a stress adjustment system that includes a movable member and a biasing member, allowing the first and second transmission members to move relative to each other in the longitudinal axis direction to prevent excessive stress, using torsion coil springs with adjustable rigidity based on pivot angle, thereby maintaining permissible axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cross-sectional dimensions of the insertion part are increased to withstand excessive axial forces, then the strength and reliability improve, but the ease of insertion and miniaturization deteriorate
Solution Approach 1:
The link is designed to dynamically adjust its stress characteristics based on the pivot angle. As the pivot angle changes, the link's internal stress distribution changes automatically, allowing it to withstand varying axial forces without requiring a consistently large cross-section throughout the entire range of motion
Solution Approach 2:
The stress threshold parameter of the link is made variable through the adjuster mechanism. By changing the stress characteristics of the link according to the pivot angle, the system can maintain adequate strength at each position without oversizing the insertion part for the maximum stress condition
2Device complexity
If the stress in the link is allowed to exceed the threshold at extreme pivot angles, then the device complexity is reduced, but the reliability and safety deteriorate
Solution Approach 1:
The link incorporates an built-in adjuster mechanism that automatically regulates its own stress levels based on the pivot angle. This self-regulating capability ensures reliability without requiring external control systems or complex additional components
Solution Approach 2:
The adjuster mechanism is designed to prevent excessive stress from occurring in the first place by automatically adjusting the link's stress characteristics before the threshold is exceeded. This proactive stress management protects against potential damage without requiring complex real-time monitoring and intervention systems
3Device complexity
If a fixed stress threshold is applied to the link throughout the entire pivot range, then the device complexity is reduced, but the productivity and operational flexibility deteriorate
Solution Approach 1:
The link's stress threshold is made dynamic rather than fixed, automatically adapting to the pivot angle. This enables the system to operate efficiently across the full range of motion without compromising safety, as the stress characteristics are optimized for each specific angular position
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
This solution effectively manages stress at each pivoting position, preventing excessive axial forces and reducing the need for increased cross-sectional dimensions, allowing for a smaller insertion part diameter while ensuring the medical manipulator operates safely and efficiently.
Implementation Method 1
an adjuster that adjusts a stress occurring in the link so as not to exceed a predetermined threshold, at each pivoting position of the pivoting member with respect to the support member... and a spring that biases the movable member in such a direction as to prevent the movement of the movable member
Data Source
AI summary
A bending mechanism includes: a support member; a pivoting member supported at a distal end of the support member to be pivotable about an axis intersecting the longitudinal axis of the support member; a link disposed along the longitudinal axis and transmitting a force applied at a proximal end thereof to cause the pivoting member to pivot; and an adjuster adjusting stresses in the link so as not to exceed a threshold, at each pivoting position of the pivoting member with respect to the support member. The link includes a first member connected to the pivoting member and a second member disposed closer to the proximal end than the first member is. The adjuster includes a movable member moving in predetermined direction when the first and second members are relatively moved, and a spring biasing the movable member in such direction as to prevent the movement of the movable member.