Surgical Tool End Effector Redirect Pulleys
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Solution Overview
Problem
Cable-driven minimally invasive surgical (MIS) instruments face challenges with high strain and reduced mechanical advantage due to the incorporation of small pulleys with large fleet angles in their wrist architecture.
Innovation Solution
The implementation of redirect pulleys between the yaw and pitch pulleys in the wrist architecture of MIS instruments eliminates fleet angle, thereby reducing strain and enhancing mechanical advantage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If small pulleys with large fleet angles are incorporated in the wrist architecture, then the device can achieve compact design and reduced cable tension, but the mechanical advantage is reduced and strain increases
Solution Approach 1:
The patent introduces redirect pulleys as intermediary components between the yaw and pitch pulleys. These redirect pulleys mediate the cable path to eliminate fleet angle while maintaining the compact wrist architecture. The redirect pulleys act as intermediaries that transform the cable direction without requiring larger pulleys, thus preserving both compactness and mechanical advantage.
Solution Approach 2:
The patent applies dimensional change by routing cables through multiple pulleys in different spatial planes. The redirect pulleys are positioned at specific locations where they redirect cables from one plane to another, eliminating fleet angle through three-dimensional cable routing rather than simply increasing pulley size in a single plane.
2Device complexity
If small pulleys with large fleet angles are used, then the wrist architecture can be simplified, but cable wear increases and tool useful life decreases
Solution Approach 1:
The redirect pulleys serve as intermediary components that protect the cable path from harmful fleet angle. By positioning these pulleys strategically, the patent eliminates direct cable-to-pulley angle stress while maintaining a relatively simple wrist architecture, thus extending tool useful life without significantly complicating the design.
Solution Approach 2:
The patent converts the potentially harmful fleet angle into a beneficial cable routing path. By using redirect pulleys, the cable path that would normally create harmful angles is transformed into a series of gentle redirects, turning what would be cable wear into an optimized cable management solution.
3Device complexity
If fleet angle is present in the cable path, then the cable driven system can be more straightforward, but strain on the cable and pulleys increases
Solution Approach 1:
The redirect pulleys act as intermediaries that reduce cable strain by eliminating fleet angle. These pulleys are positioned to create gradual cable redirects rather than sharp angles, distributing the mechanical load more evenly along the cable path while maintaining relative simplicity in the overall cable driven system.
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 configuration reduces or eliminates fleet angle, leading to decreased cable wear, improved mechanical advantage, and extended tool useful life, ultimately enhancing the performance and reliability of MIS instruments.
Implementation Method 1
first and second redirect pulleys rotatably mounted to the distal clevis and axially interposing the pulleys and the jaws. A first closure cable extends through the pulleys to the first redirect pulley, which redirects the first closure cable with no fleet angle to the first jaw
Data Source
AI summary
A surgical tool includes a shaft extending from a drive housing, an end effector including opposing jaws, and a wrist interposing the shaft and the end effector and including a distal clevis to which the jaws are rotatably mounted at a first axle, a proximal clevis rotatably mounted to the distal clevis at a second axle and operatively coupled to the shaft, a set of pulleys rotatably mounted to the second axle, and first and second redirect pulleys rotatably mounted to the distal clevis and axially interposing the pulleys and the jaws. A first closure cable extends through the pulleys to the first redirect pulley, which redirects the first closure cable with no fleet angle to the first jaw, and a second closure cable extends through the pulleys to the second redirect pulley, which redirects the second closure cable with no fleet angle to the second jaw.