Nested Pulley Wrist Mechanism for Surgical Tool Reliability
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Solution Overview
Problem
Robotic surgical tools face premature failure of elongated members due to high load demands and increased friction from pulley systems, which reduces their use life and efficiency.
Innovation Solution
The implementation of nested pulleys in the wrist mechanism of surgical tools, which reduces the load on elongated members while maintaining a low fleet angle, thereby minimizing friction and enhancing mechanical advantage without increasing the overall width of the wrist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mechanical advantage gained through the pulleys is increased to reduce cable wear, then cable wear is reduced, but the fleet angle increases which increases friction and lowers expected use life
Solution Approach 1:
The patent applies nesting by placing one pulley inside another concentric pulley assembly. The inner pulley has a smaller diameter than the outer pulley, allowing the cable to wrap around both pulleys in a nested configuration. This nested arrangement increases the effective mechanical advantage while keeping the cable's path relatively straight, thereby reducing friction and fleet angle compared to using a single larger pulley.
2Force
If a higher fleet angle is used to increase mechanical advantage, then mechanical advantage is increased, but friction on the cables increases and expected use life decreases
Solution Approach 1:
The nested concentric pulley arrangement allows the cable to wrap around multiple pulleys of different diameters in sequence. This configuration achieves the desired mechanical advantage through the combined effect of multiple pulleys rather than relying on a single pulley with a high fleet angle, thereby maintaining lower friction and higher reliability.
Solution Approach 2:
The patent segments the cable path into multiple wraps around different pulleys rather than a single wrap around one pulley. This segmentation of the mechanical advantage achievement into multiple smaller steps reduces the fleet angle at each individual pulley contact point, thereby reducing overall friction and cable wear.
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 significantly reduces the risk of premature failure of elongated members, allowing for a greater number of surgical procedures to be performed with the same tool by distributing the load effectively and minimizing friction.
Implementation Method 1
The routing of the cables around the pulleys creates a mechanical advantage and reduces cable friction when operating the tool
Implementation Method 2
The routing of the cables around the pulleys creates a mechanical advantage and reduces cable friction when operating the tool
Data Source
AI summary
Surgical tools that are capable of a higher mechanical advantage without increasing the overall width of the tool. The surgical tool includes a wrist that may comprise a first pulley adjacent to a second pulley, the first pulley may have a first lip and a second lip, and the second pulley may have a first lip and second lip. The first lip of the second pulley overlaps the second lip of the first pulley and at least a portion of the first lip of the second pulley is recessed within a body of the first pulley.