Cable Length Conserving Medical Instrument Wrist
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Solution Overview
Problem
Existing medical instruments face challenges in conserving cable length during the range of motion of a wrist joint, especially in compact designs where space limitations prevent the implementation of inherently length-conserving cable paths.
Innovation Solution
The implementation of a path-length adjusting drive mechanism in the backend of a medical instrument, which autonomously changes backend cable routings to compensate for distal path length changes, thereby conserving cable length throughout the instrument.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cables are routed through the wrist joint to enable multiple degrees of freedom, then the wrist can achieve complex motion, but the cable path length changes during actuation causing tension variations
Solution Approach 1:
The patent applies dynamics by making the cable routing path adjustable rather than fixed. The cable path lengthening mechanism dynamically adapts the cable route in response to wrist joint position changes, allowing the system to maintain optimal cable tension across multiple degrees of freedom while accommodating the complex motion requirements of the wrist
2Reliability
If cable paths are routed to minimize length change during actuation, then cable tension is maintained, but the device complexity increases
Solution Approach 1:
The patent introduces an intermediary mechanism - the cable path lengthening device - that mediates between the simple fixed routing and the complex dynamic adjustment needs. This intermediary component automatically compensates for cable length changes during wrist actuation, maintaining tension stability without requiring complex pre-planned routing geometries
3Volume of moving object
If the instrument is designed to be compact, then it is easier to insert through small incisions, but space limitations prevent implementation of inherently length-conserving cable paths
Solution Approach 1:
The patent applies nesting by placing the cable path lengthening mechanism within the compact instrument structure. The mechanism for adjusting cable path length is integrated into the existing instrument components, allowing space-efficient design that maintains cable length conservation capabilities despite the compact size required for minimally invasive insertion
Data Source
AI summary
An apparatus includes a wrist, an end effector, a cable pair, and a transmission. A proximal wrist portion is coupled to a distal end portion of a shaft. Actuation of the wrist moves a distal wrist portion relative to the proximal wrist portion. The end effector is coupled to the distal wrist portion, and can be actuated to move relative to the wrist. The transmission is coupled to a proximal end portion of the shaft, and can move an end of the cable pair to actuate the end effector. The end of the cable pair is routed through a transmission cable path within the transmission. The transmission includes an adjustment mechanism having an input portion that receives a force exerted by the end of the cable pair. The adjustment mechanism is configured to change a length of the transmission cable path in response to a change in the force.