Compact 4-DOF Surgical Tool With Solid Cable Guide Channels
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Solution Overview
Problem
Miniaturization of surgical articulation mechanisms for applications in small body cavities, such as the infant oral cavity, is challenging due to the difficulty in designing 3-DOF wrist mechanisms smaller than 5 mm in diameter, where existing designs face issues with friction, cable wear, and space constraints, particularly with the use of pulleys which are hard to manufacture and increase mechanism length.
Innovation Solution
A compact surgical tool with a design that uses solid surface cable guide channels and a tensioning mechanism with movable pulleys and cam devices to maintain constant cable tension and reduce friction, allowing for smooth articulation and high dexterity within small spaces, while minimizing the number of components and eliminating the need for pulleys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pulleys are used to guide cables in wrist mechanisms, then cable friction is reduced and constant cable length is maintained, but the mechanism diameter increases and manufacturing difficulty increases
Solution Approach 1:
The patent extracts the cable guidance function from traditional pulley components and integrates it directly into the wrist mechanism structure. Solid surface channels are formed on the wrist links themselves, eliminating the need for separate pulley components while maintaining cable guidance functionality and reducing overall mechanism diameter.
Solution Approach 2:
The patent merges the cable guide channels directly into the wrist link structure. The channels are formed as integral features of the wrist links, combining the structural support function of the links with the cable guidance function, thereby eliminating separate pulley components and reducing mechanism complexity.
2Volume of moving object
If solid surface cable guide channels are used, then mechanism size is reduced and manufacturing is simplified, but cable friction increases and cable wear occurs
Solution Approach 1:
The patent applies local quality by creating smooth, polished surfaces specifically at the cable contact regions within the guide channels. The channels are designed with optimized curvature radii and surface finishes to minimize friction at critical cable contact points, while other portions of the mechanism can have different surface characteristics.
3Volume of moving object
If mechanism size is miniaturized below 5 mm diameter, then accessibility in small body cavities is improved, but manufacturing complexity increases and performance is compromised
Solution Approach 1:
The patent merges multiple functions into the wrist links themselves. The links provide structural support, contain integral cable guide channels, and serve as rotation joints. This consolidation eliminates the need for separate pulley components and simplifies manufacturing while maintaining the required 3-DOF functionality at reduced size.
Solution Approach 2:
The wrist links are designed as multi-functional components that simultaneously provide structural support, cable guidance through integral channels, and rotation joints. This universal design approach allows the mechanism to maintain full functionality while being manufactured as compact, integrated units suitable for small body cavity applications.
4Device complexity
If solid surface cable guide channels are used, then number of components is reduced, but cable tension control becomes difficult
Solution Approach 1:
The patent incorporates dynamic tensioning features that automatically adjust cable tension based on wrist position. The guide channels are designed with varying curvature radii that create natural tensioning effects during wrist rotation, and spring elements are integrated to maintain constant cable tension throughout the range of motion, compensating for changes in cable path length.
Data Source
AI summary
A surgical tool for compact articulating during surgical procedures includes a pitch cable, at least one yaw cable, a first link, a second link, at least one end-effector link, and at least one tensioning mechanism. The first link has a pitch joint end with a pitch joint pin and at least one yaw cable guide channel. The second link has a yaw joint end with a yaw joint pin. The second link is rotatably connected to the pitch joint pin. The at least one end-effector link is rotatably connected to said yaw joint pin. The yaw cables are coupled to the end-effector links such that the yaw cables can actuate the end-effector links about the yaw joint pin. The yaw cable guide channel is configured such that the yaw cables travel through a smooth trajectory to the end-effector links. The tensioning mechanism is configured to maintain a constant length.