Double Universal Joint Wrist for Torque-Transmitting Surgical Tools
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Solution Overview
Problem
Existing minimally invasive surgical tools face challenges in transmitting desired torques and forces across compact articulated wrists, limiting their effectiveness in telesurgical tasks due to lack of natural wrist movement and precision.
Innovation Solution
A two-degree-of-freedom wrist mechanism is introduced, featuring an intermediate wrist member pivotally coupled with the instrument shaft and an end effector body, allowing for rotation about two transverse axes, along with internal passages to guide control cables and prevent tension alterations, enabling smooth and responsive articulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact articulated wrist is used in surgical tools, then the tool can access confined body spaces, but the transmission of torque and force is limited
Solution Approach 1:
The wrist mechanism is divided into multiple universal joints (first and second universal joints) with distinct axes of rotation. Each joint handles specific rotational movements, allowing the compact structure to transmit torque effectively through segmented functional components rather than a single integrated joint.
Solution Approach 2:
A coupling member is introduced as an intermediary component between drive shafts and driven shafts. This coupling member includes slots that receive protrusions from the shafts, enabling reliable torque transmission while accommodating the angular variations inherent in articulated wrist movements.
2Adaptability or versatility
If the wrist mechanism operates through a wide range of angles, then maneuverability is enhanced, but torque transmission reliability deteriorates
Solution Approach 1:
The wrist mechanism is designed to dynamically adapt its configuration through the coordinated operation of two universal joints with perpendicular axes. As the wrist articulates through wide angles, the joints automatically adjust their relative orientations, maintaining effective torque transmission paths throughout the full range of motion rather than being optimized for a single fixed angle.
Solution Approach 2:
The coupling member with protrusion-reception slots acts as a dynamic intermediary that maintains mechanical connection reliability across varying angles. The slots accommodate the angular displacement of protrusions from drive and driven shafts, ensuring continuous torque transmission even when the wrist articulates through extreme ranges of motion.
3Length of moving object
If the instrument shaft is made shorter for minimally invasive access, then patient recovery is improved, but the ability to transmit force to the end effector is reduced
Solution Approach 1:
The force transmission path is segmented into multiple stages through the first and second universal joints and coupling members. Each segment contributes to the overall torque transmission, allowing the short instrument shaft to effectively deliver force to the end effector by distributing the mechanical advantage across multiple joint interfaces rather than relying on a single long shaft.
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 enhances the maneuverability and force application of surgical tools, mimicking natural wrist movement, improving access and visibility in confined body spaces while maintaining reliable torque transmission across a wide range of angles.
Implementation Method 1
a first universal joint (254, 256) between the drive shaft (252) and the coupling member (258) so that the outer surface (260) interfaces with the first universal joint (254, 256)
Implementation Method 2
a second universal joint (262, 264) between the coupling member (258) and the driven shaft (266) so that the outer surface (260) interfaces with the second universal joint (262, 264)
Data Source
AI summary
Surgical tools having a two degree-of-freedom wrist, wrist articulation by linked tension members, mechanisms for transmitting torque through an angle, and minimally invasive surgical tools incorporating these features are disclosed. An elongate intermediate wrist member is pivotally coupled with a distal end of an instrument shaft so as to rotate about a first axis transverse to the shaft, and an end effector body is pivotally coupled with the intermediate member so as to rotate about a second axis that is transverse to the first axis. Linked tension members interact with attachment features to articulate the wrist. A torque-transmitting mechanism includes a coupling member, coupling pins, a drive shaft, and a driven shaft. The drive shaft is coupled with the driven shaft so as to control the relative orientations of the drive shaft, the coupling member, and the driven shaft.