Angled Instrument Shaft Roll Actuator for Converging Surgical Tools
Solution Overview
Problem
In teleoperated minimally invasive surgeries, existing force transmission systems for rotating elongate surgical tubes are limited by the bulk of actuators, making it difficult to converge multiple surgical tools at a surgical site due to the inability of the proximal ends of the tubes to converge.
Innovation Solution
A force transmission system utilizing an input axle with a tapered input capstan and an output capstan, where a cable couples the rotation of the input capstan to the output capstan, maintaining a substantially constant overall path length throughout the range of motion by adjusting the capstan diameters to compensate for changing cable takeoff points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If actuators are positioned at the proximal end of elongate tubes to provide mechanical actuation, then improved control of surgical instruments is achieved, but the bulk of actuators prevents the proximal ends of tubes from converging at the surgical site
Solution Approach 1:
The patent introduces an angled transmission mechanism where the output shaft is positioned at an angle (e.g., 5 degrees) relative to the input shaft. This angular offset allows the elongate tubes to converge at the distal surgical site while the actuators remain separated at the proximal end, effectively using spatial dimensionality to resolve the contradiction between control capability and device bulk.
Solution Approach 2:
The patent employs a cable transmission system as an intermediary between the actuators and the elongate tubes. The cable runs through a guide structure that includes the angled input and output shafts, acting as a mediator that transfers rotational motion while accommodating the angular misalignment and enabling tube convergence without requiring the actuators to be positioned at the convergence point.
2Ease of operation
If the elongate tube is rotated to control the orientation of the surgical tool, then the surgical tool can be oriented correctly at the surgical site, but the cable takeoff points on the capstans change position causing variable cable path lengths and tension issues
Solution Approach 1:
The patent applies a tapered geometry to the capstans, where the diameter varies along the length of the capstan. This parameter change in the capstan geometry compensates for the changing cable takeoff positions during rotation, maintaining a substantially constant cable path length and consistent cable tension throughout the range of motion, thereby resolving the reliability issue.
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 allows for efficient transmission of actuating forces to rotate elongate tubes at an angle to the actuators, enabling multiple surgical tools to converge at a surgical site without compromising cable tension, thus improving the maneuverability and effectiveness of surgical instruments.
Implementation Method 1
At least one of the input capstan and the output capstan is tapered such that the overall path length of the cable remains substantially the same throughout the range of motion of the capstans
Data Source
AI summary
A force transmission includes an input axle having an input axis of rotation that receives a rotational input. An input capstan is fixed to the input axle. An output capstan is fixed to a main tube bushing. The output capstan and main tube bushing have an output axis of rotation that is at an angle to the input axis of rotation. A cable couples the rotation of the input capstan to rotate the output capstan and the main tube bushing. At least one of the input capstan and the output capstan is tapered such that the overall path length of the cable remains substantially the same throughout the range of motion of the capstans.