Rotary Input Lever Gimbal for Minimally Invasive Surgical Tools
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Solution Overview
Problem
In minimally invasive surgeries, traditional force transmission methods using cables to control articulated sections within surgical instruments face challenges in efficiently transmitting bidirectional actuating forces through small, flexible elongate tubes, requiring multiple cables and complicating the manipulation of surgical tools with angular motion.
Innovation Solution
A force transmission mechanism utilizing three cables connected to a gimbal type articulated section, where two capstans drive cables connected to levers, with one cable shared between capstans and passing over a pulley, allows for efficient orientation of a mechanically actuated surgical tool without net movement of linkages relative to the gimbal plate's center, enabling bidirectional force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If cables are used to transmit actuating forces to articulated sections, then flexibility and force transmission capability are improved, but the number of cables required increases and system complexity increases
Solution Approach 1:
The patent combines multiple cable functions into a shared cable system. A single cable passes through multiple pulleys to connect to multiple levers, allowing one cable to perform the work of multiple separate cables while maintaining the ability to transmit bidirectional forces to the gimbal articulated section
Solution Approach 2:
The shared cable serves multiple functions simultaneously by routing through pulleys connected to different levers. This universal cable transmits forces to multiple articulated components, reducing the total cable count while maintaining full control capability over the gimbal's degrees of freedom
2Reliability
If multiple cables are used to control gimbal articulation, then bidirectional force transmission is achieved, but the manipulation precision and flexibility are reduced due to cable compliance
Solution Approach 1:
Pulleys are introduced as intermediary elements between the cables and levers. These pulleys reduce the impact of cable compliance by providing a mechanical advantage and more direct force transmission path, improving manipulation precision while maintaining bidirectional force capability
Solution Approach 2:
The patent employs curved cable paths through pulleys rather than straight-line connections. This curved routing optimizes the mechanical advantage and reduces the effective compliance impact, allowing more precise control of the gimbal articulation
3Ease of operation
If three cables are used to control a gimbal with two degrees of freedom, then complete force transmission is achieved, but the device complexity and space requirements increase
Solution Approach 1:
The patent merges the functions of three separate cables into a shared cable system that routes through pulleys. This consolidation reduces the space required for cable management while maintaining complete force transmission capability to all three gimbal control points
Solution Approach 2:
The cable routing is nested through the pulley system, with the single cable passing through multiple pulley stations in sequence. This nested arrangement compactly accommodates what would otherwise require three separate cable paths, reducing the overall volume requirements
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 mechanism effectively transmits forces to orient a surgical tool with two degrees of freedom, improving the flexibility and precision of surgical instrument manipulation within minimally invasive procedures by maintaining tension in all linkages and reducing the impact of cable compliance.
Implementation Method 1
Another cable is connected to both capstans and passes over a pulley rotatably coupled to the third lever
Data Source
AI summary
A force transmission transmits a force received by two rotational inputs to an output gimbal plate. Two capstans receive the rotational input. The capstans drive cables connected to three levers. A cable is connected directly from each of the capstans to one of two levers. Another cable is connected to both capstans and passes over a pulley rotatably coupled to the third lever. Each of three linkages has a first end coupled to one of the three levers and a second end coupled to the output gimbal plate. Rotation of each of the first and the second input capstans causes the three cables to move the three levers such that there is no net movement of the three seconds ends of the linkages with respect to the center of motion of the output gimbal plate. The output gimbal plate may orient a mechanically actuated surgical tool.