Variable Mechanical Advantage Cam Profile for Surgical Stapler Clamping
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Solution Overview
Problem
Current robotic surgical tools face challenges in efficiently actuating the closure mechanism of surgical staplers, particularly in managing the viscoelastic properties of tissue and ensuring proper staple formation.
Innovation Solution
The implementation of a gearing assembly with a closure cam gear and a profile that provides varying mechanical advantages, combined with pulsed closure control methods, allows for efficient jaw closure and staple formation by optimizing the clamping force and tissue compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a gearing assembly with closure cam gear and profile is used to provide varying mechanical advantages, then the precision and effectiveness of surgical stapling is enhanced through optimized clamping force, but the device complexity increases
Solution Approach 1:
The closure cam gear incorporates a variable profile that dynamically adjusts the mechanical advantage ratio during the jaw closure sequence. The profile transitions from a first arcuate region with a first mechanical advantage ratio to a second arcuate region with a second mechanical advantage ratio, enabling dynamic optimization of clamping force without requiring multiple discrete gears or complex control systems
Solution Approach 2:
The mechanical advantage ratio is changed as a function of the closure sequence progress. The cam profile geometry is specifically designed to provide a first mechanical advantage ratio during initial jaw closure and a second, different mechanical advantage ratio during final clamping, thereby changing the force transmission parameters to match tissue compression requirements at different stages
2Reliability
If pulsed closure control methods are implemented to optimize clamping force for thick or difficult tissues, then the reliability of staple formation is improved, but the duration of the closure action increases
Solution Approach 1:
The closure control system implements pulsed actuation patterns where the jaw closure is delivered in controlled pulses rather than continuous motion. This periodic action allows the tissue to settle and the viscoelastic properties to manifest, enabling reliable staple formation in thick or difficult tissues while maintaining efficient overall closure time through optimized pulse timing
3Force
If the mechanical advantage ratio is varied during the closure sequence to ensure adequate clamping force, then the force capability is improved, but the device complexity increases
Solution Approach 1:
The closure cam gear incorporates a variable profile that dynamically adjusts the mechanical advantage ratio during the jaw closure sequence. The profile transitions from a first arcuate region with a first mechanical advantage ratio to a second arcuate region with a second mechanical advantage ratio, enabling dynamic optimization of clamping force without requiring multiple discrete gears or complex control systems
Solution Approach 2:
The closure cam gear acts as an intermediary mechanical element between the actuator and the jaw closure mechanism. By embedding the variable mechanical advantage function within the cam profile geometry, the system achieves force optimization through a single passive mechanical component rather than requiring active control systems or multiple variable-ratio mechanisms
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 precision and effectiveness of surgical stapling by ensuring consistent and adequate clamping force, even with thick or difficult tissues, thereby improving staple formation and reducing the risk of tissue damage.
Implementation Method 1
a closure cam gear (725) having a profile (902) that provides a first mechanical advantage ratio (MA1) during a first portion of a jaw closure sequence and a second mechanical advantage ratio (MA2) during a second portion of the jaw closure sequence
Data Source
AI summary
A method of using a surgical tool includes operating at least one motor of a tool driver of the surgical tool and thereby closing first and second jaws of the surgical tool to clamp tissue disposed therebetween, recording a raw torque and a raw angular velocity corresponding to the at least one motor during closing of the first and second jaws, and correcting the raw torque to produce a corrected torque using the raw angular velocity and a dampening property of the tissue.