Laparoscopy Forceps Pantograph Links Rectangular Cross-Section
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Solution Overview
Problem
Laparoscopy forceps with existing designs face issues of increased size leading to poor guidance and accuracy, and susceptibility to breakage under force, due to oversized yokes and links, which affects the reliability and precision of minimally-invasive surgical procedures.
Innovation Solution
The design features a yoke with a constant outside diameter, identical rectangular links with chamfered ends, and a pantograph mechanism where the distance between pivot axes is optimized to ensure the forceps fit within a narrow guide tube while maintaining strength, with the links and cams securely connected to prevent breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the yoke and links are made larger to increase strength, then the forceps can withstand larger forces without breakage, but the overall size increases causing poor guidance and reduced accuracy in the guide tube
Solution Approach 1:
The patent applies parameter changes by modifying the cross-sectional geometry of the links from circular to rectangular with optimized dimensions. The rectangular cross-section with specific width and thickness ratios provides higher moment of inertia and bending resistance without increasing the overall envelope size, allowing the links to withstand larger forces while maintaining compact dimensions for accurate guidance in the guide tube.
Solution Approach 2:
The patent employs composite material strategies by using stainless steel or titanium alloy materials that provide high strength-to-weight ratios. These materials allow the links to achieve required strength levels with reduced cross-sectional dimensions, thereby maintaining compact overall size while resisting breakage under surgical forces.
2Reliability
If the yoke and links are made larger to prevent breakage, then the reliability under force increases, but the section size exceeds the guide tube diameter requiring a larger guide tube
Solution Approach 1:
The patent changes the geometric parameters of the links by adopting a rectangular cross-section with optimized width and thickness dimensions. This configuration provides superior bending resistance and moment of inertia compared to circular sections of equivalent area, enabling the links to resist breakage while maintaining a compact outside diameter that fits within standard guide tubes.
Solution Approach 2:
The patent applies curvature principles by rounding the corners of the rectangular link cross-sections. This rounding reduces stress concentration points that could initiate failure, thereby enhancing reliability without requiring increased overall dimensions. The rounded corners allow the links to withstand larger forces while maintaining the same compact envelope size.
3Force
If the links are subjected to larger forces during use, then the forceps can perform more aggressive surgical operations, but the links break more frequently degrading reliability
Solution Approach 1:
The patent optimizes the cross-sectional parameters of the links by using rectangular sections with specific width-to-thickness ratios. This geometry provides higher area moment of inertia and section modulus, enabling the links to withstand larger surgical forces without exceeding material yield strength, thereby preventing breakage while maintaining the ability to perform aggressive surgical operations.
Solution Approach 2:
The patent utilizes high-strength materials such as stainless steel or titanium alloys with optimized mechanical properties. These materials provide high tensile and yield strength, allowing the links to withstand larger forces during aggressive surgical operations without breaking, thereby maintaining reliability even under high-stress conditions.
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
The compact and strengthened laparoscopy forceps provide improved accuracy and reliability by maintaining structural integrity and fitting within a standard guide tube, reducing the likelihood of breakage and enhancing the precision of surgical operations.
Implementation Method 1
pantograph-forming means that connect the distal end of the control rod to both of the jaws, respectively... pantograph-forming means essentially comprise two links, means for mounting each of the two links via a first one of their two ends to the distal end of the rod, to pivot relative to the control rod
Data Source
AI summary
Disclosed are laparoscopy forceps, including a yoke with a hole, two jaws; a unit for mounting the jaws to pivot relative to the yoke about an axis; a control rod mounted to move in translation in the hole; a pantograph connecting the rod and two jaws using links mounted to pivot on the rod about an axis, two cams secured to the jaws, a mount for each link to pivot relative to a respective one of the two cams about axes, the four pivot axes being parallel, the outside diameter of the yoke being 2D, the width of the links being 2E, the distance between the axes when the two grip faces of the jaws are in contact being 2C, the angle under such circumstances between the axes being 2A, and the values D, E, C, and A being substantially associated by the following equation: D=C+E/cosA.