Microinvasive Scissors With Oscillating Cutting Edges
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Solution Overview
Problem
Medical scissors for microinvasive applications face challenges in reliability due to small dimensions and limited mechanical control, leading to potential slipping of material during cutting, which can prolong procedures and pose health risks.
Innovation Solution
The design features oscillating cutting edges with varying wedge angles and beveled surface widths on the scissor blades, ensuring precise intersection points and alternating sections for improved cutting efficiency and reduced slipping risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional scissors design is used in microinvasive applications, then the structure is simple and easy to manufacture, but the cutting reliability deteriorates due to material slipping
Solution Approach 1:
The cutting edge is segmented into multiple alternating sections with different wedge angles (first sections with smaller wedge angles and second sections with larger wedge angles). This segmentation allows different portions of the cutting edge to perform different functions: some sections provide sharp cutting while others provide clamping, thereby improving cutting reliability without requiring complete redesign of the entire scissors structure.
Solution Approach 2:
Different sections of the cutting edge are given different local qualities through varying wedge angles. The first sections have smaller wedge angles for sharp cutting action, while the second sections have larger wedge angles for clamping action. This local differentiation ensures that each part of the cutting edge is optimized for its specific function, improving overall reliability.
2Reliability
If the scissor blades have uniform wedge angle, then the manufacturing is simple, but the cutting performance deteriorates due to inability to prevent material slipping
Solution Approach 1:
The cutting edge is divided into alternating first and second sections with different wedge angles. This segmentation enables the cutting edge to perform both cutting and clamping functions along its length, preventing material slipping while maintaining a relatively simple manufacturing process compared to completely complex designs.
Solution Approach 2:
The cutting edge features periodic alternation between first sections (smaller wedge angles) and second sections (larger wedge angles). This periodic variation in geometry creates alternating cutting and clamping zones that work in sequence during the cutting motion, reliably preventing material slipping through rhythmic engagement of different section types.
3Productivity
If the cutting edge has constant wedge angle, then the geometry is simple, but the cutting efficiency deteriorates due to material slipping and prolonged procedure duration
Solution Approach 1:
The cutting edge geometry is segmented into alternating first and second sections with different wedge angles. This segmentation enables simultaneous achievement of sharp cutting (in first sections) and secure clamping (in second sections), eliminating material slipping and improving cutting efficiency without requiring overly complex geometries.
Solution Approach 2:
Different local regions of the cutting edge are optimized with different wedge angles: first sections have smaller angles for efficient cutting, while second sections have larger angles for secure clamping. This local optimization ensures that each region contributes to overall cutting efficiency, preventing material slipping and reducing procedure duration.
4Reliability
If the scissor blades have simple geometry, then the ease of operation is good, but the cutting reliability deteriorates due to lack of mechanical control in microinvasive applications
Solution Approach 1:
The cutting edge is segmented into alternating first and second sections that work in sequence during operation. This segmentation provides enhanced mechanical control through alternating cutting and clamping actions, improving reliability while maintaining relatively simple operation compared to complex active control systems.
Solution Approach 2:
The cutting edge geometry transitions from static uniform wedge angle to dynamic alternating wedge angles along the cutting path. As the scissor blades close, different sections engage in sequence, creating a dynamic cutting-clamping-closing cycle that improves mechanical control and reliability while maintaining simplicity of operation.
Data Source
AI summary
Microinvasive medical scissors include a first scissor blade (30) with a first cutting edge (35, 36) between a flank surface (33) and a beveled surface (37, 38), a relatively moveable second scissor blade (40) with a second cutting edge (45, 46) between a flank surface (43) and a beveled surface (47, 48), a guiding device (24) for mechanical guiding of the second cutting edge to touch the first cutting edge at any time in a point of intersection (50). The guiding device is connectable to a shaft (16) of a microinvasive instrument (10). The cutting edges have respective parameters which increase and decrease several times along the second cutting edge. The parameters are the wedge angle (β1, β2,) between the flank surface and the beveled surface, the cutting angle (δ1, δ2), or the width (b1, b2) of the beveled surface.