Double Scissor Hinge Actuation Grip for Microsurgical Instruments
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Solution Overview
Problem
Microsurgical instruments for minimally invasive surgery face challenges in achieving high precision and ergonomic control due to limited transmission ratios and susceptibility to contamination and jamming in existing actuation mechanisms.
Innovation Solution
The actuation grip features a double scissor hinge mechanism with S-shaped levers and a guide pin secured in the inner shank, allowing for a higher transmission ratio and reduced play, enabling precise control with low force input and preventing contamination, as the mechanism is enclosed within the outer contour.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pin-and-slot control system is used to convert lever pivoting movement into axial movement, then the mechanism can transmit force, but the transmission ratio is limited and control precision is reduced
Solution Approach 1:
The control mechanism is segmented into multiple levers (first lever, second lever, third lever) that work together in a scissor hinge arrangement. This segmentation allows each lever to contribute to the overall transmission ratio, achieving higher precision control through the cumulative effect of multiple lever arms rather than relying on a single pin-and-slot mechanism.
Solution Approach 2:
The invention transitions from a two-dimensional pin-and-slot control system to a three-dimensional scissor hinge mechanism with levers arranged in multiple planes. The first lever connects grip parts to the scissor hinge, the second lever forms part of the scissor hinge structure, and the third lever connects the scissor hinge to the actuation rod, creating a multi-dimensional transmission path that increases both transmission ratio and control precision.
2Power
If the levers are positioned closely to increase transmission ratio, then axial excursion increases, but the maximum possible transmission ratio is greatly limited
Solution Approach 1:
The scissor hinge mechanism is designed with dynamic lever positioning capability. The levers can be positioned at different angles and distances from each other, allowing the transmission ratio to be optimized for different operating conditions. This dynamic arrangement enables higher transmission ratios without the mechanical constraints that limit fixed-position lever systems.
3Ease of manufacture
If an open mechanism is used for actuation, then the structure is simple, but the mechanism is susceptible to contamination and can become jammed
Solution Approach 1:
The scissor hinge mechanism and all its moving parts are nested within the hollow shank structure. The grip parts, levers, and actuation rod are all contained within the protective housing of the shank, creating a nested arrangement that maintains structural simplicity while preventing contamination and jamming by isolating the mechanism from the external environment.
4Ease of operation
If a forceps grip design is used for ergonomic control, then one-handed operation is enabled, but the transmission ratio remains relatively small
Solution Approach 1:
The invention merges the ergonomic forceps grip design with a high-ratio scissor hinge mechanism. The grip parts are designed for comfortable one-handed operation while being directly connected to the multi-lever scissor hinge system. This combination allows the surgeon to apply small forces on the grip parts and receive amplified axial movement at the surgical tool, achieving both ergonomic control and high transmission ratio.
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 design allows for precise and fatigue-free control of surgical instruments with low force input, reducing the risk of operating errors and improving manufacturing efficiency by minimizing the impact of production tolerances, while maintaining sterility and preventing jamming.
Implementation Method 1
The axial pin is guided in oblong holes in the inner or outer shank, such that a pivoting movement of the first levers is converted into an axial movement of the shanks relative to one another
Implementation Method 2
The second levers are connected to one another at their ends directed away from the first levers by means of a guide pin, as a result of which a pivoting movement of the second levers is converted into an axial movement of a movable shank
Data Source
AI summary
An actuation grip for a microsurgical instrument, with an inner shaft, which is surrounded coaxially and cylindrically by an outer shaft, wherein the shafts are axially movable relative to each other. Two pivotable grip parts, each with two ends, are coupled pivotably at a proximal end of the actuation grip. On each grip part, a first lever is articulated rotatably via an attachment point between the ends of the grip part, wherein the two first levers are coupled rotatably to each other at an intersection point between their ends. The first levers are each connected rotatably to a second lever at their ends directed away from the grip parts, such that the first levers form, with the second levers, a double scissor hinge which serves to move the two shafts axially relative to each other, in order to use this movement to actuate a surgical tool.