Variable Ratio Lever Mechanism for Surgical Instrument Actuation
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Solution Overview
Problem
Existing surgical instruments for minimally invasive surgery lack an efficient mechanism for manual actuation that effectively changes the transmission ratio of force and displacement, leading to suboptimal power and speed distribution during operation.
Innovation Solution
A surgical instrument with an operating unit featuring a lever mechanism that changes its gear ratio upon actuation, utilizing a base, a handle, a drive member, and levers with different lever arms to increase force transmission while decreasing displacement transmission, allowing for enhanced power and displacement transmission through a planar lever mechanism and a bell crank design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed transmission ratio mechanism is used in the operating unit, then the structure is simple, but the force and displacement transmission efficiency is suboptimal throughout the actuation range
Solution Approach 1:
The patent applies the dynamics principle by designing a lever mechanism where the transmission ratio changes dynamically during actuation. The lever arm lengths are configured such that the distance from the pivot point to the handle attachment point differs from the distance to the drive element attachment point, creating a variable transmission ratio that adapts throughout the movement range, thereby optimizing both force and displacement transmission efficiency without requiring an overly complex mechanism.
Solution Approach 2:
The patent implements parameter changes by varying the effective lever arm lengths during actuation. As the lever moves through its range of motion, the perpendicular distances from the pivot axis to the force application points change, resulting in a changing transmission ratio. This allows the system to provide high force multiplication when needed while maintaining adequate displacement transmission, resolving the contradiction between transmission efficiency and structural simplicity.
2Speed
If the handle is moved at constant speed, then the operation is smooth and controlled, but the drive element speed varies due to changing transmission ratio
Solution Approach 1:
The dynamic lever mechanism inherently accepts variable speed transmission as a consequence of the changing transmission ratio. When the user moves the handle at constant speed, the drive element speed varies according to the instantaneous lever arm ratios, which is acceptable because the mechanism is designed to provide optimal force and speed distribution at different positions in the actuation range rather than maintaining uniform speed throughout.
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 mechanism provides increased power and displacement transmission, supporting the tool parts like scissors or forceps, with a smaller initial displacement of the drive member that increases as the handle is moved, and a higher force exerted on the drive member relative to the handle, improving the surgical instrument's efficiency and ease of use.
Implementation Method 1
a lever (17) coupled to the handle (6) and the drive element (13) for transmitting a movement of the handle (6) to the drive element (13)
Implementation Method 2
The lever arm with which the handle (6) engages the lever (17) is longer than the lever arm with which the lever (17) engages the drive element (13)
Implementation Method 3
A second connecting element pivotally connects the handle (6) and the lever (17)
Data Source
Figure 1~3
Figure 4~7
AI summary
The invention relates to a surgical instrument (1) with two handles (6) that can be pivoted against a base (2) to actuate the instrument (1). Movement of the handles (6) is transmitted via connecting elements (7, 11) and angled levers (8) to a shaft (4) that is slidable within a hollow shaft (3). The invention proposes arranging the angled levers (8) such that their angular position changes when the surgical instrument (1) is actuated, thereby increasing the force transmission.