4-Leaf Clover Coupling for Torque Transmission in Surgical Handpieces
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Solution Overview
Problem
Current surgical instruments face challenges in transmitting high torques efficiently and reliably due to material weaknesses and limited torque transmission capabilities, particularly in small-diameter handpiece shanks, which restricts their usability and requires specialized tools for each handpiece shaft length and shape.
Innovation Solution
A coupling system with a 4-leaf clover cross-sectional shape is introduced, featuring male and female coupling parts that allow axial displacement and enhanced radial guidance, reducing the risk of self-locking and enabling higher torque transmission without the need for additional radial bearings, thus facilitating the use of universal tools across different handpiece shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional coupling designs are used in small-diameter handpiece shanks, then the structure is simple, but the torque transmission capability is insufficient and reliability is reduced
Solution Approach 1:
The coupling parts feature an asymmetric 4-leaf clover cross-sectional shape with lobes of different orientations. This asymmetric geometry provides enhanced torque transmission through increased surface area and mechanical interlocking, while the specific lobe configuration prevents self-locking during axial displacement. The asymmetric design allows the coupling to transmit higher torques than symmetric designs of the same size, resolving the contradiction between strength and complexity.
Solution Approach 2:
The invention transitions from traditional circular or simple geometric coupling cross-sections to a multi-lobed 4-leaf clover shape. This dimensional change in the cross-sectional geometry creates multiple contact points and increased mechanical engagement between the male and female coupling parts. The multi-dimensional lobe structure enables superior torque transmission within the constrained small-diameter handpiece shank without requiring additional radial bearings or complex external support structures.
2Ease of operation
If conventional coupling geometries are used, then manufacturing is straightforward, but self-locking occurs and axial displacement is restricted
Solution Approach 1:
The asymmetric 4-leaf clover cross-section with specifically oriented lobes prevents self-locking during axial displacement. The non-uniform lobe configuration allows one coupling part to rotate and displace axially relative to the other without becoming mechanically locked, enabling tool changes and operational adjustments. This asymmetric geometry maintains manufacturing feasibility through standard machining processes while eliminating the self-locking problem of conventional symmetric designs.
Solution Approach 2:
The coupling design incorporates dynamic characteristics through the 4-leaf clover geometry that allows controlled axial displacement and rotation during operation. The lobe structure enables the coupling to transition between different mechanical states - engaged for torque transmission and disengaged for tool changes - without requiring complex actuation mechanisms. This dynamic capability improves ease of operation while the geometry itself is manufactured using conventional methods.
3Adaptability or versatility
If specialized tools are provided for each handpiece shaft, then torque transmission is optimized, but production and maintenance costs increase
Solution Approach 1:
The male and female coupling parts with matching 4-leaf clover cross-sections create a universal interface that can be used across different handpiece shaft configurations. This single coupling design replaces the need for multiple specialized tools for different shaft types. The standardized coupling geometry maintains optimized torque transmission while enabling interchangeability across various handpiece models, significantly reducing production volumes and maintenance costs through parts commonality.
Data Source
Figure 1
Figure 2~4a
Figure 4b
AI summary
A surgical torque-transferring instrument includes a preferably universal handpiece to which a handpiece shaft having an internal torsion rod or an internal tool shaft can be connected. The torsion rod can be connected to a torque transmission train or drive within the handpiece via a plug-type coupling which includes a male and female coupling piece which can be axially plugged into each other. The cross-sectional shape of the two coupling pieces approximately corresponds to a four-leaved cloverleaf.