Surgical Tool Coupling Geometry for Self-Aligning Torque Transfer
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Solution Overview
Problem
Current surgical cutting tools and handpieces face issues with high contact stresses, reduced interface stiffness, and alignment problems due to complex machining requirements, leading to reliability concerns and user frustration.
Innovation Solution
The surgical cutting tool features an elongated shaft with a coupling portion that includes oblique deflection surfaces and interface structures, promoting self-alignment with the drive chuck of the handpiece, enhancing torque transfer and alignment during insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If complex machining/grinding is used to achieve torque transmission and axial retention features, then torque transmission capability is improved, but contact stresses increase and interface stiffness is reduced
Solution Approach 1:
The coupling portion is divided into multiple interface structures (first and second interface structures) with distinct driven surfaces, separating the torque transmission function from axial retention. This segmentation allows each surface to be optimized for its specific function, reducing the need for complex machining on single surfaces and lowering contact stresses.
Solution Approach 2:
The invention transitions from point contacts solely about a single central axis to distributed surface contacts in multiple dimensions. The first and second driven surfaces provide torque transmission at different angular positions and radial locations, creating a multi-dimensional contact interface that increases overall interface stiffness while distributing contact stresses.
2Strength
If complex machining/grinding is used to achieve torque transmission and axial retention features, then torque transmission capability is improved, but interface stiffness is reduced
Solution Approach 1:
The coupling portion is divided into multiple interface structures (first and second interface structures) with distinct driven surfaces, separating the torque transmission function from axial retention. This segmentation allows each surface to be optimized for its specific function, reducing the need for complex machining on single surfaces and lowering contact stresses.
Solution Approach 2:
The invention transitions from point contacts solely about a single central axis to distributed surface contacts in multiple dimensions. The first and second driven surfaces provide torque transmission at different angular positions and radial locations, creating a multi-dimensional contact interface that increases overall interface stiffness while distributing contact stresses.
3Ease of manufacture
If traditional cylindrical shank with point contacts is used, then manufacturing is simpler, but alignment between shank and drive chuck becomes problematic
Solution Approach 1:
The deflection surfaces are positioned at the leading edge of the coupling portion to engage with the drive chuck first during insertion. This preliminary engagement initiates self-alignment before the main driven surfaces make contact, ensuring proper orientation without requiring complex alignment procedures by the user.
Solution Approach 2:
The deflection surfaces automatically perform the alignment function when the tool is inserted into the drive chuck. The oblique geometry of these surfaces causes them to deflect and guide the interface structures into proper alignment with the drive pins, eliminating the need for user intervention or complex alignment procedures.
4Ease of manufacture
If traditional cylindrical shank with point contacts is used, then manufacturing is simpler, but reliability decreases due to high contact stresses
Solution Approach 1:
The coupling portion is divided into multiple interface structures (first and second interface structures) with distinct driven surfaces, separating the torque transmission function from axial retention. This segmentation allows each surface to be optimized for its specific function, reducing the need for complex machining on single surfaces and lowering contact stresses.
Solution Approach 2:
The invention transitions from point contacts solely about a single central axis to distributed surface contacts in multiple dimensions. The first and second driven surfaces provide torque transmission at different angular positions and radial locations, creating a multi-dimensional contact interface that increases overall interface stiffness while distributing contact stresses.
Data Source
Figure 1
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AI summary
A surgical cutting tool (22) includes an elongated shaft (30) and a cutting head (38). The shaft defines a coupling portion (36) terminating at a proximal end (62) of the shaft, a stem portion (34), and a distal portion (32). The stem portion defines a central axis A. The coupling portion optionally defines a deflection surface (72a, 72b) positioned oblique with respect to the central axis and connected with a first driven surface (76a) and a second driven surface (74a). Upon insertion into a drive chuck (40) with drive pins (44a, 44b), the deflection surface promotes self-alignment of the cutting tool and the drive chuck.