Lobed Torque Limiter Mechanism for Orthopedic Tools
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Solution Overview
Problem
Prior art torque limiters in orthopedic surgical tools have complex structures with multiple components, leading to misalignment and the need for frequent maintenance and recalibration, which complicates their use in precise torque applications during procedures like reaming and fastening.
Innovation Solution
A torque limiting tool with a simplified design comprising a sleeve and a torque drive coupler, featuring longitudinally extending lobes and grooves that engage to transfer torque, disengaging when the torque limit is exceeded, reducing the likelihood of misalignment and recalibration needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior art torque limiters use complex structures with multiple components, then torque limiting function is achieved, but device complexity increases and misalignment occurs requiring frequent maintenance
Solution Approach 1:
The patent combines multiple torque limiting components into a single integrated mechanism featuring interlocking lobes and grooves. The drive shaft, torque limiter, and fastening mechanism are merged into one unified structure that limits torque through the geometric interaction of lobes and grooves, eliminating the need for separate bias members and ball bearings found in prior art devices.
Solution Approach 2:
The torque limiter is segmented into distinct functional zones within the single mechanism: the lobed drive shaft section, the grooved coupling section, and the fastening mechanism. This segmentation allows each zone to perform its specific function while maintaining overall structural simplicity and reducing the total number of components.
2Reliability
If prior art torque limiters use multiple components, then torque limiting function is achieved, but maintenance and recalibration frequency increases
Solution Approach 1:
The patent combines multiple torque limiting components into a single integrated mechanism featuring interlocking lobes and grooves. The drive shaft, torque limiter, and fastening mechanism are merged into one unified structure that limits torque through the geometric interaction of lobes and grooves, eliminating the need for separate bias members and ball bearings found in prior art devices.
Solution Approach 2:
The lobed and grooved structure is designed to self-align during assembly and operation, with the geometry of the lobes and grooves automatically ensuring proper positioning without requiring external calibration tools or procedures. The structure is also designed to be easily disassembled and reassembled by the end user without specialized maintenance equipment.
3Ease of manufacture
If torque limiting tool uses simplified design with fewer components, then manufacturing ease improves, but torque transfer reliability may worsen
Solution Approach 1:
The lobes and grooves are designed with asymmetric geometries that create directional torque transfer characteristics. The lobes have varying depths and angles that engage with corresponding grooves to provide reliable torque transfer in the driving direction while allowing controlled slippage when torque exceeds the limit. This asymmetric design achieves complex mechanical functionality through relatively simple geometric features that are easy to manufacture.
Solution Approach 2:
The lobes and grooves incorporate curved surfaces that facilitate smooth engagement and torque transfer. The rounded profiles of the lobes mating with the grooves create gradual contact areas that distribute stress evenly, improving reliability while maintaining manufacturing simplicity through standard machining or molding operations.
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 tool effectively limits torque in both clockwise and counterclockwise directions, minimizing the risk of damage to orthopedic implants or bone plates, and reducing maintenance requirements due to its fewer components and robust construction.
Implementation Method 1
The sleeve and the coupler are configured so that they mate together. The plurality of first and second elongated lobes of the sleeve and coupler are received within a corresponding first and second grooves of the sleeve and coupler. Rotation of the coupler causes a physical interference of the mated lobes of the sleeve and coupler that results in torque being transferred from the coupler to the sleeve and connected drive shaft.
Data Source
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AI summary
A torque limiting tool is described. The tool comprises a torque limiting mechanism comprising a sleeve connectable to a drive shaft and a torque drive coupler that resides within a housing. The sleeve comprises a sleeve annular sidewall having a plurality of outwardly projecting elongated first lobes and recessed first grooves that are circumferentially positioned along the length thereof. The drive coupler comprises a socket defined by a coupler annular sidewall having a plurality of outwardly projecting second elongated lobes and recessed second grooves positioned along the coupler interior sidewall. Torque is transferred therebetween when the ramped surfaces of the first and second lobes mate within respective second and first grooves of the coupler and sleeve. When a torque limit is exceeded, the first and second lobes of the sleeve and coupler disengage for their respective second and first grooves.