Variable Sharpness Reamer for Controlled Bone Cutting
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Solution Overview
Problem
Conventional bone reamers face issues with overshooting and deforming holes during cortical bone penetration, leading to overheating and inefficient cutting, which can result in bone necrosis and the need for frequent tool replacement, while also causing unnecessary trauma to surrounding soft tissue.
Innovation Solution
A reamer with variable sharpness, where the sharpness decreases with increasing radius from the axis, allowing for precise and controlled cutting with reduced force, and featuring a flat body with blade wings and a depth limit stop for accurate hole depth management, enabling constant pressure application and minimizing overshooting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional reamers with uniform sharpness are used, then initial cortical bone can be cut, but the reamer quickly dulls and generates excessive heat causing bone necrosis
Solution Approach 1:
The reamer applies the local quality principle by varying the sharpness of cutting blades across different radial positions. Central blades (near axis) are sharper to efficiently penetrate hard cortical bone, while peripheral blades are less sharp to reduce heat generation in softer cancellous bone, thereby preventing bone necrosis while maintaining cutting efficiency.
2Force
If excessive reaming force is applied to penetrate cortical bone, then initial bone penetration is achieved, but surrounding soft tissue is damaged and bone necrosis occurs
Solution Approach 1:
The reamer concentrates sharper blades at the central region to focus cutting action on the hard cortical bone, requiring less overall force. This localized sharpness distribution enables effective penetration without applying excessive force that would damage surrounding soft tissue.
3Reliability
If conventional reamers are replaced frequently to maintain cutting efficiency, then consistent cutting performance is achieved, but material wastage and cost increase
Solution Approach 1:
The reamer design with variable sharpness allows different blade regions to wear at different rates appropriate to their function. Central sharper blades wear more quickly as expected, while peripheral blades maintain their less sharp condition. This differential wear pattern extends the overall reamer life and reduces replacement frequency compared to uniform sharpness designs.
Data Source
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AI summary
A flat reamer (200) has a reamer shaft (270) and two opposite blade wings (220, 221). The blade wings have a proximal reamer area (202) with first cutting areas (240-241) and second cutting areas (250-252) intermittently separated by first recesses (245-246) and second recesses (255-256), respectively. The cutting areas have variable sharpness with the highest sharpness at the center and decreasing to the outside.