Knee Prosthesis Eccentric Bolt Stability
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Solution Overview
Problem
Existing knee prostheses joints face challenges in ensuring permanent securement and stability of pivot bolts, particularly due to linear contact with the slot surface, which affects the joint's ability to adapt to varying shoe heights and user activity levels.
Innovation Solution
Designing at least one axle bolt as a rotatable, lockable eccentric allows for a larger bearing surface and adjustable position, enabling displacement and rotation to change the distance between axle bolts, thereby enhancing stability and flexibility in adapting to different shoe heights and user conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pivot bolt is mounted in a slot with linear contact, then the device structure is simple, but the stability and securement of the pivot bolt is insufficient
Solution Approach 1:
The patent applies the curvature principle by replacing the linear slot contact with a circumferential bearing surface. The pivot bolt contacts the inner surface of the slot along an arc rather than a straight line, providing continuous radial support and significantly improving stability while maintaining the simplicity of the slot structure.
Solution Approach 2:
The patent introduces an intermediary bearing surface between the pivot bolt and the slot. This circumferential surface acts as a mediator that distributes loads and provides continuous contact, enhancing the securement of the pivot bolt without adding complex external components.
2Adaptability or versatility
If the distance between axle bolts is fixed, then the structure is simple, but the adaptability to different shoe heights and user activities is limited
Solution Approach 1:
The patent applies the dynamics principle by making the distance between axle bolts variable rather than fixed. The adjustable mechanism allows the distance to change based on user needs, enabling adaptation to different shoe heights and activity levels while maintaining structural integrity through the circumferential bearing surface.
3Strength
If the pivot bolt has only linear contact with the slot surface, then the manufacturing is simple, but the bearing capacity for compressive forces is insufficient
Solution Approach 1:
The patent enhances bearing capacity by replacing linear contact with circumferential contact. The curved bearing surface distributes compressive forces more effectively across the pivot bolt, significantly increasing load-bearing capacity while adding minimal complexity to the manufacturing process.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Knee prosthesis joint (1) with four pivot bolts (9-12) for connecting four articulating elements (2, 3, 7, 8), each of which is supported at its end by an pivot bolt (9-12), wherein two opposing, transverse articulating elements (2, 3) can be connected on the one hand to a prosthetic stem and on the other hand to a prosthetic foot, and the other two articulating elements, as longitudinal articulating elements (7, 8), can be pivoted relative to each other in both the standing and flexed positions, essentially from an angular position approximating parallel to the knee to a more pronounced oblique position. At least one of the pivot bolts (9, 10) of the articulating element (5) connected to the prosthetic foot is designed as a rotatable, lockable eccentric (13, 16), the rotation of which changes the distance between the two pivot bolts (9, 10) on this articulating element (7).