Knee Prosthesis Locking Mechanism Using Roller Freewheel
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Solution Overview
Problem
Existing knee prostheses with electrical systems are complex, costly, and require frequent maintenance, making them inaccessible in countries with limited medical infrastructure, and their mechanical assembly can be tricky, especially for users with low muscular potential.
Innovation Solution
A mechanical knee prosthesis with a simplified locking/unlocking mechanism using a roller freewheel assembly and pinion system, which is easy to assemble, reliable, and adaptable for various positions, including seated and standing, with automatic commissioning in walking mode, ensuring natural walking movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sophisticated electrical systems with hydraulic cylinders and microprocessors are used, then precise adjustments are achieved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces complex electrical-hydraulic systems with a purely mechanical solution using a freewheel mechanism, cable, pulleys, and spring. This mechanical substitution eliminates the need for microprocessors, sensors, and hydraulic cylinders while achieving the required functional precision for knee prosthesis control.
Solution Approach 2:
The invention uses simple, inexpensive mechanical components that can be easily manufactured and replaced if needed. The freewheel mechanism, cable, and pulleys are basic mechanical elements that are far cheaper than electrical-hydraulic systems, making the prosthesis accessible in resource-limited settings.
2Ease of operation
If cable control means with preload springs are used, then locking/unlocking function is achieved, but assembly becomes tricky and complex
Solution Approach 1:
The freewheel mechanism automatically locks and unlocks based on the direction of force applied to the cable. When the cable is tensioned during leg extension, the freewheel engages automatically without requiring complex adjustment mechanisms. This self-acting mechanism simplifies assembly while maintaining operational control.
3Device complexity
If mechanical freewheel control is used, then device simplicity and reduced cost are achieved, but assembly remains tricky requiring adjusted cables and springs
Solution Approach 1:
The patent incorporates a preload spring that is pre-adjusted during manufacturing to tension the cable and engage the freewheel mechanism. This preliminary action ensures that the assembly arrives pre-configured, eliminating the need for field adjustments of cables and springs, thereby simplifying the assembly process while maintaining mechanical simplicity.
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 solution provides a cost-effective, reliable, and easy-to-assemble knee prosthesis that ensures natural walking movements with reduced maintenance needs, suitable for users with low muscular potential and accessible in resource-limited settings, while maintaining safety and stability.
Implementation Method 1
A mechanical knee prosthesis with a simplified locking/unlocking mechanism using a roller freewheel assembly
Implementation Method 2
A mechanical knee prosthesis with a simplified locking/unlocking mechanism using a roller freewheel assembly and pinion system
Data Source
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AI summary
The subject matter of the invention is a locking/unlocking device for a knee prosthesis (10), comprising a femoral part (12) and a tibial part (14) provided with a tibial plate (14‐1), said femoral part (12) and tibial part (14) both being mounted in rotation, coaxial about an axis XX', characterised in that it comprises: ‐ a disk (16) constituting the femoral part (12), ‐ two left and right flanges (22‐1, 22‐2) and a through shaft (24), ‐ a free-wheel mounting (28) comprising a pinion (30) provided with ramps (32) and one roller (38) per ramp, ‐ unlocking means (40) comprising a wheel (42) with pins (44), and ‐ a part (46) offset from the unlocking means comprising angular control means (48) constituted by at least one link rod (52) interposed between said offset part and the tibial plate (14-1).