Passive Artificial Knee with Toggle Locking for Natural Gait
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Solution Overview
Problem
Current stance control orthoses for knee-ankle-foot orthotics require sensors and electrical power sources, making them complex and costly, and there is a need for a simpler, economically constructed device that assists walking without these dependencies.
Innovation Solution
A passive power-conservative artificial knee with a compressive force generator and a dual operational mode release mechanism that uses a strut actuator and a cam slot mechanism to lock and unlock the knee joint based on the angle of the shank link relative to the thigh link, allowing for natural gait without the need for sensors or electrical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If traditional KAFO locks the knee in full extension to provide stability, then knee stability is improved, but gait naturalness deteriorates leading to overuse injuries
Solution Approach 1:
The knee joint transitions from a static locked position to a dynamic controlled state. The mechanism allows the knee to be locked in full extension during stance phase for stability, then automatically unlocks to allow natural flexion during swing phase, creating a dynamic system that adapts to gait requirements
Solution Approach 2:
The knee locking mechanism is self-actuating through the user's own movement. The quadriceps tendon and patellar ligament serve as the actuating force, automatically locking the knee during weight-bearing without external control systems
2Ease of operation
If SCO allows knee flexion during swing phase to enable natural gait, then gait naturalness is improved, but knee stability during stance phase must be maintained
Solution Approach 1:
The knee joint undergoes periodic locking and unlocking cycles corresponding to the gait cycle. The mechanism locks during stance phase and unlocks during swing phase, creating a rhythmic pattern that matches natural walking mechanics
Solution Approach 2:
The system uses the user's own quadriceps contraction and patellar ligament tension to automatically control locking and unlocking, eliminating the need for external sensors or power sources while maintaining both stability and natural motion
3Measurement precision
If sensors and electrical power sources are used in SCO to control knee locking, then control precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces electronic sensing and control systems with a purely mechanical solution. The quadriceps tendon and patellar ligament serve as mechanical sensors that directly actuate the locking mechanism through their natural tension and relaxation during gait
Solution Approach 2:
The body's own tissues (quadriceps tendon and patellar ligament) serve as both the actuator and sensor for the locking mechanism, eliminating the need for external power sources, batteries, or electronic control systems
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 stable and natural walking assistance by resisting and encouraging flexion and extension of the knee joint based on the angle, reducing the risk of overuse injuries and gait deviations, while being simpler and more cost-effective than existing systems.
Implementation Method 1
a compressive force generator rotatably coupled to said shank link, said compressive force generator providing a compressive force that said release mechanism uses to lock said shank link to said thigh link
Implementation Method 2
a cam slot mechanism to lock and unlock the knee joint based on the angle of the shank link relative to the thigh link
Implementation Method 3
a strut actuator and a cam slot mechanism to lock and unlock the knee joint
Data Source
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AI summary
A passive artificial knee comprises first and second links rotatably coupled at a knee joint, a passive compressive force generator rotatably coupled to the second link, and a release mechanism coupled to the first link. When a relative angle of the first and second links is less than a toggle angle, the release mechanism locks in a first operational mode, and the force generator compresses, resisting the flexing of the second link relative to the first link. When the relative angle is larger than the toggle angle, the force generator decompresses and encourages the flexion of said second link relative to said first link. When the force generator is substantially extended and said compressive force is substantially small, the release mechanism moves into a second operational mode, wherein the force generator neither resists nor encourages the extension and flexion of said second link from said first link.