Prosthetic Foot Dynamic Variable Keel Resistance
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Solution Overview
Problem
Current foot prostheses, such as those with carbon fiber components, fail to accurately replicate the variable resistance and torque changes of natural muscle action during the gait cycle, leading to limitations in limb stability, gait efficiency, and stride symmetry, and often require heavy and costly powered mechanisms to achieve this.
Innovation Solution
A prosthetic foot with an adjustable spring mechanism extending from the forefoot keel to a position posterior to the ankle, incorporating a resilient substrate and a brake system that provides anatomically accurate variable resistance through a combination of carbon fiber and a braking mechanism, allowing for controlled energy storage and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If powered mechanisms with motors, gears, and batteries are used to provide variable resistance during stance phase, then the resistance timing and torque changes approximate normal muscle action, but the weight, cost, and user inconvenience greatly increase
Solution Approach 1:
The patent replaces complex powered mechanical systems (motors, gears, batteries) with a passive mechanical system using a spring mechanism and friction brake. The spring provides energy storage and release, while the friction brake creates variable resistance through controlled slippage, eliminating the need for active power sources while maintaining anatomically accurate resistance timing.
Solution Approach 2:
The spring mechanism automatically stores energy during early stance phase and releases it during late stance phase without external control. The friction brake self-regulates resistance through the natural interaction between the brake pad and drum, creating variable resistance that approximates muscle action without requiring power input or electronic control systems.
2Device complexity
If passive carbon fiber spring action is used to provide energy storage and release, then the structure is simple and lightweight, but the resistance timing and torque changes do not approximate normal muscle action
Solution Approach 1:
The friction brake acts as an intermediary element between the spring mechanism and the environment. It modifies the spring's natural force output by introducing controlled friction and slippage, transforming the simple spring force into a variable resistance profile that better approximates the complex timing and torque changes of normal muscle action during gait.
Solution Approach 2:
The patent introduces dynamic elements to the passive spring system through the friction brake. The brake pad's interaction with the drum creates variable resistance that changes throughout the gait cycle, allowing the system to adapt its mechanical properties dynamically without requiring active control, thus improving resistance timing accuracy while maintaining structural simplicity.
3Weight of moving object
If a friction brake is used to provide variable resistance, then the brake pad experiences wear and requires maintenance, but the system avoids heavy motorized components
Solution Approach 1:
The patent designs the friction brake system with replaceable brake pads that can be easily swapped when worn. The modular design allows users to maintain the lightweight passive system by simply replacing consumable friction elements rather than repairing complex motorized components, balancing maintenance ease with weight savings.
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 adjustable spring mechanism enhances gait efficiency and stability by providing a more natural resistance profile, improving limb alignment and reducing the need for heavy, costly motorized components, while maintaining compliance at low walking speeds and adjusting resistance as needed with increased speed.
Implementation Method 1
The first resilient substrate is configured as a load bearing substrate for a walking human... The third resilient substrate extends through or around the first resilient member and the second resilient member
Implementation Method 2
The brake provides resistance to the travel of the first end of the third resilient substrate in the superior direction
Data Source
AI summary
A prosthetic foot has a frame, a forefoot keel, a heel keel, and an adjustable spring member. The frame couples to a prosthetic leg. The forefoot keel includes a first resilient substrate extending from the frame to the anterior end of the foot. The heel keel member includes a second resilient substrate extending from the frame to the posterior end. The first and second resilient substrates are load bearing substrates for a walking human. The adjustable spring member includes a third resilient substrate and a brake. The third resilient substrate has a first end directly or indirectly coupled to the brake, and a second end coupled to the forefoot keel proximate to the anterior end. The third resilient substrate extends through or around the first resilient member and the second resilient member. The brake provides resistance to the travel of the first end of the third resilient substrate in the superior direction.