Variable Force Spring Shoe Sole for Forward Propulsion
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Solution Overview
Problem
Conventional shoe soles with springs return energy too early in the foot stride, failing to effectively utilize stored energy for forward motion due to higher bounce frequency than natural walking or running gait, resulting in inefficient energy transfer.
Innovation Solution
A spring system with a decreasing spring force that stores energy during compression and releases it later, allowing for a forward component of force when the user's center of gravity is forward of the heel, utilizing a combination of rigid and elastic elements and air chambers for energy storage and return.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional spring is used in the shoe sole, then energy is stored during compression, but the energy is returned too early in the foot stride due to high bounce frequency
Solution Approach 1:
The spring transitions from a static, constant-force system to a dynamic, variable-force system. The spring force varies during compression and extension cycles, allowing the system to adapt its characteristics to match the natural gait frequency and delay energy return until the appropriate moment in the stride cycle.
Solution Approach 2:
The spring's force characteristic changes as a function of compression distance. By designing the spring to exert decreasing force with increasing compression, the system modifies its mechanical parameters dynamically, enabling energy to be stored during compression and returned only when the spring extends past the neutral position, thereby delaying energy return to the optimal timing.
2Speed
If a conventional spring with constant force is used, then the bounce frequency is high, but this causes mismatch with natural walking or running gait frequency
Solution Approach 1:
The spring system becomes dynamic rather than static, with force characteristics that change throughout the compression-extension cycle. This dynamic behavior allows the spring to interact with the user's gait in a more adaptable manner, synchronizing energy return with the natural rhythm of walking or running rather than imposing a fixed high-frequency oscillation.
Solution Approach 2:
The spring is designed to resist compression strongly initially, then progressively reduce resistance as compression increases. This preliminary anti-action during compression phases allows the system to accommodate the user's natural gait frequency while still providing adequate shock absorption, preventing the spring from oscillating at its natural high frequency and instead responding to the user's movement rhythm.
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 system effectively stores and returns energy to enhance forward motion by delaying the release of energy until the user's center of gravity is forward, improving energy transfer and reducing the force required during compression, thus enhancing walking and running efficiency.
Implementation Method 1
the force of the user's foot strike can be stored in the elastic deformation of the spring during compression of the sole
Implementation Method 2
the spring comprises at least two air chambers, a first chamber acting to provide resistance to compression and another storing gas ejected from the first chamber and then returning the gas to the first chamber after a delay
Data Source
AI summary
A spring shoe, and also in particular a spring, as well as a method of returning energy to a user, are provided. In one embodiment, a method and apparatus stores foot strike energy and releases it after a slight delay, when it will exert a force on the user which includes a forward component. This is accomplished in an embodiment by a spring in the sole which has a decreasing spring force, such that the force required to compress the sole decreases for all or part of the compression displacement as the spring is compressed.