Variable Stiffness Prosthetic Foot via Tongue Engagement
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Solution Overview
Problem
Existing prosthetic feet have fixed stiffness levels, which do not accommodate the varying demands of different gait phases, leading to suboptimal performance in terms of flexibility and energy return during dorsiflexion and plantarflexion.
Innovation Solution
A prosthetic foot with an adjustable stiffness mechanism, featuring a tongue portion that can be selectively connected or disconnected from the main foot element using engagement members and spring mechanisms, allowing for customizable stiffness in both dorsiflexion and plantarflexion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the prosthetic foot uses fixed stiffness materials and structure, then the manufacturing is simple and cost-effective, but the adaptability to different gait phases is poor
Solution Approach 1:
The patent applies the dynamics principle by making the prosthetic foot structure adjustable rather than fixed. The tongue portion can be selectively connected or disconnected from the heel portion through engagement members, allowing the stiffness characteristics to change dynamically between locked and unlocked states. This enables the foot to adapt to different gait phases (stance and swing) while maintaining a relatively simple overall structure that does not require complex continuous adjustment mechanisms.
Solution Approach 2:
The patent segments the prosthetic foot into distinct functional portions: a heel portion, a toe portion, and a tongue portion. The tongue portion is further divided with engagement members that can independently connect to the heel portion. This segmentation allows different parts to perform specialized functions (energy storage in heel, propulsion in toe) while enabling selective connection to achieve variable stiffness without requiring the entire structure to be complex.
2Stability of the object's composition
If the prosthetic foot has high stiffness for structural support, then the stability during stance phase is improved, but the flexibility during swing phase is reduced
Solution Approach 1:
The engagement members enable dynamic transition between locked and unlocked states. During stance phase, the engagement members connect the tongue portion to the heel portion, creating a stable, high-stiffness structure that provides structural support. During swing phase, the engagement members can be disengaged, allowing the tongue portion to flex independently and providing the necessary flexibility for natural swing motion. This dynamic state change resolves the contradiction between stability and flexibility.
3Strength
If the tongue portion is permanently connected to provide structural integrity, then the strength is maintained, but the energy return during dorsiflexion is reduced
Solution Approach 1:
The tongue portion is segmented from the heel portion through the cutout, with engagement members providing selective connection. During dorsiflexion, the engagement members can be disengaged, allowing the tongue portion to move independently and store elastic energy through flexing. This independent motion enables energy storage and return that would be lost if the tongue were permanently rigidly connected. The structural integrity is maintained when engaged, while energy return is enabled when disengaged.
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 stiffness mechanism enhances the prosthetic foot's ability to mimic natural foot behavior, providing greater flexibility and energy return during heel strike and toe-off phases, thereby improving user mobility and comfort.
Implementation Method 1
The mechanism includes a shaft extending through an aperture near a proximal end of the tongue portion, a flange at a first end of the shaft, an adjustment knob at a second end of the shaft, a washer slidably disposed on the shaft between the adjustment knob and the foot element, and a spring disposed around the shaft. The spring extends between and is coupled to the adjustment knob and the washer.
Implementation Method 2
The mechanism includes first and second engagement members coupled to the tongue portion. The first engagement member is disposed on a front side of the foot element and the second engagement member is disposed on a back side of the foot element. The first engagement member is configured to be actuated to selectively operatively connect or operatively disconnect the tongue portion from the remainder of the foot element in dorsiflexion, and the second engagement member is configured to be actuated to selectively operatively connect or operatively disconnect the tongue portion from the remainder of the foot element in plantarflexion.
Data Source
AI summary
Prosthetic feet that provide for variable and adjustable stiffness are provided. A foot element can include a tongue portion defined or formed by a slot in the foot element that at least partially separates the tongue portion from a remainder of the foot element. The tongue portion can be operably connected to the remainder of the foot member to increase the stiffness of the foot member or operably disconnected from the remainder of the foot member to increase the flexibility of the foot member. The prosthetic foot further includes a mechanism for adjusting whether the tongue portion is operably connected or disconnected from the remainder of the foot member. The mechanism can be selectively actuated to adjust the stiffness of the foot element in dorsiflexion and/or plantarflexion and/or to adjust the degree to which the tongue portion is allowed to flex relative to the remainder of the foot member.