Knee-ankle-foot orthotic with automatic locking hinge
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Solution Overview
Problem
Existing orthotic devices for patients with knee joint weakness or lack of control fail to provide adequate stability and safety during the weight-bearing stages of gait, as they either lock the knee in extension or allow unnecessary flexion, leading to instability.
Innovation Solution
A low-profile cabling system that automatically unlocks at terminal stance for free knee flexion and reengages at mid-swing to allow only knee extension, ensuring stability before heel contact, using a main hinge assembly with a gear, unidirectional bearing, and locking lever mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the knee is locked in extension during weight-bearing stages, then knee stability is improved, but natural gait and knee flexion are restricted
Solution Approach 1:
The locking mechanism transitions from static to dynamic, automatically locking during stance phase and unlocking during swing phase based on gait cycle requirements, allowing the knee to be stable when needed and flexible when needed
Solution Approach 2:
The orthotic device uses the patient's own ankle dorsiflexion motion to trigger cable tension that automatically locks the knee joint, and uses ankle plantarflexion to release the lock, eliminating the need for external control or power sources
2Ease of operation
If the knee is allowed to flex freely, then natural gait is improved, but knee stability and safety are compromised
Solution Approach 1:
The cable linkage provides mechanical feedback from ankle motion to the knee locking mechanism, where ankle dorsiflexion tensioning the cable triggers knee lock engagement, and ankle plantarflexion releasing the cable allows lock disengagement
Solution Approach 2:
The locking mechanism dynamically adjusts knee stability based on gait phase, being locked during weight-bearing and unlocked during swing phase, providing stability when needed and freedom of motion when needed
3Stability of the object's composition
If existing locking mechanisms are used, then knee stability is improved, but device complexity and profile are increased
Solution Approach 1:
The orthotic device uses the patient's own ankle motion to power the locking mechanism through cable tension, eliminating the need for motors, sensors, or external power sources that would increase complexity
Solution Approach 2:
The cable acts as a mechanical intermediary that transmits force from ankle motion to the knee locking mechanism, simplifying the control system by using a direct mechanical linkage rather than complex electronic or hydraulic 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 device provides enhanced safety and stability by maintaining knee joint stability prior to heel contact, allowing a natural gait while preventing excessive knee flexion, making it safer and more secure for individuals with knee joint issues.
Implementation Method 1
wherein the unidirectional bearing only allows the first and second elongated members to move in one direction in relation to one another, that direction corresponding to the extension of a patient's leg at the knee
Implementation Method 2
wherein the spring maintains the locking lever in an engaged position unless the spring is compressed
Implementation Method 3
wherein when the cable is pulled taught, the spring of the locking lever is compressed, and the locking lever is disengaged from the gear
Data Source
AI summary
An ankle-foot orthotic device comprising a main hinge assembly; ankle hinge assembly; two ankle pivot points; foot plate; lower leg housing member; upper leg housing member; and cable; wherein the main hinge assembly comprises a first elongated member, a second elongated member, and a locking lever; wherein the first elongated member comprises a gear and a unidirectional bearing; wherein a spring maintains the locking lever in an engaged position in which the teeth of the locking lever engage with the teeth on the gear, thereby maintaining the gear in a stationary position; wherein when the cable is pulled taught, the spring of the locking lever is compressed, and the locking lever is disengaged from the gear; wherein the ankle hinge assembly is situated above the heel portion of the foot plate; and wherein the cable connects the ankle hinge assembly to the locking lever.