Lever-Actuated Distal Lock for Prosthetic Limb Suspension
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Solution Overview
Problem
Current suspension systems for external prostheses face challenges in providing a reliable and easy-to-use mechanical connection between the limb liner and socket, particularly in maintaining optimal pressure control and comfort, especially during weight-bearing activities and gait cycles.
Innovation Solution
A lever-actuation system that allows for manual operation of a shaft or member to lock/unlock the connection between the limb liner and socket, or control air flow, using a cam mechanism that enables hands-free operation and reduces the need for strength or agility, suitable for vacuum or suction suspension systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional lock mechanism is used to connect the liner to the socket, then the mechanical connection is secure, but the operation requires significant strength and agility making it difficult for users with limited mobility
Solution Approach 1:
A cam-actuated lever mechanism serves as an intermediary between the user's manual input and the lock/unlock action. The lever translates a simple swinging motion into the linear motion needed to engage or disengage the locking element, reducing the strength and dexterity required while maintaining secure connection.
Solution Approach 2:
The mechanism uses a cam profile that converts the dynamic swinging motion of the lever into controlled linear displacement of the locking element. This dynamic transformation allows the lock to be engaged with a simple arc-shaped motion rather than requiring sustained force or precise manual manipulation.
2Reliability
If a vacuum suspension system is used to maintain pressure control, then the suspension is secure and comfortable, but air leakage through the lock mechanism compromises the vacuum integrity
Solution Approach 1:
A flexible membrane or diaphragm is used to seal the vacuum chamber while allowing the mechanical locking elements to move. This flexible barrier prevents air leakage through the lock mechanism during both locked and unlocked states, maintaining vacuum integrity without compromising the mechanical connection security.
Solution Approach 2:
The air sealing function is extracted from the mechanical locking elements and implemented as a separate dedicated sealing system. This allows the lock mechanism to focus on providing secure mechanical connection while the separate sealing system prevents air leakage, resolving the conflict between these two functions.
3Adaptability or versatility
If a complex lock mechanism is used to provide both secure connection and pressure control, then the functionality is comprehensive, but the device complexity increases making it harder to operate and maintain
Solution Approach 1:
The lever-actuated cam mechanism serves multiple functions simultaneously: it provides the locking action, controls the air seal engagement, and maintains vacuum integrity. By consolidating these functions into a single actuation system, the device achieves comprehensive functionality without proportionally increasing complexity.
Solution Approach 2:
The mechanical locking function and the air sealing function are merged into a single integrated mechanism actuated by the same lever. The cam profile coordinates both the locking element displacement and the seal engagement, allowing one actuation to accomplish multiple objectives and reducing overall system complexity.
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 lever-actuation system provides a convenient, comfortable, and reliable mechanism for securing and releasing the prosthetic limb, maintaining optimal pressure control and preventing air leakage, thus enhancing the usability and effectiveness of suspension systems for prosthetic limbs.
Implementation Method 1
using a cam mechanism that enables hands-free operation
Data Source
AI summary
A lever-actuated distal lock connects a limb liner to a prosthetic leg or arm hard socket. In some versions, air-sealing capability may limit/prevent air flow through the distal lock, even with vacuum inside the socket. To unlatch the lock, a lever is swung to pull a sliding shaft outward in the lock housing. Swung in the opposite direction, the lever releases the sliding shaft to be biased to a latched position wherein slanted surfaces of the shaft inner end and a liner pin cooperate to allow the pin to slide down into, but not up out of, the lock. In some versions, the shaft inner end slides relative to, but is biased away from, the shaft opposite end, so that the inner end moves out of the way of the downwardly-sliding pin, without moving the entire lock shaft and without disrupting the optional air seal.