Adjustable Friction Locking Shoulder Joint Mechanism
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Solution Overview
Problem
Prosthetic shoulder joints face challenges with high friction requiring excessive force for repositioning, potential slippage, and lack of free-swing mode, as well as inefficient control cable management, making them uncomfortable and difficult to use, especially during walking.
Innovation Solution
A lightweight prosthetic shoulder joint with adjustable friction, capable of switching between fully locked and free-swing states, featuring a flexion-extension bearing that can sustain 50 ft-lb torque, with a lock that can be manually or remotely operated, and a mechanism allowing auto-engagement and multiple locking positions, utilizing a rotor with equidistant pins and a cam system for smooth motion and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction is increased to prevent slippage, then stability is improved, but excessive force is required to reposition the joint
Solution Approach 1:
The patent applies dynamics by making the friction characteristic adjustable rather than fixed. The friction mechanism can dynamically change between high friction (locked) and low friction (free-swing) states based on user needs, resolving the contradiction between stability and ease of repositioning
Solution Approach 2:
The patent changes the friction parameter from a constant value to a variable that can be adjusted between different states. By modifying the friction parameter through the locking mechanism, the system achieves both high stability when locked and low repositioning force when unlocked
2Ease of operation
If friction is decreased to reduce repositioning force, then ease of operation is improved, but inadvertent slippage occurs
Solution Approach 1:
The friction mechanism dynamically adapts to operational needs by switching between low friction for easy repositioning and high friction for stable positioning, preventing slippage during use while maintaining ease of adjustment
3Ease of operation
If a free-swing mode is added to increase comfort during walking, then ease of operation is improved, but control complexity increases
Solution Approach 1:
The patent segments the control function into distinct locked and free-swing modes that can be independently selected. This segmentation allows the complex free-swing capability to be added without overwhelming the control system, as each mode has its own dedicated control pathway
Solution Approach 2:
The locking mechanism serves multiple functions: it provides both stable locked positioning and controlled free-swing modes. This multi-functionality reduces overall control complexity by using a single mechanism to handle both operational requirements
4Ease of operation
If control cables are made accessible for manual operation, then ease of operation is improved, but they become prone to tangling and catching during movement
Solution Approach 1:
The control cables are nested within protective conduits or channels that guide their movement. This nesting prevents the cables from becoming exposed and tangling during joint movement, while still allowing accessible control points to be reached when needed
Data Source
AI summary
A locking shoulder joint adapted to be attached to a user's shoulder, generally comprising a rotor provided with a plurality of radially positioned pins, that rotates relative to a stator, and a cam provided with one or more plungers adapted to engage said rotor pins to releasably lock said rotor in position selected by said user, all of which act to move a humeral member in a direction corresponding to a flexion/extension direction of the shoulder joint; and a yoke coupled to an axle for moving the humeral member in a direction corresponding to an abduction/adduction direction of the shoulder joint.