Unidirectional Arm Support Joint with Wrap Spring Brake
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Solution Overview
Problem
Existing orthopedic devices that support arms require continuous force application, making it uncomfortable and disruptive to move the arm in the opposite direction or lower it when not needed, as they apply a permanent force even when the arm is raised.
Innovation Solution
A device with a joint system that allows movement in one direction while blocking it in the opposite direction, using a wrap spring or magnetorheological fluid to provide a self-amplifying brake, which can be unblocked with an actuator or magnetic field control based on sensor data to enable movement in both directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a permanent force is applied to the arm to support it, then the arm support function is improved, but the comfort and ease of movement in the opposite direction deteriorates
Solution Approach 1:
The joint transitions from a static force application system to a dynamic system that adapts its behavior based on movement direction. The joint allows free movement in the lowering direction while blocking movement in the raising direction, creating a dynamic response that eliminates the need for continuous force application and improves ease of operation.
Solution Approach 2:
The joint is divided into two functional segments: a first operating mode for allowing movement in the lowering direction (first direction) and a second operating mode for blocking movement in the raising direction (second direction). This segmentation enables the system to provide support force when needed while eliminating unnecessary force when the arm is being lowered.
2Force
If a permanent force is applied to the arm, then the arm support function is improved, but the device complexity increases due to continuous force application mechanisms
Solution Approach 1:
The joint utilizes the user's own arm weight and gravity as the force source. When the arm is raised, gravity naturally provides the blocking force in the lowering direction without requiring additional actuators or power sources. The system serves itself by using the load it needs to support as the source of the supporting force.
Solution Approach 2:
The joint operates in periodic cycles between two states: allowing movement during arm lowering and blocking movement during arm raising. This periodic operation eliminates the need for continuous force application, reducing the complexity of the force generation system while maintaining effective support when needed.
3Force
If the joint is blocked to prevent arm lowering, then the support function is improved, but the ease of taking off the device or changing position deteriorates
Solution Approach 1:
The joint incorporates sensors that detect when the device should be removed or repositioned, providing feedback to switch from the first operating mode (blocked) to the second operating mode (unblocked). This feedback mechanism allows the system to automatically adapt to removal intentions, making device removal as easy as normal arm movement.
Solution Approach 2:
The joint dynamically switches between blocked and unblocked states based on operational needs. During normal use, it blocks arm lowering to provide support. When removal is intended, it transitions to an unblocked state, allowing free movement in both directions, thereby maintaining ease of operation throughout the device lifecycle.
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
Enables comfortable and efficient arm support by allowing movement in the desired direction without continuous force application, and can be easily unblocked when needed, reducing discomfort and improving usability during tasks with raised or extended arms.
Implementation Method 1
Due to the friction between the material of the wrap spring and the exterior of the shaft of the joint, a force is exerted on the wrap spring during a swivelling of the supporting system relative to main body
Implementation Method 2
the joint comprises a magnetorheological fluid and at least one magnetic field generation device, such as an electromagnet, which is arranged in such a way that a magnetic field generated by the electromagnet has an effect on at least one part of the magnetorheological fluid
Data Source
AI summary
The present invention comprises a device for supporting at least one arm of a user, wherein the device hasat least one main body (2) for arranging on a torso (4) of the user andat least one supporting device (8) for supporting the arm, wherein the supporting device (8) is arranged on the main body (2) via at least one joint (10) so that it can be moved relative to the main body (2),wherein, in every position within a predetermined position range of the supporting system (8) relative to the main body (2), the joint (10) allows a movement of the supporting system (8) relative to the main body (2) in a first direction and prevents a movement in an opposite second direction.