Compliant Elbow Brace Nonlinear Torsion Spring
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Solution Overview
Problem
Conventional joint braces that reduce the range of motion often cause uncomfortable deceleration and pain by imposing abrupt mechanical stops, which can disrupt the healing process of joints during rehabilitation or injury recovery.
Innovation Solution
A brace configuration featuring a non-linear torsion spring mechanism that resists motion nonlinearly, requiring increasing torque as the user approaches the end of the rotational travel, thereby minimizing impulse and providing a cushioning force instead of a hard cut-off, thus reducing user discomfort and protecting the joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical stop is used to limit joint rotation, then the range of motion is effectively restricted, but abrupt deceleration and pain occur
Solution Approach 1:
The patent applies parameter changes by transitioning from a rigid mechanical stop (infinite stiffness) to a compliant mechanism with variable stiffness. The compliant mechanism's stiffness parameter changes continuously as it approaches the range of motion limit, providing a smooth transition from flexible to restrictive behavior. This resolves the contradiction by maintaining reliable ROM limitation while eliminating abrupt deceleration through progressive stiffness increase.
Solution Approach 2:
The compliant mechanism provides beforehand cushioning by gradually increasing resistance as the joint approaches the prescribed ROM limit. Instead of an abrupt stop, the mechanism accumulates elastic energy and provides a cushioning effect that smoothly decelerates the joint movement before reaching the limit, preventing pain and disruption to the healing joint.
2Stability of the object's composition
If a rigid brace structure is used to enforce ROM reduction, then joint stability is improved, but comfort and smooth motion control deteriorate
Solution Approach 1:
The brace structure transitions from rigid to compliant by changing the stiffness parameter of the motion-constraining mechanism. The compliant mechanism provides variable stiffness that adapts during motion, ensuring joint stability while maintaining motion smoothness and user comfort through progressive resistance rather than abrupt constraints.
Solution Approach 2:
The patent substitutes a rigid mechanical stop system with a compliant mechanism that uses elastic deformation and variable stiffness characteristics. This replacement maintains the essential function of ROM limitation and joint stability while dramatically improving ease of operation by providing smooth, comfortable motion control without abrupt deceleration.
3Object-affected harmful factors
If a compliant mechanism is used to reduce abrupt deceleration, then user comfort is improved, but the effectiveness of ROM limitation may be reduced
Solution Approach 1:
The compliant mechanism uses parameter changes to achieve both smooth deceleration and effective ROM limitation. By designing the mechanism with specific geometric parameters and material properties, the stiffness increases progressively as the joint approaches the prescribed ROM limit, ensuring that the full range of motion is effectively limited while maintaining user comfort through smooth motion control.
Solution Approach 2:
The mechanism transitions from a static rigid stop to a dynamic compliant system that adapts its stiffness characteristics during motion. The compliant mechanism's dynamic response provides smooth deceleration during normal movement while maintaining effective ROM limitation at the prescribed boundary, resolving the contradiction between comfort and effectiveness.
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 compliant motion-constraining brace effectively limits joint rotation with a cushioning force, reducing discomfort and protecting the joint from abrupt deceleration, while allowing controlled movement with minimal stiffness near the home position.
Implementation Method 1
A brace configuration featuring a non-linear torsion spring mechanism that resists motion nonlinearly, requiring increasing torque as the user approaches the end of the rotational travel
Implementation Method 2
The compliant motion-constraining brace effectively limits joint rotation with a cushioning force, reducing discomfort and protecting the joint from abrupt deceleration
Data Source
AI summary
One embodiment is directed to a brace for limiting motion of a joint of an appendage of that is interposed between a first appendage portion and a second appendage portion of a patient, comprising: an upper member removably coupleable to the first appendage portion, the upper member having proximal and distal ends; and a lower member removably coupleable to the second appendage portion, the lower member having proximal and distal ends; wherein the distal end of the upper member and proximal end of the lower member are coupled to form a movable joint that is substantially alignable with the joint of the patient, such that when the patient attempts to move his appendage and associated joint, motion is resisted at this joint in a nonlinear fashion.