Spherical Hinge Ankle Joint for Brace Misalignment Tolerance
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Solution Overview
Problem
Existing ankle joints for leg braces are difficult to install due to precise parallel mounting requirements, often leading to wear, binding, and stress, and are bulky and inflexible, making them unsuitable for pediatric patients and requiring separate adjustments for varying range of motion.
Innovation Solution
A spring-loaded spherical joint with a dome and mating cup, combined with an adjustable flexion range limiting system using threaded rods, allows for misalignment tolerance and compact design, enabling easy installation and adjustment to accommodate individual patient needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ankle joints are used with parallel mounting requirements, then control of plantar flexion and dorsiflection is achieved, but installation becomes difficult and time-consuming requiring precise parallel mounting surfaces
Solution Approach 1:
The patent employs a spherical hinge mechanism where a spherical dome on one mounting surface mates with a corresponding spherical recess on the other surface. This spherical geometry inherently accommodates non-parallel mounting surfaces by allowing rotational adjustment, eliminating the need for precise parallelism while maintaining reliable plantar flexion and dorsiflection control.
2Loss of time
If traditional ankle joints are installed without proper alignment, then installation time is reduced, but the joints are subject to greater wear, binding, and stress leading to cracks and possible failure
Solution Approach 1:
The spherical hinge design with a dome and mating recess allows for self-alignment during installation. The curved surfaces guide the components into proper orientation, ensuring that even if mounting surfaces are not initially parallel, the joint will seat correctly to minimize wear and stress concentrations that would lead to failure.
Solution Approach 2:
The spherical geometry provides a built-in tolerance mechanism that cushions against misalignment errors. By designing the joint with spherical surfaces that can rotate and adapt to non-ideal mounting conditions, the system preemptively protects against the harmful effects of improper installation without requiring additional alignment steps.
3Reliability
If bulky devices with definite settings are used for plantar flexion control, then control is provided, but the devices are difficult to fit in patient's shoe and difficult to adjust due to incremental settings only
Solution Approach 1:
The spherical hinge mechanism enables continuous adjustment of the ankle joint's range of motion by rotating the spherical dome within its mating recess. This dynamic adjustment capability allows practitioners to precisely tailor the plantar flexion and dorsiflection limits to each patient's specific needs, rather than being constrained to fixed incremental settings, while maintaining effective control.
4Adaptability or versatility
If devices with separate pieces for range of motion adjustment are used, then range of motion can be adjusted, but the devices are large and cause additional complications with smaller patients such as pediatric patients
Solution Approach 1:
The patent integrates the range of motion adjustment mechanism directly into the spherical hinge structure itself, rather than using separate external adjustment pieces. The spherical dome and recess combination serves both as the joint mechanism and as the adjustment system, eliminating the need for additional components and reducing overall device size to accommodate pediatric patients while maintaining full adjustability.
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 solution simplifies the installation process, reduces wear and stress on leg brace components, and provides a compact, adjustable ankle joint suitable for pediatric patients, allowing for precise setting of plantar and dorsiflexion limits without additional complications.
Implementation Method 1
A spring washer may be included to provide a preloading force to mate the cup to the dome.
Data Source
AI summary
A joint hinge and a leg brace having the joint hinge that includes a spring loaded spherical joint for coupling a proximal portion and a distal portion of the joint hinge. The spherical joint includes a dome on one portion coupled to a mating cup on the other portion. A wide-headed pin, typically a shoulder screw, captivates the cup against the sphere. A spring washer may be included to provide a preloading force to mate the cup to the dome. The spherical portion may be pressed or stamped into one portion of the hinge or fabricated separately and attached. In one embodiment, the dome is fabricated of sintered bearing material and may be impregnated with lubricant. The spherical joint functions in conjunction with an adjustable flexion range limiting system that include rods that are threaded and easy to screw in and out as the patient's range of motion changes.