External Fixator Joint With Frustum Friction for Bone Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing external fixators for bone fractures lack efficient mechanisms for aligning and securely fixing bone fragments in a desired position without requiring continuous external force and allow only angular adjustments in predefined steps.
Innovation Solution
The external retaining device features rotatable rod holders with frustum-shaped, mirror-opposite friction surfaces that generate high friction when clamped, allowing continuous angular adjustability and secure fixation of bone fragments using a tensioning device, which can be adjusted to desired friction levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frustum-shaped friction surfaces are clamped together with high tensioning force, then rotation prevention is improved, but the device complexity increases
Solution Approach 1:
The patent employs frustum-shaped (truncated conical) friction surfaces instead of flat surfaces. The curved conical geometry creates a wedge effect where the normal force from tensioning generates a larger friction force tangential to the rotation axis, providing superior rotation prevention with the same tensioning force compared to flat surfaces.
Solution Approach 2:
The joint is divided into two separate rod holders that can be independently adjusted and clamped. Each rod holder contains friction surfaces that can be tensioned separately via individual tensioning devices, allowing modular adjustment and simplifying the overall device operation while maintaining high reliability.
2Manufacturing precision
If continuous external force is applied to maintain bone fragment alignment, then positioning precision is improved, but the ease of operation deteriorates
Solution Approach 1:
The friction surfaces are designed to maintain bone fragment positioning through self-generating friction forces. Once the tensioning devices are adjusted to create the desired friction, the system maintains positioning precision automatically without requiring continuous external force or active control, making the device easy to operate after initial setup.
Solution Approach 2:
The tensioning force parameter can be adjusted to control the friction force level. By changing the tensioning parameter, the system achieves both precise positioning (through controlled friction) and ease of operation (through adjustable, maintainable force levels without continuous external intervention).
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 precise alignment and secure fixation of bone fragments without continuous external force, allowing smooth angular adjustments and reliable prevention of rotation, with adjustable friction force for precise positioning.
Implementation Method 1
the clamped-together friction surfaces generate high friction, which holds the two clamped-together rod holders of the joint to prevent rotation
Implementation Method 2
As a result of wedge action, the clamped-together friction surfaces generate high friction
Data Source
AI summary
A joint of an external retaining device for fragments of a bone (external fixator) with circular ribs and grooves having a V-shaped cross-section, the flanks of which form frustum-shaped friction surfaces, which enable a high friction force to prevent rotation of the joint, and thereby prevent inadvertent displacement of the retaining device, and enable adjustment of the retaining device using an adjustable friction force for aligning the fragments of the bone.