Ball Joint for External Fixator with Wedge Locking
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Solution Overview
Problem
Existing external fixator systems face challenges in easily and securely connecting telescopic rods to rings, especially when the rings are not in ideal orientation, requiring complex adjustments and orientations that hinder the ease of use and stability of the rods.
Innovation Solution
A ball joint system comprising a sleeve, ring insert, and blocking element with complementary wedge surfaces and a spherical hollow ball portion, allowing radial and axial displacement to securely lock and unlock the rod within a ring fixator hole, enabling easy orientation and connection of struts to external fixator rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional rod-ring connection systems are used, then the structure is simple, but the ease of operation deteriorates because the rings must be in nearly perfect orientation to fit straight rods through ring holes
Solution Approach 1:
The connection system is divided into separate functional components: a ball joint assembly with spherical socket, a blocking element with wedge surfaces, and a ring insert. This segmentation allows each component to perform its specific function independently, enabling the rod to be connected to rings in different orientations without requiring precise alignment of the entire assembly.
Solution Approach 2:
The ball joint assembly acts as an intermediary mechanism between the rod and the ring. The spherical socket in the blocking element provides a universal connection point that can accommodate rods at various angles, while the wedge surfaces mediate the locking action between the blocking element and ring insert, eliminating the need for precise pre-alignment.
2Adaptability or versatility
If the rod is made telescopic for adjustability, then the adaptability improves, but the ease of operation worsens because the rod length cannot be easily changed while maintaining secure connection
Solution Approach 1:
The connection system is designed to be dynamic rather than static. The ball joint allows the rod orientation to be changed dynamically after insertion, and the wedge-based locking mechanism can be quickly engaged or disengaged to secure or release the rod. This dynamic design enables telescopic rods to be adjusted in length and reconnected without requiring complex procedures.
3Ease of operation
If the ring insert and blocking element are fixed in position, then the manufacturing precision is high, but the ease of operation deteriorates because the joint cannot be easily tightened or loosened
Solution Approach 1:
The ring insert and blocking element are pre-positioned within the ball joint assembly during manufacturing. Their relative positions are predetermined by the spherical socket geometry and wedge surface configurations. This preliminary positioning ensures that when the assembly is installed, the components are already aligned to facilitate easy tightening through the wedge action without requiring complex adjustment procedures.
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 ball joint system allows for quick and secure adjustment of the telescopic rod's orientation and connection to external fixator rings, reducing the complexity of fitting rods into holes and maintaining stability with a single tightening operation, while self-locking properties ensure secure fixation.
Implementation Method 1
Ring insert and blocking element have complementary wedge surfaces allowing a relative radial displacement of ring insert and blocking element one against the other to enlarge the diameter of the combined circumferential surface for blocking the ball joint inside such a hole
Implementation Method 2
sleeve comprises a spherical hollow ball portion with concentrical inner and outer spherical portions, wherein the outer spherical portion engages a complementary spherical socket of blocking element and wherein the inner spherical portion is engaged by a ball nut
Implementation Method 3
said ball nut is in an axial displaceable relationship with a connection element extending in and through sleeve, blocking element and ring insert, wherein said radial displacement and axial displacement are activated by said connection element
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A ball joint (12) comprises a sleeve (20) in engagement (21) with a rod of a strut for an external fixator and a ring insert (50) and a blocking element (40) having a combined circumferential surface (45,55) introducible into a hole of an external fixator element and having complementary wedge surfaces (42,52) allowing radial displacement of ring insert (50) relative to blocking element (40) to enlarge the diameter of the combined circumferential surface (42,52) for blocking the ball joint (12) inside the hole. Additionally sleeve (20) comprises a spherical hollow ball portion (26) with concentrical inner (26) and outer (24,25) spherical surfaces, wherein the outer spherical surface (24,25) engages a complementary spherical socket (41) of blocking element (40) and wherein the inner spherical surface (26) is engaged by a ball nut (30) i.e. a nut comprising a polygon cylinder together with a spherical portion. A connection element (60) extends through sleeve (20), blocking element (40) and ring insert (50), and when activated displaces ball nut (30) axially such as to cause said radial displacement.