Variable Ankle Rod Coupler for External Fixation Stability
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Solution Overview
Problem
Existing external fixation systems, such as those described in U.S. Pat. No. 5,653,707 and US Patent Application No. 2007/0249979 A1, lack stability when subjected to large forces and fail to securely fix rods in a common plane, especially when the angle between the rods' longitudinal axes is significant, due to reliance on force fits and spherical bearings that can slip.
Innovation Solution
A rod coupler with two clamping jaws and locking means, featuring grooves on the clamping surfaces that form apertures for receiving rods, allowing for secure locking and adjustable ankle position, with the grooves' angles optimized for enhanced stability and versatility, enabling rods to be coupled in V- or Y-configurations and allowing for adjustable bridging lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If force fit connections are used to join bars, then the device can be assembled easily, but the stability and reliability deteriorate under large forces
Solution Approach 1:
The connector is divided into multiple independent hexagonal apertures, each capable of receiving and securing a bar independently. This segmentation allows each bar connection to be optimized individually while maintaining overall system ease of assembly.
Solution Approach 2:
The hexagonal cross-section of the bars and corresponding apertures provides geometric interlocking that prevents slippage under load. The specific hexagonal geometry creates multiple contact points that distribute forces evenly, enhancing stability while maintaining simple assembly through straightforward insertion.
2Ease of operation
If bars are connected side-by-side through a connector, then assembly is simplified, but the ability to secure bars in a common plane deteriorates
Solution Approach 1:
The hexagonal apertures are positioned and oriented asymmetrically within the connector body, allowing bars to be arranged in specific spatial configurations. This asymmetric design enables the connector to guide bars into precise alignments, including common plane arrangements, while maintaining ease of assembly through the standardized hexagonal interface.
3Adaptability or versatility
If spherical bearings are used with force fit, then the device can accommodate various configurations, but stability deteriorates when subjected to large forces
Solution Approach 1:
The hexagonal geometry of the bars and apertures provides inherent mechanical interlocking that prevents spherical bearing slippage. The multiple flat surfaces of the hexagonal cross-section create distributed contact points that lock the bearings in place, maintaining both configuration flexibility and stability under large forces.
4Length of stationary object
If the angle between bar longitudinal axes is increased, then the frame can bridge longer distances, but the stability of the connection deteriorates
Solution Approach 1:
The asymmetric positioning and orientation of hexagonal apertures within the connector allow accommodation of various angles between connected bars. The hexagonal geometry maintains mechanical interlocking and stability even at larger angles, enabling the frame to bridge longer distances while preserving connection integrity.
Data Source
AI summary
The rod coupler according to the present invention comprises two clamping jaws and locking means for locking said clamping jaws against one another. Each clamping jaw comprises an outside surface and a clamping surface, the latter providing at least a first and a second groove. Each groove runs laterally from a different part of the outside surface extending into the rod coupler, wherein longitudinal axis of the first groove and the second groove include an angle that is equal to or less than 160 degrees. Opposing grooves form an aperture. The apertures are adapted for receiving a rod if the locking means is released. Clamping jaws that are locked by the locking means clamp the rods received in said apertures.