External Fixator Bolt With Segmented Pin Opening
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Solution Overview
Problem
Existing bolts used in external fixators for bone deformities or fractures often experience gaping and structural failure under high tightening forces due to their drop-shaped openings and plane surface clamping, which complicates the clamping of pins with different diameters and may lead to misalignment during tightening.
Innovation Solution
A bolt design featuring a pin opening with two edges extending in the same direction as the opening, which clamps the pin or wire with the edges and a surface of the external fixator plate, allowing for secure clamping of pins with different diameters and maintaining alignment during tightening, with the edges optionally forming a groove or ridge within the pin opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a drop-shaped opening is used in the bolt to accommodate different pin diameters, then adaptability to different pin sizes is improved, but the structural strength and stability deteriorate due to gaping and potential breakage under tightening forces
Solution Approach 1:
The pin opening is divided into multiple functional elements: at least two edges extending along the opening direction to contact the pin, and a clamping surface perpendicular to the opening direction. This segmentation allows the opening to accommodate different pin diameters through the edges while distributing tightening forces across multiple contact points (edges and surface), preventing gaping and structural failure.
2Device complexity
If plane surfaces are used to clamp the pin, then the clamping mechanism is simple, but the connection reliability deteriorates under extraordinary tightening forces
Solution Approach 1:
The clamping mechanism employs local quality differentiation: the edges provide linear contact points along the pin opening direction, while the clamping surface provides a perpendicular contact face. This local differentiation of contact geometry enhances the reliability of the connection under tightening forces by distributing stress across multiple zones with different functional characteristics, preventing both gaping and breakage.
3Ease of operation
If the bolt is moved along its middle axis during tightening, then pre-alignment of the pin is improved, but maintaining constant orientation throughout tightening becomes difficult
Solution Approach 1:
The pin opening geometry is designed to perform preliminary alignment action before full tightening. The at least two edges extending along the opening direction automatically guide and align the pin as the bolt approaches, ensuring correct orientation is established prior to application of significant clamping force. This preliminary alignment action maintains stability throughout the tightening process.
Data Source
Figure 1~2
Figure 3~4
AI summary
A bolt (1) is adapted to clamp a pin (2) to an external fixator system. Said bolt (1) comprises a shaft having a threaded section (10), a head section (11) and a pin opening (13) that is arranged opposite the threaded section (10) and accommodates and clamps a pin (2) or a wire to a plate (3) of an external fixator. The plate (3) comprises at least one opening (30) which accommodates the shaft and a surface (31) against which the pin or the wire is clamped by means of the bolt (1). Said pin opening (13) comprises at least two edges (15) extending essentially along the same direction as the pin opening (13) such that the pin (2) or wire to be clamped is contact with said edges (15).