Conductive Self-Lubricating Bushing for Lightning-Safe Landing Gear
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Solution Overview
Problem
Existing landing gear bushings for aerospace applications require periodic maintenance for lubrication and do not provide adequate electrical conductivity, which can lead to damage from lightning strikes or static electricity.
Innovation Solution
A self-lubricated bushing system with cylindrical and annular liners made of PTFE or PTFE-infused materials, integrated with an electrically conductive path through the cylindrical wall and flange, allowing for maintenance-free operation and effective electrical current conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grease lubricated bushings are used to provide electrical conductivity through direct metal contact, then electrical current conduction is improved, but periodic maintenance and re-greasing are required which reduces reliability
Solution Approach 1:
The bushing incorporates self-lubricating liners made of PTFE or PTFE-infused materials that provide automatic lubrication without requiring external intervention or periodic re-greasing. The liners are disposed in recesses within the bushing structure, with radially inward facing surfaces substantially flush with the bore interior surface, enabling maintenance-free operation while maintaining electrical conductivity through the conductive path.
2Duration of action of stationary object
If permanent or semi-permanent lubrication is added to extend bushing life, then service life is improved, but electrical conductivity is sacrificed
Solution Approach 1:
The bushing structure incorporates distinct zones with different properties: self-lubricating liners made of PTFE or PTFE-infused materials are disposed in cylindrical recesses to provide lubrication, while an electrically conductive path extends around these liners and through the cylindrical wall and flange to maintain electrical conductivity. This local differentiation allows each region to perform its specific function optimally.
Solution Approach 2:
The bushing employs composite construction combining PTFE or PTFE-infused self-lubricating liner materials with electrically conductive materials (such as aluminum-bronze alloy) for the cylindrical wall and flange. The self-lubricating liner provides maintenance-free operation, while the conductive path ensures electrical conductivity, creating a multi-material system that achieves both objectives simultaneously.
3Ease of operation
If self-lubricating liners are used to eliminate maintenance, then ease of operation is improved, but electrical conductivity path may be interrupted
Solution Approach 1:
The bushing is segmented into functional zones: cylindrical recesses containing self-lubricating liners are positioned at specific locations, while the electrically conductive path extends around these liners and through the cylindrical wall and flange. This segmentation allows the lubrication function and electrical conduction function to coexist without interference, with the conductive path routed to bypass the non-conductive PTFE liner regions.
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 bushing system maintains electrical conductivity while eliminating the need for re-lubrication, effectively dissipating electromagnetic energy from lightning strikes and static discharge without causing damage.
Implementation Method 1
one or more cylindrical self-lubricating liners each being disposed in a respective one of the cylindrical recesses
Implementation Method 2
an electrically conductive path that is configured to conduct electrical current, preferably an electrical current that has a voltage equivalent to that of a lightning strike
Data Source
Figure 1~2
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Figure 4
AI summary
A bushing for aircraft landing gear includes a cylindrical wall having an interior surface defining a bore extending between a first and second axial end thereof and a cylindrical recess extending into the interior surface. The bushing includes a cylindrical self-lubricating liner which is substantially flush with the interior surface is disposed in the recess. The cylindrical wall includes a flange that has an annular recess that receives an annular self-lubricating liner that has a planar axial bearing surface. The planar axial bearing surface is coplanar with an inboard axial surface of the flange. The bushing has an electrically conductive path that conducts electrical current and that extends around the cylindrical self-lubricating liner and the annular self-lubricating liner and through the cylindrical wall and the flange.