Conductive Self-Lubricating Landing Gear Bushing for Lightning Current
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Solution Overview
Problem
Existing landing gear bushings for aerospace applications require periodic maintenance and sacrifice electrical conductivity for long service life, as they often use non-conductive materials like PTFE for self-lubrication, which impedes the conduction of electrical currents from lightning strikes or static electricity.
Innovation Solution
A bushing system with self-lubricating liners made from PTFE or PTFE fibers, integrated with an electrically conductive path and a wear-resistant coating, allowing for maintenance-free operation while maintaining electrical conductivity, suitable for withstanding lightning strikes and static electricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If self-lubricating liners made from PTFE are used in bushings, then maintenance-free operation and long service life are achieved, but electrical conductivity is lost
Solution Approach 1:
The bushing employs a composite structure combining PTFE self-lubricating liner with electrically conductive components (metal housing, metal shaft, and conductive grease). The PTFE liner provides maintenance-free operation while the conductive grease filled in cavities and the metal components ensure electrical conductivity, resolving the contradiction between durability and electrical functionality
Solution Approach 2:
The PTFE liner is positioned specifically at the bearing surface where lubrication is needed, while electrically conductive materials are placed in specific locations (housing, shaft, grease in cavities) where electrical conduction is required. This localized assignment of different material properties allows the bushing to simultaneously achieve maintenance-free operation and electrical conductivity
2Reliability
If grease lubricated bushings with direct metal contact are used, then electrical conductivity is maintained, but periodic maintenance and re-greasing are required
Solution Approach 1:
The PTFE liner is integrated directly into the bushing structure, providing self-lubrication without requiring external grease application or maintenance. The liner's inherent lubricating properties enable the bushing to operate maintenance-free throughout its service life, eliminating the periodic re-greasing required by traditional grease-lubricated bushings
Solution Approach 2:
The combination of PTFE liner with metal housing and shaft creates a composite bushing that achieves both maintenance-free operation through the PTFE's self-lubricating properties and electrical conductivity through the metal components and conductive grease, surpassing the limitations of single-material bushings
3Ease of operation
If non-conductive PTFE bushings are used, then maintenance-free operation is achieved, but electrical current conduction from lightning strikes is impeded
Solution Approach 1:
The bushing uses a composite structure where the PTFE liner provides self-lubrication and the electrically conductive grease filled in cavities and metal components provide electrical conductivity. This allows the bushing to be maintenance-free while still conducting electrical currents from lightning strikes or static electricity, preventing the harmful effects of electrical insulation
Solution Approach 2:
The electrically conductive grease acts as an intermediary material that bridges the non-conductive PTFE liner and the metal housing/shaft. It fills the cavities and provides a conductive path for electrical current while allowing the PTFE liner to maintain its self-lubricating properties, thus mediating between the conflicting requirements of electrical conduction and maintenance-free operation
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 provides a durable, maintenance-free solution that effectively conducts electrical currents equivalent to lightning strikes without damage, with a maximum wear of 0.0033mm after 25,000 cycles across a wide temperature range, ensuring reliable operation in aircraft landing gear.
Implementation Method 1
one or more cylindrical self-lubricating liners each of which are disposed in a respective one of the cylindrical recesses
Implementation Method 2
The bushing system includes 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
Figure 3
Figure 4
AI summary
A bushing for aircraft landing gear (100) includes a cylindrical wall (12) having an interior surface (21, 23) defining a bore (20) extending between a first and second axial end (14, 16) thereof and a cylindrical recess (24, 24') extending into the interior surface (21, 23). The bushing includes a cylindrical self-lubricating liner (22, 22') which is substantially flush with the interior surface is disposed in the recess. The cylindrical wall (12) includes a flange (26) that has an annular recess that receives an annular self-lubricating liner (28) that has a planar axial bearing surface (28X). The planar axial bearing surface (28X) is coplanar with an inboard axial surface of the flange (26). The bushing has an electrically conductive path (34) that conducts electrical current and that extends around the cylindrical self-lubricating liner (22, 22') and the annular self-lubricating liner (28) and through the cylindrical wall (12) and the flange (26).