Aircraft Shock Strut Percolation Seals for Fluid Switching
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Solution Overview
Problem
Aircraft shock struts with mixed air/oil chambers face inefficiencies due to gas and oil leakage when retracted, leading to delayed fluid switching and reduced performance during landing, exacerbated by cold temperatures, which can result in increased landing loads and potential damage.
Innovation Solution
The implementation of a shock strut system with first and second percolation seals that restrict fluid flow between chambers, controlled by a fluid source and conduit, to prevent gas and oil from switching places when retracted, ensuring efficient fluid distribution upon extension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shock strut is retracted to a position above horizontal for a period of time, then the gas and oil switch chambers due to gravity, but the insufficient flow area prevents timely switching back, causing delayed landing gear readiness
Solution Approach 1:
The patent employs dynamic seals that can change their sealing characteristics based on the shock strut's position and operating conditions. The seals transition between different sealing states to allow rapid fluid switching when needed while preventing percolation during retraction, resolving the time delay contradiction.
Solution Approach 2:
The patent changes the flow area parameter dynamically by using seals with variable sealing characteristics. When the shock strut is extended, the seals provide sufficient flow area for rapid gas and oil switching. When retracted, the seals adjust to restrict percolation, thus optimizing performance across different operational phases.
2Reliability
If percolation seals are added to restrict fluid flow between chambers, then gas and oil distribution is maintained, but the device complexity increases
Solution Approach 1:
The percolation seals are designed to automatically respond to pressure differentials and gravitational forces without requiring external control systems. The seals self-adjust their sealing characteristics based on the shock strut's position and fluid pressure, maintaining reliable fluid distribution while avoiding complex control mechanisms.
Solution Approach 2:
The patent introduces percolation seals as intermediary elements between the upper and lower chambers. These seals act as mediators that selectively control fluid flow based on operating conditions, providing reliable fluid distribution while adding minimal structural complexity compared to active control systems.
3Reliability
If the shock strut operates with gas in the lower chamber due to percolation, then the hydraulic damping characteristics deteriorate, but increasing the flow area to prevent percolation increases device complexity
Solution Approach 1:
The percolation seals dynamically adjust their flow restriction characteristics based on the shock strut's operational phase. During retraction, they restrict flow to prevent percolation. During extension, they allow sufficient flow area for rapid gas and oil switching, maintaining hydraulic damping performance without requiring complex flow restriction mechanisms.
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
This solution ensures the shock strut operates efficiently by maintaining the optimal gas and oil distribution, reducing the risk of damage and enhancing hydraulic damping characteristics, even at cold temperatures, by inflating and deflating the seals based on the landing gear's position.
Implementation Method 1
a first percolation seal configured to restrict a first flow of fluid between the shock strut cylinder and the rebound chamber, and a second percolation seal configured to restrict a second flow of fluid between the shock strut cylinder and the shock strut piston
Implementation Method 2
the fluid source is configured to inflate and deflate the first percolation seal and the second percolation seal via the conduit, the first percolation seal restricting the first flow of fluid when inflated, and the second percolation seal restricting the second flow of fluid when inflated
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A shock strut is disclosed herein. The shock strut includes a shock strut cylinder (204), a shock strut piston (206) slidably disposed within the shock strut cylinder (204), a rebound chamber (270) disposed within the shock strut cylinder (204) and adjacent the shock strut piston (206), a first percolation seal (250) configured to restrict a first flow of fluid between the shock strut cylinder (204) and the rebound chamber (270), and a second percolation seal (252) configured to restrict a second flow of fluid between the shock strut cylinder (204) and the shock strut piston (206).