Shock Strut Variable-Area Metering for Fluid Damping Control
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Solution Overview
Problem
Existing shock struts in aircraft landing gear systems face inefficiencies in controlling the rate of fluid flow and energy absorption, leading to suboptimal performance in managing transient forces during landing, taxiing, and takeoff.
Innovation Solution
A shock strut variable-area metering unit with a metering pin analog and translation shaft that translates within a metering unit housing, featuring variable area flutes and a return spring, to control fluid flow and energy absorption by altering the orifice area based on load pressure and differential pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional metering pin is used to control fluid flow rate, then the shock strut can effectively manage transient forces, but the overall weight of the shock strut increases
Solution Approach 1:
The patent extracts the metering function from the traditional metering pin and relocates it to a variable area orifice in the metering unit. This allows the metering pin to be removed or significantly reduced in size, thereby reducing the overall weight of the shock strut while maintaining the fluid flow control function through the variable area orifice geometry
Solution Approach 2:
The patent uses hydraulic principles by implementing a variable area orifice through which hydraulic fluid flows. The orifice area varies with piston position, providing automatic metering control without requiring a heavy mechanical metering pin. The hydraulic system leverages fluid pressure and flow characteristics to achieve the desired damping control
2Device complexity
If a fixed orifice area is used in the metering unit, then the structure is simpler, but the control over fluid flow rate and energy absorption becomes less effective
Solution Approach 1:
The patent implements a dynamic orifice area that changes with piston position during compression and extension. The variable area orifice is designed such that the open area varies continuously as the piston moves, providing adaptive fluid flow control that responds to changing load conditions. This dynamic characteristic improves energy absorption control while maintaining a relatively simple overall structure
Solution Approach 2:
The patent changes the geometric parameter of the orifice area dynamically during operation. By designing the orifice with a variable cross-sectional area that depends on piston position, the system achieves effective fluid flow rate control without complex mechanical components. The parameter change is achieved through the interaction between the piston and the orifice geometry
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
Enhances the control of fluid flow and energy absorption, reducing the weight of the shock strut while maintaining effective dampening and energy return, thus improving the performance and safety of aircraft landing gear systems.
Implementation Method 1
a trapped volume of gas is compressed as the shock strut is axially compressed, and a volume of oil is metered through a metering orifice. The gas acts as an energy storage device, similar to a spring
Implementation Method 2
The gas acts as an energy storage device, similar to a spring, so that upon termination of a compressing force the shock strut returns to its original length
Implementation Method 3
Shock struts also dissipate energy by passing the oil through the orifice so that as the shock absorber is compressed or extended, its rate of motion is limited by the damping action from the interaction of the orifice and the oil
Data Source
AI summary
A metering unit is provided. The metering unit includes a metering pin analog and a translation shaft. The metering pin analog is configured to translate about the translation shaft in a first direction in response to a load pressure acting on an annular region of a bottom portion of the metering pin analog. The metering pin analog is configured to translate about the translation shaft in a second direction opposite the first direction in response to the load pressure ceasing.