Landing Gear Washer Spring Assembly Against Creep and Vibration
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Solution Overview
Problem
Aircraft landing gear systems face issues with helical springs, which are susceptible to vibration, heavy, and prone to creep due to constant tensile stress, leading to potential unintentional retraction and reduced reliability.
Innovation Solution
The use of elastically deformable washers, such as conical or hemispherical washers, which offer improved aerodynamics, robustness, and impact resistance, and are designed to reduce creep by avoiding constant tensile stresses, with a sliding rod and disk arrangement to prevent buckling and torsional stress, and formed from materials like carbon fibre reinforced thermoplastic composites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If helical springs are used to provide deployment force, then the landing gear can be deployed, but the system becomes susceptible to vibration, aeroelastic vibrations, and creep due to constant tensile stress
Solution Approach 1:
The patent changes the fundamental parameter of spring geometry from a helical shape to a laminated washer configuration. This geometric transformation eliminates the bluff body shape that causes aeroelastic vibrations while maintaining the elastic energy storage function. The laminated structure also distributes stress differently, reducing creep susceptibility under constant load.
Solution Approach 2:
The patent employs composite material construction for the spring assembly, using multiple layers of elastic material bonded together in a laminated washer configuration. This composite approach provides both the necessary elastic properties and resistance to vibration and creep that single-material helical springs cannot achieve.
2Force
If helical springs are used, then deployment force is provided, but the weight of the spring assembly increases
Solution Approach 1:
The patent transforms the spring from a traditional helical geometry to a laminated washer configuration, which achieves the same force-providing function with reduced mass. The laminated structure efficiently stores and releases elastic energy while being lighter than an equivalent helical spring assembly.
3Reliability
If elastically deformable washers are used, then vibration and creep are reduced, but additional components (sliding rod, disk) are needed to prevent buckling and torsional stress
Solution Approach 1:
The patent introduces intermediary components - a sliding rod and a disk - that mediate between the elastically deformable washers and the external loads. The sliding rod prevents buckling by providing axial support, while the disk prevents torsional stress by constraining rotational movement. These intermediaries protect the washers from failure modes without compromising their vibration and creep resistance.
Solution Approach 2:
The spring assembly is segmented into distinct functional components: elastically deformable washers for energy storage, a sliding rod for buckling prevention, and a disk for torsional constraint. This segmentation allows each component to be optimized for its specific function while working together as an integrated system.
4Shape
If the number of washers is increased to customize spring length, then aerodynamic profile is improved, but manufacturing complexity increases
Solution Approach 1:
The spring is constructed from multiple discrete washer units that can be individually manufactured using standard processes and then stacked to achieve the required length and aerodynamic profile. This modular segmentation simplifies manufacturing compared to forming a single long helical spring, while allowing customization of the overall dimensions.
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 elastically deformable washer system enhances the reliability of aircraft landing gear by reducing the likelihood of creep and vibration-induced issues, providing a more stable and durable locking mechanism that maintains the gear in the deployed position without unnecessary stress, thus improving safety and performance.
Implementation Method 1
a spring comprising a plurality of elastically deformable washers arranged one behind the other along an elongate axis of the spring and compressed along said elongate axis
Implementation Method 2
The sliding rod may provide a structural support to the washers and may thereby prevent the spring from buckling in compression
Implementation Method 3
The disk may prevent any rotational movement from being transferred to the washers and may thereby prevent any torsional stress from being transferred to the washers
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
An aircraft landing gear comprising: a first member, a second member pivotally coupled to the first member, and a spring coupled to the first and second members, the spring comprising a plurality of elastically deformable washers, the spring being arranged to generate a biasing force between the first and second members to bias the first member toward a predetermined orientation relative to the second member.