Leaf Spring Locking Device for Aircraft Landing Gear
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Solution Overview
Problem
Aircraft undercarriages with coil springs for locking in the deployed position are expensive, heavy, and require high forces for retraction, necessitating robust actuators and posing manufacturing challenges.
Innovation Solution
The use of spring blades subjected to axial compression to maintain alignment of the undercarriage links, which buckles to provide a consistent locking force, reducing the forces needed for deployment and retraction, and are lighter and cheaper to produce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coil springs are used to lock the undercarriage in the deployed position, then the undercarriage can be held securely in position, but the weight and cost increase significantly
Solution Approach 1:
The patent changes the physical state and configuration of the spring element from a conventional coil spring to a flattened spring configuration. This parameter change allows the spring to achieve the necessary locking force while significantly reducing weight and cost, as the flattened geometry provides higher stiffness-to-weight ratio and requires less material volume.
2Reliability
If coil springs are used to lock the undercarriage, then secure positioning is achieved, but the cost increases
Solution Approach 1:
The spring element is transformed from a coil configuration to a flattened configuration, changing its geometric parameters. This allows the use of simpler manufacturing processes such as laser cutting and bending from flat metal sheets, eliminating the need for complex coil winding operations, thereby reducing manufacturing cost while maintaining locking reliability.
3Reliability
If coil springs are used to assist in moving the undercarriage to deployed position, then the undercarriage can be locked in position, but large additional forces are required for retraction
Solution Approach 1:
The spring element's geometric parameters are changed from coiled to flattened configuration, which fundamentally alters its force-displacement characteristics. The flattened spring provides a more linear and predictable force curve that can be better matched to the actuator's capabilities, reducing the peak forces required during retraction while maintaining adequate locking force during deployment.
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 spring blade system effectively locks the undercarriage in the deployed position with minimal force variation, reducing the load on the drive actuator and offering a cost-effective, lightweight solution.
Implementation Method 1
at least one spring for elastically urging the hinges of the first and second links into a generally aligned position
Implementation Method 2
Compressing the blade axially causes it to buckle in such a manner that the force that needs to be delivered for breaking the alignment of the links varies little while the blade is buckling
Data Source
AI summary
An aircraft undercarriage comprising: a leg connected to an aircraft structure to be movable between a deployed position and a retracted position; a brace member for holding the leg in its deployed position and comprising a first rod hinged to the aircraft structure and a second rod hinged to the first link and to the leg; a stabilizer member for holding the first and second rods in an aligned position and comprising a first link and a second link that are hinged to each other, with at least one of them being hinged to the brace member; and a spring for elastically urging the hinges of the first and second links into a generally aligned position.The spring comprises at least one spring blade arranged to be subjected to an axial compression force when the first and second links leave the generally aligned position.