Aircraft Landing Gear Ground Lock With Mass-Balanced Pivot Stability
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Solution Overview
Problem
Existing vehicle assembly locks, such as those in aircraft landing gear, are prone to unintentional unlocking due to movement, leading to suboptimal geometry and potential accidents, and require substantial biasing devices that can be heavy and inefficient.
Innovation Solution
A lock design featuring a movably mounted first part with a swept volume and a rotatable second part with a bearing surface, where the effective bearing radius is greater than the distance between the center of mass and the pivot axis, reducing the likelihood of pivotal movement and allowing for reduced biasing force requirements, with a biasing device to maintain the lock in a specific condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ground lock is provided to inhibit unlocking of the down lock while on the ground, then safety is improved, but the lock is prone to unintentional movement due to vehicle movement
Solution Approach 1:
The second part is mass balanced about the pivot axis, with the center of mass positioned at or near the pivot axis. This counterbalances the effects of vehicle movement and gravitational forces, preventing unintentional pivoting of the lock mechanism while maintaining its locked or unlocked state.
Solution Approach 2:
The bearing surfaces are positioned to create an effective bearing radius greater than the distance from the center of mass to the pivot axis. This dynamic geometric relationship ensures that friction forces at the bearing surfaces automatically resist pivoting moments caused by vehicle movement, providing passive stability without additional active control mechanisms.
2Stability of the object's composition
If a substantial biasing device such as a spring is provided to maintain the lock in a particular condition, then the lock stability is improved, but the size and mass of the biasing device increases
Solution Approach 1:
By mass balancing the second part about the pivot axis, the design eliminates the need for substantial biasing forces. The center of mass is positioned at or near the pivot axis, so gravitational forces create minimal moment about the pivot, reducing or eliminating the requirement for heavy springs or other biasing devices.
Solution Approach 2:
The bearing geometry is designed so that the effective bearing radius exceeds the center of mass offset from the pivot axis. This creates sufficient friction moment at the bearing surfaces to resist pivoting due to vehicle movement, providing stability through geometric design rather than substantial elastic biasing forces.
3Force
If the second part is positioned with a larger bearing radius, then the friction moment increases to resist movement, but the distance from center of mass to pivot axis also increases
Solution Approach 1:
The second part is designed with its center of mass positioned at or near the pivot axis, minimizing the center of mass offset. This counterbalances the increased moment arm effect of the larger bearing radius, ensuring that gravitational forces do not create excessive pivoting moments while still benefiting from the increased friction moment provided by the larger bearing radius.
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 design reduces the likelihood of unintentional locking or unlocking, minimizes the need for large biasing devices, and allows for optimal positioning and operation of the ground lock, enhancing safety and efficiency.
Implementation Method 1
the one or more bearing surfaces define an effective bearing radius which is greater than the distance between the centre of mass of the second part and the pivot axis
Data Source
Figure 1
Figure 2a~2b
Figure 3~4
AI summary
A mechanical lock (10) for a vehicle assembly such as an aircraft landing gear assembly. The lock is either pivotally mounted and substantially mass balanced, or part of an aircraft landing gear assembly (30) and arranged to be mechanically operated from the ground by a mechanical actuation device.