Aircraft Landing Gear Locking Device Cam Mechanism
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Solution Overview
Problem
Existing locking devices for steerable axles in aircraft landing gear are prone to jamming and noise due to the need for moving locking elements into mating recesses, which can be unreliable and noisy in operation.
Innovation Solution
A locking device with a movable member and follower that transfers steering force to the axle, allowing the axle to be locked or unlocked by moving the movable member between configurations, using a cam surface and follower to prevent back-driving and enable steering in both directions, with a biasing mechanism to maintain the axle in a fixed orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If locking elements move into mating recesses to lock the axle, then the locking function is achieved, but the device is prone to jamming and noise
Solution Approach 1:
Instead of moving locking elements into recesses to achieve locking, the patent inverts the approach by using a cam surface that passively locks the follower through its geometric profile. The cam surface shape inherently prevents back-driving and locking occurs without active insertion into recesses, thereby eliminating jamming and noise while maintaining reliable locking function.
Solution Approach 2:
The patent replaces the traditional mechanical locking system with recesses and locking elements with a cam-based system. The cam surface uses geometric constraints and force distribution to achieve locking without the need for mating recesses, substituting a smoother mechanical interaction that avoids jamming and reduces noise.
2Reliability
If a locking actuator is used to lock the axle at a predefined extension state, then the locking orientation is achieved, but the device complexity increases
Solution Approach 1:
The cam surface serves multiple functions simultaneously: it provides the locking mechanism, guides the follower movement, prevents back-driving, and defines the locking orientation. This multi-functionality eliminates the need for separate locking actuators and recesses, reducing device complexity while maintaining reliable locking.
Solution Approach 2:
The cam-follower mechanism is self-actuating through the natural movement of the movable member. The cam surface geometry automatically provides locking and prevents back-driving without requiring additional actuators or complex control systems, making the system self-sufficient and simpler in design.
3Reliability
If a wedge is movable between housed and removed positions to lock or allow pivoting, then the locking function is achieved, but the device is prone to jamming and noise
Solution Approach 1:
The patent replaces the wedge-based locking system with a cam surface mechanism. The cam surface provides continuous geometric constraints on the follower, eliminating the need for wedges that move between housed and removed positions. This substitution removes the sources of jamming and noise associated with wedge insertion and extraction while maintaining effective locking.
Solution Approach 2:
Instead of using a wedge that actively engages and disengages from a slot, the patent inverts the approach by using a cam surface that continuously guides and constrains the follower. The locking action is achieved through the cam profile geometry rather than through active engagement of separate elements, thereby eliminating jamming and noise.
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 solution provides a reliable and quiet locking mechanism that prevents jamming and noise, allowing the axle to be securely locked or steered as needed, enhancing the operational stability and efficiency of the landing gear.
Implementation Method 1
the locking device being arranged such that movement of the movable member from the first configuration to the second configuration causes corresponding movement of the follower so as to transfer a steering force to the axle, through the follower, which causes the axle to rotate
Implementation Method 2
with a biasing mechanism to maintain the axle in a fixed orientation
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A landing gear (70) for an aircraft, the landing gear including an axle (14) pivotally connected to a bogie beam (12) and a locking device (11c), the locking device being arranged to couple the axle to the bogie beam, the locking device including a movable member and a follower (22), the movable member (60) being arranged to be moved by an actuator between first and second configurations, the locking device being arranged such that movement of the movable member towards the second configuration causes corresponding movement of the follower so as to transfer a steering force to the axle through the follower which causes the axle to rotate in a first direction, wherein, with the movable member in the first configuration, the locking device is arranged with the follower in a first configuration that inhibits the movable member being moved by an external force applied to the axle and, with the movable member in the second configuration, the locking device is arranged with the follower in a second configuration that permits the movable member to be moved by an external force applied to the axle.