Aircraft Door Interlock Cam Assembly for Arming Sequence Control
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Solution Overview
Problem
Existing aircraft door emergency support systems lack efficient mechanisms for controlling their active or inactive conditions, leading to potential misuse or malfunction during emergencies.
Innovation Solution
An interlock assembly with a shaft, interlock cam, and auto-disarm cam, allowing for selective configuration of the emergency support system to be armed or disarmed, preventing inadvertent activation during door opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the emergency support system is always active, then emergency evacuation capability is improved, but the risk of accidental activation and misuse increases
Solution Approach 1:
The system requires preliminary actions (rotating the interior door handle to unlock the shaft, then rotating the exterior door handle to disengage the auto-disarm cam) before the emergency support system can be activated. This preliminary sequence ensures that only intentional actions, not accidental movements, will arm the system.
Solution Approach 2:
The interlock cam and locking sector create a preliminary blocking mechanism that prevents the shaft from rotating into the armed position unless the door is properly closed and latched. This anti-action is built into the mechanical structure to counteract accidental activation attempts.
2Object-affected harmful factors
If the emergency support system is always inactive, then the risk of misuse is reduced, but the response time during actual emergencies increases
Solution Approach 1:
The system is pre-configured with the shaft in the armed position during normal door closure, requiring only a simple disengagement action (rotating the exterior door handle) during emergencies rather than requiring activation steps. This preliminary arming state enables rapid response while maintaining safety during normal operations.
Solution Approach 2:
The system dynamically transitions between armed and disarmed states based on door position and handle rotation, allowing the emergency support system to be ready for immediate activation when needed while remaining inactive during normal operations. The mechanical interlocks automatically adjust the system state based on operational conditions.
3Device complexity
If a simple on/off control mechanism is used, then the device complexity is reduced, but the precision of control over emergency system activation is worsened
Solution Approach 1:
The control mechanism is segmented into distinct functional components: the interior door handle with interlock first portion for unlocking the shaft, the exterior door handle with auto-disarm second portion for disengaging the cam, and the shaft with interlock and auto-disarm cams. Each segment performs a specific function in the activation sequence, providing precise control while keeping individual components relatively simple.
Solution Approach 2:
The shaft acts as an intermediary mechanical element that transmits and coordinates the actions of both door handles. The interlock cam and auto-disarm cam on the shaft mediate between the handle rotations and the final armed/disarmed state, ensuring precise control through mechanical coordination rather than complex electronic control.
4Ease of operation
If the door handles are independently rotatable, then the ease of operation is improved, but the reliability of preventing inadvertent activation is worsened
Solution Approach 1:
The interlock cam on the shaft creates a preliminary blocking action that prevents the shaft from rotating into the armed position unless the interior door handle has first been rotated to unlock the interlock first portion. This anti-action mechanism works alongside the independent handle rotation to prevent inadvertent activation while maintaining ease of legitimate operation.
Solution Approach 2:
The system requires a preliminary action (rotating the interior door handle to move the interlock first portion and unlock the shaft) before the exterior door handle can effectively disengage the auto-disarm cam and arm the system. This preliminary step ensures that independent handle rotation does not accidentally activate the emergency support system.
Data Source
AI summary
An interlock assembly for an aircraft door includes a shaft, an interlock first portion, and an auto-disarm second portion. The shaft is rotatable about the second rotational axis between an armed position and a disarmed position. The shaft includes an interlock cam and an auto-disarming cam. In a first interlock position, the interlock first portion permits rotation of the shaft between the armed position and the disarmed position. In a second interlock position, the interlock first portion prevents rotation of the shaft from the disarmed position to the armed position. In a first auto-disarm position, the auto-disarm second portion permits rotation of the shaft between the armed position and the disarmed position. In a second auto-disarm position, the auto-disarm second portion prevents rotation of the shaft from the disarmed position to the armed position.