Armrest Shaft Locking Mechanism for Back-Drive Prevention
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Solution Overview
Problem
Existing adjustable aircraft armrests lack a fast and stable mechanism for infinite adjustability, often resulting in back-drive issues that lead to fatigue due to the armrest shifting from the desired orientation.
Innovation Solution
A locking mechanism featuring a locking shaft with guide grooves and a nut with corresponding grooves, which prevents back-drive by constraining lateral motion and linear translation of the locking shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a threaded rod mechanism is used for infinite adjustability, then the armrest can be adjusted to any position, but the adjustment process becomes cumbersome and time-consuming
Solution Approach 1:
The locking mechanism is divided into distinct functional segments: a shaft for positioning, a nut for locking, and a button for actuation. This segmentation allows the system to achieve infinite adjustability through the shaft's continuous movement while providing rapid locking through the nut-button mechanism, eliminating the need to turn a threaded rod for both positioning and locking.
Solution Approach 2:
The nut is pre-positioned to engage with the shaft at any point along its travel path. When the button is pressed, the nut is already in place to immediately lock the shaft at the desired position, eliminating the need for additional turning or adjustment actions after positioning.
2Device complexity
If a simple retaining mechanism is used, then the structure remains simple, but the armrest becomes unstable and experiences significant back-drive
Solution Approach 1:
The locking mechanism merges multiple functions into a compact assembly: the nut provides both the locking function and resistance to back-drive forces, while the button integrates the actuation and release functions. This combination achieves high reliability without adding significant structural complexity, as all components work together in a unified mechanism.
Solution Approach 2:
The nut acts as an intermediary element between the shaft and the housing. It translates the shaft's linear movement into a locked position and provides mechanical resistance to back-drive forces, thereby stabilizing the armrest position without requiring complex additional structures.
3Reliability
If a locking mechanism is added to prevent back-drive, then position stability improves, but the device complexity increases
Solution Approach 1:
The locking mechanism is designed to be self-servicing through the button-nut-shaft interaction. Pressing the button automatically engages the nut to lock the shaft, and releasing the button allows automatic release. This self-service design prevents back-drive without requiring external locking devices or complex control systems, thereby minimizing added complexity.
Data Source
AI summary
A locking mechanism to prevent back-drive includes a locking shaft with guide grooves. Locking shaft guides engage the guide grooves to constrain lateral motion of the locking shaft. A nut includes corresponding grooves to the locking shaft, and engages the locking shaft to prevent linear translation. The locking mechanism may be incorporated into a aircraft seat armrest to create a positive lock in the armrest position.