Aircraft Actuator Load Detent Assembly for Creep Restriction
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Solution Overview
Problem
Aircraft actuators for flight control surfaces face issues with creep due to external forces like wind and vibration, leading to undesired movement of flight control surfaces, which existing no-back assemblies may not effectively prevent.
Innovation Solution
A load detent assembly is introduced, comprising an engagement member with circumferentially spaced surfaces and a radially biasable stoppage member that interengages to restrict rotation of the actuator's rotating assembly, preventing creep by engaging with the engagement member upon biasing, allowing continuous engagement or selective interlocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional no-back assembly is used to prevent reverse rotation, then back-driving is restricted, but creep (slow movement) under external forces like wind and vibration is not effectively prevented
Solution Approach 1:
The detent member is designed to dynamically engage and disengage from the engagement surfaces based on rotational direction. During normal operation, the detent member can disengage to allow smooth rotation in the driven direction. When reverse rotation or creep occurs, the detent member automatically engages with the engagement surfaces to prevent unwanted movement. This dynamic behavior resolves the contradiction by providing creep prevention only when needed, rather than continuous engagement that would increase complexity.
Solution Approach 2:
The detent member acts as an intermediary element between the driven component and the housing. It mediates the interaction by selectively engaging with circumferentially spaced engagement surfaces on the engagement member, allowing the system to prevent creep without requiring a complex mechanical linkage or additional control systems. This intermediary approach provides effective creep prevention while maintaining relatively simple device architecture.
2Reliability
If the detent member continuously engages with the engagement member, then creep is prevented, but rotation during normal operation is restricted
Solution Approach 1:
The detent member is designed with selective engagement capability that allows it to be disengaged from the engagement surfaces during normal operation to permit smooth rotation. When creep or reverse rotation is detected, the detent member automatically engages with the engagement surfaces to provide stable positioning. This dynamic engagement/disengagement mechanism resolves the contradiction by providing stability only when needed while maintaining ease of operation during normal function.
Solution Approach 2:
The detent member is pre-configured to engage with the engagement surfaces in anticipation of creep or reverse rotation. The circumferentially spaced engagement surfaces are positioned such that as the driven component rotates, the detent member can selectively engage to prevent unwanted motion before it occurs. This preliminary anti-action approach ensures stable positioning without continuously restricting normal rotation.
3Reliability
If multiple circumferentially spaced engagement surfaces are provided, then creep restriction is enhanced, but device complexity increases
Solution Approach 1:
The engagement member features circumferentially spaced engagement surfaces that provide localized engagement points around the circumference. Rather than requiring continuous engagement surfaces or multiple complex mechanisms, the local quality approach uses discrete engagement surfaces at specific locations. This allows the detent member to engage at any of these localized points to prevent creep, enhancing reliability while maintaining relatively simple device structure.
Solution Approach 2:
The engagement surfaces are segmented into discrete circumferentially spaced features rather than forming a continuous structure. This segmentation allows the detent member to engage at specific points around the circumference, providing effective creep prevention while reducing the overall complexity compared to continuous engagement mechanisms. The segmented approach also allows for easier manufacturing and assembly.
Data Source
AI summary
A load detent assembly for restricting creep of a rotating assembly of an actuator used to actuate an aircraft flight control surface. The load detent assembly includes an engagement member having circumferentially spaced engagement surfaces/protruding portions, and a load detent having a stoppage member radially biasable towards the engagement member for interengagement between the engagement surfaces to restrict creep of the rotating assembly. One of the engagement member or the load detent is configured for rotation radially inward of the other of the engagement member or the load detent through at least 360 degrees of rotation. The other of the engagement member or the load detent is configured for being fixed radially outward of the one of the engagement member or the load detent.