Anti-jamming Piston for Linear Electromechanical Actuator
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Solution Overview
Problem
Existing linear electromechanical actuators for aircraft face issues with screw jamming during electrical or mechanical failures, leading to costly repairs and inability to test functionality before installation, as current solutions either fail to prevent jamming or require complete replacement of the actuator.
Innovation Solution
A linear electromechanical actuator with an anti-jamming piston that shifts between engaged and disengaged positions upon failure, allowing free extension and enabling reengagement without replacing the entire actuator, featuring a key with locking and unlocking sections to bias locking dogs and facilitate sliding within a hollow screw, along with optional secondary screw-nut assemblies and failure detection for early fault identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clutch is used to disengage the screw-nut assembly from the gearbox upon failure, then the actuator can freely extend, but screw jamming is not prevented as disengagement occurs upstream of the screw-nut assembly
Solution Approach 1:
The actuator is divided into functional segments: the anti-jamming piston separates the screw-nut assembly from the hollow screw, allowing independent operation of each component. This segmentation enables the locking dogs to engage/disengage from the abutting surface independently, preventing jamming while maintaining screw-nut functionality.
Solution Approach 2:
The anti-jamming piston acts as an intermediary element between the screw-nut assembly and the hollow screw. It transfers motion during normal operation but can disengage to allow free extension upon failure, mediating between the engaged and free-extension states without causing jamming.
2Reliability
If pyrotechnic explosive loads are used to destroy retaining elements and enable free extension, then the actuator can extend upon failure, but the entire actuator must be replaced after failure, highly increasing reparation costs
Solution Approach 1:
Instead of destroying the entire actuator, only the anti-jamming piston and its retaining elements are discarded upon failure. The main screw-nut assembly, motor, and gearbox are recovered and can be reused after replacing the anti-jamming piston, significantly reducing reparation costs.
Solution Approach 2:
The actuator is designed with replaceable segments: the anti-jamming piston is a separate, replaceable component from the main actuator body. This allows partial replacement (only the piston) rather than complete actuator replacement, reducing costs while maintaining reliability.
3Reliability
If pyrotechnic explosive loads are used to destroy retaining elements, then free extension is enabled, but functional tests cannot be carried out before installation, forcing reliance on entrusted functionality
Solution Approach 1:
The actuator includes a test mode where the anti-jamming piston can be manually engaged and disengaged without failure conditions. This self-testing capability allows functional verification before installation, eliminating the need to trust untested functionality while maintaining the pyrotechnic failure response capability.
Data Source
AI summary
A linear electromechanical actuator with a main screw-nut assembly driven by a main motion device and having a hollow screw with an abutting surface; an anti-jamming piston arranged coaxially within the screw and shiftable between an engaged position in which locking dogs interfere with the abutting surface and a disengaged position in which the piston is free to slide within the screw; and actuating elements configured to shift the piston from the engaged to the disengaged position upon electrical or mechanical failure of the actuator. The actuating elements include a key axially movable between the engaged and disengaged positions and having a locking section, configured to bias the locking dogs into interference with the abutting surface in the engaged position, and an unlocking section, configured to allow free sliding of the piston within the screw in the disengaged position. An anti-jamming device for operating a critical flight control surface.