No-Back Actuator Friction Disk for Controlled Thrust Reverser Deployment
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Solution Overview
Problem
Conventional electrical thrust reverser actuators for turbojets face challenges in controlling the deployment speed and preventing accidental deployment of movable surfaces, leading to increased weight and size, which compromises safety and efficiency.
Innovation Solution
An actuator with a friction disk that uses friction to brake rotation when a traction force is exerted, featuring a smooth surface and an obstacle for cooperation with a pawl, allowing controlled movement between over-retracted and retracted positions, and synchronized with the nut's position to avoid blocking and reduce stress on the nacelle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an anti-extension device is added to brake screw rotation during deployment, then deployment speed control is improved, but device complexity and weight increase
Solution Approach 1:
The friction disk is integrated into the existing anti-extension device structure, combining the braking function with the screw mechanism. The friction disk rotates with the screw and uses friction between its smooth surface and the pawl to provide braking during deployment while allowing free rotation during retraction, thus controlling deployment speed without adding separate complex braking systems.
Solution Approach 2:
The friction disk acts as an intermediary element between the screw and the pawl. It transfers the braking force through friction contact while allowing the screw to rotate freely in the opposite direction. This intermediary mechanism enables speed control during deployment while maintaining simplicity and avoiding direct complex braking components on the screw itself.
2Reliability
If a main locking device with locks is used to prevent accidental deployment, then safety is improved, but device complexity and weight increase
Solution Approach 1:
The friction disk with its smooth surface and obstacle automatically engages with the pawl based on the direction of screw rotation. During deployment, the friction between the smooth surface and pawl provides self-braking without external control. During retraction, the obstacle-passing mechanism allows automatic disengagement and free rotation. This self-service特性 reduces the need for additional locking components and control systems.
3Ease of operation
If the ball screw is made reversible for free movement, then ease of operation is improved, but control over deployment speed deteriorates
Solution Approach 1:
The friction disk dynamically changes its interaction with the pawl based on the direction of screw rotation. During deployment, the smooth surface creates friction that dynamically brakes the rotation. During retraction, the dynamic motion allows the pawl to pass over the obstacle freely. This dynamic behavior enables the screw to be reversible while maintaining speed control during deployment.
Solution Approach 2:
The friction disk undergoes periodic changes in its operational state corresponding to the rotation direction. In one half-cycle (deployment), friction braking is active. In the other half-cycle (retraction), free rotation is permitted. This periodic action pattern allows the system to alternate between controlled braking and free movement, achieving both speed control and reversibility.
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 reduces the weight and size of the actuator, enhances reliability, and ensures controlled deployment and retraction of the movable surface, improving safety and efficiency by minimizing unnecessary forces and stresses on the nacelle.
Implementation Method 1
an anti-extension device comprising a friction disk free to rotate relative to the screw and designed to use friction to brake a portion constrained to rotate with the screw
Data Source
AI summary
An actuator includes a screw mounted on a body to pivot, a nut connected to an element for moving, and that is engaged on the screw to be moved between an over-retracted first position and a deployed second position on either side of a retracted third position that is spaced apart from the over-retracted position by a distance corresponding to the screw rotating through a first angular sector and an anti-extension device comprising a friction disk having at least one smooth surface and an obstacle both for co-operating with at least one pawl, thereby defining both at least one second angular sector of free rotation for the friction disk and also a position for blocking the friction disk.