No-back Arrangement with Load Limiting for Thrust Reverser
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Solution Overview
Problem
Existing no-back devices for thrust reverser systems are oversized and heavy when designed to handle high aerodynamic loads during rejected take-off, risking damage from excessive temperatures and requiring increased motor power, which is undesirable in aerospace applications.
Innovation Solution
A no-back arrangement with a friction disc compressed by a disc spring pack, featuring a limit means to cap the braking load and a load limiter device to manage excessive tensile loads, preventing damage and allowing controlled cowl movement during high-load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the no-back device is designed to withstand high aerodynamic loads during rejected take-off, then the braking load capacity is improved, but the size and weight of the no-back device increase significantly
Solution Approach 1:
The patent changes the parameter of spring compression by introducing a limit means that allows the spring to be compressed only to a predetermined maximum extent. This limits the braking load to a safe level during rejected take-off, preventing the no-back device from needing to be oversized while still protecting against excessive temperatures and damage.
2Force
If the gain of the no-back device is increased to resist higher tensile loads during rejected take-off, then the braking load capacity is improved, but the power, weight and size of the associated motor and control circuits increase
Solution Approach 1:
The patent changes the parameter of spring compression by introducing a limit means that allows the spring to be compressed only to a predetermined maximum extent. This limits the braking load to a safe level during rejected take-off, preventing the no-back device from needing to be oversized while still protecting against excessive temperatures and damage.
3Weight of moving object
If a no-back device sized for normal landing conditions is used, then the weight and size are reduced, but the device is unable to hold the cowl against movement under high tensile loads during rejected take-off, causing temperature rise and potential damage
Solution Approach 1:
The patent applies beforehand cushioning by introducing a limit means that prevents the spring from being compressed beyond a predetermined extent. This cushioning mechanism protects the no-back device from excessive temperatures and damage during rejected take-off by limiting the braking load to a safe level, ensuring reliability without requiring an oversized device.
4Force
If the spring arrangement is allowed to compress freely under high tensile loads, then the braking load capacity is improved, but the operating temperature rises excessively causing damage or failure
Solution Approach 1:
The patent changes the parameter of spring compression by introducing a limit means that allows the spring to be compressed only to a predetermined maximum extent. This limits the braking load to a safe level during rejected take-off, preventing the no-back device from needing to be oversized while still protecting against excessive temperatures and damage.
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 prevents excessive operating temperatures and damage, enabling controlled cowl deployment without the need for oversized no-back devices or motors, maintaining system reliability and reducing weight and size.
Implementation Method 1
The no-back device comprises a friction disc compressed by a disc spring pack
Implementation Method 2
a friction disc compressed against a no-back disc by a spring arrangement
Data Source
Figure 1
Figure 2
AI summary
A no-back arrangement is disclosed for use in applying a braking load to a rotary actuator member (10), the no-back arrangement comprising a no-back device (26) operable to apply a braking load to the rotary actuator member (10) when the rotary actuator member (10) is subject to a tensile loading, and limit means (28) operable to limit the magnitude of the applied braking load.