Overload Coupling Structure for Reverse Torque Buckling Protection

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Solution Overview

Problem

Conventional overload couplings for rotating drive systems are complex, heavy, fatigue-sensitive, and costly, particularly in aircraft applications, and fail to provide a reliable and fail-safe solution for preventing damage from overloading in reverse rotation directions.

Innovation Solution

An overload coupling design featuring concentric inner and outer connecting elements with angled arms that buckle and fail predictably under excessive torque, allowing for controlled decoupling and preventing sudden load peaks, utilizing a staggered arrangement of plates for tension and compression loads, and enabling free rotation after failure to avoid stress peaks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional overload couplings are used to prevent catastrophic failures, then reliability is improved, but device complexity and weight increase

Engineering Contradiction:

Improveprotection against catastrophic failureVSAvoidcomplexity of overload coupling

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The overload coupling is divided into separate functional elements: an inner connecting element, an outer connecting element, and multiple arms with distinct functions. Some arms are designed for torque transmission while others serve as overload protection elements that can fail independently, segmenting the failure modes and protecting the overall system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The overload protection function is extracted as a separate mechanism from the main torque transmission path. The arms with reduced cross-sectional areas are specifically designed to fail first under overload conditions, removing the dangerous excess load before it can damage the main drive train components.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If conventional overload couplings are used to prevent catastrophic failures, then reliability is improved, but weight increases

Engineering Contradiction:

Improveprotection against catastrophic failureVSAvoidweight of overload coupling

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

Different parts of the arms have different cross-sectional areas optimized for their specific functions. The arms have reduced cross-sectional areas at critical locations where they need to fail first, while maintaining full strength in other regions. This local differentiation allows weight reduction without compromising the primary torque transmission capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The overload coupling utilizes composite construction with arms made from materials or structures that provide high strength-to-weight ratio. The combination of different arm types (some with reduced cross-sections) creates a composite structure that achieves overload protection with minimal weight penalty.

Inventive Principle:

Principle #40Composite materials

3Reliability

If conventional overload couplings are used to prevent catastrophic failures, then reliability is improved, but fatigue sensitivity increases

Engineering Contradiction:

Improveprotection against catastrophic failureVSAvoidfatigue resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The arms with reduced cross-sectional areas act as pre-designed weak points that fail first under overload conditions. This beforehand cushioning protects the main torque transmission path from sudden shock loads and impact forces, preventing fatigue damage to the more critical components.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The potential weakness of having reduced cross-sectional areas is converted into a benefit: these same features serve as controlled failure points that protect the overall system. The arms designed to fail first absorb the harmful overload energy, converting what would be a weakness into a protective mechanism that prevents fatigue damage to the main drive train.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Strength

If high rigidity is achieved in nominal rotation direction, then power transmission efficiency is improved, but vulnerability to overload in reverse direction increases

Engineering Contradiction:

Improverigidity in nominal rotation directionVSAvoidprotection against reverse torque overload

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The arms are designed with asymmetric properties: they have different cross-sectional areas and structural characteristics that provide high rigidity and strength for torque transmission in the nominal rotation direction, while simultaneously being vulnerable to buckling and failure in the reverse rotation direction. This asymmetric design achieves both goals of efficient power transmission and overload protection.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

Instead of designing for symmetric strength in both directions, the solution inverts the approach by designing the arms to be strong in the nominal direction but deliberately weak in the reverse direction. The arms are configured to buckle and fail under reverse torque loads, providing automatic overload protection when rotation occurs in the opposite direction.

Inventive Principle:

Principle #13The other way round (Inversion)

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 design achieves high rigidity in the nominal rotation direction, is lightweight, simple, and fatigue-insensitive, providing reliable protection against overloading while allowing for smooth failure modes that prevent damage to connected components.

Implementation Method 1

each one of the at least first and second arms comprises an arrangement of at least one plate, wherein the at least one plate is loaded in tension when a first torque acts on the inner connecting element in the first direction of rotation

Methodology Applied

Scientific EffectTension: Tension

Implementation Method 2

the at least one plate is loaded with a compression force when a second torque acts on the inner connecting element in the second direction of rotation

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 3

the first and second arms are formed with predefined geometries to enable buckling of the first and second arms when the second torque exceeds a predetermined threshold

Methodology Applied

Scientific EffectBuckling: Deformation

Data Source

PatentEP4050231B1An overload coupling for rotating drive systems

Publication Date: 2023.08.16 AIRBUS URBAN MOBILITY GMBH

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Figure 2A~2B
Figure 3~4

AI summary

The present embodiments relate to an overload coupling 200 for coupling a driving device 280 to a driven device 290. The present embodiments also relate to a rotating drive system 270 with such an overload coupling 200, to a rotor system 110 with such a rotating drive system 270, and to a rotary-wing aircraft 100 with such a rotor system 110. The overload coupling 200 may include concentrically arranged inner connecting element 210 coupled to the driving device 280 and outer connecting element 220 coupled to the driven device 290. At least a first and a second arm 230, 240 that each include an arrangement 250 of at least one plate 255 may connect the inner connecting element 210 with the outer connecting element 220.