Locking Nut Tightening With Axial Load Verification

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Solution Overview

Problem

Existing screwing systems face challenges in maintaining consistent tightness, especially in environments with vibration or wear, making it difficult to verify and maintain the correct tightening torque, particularly in inaccessible areas like aircraft systems.

Innovation Solution

A method involving a screwing system with a threaded rod and locking nut, utilizing a measuring system to determine axial tightening loads, which includes an initial tightening phase to a nominal torque, adjusting the brake position, and verifying the final axial clamping load within a compliance range, facilitated by a controller and tension sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If regular maintenance actions are performed to check and re-tighten the screwing system, then the tightening reliability is improved, but the maintenance time and operational disruption increase

Engineering Contradiction:
Improvetightening reliabilityVSAvoidmaintenance time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by installing a measuring system (strain gauges, transducers) during the initial assembly phase. This allows continuous monitoring of tightening parameters without requiring subsequent disassembly or re-tightening for verification. The brake position is adjusted preliminarily to ensure proper engagement, eliminating the need for repeated maintenance interventions.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback through measuring systems that continuously monitor axial clamping loads and tightening parameters. This real-time feedback enables verification of tightening reliability without physical intervention, allowing operators to detect loosening trends and schedule maintenance only when necessary, rather than performing routine re-tightening regardless of actual condition.

Inventive Principle:
Principle #23Feedback

2Reliability

If the brake position is adjusted to ensure proper locking, then the locking reliability is improved, but the tightening process complexity increases

Engineering Contradiction:
Improvelocking reliabilityVSAvoidtightening process complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical adjustment procedures with automated measurement and control systems. Strain gauges and transducers automatically detect the brake position and tightening parameters, substituting manual mechanical adjustment with electronic sensing and digital verification, thereby reducing process complexity while maintaining or improving reliability.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The measuring system performs self-verification of the brake position and tightening parameters. The system automatically determines whether the brake is correctly positioned and whether tightening specifications are met, eliminating the need for complex manual inspection procedures and reducing the skill level required for operation.

Inventive Principle:
Principle #25Self-service

3Reliability

If a pin-type lock or folding tab lock washer is used to prevent loosening, then the anti-loosening capability is improved, but the device complexity and assembly time increase

Engineering Contradiction:
Improveanti-loosening capabilityVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the locking function with the brake mechanism itself. The brake's position and engagement provide the primary locking action, eliminating the need for separate pin-type locks or folding tab lock washers. This integration reduces the number of components and simplifies the overall device while maintaining anti-loosening capability through the brake's inherent mechanical interference.

Inventive Principle:
Principle #5Merging (Combining)

4Manufacturing precision

If the screwing system is tightened to a predetermined nominal torque, then the tightening consistency is improved, but the ability to verify actual clamping load decreases

Engineering Contradiction:
Improvetightening consistencyVSAvoidclamping load verification
Core Design Contradiction:
Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent introduces strain gauges and transducers as intermediary measurement devices between the tightening action and the verification process. These sensors directly measure the actual clamping load generated by the tightening process, providing precise verification data that correlates directly with the applied torque, thereby enabling both consistent tightening and accurate verification simultaneously.

Inventive Principle:
Principle #24Intermediary (Mediator)

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

Ensures easy and quick verification of screw system tightness, guaranteeing compliance with technical specifications and reducing maintenance time, with the option for periodic checks and alerts for maintenance or flight authorization.

Implementation Method 1

a measuring system determining an axial tightening load in the screwing system

Methodology Applied
Scientific EffectAxial tightening load measurement:

Data Source

PatentEP4357626B1Method for tightening and controlling a screwing system
Publication Date: 2025.01.15 EUROCOPTER FRANCE SA
  • EP4357626B1 patent drawingFigure 1~2
  • EP4357626B1 patent drawingFigure 3~5

AI summary

The present invention relates to a method for tightening a screw system (10) comprising a threaded rod (17) and at least one locking nut. The method includes an initial tightening phase (60) comprising successively: tightening the screw system (10) to a predetermined nominal torque with a torque wrench, measuring an initial axial tightening load in the screw system (10) with the measuring system (30), adjusting the position of the locking nut relative to the threaded rod (17) for the placement of a locking nut (25), measuring (65) a final axial tightening load with the measuring system (30), and verifying (66) that the final axial tightening load is within a conformity range.