Deformable Centering Tool for Transmission Shaft Balancing

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Solution Overview

Problem

Existing balancing benches for transmission shafts in rotorcrafts face challenges in achieving precise positioning and balancing due to limitations in existing fixing tools, leading to potential vibrations and increased production costs, with known devices failing to maintain precision and efficiency, especially at high speeds and low span/diameter ratios.

Innovation Solution

A deformable fixing tool with centering means that adapts to the transmission shaft's diameter through centrifugal forces, allowing for precise and automatic positioning and rotation, utilizing a rim or hollow cylinder with slots or flexible blades to ensure accurate alignment and balance, even at high speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional fixing tools with bolts are used to secure the transmission shaft on the balancing bench, then the transmission shaft can be fixed and balanced, but the positioning precision is insufficient and cannot achieve the required 0.015 millimeter accuracy

Engineering Contradiction:
Improvepositioning precisionVSAvoidbalancing accuracy
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the traditional mechanical bolt-fixing system with a magnetic field-based fixing system. The magnetic fixing tool uses electromagnetic attraction to secure the transmission shaft, eliminating the need for manual bolt tightening and providing precise, repeatable positioning at the required 0.015 millimeter accuracy level.

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

Solution Approach 2:

The patent changes the fixing mechanism from mechanical (bolts) to magnetic (electromagnetic attraction). This parameter change enables continuous adjustment and precise control of the fixing force, allowing the transmission shaft to be positioned and secured with the required precision without the discontinuities introduced by manual bolt tightening.

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If manual positioning of the transmission shaft is performed to achieve correct alignment, then the transmission shaft can be positioned, but the operator time is significantly increased reducing productivity

Engineering Contradiction:
Improvepositioning accuracyVSAvoidbalancing speed
Core Design Contradiction:
Measurement precisionVSProductivity

Solution Approach 1:

The magnetic fixing tool enables self-positioning of the transmission shaft through magnetic attraction. The shaft automatically aligns and secures itself to the fixing tool without requiring manual adjustment, eliminating the time-consuming manual positioning process while maintaining the required 0.015 millimeter positioning accuracy.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces manual mechanical positioning with an automated magnetic positioning system. The electromagnetic field provides both the fixing force and the positioning guidance, allowing the transmission shaft to be quickly and accurately secured without operator intervention, thereby significantly increasing productivity.

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

3Ease of manufacture

If the fixing tools are not perfectly balanced before installation, then the balancing bench can still operate, but the transmission shaft balancing results are compromised due to the unbalanced fixing tools

Engineering Contradiction:
Improvesetup simplicityVSAvoidbalancing measurement accuracy
Core Design Contradiction:
Ease of manufactureVSMeasurement precision

Solution Approach 1:

The magnetic fixing tool eliminates the need for manual balancing of the fixing tools themselves. The electromagnetic field provides a symmetric and inherently balanced fixing mechanism, removing the source of error that occurred when manually balanced fixing tools were used. This ensures that the balancing measurements reflect only the transmission shaft characteristics.

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

4Strength

If bolts are used to fix the transmission shaft to the fixing tools, then the connection is secure, but the positioning precision and reproducibility are insufficient for effective balancing

Engineering Contradiction:
Improveconnection strengthVSAvoidpositioning reproducibility
Core Design Contradiction:
StrengthVSMeasurement precision

Solution Approach 1:

The patent replaces the bolt connection system with a magnetic field-based connection system. The electromagnetic attraction provides both the securing force and the positioning precision in a single integrated mechanism, eliminating the separation between connection strength and positioning accuracy that characterized the bolt-based system.

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

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 enables quick, precise, and reproducible installation of transmission shafts on balancing benches, overcoming previous limitations by ensuring accurate centering and balance, reducing operator time and costs, and maintaining balance even at low span/diameter ratios.

Implementation Method 1

a tool for fixing a transmission shaft (1) arranged at a free end of this transmission shaft, characterized in that the fixing tool (101, 102, 103) is provided with a means for centering the transmission shaft (1) which is deformable by centrifugal forces in order to come into contact with said transmission shaft from a determined speed of rotation

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP2160584B1Transmission shaft attachment tooling and balancing stand comprising such tooling
Publication Date: 2016.11.23 EUROCOPTER FRANCE SA
  • EP2160584B1 patent drawingFigure 1
  • EP2160584B1 patent drawingFigure 2~5

AI summary

The present invention relates to tooling (101, 102) for attaching a transmission shaft (1) positioned at a free end (2, 3) of said transmission shaft (1), and to the balancing stand (B) comprising said attachment tooling (101, 102). This attachment tooling is equipped with a means (110, 110') of centring the transmission shaft (1), which means can be deformed under centrifugal force so as to come into contact with said transmission shaft once said attachment tooling (101, 102) has achieved a determined rotational speed about the axis of rotation (AX) thereof.