Grounding Brush Assembly With Centering Plate for Stress Relief

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Solution Overview

Problem

Existing grounding brush assemblies for motors and electrical machines suffer from reduced mechanical resistance and stress concentration due to large cuts in the fitting plate, leading to potential misalignment and damage during assembly, which can result in electrical discharges and vibrations through roller bearings.

Innovation Solution

A grounding brush assembly with a fitting plate that includes axial centering portions and reduced retention tongues, minimizing stress concentration and misalignment, and featuring an annular flange or lugs for enhanced radial centering and mechanical stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If large cuts are made in the fitting plate to form retention tongues, then the retention tongues can be formed for axial retention, but the mechanical resistance of the fitting plate is reduced

Engineering Contradiction:

Improveaxial retention capabilityVSAvoidmechanical resistance of fitting plate

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The fitting plate is segmented into multiple retention tongues that are distributed around the circumference, each providing localized retention while maintaining overall structural integrity. The tongues are spaced apart to minimize the size of cuts required in each location.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The retention tongues are designed with varying local properties - the root portion maintains full thickness for strength, while the tip portion is reduced for flexibility and retention function. This local differentiation allows the structure to provide both strength and retention capability.

Inventive Principle:

Principle #3Local quality

2Reliability

If the retention tongues are folded back for axial retention, then the support is retained axially, but stress concentration occurs during folding

Engineering Contradiction:

Improveaxial retention of supportVSAvoidstress concentration in retention tongues

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The retention tongues are designed with a gradual curvature radius at the folding location, which acts as a stress-relieving feature before the fold. This pre-designed geometric feature prevents stress concentration by distributing the bending stresses over a larger area.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The fitting plate is pre-formed with the retention tongues in their final folded position during manufacturing, rather than being folded during assembly. This preliminary action ensures proper stress distribution and eliminates the risk of stress concentration during the folding operation.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the folded length of retention tongues is increased for retention, then axial retention is improved, but stress concentration and mechanical resistance are worsened

Engineering Contradiction:

Improveaxial retention capabilityVSAvoidmechanical resistance to stress concentration

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The retention tongues are designed with just sufficient folded length to provide the required axial retention, rather than excessive length. This partial action approach provides the minimum necessary retention while minimizing stress concentration and maintaining mechanical strength.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The geometric parameters of the retention tongues, including folded length, thickness, and curvature radius, are optimized to achieve the required retention force while maintaining adequate mechanical strength. The parameters are adjusted to find the optimal balance between retention capability and stress resistance.

Inventive Principle:

Principle #35Parameter changes

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 effectively reduces stress concentration and misalignment, enhancing the mechanical stability and precision of the grounding brush assembly, thereby preventing electrical discharges and vibrations in motor and electrical machine bearings.

Implementation Method 1

Due to the conductivity of the fibers, the brush is kept at the same electrical potential as the housing of the electric motor

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

the free ends of the fibers are in radial contact with the outer surface of the rotary shaft

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS20240305174A1Grounding brush assembly

Publication Date: 2024.09.12 AB SKF SKF PATENT DEPARTMENT

AI summary

A grounding brush assembly includes a grounding brush provided with a plurality of conductive fibers and a support inside of which the conductive fibers are fitted. A brush fitting plate is connected with the support of the brush, the fitting plate including a radial portion supported axially against the support of the brush and a plurality of retention tongues for axial retention of the support. The fitting plate also includes a plurality of axial centering portions each extending from the radial portion and spaced circumferentially apart. The centering portions are supported radially against the support of the brush, each retention tongue being located circumferentially between two successive axial centering portions.