Current Control Brush Assembly for Motor Shaft Charge Dissipation

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Solution Overview

Problem

Static electrical charges accumulate on motor drive shafts due to friction and induced voltages, leading to potential discharges that increase wear and interfere with motor operation.

Innovation Solution

A current control brush assembly with axial and radial electrically conductive filaments that transfer charges from the shaft to an electrically conductive housing, providing a larger contact area and reducing the likelihood of discharges by dissipating the charge to Earth ground.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional single-direction brush assemblies are used, then the structure is simple, but the contact area with the shaft is limited and charge dissipation is insufficient

Engineering Contradiction:
Improvecharge dissipation effectivenessVSAvoidbrush assembly structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent transitions from a single-direction (axial) brush assembly to a multi-dimensional configuration by adding radial filaments that extend in a direction perpendicular to the axial filaments. This dimensional expansion increases the contact area with the shaft surface, allowing more effective charge dissipation while maintaining a relatively compact structure.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The brush assembly is segmented into distinct functional components: axial filaments for primary charge collection, radial filaments for enhanced surface contact, and a housing structure that organizes these elements. This segmentation allows each component to perform its specific function optimally while contributing to the overall reliability of the charge dissipation system.

Inventive Principle:
Principle #1Segmentation

2Reliability

If multiple filaments are added to increase contact area, then charge dissipation improves, but manufacturing complexity increases

Engineering Contradiction:
Improveelectrical connection robustnessVSAvoidassembly construction
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent combines axial and radial filaments within a single integrated housing structure, creating a unified brush assembly that performs multiple functions simultaneously. This merging approach consolidates what would otherwise be separate components, simplifying the manufacturing process and assembly procedures while achieving robust electrical connection through the combined filament system.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The brush assembly is designed as a multi-functional unit where the same housing and filament structure simultaneously provides mechanical support, electrical conduction, and multi-directional charge collection. This universal design eliminates the need for separate components for each function, thereby reducing manufacturing complexity while improving reliability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 the accumulation of static electrical charges on the shaft, minimizing wear and operational interference by establishing a robust electrical connection and dissipating induced charges, thereby enhancing motor reliability and longevity.

Implementation Method 1

a first set of electrically conductive filaments (42) extending generally inward along an axial direction (4) and a radial shaft grounding ring (SGR) (40) coupled to the axial button (38). The radial SGR (40) includes an electrically conductive annular housing (50), and a second set of electrically conductive filaments (44) retained by the electrically conductive annular housing (50). The second set of electrically conductive filaments (44) is arranged circumferentially around the electrically conductive annular housing (50), and extends generally inward along a radial direction (6).

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

During operation of an electric motor, a static electrical charge may accumulate on the motor drive shaft due to friction between the rotating shaft and the surrounding air.

Methodology Applied
Scientific EffectTriboelectric effect: Triboelectric Effect

Data Source

PatentEP2727225B1Current control brush assembly
Publication Date: 2016.12.14 ILLINOIS TOOL WORKS INC
  • EP2727225B1 patent drawingFigure 1~3
  • EP2727225B1 patent drawingFigure 2
  • EP2727225B1 patent drawingFigure 4

AI summary

A system, in certain embodiments, includes a current control brush assembly including an axial button having a first electrically conductive housing retaining a first set of electrically conductive filaments. The first set of electrically conductive filaments extends generally inward along an axial direction. The current control brush assembly also includes a radial shaft grounding ring (SGR) coupled to the axial button. The radial SGR includes a second electrically conductive housing retaining a second set of electrically conductive filaments. The second set of electrically conductive filaments is arranged circumferentially around the second electrically conductive housing, and the second set of electrically conductive filaments extends generally inward along a radial direction.