Brush Holder Spring Design for Wear Reduction

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Solution Overview

Problem

Existing brush holders experience increased wear due to vibrations causing carbon brushes to tilt, leading to high production costs and wear at contact surfaces, as the complex spring arrangement requires special receptacles and generates line tension that cuts into the brushes.

Innovation Solution

A U-shaped leaf spring with a snap-in tab for securing to the carbon holder and a planar contact surface for the carbon brush reduces relative movement and wear by pressing the brush against the holder, eliminating the need for special holding means and simplifying production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a complex spring arrangement with swivelable mounting is used to press the carbon brush against the commutator and guide wall, then the carbon brush is held firmly against the contact surfaces, but the device complexity increases and production costs rise

Engineering Contradiction:

Improveholding firmness of carbon brushVSAvoidspring arrangement complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The spring arrangement is divided into two independent functional portions: a first portion (rolled portion) that presses the carbon brush against the commutator, and a second portion (curved area at free end) that presses the carbon brush against the guide wall. This segmentation allows each portion to be optimized for its specific function while simplifying the overall structure and eliminating the need for complex swivelable mounting mechanisms.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a curved area at the free end of the flat spring presses laterally against the carbon brush, then the carbon brush is held against the guide wall, but line tension increases and cuts into the carbon brush due to vibrations

Engineering Contradiction:

Improveholding of carbon brush against guide wallVSAvoidline tension cutting into carbon brush

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The spring portions are designed with specific local geometries optimized for their functions: the rolled portion has a configuration suitable for pressing against the commutator, while the curved area at the free end is shaped to press against the guide wall. This local optimization reduces concentrated line tension and distributes the pressing force more evenly, minimizing cutting into the carbon brush while maintaining effective holding.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If movement play is preserved to allow carbon brush movement along the guide, then the carbon brush can accommodate vibrations, but increased wear occurs at contact surfaces due to tilting

Engineering Contradiction:

Improvecarbon brush movement capabilityVSAvoidwear at contact surfaces

Core Design Contradiction:

Adaptability or versatilityVSLoss of substance

Solution Approach 1:

The spring arrangement applies preliminary pressing forces in two directions: against the commutator through the rolled portion and against the guide wall through the curved area at the free end. This preliminary anti-action counteracts the tilting motion caused by vibrations before significant wear can occur, while still allowing necessary movement play for the carbon brush to follow the guide.

Inventive Principle:

Principle #9Preliminary anti-action

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 wear on carbon brushes by stabilizing the spring position and minimizing pressure tension, making it economical and retrofittable to existing holders while maintaining pressing force.

Implementation Method 1

the holding spring has two portions preloaded against one another... one of the portions acting on the carbon holder and the other portion acting on the carbon brush

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

securing means is provided on a first leg of the holding spring for securing the spring to the carbon holder... The securing means is preferably formed by a snap-in tab which can snap into a correspondingly shaped receptacle in the carbon holder

Methodology Applied

Scientific EffectMechanical Fastening: Mechanical Fastener

Implementation Method 3

The application means advantageously forms a contact surface which contacts the carbon brush in a planar manner. Accordingly, the pressure tension between the application means and the carbon brush can be kept relatively small while maintaining the same pressing force, which in turn reduces wear in this area.

Methodology Applied

Scientific EffectPressure Distribution:

Data Source

PatentUS7772740B2Brush holder

Publication Date: 2010.08.10 HILTI AG

AI summary

A brush holder (2) has a carbon holder (4) which forms a guide (38) for a carbon brush (6) and at which a holding spring (10) that presses the carbon brush (6) against a first guide side of the guide (38) with a holding pressure force (HF), is provided, with the holding spring (10) having two portions (12, 21) which are biased against one another, and with the carbon holder (4) and the carbon brush (6) projecting through between the two portions (12, 21).