PFA Sheath Carbon Brush for Fuel-Resistant Flexibility

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Solution Overview

Problem

Carbon brush arrangements in aggressive environments, such as fuel pumps, face challenges with PTFE sheaths due to processing difficulties and stiffness issues, leading to defects in injection-molding and insufficient flexibility for reliable operation.

Innovation Solution

Employing a perfluoroalkoxy polymer (PFA) for the plastic sheath, allowing for thicker, more flexible sheaths and enabling defect-free injection-molding of the connection housing with suitable thermoplastics like POM and PPS, ensuring both flexibility and fuel resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If PTFE is used for the plastic sheath to achieve high fuel resistance, then fuel resistance is improved, but processing difficulty increases and flexibility decreases

Engineering Contradiction:

Improvefuel resistanceVSAvoidprocessing difficulty

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter from PTFE to PFA (perfluoroalkoxy polymer), which has different processing characteristics. PFA maintains the high fuel resistance of PTFE but allows for easier injection molding and produces more flexible sheaths with appropriate wall thicknesses, resolving both the processing difficulty and flexibility issues while preserving fuel resistance

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If PTFE is used for the plastic sheath to achieve high fuel resistance, then fuel resistance is improved, but flexibility worsens

Engineering Contradiction:

Improvefuel resistanceVSAvoidflexibility

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

By changing the material from PTFE to PFA, the patent achieves a material that forms more flexible sheaths. The PFA material allows for better wall thickness control during injection molding, producing sheaths that maintain sufficient flexibility for carbon brush operation while providing the required fuel resistance

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If PTFE is used for the plastic sheath, then fuel resistance is improved, but defects occur in the transition region during injection molding

Engineering Contradiction:

Improvefuel resistanceVSAvoiddefect-free transition region

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent changes the material parameter from PTFE to PFA, which has superior injection molding characteristics. PFA produces defect-free transition regions between the plastic sheath and connection housing, eliminating the manufacturing defects that occur with PTFE while maintaining the required fuel resistance

Inventive Principle:

Principle #35Parameter changes

4Object-affected harmful factors

If wall thickness of PTFE sheath is increased to achieve fuel resistance, then fuel resistance is improved, but stiffness increases reducing flexibility

Engineering Contradiction:

Improvefuel resistanceVSAvoidstiffness

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

By changing the material from PTFE to PFA, the patent achieves a material that provides adequate fuel resistance at lower wall thicknesses. This results in less stiff, more flexible connection conductors that maintain permanent contact between carbon brushes and commutator, resolving the stiffness-fuel resistance trade-off

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10193423B2Carbon brush arrangement

Publication Date: 2019.01.29 SCHUNK HOFFMANN CARBON TECH AG

AI summary

The invention relates to a carbon brush arrangement for connection to an electric motor, comprising at least one carbon brush (17, 18) connected to a connection means (29) provided with a plastic connection housing (32) via a connection conductor (15, 16) provided with a plastic sheath (24, 25), said plastic sheath (24, 25) consisting of perfluoroalkoxy polymer (PFA) in at least a region of transition (33, 34) to the connection housing (32).