Conductive Elastomer Seal for Length Measuring Device

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Solution Overview

Problem

Existing length measuring devices are complex to manufacture and assemble due to the difficulty in producing and integrating a resilient sheet metal tongue for environmental protection and electrical connection, leading to potential measurement errors from electrical charge accumulation.

Innovation Solution

A length measuring device with a housing featuring an elongated hollow profile and a conductive elastomer seal that forms an integral connecting element, ensuring electrical contact and sealing between the housing and scale, while using a discharge element to dissipate electrical charges and maintain reliable contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a resilient sheet metal tongue is used to establish electrical contact and provide environmental protection, then electrical connection is achieved, but manufacturing complexity and assembly difficulty increase significantly

Engineering Contradiction:
Improveelectrical connectionVSAvoidmanufacturing and assembly complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the sealing function and electrical connecting function into a single integrated seal element. The seal includes a sealing portion for environmental protection and a connecting portion with electrical contact elements that establish electrical connection with the scale, eliminating the need for separate sheet metal tongue components

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The seal element performs multiple functions simultaneously: it provides environmental protection through sealing, establishes electrical contact between the scale and housing, and compensates for manufacturing tolerances through its resilient material properties, replacing what previously required multiple specialized components

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

2Measurement precision

If electrical charges accumulate on the scale surface, then measurement errors occur, but adding discharge elements increases device complexity

Engineering Contradiction:
Improvemeasurement accuracyVSAvoiddevice structure
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the discharge function from the main seal structure by incorporating discrete discharge elements that are electrically connected to the scale surface. These elements provide a dedicated path for charge dissipation without requiring a complete redesign of the sealing system

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The discharge elements act as intermediaries between the charged scale surface and the housing, providing a controlled electrical path that safely dissipates accumulated charges without interfering with the measurement function or requiring complex additional systems

Inventive Principle:
Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If a seal is used to provide environmental protection, then the scale is protected, but electrical contact between the scale and housing is lost

Engineering Contradiction:
Improveenvironmental protectionVSAvoidelectrical contact
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The seal integrates both sealing and electrical connecting functions into a single component. The connecting portion of the seal includes electrical contact elements that maintain electrical connection between the scale and housing while the sealing portion provides environmental protection

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The seal is made from electrically conductive elastomer material that combines the properties of elastomers (flexibility, sealing capability) with electrical conductivity, enabling it to perform both mechanical sealing and electrical conduction functions simultaneously

Inventive Principle:
Principle #40Composite materials

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 simplifies the construction and assembly of the device, reduces measurement errors by ensuring consistent electrical contact and reference potential, and adapts to tolerances and vibrations without abrasion.

Implementation Method 1

an electrically conductive connecting element which is part of a seal inserted in a sealing manner between the hollow profile and the cover... It is particularly advantageous if the connecting element consists of an electrically conductive elastomer... Through the invention, the resilient property of the material of the seal is used in an advantageous manner in addition to the resilient contacting of the diverting element of the scale

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

a discharge element which discharges electrical charges that accumulate on the surface... An electrically conductive connecting element establishes electrical contact between this diverting element of the scale and at least one of the housing parts

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP2306157B1Length measuring device
Publication Date: 2017.09.06 DR JOHANNES HEIDENHAIN GMBH
  • EP2306157B1 patent drawingFigure 1
  • EP2306157B1 patent drawingFigure 2
  • EP2306157B1 patent drawingFigure 3

AI summary

The length measuring device has a housing with an elongated hollow section (21) and a front side cover (22) that is arranged at the hollow section. An electrically conducting connecting element (41) is provided as a component of a seal ring (4), which is arranged between the hollow section and the cover.