Heat-Resistant Gasket With Expanded Graphite Core

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Solution Overview

Problem

Conventional heat-resistant gaskets fail to maintain sealing performance under high-temperature environments due to stress relaxation and high material costs, especially when exposed to temperatures above 800°C.

Innovation Solution

A heat-resistant gasket design featuring a metal first coating plate with an annular emboss portion, a second metal coating plate in close contact with the emboss portion, and a core of expanded graphite pinched between them, which prevents oxidation and stress relaxation by maintaining compression strength and elasticity, and includes a compression restricting plate to prevent over-compression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a metal gasket made of stainless steel plate is used, then the gasket can maintain structural integrity, but stress relaxation occurs at temperatures above 800°C causing sealing performance degradation

Engineering Contradiction:

Improvestructural integrityVSAvoidsealing performance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The gasket uses a composite structure combining expanded graphite core (providing elasticity and compression strength) with metal coating plates (providing structural integrity and heat resistance). This composite approach allows the gasket to maintain both structural integrity and sealing performance at high temperatures above 800°C without stress relaxation.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the material parameters by selecting expanded graphite with specific compression strength and elasticity properties that remain stable at high temperatures. The metal coating plates are selected with appropriate thermal expansion coefficients and strength characteristics to maintain sealing pressure without relaxation at temperatures above 800°C.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If heat resisting alloy is employed to withstand temperatures above 800°C, then the gasket can maintain sealing performance, but material cost becomes significantly high

Engineering Contradiction:

Improvesealing performanceVSAvoidmaterial cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention replaces expensive heat resisting alloys with a combination of cheaper materials: expanded graphite (which maintains mechanical properties at high temperatures) and ordinary metal coating plates. This substitution significantly reduces material cost while maintaining sealing performance through the functional synergy of the composite structure.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Strength

If expanded graphite is used as the core material, then the gasket can maintain compression strength and elasticity, but the graphite oxidizes at 500-600°C causing disappearance and loss of sealing function

Engineering Contradiction:

Improvecompression strength and elasticityVSAvoidoxidation

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The metal coating plates serve as intermediary protective layers between the expanded graphite core and the high-temperature oxidizing environment. These coating plates prevent direct contact between oxygen and the graphite, blocking oxidation while allowing the graphite to maintain its compression strength and elasticity at temperatures above 800°C.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the potential harm of graphite oxidation into a benefit by using the metal coating plates to create a protective barrier. The coating plates are designed to withstand oxidation themselves while protecting the graphite core, effectively using the oxidizing environment's harm against itself by preventing the graphite from being exposed to it.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Object-affected harmful factors

If the expanded graphite is completely coated with metal plate, then oxidation is prevented, but manufacturing cost increases significantly

Engineering Contradiction:

Improveoxidation preventionVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The metal coating plates are applied locally rather than completely coating the entire graphite surface. The coating is concentrated on the outer surfaces and edges where oxidation would most rapidly occur and propagate, while reducing or eliminating coating on inner surfaces where oxidation is less critical. This local quality approach prevents oxidation while significantly reducing material and manufacturing costs.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention applies partial coating rather than complete coating of the expanded graphite. The metal coating is applied to the extent necessary to prevent oxidation at critical surfaces, but not excessively beyond what is needed. This partial action achieves adequate oxidation protection while minimizing material cost and manufacturing complexity.

Inventive Principle:

Principle #16Partial or excessive 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 design effectively maintains excellent sealing performance at high temperatures while preventing graphite oxidation and reducing material costs by utilizing less expensive materials and minimizing expanded graphite usage.

Implementation Method 1

an expanded graphite sheet 11 is oxidized at 500 to 600° C. so as to form carbon dioxide, thereby starting disappearance in the expanded graphite

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

since the core made of the expanded graphite has excellent compression strength and elasticity even under the high temperature, an elastic restoring force can be achieved by being exposed to compression between the first coating plate and the second coating plate

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS10094473B2Heat-resistant gasket

Publication Date: 2018.10.09 NOK CORP

AI summary

A heat-resistant gasket is provided with a first coating plate in which an annularly continuous emboss portion is formed and which is made of metal, a second coating plate which is arranged so as to face to the first coating plate in a thickness direction and is brought into close contact with a convex surface of the emboss portion, in which end portions in an inner peripheral side of the emboss portion are connected in a state of being in close contact with and lapped over the first coating plate and which is made of metal, and an expanded graphite core which is pinched between the first coating plate and the second coating plate, in a portion between the emboss portion and the overlapped portion of the end portions. Therefore, excellent sealing performance can be maintained even under a high-temperature environment while preventing stress relaxation due to heat.