Tunnel Kiln Support Element Thermal Expansion Match

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Solution Overview

Problem

Tunnel kiln cars experience wear and thermal expansion issues due to differing thermal expansion coefficients of materials, leading to potential damage and inefficiencies in firing processes, particularly in the ceramic and heavy clay industries.

Innovation Solution

A support element with a grid-like frame made of refractory material, matched to the thermal expansion of the firing trays, which reduces wear and allows for efficient thermal insulation and energy conservation by minimizing the mass to be heated, while maintaining high firing quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If support elements are made of refractory material to withstand high temperatures, then thermal stability is improved, but wear on bearing feet increases due to friction during thermal expansion

Engineering Contradiction:
Improvethermal stabilityVSAvoidwear on bearing feet
Core Design Contradiction:
Stability of the object's compositionVSLoss of substance

Solution Approach 1:

The patent introduces an intermediate piece made of material with thermal expansion coefficient matched to the carrier (e.g., ceramic fiber board or similar refractory material). This intermediate piece acts as a mediator between the refractory support element and the metal carrier, absorbing differential thermal expansion through its own expansion/contraction, thereby preventing direct frictional contact and wear on the bearing feet while maintaining thermal stability of the overall structure

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the thermal expansion parameter by selecting materials with matched coefficients. The intermediate piece is specifically chosen to have a thermal expansion coefficient that corresponds to the carrier material, creating a parameter match that eliminates differential expansion stresses and prevents wear during thermal cycles

Inventive Principle:
Principle #35Parameter changes

2Use of energy by moving object

If the mass of the tunnel kiln car is reduced by using lighter support elements, then energy consumption decreases, but structural strength and thermal resistance may be compromised

Engineering Contradiction:
Improveenergy consumptionVSAvoidstructural strength
Core Design Contradiction:
Use of energy by moving objectVSStrength

Solution Approach 1:

The patent employs composite construction by combining refractory materials (for thermal resistance) with insulating materials (for thermal isolation). The support elements use refractory material strategically only where structural strength and heat resistance are critical, while incorporating lighter insulating materials in non-critical areas, achieving optimal strength-to-weight ratio and minimizing energy consumption without compromising structural integrity

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The support structure is segmented into functional zones: refractory material is applied only where high-temperature resistance and structural strength are required (e.g., load-bearing areas and heat-exposed surfaces), while lighter materials are used in areas requiring minimal strength or thermal isolation, reducing overall mass and energy consumption while maintaining necessary structural properties

Inventive Principle:
Principle #1Segmentation

3Productivity

If more trays are stacked on the tunnel kiln car to increase capacity, then productivity increases, but thermal expansion differences cause greater wear and potential damage

Engineering Contradiction:
Improvekiln capacityVSAvoiddamage risk to bearing feet
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The intermediate piece with matched thermal expansion coefficient serves as a protective intermediary that absorbs differential expansion stresses. This allows the system to support higher loads from multiple stacked trays without transmitting excessive frictional forces to the bearing feet, enabling increased productivity while maintaining reliability

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The intermediate piece provides beforehand cushioning by being pre-installed between the carrier and support elements. It anticipates and cushions against the thermal expansion differences that will occur during firing, preventing direct contact and potential damage to the bearing feet before wear can occur, thus enabling safe stacking of multiple trays

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

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 significantly reduces wear on the support elements, ensures uniform thermal expansion, enhances firing quality, and increases kiln capacity by allowing more trays to be stacked, while reducing energy consumption through lighter, more efficient design.

Implementation Method 1

The support element (17) consists of a material whose coefficient of thermal expansion essentially corresponds to the coefficient of thermal expansion of the lowest firing tray (35a). During the kiln cycle, the tunnel kiln car and the kiln furniture are exposed to large temperature fluctuations, which leads to thermal expansion.

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

Since the components of the tunnel kiln car receiving the kiln furniture and the kiln furniture consist of materials with different thermal expansion coefficients, there is a risk that the sensitive bearing feet will be damaged by different thermal expansions.

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 3

which reduces wear and allows for efficient thermal insulation and energy conservation by minimizing the mass to be heated

Methodology Applied
Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentEP3355015B1Support elements for a tunnel furnace cart or carriage, tunnel furnace cart or carriage with such support elements and tunnel furnace with such a tunnel furnace cart or carriage
Publication Date: 2019.09.11 REFRATECHNIK HLDG GMBH
  • EP3355015B1 patent drawingFigure 1
  • EP3355015B1 patent drawingFigure 2
  • EP3355015B1 patent drawingFigure 3

AI summary

The present invention relates to a support element (17) for forming an upper wagon or sled cover (43) of a tunnel kiln wagon or sled (3) for the direct support of a lowest fuel carrier of a fuel carrier stack formed from stacked fuel carriers, wherein the support element (17) has a grid-like support frame (22) with one or more grid recess(s) extending from a support frame top to a support frame bottom and at least one cover plate (23) covering and closing the grid recess(s), preferably from above, as well as a tunnel kiln wagon or sled (3) with at least one such support element (17) and a tunnel kiln with at least one such tunnel kiln wagon or sled (3).