Muffle Assembly Using Welded Brackets to Reduce Oven Assembly Time

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Solution Overview

Problem

Existing methods for assembling a muffle inside a domestic cooking oven's external bearing structure are inefficient, as they concentrate stress around screw holes, are lengthy and expensive, and can compromise surface finishing processes.

Innovation Solution

A process involving a muffle with transversal flanges and fixing brackets welded to the flanges, which are then engaged with the external bearing structure using discrete welding spots to distribute stress and facilitate easy assembly without invasive fastening to the muffle's lateral wall.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If screws are used to fasten the muffle to the frame, then the muffle can be securely attached, but stress concentrates around the screw holes compromising structural solidity

Engineering Contradiction:
Improvestructural solidityVSAvoidlocalised tension concentration
Core Design Contradiction:
StrengthVSStress or pressure

Solution Approach 1:

The invention divides the fastening function into separate components: the muffle structure, the bearing structure with recesses, and connecting elements that bridge them. This segmentation allows stress to be distributed across multiple connection points and areas rather than concentrated at discrete screw holes, resolving the contradiction between secure attachment and structural solidity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The connecting elements act as intermediaries between the muffle and the bearing structure. These elements include recesses in the bearing structure and corresponding protrusions on the muffle, creating a distributed connection system that reduces localised stress concentration while maintaining secure attachment.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If multiple screws are used to fasten the muffle, then secure attachment is achieved, but the assembly process becomes lengthy and expensive

Engineering Contradiction:
Improvefastening stabilityVSAvoidassembly time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The invention merges the fastening function into the structural design itself through integrating recesses and protrusions that form connection points. This eliminates the need for separate screw fastening operations, reducing assembly time and cost while maintaining reliable attachment through the distributed connecting elements.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The muffle and bearing structure are designed with self-aligning connecting elements (recesses and protrusions) that automatically position and secure the muffle during assembly. This self-service mechanism eliminates the need for complex fastening operations, reducing both assembly time and labor costs while ensuring reliable attachment.

Inventive Principle:
Principle #25Self-service

3Reliability

If screws are fastened to the muffle, then secure attachment is achieved, but subsequent surface finishing processes are compromised

Engineering Contradiction:
Improveattachment stabilityVSAvoidsurface finish quality
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The invention extracts the fastening function from the muffle's lateral wall surface by placing connecting elements on the bearing structure instead. This allows the muffle's external surfaces to remain intact and free from screw holes, preserving surface finish quality for subsequent painting or lacquering operations while maintaining secure attachment through the bearing structure's recesses.

Inventive Principle:
Principle #2Taking out (Extraction)

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

This method reduces assembly time and cost, provides a stable and non-invasive fastening solution that preserves surface finish quality, and allows for a lightweight yet strong muffle construction.

Implementation Method 1

said at least one fixing bracket (20) being welded to said at least one flange (10)

Methodology Applied
Scientific EffectWelding: Welding

Data Source

PatentEP3129714B1Process of assembling a muffle to the structure of an oven and oven including a muffle assembled according to the process
Publication Date: 2020.02.26 WHIRLPOOL EMEA SPA
  • EP3129714B1 patent drawingFigure 1~2
  • EP3129714B1 patent drawingFigure 3
  • EP3129714B1 patent drawingFigure 4~5

AI summary

The present invention relates to a domestic cooking oven (1 ) comprising an external bearing structure (2), a muffle (3) defining a cooking chamber and housed inside the external bearing structure (2) and a door (4) for accessing the cooking chamber. The muffle (3) comprises one or more flanges (10) and the oven (1) comprises one or more fixing brackets (20) configured to constrain the muffle (3) to the external bearing structure (2). The fixing brackets (20) are welded to the respective flanges (10) of the muffle (3), in particular through spot welding, and are engaged with the external bearing structure (2).