Biogas Fermenter Mixer Shaft Welding Stability

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Solution Overview

Problem

Existing mixers for biogas fermenters lack stable attachment of stirring elements to the shaft, leading to radial play and potential weld breakage due to circumferential stresses from fermenting material resistance.

Innovation Solution

A mixer design featuring a rotatable shaft with stirring elements attached by welding along arcuate profiles and equipped with radial projections that act as circumferential end stops to prevent excessive deformation and sliding, thereby stabilizing the attachment and reducing stress on welds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If stirring elements are attached to the shaft by welding along arcuate profiles, then the attachment stability is improved, but the risk of weld breakage due to circumferential stresses increases

Engineering Contradiction:

Improveattachment stabilityVSAvoidweld strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The attachment system is segmented into two independent parts: welding provides radial attachment stability while radial projections handle circumferential stress. This segmentation allows each component to specialize in one function, preventing the welds from bearing circumferential loads that could cause breakage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Radial projections act as intermediary elements between the stirring element and the shaft. These projections absorb and redirect circumferential stresses away from the welds, serving as a mediator that protects the welding joints from damaging forces while maintaining overall attachment stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If radial projections are added to prevent circumferential sliding, then the protection of welds is improved, but the device complexity increases

Engineering Contradiction:

Improveweld protectionVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The radial projections are merged with the shaft structure, forming an integrated component rather than separate attachments. This merging approach minimizes additional complexity while effectively preventing circumferential sliding and protecting the welds from excessive stresses.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Instead of attempting to make the welds themselves resistant to circumferential stresses, the design inverts the approach by using radial projections to prevent circumferential movement in the first place. This indirect protection method is simpler and more effective than trying to strengthen the welds against multi-directional forces.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP4190435B1A mixer for biogas fermenters, and method for the assembly thereof

Publication Date: 2024.06.19 BIOGAS ENG

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AI summary

A mixer (9) for biogas fermenters, adapted to stir a fermenting material, comprises a shaft (10), rotatable about an axis of rotation (x); a stirring element (12), comprising an attachment portion (14) welded to the shaft (10); and a pair of projections (16), protruding radially from the shaft (10) and spaced angularly from respective circumferential ends of the attachment portion (14), so as to form a stop against which these ends abut when the attachment portion (14) becomes deformed and/or slides angularly with respect to the shaft (10) due to the resistance opposed by the fermenting material to the rotation of the mixer (9).