Knitted Hose Bellows Attachment via Central Compression

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Solution Overview

Problem

Existing flexible line elements for motor vehicle exhaust systems face challenges in effectively damping speed-dependent engine vibrations and maintaining a secure fit on metal bellows, particularly due to issues with radial force introduction, thermal loading, and limited extensibility of knitted hoses, leading to potential corrosion and loss of grip during thermal expansion.

Innovation Solution

A knitted hose made of metal wire is applied to a metal bellows with its rows of stitches rotated 90° axially, forming a two-layer, flat knitted fabric that is then reformed into a cylindrical tube with a central compressed area, providing axial stability and a form-fitting attachment that maintains the knitted hose's position even under stretching, while eliminating protruding ends and cutting waste.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the knitted hose is routed to the connection points of the metal bellows and fixed by conventional end sleeves, then the knitted hose can be secured to the bellows, but radial force is introduced into the bellows corrugation which may cause destruction and increased thermal loading leading to corrosion

Engineering Contradiction:

Improvesecure attachment of knitted hoseVSAvoidradial force introduction and thermal loading

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of fixing the knitted hose at the bellows edges (conventional approach), the invention inverts the attachment location to the central corrugated area of the bellows. This is achieved by providing a compressed area in the knitted hose that is radially compressed to form a bead, which is then attached to the central corrugations away from the edges, thereby avoiding radial force introduction at the connection points.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The knitted hose is pre-compressed radially to form a bead structure before attachment to the bellows. This preliminary compression creates a form-fitting connection that secures the hose without requiring additional fastening components, and the bead is designed to engage with the bellows corrugations in a way that prevents radial force introduction during operation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the knitted hose is compressed as a whole to form a wire cushion with radially inner wavy impression, then the hose can be fixed to the metal bellows, but the radial expansion is disruptive in installation situations and large material amount is not desirable

Engineering Contradiction:

Improveattachment of knitted hose to metal bellowsVSAvoidinstallation difficulty and material usage

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Instead of compressing the entire knitted hose to form a wire cushion, the invention applies compression locally to create a discrete bead structure. This compressed area is radially compressed to form a bead that engages with the bellows corrugations, while the rest of the hose remains uncompressed and maintains its normal flexibility and dimensions, facilitating easier installation and reducing material usage.

Inventive Principle:

Principle #3Local quality

3Reliability

If radially thickened peripheral areas are provided at both ends of the knitted tube for fastening, then the hose can be fixed to the metal bellows, but the hose can only stretch to a very limited extent and loses grip when bellows is stretched more than the knitted tube capability

Engineering Contradiction:

Improvefastening of knitted tube to metal bellowsVSAvoidextensibility of knitted hose

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Instead of providing thickened peripheral areas at both ends of the knitted tube (conventional approach), the invention inverts the attachment strategy by placing a single compressed bead area in the central region of the bellows. This central attachment point allows the knitted hose to stretch freely at the ends without losing grip, as the bead remains engaged with the central corrugations while accommodating bellows expansion.

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration ensures the knitted hose remains securely attached to the metal bellows during thermal expansion, maintains damping effectiveness, and simplifies assembly by reducing axial mobility and eliminating cutting waste, thereby preventing potential corrosion and mechanical disruptions.

Implementation Method 1

the knitted hose is usually drawn onto the metal bellows to dampen vibrations, so that it covers at least a section of the same

Methodology Applied

Scientific EffectVibration damping: Damping

Implementation Method 2

an area compressed by pressing which is seated in a form-fitting manner on the metal bellows in this area

Methodology Applied

Scientific EffectRadial compression: Compression

Data Source

PatentEP2463493B1Flexible conduit element and method for applying a knit tube to a metal bellows

Publication Date: 2015.06.17 WITZENMANN GMBH

Figure 1
Figure 2~4

AI summary

The flexible conduit element has helically or annularly corrugated metal bellows (1) and hose (4) knitted with metal wire (5) for damping vibrations of metal bellows. The hose is seated by pressing compacted peripheral zone (7) from the ends (3) of the metal bellows non-positively and/or positively, to space apart from the center of metal bellows. An independent claim is included for method for applying metal wire knitted hose to metal bellows of flexible conduit element.