Self-Flaring Tube Connection for Leak-Tight High-Pressure Joining

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Solution Overview

Problem

Existing tube connections face issues such as the need for specialized equipment for deformation, inadequate handling of axial and radial forces due to tapering threads, and inefficiencies in brazing processes, which are time-consuming and prone to errors.

Innovation Solution

A tube connection with a thread that increases in maximum diameter and decreases in minimum diameter along the axial direction, allowing for a flared tube end shape without relying on a single thread turn, and optionally using a cylindrical surface for support and a seal for leak-tightness, which can be achieved without specialized tools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a tapering thread is used to simplify the connection process, then the ease of operation is improved, but the strength to withstand axial and radial forces deteriorates

Engineering Contradiction:
Improveease of connectionVSAvoidstrength against axial and radial forces
Core Design Contradiction:
Ease of operationVSStrength

Solution Approach 1:

The patent changes the geometric parameters of the thread by maintaining a constant pitch diameter while allowing the maximum and minimum diameters to vary along the axial direction. This creates a thread profile that balances ease of insertion with mechanical strength, resolving the contradiction between operational simplicity and force resistance.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If specialized equipment is used to deform the tube end for ridge formation, then the reliability of connection is improved, but the device complexity increases

Engineering Contradiction:
Improveconnection reliabilityVSAvoidequipment complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The tube end deformation is achieved through the self-flaring action caused by the constant pitch diameter thread geometry during the insertion process. The tube material deforms itself into the required flared shape without requiring external specialized equipment, thus maintaining reliability while reducing device complexity.

Inventive Principle:
Principle #25Self-service

3Strength

If brazing is used to create strong connections for high pressure applications, then the strength is improved, but the productivity deteriorates due to time consumption and labor intensity

Engineering Contradiction:
Improveconnection strengthVSAvoidconnection speed
Core Design Contradiction:
StrengthVSProductivity

Solution Approach 1:

The patent replaces the thermal brazing process with a mechanical thread-based connection system. The constant pitch diameter thread creates a flared tube end that forms a mechanically strong connection capable of withstanding high pressures, while eliminating the time-consuming and labor-intensive brazing operations, thus improving productivity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 solution provides a reliable, leak-tight connection that withstands axial and radial forces without requiring specialized tools, suitable for both repairs and high-pressure applications, and is adaptable for short-term orders and long tubes.

Implementation Method 1

The minimum diameter of the thread which will deform the material of the tube when rotated inwardly in the through hole. The deformed material will be pushed into the space provided by the increasing maximum diameter of the thread.

Methodology Applied
Scientific EffectPlastic deformation: Plasticity

Data Source

PatentEP3728922B1Tube connection
Publication Date: 2022.03.30 DANFOSS POWER SOLUTIONS II TECH AS
  • EP3728922B1 patent drawingFigure 1
  • EP3728922B1 patent drawingFigure 2

AI summary

The invention relates to a Tube connection for example a hose fitting for connection to a tube, which tube connection comprises a body having a through hole with a central axis, a first end, a second end, an internal thread arranged close to the first end and coaxial with the central axis, wherein the internal thread has a constant pitch diameter, wherein the maximum diameter of the thread increases in axial direction from the first end towards the second end and wherein the minimum diameter of the thread decrease in axial direction from the first end towards the second end.