Plastic Tube Insert Fitting Friction-Lock Mechanism

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Solution Overview

Problem

Existing push-fit fittings for plastic pipes often damage the pipe due to the generation of holding forces through clawing or external wedge elements, and there is a need for an improved retention mechanism that ensures secure connection without pipe damage.

Innovation Solution

A plug-in fitting with a radially prestressed clamping body, a release element, a wedge element, and a spring element that creates a friction-locked connection by displacing the clamping body and wedge element when the pipe is inserted, providing a gentle strain relief and secure fixing without damaging the pipe.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If clawing elements or external wedge elements are used to generate holding forces, then the pipe can be securely connected to the fitting, but the pipe may be damaged

Engineering Contradiction:
Improveconnection securityVSAvoidpipe damage
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A release element is introduced as an intermediary component between the clamping body and the pipe. This release element controls when the clamping body applies force to the pipe, preventing premature or excessive clamping that could damage the pipe while ensuring secure connection when properly activated

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The system uses the insertion motion of the pipe itself to activate the release element, which then automatically triggers the clamping body to engage. The pipe's own movement during installation serves to activate the connection mechanism, eliminating the need for separate activation steps

Inventive Principle:
Principle #25Self-service

2Reliability

If additional measures are taken to generate holding forces by pushing the pipe into or onto the fitting body, then the connection can be secured, but the installation process becomes more complex

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

Solution Approach 1:

The clamping body is pre-configured in a ready-to-clamp state within the fitting body, with the release element positioned to automatically trigger clamping upon pipe insertion. This preliminary arrangement eliminates the need for additional activation steps during installation

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The insertion motion of the pipe automatically activates the release element, which in turn triggers the clamping body to engage. The system uses the installer's own action (pushing the pipe in) to automatically initiate the securing mechanism

Inventive Principle:
Principle #25Self-service

3Force

If the clamping body is radially prestressed against the pipe, then holding forces are automatically generated for strain relief, but the pipe may be damaged by excessive force

Engineering Contradiction:
Improveholding forceVSAvoidpipe damage
Core Design Contradiction:
ForceVSObject-affected harmful factors

Solution Approach 1:

The release element is positioned to prevent the radially prestressed clamping body from contacting the pipe during insertion. This preliminary restraining action prevents excessive force application that could damage the pipe, while allowing the clamping force to engage only when properly activated

Inventive Principle:
Principle #9Preliminary anti-action

Solution Approach 2:

The release element acts as a mediator that controls the interaction between the prestressed clamping body and the pipe. It ensures that the holding force is applied only when the pipe is correctly positioned and activated, preventing premature or excessive force

Inventive Principle:
Principle #24Intermediary (Mediator)

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 ensures a secure and damage-free connection of the pipe, with an audible click indicating proper connection, and enhances strain relief by increasing holding forces without risking pipe damage, while maintaining fluid-tight sealing through strategically placed sealing elements.

Implementation Method 1

a spring element for axial relative Displacement of the clamping body and wedge element when the clamping body is released

Methodology Applied
Scientific EffectSpring force: Spring

Implementation Method 2

friction-locked system of the same on the pipe to be connected

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP2031291B1Insert fitting for a tube comprising plastic material
Publication Date: 2011.03.16 UPONOR INNOVATION AB
  • EP2031291B1 patent drawingFigure 1~2
  • EP2031291B1 patent drawingFigure 3~4

AI summary

The fitting (10) has a spring element (46) for axially relative movement of a clamping body (34) i.e. slotted clamping ring, and a wedge element (38) with the body. A release element (28) comprises an actuator part (32) for a tube to be attached for synchronization of the release element by the tube during suspension or sliding of the release element on and/or in a connection region (20) for releasing the clamping body and for a force-fit attachment of the clamping body to the tube. An inner sleeve element (14) has a sealing element i.e. O-ring, for sealing attachment to the tube.