Threadless Pipe Coupling Locking Mechanism

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Solution Overview

Problem

Existing pipe couplings for oil, water, and gas supply lines are time-consuming to connect and prone to corrosion, with threaded couplings being difficult to protect against corrosion and having reliability issues in harsh environments, and previous solutions either disengage under axial load or are cumbersome to lock.

Innovation Solution

A threadless pipe coupling with convex conical axial end faces and concave conical contact surfaces that generate a radially inward force under axial load to secure the locking member, ensuring a fluid-tight seal and easy assembly/disassembly without tools, using a locking member that engages around the plug to resist both tensile and compressive forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If threaded couplings are used for pipe connections, then the connection strength is improved, but the assembly time increases and corrosion protection becomes difficult

Engineering Contradiction:
Improveconnection strengthVSAvoidassembly time
Core Design Contradiction:
StrengthVSLoss of time

Solution Approach 1:

The connection system is divided into separate functional components: a plug with external conical surface, a socket with internal conical surface and transverse slot, and a separate locking member. This segmentation allows the coupling body to be quickly assembled while the locking mechanism provides subsequent securing, eliminating the need for time-consuming threading operations.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The conical surfaces of the plug and socket are designed to automatically guide and preliminarily secure the plug in the correct axial position during insertion. This preliminary action occurs before the locking member is installed, enabling quick assembly without requiring pre-threading or alignment time.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If threaded couplings are used, then the connection reliability is improved, but corrosion protection becomes difficult and device complexity increases

Engineering Contradiction:
Improveconnection reliabilityVSAvoidcorrosion susceptibility
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The locking function is extracted from the threaded connection structure and implemented by a separate locking member that engages through a transverse slot. This allows the main coupling body to have smooth, continuous surfaces that are easily protected against corrosion, while the locking mechanism provides the necessary mechanical security.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The coupling system combines materials with different properties: the plug and socket can be made from corrosion-resistant materials with smooth surfaces, while the locking member can be made from stronger materials capable of withstanding mechanical loads. This composite approach optimizes both corrosion resistance and connection reliability.

Inventive Principle:
Principle #40Composite materials

3Productivity

If a locking member is inserted through a slot in the socket to engage the plug, then the assembly speed is improved, but the locking member may disengage under axial load

Engineering Contradiction:
Improveassembly speedVSAvoidlocking reliability
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The locking member features convex conical end faces that engage with concave conical surfaces in the plug and socket. These curved conical surfaces provide mechanical advantage under axial load, converting the axial force into radial clamping force that presses the locking member firmly against the conical surfaces, preventing disengagement while maintaining quick assembly capability.

Inventive Principle:
Principle #14Spheroidality (Curvature)

4Object-affected harmful factors

If the locking member ends are located between the plug outer surface and socket side wall, then protection from external interference is improved, but access for locking becomes more difficult

Engineering Contradiction:
Improveexternal interference protectionVSAvoidlocking access
Core Design Contradiction:
Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The transverse slot in the socket serves multiple functions: it provides the insertion path for the locking member, allows access to the locking mechanism during assembly and maintenance, and when closed with a cover, becomes part of the protective structure. This multi-functionality resolves the conflict between protection and accessibility.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 threadless pipe coupling provides a quick, reliable, and corrosion-resistant connection that maintains fluid tightness under various axial loads, simplifying assembly and disassembly while protecting the locking mechanism from external interference.

Implementation Method 1

the axial end faces are convex conical and the axial contact surfaces are concave conical for cooperating with the axial end faces, whereby under axial load the inclined cooperating axial surfaces interact to generate a radially inward directed force on the locking member

Methodology Applied
Scientific EffectConical surface geometry generating radial force: Geometry

Implementation Method 2

a sealing member arranged between a circumferential outer surface of the plug and a cooperating inner surface of a circumferential side wall of the socket, so as to provide a fluid tight seal

Methodology Applied
Scientific EffectSealing:

Data Source

PatentEP2839198B1Threadless pipe coupling with locking member
Publication Date: 2017.08.23 AVK HLDG AS
  • EP2839198B1 patent drawingFigure 1
  • EP2839198B1 patent drawingFigure 2~4
  • EP2839198B1 patent drawingFigure 5~9

AI summary

A threadless pipe coupling (x00) comprises a socket (x01), a plug (x02) configured for being inserted into the socket (x01) in an insertion direction (10), a sealing member (x03) arranged between a circumferential outer surface (x04) of the plug (x02) and a cooperating inner surface (x05) of a circumferential side wall (x06) of the socket (x01), so as to provide a fluid tight seal when the plug (x02) is placed in the socket (x01), wherein the plug (x02) is retained in the socket (x01) by means of a locking member (x07) inserted in a transverse direction through a slot (x08) in the circumferential side wall (x06) of the socket (x01) to engage around the plug (x02) at a location behind the sealing member (x03) as seen in the insertion direction (10). The ends (x28, x29) of the locking member (x07) in the mounted position are located between the outer surface (x04) of the plug (x02) and the circumferential side wall (x06) of the socket (x01) as seen in a radial direction.