One-Piece Double Containment Fittings for Leak-Stable Tube Connections

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Solution Overview

Problem

Conventional double containment fittings for connecting double containment tubing systems are prone to leaks at intersections and become loose, compromising the integrity of double containment piping systems.

Innovation Solution

The development of double containment fittings as one-piece integral structures with inner and outer cylinders and ribs, forming separate flow paths to prevent leaks and maintain stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional double containment fittings are made from assemblies of several separate pieces, then the fittings can be manufactured and assembled, but fluid leaks occur at intersections and connections become loose

Engineering Contradiction:
Improvemanufacturability of fittingsVSAvoidleak prevention and connection stability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent merges multiple separate fitting pieces into a single integral molded structure. The fitting comprises a body portion with integrated inner and outer tube receiving structures, eliminating intersections between separate components where leaks could occur. This single-piece construction maintains manufacturability through injection molding while eliminating leak paths that existed in multi-piece assemblies.

Inventive Principle:
Principle #5Merging (Combining)

2Adaptability or versatility

If double containment fittings use separate pieces assembled together, then the fittings can be constructed with different components, but the connections become loose and compromise system integrity

Engineering Contradiction:
Improvecomponent configuration flexibilityVSAvoidfitting connection stability
Core Design Contradiction:
Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The fitting integrates multiple connection functions into a single stable structure. The body portion simultaneously receives and secures both inner and outer tubes through integrated interference fit structures, preventing loosening that occurs with separate assembled pieces. The monolithic construction ensures consistent geometric relationships and eliminates gaps between components.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If double containment fittings are made as one-piece integral structure, then leaks are prevented and stability is improved, but the device complexity increases

Engineering Contradiction:
Improveleak prevention and system integrityVSAvoidstructural integration complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

While the fitting is a single integral piece, the design incorporates functional segmentation through distinct receiving structures for inner and outer tubes. The body portion contains integrated features such as interference fit zones, drainage pathways, and alignment structures that are molded as one piece but provide differentiated functions. This segmentation of function within a unified structure achieves reliability without excessive complexity.

Inventive Principle:
Principle #1Segmentation

4Ease of operation

If conventional fittings use multiple separate pieces, then assembly and disassembly is easier, but fluid can leak at intersections of the separate pieces

Engineering Contradiction:
Improveassembly convenienceVSAvoidfluid leakage at connections
Core Design Contradiction:
Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The single-piece fitting eliminates all internal intersections and joints where leaks could occur. Fluid flows continuously through the integrated drainage pathways without encountering gaps or seams between separate components. The integral construction ensures that the drainage function is maintained while completely eliminating leak paths at component interfaces.

Inventive Principle:
Principle #5Merging (Combining)

Data Source

PatentEP4726245A2Double containment fittings for connecting double containment tubing
Publication Date: 2026.04.15 K D W CO LTD
  • EP4726245A2 patent drawingFigure 1
  • EP4726245A2 patent drawingFigure 2
  • EP4726245A2 patent drawingFigure 3~4

AI summary

A double containment fitting for engagement with double containment pipes and comprising a one-piece integral structure having at least one outer cylinder having at least two outer receiving openings, at least one inner cylinder having at least two inner receiving openings, and a plurality of ribs integral with and spacing the at least one outer cylinder from the at least one inner cylinder, thereby forming an inner fitting flow area within the inner cylinder and forming an outer fitting flow area between the at least one outer cylinder and the at least one inner cylinder and between adjacent ribs. Each inner tube of the double containment pipes are connected to the double containment fitting by being located within one of the inner receiving openings. Each outer tube of the double containment pipes are connected to the double containment fitting by being located within one of the outer receiving openings.