Pipe Joint Watertight Testing with Compressed Seal Members

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Solution Overview

Problem

Conventional watertight testing devices face challenges in maintaining sealing performance due to thin water-stop bags that can easily be holed, or thicker bags that are less deformable and thus reduce sealing efficiency.

Innovation Solution

The watertight testing device incorporates a design where the seal members are compressed into reduced insertion spaces, with moving devices that press and release the seal members to ensure proper sealing between the core and the pipes, enhancing sealing performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the water-stop bags are made thin to be easily deformed and expanded, then the ease of operation and sealing capability improve, but the reliability deteriorates as they can easily be holed during handling

Engineering Contradiction:
Improvesealing capabilityVSAvoidresistance to holes
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The water-stop bags are designed to dynamically change their state between shrunk (for easy installation) and expanded (for sealing). The bags are initially shrunk to facilitate insertion into the socket, then expanded using compressed air to provide the sealing function, and finally shrunk again for removal. This dynamic transformation allows thin bags to be both easy to handle and reliable during operation.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The physical parameters of the water-stop bags (volume, shape, density) are changed through compression and expansion. By injecting compressed air, the bags expand to provide sealing; by exhausting the air, they shrink for removal. This parameter change allows the same thin bag to provide both ease of operation and reliability at different stages.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If the water-stop bags are made thick to resist holes, then the reliability improves, but the ease of operation deteriorates as they become less deformable and harder to expand

Engineering Contradiction:
Improveresistance to holesVSAvoiddeformability
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The system uses dynamic expansion and shrinkage to overcome the static limitation of thick bags. Even if thick bags are used, they can be shrunk for installation and then expanded for sealing, providing both reliability and ease of operation through this dynamic process.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

Compressed air is used to expand the water-stop bags, providing the force needed to deform even thick bags into the sealing position. The pneumatic system overcomes the resistance of thick material, allowing reliable sealing without sacrificing ease of operation.

Inventive Principle:
Principle #29Pneumatics and hydraulics

3Reliability

If the seal members are compressed into reduced insertion spaces, then the sealing performance improves, but the device complexity increases due to the need for pressing mechanisms

Engineering Contradiction:
Improvesealing performanceVSAvoidpressing mechanism
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The water-stop bags perform self-service by using the injected compressed air to expand themselves into the sealing position without requiring external pressing mechanisms. The air pressure automatically pushes the bags against the socket inner surface, achieving sealing through self-compression.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

Pneumatic pressure is used to compress the seal members into the reduced insertion spaces. The compressed air serves dual purposes: expanding the water-stop bags for sealing and pushing the elastic seal member into its sealing position, simplifying the overall device structure.

Inventive Principle:
Principle #29Pneumatics and hydraulics

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 design improves the sealing performance between the core and the pipes by ensuring the seal members are adequately compressed and maintained in place during the watertight test, thereby reducing leakage and enhancing test reliability.

Implementation Method 1

an elastic seal member (23, 24) that is compressed between a pressing member (25, 26) and a core (22) in a radial direction B

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

a movable rod (55) that is movable in a pipe axial direction A

Methodology Applied
Scientific EffectMechanical Force: Mechanical Force

Data Source

PatentEP3943908B1Watertight testing device
Publication Date: 2025.04.30 KUBOTA CORP
  • EP3943908B1 patent drawingFigure 1
  • EP3943908B1 patent drawingFigure 2
  • EP3943908B1 patent drawingFigure 3

AI summary

This watertight testing device 21 has: a cylindrical core 22 internally fitted to a pipe joint part 1; a first seal member 23 that seals the space between the outer circumference of the core 22 and the inner circumference of one pipe 2; a second seal member 24 that seals a space between the outer circumference of the core 22 and the inner circumference of the other pipe 4; a first pressing member 25 that presses and compresses the first seal member 23 into a first seal member insertion space 46; a second pressing member 26 that presses and compresses the second seal member 24 into a second seal member insertion space 47; a moving device 27 that moves the first and second pressing members 25, 26 in the pipe axial direction A; and a testing fluid supply device 28 that supplies a testing fluid into a testing space 71.