Pipe Joint Seal Geometry for Low-Stress Watertight Compression
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Solution Overview
Problem
Existing seal members made of high hardness materials like NBR face challenges in balancing stress requirements during compression and watertightness, as they either experience high stress leading to deformation or lose sealing surface pressure under water pressure.
Innovation Solution
A seal member design with a first and second projecting portion, where the center of the first circle is within the second circle, reducing deformation and stress while maintaining sealing surface pressure through efficient repulsive force development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seal member is made of high hardness material like NBR to improve oil resistance and chemical resistance, then material durability is improved, but high stress is produced on the seal member during compression
Solution Approach 1:
The seal member is divided into multiple functional portions: a heel portion for insertion guidance, a bulb-shaped portion for sealing, and a compression portion for maintaining contact pressure. This segmentation allows each portion to be optimized for its specific function, reducing overall stress while maintaining durability.
Solution Approach 2:
Different portions of the seal member have different cross-sectional areas and material properties optimized for their specific functions. The bulb-shaped portion has a larger cross-sectional area to distribute stress, while the heel portion has a smaller area for precise insertion. This local quality variation reduces peak stress while maintaining overall reliability.
2Stress or pressure
If the bulb-shaped portion height is reduced to relieve high stress, then stress on the seal member is reduced, but compression allowance decreases which might reduce watertightness
Solution Approach 1:
The seal member design transitions from a single-dimensional height reduction approach to a multi-dimensional solution involving cross-sectional area variation, radial thickness distribution, and axial positioning. The bulb-shaped portion compensates for reduced height with increased radial thickness and optimized cross-sectional geometry, maintaining compression allowance while relieving stress.
Solution Approach 2:
The invention optimizes multiple geometric parameters simultaneously: the bulb-shaped portion's cross-sectional area, the heel portion's thickness, the compression portion's axial position, and the overall radial thickness distribution. These parameter changes work together to reduce stress while maintaining sufficient compression allowance for watertight sealing.
3Reliability
If the seal member is compressed between the sealing surface and spigot outer circumferential surface to generate sealing surface pressure, then watertightness is achieved, but high stress is produced in the interface
Solution Approach 1:
The heel portion is designed to be inserted first, guiding the spigot into proper alignment with the socket before the bulb-shaped portion engages the sealing surface. This preliminary action ensures correct positioning and distributes the compression load more evenly, reducing peak stress in the sealing interface while maintaining watertightness.
Solution Approach 2:
The heel portion acts as an intermediary element between the spigot and the bulb-shaped portion. It absorbs initial insertion forces, guides alignment, and transitions loads smoothly to the bulb-shaped portion, reducing stress concentration in the sealing interface while ensuring reliable sealing contact.
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 seal member effectively reduces stress and maintains watertightness by minimizing deformation and ensuring sufficient sealing surface pressure, even under water pressure, while requiring only a slight increase in insertion force.
Implementation Method 1
a seal member (1) made of an elastic material, having an annular shape, and used for a pipe joint in which a spigot (3) formed at an end of a first pipe is inserted into a socket (2) formed at an end of a second pipe
Implementation Method 2
when the bulb-shaped portion 90 is spread out toward the outer circumference as indicated by arrow D91, bending stress and tensile stress, in particular, increase on the inner circumferential side of the seal member 9
Implementation Method 3
when the bulb-shaped portion 90 is spread out toward the outer circumference as indicated by arrow D91, bending stress and tensile stress, in particular, increase on the inner circumferential side of the seal member 9
Implementation Method 4
when water pressure WP acts on the seal member 9d from inside the pipe in the sealed state, sealing surface pressure of the seal member 9d is lost due to the water pressure WP, creating a gap G
Data Source
AI summary
A seal member includes a heel fitted into a setting groove of a socket and a bulb-shaped portion to be compressed between the socket and a spigot. The bulb-shaped portion includes a first and a second projecting portion respectively formed on the outer side and the inner circumferential side thereof. A first radius of a first circle of the first projecting portion is smaller than a second radius of a second circle including a circular arc-shaped outline of the second projecting portion. The center of the first circle is located within the second circle. The distance between the center of the first circle and the center of the second circle in the axial direction of the seal member is smaller than the difference between the second radius and the first radius.