High Thermal Expansion Scraper Ring for Cryogenic Sealing
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Solution Overview
Problem
Traditional seal assemblies fail to maintain effective sealing and scraping performance at cryogenic temperatures, lacking sufficient radial compressive strength and often requiring secondary features like O-rings and spring energizers, which can be unreliable and costly.
Innovation Solution
A self-energized scraper ring with a high coefficient of linear thermal expansion, made from materials like ultra-high molecular weight polyethylene, is designed to contact the inner component, providing a loading force at low temperatures without external biasing components, and features a unique groove and bumper structure for enhanced sealing and scraping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional seal assemblies are used, then sealing function is provided at normal temperatures, but sealing and scraping performance deteriorates at cryogenic temperatures due to loss of radial compressive strength
Solution Approach 1:
The patent changes the material parameter of the scraper ring by selecting materials with high coefficient of thermal expansion (such as certain polymers or composites) that maintain adequate radial compressive strength at cryogenic temperatures. This material parameter change allows the scraper ring to exert sufficient scraping force on the piston rod even when contracted by extreme cold, resolving the contradiction between maintaining sealing reliability and preserving strength at low temperatures.
Solution Approach 2:
The patent employs composite material structures for the scraper ring, combining materials with complementary properties - one providing structural integrity and another providing thermal expansion characteristics. This composite approach enables the scraper ring to maintain both the necessary strength and the thermal response needed to generate scraping force at cryogenic temperatures, overcoming the limitations of traditional single-material seals.
2Reliability
If secondary features like O-rings and spring energizers are added, then sealing effectiveness is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the sealing function and the scraping function into a single integrated scraper ring component. The scraper ring simultaneously provides both sealing against leakage and scraping of contaminants from the piston rod surface, eliminating the need for separate O-rings, spring energizers, and other secondary features. This consolidation reduces device complexity while maintaining or improving sealing effectiveness through the high-compression capability of the scraper ring material.
Solution Approach 2:
The scraper ring is designed as a multi-functional component that performs multiple functions: sealing the annulus, scraping the piston rod surface, and providing mechanical support. This universal component replaces what would traditionally require multiple specialized parts, reducing overall system complexity and manufacturing cost while maintaining reliable sealing performance through its ability to exert high radial compression force.
3Force
If scraper ring material with high thermal expansion coefficient is used, then scraping force is maintained at low temperatures, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-setting the scraper ring dimensions and pre-load characteristics during manufacturing to account for thermal contraction at operating temperatures. The scraper ring is manufactured with specific dimensional tolerances and pre-compression features that ensure adequate scraping force is generated automatically when the material contracts in cryogenic service. This preliminary design approach compensates for thermal effects without requiring excessively tight manufacturing tolerances, balancing scraping force requirements with manufacturability.
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 scraper ring maintains effective sealing and scraping performance at cryogenic temperatures, reducing manufacturing costs and operational complexity while ensuring reliable operation in harsh environments.
Implementation Method 1
a scraper ring for a linear motion assembly comprising: an annular body having a contact face adapted to contact an inner component, wherein the annular body comprises a material having a coefficient of linear thermal expansion of at least 75×10−6/° C.
Data Source
AI summary
A scraper ring for a linear motion assembly including an annular body having a contact face adapted to contact an inner component, wherein the annular body comprises a material having a coefficient of linear thermal expansion of at least 75×10−6/° C. An assembly for linear motion including an outer component defining a bore and a first annular recess extending radially outward from the bore; an inner component disposed in the bore, wherein the inner component is adapted to translate longitudinally within the bore; and a scraper ring disposed in the first annular recess and contacting the inner component, wherein there is no component disposed between any portion of the spacer ring and the outer component.