Spring-Energized Plastic Seal with Backup Ring for Extrusion Prevention
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Solution Overview
Problem
Existing spring energized plastic seals face challenges in maintaining a secure seal under pressure and preventing extrusion between components, particularly due to the lack of effective radial support and thermal growth accommodation.
Innovation Solution
A seal assembly comprising a flexible plastic sealing ring with axial limbs, a spring-loaded sealing element, a rigid metal ring for external compression, and a backup ring with a frusto-conical surface, which applies a radial load to prevent extrusion and accommodate thermal growth, supported by an annular recess in the outer component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring energised plastic seal is used to maintain sealing contact under pressure, then sealing reliability is improved, but the seal is susceptible to extrusion between components due to lack of radial support
Solution Approach 1:
A backup ring is introduced as an intermediary element between the sealing ring and the outer component. This backup ring provides radial support to the sealing ring, preventing extrusion of the sealing ring between the components while maintaining the sealing contact force applied by the spring means.
Solution Approach 2:
The seal assembly combines different materials with complementary properties: a flexible plastics material for the sealing ring to provide elasticity and sealing contact, a spring material for continuous contact force, and a rigid or resiliently flexible material for the backup ring to prevent extrusion. This composite structure resolves the contradiction between maintaining sealing reliability and preventing extrusion.
2Object-affected harmful factors
If the backup ring is made rigid to prevent extrusion, then extrusion resistance is improved, but the seal cannot accommodate thermal growth differentials
Solution Approach 1:
The backup ring is designed with changeable mechanical properties - it can transition between rigid and resiliently flexible states. When cold, it is rigid to prevent extrusion; when heated, it becomes resiliently flexible to accommodate thermal growth differentials. This parameter change resolves the contradiction between extrusion resistance and thermal adaptability.
Solution Approach 2:
The backup ring's mechanical properties are made dynamic rather than static. It adapts its rigidity/flexibility based on operating conditions (temperature, pressure), being rigid when needed for extrusion resistance and flexible when needed for thermal accommodation, thus resolving the contradiction.
3Reliability
If the sealing ring is pressed against the inner component to maintain seal under pressure, then sealing contact is improved, but the sealing ring is subjected to excessive radial load
Solution Approach 1:
The sealing function is segmented into two independent elements: the sealing ring with spring means that applies contact force to the inner component, and the backup ring that provides radial support and prevents extrusion. This segmentation allows the sealing ring to maintain sealing contact without bearing the full radial load, as the backup ring assumes the extrusion prevention function.
Solution Approach 2:
The backup ring acts as an intermediary that bears the radial load and prevents extrusion, thereby protecting the sealing ring from excessive radial forces while allowing the sealing ring to focus on maintaining sealing contact through the spring means.
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
Enhances sealing efficiency by maintaining contact between the sealing element and components under pressure, prevents extrusion of the sealing ring, and accommodates thermal growth differentials, ensuring a reliable and durable seal.
Implementation Method 1
spring means acting on the external periphery of the inner limb to resiliently load the sealing element into sealing engagement with the surface of the inner component
Implementation Method 2
the backup ring abutting a frusto-conical surface of the base of the sealing ring, said frusto-conical surface extending from the internal diameter away from the limbs of the sealing ring and engaging a corresponding frusto-conical surface of the backup ring, to apply a radial load to the inner periphery of the backup ring urging it towards the outer periphery of the inner component
Implementation Method 3
a backup ring made of resiliently flexible plastics material... to accommodate thermal growth differentials
Data Source
Figure 1
AI summary
A seal assembly for providing a seal between a pair of components has a sealing ring made of flexible plastics material and a backup ring (70) made of resiliently flexible plastics material being located coaxially of the sealing ring on the side thereof remote from the limbs, the backup ring abutting a f rusto-conical surface (62) of a base of the sealing ring, said frusto-conical surface engaging a corresponding frusto-conical surface (74) of the backup ring, to apply a radial load to the inner periphery of the backup ring urging it towards the outer periphery of the inner component, when an axial load is applied to the sealing ring by exposure of the sealing ring to pressure from the side of the sealing ring to which the limbs extend, a projection (72) on the backup ring engaging an inner periphery of an axially extending annular recess (80) in the outer component, to locate and support the reinforcing ring radially.