Dynamic Seal Assembly With Pressure-Triggered Bypass Venting
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Solution Overview
Problem
Existing seal assemblies in hydraulic systems, such as those in transmission pistons, experience leakage issues even at low pressures, and fail to reliably manage fluid and air venting above a certain pressure limit.
Innovation Solution
A seal assembly design featuring two radial piston walls with a groove and sealing lips, where the second sealing lip pivots inward at a predetermined limit pressure, creating a bypass passage for hydraulic fluid and air to flow into a bypass line, ensuring a defined leakage flow, with the geometry and material of the sealing lip and bypass line determining the limit pressure and leakage rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal assembly with a single sealing lip is used, then the structure is simple, but leakage occurs even at low pressures and the seal cannot reliably manage fluid venting above pressure limits
Solution Approach 1:
The seal assembly is segmented into multiple functional sealing lips: a first sealing lip for primary sealing, a second sealing lip for limiting overpressure, and a third sealing lip for additional sealing. This segmentation allows each lip to perform a specific function, improving overall sealing reliability while managing different pressure conditions effectively.
Solution Approach 2:
The second sealing lip is designed as a valve lip that can dynamically change its sealing state based on pressure conditions. Below a predetermined limit pressure, it maintains sealing contact; above this pressure, it opens to allow controlled leakage. This dynamic behavior enables the seal to adapt to varying pressure conditions automatically.
2Reliability
If a seal assembly seals completely at all pressures, then sealing is reliable, but controlled leakage above a pressure limit cannot be achieved
Solution Approach 1:
The valve lip (second sealing lip) is designed to dynamically transition between sealed and open states based on pressure differential. Below the predetermined limit pressure pG, it seals the entry space completely. Above pG, it pivots inward to open the entry space, allowing controlled leakage through the bypass line, thus adapting to different pressure conditions.
Solution Approach 2:
The seal assembly changes its sealing parameters based on pressure conditions. The valve lip's position and sealing contact change as a function of the pressure differential across the seal, allowing the system to maintain reliable sealing at low pressures while enabling controlled leakage at high pressures through parameter variation.
3Stress or pressure
If the second sealing lip is made thinner and longer, then the limit pressure decreases, but the structural strength of the seal is reduced
Solution Approach 1:
Different regions of the seal assembly have different local qualities optimized for their specific functions. The valve lip has specific geometric characteristics (thickness, length, curvature) optimized for pressure sensitivity and pivoting motion, while other parts of the seal maintain sufficient strength. This localized optimization allows the valve lip to be thin and long for low limit pressure without compromising overall seal strength.
Solution Approach 2:
The seal assembly uses elastomeric materials with specific viscoelastic properties that provide both the necessary flexibility for the valve lip to pivot at low pressures and the structural strength to maintain sealing contact. The material composition is optimized to balance softness (for low limit pressure) with durability (for structural strength).
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 assembly effectively seals up to a predetermined pressure, then allows controlled leakage of hydraulic fluid and air, reducing axial space requirements and simplifying assembly, while maintaining precise leakage control.
Implementation Method 1
The second sealing lip pivots radially inwards at a pressure above the predetermined limit pressure pG
Implementation Method 2
the geometry and material of the sealing lip and bypass line determining the limit pressure and leakage rate
Data Source
AI summary
A seal assembly includes a piston and a seal. The piston includes a first radial piston wall, a second radial piston wall extending radially further than the first radial piston wall, a groove formed between the first radial piston wall and the second radial piston wall, and a bypass line extending at least partially around the groove. The seal disposed in the groove. The seal includes a first sealing lip extending radially outward beyond the second radial piston wall and a second sealing lip. The second sealing lip is sealed against the first radial piston wall to seal an entry space when acted on by a pressure below a predetermined pressure limit pG, and pivotable radially inward to open the entry space when acted on by a pressure above the predetermined pressure limit pG.