Leather Hydrodynamic Shaft Seal for Low-Temperature Flexibility
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Solution Overview
Problem
Radial shaft seals made from materials like NBR and HNBR become brittle and lose flexibility at low temperatures, making them unsuitable for cold operating conditions.
Innovation Solution
A hydrodynamic sealing element with a plurality of indentations made by debossing, compatible with leather flanges, combining the low glass transition temperature of leather with hydrodynamic pumping features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NBR or HNBR materials are used for seal flanges, then the seal has good flexibility and abrasion resistance at normal temperatures, but the seal becomes brittle and loses flexibility at low temperatures
Solution Approach 1:
The patent changes the material parameter from conventional NBR/HNBR rubber to leather, which has a significantly lower glass transition temperature (−94°F vs. −30°F to −40°F). This parameter change enables the seal to maintain flexibility and sealing performance in cold operating conditions where conventional materials become brittle.
2Temperature
If leather is used for seal flanges, then the seal maintains flexibility at low temperatures, but it cannot be molded to include hydrodynamic features
Solution Approach 1:
The patent extracts the hydrodynamic features from the molding process and implements them through post-manufacturing debossing. This separates the material selection (leather for low-temperature flexibility) from the feature creation (debossing for hydrodynamic pumping), allowing both requirements to be satisfied independently.
Solution Approach 2:
The debossing process creates hydrodynamic indentations in the leather flange after the leather is formed into the seal configuration. This preliminary action of debossing enables the leather seal to acquire hydrodynamic pumping capability without requiring moldability, thus resolving the manufacturing constraint.
3Ease of manufacture
If conventional rubber materials are used, then hydrodynamic pumping features can be molded into the seal, but the seal cracks at low temperatures
Solution Approach 1:
The patent changes the material parameter from conventional rubber (glass transition temperature of −30°F to −40°F) to leather (glass transition temperature of −94°F). This parameter change fundamentally improves cold weather durability while maintaining the ability to create hydrodynamic features through debossing.
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 solution provides a radial shaft seal that maintains flexibility and operational effectiveness in cold conditions, enhancing the sealing performance and operational life by reducing friction and temperature.
Implementation Method 1
Radial shaft seals rely on a pumping mechanism that arises when the lip interacts with the rotating shift. This mechanism causes lubricant to be pumped back to the oil side.
Implementation Method 2
The pumping mechanism is understood to develop through an interaction between the lip and rotating shaft over time, e.g., by the formation of microasperities in the wear track.
Data Source
AI summary
A hydrodynamic sealing element for a radial shaft seal includes a radial flange leg encircling a rotation axis and an oblique flange leg encircling the rotation axis and joined to the radial flange leg. The oblique flange leg extends both radially inward and axially away from the radial flange leg to form an oblique angle relative to the radial flange leg. The oblique flange leg has an air-side surface and an end face that meet at a lip. The oblique flange forms a plurality of hydrodynamic indentations that extend into the oblique flange leg from the air-side surface. The sealing element may be formed from leather, in which case the indentations may be created by debossing the leather. The sealing element may be inserted into a seal case to create a radial shaft seal.