Pressure Balanced Radial Shaft Seal Design

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Solution Overview

Problem

Conventional radial rotary shaft lip seals are not pressure balanced, leading to premature failure and fluid leakage due to increased heat generation and wear at high pressures and surface speeds, especially under dynamic conditions with high vibration and misalignment.

Innovation Solution

A pressure balanced radial seal design featuring a first sealing member in constant engagement with the shaft and a second sealing member biased by fluid pressure to maintain contact, with a retaining member to prevent rotation and axial movement, and a secondary seal to evacuate leaking fluid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional radial rotary shaft lip seals are used, then the seal structure is simple, but the seal fails prematurely and leaks fluid at high pressures and surface speeds due to heat generation and wear

Engineering Contradiction:

Improveseal service lifeVSAvoidseal structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The seal is divided into two distinct sealing members: a first sealing member that contacts the shaft and a second sealing member that contacts the first sealing member. This segmentation allows each member to perform a specific function, with the second member compensating for wear of the first member, thereby extending overall seal life without significantly increasing complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces pressure balance by directing fluid pressure onto the second sealing member to bias it against the first sealing member. This parameter change (applying counter-pressure) compensates for wear and maintains sealing contact, improving reliability at high pressures and speeds without requiring complex mechanical elements.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the seal operates at high differential pressures and high rotational speeds, then the sealing performance should be maintained, but heat generation and wear increase causing premature failure

Engineering Contradiction:

Improveseal performance at high pressure and speedVSAvoidheat generation at seal contact

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The invention replaces mechanical biasing elements (such as springs or O-rings) with fluid pressure biasing. Fluid pressure from the sealed environment directly biases the second sealing member against the first, eliminating the need for separate mechanical biasing components and reducing heat generation from mechanical friction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If the first sealing member is biased harder against the shaft, then sealing contact is maintained, but wear increases leading to premature failure

Engineering Contradiction:

Improvesealing contact maintenanceVSAvoidseal contact duration

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The invention uses fluid pressure as a variable parameter to dynamically bias the second sealing member. This allows the sealing force to be maintained without excessive wear, as the fluid pressure automatically compensates for wear rather than requiring a constantly high mechanical biasing force that would accelerate wear.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The fluid pressure from the sealed environment itself serves to bias the second sealing member, creating a self-regulating system. The sealed fluid provides the biasing force needed to maintain sealing contact, eliminating the need for external mechanical biasing components and reducing wear on the primary sealing interface.

Inventive Principle:

Principle #25Self-service

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 design significantly reduces fluid leakage and extends the service life of the seal by maintaining consistent contact and reducing wear, even at high differential pressures and rotational speeds, without the need for mechanical elements or O-ring biasing.

Implementation Method 1

A fluid pressure directed at least onto the second sealing member, whereby the second sealing portion is configured to bias the first sealing portion into the constant engagement with the peripheral surface of the member

Methodology Applied

Scientific EffectFluid pressure: Pressure Increase

Data Source

PatentUS8720902B2Pressure balanced radial rotary shaft seal

Publication Date: 2014.05.13 KOFLER HARALD

AI summary

In combination with a body defining an annular space and a member received for rotation or linear movement within the annular space, an annular seal includes a first sealing member defining a first sealing portion disposed in constant engagement with a peripheral surface of the member during the rotation or the linear movement thereof, a second sealing member defining a second sealing portion disposed in constant engagement with the first sealing member and radially aligned only with the first sealing portion, and a fluid pressure directed at least onto the second sealing member, whereby the second sealing portion is configured to bias the first sealing portion into the constant engagement with the peripheral surface of the member.