Deflectable Seal Assembly for Radial Shaft Misalignment
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Solution Overview
Problem
Radial lip seal assemblies fail to maintain effective sealing when there is substantial radial misalignment between the central axis of a shaft and the centerline of a bore, leading to lubricant leakage and contamination.
Innovation Solution
A seal assembly comprising an outer annular case, an inner annular case, and an annular elastomeric coupler that allows radial displacement between the cases while maintaining constant sealing pressure, ensuring the sealing member remains centered and engaged, even with significant radial offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional radial lip seal assembly is used with rigid case structure, then the structure is simple and manufacturing is easy, but the sealing lip cannot maintain full engagement with the shaft when radial misalignment occurs, causing lubricant leakage and contamination
Solution Approach 1:
The case is divided into two separate annular cases (outer and inner) that can move independently relative to each other. The sealing member is attached to the inner case while the outer case is mounted in the bore, creating segmented structures that can accommodate misalignment through relative movement.
Solution Approach 2:
The rigid case structure is replaced with a dynamic configuration where the inner case can move radially and axially relative to the outer case. This dynamic arrangement allows the sealing member to maintain engagement with the shaft despite radial misalignment between the shaft axis and bore centerline.
2Reliability
If the sealing member is rigidly fixed to the case, then the structure is simple, but the sealing lip cannot adapt to radial misalignment and maintain constant sealing pressure
Solution Approach 1:
A coupler mechanism is introduced as an intermediary between the outer and inner cases. This coupler allows relative movement between the cases while maintaining the connection, enabling the sealing member to adapt to misalignment and maintain constant sealing pressure through the controlled movement it permits.
3Reliability
If the seal assembly uses a fixed rigid structure, then manufacturing precision requirements are lower, but the sealing lip cannot compensate for radial offsets between shaft and bore centerlines
Solution Approach 1:
The fixed rigid structure is replaced with a dynamic system where the inner case can move relative to the outer case. This dynamic capability allows the seal assembly to compensate for radial offsets between the shaft and bore centerlines, reducing the stringency of manufacturing precision requirements for case alignment.
4Reliability
If the seal assembly accommodates radial misalignment through case movement, then sealing integrity is maintained, but the structure becomes more complex with multiple moving parts
Solution Approach 1:
The coupler mechanism merges the functions of connecting the outer and inner cases while simultaneously providing the movement capability needed to accommodate misalignment. This consolidation of connection and movement functions into a single mechanism reduces the overall number of separate components compared to having independent connection and adjustment mechanisms.
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 accommodates substantial radial offsets, maintaining constant sealing pressure and preventing lubricant leakage and contamination, outperforming previous designs by ensuring continuous sealing integrity during rotation and misalignment.
Implementation Method 1
an annular elastomeric coupler has a first axial end attached to the outer case and a second axial end attached to the inner case, the elastomeric coupler being radially deflectable such that one of the outer case and the inner case is radially displaceable relative to the other one of the outer case and the inner case
Data Source
AI summary
A seal assembly is for sealing between an outer member and an inner member, one of which is rotatable about a central axis. An outer annular case is coupled with the outer member and an inner annular case is disposed within and spaced radially inwardly from the outer case. An annular sealing member is disposed within and coupled with the inner case, the sealing member having a centerline coaxial with the central axis and a sealing lip or lips engaged with the inner member. An annular elastomeric coupler has a first axial end attached to the outer case and a second axial end attached to the inner case. The elastomeric coupler is radially deflectable such that the outer case or inner case is radially displaceable relative to the other one of the two cases while the centerline of the sealing member remains coaxial with the central axis.