Sealed Screw Joint Assembly With Compression-Limiting Bushings
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Solution Overview
Problem
Existing assemblies in rail and road transport vehicles face issues with joint creep and seal deterioration due to excessive compression, necessitating frequent tightening of fixing screws to maintain a watertight seal.
Innovation Solution
An assembly design featuring annular seals with integrated metal rings and controlled compression, utilizing parallel flat surfaces and threaded nuts to secure the connection, ensuring homogeneous sealing and limiting seal creep.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gasket is compressed to ensure a watertight seal, then sealing reliability is improved, but the gasket creeps and requires regular tightening of fixing screws
Solution Approach 1:
A rigid ring is introduced as an intermediary element between the gasket and the compression force from the fixing screws. The ring distributes the compression force uniformly across the gasket while preventing localized deformation and creep, thereby maintaining sealing reliability without the need for frequent tightening
Solution Approach 2:
The invention changes the physical state and distribution of compression force by introducing the rigid ring structure. This modifies how the compression parameter is applied to the gasket, transforming it from concentrated point loads to distributed uniform pressure, which prevents creep while maintaining the sealing function
2Reliability
If fixing screws are tightened regularly to maintain the seal, then sealing reliability is improved, but the gasket's creep is exacerbated
Solution Approach 1:
The rigid ring is installed in advance to counteract the harmful effect of gasket creep before it occurs. By providing a rigid structure that resists deformation, the ring prevents the gasket from creeping under compression, eliminating the need for repeated tightening operations that would otherwise worsen the creep
3Reliability
If excessive compression is applied to the gasket, then initial sealing is improved, but the gasket deteriorates faster
Solution Approach 1:
The rigid ring transforms the compression parameter distribution, converting excessive localized compression into moderate uniform distribution. This allows the gasket to achieve effective sealing without subjected to damaging stress concentrations, thereby extending its service life while maintaining initial sealing quality
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 effectively limits seal creep and deterioration, maintaining a reliable seal while extending the service life of the seal and preventing screw loosening.
Implementation Method 1
a gasket is inserted between the chassis or bogie and the flange of the underbody. The gasket is pierced by fixing screws that are tightened into threaded holes in the chassis or bogie, thus compressing the gasket to ensure a watertight seal.
Implementation Method 2
The joint also comprises at least one metal ring received in one of the holes of the seal. The height H of each ring along the screw axis is less than the resting thickness E of the seal. A ratio between the resting thickness E of the seal and the height H of each ring is preferably between 1.2 and 1.5.
Data Source
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AI summary
The present invention relates to an assembly comprising a support (10), a component attached to the support, and at least two screws (34) for securing the component to the support. Each screw (34) is inserted through a hole (65) in the component and screwed into a threaded hole (60) in the support along a screw axis (XX). The assembly includes a gasket (33) between the support and the component, the gasket having at least two holes (90) through which the screws pass. The assembly includes at least two rigid bushings (95), each received by a respective hole in the gasket. Each bushing defines a passage through which one of the screws passes. Each bushing has a height along the screw axis less than or equal to the rest thickness of the gasket. The screws are tightened so that the support and the component bear against each bushing.