Fork Tube Sealing Unit With Eccentric Lips for Misalignment
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Solution Overview
Problem
Conventional sealing units for fork tubes in bicycles and motorcycles face difficulties in maintaining a sealing action against external contaminants due to radial misalignment, leading to dust entry and loss of lubrication oil, which can cause damage and faulty operation of internal components.
Innovation Solution
An asymmetrical sealing unit design with offset sealing lips and variable thickness is employed, allowing the sealing lips to follow misalignment and reduce friction, while a protrusion aids in correct orientation during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the internal diameter of the sealing unit is reduced to increase radial load and ensure sealing action under misalignment, then sealing effectiveness is improved, but passive resistance due to friction increases
Solution Approach 1:
The sealing unit employs an asymmetrical design where the sealing lips are offset from the central axis of the sealing unit. This asymmetry allows the sealing lips to better follow the misaligned stem while maintaining adequate sealing contact without requiring a reduced internal diameter, thus avoiding excessive friction resistance.
Solution Approach 2:
The sealing lips are designed with non-uniform thickness distribution, being thicker in regions where misalignment occurs and thinner in opposite regions. This local variation in geometry allows the sealing lips to adapt to misalignment conditions while maintaining optimal contact pressure and reducing overall friction resistance.
2Ease of manufacture
If an axially symmetric sealing unit is used, then manufacturing and assembly are simplified, but the sealing unit cannot effectively follow the dynamics of the misaligned fork tube stem
Solution Approach 1:
The sealing unit is designed with asymmetrical sealing lips that are offset from the central axis. This asymmetry enables the sealing lips to follow the misaligned stem dynamics while maintaining sealing effectiveness, overcoming the limitation of symmetric designs that cannot adapt to radial misalignment conditions.
3Reliability
If the sealing lips are positioned to follow misalignment, then sealing effectiveness is improved, but the complexity of the sealing unit design increases
Solution Approach 1:
The sealing unit incorporates asymmetrical sealing lips with offset positioning and non-uniform thickness. This design allows the sealing lips to follow misalignment while maintaining a relatively simple overall structure that can be manufactured using conventional processes, balancing complexity with performance.
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 asymmetrical design ensures effective sealing against external contaminants by compensating for radial misalignment and reducing friction, thereby enhancing the sealing action and maintaining performance characteristics.
Implementation Method 1
the misalignment is due to the load acting on the fork tube and transmitted by the vehicle or the rider or in any case by dynamic conditions affecting the suspension
Implementation Method 2
increase in the passive resistance due to the friction
Data Source
AI summary
A sealing unit for a fork tube provided with a lining and a stem disposed slidably inside the lining through an inlet opening. The sealing unit being mounted in the inlet opening to be slidably engaged by the stem and provided with an annular stiffening insert and a flexible annular body provided with two dust-cover lips arranged in sliding contact with the stem, and with a cylindrical static sealing element forcibly and elastically locked inside the inlet opening. The cylindrical static sealing element being radially delimited outwardly by a cylindrical assembly surface having a respective axis (X) of symmetry, which is eccentric with respect to the axis (Y) of symmetry of the first dust-cover lip to ensure a uniform sliding contact of at least the first dust-cover lip on the stem.