Single-Nut Wheel Assembly With Wedge Inserts for Low-Torque Fastening
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Solution Overview
Problem
Existing single-nut wheel fastening systems face issues with progressive loss of fastening preload, requiring high torques and special tools, leading to wear, repeatability issues, and frequent replacement, while conventional pulling devices are not infinitely rigid and suffer from thermal deformation.
Innovation Solution
A wheel assembly with wedge-shaped pulling inserts and a fastening bell that secures the rim and hub with a central screw, featuring a safety system for secure fastening and a deformable fastening bell to absorb thermal expansion, allowing low fastening torques and precise assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high fastening torques (700-800 Nm) are applied to prevent loss of fastening preload, then the fastening reliability is improved, but the wear and friction of the single nut increases excessively and special spanners with extremely long arm are required
Solution Approach 1:
The fastening system is segmented into multiple functional components: a central nut for thread engagement, a separate fastening bell for force transmission, and wedge-shaped pulling inserts for securing the rim. This segmentation allows each component to be optimized independently, enabling reliable fastening at lower torques by distributing the mechanical functions across multiple elements rather than concentrating all stress on the nut alone.
Solution Approach 2:
The fastening bell acts as an intermediary element between the central nut and the wedge-shaped pulling inserts. It translates the rotational fastening torque into axial tension forces that secure the wheel assembly, mediating the force transmission and reducing the direct wear on the nut while maintaining fastening reliability.
2Reliability
If very high fastening torques are used to achieve seizing of contact surfaces, then the fastening security is improved, but more than half of the fastening torque is consumed by seizing (deforming) the conical contact surface irreversibly
Solution Approach 1:
The traditional conical seizing mechanism is replaced with a wedge-shaped pulling insert system that uses geometric locking instead of friction-based seizing. The wedge shape converts axial force into radial clamping force, securing the rim to the hub without requiring irreversible deformation of contact surfaces, thereby reducing torque loss and improving fastening efficiency.
3Strength
If cylindrical pulling pins are used to transmit braking and acceleration torques, then the fastening system can handle dynamic loads, but the pulling system is not infinitely rigid and suffers from thermal deformation and buckling
Solution Approach 1:
The fastening system uses a composite structure combining the central nut (for thread engagement), the fastening bell (for force distribution), and wedge-shaped pulling inserts (for rigid mechanical locking). This composite approach creates a more rigid and thermally stable pulling system that resists buckling and deformation under dynamic loads while maintaining assembly precision.
Solution Approach 2:
The wedge-shaped pulling inserts are designed to counteract thermal expansion and buckling forces through their geometric configuration. The wedge shape provides mechanical leverage that compensates for thermal deformation, maintaining the rigidity and precision of the pulling system under varying temperature conditions and dynamic loads.
4Reliability
If the single nut is made disposable and replaced frequently, then the fastening reliability is maintained, but the manufacturing cost and complexity increase
Solution Approach 1:
The patent applies the disposable principle to the wedge-shaped pulling inserts rather than the central nut. These inserts are designed as low-cost, easily replaceable components that secure the rim to the hub through wedge geometry. If wear occurs, only these simple inserts need replacement, not the entire fastening system, maintaining reliability while minimizing cost and complexity.
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 system provides stable assembly with low fastening torques, easy assembly, and reduced wear, ensuring secure fastening and precise engagement without frequent replacement, while being cost-effective and easy to manufacture.
Implementation Method 1
a plurality of wedge-shaped pulling inserts (8) that are radially expandable within a respective plurality of compartments (6) of the rim (2)
Implementation Method 2
an elastic body (26), which pushes the stop element (24) against the cylindrical body (15) of the screw (13)
Data Source
Figure 1
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AI summary
A wheel assembly for a road vehicle comprising: a rim (2) of a wheel, a rotary hub (3), and a fastening system (1), which secures the rim (2) and the hub (3). The rim (2) has a plurality of compartments (6), each has the shape of a wedge and a first open side in a rear plane of the rim (2) perpendicular to a rotation axis (7) of the wheel and a second open side perpendicular to the first side and facing the rotation axis (7) of the wheel. The fastening system (1) has a plurality of pulling inserts (8), each having the shape of a wedge and being designed to be inserted into a corresponding compartment (6) obtained in the rim (2). The hub (3) has a plurality of housings (9), each shaped so as to accommodate a respective pulling insert (8) allowing the pulling insert (8) to axially slide within the housing (9).