Offset Bicycle Chainring Structure for Buckling Resistance
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Solution Overview
Problem
Chain drives in bicycles face challenges with chain skewing and sprocket stability due to increased chain tensile forces, especially with multiple sprocket arrangements, leading to potential buckling and instability, while requiring a balance between stability and lightweight construction.
Innovation Solution
A single sprocket design with an offset tooth center plane and a connecting area formed by a plurality of arms, which increases rigidity and load-bearing capacity, featuring a thin-walled open cross-section and alternating tooth geometry for improved chain guidance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sprocket diameter is increased to provide a larger gear ratio range, then the available gear ratios are improved, but the chain tension forces increase and the sprocket becomes more susceptible to buckling
Solution Approach 1:
The patent applies asymmetry by offsetting the tooth center plane axially inward relative to the hub center plane. This asymmetric positioning allows the teeth to be positioned optimally for chain engagement while the hub area maintains structural stability, enabling large sprocket diameters without proportional increases in buckling risk.
Solution Approach 2:
The patent resolves the contradiction by utilizing the axial dimension rather than solely radial scaling. By offsetting the tooth center plane axially inward, the design accommodates large gear ratios while maintaining structural integrity through three-dimensional spatial arrangement rather than simple radial enlargement.
2Area of stationary object
If the sprocket is positioned axially inward to accommodate multi-sprocket arrangements, then the space utilization is improved, but the chain angle increases and chain tension forces increase
Solution Approach 1:
The asymmetric offset of the tooth center plane inward allows the sprocket to be positioned axially inward for compact multi-sprocket arrangements while the tooth geometry compensates for the increased chain angle, maintaining effective chain engagement despite the unfavorable positioning.
3Weight of moving object
If the chainring is made lighter to meet weight requirements, then the weight is reduced, but the rigidity decreases and buckling risk increases
Solution Approach 1:
The asymmetric design concentrates material where it is most needed for structural integrity. By offsetting the tooth center plane and optimizing the connecting area geometry, the design achieves maximum rigidity with minimum material, allowing lightweight construction without sacrificing buckling resistance.
Solution Approach 2:
The patent applies local quality by varying the material distribution and cross-sectional properties in different areas of the chainring. The connecting area between hub and teeth is optimized locally to provide sufficient rigidity against chain tension, while other areas can be minimized for weight reduction.
Data Source
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AI summary
The single chainring (10) according to the invention is suitable for mounting on a bicycle crank arm (2) rotatably mounted about an axis of rotation and for engaging a bicycle chain with inner and outer link plates. The chainring (10) has an axial outer and an axial inner surface. Furthermore, the chainring (10) has a hub area (20) with an inner profile at its radially inner end for transmitting torque from the crank arm (2) to the chainring (10). The hub area (20) defines an axial hub median plane between an outer and an inner hub plane. The chainring (10) also has a toothed area (30) with a plurality of teeth (32) at its radially outer end for engaging the bicycle chain.