Alternating-Tooth Bicycle Chainring for Rough-Terrain Chain Retention
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Solution Overview
Problem
Managing chain engagement and tension in bicycles, especially over rough terrain, is challenging due to potential frame and chainring damage from high load applications, and existing solutions do not adequately address severe chain tension and energetic motion.
Innovation Solution
A solitary bicycle chainring with alternating groups of teeth, where the first group has protrusions on the outboard side and the second group is recessed, designed to work with an interleaved drive chain, providing enhanced guidance and tension management through specific tooth shapes and chamfers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the chainring uses conventional uniform teeth design, then the structure is simple and easy to manufacture, but the chain engagement is unreliable under severe chain tension and energetic motion from rough terrain
Solution Approach 1:
The chainring teeth are segmented into two distinct groups: a first group with protrusions on the outboard side and a second group without protrusions. This segmentation allows each group to perform different functions - the first group provides enhanced chain guidance and engagement, while the second group maintains simpler geometry. The alternating arrangement of these two groups throughout the tooth set creates a pattern that improves overall chain retention reliability without requiring complete redesign of all teeth.
Solution Approach 2:
Protrusions are applied locally only to specific teeth in the first group rather than uniformly to all teeth. This local quality approach places the additional geometric feature (protrusion) only where it is most needed for chain engagement during high-stress conditions, while leaving other teeth with simpler geometry. This resolves the contradiction by providing enhanced reliability at critical locations without unnecessarily increasing complexity across the entire chainring.
2Reliability
If the chainring teeth are designed with protrusions to improve chain guidance, then chain engagement is enhanced, but the risk of frame and chainring damage from high load applications increases
Solution Approach 1:
The tooth set is segmented into two groups with different geometries, where only the first group has protrusions. This segmentation distributes the chain engagement function across different tooth types, allowing the protruded teeth to provide enhanced guidance and stability during high-load conditions, while the non-protruded teeth in the second group provide alternative engagement points that reduce overall stress concentration on any single tooth structure.
Solution Approach 2:
The chainring employs asymmetric tooth geometry where teeth in the first group have protrusions on their outboard sides, creating an asymmetric profile that differs from the symmetric or simpler geometry of conventional teeth and the second group. This asymmetry is strategically designed to guide the chain more effectively during the power stroke when high loads are applied, improving engagement stability without proportionally increasing damage risk through balanced load distribution across the alternating tooth groups.
3Reliability
If alternating groups of teeth with different geometries are used, then chain tension management is improved, but the manufacturing complexity increases
Solution Approach 1:
The tooth geometry is segmented into two repeatable groups that alternate around the chainring. This segmentation into standardized, repeating patterns simplifies the manufacturing process compared to completely unique tooth designs, as the same two tooth types are reused multiple times. The alternating pattern creates a manageable manufacturing workflow where tooling and fixtures can be designed to produce these two specific tooth geometries repeatedly, balancing improved chain tension management with reasonable manufacturing complexity.
Solution Approach 2:
The tooth geometry follows a periodic pattern where the first group and second group of teeth alternate in a regular sequence around the chainring. This periodic arrangement allows for standardized manufacturing processes that can efficiently produce repeating units, reducing overall manufacturing complexity despite the presence of multiple tooth geometry types. The periodic nature enables modular production approaches and simplifies quality control and inspection procedures.
Data Source
Figure 1~2
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AI summary
A solitary chainring (50) of a bicycle front crankset for engaging a drive chain (10), including a plurality of teeth (52) formed about a periphery of the chainring (50), the plurality of teeth (52) consisting of an even number. The plurality of teeth (52) includes a first group of teeth (58) and a second group of teeth (60) arranged alternatingly between the first group of teeth (58). The first group of teeth (58) and the second group of teeth (60) are equal in number. Each of the first and second group of teeth include an outboard side (54) and an inboard side (56) opposite the outboard side and each tooth of the first group of teeth (58) includes at least a first protrusion on the outboard side (54) thereof and each tooth of the second group of teeth (60) are free of the first protrusions on the outboard side (54) and the inboard side (56).