Alternating-Tooth Chainring for Stable Chain Engagement on Rough Terrain
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Solution Overview
Problem
Managing chain engagement and preventing frame damage in bicycles, especially when riding over rough terrain, is challenging due to severe chain tension and potential contact with the chain stay, leading to elastic deformation and damage.
Innovation Solution
A solitary chainring with alternating groups of teeth, where the first group has protrusions on both sides and a cross-shaped cross section, and the second group has a rectangular cross section and recesses, designed to engage with different chain link spaces, guiding and maintaining the chain effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional chainring with uniform teeth is used, then the structure is simple, but the chain engagement is inconsistent leading to poor chain management on rough terrain
Solution Approach 1:
The chainring teeth are segmented into two distinct groups: first group teeth with protrusions on both sides and cross-shaped cross sections, and second group teeth with rectangular cross sections and recesses. This segmentation allows different tooth types to engage with different chain link spaces (outer and inner), providing consistent chain management across varying terrain conditions.
Solution Approach 2:
Different regions of the chainring have different tooth characteristics. The first group teeth have protrusions extending beyond the tooth tip on both sides with cross-shaped cross sections, while the second group teeth have rectangular cross sections with recesses. This local differentiation optimizes engagement with specific chain link spaces at different locations around the chainring.
2Reliability
If the chainring teeth are designed for optimal engagement, then chain management improves, but the risk of chain contact with chain stay increases causing frame deformation
Solution Approach 1:
By segmenting teeth into two groups with different geometries, the chain is guided more precisely along the chainring periphery. The alternating pattern of protruding and recessed teeth creates a more controlled chain path, reducing lateral chain movement and the likelihood of chain contact with the chain stay, thereby preventing frame deformation.
Solution Approach 2:
The alternating protrusions and recesses act as intermediaries that guide and constrain the chain. The protrusions on first group teeth engage with outer link spaces while recesses between second group teeth engage with inner link spaces, creating an intermediary guidance system that keeps the chain properly positioned and prevents harmful contact with the frame.
3Ease of operation
If alternating tooth groups with different geometries are used, then chain guidance is improved, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into creating two distinct tooth types. First group teeth are formed with protrusions on both sides and cross-shaped cross sections, while second group teeth are formed with rectangular cross sections and recesses. This segmentation allows for specialized tooling and processes for each tooth type, potentially simplifying the overall manufacturing approach despite the complexity of individual tooth geometries.
Data Source
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AI summary
A 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 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 includes at least a first protrusion on the outboard side thereof and each tooth of the second group of teeth are free of the first protrusions on the outboard side and the inboard side.