Single Bicycle Chainring Tooth Geometry to Prevent Chainsuck
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Solution Overview
Problem
Single sprockets in bicycle front crank assemblies experience wear-related material removal at load flanks, leading to chain blockage and 'Chainsuck' issues, as chain rollers dig into the teeth, causing edges that prevent chain run-out and increased susceptibility to radial jumping.
Innovation Solution
Designing the single sprocket with geometrically arranged load flanks and profiling that allows for wear without edge formation, featuring flat load flank angles (110°-125°) to distribute force over multiple teeth, reducing wear and preventing chain blockage, along with projections to secure the chain and recesses to manage wear without impeding disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the load flanks of the teeth are designed with steep angles to prevent chain jumping, then the chain is secured against radial jumping, but the chain rollers dig into the load flanks causing wear and edge formation that blocks chain run-out
Solution Approach 1:
The patent changes the geometric parameters of the load flanks by introducing flat angles (110°-125°) instead of steep angles, and by providing recesses at specific positions. This parameter change allows the chain rollers to ride on the flat surfaces without digging in, preventing wear edge formation while maintaining chain security through the projection geometry
Solution Approach 2:
The patent adds a new dimensional feature by providing recesses in the load flanks at specific distances from the tooth peak. This creates a multi-level surface geometry where the recess depth and position are carefully controlled to prevent chain roller engagement with the tooth root, thereby preventing wear-induced edge formation while maintaining chain retention
2Loss of substance
If the load flanks are designed with flat angles (110°-125°) to distribute force and reduce wear, then wear is reduced and chain run-out is maintained, but the chain may become susceptible to radial jumping
Solution Approach 1:
The patent modifies the load flank geometry by specifying flat angles in the range of 110°-125°, which is a significant deviation from conventional steep angles. This parameter change distributes the chain load over a larger surface area, reducing contact pressure and wear rate, while the associated projection geometry maintains chain retention
Solution Approach 2:
The patent applies different geometric qualities to different regions of the tooth structure. The load flanks have flat angles for wear reduction, while the projections and recesses create localized features that secure the chain. This local differentiation allows each region to perform its specific function optimally
3Device complexity
If the sprocket uses a single tooth design without recesses, then the structure is simpler, but wear edges form that block chain run-out and cause Chainsuck
Solution Approach 1:
The patent incorporates recesses in the load flanks during the manufacturing process, before the sprocket is put into service. This preliminary action pre-prevents the formation of wear edges by providing a geometry that guides the chain roller away from the tooth root, eliminating the Chainsuck problem before it can occur during operation
Solution Approach 2:
The patent segments the load flank surface by introducing recesses that divide the continuous surface into distinct regions. This segmentation creates a profiled geometry where the recesses prevent chain roller engagement with the vulnerable tooth root areas, thereby preventing wear edge formation while adding minimal structural complexity
Data Source
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AI summary
The invention relates to a single chainring (10) for a bicycle front crank assembly for engaging with a drive chain, comprising a plurality of teeth (12, 14) formed on a circumference of the chainring (10), which has a first and a second tooth group, wherein the teeth (14) of the second tooth group are arranged alternately between the teeth (12) of the first tooth group, wherein each tooth (12, 14) has a load flank (16) via which a force transmission takes place between a chain roller (30) of the drive chain abutting it and the respective tooth (12, 14), and wherein each tooth (12) of the first group has at least one profile with a recess (18) near the flank into which a section of an inner link of the drive chain extending beyond the chain roller (30) engages.In this single sprocket, it is provided that the load flank (16) and the profile of at least one tooth (12) of the first tooth group are geometrically designed and arranged in such a way as to ensure that, even in the case of wear-involving stress on the load flank (16) as a result of the force transmission via the chain rollers (30) during operation of the single sprocket (10), an unimpeded disengagement of the respective chain roller (30) in contact with the load flank (16) and the tooth (12) is ensured.