Chainring Wide-Tooth Protrusions for Mud-Resistant Chain Guidance
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Solution Overview
Problem
Existing chainrings for bicycles with alternating narrow and wide teeth face challenges in maintaining effective chain guidance and engagement, especially in muddy or soiled environments, due to increased resistance and potential disengagement from shocks and vibrations.
Innovation Solution
The design features wide teeth with protrusions that extend over only half the lateral face, reducing weight and surface area, allowing easier penetration into link spaces and minimizing resistance, while maintaining effective lateral guidance through a T-shaped or cross-shaped configuration, and chamfered edges to avoid contact with inner chain links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wide teeth with protrusions extending over the entire lateral face are used, then lateral guidance of the chain is improved, but weight and surface area increase, causing higher resistance and noise
Solution Approach 1:
The protrusion on the wide tooth is segmented to extend over only a first portion of the lateral face rather than the entire length. This segmentation allows the tooth to provide lateral guidance where needed (at the front portion engaging the chain) while reducing material in the rear portion, thereby decreasing weight and surface area to minimize resistance and noise.
Solution Approach 2:
The protrusion is applied locally to the first portion of the lateral face where it is most effective for chain guidance, rather than uniformly across the entire tooth. This local application optimizes the guidance function at the critical engagement zone while reducing overall material usage and resistance.
2Reliability
If wide teeth with protrusions extending over the entire lateral face are used, then lateral guidance of the chain is improved, but resistance and noise increase due to increased surface area
Solution Approach 1:
The protrusion is segmented to cover only the necessary first portion of the lateral face, reducing the surface area that contacts the chain and surrounding environment. This segmentation maintains guidance effectiveness at the critical front portion while minimizing resistance and noise-generating surface area in the rear portion.
Solution Approach 2:
The protrusion is concentrated in the local region where chain guidance is most critical (the front portion of the tooth), allowing effective guidance with minimal surface area exposure that would generate resistance and noise.
3Reliability
If full-width protrusions are used on wide teeth, then chain guidance is improved, but material usage increases
Solution Approach 1:
The protrusion is segmented along the lateral face of the tooth, extending over only the first portion rather than the full width. This segmentation reduces the volume of material required for each tooth while preserving the guidance function where it is most needed for effective chain engagement.
Solution Approach 2:
Material is concentrated locally in the protrusion region where it provides maximum guidance benefit, rather than distributing material uniformly across the entire tooth. This local quality approach minimizes overall material usage while maintaining effective chain guidance.
Data Source
AI summary
A sprocket for engagement with a drive chain has a plurality of teeth extending radially from a periphery of the sprocket, including a first and a second group of teeth; the teeth of the first group and the second group are alternately arranged so that each tooth of the first group is followed by a tooth of the second group, and vice versa; each tooth of the first group having a first maximum width, each tooth of the second group having a second maximum width which is larger than the first maximum width; each tooth of the second group has a protrusion on at least one lateral face of the tooth; the outer lateral face of the protrusion extends over a first portion of the lateral face of each tooth of the second group, the length being 50% of the length of the respective tooth or less.