Narrow-Wide Chainring Teeth for Mud-Resistant Chain Guidance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing chainrings with alternating narrow and wide teeth face challenges in maintaining effective chain guidance and engagement, especially in muddy or soiled environments, due to increased weight and resistance from protrusions extending over the entire lateral face of wide teeth.
Innovation Solution
The sprocket design features wide teeth with protrusions that extend over only half the lateral face, providing reduced weight and surface area, allowing easier penetration into link spaces and reducing resistance, while maintaining effective lateral guidance through a T-shaped configuration with chamfered edges and rounded tips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protrusions extend over the entire lateral face of wide teeth, then chain guidance is improved, but weight and surface area increase
Solution Approach 1:
The protrusion on each wide tooth is segmented into two distinct portions: a first portion extending from the tooth tip to a first distance, and a second portion extending from the tooth tip to a second distance greater than the first distance. This segmentation allows different regions of the protrusion to serve different functions - the first portion provides chain guidance while the second portion provides structural support, thereby reducing weight while maintaining guidance effectiveness.
Solution Approach 2:
The protrusion is designed with non-uniform dimensions along its length, creating local quality variations. The first portion has different cross-sectional dimensions compared to the second portion, optimizing material distribution. This allows the tooth to have sufficient strength where needed while minimizing material usage in regions where full coverage is not required, thus reducing overall weight while maintaining chain guidance functionality.
2Reliability
If protrusions extend over the entire lateral face of wide teeth, then chain guidance is improved, but resistance in link spaces increases
Solution Approach 1:
The protrusion is divided into two portions with different extents along the lateral face. The first portion extends to a first distance while the second portion extends to a greater second distance. This segmented approach ensures that the protrusion provides guidance only where necessary (where the chain contacts the tooth) while minimizing the surface area that would otherwise increase resistance when passing through link spaces, particularly in soiled conditions.
Solution Approach 2:
Rather than providing full-length protrusions across the entire lateral face, the invention applies partial action by limiting the protrusion extent to specific portions. The first portion provides sufficient guidance functionality, while the reduced overall extent minimizes resistance in link spaces. This partial action approach eliminates the excessive material that would create unnecessary resistance without compromising the essential chain guidance function.
3Reliability
If protrusions extend over the entire lateral face of wide teeth, then chain engagement is improved, but material usage increases
Solution Approach 1:
The protrusion material is segmented into two portions with different extents and cross-sectional dimensions. The first portion extends to a first distance with specific dimensions, while the second portion extends to a greater second distance with different dimensions. This segmentation optimizes material distribution, providing chain engagement functionality only where contact occurs while reducing material usage in non-contact regions.
Solution Approach 2:
The tooth structure exhibits local quality variations through the differentiated protrusion portions. Material is concentrated in regions where chain engagement is required (with appropriate dimensions and strength) while minimizing material in regions where it is not needed. This local quality optimization reduces overall material usage while maintaining effective chain engagement at the contact points.
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
A sprocket (11) for engagement with a drive chain (15) comprises: • a plural ity of teeth (12; 16) extending radially from a periphery of the sprocket (11); • the plurality of teeth (12; 16)including a first and a second group of teeth, wherein the teeth of the first group and the second group are alternately arranged so that each tooth (12) of the first tooth group is followed by a tooth (1 6) of the second group, and vice versa; • each tooth (12) of the first group of teeth having a first maximum width; • each tooth (16) of the second group of teeth having a second maximum width which is larger than the first maximum width, wherein each tooth (16) of the second group of teeth has a protrusion (17, 18) on at least one lateral face of the tooth; In order to provide a sprocket with alternating narrow and wide teeth that has a low weight and remains functional in a muddy environment with a soiled chain, the outer lateral face of the protrusion (17, 18) extends over a first portion of the lateral face (19, 20) of each tooth (16) of the second group of teeth, wherein the length of the first portion is 50% of the length of the respective tooth (16) or less.