Bicycle Rear Derailleur Chain Guide Width and Curvature
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Solution Overview
Problem
Conventional bicycle rear derailleurs face issues with chain disengagement, where the chain disengagement prevention part can become caught in sprockets, and the chain may fail to return to the guide pulley, leading to potential derailleur damage and gear shifting problems.
Innovation Solution
A redesigned bicycle rear derailleur with a chain disengagement prevention part of a specific width (10 mm or greater and 50 mm or less) positioned closer to the guide pulley, and a curvilinear outer edge on the plate member to facilitate easy chain re-engagement, ensuring the chain can return to the guide pulley even if it slips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the chain disengagement prevention part is formed with a narrow width in conventional derailleurs, then the structure is simpler and manufacturing is easier, but the chain can become caught in sprocket teeth causing derailleur damage
Solution Approach 1:
The patent changes the width parameter of the chain disengagement prevention part from narrow (conventional) to wide (10-50mm). This parameter change prevents the chain from becoming caught in sprocket teeth while maintaining manufacturing feasibility through standard plate bending processes.
Solution Approach 2:
The patent positions the chain disengagement prevention part closer to the guide pulley in the radial dimension, and extends it wider in the tangential dimension. This dimensional repositioning ensures the prevention part intercepts the chain before it can engage with sprocket teeth, solving the reliability issue.
2Ease of operation
If the chain disengagement prevention part is positioned farther from the guide pulley in conventional derailleurs, then the chain guide can swing more freely, but the chain cannot return to the guide pulley after slipping off
Solution Approach 1:
The patent positions the chain disengagement prevention part closer to the guide pulley, creating a preliminary barrier that guides the chain back toward the pulley before the chain can completely disengage. This preliminary positioning ensures the chain follows the correct path back to the guide pulley.
3Volume of moving object
If the guide pulley supporting part has a small diameter in conventional derailleurs, then the structure is more compact, but the chain can be easily moved out of alignment during gear shifting
Solution Approach 1:
The patent introduces a curvilinear outer edge on the plate member that forms a smooth curved surface guiding the chain back to the guide pulley. This curvature design maintains compact dimensions while providing stable chain guidance through the curved geometry that naturally directs the chain along the intended path.
Data Source
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AI summary
The chain guide of a bicycle rear derailleur is a chain guide which is connected to a movable member (12) so that this guide is free to swing about a center pivot axis. The chain guide has a pair of plate members (20,21) rotatably supporting a guide pulley (22) and a tension pulley (23). One of the plate members is provided with a chain disengagement prevention part (35) which is disposed between both plate members (20,21) in the vicinity of the guide pulley (22). The chain disengagement prevention part (35) has a width of ten mm or greater and fifty mm or less.