Coaxial Rear Derailleur Mounting for Precise Shifting Alignment
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Solution Overview
Problem
Conventional rear derailleurs face issues with positioning accuracy due to frame tolerances, increased leverage forces, instability, and misshifting, particularly with large sprocket sets and slant parallelogram designs, which complicate assembly and adjustment.
Innovation Solution
A rear derailleur with a base element featuring two axially spaced arms for coaxial mounting on the rear wheel axle, incorporating a straight parallelogram four-bar linkage and a pivoting mechanism, which ensures stable alignment and absorbs forces, minimizing tilting and unintended shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate derailleur hanger is used to attach the derailleur to the frame, then the derailleur can be mounted with some flexibility, but the positioning accuracy deteriorates due to accumulated tolerances
Solution Approach 1:
The patent removes the separate derailleur hanger component entirely, integrating the mounting function directly into the frame structure. The derailleur is mounted coaxially to the rear axle through the frame's dropout, eliminating the intermediate hanger component that caused tolerance accumulation. This extraction of the problematic component resolves the contradiction by maintaining adaptability through direct frame integration while improving positioning accuracy by eliminating the additional tolerance interface.
2Adaptability or versatility
If derailleur dimensions are increased to accommodate large sprocket sets, then more sprockets can be engaged, but positioning accuracy deteriorates due to increased leverage forces causing tilting
Solution Approach 1:
The patent changes the mounting dimension from offset (non-coaxial) to coaxial alignment with the rear axle. By positioning the derailleur's pivot axis coincident with the rear axle centerline, the design creates a more favorable force geometry where leverage forces act through the axis rather than creating tilting moments. This dimensional change allows large sprocket sets to be engaged while maintaining positioning accuracy by eliminating the tilting problem inherent in offset mounting configurations.
3Ease of operation
If conventional coaxial derailleurs use a slant parallelogram pivoting mechanism, then the derailleur can pivot to engage different sprockets, but reliability deteriorates due to unintended shifting from vertical impacts
Solution Approach 1:
The patent changes the parallelogram mechanism from a slant (asymmetric) configuration to a straight (symmetric) configuration where the parallelogram links are aligned parallel to the direction of chain movement. This symmetric arrangement ensures that vertical impacts from road surfaces act equally on both sides of the mechanism, preventing asymmetric forces that cause unintended shifting. The symmetric design maintains full shifting capability while eliminating the ghost shifting problem caused by the asymmetric slant parallelogram under vertical loads.
4Ease of manufacture
If the derailleur is directly attached to the frame, then assembly is simplified, but positioning accuracy deteriorates due to frame manufacturing tolerances
Solution Approach 1:
The patent changes the reference parameter from frame-based mounting to axle-based coaxial mounting. By referencing the derailleur position to the rear axle centerline rather than frame features, the design isolates the positioning system from frame manufacturing tolerances. The derailleur's coaxial mounting to the axle provides a stable, precision reference that is independent of frame variability, maintaining assembly simplicity while dramatically improving positioning accuracy by changing the fundamental reference parameter.
Data Source
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AI summary
The invention relates to a rear derailleur for coaxial mounting on a rear wheel axle. The derailleur comprises a base element, a pivoting mechanism, a movable element, and a chain guide assembly. The pivoting mechanism connects the base element to the movable element. The chain guide assembly is rotatably connected to the movable element about a pivot axis. The base element includes a first connecting end, which can be mounted coaxially with the rear wheel axle, and a second connecting end for coupling with the pivoting mechanism.