Bicycle Front Derailleur Variable Actuation Ratio
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Solution Overview
Problem
Conventional bicycle front derailleurs have fixed or erratic actuation ratios, which can lead to uneven effort requirements for shifting gears, particularly as the rider's hand position changes, making it difficult to maintain ergonomic operation.
Innovation Solution
A bicycle front derailleur with a variable actuation ratio is achieved through a control cable route adjuster that modifies the path of the control cable, allowing for a smoother transition of force application by varying the actuation ratio based on the position of the chain guide, thereby reducing the effort needed to shift gears across different hand positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed actuation ratio is used in the derailleur, then the structure is simple, but the shifting effort becomes uneven and difficult to operate ergonomically across different hand positions
Solution Approach 1:
The patent applies the dynamics principle by making the actuation ratio variable rather than fixed. The cable route adjuster changes the cable path dynamically based on the chain guide position, allowing the actuation ratio to adapt as the derailleur moves between different gear positions. This resolves the contradiction by providing ergonomic shifting effort across all positions while accepting increased mechanism complexity through the adjustable cable routing system.
2Ease of operation
If a variable actuation ratio mechanism is added to adjust the cable path, then the ergonomic operation is improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the cable route geometry through the cable route adjuster. By changing the physical parameters of the cable path (position, angle, length) based on the chain guide position, the system achieves variable actuation ratio that adapts to different hand positions. This resolves the contradiction by improving ergonomic operation while the complexity is contained within the adjustable routing mechanism rather than the entire derailleur system.
Data Source
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AI summary
A derailleur comprises a base member (110) structured to be attached to a bicycle frame member; a chain guide (122) operatively connected to the base member (110); and an actuation mechanism (118) coupled to the base member (110) and to the chain guide (122) for moving the chain guide (122) relative to the base member (110). The actuation mechanism (118) comprises: a first link (138) pivotably coupled to the base member (110) and to the chain guide (122); an actuating arm (130) coupled to the first link (138) for attaching a control cable; and a control cable route adjuster (134) provided on the actuating arm (130) for adjusting a route of the control cable.