Bicycle Front Derailleur Actuator with Elastic Decoupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing actuation devices for front derailleurs on bicycles suffer from reduced responsiveness in the first upward gearshifting due to the adjustment of mechanical end stops, which results in a lower effective excursion and instability in gearshifting operations.
Innovation Solution
The actuation device incorporates a control pin, a cable-winding bush, and an indexer with elastic members that allow the control pin to rotate with respect to the cable-winding bush, enabling stable positioning and reduced tension in the control cable, thereby improving responsiveness and eliminating the need for additional stop areas to recover tension before the first upward gearshifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control pin is rigidly connected to the cable-winding bush, then the gearshifting operation is stable, but the responsiveness in the first upward gearshifting is reduced due to cable tension recovery requirements
Solution Approach 1:
The connection between the control pin and cable-winding bush is made dynamic through elastic members (torsion spring) instead of rigid fixation. This allows the system to adapt its stiffness characteristic: flexible during tension recovery and rigid during positioning, thereby improving both responsiveness and stability
Solution Approach 2:
The elastic members change the mechanical parameter (torque transmission) between the control pin and cable-winding bush based on the operational phase. During first upward gearshifting, the elastic members allow relative rotation to recover cable tension; during normal operation, they transmit torque rigidly for stable positioning
2Reliability
If additional stop areas are added to the indexer to allow cable tension recovery, then the gearshifting stability is improved, but the device complexity increases
Solution Approach 1:
The tension recovery function is merged into the existing indexing mechanism by allowing the control pin to rotate relative to the cable-winding bush within the same indexing structure. This eliminates the need for separate stop areas while maintaining stability through the elastic members
3Adaptability or versatility
If the derailleur excursion is increased to cover all gearshifting operations, then the adaptability to different mounting configurations is improved, but the effective excursion is reduced due to mechanical end stops
Solution Approach 1:
The elastic members perform preliminary action by allowing the control pin to rotate ahead of the cable-winding bush to recover cable tension before the actual gearshifting movement begins. This preliminary tension recovery eliminates the need for reduced effective excursion while maintaining adaptability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures immediate and rapid upward gearshifting by stabilizing the derailleur's position at the inner end stop and allowing the control pin to reach the last stop area without further rotating the cable-winding bush, maintaining synchrony and reducing the torque required for gearshifting operations.
Implementation Method 1
elastic members active between said control pin and said cable-winding bush configured to fixedly connect the control pin to the cable-winding bush during rotations of the latter between the first winding position and the last winding position and between the last winding position and the first winding position and to make said control pin rotatable with respect to said cable-winding bush between the last winding position of the cable-winding bush and the last angular position of the control pin
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to an actuation device (10) for actuating the front derailleur of a bicycle, comprising a control pin (12), configured to be set in rotation by a control lever, rotatable about a rotation axis (X) in a first angular direction (A) between a first angular position and a last angular position and in a second angular direction (B) between the last angular position and the first angular position, a cable-winding bush (13) angularly rotatable about the rotation axis (X) to wind a control cable between a first winding position and a last winding position and vice-versa, an indexer (11) configured to define a plurality of stop areas (20) for the rotation of the control pin (12), each area (20) corresponding to an angular position comprised between the first angular position and the last angular position of the control pin (12). Elastic members (21) are active between the control pin (12) and the cable-winding bush (13) and are configured to make the control pin (12) form a unit with the cable-winding bush (13) during rotations of the latter between the first winding position and the last winding position and between the last winding position and the first winding position and to make the control pin (12) rotatable with respect to the cable-winding bush (13) between the last winding position of the cable-winding bush (13) and the last angular position of the control pin (12).