Bicycle Derailleur Actuation Device with Switchable Pointer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mechanical actuation devices for bicycle derailleurs often face inefficiencies in upward gearshifting, leading to unstable and slow downward gearshifting due to incomplete recovery of the extra upward stroke, causing the transmission chain to be positioned off-center relative to the preselected sprocket.
Innovation Solution
A mechanical actuation device with a pointer that can switch between active and passive positions to selectively limit the angular play of the indexing bush, allowing partial or complete recovery of the extra rotation during upward gearshifting, ensuring precise positioning of the derailleur during both upward and downward shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the indexing bush is allowed to rotate freely during upward gearshifting, then the transmission chain can engage the preselected sprocket quicker, but the downward gearshifting becomes unstable and slow due to incomplete recovery of the extra upward stroke
Solution Approach 1:
The pointer is made movable between active and passive positions, allowing the system to dynamically adjust the angular play limitation of the indexing bush. This dynamic adjustment enables the system to optimize performance for different gearshifting directions: limiting angular play during upward shifts for speed, and allowing full recovery during downward shifts for stability.
Solution Approach 2:
The system changes the parameter of angular play of the indexing bush based on the pointer's position. When the pointer is in the active position, the angular play is limited; when in the passive position, the angular play is allowed to recover fully. This parameter change resolves the contradiction between speed and stability.
2Measurement precision
If the pointer limits the angular play of the indexing bush, then the positioning precision is improved, but the gearshifting speed may be reduced due to restricted movement
Solution Approach 1:
The limitation of angular play is applied locally and selectively rather than globally. The pointer limits angular play only in specific situations (when in the active position and during upward gearshifting), while allowing full movement in other situations (when in the passive position and during downward gearshifting). This local application resolves the contradiction between precision and speed.
3Reliability
If the indexing bush angular play is fully recovered, then the downward gearshifting stability is improved, but the upward gearshifting efficiency is reduced due to loss of extra stroke
Solution Approach 1:
The system dynamically controls the recovery of angular play based on the gearshifting direction and pointer position. During upward gearshifting with pointer in active position, recovery is limited to maintain efficiency. During downward gearshifting, full recovery is allowed to maintain stability. This dynamic control resolves the contradiction between stability and efficiency.
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 solution enhances responsiveness and efficiency by maintaining precise positioning of the derailleur during gear changes, ensuring stable and efficient shifting by adjusting the extra stroke recovery based on the pointer's position, thus improving gear engagement accuracy.
Implementation Method 1
the release of the control cable frees the elastic energy of such a spring
Implementation Method 2
the control cable is actuated in traction or in release through winding and unwinding on a rotor element, commonly called cable-winding bush
Data Source
Figure 1~8
Figure 2~3
Figure 4~5
AI summary
The invention relates to a mechanical actuation device (10) for actuating the control cable of a gearshift of a bicycle comprising a fixed casing (11), a control pin (12) rotatably mounted in the casing (11) about a rotation axis (X), a cable-winding bush (13) mounted coaxially and rotatable with the control pin (12) in a first angular direction (A) and in a second angular direction (B) opposite to the first, a ball-carrying bush (15) mounted in the casing (11) in a rotary manner about the rotation axis (X), rotating as a unit with the cable-winding bush (13) and equipped with at least one slider (16, 17). An indexing bush (20) is rotatable with respect to the control pin (12) with a rotational play with respect to the casing (11), the indexing bush (20) being provided with a plurality of stop positions (22) engageable in sequence by the slider (16, 17) during a relative rotation between the ball-carrying bush (15) and the indexing bush (20), each stop position (22) defining a stable angular position for the cable-winding bush (13). A pointer (30) is switchable between an active position in which it interacts with the indexing bush (20) to limit the angular play thereof with respect to the casing (11) and a passive position in which it does not interact with the indexing bush (20) and does not limit the angular p between the indexing bush (20) and the casing (11).