Bicycle Gearshift Unidirectional Damping Device
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Solution Overview
Problem
Existing bicycle gearshifts with unidirectional damping devices are bulky and have limited torque transmission, leading to inefficiencies and a higher risk of chain detensioning and dropping, especially on irregular road surfaces.
Innovation Solution
A compact unidirectional damping device using a pair of ring nuts with front saw-toothings and an actuation system that engages the ring nuts to transfer torque in one direction, allowing for increased torque transmission and reliability, potentially made from light alloys or plastics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If roller bearings are used in unidirectional damping devices, then the device can dampen rocker arm oscillations, but the device becomes bulky and torque transmission is limited
Solution Approach 1:
The invention changes the fundamental operating parameters of the damping device by replacing roller bearings with a friction-based mechanism using ring nuts with saw-toothing. This allows the device to achieve damping functionality through friction forces generated during relative rotation, fundamentally altering how the damping effect is produced and enabling a more compact design
Solution Approach 2:
The invention extracts the essential damping function from the bulky roller bearing structure and implements it through a simplified friction-based mechanism. By removing the complex roller bearing components and retaining only the necessary friction-generating elements (ring nuts with saw-toothing), the device achieves the same damping effect in a much more compact form
2Reliability
If roller bearings are used in unidirectional damping devices, then oscillation damping is achieved, but maximum transmissible torque is very limited
Solution Approach 1:
The invention changes the force transmission mechanism from roller bearing contact to friction-based contact through saw-toothing engagement. This allows the damping device to transmit significantly higher torques by utilizing friction forces that can be optimized through the geometry and material properties of the ring nuts
Solution Approach 2:
The invention employs composite construction with ring nuts made from light alloys or plastics combined with friction surfaces. This allows optimization of both strength properties for high torque transmission and weight reduction, achieving a balance that roller bearings cannot provide
3Ease of operation
If the rocker arm is subjected to oscillations in the direction opposite to chain tensioning, then chain detensioning occurs, but this increases the risk of chain dropping
Solution Approach 1:
The invention converts the harmful oscillatory movements that cause chain detensioning into a beneficial damping effect. By using a unidirectional friction-based mechanism, the oscillations are resisted when they threaten to detension the chain, while normal operational movements are allowed to proceed freely
Solution Approach 2:
The friction-based damping device acts as an intermediary between the rocker arm oscillations and the chain tensioning system. It mediates the oscillatory forces by providing controlled friction resistance, preventing these oscillations from translating into harmful chain detensioning while allowing normal chain engagement
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
The solution provides a more compact and efficient damping mechanism that increases the maximum transmissible torque by up to five times, reducing the risk of chain detensioning and enhancing the reliability of the gearshift.
Implementation Method 1
an elastic element configured to push said rocker arm in rotation about said rotation axis in a first direction of rotation
Implementation Method 2
configured to apply a friction force to said rocker arm when said rocker arm is moved about said rotation axis in a second direction of rotation opposite to said first direction of rotation
Data Source
Figure 1
Figure 2
Figure 3~3a
AI summary
The invention relates to a bicycle gearshift (10) comprising a first body configured to be associated with a bicycle frame, a second body (36) connected to, and moveable with respect to, said first body, a rocker arm (20) rotatably connected to the second body (36) at a predetermined rotation axis (X), an elastic element (40) configured to push the rocker arm (20) in rotation about said rotation axis (X) in a first direction of rotation, and an unidirectional damping device (50) operatively arranged between the rocker arm (20) and the second body (36) and configured to apply a friction force to the rocker arm (20) when the rocker arm (20) is moved about said rotation axis (X) in a second direction of rotation opposite to said first direction of rotation. The unidirectional damping device (50) comprises a first ring nut (52) arranged coaxially to said rotation axis (X) and rotatable as a unit with said rocker arm (20) about said rotation axis (X) and a second ring nut (54) arranged coaxially to said rotation axis (X) in a position axially adjacent to the first ring nut (52). The first ring nut (52) comprises a first front saw-toothing (52a) and the second ring nut (54) comprises a second front saw-toothing (54a) matching the first front toothing (52a). An actuation system (56) of the unidirectional damping device (50) is also provided, said actuation system (56) acting on one (52) of said ring nuts (52, 54) to axially push said ring nut (52) towards the other ring nut (54) so as to mutually engage said first front toothing (52a) and said second front toothing (54a) when the rocker arm (20) is moved about the rotation axis (X) in said second direction of rotation. A first friction surface (58a) is part of, or is associated with, said second ring nut (54) and a second friction surface (60a) is part of, or is associated with, said second body (36) and is configured to slide on the first friction surface (58a) when the rocker arm (20) is moved around the rotation axis (X) in said second direction of rotation.