Bicycle Gearshift Actuator Snap Mechanism Knock Protection
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Solution Overview
Problem
Existing actuator devices for bicycle gearshifts with motorized actuation are compromised by minor damage from knocks, leading to precision issues and potential breakage, and existing solutions are either complex or require replacement of parts.
Innovation Solution
An actuator device with a snap mechanism between the nut and drive shaft that absorbs excess forces by transitioning from an engaged to a release configuration, allowing complete release of the kinematic mechanism without residual deformations or part breakage, and enabling manual operation and easy mounting/dis mounting of wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clutch device with torsion spring is used to protect against excess forces, then the gearshift is protected from knocks, but the device becomes complicated and bulky
Solution Approach 1:
The invention extracts the protective function from the complex clutch device and implements it through a simple snap mechanism with a ball and seat. The ball can be disengaged from the seat when excessive force is applied, providing protection without requiring multiple gear wheels, torsion springs, or complex clutch components.
Solution Approach 2:
The snap mechanism uses a simple ball and seat arrangement that can be easily replaced if damaged. The ball is a simple, inexpensive component that can be quickly replaced without requiring complex disassembly or specialized tools, making it a cost-effective protective solution.
2Reliability
If a spring-loaded nut is used to absorb excess forces, then the kinematic mechanism is protected, but the spring and collar may break under high excess force
Solution Approach 1:
The ball in the snap mechanism is designed as a simple, replaceable component that can be easily replaced if damaged by excessive force. This eliminates the need for complex spring and collar assemblies that would be difficult and expensive to replace if they failed.
Solution Approach 2:
The invention removes the spring and collar components from the protective mechanism, replacing them with a simple snap mechanism that uses a ball and seat arrangement. This simplifies the structure and eliminates the risk of spring and collar breakage.
3Manufacturing precision
If the nut is firmly engaged with the drive shaft, then the actuation is precise, but the mechanism cannot release under knock to prevent damage
Solution Approach 1:
The snap mechanism provides a dynamic connection between the nut and drive shaft. Under normal operation, the ball is seated in the seat providing firm engagement for precise actuation. Under excessive force, the ball can disengage from the seat, allowing the connection to become flexible and absorb the knock energy.
Solution Approach 2:
The mechanism changes its engagement parameter based on the applied force. At normal operating forces, the ball remains seated providing high engagement. When excessive force is applied, the ball disengages from the seat, changing the engagement parameter to allow energy absorption while maintaining connection through the deformed seat.
4Reliability
If the tooth slips out of the seat to absorb excess force, then the kinematic mechanism is protected, but the coupling surfaces require large contact area for normal operation
Solution Approach 1:
The invention extracts the protective function from the tooth-and-seat slipping mechanism and implements it through a separate ball-and-seat snap mechanism. This allows the coupling surfaces to maintain small, efficient contact areas while still providing effective protection against excess forces through the ball's disengagement.
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 snap mechanism effectively absorbs knocks and deformations, maintaining the actuator's integrity and allowing for manual operation, reducing the risk of damage and simplifying maintenance, while maintaining the gearshift's precision and functionality.
Implementation Method 1
the snap mechanism absorbs excess forces by deforming
Implementation Method 2
a preloaded spring, housed in the first cavity of the tubular body and acting on said ball to push it towards the tubular sleeve along said first direction
Implementation Method 3
a threaded drive shaft put in rotation by the motor
Data Source
AI summary
An actuator device for a bicycle gearshift, comprising an actuation kinematic mechanism adapted to be deformed in order to move a derailleur of the gearshift; a driving member adapted to control the deformation of the aforementioned kinematic mechanism, the driving member comprising a motor and a threaded drive shaft put in rotation by the motor; a nut associated with the aforementioned kinematic mechanism and with the drive shaft. The actuator device comprises a snap mechanism that, in a first operative configuration, holds the nut in an engaged condition with the drive shaft such that the rotation of the drive shaft causes the deformation of the actuation kinematic mechanism and that, when the actuator device is subjected to a force greater than a predetermined threshold force, defines a release configuration in the nut, such that the rotation of the drive shaft does not cause the deformation of the actuation kinematic mechanism.