Variable-Radius Bicycle Drivetrain With Movable Pins

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Solution Overview

Problem

Conventional bicycle drivetrains with multiple gears face issues such as cross-loading, binding, increased width, and reduced reliability due to the need for axial shifting between fixed radius gears, which affects aerodynamics, internal friction, and weight.

Innovation Solution

A gearless drivetrain system utilizing a power transmission belt engaged with input and output interfaces featuring concentric rings of movable pins, allowing for variable ratios without lateral movement of the belt, and actuated through mechanical, electromechanical, or pneumatic mechanisms to adjust the interface radii.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional bicycle drivetrains use multiple gears with axial shifting, then variable gearing ratios are achieved, but cross-loading and binding occur, reducing reliability

Engineering Contradiction:

Improvevariable gearing ratiosVSAvoiddrivetrain reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs movable pins that can dynamically change their radial position within the input and output interfaces. These pins move between different concentric circles, allowing the effective radius to change continuously without discrete gear shifts. This dynamic adjustment eliminates cross-loading and binding while maintaining reliable power transmission, as the belt remains engaged with the pins throughout the adjustment process.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the geometric parameter of the interface radius by moving pins between different concentric circles. Instead of changing gears, the system varies the effective radius of the input and output interfaces, thereby achieving variable gearing ratios. This parameter change approach maintains continuous belt engagement and avoids the reliability issues associated with axial shifting between fixed gears.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If multiple gears are used for variable gearing, then adaptability is improved, but device width increases

Engineering Contradiction:

Improvegearing variabilityVSAvoiddrivetrain width

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The movable pins within a single interface plane allow for continuous radius adjustment without requiring multiple discrete gears stacked axially. This dynamic system achieves variable gearing within a compact width, eliminating the need for wide gear stacks while maintaining adaptability across different terrains and riding conditions.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If axial shifting between fixed radius gears is implemented, then gearing ratios are variable, but internal friction increases

Engineering Contradiction:

Improvegearing ratiosVSAvoidinternal friction

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The continuous movement of pins along concentric circles within the same interface plane eliminates the need for axial shifting between discrete gears. This dynamic adjustment mechanism maintains constant belt engagement and reduces internal friction by avoiding the disengagement and re-engagement losses inherent in traditional gear shifting systems.

Inventive Principle:

Principle #15Dynamics

4Power

If conventional gear systems are used, then power transmission is achieved, but aerodynamics are degraded

Engineering Contradiction:

Improvepower transmissionVSAvoidaerodynamic drag

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The compact single-plane interface with movable pins creates a more aerodynamic drivetrain profile compared to wide multi-gear systems. The continuous radius adjustment capability within this compact form factor maintains power transmission efficiency while reducing aerodynamic drag, as the drivetrain presents a smaller cross-sectional area to the airflow.

Inventive Principle:

Principle #15Dynamics

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 improves aerodynamics, reduces internal friction and weight, enhances reliability, and extends the operational lifetime of components by maintaining a single chainline and allowing for wireless actuation, while providing efficient power transmission and adjustable drive ratios.

Implementation Method 1

The power transmission belt is engaged with the input interface and output interface to transmit force from the input interface to the output interface

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11945546B2Bicycle drivetrain

Publication Date: 2024.04.02 MEJIA COBO MARCELO ALONSO

AI summary

A pedal drivetrain includes an input interface, an output interface, and a power transmission belt. The power transmission belt is engaged with the input interface and output interface to transmit force from the input interface to the output interface. At least one of the input interface and the output interface includes a plurality of movable pins engaged with the power transmission belt.