Composite Chain Roller Structure for Stiff, Self-Cleaning Derailleurs

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Solution Overview

Problem

Conventional chain rollers for bicycle gearshift mechanisms face issues with low stiffness, precision, and self-cleaning due to material limitations, particularly in adverse weather conditions, where contaminants accumulate and increase wear, leading to potential blockages and damage.

Innovation Solution

A chain roller design featuring a toothed ring made of plastic and a support structure made of metal, connected in a positively locking fashion, allowing for high precision and stiffness while enabling self-cleaning and overload protection through a frictional connection that allows the toothed ring to rotate independently if blocked.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If chain rollers are produced from plastics by injection moulding, then production cost is reduced and design freedom is increased, but lateral stiffness and manufacturing precision deteriorate

Engineering Contradiction:

Improveproduction costVSAvoidlateral stiffness

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The chain roller combines plastic and metal materials in a composite structure. The plastic toothed ring provides design freedom and damping characteristics, while the metal support structure provides lateral stiffness and structural strength. This composite approach resolves the contradiction between low-cost plastic construction and the need for high lateral stiffness.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If chain rollers are produced from plastics by injection moulding, then production cost is reduced, but precision of pitch circle diameter and lateral runout deteriorate

Engineering Contradiction:

Improveproduction costVSAvoidpitch circle diameter precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The metal support structure with precisely manufactured pitch circle serves as the foundation, while the plastic toothed ring is molded onto it. This composite construction allows the precision-critical pitch circle to be defined by the metal component, which can be manufactured with high precision, while the plastic portion provides cost-effective design freedom.

Inventive Principle:

Principle #40Composite materials

3Strength

If support structure of conventional plastic chain rollers is made massive with few cutouts, then structural strength is maintained, but self-cleaning function deteriorates due to contaminant accumulation

Engineering Contradiction:

Improvestructural strengthVSAvoidself-cleaning function

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention extracts and removes material from the support structure to create numerous cutouts and open spaces. This extraction maintains structural strength through the metal material and strategic reinforcement while creating self-cleaning functionality by allowing contaminants to be expelled through the open structure during operation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The support structure is designed with a porous-like open structure featuring numerous cutouts and voids. This porous configuration enables self-cleaning by allowing contaminants to pass through and be ejected during chain roller operation, while the metal material and strategic web placement maintain necessary structural strength.

Inventive Principle:

Principle #31Porous materials

4Reliability

If large material cutouts are made in spoked support structure, then self-cleaning capability is improved, but risk of blockage by foreign bodies increases

Engineering Contradiction:

Improveself-cleaning capabilityVSAvoidblockage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The support structure features locally optimized quality with varying web thicknesses and strategically placed cutouts. Critical areas have reinforced structures to prevent blockage, while non-critical areas have open cutouts for self-cleaning. This local differentiation resolves the contradiction between self-cleaning capability and blockage resistance.

Inventive Principle:

Principle #3Local quality

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 design enhances lateral stiffness, precision, and self-cleaning capabilities, preventing damage from foreign bodies and maintaining optimal operation under various conditions, including adverse weather, while maintaining design freedom and cost-effectiveness.

Implementation Method 1

connected to one another radially and axially in a positively locking fashion, allowing for high precision and stiffness while enabling self-cleaning and overload protection through a frictional connection that allows the toothed ring to rotate independently if blocked

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11661143B2Gearshift mechanism roller

Publication Date: 2023.05.30 SRAM

AI summary

The disclosure relates to a chain roller for a rear bicycle gearshift mechanism. The chain roller comprising a rotatory bearing, a toothed ring with teeth formed thereon, and a support structure which connects the rotary bearing and the toothed ring. The toothed ring and support structure are formed from different materials and are connected to one another radially and axially.