Axially Shifted Bicycle Cassette for Straight Chain Alignment

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Solution Overview

Problem

Bicycle transmission systems suffer from inefficiencies due to the suboptimal orientation of the endless drive member when meshing with outermost sprockets, leading to increased friction losses and wear, particularly when the drive member extends askew between the front chain wheel and rear cassette.

Innovation Solution

A transmission system with a cassette of sprockets that rotates about a rotational axis, allowing axial movement via a driver element and shifting unit, ensuring optimal alignment of the endless drive member with sprockets, maintaining a straight chain line, and utilizing a shifting unit with an actuator element to facilitate smooth gear changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a derailleur is used to shift the endless drive member between sprockets, then gear changing is achieved, but the endless drive member becomes misaligned with outermost sprockets causing increased friction and wear

Engineering Contradiction:

Improvegear changing capabilityVSAvoidfriction losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The invention moves the cassette axially along the drive member in the third dimension, rather than using a derailleur to laterally shift the drive member. This axial movement in a different dimension allows the cassette to reposition itself while maintaining proper alignment of the drive member with all sprockets, eliminating the misalignment friction problem.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Instead of moving the drive member laterally between fixed sprockets (conventional approach), the invention inverts the approach by moving the entire cassette axially along the stationary drive member. This inversion allows the sprockets to engage the drive member at optimal angles while maintaining a straight chain line.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If a derailleur is used to shift the endless drive member between sprockets, then gear changing is achieved, but wear of the endless drive member and sprockets increases

Engineering Contradiction:

Improvegear changing capabilityVSAvoidcomponent wear

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The axial movement of the cassette along the drive member in the third dimension enables gear changing without lateral shifting of the drive member. This maintains optimal engagement geometry between the drive member and all sprockets, significantly reducing wear on the endless drive member and sprocket teeth.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The cassette is designed with dynamic axial mobility along the drive member, allowing it to shift positions smoothly between gear configurations. This dynamic adjustment capability ensures continuous optimal alignment during gear changes, reducing impact and wear compared to fixed-position derailleur systems.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If the endless drive member extends askew between front chain wheel and rear cassette, then gear changing is possible, but friction losses increase and efficiency decreases

Engineering Contradiction:

Improvetransmission ratio variationVSAvoiddrive train efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

By implementing axial movement of the cassette along the drive member in the third dimension, the system maintains a straight chain line configuration while achieving transmission ratio variation. This eliminates the askew extension of the drive member that causes friction losses, thereby preserving drive train efficiency.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The invention inverts the conventional approach by keeping the drive member straight and stationary, and instead moving the cassette axially to achieve gear changes. This inversion maintains optimal drive member orientation throughout the transmission range, maximizing productivity and minimizing friction-based efficiency losses.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS12497133B2Transmission system for a bicycle

Publication Date: 2025.12.16 CLASSIFIED CYCLING BV

AI summary

A transmission system for a bicycle, wherein the system comprises a driver element configured and arranged to rotate about an axis. The transmission system comprises a cassette of sprockets mounted on the driver element to rotate together. The transmission system comprises a shifting unit arranged to move the cassette of sprockets in axial direction on the driver element. The shifting unit comprises an actuator element arranged to actuate the movement of the cassette of sprockets on the driver element. The actuator element is at least partially positioned between the driver element and the axis, and/or the actuator element is at least partially positioned in axial direction next to the driver element.