Cycle Crankset with Self-Positioning Floating Chainring

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Solution Overview

Problem

The symmetrical configuration of cranks in traditional cranksets leads to ineffective pedaling due to dead spots, requiring unstable shifts and chain lengthening, which increases the weight and complexity of the cycle.

Innovation Solution

Independent cranks with a cam-mounted plate, where the articulation axis is opposite the pedal axis, allowing the cam to naturally offset rearward and self-position to avoid dead spots, reducing chain length and weight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the articulation axis is positioned forward of the crank axis to eliminate dead centers, then dead spots are eliminated, but the cam becomes unstable and requires additional positioning systems

Engineering Contradiction:

Improvepedaling efficiencyVSAvoidcam position stability

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent inverts the conventional cam positioning approach by placing the articulation axis rearward of the crank axis instead of forward. This inversion allows the chain tension to naturally push the cam rearward into a stable position, eliminating the need for additional positioning systems while avoiding dead spots through the reversed geometry

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of operation

If the chain is lengthened to accommodate forward cam offset, then the cam can be positioned to eliminate dead centers, but the cycle weight increases

Engineering Contradiction:

Improvedead center eliminationVSAvoidcycle weight

Core Design Contradiction:

Ease of operationVSWeight of moving object

Solution Approach 1:

By inverting the cam offset direction to rearward instead of forward, the patent reduces the required chain length. The chain naturally pushes the cam rearward under tension, achieving dead center elimination with a shorter chain configuration that reduces overall cycle weight

Inventive Principle:

Principle #13The other way round (Inversion)

3Stability of the object's composition

If additional systems are added to maintain cam position, then cam stability is improved, but device complexity increases

Engineering Contradiction:

Improvecam position stabilityVSAvoidpositioning system complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent implements a self-service mechanism where the chain tension automatically pushes the cam into its stable rearward position during normal operation. This self-positioning eliminates the need for external positioning systems, maintaining cam stability while minimizing device complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The inverted rearward offset configuration allows chain tension to naturally stabilize the cam position, converting what would require active positioning systems into a passive self-stabilizing arrangement

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP3439946B1Cycle crankset with self-positioned floating chainring

Publication Date: 2024.03.27 C3B

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AI summary

The invention relates to a cycle crankset, comprising independent cranks (11) articulated around a crank axis (x) and each having a pedal axis (w), a cam (1) pivotably mounted about said crank axis, and a chainring assembly pivotably mounted about the cam (1), about an axis parallel to the crank axis, the cranks (11, 12) being connected to the chainring assembly via connecting rods (5, 6), the articulation point (n) between each of said cranks (11, 12) and one of said connecting rods being located on the portion of the crank opposite the pedal axis (w, t) relative to the crank axis (x). The crankset according to the invention is intended for being fitted on cycles in order to improve the performance thereof.