Bicycle Cogset Monolithic Sprocket Coupling for Small Tooth Counts
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Solution Overview
Problem
Modern bicycle gearshifts with a high number of sprockets face challenges in mounting small sprockets with low teeth due to size constraints, leading to reduced flexibility in gear ratio selection and compromised coupling solidity.
Innovation Solution
A cogset design featuring monolithic sets of sprockets with a coupling profile on the radially inner surface of the largest sprocket, allowing direct shape engagement with the sprocket-carrying body and optional ring nut for stable positioning, enabling flexible tooth selection and high coupling solidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of sprockets is increased to provide more gear ratios, then the versatility of the gearshift system is improved, but the size constraints on small sprockets worsen, making mounting difficult
Solution Approach 1:
The patent combines multiple small sprockets (typically 3-5 sprockets with 9-12 teeth each) into a single monolithic set that is mounted as one unit on the sprocket-carrying body. This merging allows each individual sprocket to have a small diameter suitable for low tooth counts, while the collective assembly provides the necessary mounting surface area and structural integrity. The monolithic design enables the inclusion of sprockets with very low tooth counts (9 teeth or fewer) that would be too small to mount individually, thus expanding gear ratio versatility without compromising manufacturability.
2Adaptability or versatility
If small sprockets with fewer teeth are used to increase gear ratio flexibility, then the adaptability of the cogset is improved, but the coupling solidity between sprockets and sprocket-carrying body worsens
Solution Approach 1:
The monolithic set merges multiple small sprockets into a single rigid structure, where the strength of the coupling between the sprocket group and the sprocket-carrying body is distributed across multiple engagement points. The coupling profile engages with multiple teeth from different sprockets simultaneously, creating a cumulative coupling strength that compensates for the small size of individual sprockets. This approach maintains high coupling solidity while allowing flexible tooth selection across the range of sprockets in the set.
Solution Approach 2:
The patent transitions from individual sprocket mounting to a multi-dimensional coupling approach, where the coupling profile engages with multiple sprockets across different radial positions and axial depths. This multi-point engagement in three-dimensional space distributes the mechanical loads and enhances overall coupling solidity, allowing small sprockets to be mounted securely without relying on the strength of a single sprocket-coupling interface.
3Ease of manufacture
If monolithic sets of small sprockets are used, then the manufacturing flexibility is improved, but the device complexity increases due to the need for specialized coupling profiles
Solution Approach 1:
The coupling profile is designed with multi-functionality to engage with various configurations of monolithic sets. The same basic coupling profile geometry can accommodate different numbers of sprockets (3-5 sprockets), different tooth counts (9-12 teeth), and different radial positions. This universal design reduces the need for specialized coupling profiles for each specific sprocket configuration, thereby reducing device complexity while maintaining manufacturing flexibility. The coupling profile essentially serves multiple functions: providing mechanical engagement, distributing loads, and accommodating variations in sprocket arrangement.
Data Source
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Figure 3
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AI summary
The cogset (20) has the first n sprockets (26a, 26b, 26c), with 6 ≥ n ≥ 3, fixedly connected to one another so as to form a monolithic set (26), adapted for being mounted directly in shape engagement on a coupling profile (16) formed on the radially peripheral surface of a sprocket-carrying body (14) through a coupling profile (32) formed on the radially inner surface of at least the largest sprocket (26a) of the monolithic set (26). The direct shape coupling between the largest sprocket (26a) of the monolithic set (26) and the sprocket-carrying body (14), and the fact that this direct coupling is made between the radially peripheral surface of the sprocket-carrying body (14) and the radially inner surface of the largest sprocket (26a) (or of the largest sprockets) of the monolithic set (26), makes it possible to have very high solidity and rigidity of coupling, so as to ensure the maximum precision of actuation of the gearshift that uses the subassembly.