Two-Part Ring Nut Assembly for Small-Sprocket Bicycle Cogsets
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Solution Overview
Problem
The challenge is to securely fix a monolithic cogset with small sprockets to a bicycle rear wheel sprocket-carrying body without increasing the weight of the sub-assembly, as the small diameter of the smallest sprocket's central opening prevents conventional ring nuts from engaging effectively.
Innovation Solution
A two-part ring nut design, where the first part has a radially peripheral flange and the second part has a radially peripheral threaded portion, allowing the nut to be constrained axially to the monolithic set without needing to be inserted through its central opening, enabling secure screwing to the sprocket-carrying body while allowing the set to rotate freely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ring nut is used to fix the monolithic set to the sprocket-carrying body, then the assembly is secure, but the weight of the sub-assembly increases
Solution Approach 1:
The ring nut is divided into two separate parts: a first part with a radially peripheral flange for axial constraint, and a second part with a radially peripheral threaded portion for screwing to the sprocket-carrying body. This segmentation allows each part to be optimized for its specific function, reducing the overall weight compared to a single conventional ring nut while maintaining secure fixation.
2Adaptability or versatility
If the smallest sprocket has a reduced number of teeth to achieve smaller diameter, then the gear ratios are maintained, but the central opening becomes too small for conventional ring nuts to engage
Solution Approach 1:
By segmenting the ring nut into two parts, the first part can be positioned to engage with the flange on the outer periphery of the monolithic set, away from the central opening. This allows the smallest sprocket to have a reduced number of teeth and smaller diameter while still providing adequate space for the ring nut components to engage properly.
3Ease of manufacture
If the ring nut is inserted through the central opening of the monolithic set, then the assembly is simple, but small sprockets cannot accommodate the ring nut
Solution Approach 1:
Instead of inserting the ring nut through the central opening in the axial direction, the first part of the ring nut engages with the flange on the outer periphery of the monolithic set. This dimensional change from central engagement to peripheral engagement allows small sprockets with limited central opening diameter to accommodate the ring nut assembly while maintaining simple assembly procedures.
Data Source
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AI summary
The sub-assembly provides for a ring nut (30) formed in two parts (31, 32) assembled together - an axially outer first part (31) on which a tubular body (33) and a flange (35) are formed, and an axially inner second part (32) on which a threaded portion (36) is formed. The structure in two parts allows a simple and effective coupling of the ring nut (30) with a monolithic set (26) of a cogset and the attachment thereof to a sprocket-carrying body provided with internal threading. The two parts (31, 32) of the ring nut (30) can be partially inserted in the monolithic set (26) from opposite directions and thus be coupled by closing together the monolithic set (26).