Bicycle Sprocket Spacer with Recessed Areas for Chain Meshing
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Solution Overview
Problem
The existing sprocket assemblies for racing bicycles face challenges in achieving correct chain meshing when an additional sprocket with a smaller number of teeth is added, due to the requirement for a spacer with sufficient structural strength, which can result in an outer diameter greater than the sprocket's throat diameter, preventing proper engagement.
Innovation Solution
Incorporating a last spacer with a radially outer surface featuring recessed areas at the throats of the additional sprocket, allowing correct chain meshing even when the spacer's outer diameter exceeds the sprocket's throat diameter, and enabling canti-levered mounting to accommodate conventional freewheel bodies without mechanical processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the last spacer is designed with sufficient structural strength, then the spacer can support the additional sprocket, but the outer diameter of the spacer becomes greater than the throat diameter of the sprocket, preventing correct chain meshing
Solution Approach 1:
The spacer is designed with non-uniform thickness: thicker in regions where structural strength is needed to support the sprocket, and thinner in regions where the chain needs to access the sprocket teeth. This localized variation in geometry allows the spacer to provide both mechanical support and proper chain engagement without requiring the entire spacer outer diameter to be reduced.
2Adaptability or versatility
If an additional sprocket with fewer teeth is added to the sprocket assembly, then a new gear ratio suitable for flat terrain and sprints is achieved, but the spacer required to accommodate this sprocket cannot maintain both structural strength and correct chain meshing
Solution Approach 1:
The spacer is segmented into different functional zones with varying thicknesses. The thicker portions provide structural support for mounting the sprocket, while the thinner portions allow chain access. This segmentation resolves the conflict between needing a strong spacer structure and maintaining correct chain meshing geometry.
Data Source
AI summary
The invention relates to a bicycle sprocket assembly (10), comprising a plurality of sprockets (12) of decreasing diameter configured to be mounted on a freewheel body (20) of a bicycle hub. The plurality of sprockets (12) includes a first sprocket of larger diameter (12a) and a last sprocket of smaller diameter (12d). The last sprocket (14b) comprises a plurality of teeth (122d) and a plurality of throats (121d), each throat (121 d) being arranged between two consecutive teeth (122d). The throats (121 d) comprise respective bottom surfaces (123d) substantially tangent to a first circumference having a first diameter (D1). The sprocket assembly (10) further comprises a plurality of spacers (14) arranged between the first sprocket (12a) and the last sprocket (12d). The plurality of spacers (14) includes a last spacer (14b) arranged between the last sprocket (12d) and a second-last sprocket (12c) of said plurality of sprockets (12) and having a radially inner surface (141 b) configured to be fitted onto a free end portion (23) of said freewheel body (20). The last spacer (14b) comprises a radially outer surface (142b) having a second diameter (D2) greater than said first diameter (D1) and including a plurality of recessed areas (143b), each recessed area (143b) being positioned at a respective throat of said plurality of throats (121 d). The recessed areas (143b) comprise respective base surfaces (144b) substantially tangent to a second circumference having a third diameter (D3) smaller than or equal to said first diameter (D1).