Two-Piece Rear Sprocket Assembly With Latching Load Distribution
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Solution Overview
Problem
The existing bicycle rear wheel sprocket assemblies experience mechanical stress and potential damage due to large differences in sprocket sizes, leading to stress peaks and cracking, particularly at the fastening surfaces where oversized pins are used for attachment, causing axial deformation and form-fitting effects that are not sufficient to handle operational forces effectively.
Innovation Solution
The introduction of elastically deformable latching formations on the subassemblies that secure the two subassemblies together through a form-fitting engagement, eliminating the need for separate fasteners and enhancing component strength by distributing forces more evenly, while maintaining assembly simplicity and reducing assembly effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If oversized pins are used for attachment at fastening surfaces, then the connection between subassemblies is secured, but stress peaks and cracking occur due to insufficient distribution of operational forces
Solution Approach 1:
The pinion assembly is divided into two separate subassemblies (first subassembly with largest pinion, second subassembly with remaining pinions) that are connected through interlocking formations rather than traditional fasteners. This segmentation allows forces to be distributed across multiple engagement points (locking formations and counter-formations) rather than concentrating stress at single fastening holes, thereby preventing cracking while maintaining connection strength.
Solution Approach 2:
The connection interface features localized interlocking formations with specific geometric shapes designed to distribute loads evenly across the engagement surfaces. The locking formations include features such as protrusions, recesses, and bearing surfaces that are strategically positioned to handle different force components (axial, radial, tangential), creating locally optimized stress distribution zones that prevent stress peaks.
2Ease of manufacture
If traditional fastening pins are used, then assembly is simplified, but mechanical strength is reduced due to weakening of fastening surfaces
Solution Approach 1:
The fastening function and the structural connection function are merged into a single integrated interlocking mechanism. The locking formations are formed as integral parts of the subassemblies themselves, eliminating the need for separate fasteners. This merging maintains assembly simplicity while significantly improving strength by distributing loads across the interlocking geometry rather than relying on weakened fastening holes.
Solution Approach 2:
The traditional fastening holes and separate fastener components are extracted from the design. Instead of creating holes that weaken the fastening surfaces, the connection is achieved through protruding locking formations that engage with corresponding counter-formations, removing the source of stress concentration while maintaining ease of assembly through the inherent geometry of the interlocking features.
3Strength
If separate fastening components are used, then connection is achieved, but device complexity increases and assembly effort increases
Solution Approach 1:
The subassemblies are designed with self-locking interlocking formations that automatically engage and secure the connection during the assembly process. The locking formations are shaped such that when the subassemblies are brought together, the features naturally mate and lock without requiring additional fastening operations, tools, or complex sequencing, thereby reducing both device complexity and assembly effort while maintaining strong connections.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly increases the mechanical strength and stability of the pinion arrangement, preventing relative movement between subassemblies and ensuring a secure, practically unreleasable latching engagement that enhances operational reliability and reduces the risk of damage from operational forces.
Implementation Method 1
at least one of the first and second sub-assemblies has elastically deformable latching formations which are in latching engagement with latching counter-formations of the other sub-assemblies
Data Source
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AI summary
A bicycle rear wheel sprocket assembly (30), rotatable about a common sprocket rotation axis (RA) defining an axial direction and radial directions orthogonal thereto, comprises a plurality of sprockets (R1-R12) of different sizes and numbers of teeth arranged coaxially with respect to the sprocket rotation axis (RA) and connected to one another for common rotation about the sprocket rotation axis (RA). The sprocket assembly (30) has a first sub-assembly (32) comprising the largest sprocket (R1), and a second sub-assembly (34) comprising a plurality of sprockets (R3-R12) formed integrally together. According to the invention, the second sub-assembly (34) has a series of between 6 and 12 axially successive sprockets (R3-R12) formed integrally together.