Bicycle Cassette Sprocket Segmentation for Weight Reduction
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Solution Overview
Problem
Current bicycle cassette designs are heavy and costly due to the need for stiff sprockets with thick radial dimensions to transmit tangential forces efficiently, which also results in increased weight and complexity, while existing solutions either require replacing the entire cassette or result in complex manufacturing processes.
Innovation Solution
A cassette design featuring sprockets with a smaller base diameter and a spacer that extends from the grooved surface of the larger sprocket to the base line of the smaller sprocket, allowing tangential forces to be transmitted directly to the supporting structure, enabling axial forces to be transmitted between sprockets via spacers, thus allowing for easier disassembly and replacement of sprockets without damaging the supporting structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If sprockets are made with thick radial dimensions to transmit tangential forces efficiently, then force transmission is improved, but weight increases
Solution Approach 1:
The invention divides the cassette into two separable parts: a non-consumable supporting structure (body) and consumable sprockets. The supporting structure contains the grooved geometry for force transmission, while sprockets can be replaced independently. This segmentation allows the force transmission function to be preserved in the durable body while enabling lightweight, replaceable sprockets.
Solution Approach 2:
The grooved geometry acts as an intermediary between the sprocket and the supporting structure. The groove transmits tangential forces from the sprocket teeth to the body, allowing efficient force transmission without requiring the sprocket itself to have thick radial dimensions. The groove serves as the mediator that handles the force transmission function.
2Strength
If sprockets are made with thick radial dimensions to ensure stiffness, then strength is improved, but manufacturing complexity increases
Solution Approach 1:
By separating the stiff supporting structure with grooved geometry from the sprockets, the invention allows each component to be optimized independently. The body can be manufactured with complex grooved features for stiffness and force transmission, while sprockets can be simpler, lighter components that are easier to manufacture and replace.
Solution Approach 2:
The invention treats sprockets as disposable consumable parts that can be easily replaced, while the expensive, complex supporting structure is kept permanently. This allows sprockets to be manufactured simply and economically, while the strength and stiffness functions are concentrated in the durable, non-consumable body.
3Reliability
If the entire cassette is replaced due to sprocket wear, then reliability is maintained, but cost increases
Solution Approach 1:
The cassette is segmented into consumable sprockets and non-consumable supporting structure. When sprockets wear, only the sprockets need to be replaced, not the entire cassette. This preserves the reliable, durable supporting structure while replacing only the worn components, reducing material waste and cost.
Solution Approach 2:
The invention enables discarding only the worn sprockets while recovering and reusing the supporting structure. The grooved geometry and other permanent features of the body are preserved, and only the consumable sprockets are discarded and replaced, significantly reducing material loss compared to replacing the entire cassette.
4Force
If spacers are positioned to transmit axial forces, then axial force transmission is improved, but tangential force transmission distance increases
Solution Approach 1:
The invention applies different functional qualities to different parts of the supporting structure. The grooved geometry is positioned and shaped specifically for optimal tangential force transmission, while spacers are positioned specifically for axial force transmission. Each feature has its optimized location and function, avoiding compromise between conflicting requirements.
Data Source
AI summary
Cassette (1) for a bicycle transmission system, which comprises a first sprocket (P1) and a second sprocket (P2) smaller than the first sprocket (P1) and a support structure (S) the sprockets (P1, P2), being the inner edges (CI1, CI2) of the sprockets (P1, P2) configured by grooved surfaces (P11, P21), being the support structure (S) provided with two engagement surfaces (S1, S2) complementary of the grooved surfaces (P11, P21) of the grooved sprockets (P1, P2), such that tangential forces (T) can be transmitted between the sprockets and the support structure (S), comprising the cassette at least a spacer (E1-2, E2-3, E3-4 . . . ) between sprockets (P1, P2), wherein the base line (B2) of the second sprocket (P2) is smaller than the average diameter (D1) of the grooved surface (P11) of the first sprocket (P1), extending the spacer (E1-2) between the first sprocket (P1) and the second sprocket (P2) at least from the grooved surface (P11) of the first sprocket (P1) to at least the base line (B2) of the second sprocket (P2), such that the spacer (E1-2) allows to exert axial forces (A) on the first sprocket (P1).