Double Chainring Axial Protrusions for Smaller Gears
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Solution Overview
Problem
Standard bicycle crank spiders limit the size of small chainrings, restricting cyclists to larger chainrings that provide only higher gears, making it difficult to ascend steep hills or navigate challenging terrain.
Innovation Solution
Incorporating axial protrusions on the small chainring and recesses on the large chainring allows for axial movement relative to the crank spider, enabling the use of smaller chainrings without interference with the spider, thus allowing for tighter connection and proper power transfer while using standard gear equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a smaller chainring is used to provide lower gears for steep ascents, then the cyclist can ascend hills more easily, but the chainring cannot be tightly connected to the standard crank spider
Solution Approach 1:
The invention introduces axial positioning elements (protrusions on the small chainring and recesses on the large chainring) that engage with the crank spider in the axial dimension, allowing the chainrings to be tightly connected radially even when the small chainring diameter is reduced. This dimensional approach resolves the contradiction by providing connection reliability through axial engagement while maintaining the benefits of a smaller chainring diameter for lower gears.
2Ease of operation
If the outer perimeter of the chainring is located well outside the outer radius of the crank spider to allow chain operation, then the chain can run freely, but the chainring diameter cannot be reduced
Solution Approach 1:
The invention uses axial protrusions and recesses to position the chainrings at an optimized radial distance from the crank spider center. This axial positioning mechanism allows the chainring outer perimeter to be located at the precise distance needed for proper chain operation, rather than requiring a fixed large diameter. The axial elements enable the chainring diameter to be reduced while maintaining the necessary outer perimeter position for free chain operation.
3Reliability
If axial protrusions and recesses are added to enable axial movement and tighter connection, then smaller chainrings can be used with proper power transfer, but the device complexity increases
Solution Approach 1:
The invention combines the axial positioning and connection functions into integrated protrusions and recesses that are part of the chainring and crank spider structures. Rather than adding separate adjustment mechanisms or complex positioning systems, the axial elements are merged into the existing chainring and spider designs, providing reliable power transfer through axial engagement while minimizing the increase in device complexity.
Data Source
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AI summary
The present invention pertains to a double chainring (1) suitable for engagement to a bicycle crank spider (4), the double chainring (1) comprising: a small chainring (2) having first mounting openings (7); and a large chainring (3) having second mounting openings (8), wherein the first mounting openings (7) and the second mounting openings (7) are suitable for engagement with respective third mounting openings (6) provided on respective mounts (5) of the spider (4) so as to assemble the small chainring (2) and the large chainring (3) to the spider (4); wherein each chainring (2, 3) has a side facing the spider (4) and a side facing away from the spider (4), in an assembled state; wherein the small chainring (2) has axial protrusions (11) at the side facing the spider (4) suitable for engaging axially against the spider (4) in the assembled state; and wherein the large chainring (3) has axial recesses (15) at the side facing the spider (4) suitable for axially receiving the respective mounts (5) in the assembled state. The present invention also pertains to a method for assembling the above double chainring (1).