Flower-Shaped Keyed Bicycle Pedal Spindle Connection
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Solution Overview
Problem
Conventional bicycle pedal spindles are prone to breaking due to the direction of thread alignment matching the force exerted by the rider, leading to increased manufacturing costs and complexity in distinguishing left and right spindles.
Innovation Solution
A flower-shaped keyed hole and key connection system replaces traditional threading, enhancing spindle strength and eliminating the need to differentiate between left and right spindles, using a fastener to secure the spindle to the crank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional threaded connection is used between pedal spindle and crank, then the assembly is simple to manufacture, but the spindle is prone to breaking due to thread alignment with force direction
Solution Approach 1:
The connection structure is segmented into two parts: a flower-shaped keyed hole in the crank and corresponding flower-shaped keys on the spindle. This segmentation allows the spindle to have a solid, non-threaded structure while the crank contains the threading, thereby preventing spindle breakage while maintaining manufacturing simplicity.
Solution Approach 2:
The flower-shaped keyed hole and keys provide an asymmetric connection geometry that resists the rotational forces applied to the pedal. The multiple lobes of the flower shape distribute stress more effectively than a simple round hole, enhancing spindle strength without requiring traditional threading on the spindle itself.
2Reliability
If different threading directions are used for left and right spindles to prevent loosening, then loosening is prevented, but assembly complexity and preparation time increase
Solution Approach 1:
The flower-shaped keyed connection serves multiple functions simultaneously: it provides a secure mechanical connection, prevents rotational loosening through the keyed engagement, and works identically for both left and right pedals. This universal design eliminates the need for different threading directions while maintaining anti-loosening capability and simplifying assembly procedures.
3Weight of moving object
If aluminum alloy cranks are used to reduce weight, then weight is reduced, but the crank threads are more susceptible to damage
Solution Approach 1:
The connection structure is segmented into two parts: a flower-shaped keyed hole in the crank and corresponding flower-shaped keys on the spindle. This segmentation allows the spindle to have a solid, non-threaded structure while the crank contains the threading, thereby preventing spindle breakage while maintaining manufacturing simplicity.
4Strength
If a hard bushing is added around the spindle to protect aluminum alloy crank threads, then thread damage is prevented, but manufacturing cost increases
Solution Approach 1:
The connection structure is segmented into two parts: a flower-shaped keyed hole in the crank and corresponding flower-shaped keys on the spindle. This segmentation allows the spindle to have a solid, non-threaded structure while the crank contains the threading, thereby preventing spindle breakage while maintaining manufacturing simplicity.
Data Source
AI summary
The invention includes a crank, a pedal and a fastener. The crank has a flower-shaped keyed hole at an outboard end thereof. The pedal has a body and a spindle with a connecting end. The connecting end is formed with flower-shaped keys corresponding to the flower-shaped keyed hole so that the connecting end is inserted into the flower-shaped keyed hole with engagement between the flower-shaped keyed hole and the flower-shaped keys. An end surface of the connecting end is formed with a first threaded hole. The fastener passes through the flower-shaped keyed hole and screws into the first threaded hole for fixing the connecting end of the spindle to the crank.