Sectioned Step Pulley for Clutchless Continuous Gear Shifting
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Solution Overview
Problem
Current gear shifting mechanisms for bicycles and lightweight vehicles require a secondary transmission system with a clutch, leading to power loss and mechanical inefficiencies, as they must disconnect the motor from the load during shifting, and existing pulley systems with integrated gear shifting face alignment and wear issues.
Innovation Solution
A sectioned pulley transmission system where pulley sections quickly rotate on a hub during a shift window to align surfaces of different diameters with the flexible drive member, maintaining synchronous motion and eliminating the need for a clutch, using a modular flexible drive member and a variable force tensioner to ensure constant engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a secondary transmission system with clutch is used for gear shifting, then gear changing capability is achieved, but power loss occurs and mechanical efficiency deteriorates
Solution Approach 1:
The patent merges the gear shifting function directly into the drive pulley by creating a sectioned pulley where multiple pulley sections can be rotated to different positions. This integration eliminates the need for a separate clutch mechanism, allowing gear changes to occur while maintaining continuous power transmission from the drive member to the driven member.
Solution Approach 2:
The patent employs dynamic reconfiguration of the drive pulley by allowing pulley sections to rotate to different angular positions. During shifting, one or more pulley sections rotate to a shifted position where they engage the drive member at a different radial distance, effectively changing the gear ratio without disconnecting the power transmission path.
2Adaptability or versatility
If the drive member is disconnected from the pulley during shifting, then gear ratio change is enabled, but power transmission is interrupted
Solution Approach 1:
The drive pulley is segmented into multiple independently rotatable pulley sections. Each section can be rotated to a different angular position to engage the drive member at different radial distances. This segmentation allows one section to be shifted while other sections continue to transmit power, ensuring continuous power transmission during gear changes.
Solution Approach 2:
The patent ensures continuous power transmission by maintaining engagement between the drive member and at least one active pulley section throughout the shifting process. While one pulley section rotates to a new position, other sections remain in their original positions and continue to transmit power, eliminating interruptions in the useful action of power transmission.
3Adaptability or versatility
If the drive member flexes laterally to climb onto a different sized pulley, then gear shifting is achieved, but alignment issues and wear increase
Solution Approach 1:
Instead of lateral movement, the patent employs rotational movement of pulley sections about the pulley axis. Each pulley section rotates to a different angular position, bringing surfaces of different diameters into alignment with the drive member. This rotational approach maintains consistent alignment between the drive member and the active pulley surface, preventing misalignment and reducing wear.
Data Source
AI summary
A pulley for a transmission system, including a central rotatable hub having a circumference; and a plurality of adjoining identical pulley segments rotatably mounted about the central hub circumference, wherein the adjoining pulley segments form an approximately circular stepped pulley shape and each of the pulley segments includes two sections providing two curved shelf surfaces for engaging a flexible drive member, each shelf having a different radius, forming higher and lower steps, and further wherein each of the pulley segments are independently rotatable about a radial axis with respect to the central hub.