Alternating Pitch Circle Chain Drive Eliminates Polygon Effect
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Solution Overview
Problem
Conventional driving and reversing elements for chains in transport systems, such as escalators and conveyors, experience the polygon effect, leading to speed fluctuations, noise, and premature wear due to sudden rotational impulses and sliding of chain rollers on engagement elements.
Innovation Solution
The use of engagement elements with alternating first and second pitch circles, where chain pins alternately engage on different diameter circles, preventing sliding and maintaining constant velocity, thereby reducing the polygon effect and associated noise and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional engagement element with a single pitch circle is used, then the chain is driven, but the polygon effect causes speed fluctuations, noise, and wear
Solution Approach 1:
The single pitch circle is segmented into multiple pitch circles (first pitch circle with radius R1 and second pitch circle with radius R2). Chain pins are distributed across these multiple circles, causing them to engage alternately. This segmentation eliminates the polygon effect by ensuring that as some pins engage on one pitch circle, others engage on another, averaging out the speed fluctuations and maintaining constant chain velocity.
Solution Approach 2:
The engagement element is designed to rotate such that chain pins periodically engage with alternating pitch circles in a regular sequence. This periodic engagement pattern ensures that the polygon effect is counterbalanced, as pins engage on larger and smaller radius circles in alternation, maintaining constant velocity in the direction of chain movement while allowing controlled radial motion.
2Speed
If chain rollers slide on the engagement element to compensate for polygon effect, then speed fluctuation is reduced, but noise and wear increase
Solution Approach 1:
By segmenting the engagement element into multiple pitch circles with different radii, the patent eliminates the need for sliding compensation. Chain pins engage positively on alternating circles, maintaining constant velocity without requiring rollers to slide across the engagement element surface, thereby preventing the noise and wear associated with sliding friction.
3Speed
If the pitch circle radius is increased to reduce polygon effect, then velocity constancy improves, but the engagement element size and complexity increase
Solution Approach 1:
Rather than using a single large pitch circle, the patent segments the engagement element into multiple smaller pitch circles with different radii. This segmentation achieves velocity constancy through the alternating engagement pattern, avoiding the need for a single large radius that would increase the overall size and complexity of the engagement element.
Data Source
AI summary
A driving and/or reversing system includes a driving and/or reversing element and a chain having a plurality of first and second chain pins connected by chain plates. The driving and/or reversing element has first and second pitch circles. First and second chain pins are alternately correspondingly engaged with the first and second pitch circles.