Lobed Sprocket Geometry for Chain Polygon Effect Compensation
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Solution Overview
Problem
Existing passenger conveyor systems, such as escalators and moving walkways, experience vibrations and noise due to the polygon effect caused by the interaction between the step chain and the step chain sprocket, which increases wear and tear, maintenance costs, and noise levels, and existing solutions to mitigate this issue either increase costs or do not effectively address noise.
Innovation Solution
A polygon compensation coupling system that includes a chain sprocket with compensation holes and a main drive engaged through these holes, allowing for rotation with constant average angular velocities but non-constant instantaneous angular velocities to maintain a constant linear speed of the chain, thereby reducing the polygon effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the pitch of the step chain is reduced to minimize the polygon effect, then the polygon effect is reduced, but the number of step chain links and associated parts increases, leading to increased system cost and complexity
Solution Approach 1:
The invention changes the geometric parameters of the sprocket by providing lobes with varying radii of curvature. The first lobe has a different radius of curvature than the second lobe, creating non-uniform engagement characteristics that compensate for the polygon effect without requiring changes to the chain pitch or adding more chain links.
Solution Approach 2:
The invention applies curved surfaces (lobes) with specific radii of curvature to the sprocket engagement surfaces. The varying curvature of the lobes creates a more continuous and smoother engagement path for the chain, reducing the abrupt transitions that cause the polygon effect.
2Object-affected harmful factors
If the diameter of the step chain sprocket is increased to reduce the polygon effect, then the polygon effect is reduced, but the system cost and maintenance requirements increase
Solution Approach 1:
The invention modifies the engagement surface geometry by adding lobes with specific radii of curvature to the existing sprocket design. This allows the polygon effect to be minimized without increasing the overall sprocket diameter, maintaining cost-effectiveness and ease of manufacture.
Solution Approach 2:
The sprocket engagement surface is segmented into multiple lobes (first lobe, second lobe, etc.) with different radii of curvature. This segmentation allows each lobe to be optimized for specific engagement phases, reducing the polygon effect through distributed geometric compensation rather than a single large-diameter design.
3Object-affected harmful factors
If the number of step chain links is increased to reduce the polygon effect, then the polygon effect is reduced, but the wear and tear and lubricant usage increase
Solution Approach 1:
The invention changes the geometric parameters of the sprocket lobes to create a more continuous engagement pattern. This reduces the impact loading and vibration that cause wear, allowing the use of fewer chain links while minimizing the polygon effect and reducing wear and lubricant consumption.
4Object-affected harmful factors
If traditional solutions are used to mitigate the polygon effect, then the polygon effect is reduced, but noise levels may increase due to greater engagement
Solution Approach 1:
The curved lobes with optimized radii of curvature create a smoother engagement transition, reducing impact noise and vibration. The gradual contact between the chain and the lobed surfaces eliminates abrupt engagement shocks that would increase noise levels.
Data Source
AI summary
A polygon compensation coupling system for reducing a polygon effect in a chain driven system is disclosed. The polygon compensation coupling system may include a chain sprocket and a main drive in engagement with the chain sprocket, such that the engagement defines a compensation curve to reduce the polygon effect.