Vertical Lift Conveyor Sprocket Offset for Pulsation Cancellation
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Solution Overview
Problem
Vertical lift conveyors experience significant vertical pulsations due to the sinusoidal linear velocity profile of single lift chains, which can lead to resonance and amplified oscillations, especially with varying payloads, making it difficult to design systems that minimize these pulsations effectively.
Innovation Solution
The implementation of a pair of drive sprockets with teeth offset by 180/N° and a pair of lift chains connected through a pivotal connection block to a master chain, which compensates for the sprocket offset, resulting in a constant average velocity profile that cancels out the pulsations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single lift chain is used to convey the carriage, then the structure is simple, but significant vertical pulsations occur due to sinusoidal velocity profile
Solution Approach 1:
The single lift chain system is segmented into multiple lift chains (at least two) that operate in parallel. Each chain is engaged with its own sprocket, and the chains are offset vertically along the drive shaft axis. This segmentation divides the pulsation problem into multiple smaller components that can be phased to cancel each other's vibrations, reducing overall vertical pulsation while maintaining structural feasibility.
Solution Approach 2:
The lift chains are positioned asymmetrically with vertical offsets relative to each other along the drive shaft axis. The sprockets are also offset vertically, creating an asymmetric configuration where the chains engage at different angular positions. This asymmetric arrangement ensures that the sinusoidal velocity profiles of individual chains are phase-shifted, causing their pulsations to cancel rather than reinforce each other.
2Stability of the object's composition
If multiple lift chains are used to reduce pulsations, then vertical stability improves, but device complexity increases
Solution Approach 1:
Multiple lift chains and sprockets are merged into a single integrated drive system that shares a common drive shaft and motor. The sprockets are mounted on the same axial axis, and the chains work together in unison to convey the carriage. This merging approach achieves pulsation reduction through phase cancellation while avoiding the complexity of completely independent drive systems, as the chains and sprockets are synchronized through their shared mounting structure.
3Stability of the object's composition
If sprockets are offset to cancel pulsations, then vertical oscillation reduces, but manufacturing precision requirements increase
Solution Approach 1:
The offset configuration is applied locally to the sprocket and chain arrangement rather than requiring precision throughout the entire conveyor system. The vertical offset between sprockets and chains is the critical localized feature that enables pulsation cancellation. This approach concentrates the precision requirement to a specific geometric relationship (the offset distance and phase angle) rather than demanding high precision across all components, making the system more manufacturable while achieving oscillation reduction.
Data Source
AI summary
A vertical lift conveyor for lifting materials between different vertical levels. The vertical lift conveyor includes a pair of spaced uprights and a carriage that moves vertically along the spaced uprights. The vertical lift conveyor includes a drive assembly including a drive motor coupled to a drive shaft. Each end of the drive shaft includes a first sprocket and a second sprocket that each engages one of a pair of lift chains. The first and second sprockets each include a plurality of teeth (N). The first and second sprockets are offset from each other 180/N°. The offset between the first and sprockets creates sinusoidal velocity profiles for the two chains that are out of phase with each other. A connection block is used to connect the pair of lift chains to each side of the carriage combines the lift chain velocities into a linear vertical velocity for the carriage.