Double Chain Wheel Offset to Reduce Chain Hoist Polygon Effect
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Solution Overview
Problem
Chain hoists with link chains experience the polygon effect, characterized by rhythmic swinging of the load chain due to varying effective radii on the tension roller, which can lead to extreme vibrations approaching resonance frequency.
Innovation Solution
A chain drive system with two chain wheels twisted at a fixed angular offset greater than 0°, preferably half the angular pitch, to compensate for temporarily different radial deflections of the chain strands, reducing the polygon effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single chain wheel is used in a chain hoist, then the structure is simple, but the polygon effect causes rhythmic swinging and vibrations of the load chain
Solution Approach 1:
The patent combines multiple chain wheels (at least two) into a single integrated chain drive system, where multiple chains are guided over multiple chain wheels that are arranged adjacent to one another on a common shaft. This merging of multiple chain wheels into one functional unit allows the chains to work together to reduce the polygon effect while maintaining a relatively compact and simple overall structure.
Solution Approach 2:
The patent segments the single chain wheel function into multiple chain wheels, each guiding a respective section of a link chain. By dividing the load support function across multiple chain wheels with different angular positions, the system compensates for the polygon effect through the combined action of multiple chains, thereby improving load stability.
2Stability of the object's composition
If multiple chain wheels are used to reduce the polygon effect, then load stability improves, but the device complexity increases
Solution Approach 1:
Multiple chain wheels are merged into a single functional assembly mounted on a common shaft, sharing a common drive mechanism. This integration reduces the overall complexity compared to using separate chain wheels with independent drives, while still achieving the load stability benefits of multiple chains working together.
Solution Approach 2:
The multiple chain wheels perform the same function of guiding chains, but their combined operation achieves additional benefits of reducing the polygon effect. This multi-functionality allows a single chain drive system to simultaneously provide load support and vibration reduction without requiring additional separate mechanisms.
3Stability of the object's composition
If chain wheels are arranged with angular offset, then radial deflections are compensated and polygon effect is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies particular angular offset parameters (such as at least 5 degrees, or specific fractions of the angular pitch between chain links) to optimize the compensation of radial deflections. By defining specific parameter ranges, the system achieves effective polygon effect reduction while providing clear manufacturing guidelines to manage precision requirements.
Data Source
AI summary
A chain drive for chain hoist with two link chains including two chain wheels arranged adjacent on a shaft and in torque-proof connection to one another, each chain wheel being used to guide a section of link chain having alternately horizontal and vertical links, namely, with pockets for accommodating horizontal links and with a groove extending in the circumferential direction for accommodating vertical links. The chain wheels have a fixed angular offset smaller than the angular pitch between two successive chain links of a chain wheel. This chain drive forms a chain drive system together with a sling for two link chains running parallel, wherein the sling includes, at one end, a connecting part for a load and, opposite thereto, two adjacently arranged connection portions for respective end links of either link chain, wherein the connection portions are offset from one another along the load direction with a linear offset smaller than the chain pitch along the load direction.