Chain hoist
A chain is a lifting gear , in which as the support means of round steel chains may be used. It is used to raise and lower freely movable loads. The lifting movement can be generated by manual operation, compressed air or an electric motor .
Areas of application
Chain hoists are used both as hoists on crane systems or rail systems in the area of overhead conveyor technology, as well as aids in assembly work. Chain hoists are also manufactured in explosion-proof design. In comparison to the rope hoist, the chain hoist is usually cheaper and is used in the lower load ranges (up to max. 10 t). Further advantages result from the compact dimensions and the low weight. In contrast to the rope pull , there is no hook migration. Lifting speeds of ≥ 32 m / min and lifting heights of 160 m (when used in wind turbines) have already been achieved.
General structure of a motorized chain hoist
The chain hoist essentially consists of the following components:
Lifting motor, gear , chain guide, chain sprocket , hook block, round steel chain and chain box .
The necessary speed reduction to the output shaft is achieved from the lifting motor via the gearbox . The lifting movement can be generated either with pole-changing or frequency-controlled motors. Pole-changing motors allow a slow (fine stroke) and a fast (main stroke) lifting speed. When operating with frequency converters, the operator can continuously regulate the lifting speed. The motor can either be switched directly or switched on and off via a contactor-transformer combination. In the case of direct control, mains voltage and current are applied to the control device, while contactor controls are supplied with a safety extra-low voltage. The chain sprocket on the output shaft enables a positive connection to the round steel chain . A hook block is attached to the chain from which loads can be attached. The chain box , usually made of sheet metal or plastic , is used to protect and store the chain.
Polygon effect
A polygon effect occurs with every chain hoist . It describes a rhythmic oscillation of the chain hoist when pulling in the chain, which is caused by the different effective radii of the chain on the pulling roller. In the extreme case, the chain swings up to the resonance frequency .
conditions
In event technology, a distinction is made between different types of chain hoists. Depending on the intended use, the trains must meet different safety requirements. Various safety devices are built into the trains, such as slip clutches , safety brakes, emergency limit switches, overload monitoring, etc. The main issue here is how the train reacts in the event of a fault.
A distinction is made between three different types, which are described in the SQP2 standard of the igvw and the professional association regulations (BGV):
BGV D 8-Zug: chain hoist for assembly and dismantling to lift loads, to hold loads above people, a secondary safety device must be attached that does not allow a fall
igvw D 8 Plus-Zug: chain hoist for assembly and dismantling to lift loads, when idle the train is suitable for holding loads above people without secondary safety
BGV C 1-Zug: chain hoist for holding and moving loads above people
Occupational safety
Like all other hoists, chain hoists are obliged to carry out a recurring inspection.
literature
- Martin Scheffler, Klaus Feyrer, Karl Matthias: conveyors. Hoists, elevators, industrial trucks. Vieweg, Braunschweig et al. 1998, ISBN 3-528-06626-1 .
- SQP2 standards for electric chain hoists in March 2010 from the Event Industry Interest Group, formerly SR2.0 from VPLT
Web links
Individual evidence
- ↑ Screw pulley system from Eduard Becker (engineer)
- ↑ SQP2. Retrieved May 10, 2020 . , >> igvw standards of quality, electric chain hoists (PDF, 1.2MB)