What is a Lever Hoist?
The term lever hoist may be applied to any small, portable lifting device which relies on the manual operation to lift or lower heavy loads. Lever hoists fall into two main categories: cable or rope hoists and chain hoists. Both variants rely on a ratchet and pawl system to rotate a gear or pulley a pre-set distance that lifts the load. The ratchet and lever mechanism is equipped with a hook or fastener which is used to suspend the lever hoist from a suitable support. Both lever hoist types may be used in any orientation for lifting, tensioning, or pulling operations although chain type hoists are generally more suited to vertical lifting.
Both kinds of lever hoists makes use of the mechanical advantage of a lever to lift loads which would be impossible to move by hand. The rope hoist, or “come-A-long” as it is colloquially known, employs a steel rope wound onto a pulley which incorporates an inbuilt ratchet system and a mounting hook. The other end of the rope is fitted with a small hook block used to attach the load.
Once the rope hoist has been securely attached to a suitable support using the mounting hook, the ratchet is unlocked and the rope pulled down to the load. The load is then attached to the hook block and the pawl re-engaged. The load may then be lifted by cranking the handle up and down. Typically the downward cycle of this cranking motion will turn the pulley and retrieve a length of rope in turn raising the load. The upward stroke usually does not turn the pulley and only serves to bring the handle back to the top of its travel to perform another cycle.
The chain-operated lever hoist works in a similar fashion except there is no pulley system. Instead, it employs a gear over which a free falling length of chain travels. The operating lever of the chain hoist is also fitted with a pawl system and may employ additional gears which increase the speed and power of the hoist. Each time the handle is cycled, it turns the gear which advances or retrieves the chain to raise or lower the load. The chain hoist handle mechanism is fitted with a release feature which means that, as in the case of the rope hoist, the work is achieved on one half of the stroke cycle.
The benefit of using a rope hoist is the fact that there is no free falling length of chain which makes it ideal for horizontal pulling operations. Although the chain hoist may be also used in these applications, the excess chain on the non-load side is impractical, making it better suited to vertical lifting operations. One safety consideration that should be kept in mind at all times when using either lever hoist is never to exceed the rating of the hoist. The lever hoist can be particularly susceptible to overload failures with the rope hoist being especially dangerous due to the possibility of whip injuries should the rope break.
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