Lever hoists are portable lifting devices that use manual operation to lift heavy loads. They come in two main categories: rope/wire rope hoists and chain hoists. Both types use a ratchet and pawl system to lift loads, and can be used for lifting, tensioning, or pulling operations. Wire rope hoists are ideal for horizontal pulling operations, while chain hoists are better suited for vertical lifting. It is important to never exceed the rated power of the hoist to prevent overload failure and injury.
The term lever hoist can be applied to any small portable lifting device that relies on manual operation to raise or lower heavy loads. Lever hoists fall into two main categories: rope or wire rope hoists and chain hoists. Both variations rely on a ratchet and pawl system to rotate a gear or pulley a pre-set distance which lifts the load. The ratchet and lever mechanism is equipped with a hook or fastener which serves to suspend the lever block from a suitable support. Both types of lever hoists can be used in any orientation for lifting, tensioning or pulling operations, although chain hoists are generally more suited to vertical lifting.
Both types of lever hoists use the mechanical advantage of a lever to lift loads that would be impossible to move by hand. The wire rope hoist, or “come-A-long” as it is commonly known, employs a steel wire rope wound over a sheave that incorporates an integrated ratchet system and mounting hook. The other end of the rope has a small block used to secure the load.
Once the wire rope hoist has been securely attached to a suitable support using the mounting hook, the ratchet is released and the wire rope pulled down onto the load. The load is then secured to the block and the pawl re-engaged. The load can then be lifted by raising and lowering the handle. Typically the downward cycle of this cranking motion will spin the sheave and retrieve a piece of rope in turn lifting the load. The up stroke does not usually turn the pulley and only serves to return the handle to its maximum stroke to perform another cycle.
The chain lever hoist works similarly except there is no pulley system. Instead, it employs a gear on which a free-falling section of chain travels. The chain hoist operating lever is also equipped with a pawl system and can employ additional gears which increase the speed and power of the hoist. Each time the handle is operated, it spins the gear which advances or retrieves the chain to raise or lower the load. The handle mechanism of the chain hoist is equipped with a release device which causes, as in the case of the wire rope hoist, the work to be done on half of the stroke cycle.
The benefit of using a wire rope hoist is the fact that there is no free falling section of chain making it ideal for horizontal pulling operations. Although the chain hoist can also be used in these applications, the excess chain on the empty side is impractical, making it more suitable for vertical lifting operations. One safety consideration that should always be kept in mind when using either lever hoist is to never exceed the rated power of the hoist. The lever hoist can be especially susceptible to overload failure, and the wire rope hoist is especially dangerous due to the possibility of whiplash injury if the rope breaks.
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