Hoist

3 Ton Shop Hoist

See also:  Winch

A hoist is a piece of materials handling equipment used to lift, lower, and hold heavy loads.^[1] A hoist uses a series of pulleys and gears to gain mechanical advantage, which allows a large load to be lifted with little effort.^[2] Hoists are often used in conjunction with cranes, monorails, and derricks to allow for horizontal movement.^[3]

[edit] Features/Types/How it Works

Hoists are loosely classified as either frictional hoists or drum hoists.  A frictional hoist’s rope passes over a pulley and is propelled by friction between the rope and pulley. A drum hoist's rope is physically attached to a rotating drum and subsequently wound as the drum rotates. ^[4]

Hoists are classified further according to the type of power used; most commonly mechanical, electric, or pneumatic.^[5]

[edit] Frictional Hoists

[edit] Mechanical hoist

Mechanical hoists use human power to lift. There are two main types of mechanical hoists, chain hoists and lever-operated hoists.^[6] In a chain hoist, the operator pulls lightly on a thin chain. In a lever operated hoist, the operator has to pull repeatedly on a ratcheting lever. Either way, the operator’s force is magnified by a series of gears and pulleys, making it possible for an individual to lift very heavy objects.

[edit] Electric hoist

Electric hoists are the most popular type of hoist.^[7] They lift quickly in a controlled manner. An electric hoist works in the same fashion as a mechanical hoist, except power is generated from an electric motor before being magnified by the gear assembly. Electric hoists use wire rope, welded steel chain, or roller load chain.

[edit] Pneumatic hoist

Pneumatic hoists, or air-powered hoists, are used as alternatives to electric hoists in hazardous environments where electricity may pose a safety risk.^[8] Pneumatic hoists have either a rotary-vane^[9] pneumatic engine or a piston pneumatic engine^[10] to turn compressed air into a usable force. Like electric hoists, they are available with wire rope, welded steel chain, or roller load chain.

[edit] Drum Hoists

Like frictional hoists, drum hoists can be powered mechanically, electrically, or pneumatically. Drum hoists come as either single drum or double drum machines.

[edit] Single drum hoist

In a single drum hoist, a rope is attached to a drum and wound. The surface of the drum is grooved to allow the rope to wind uniformly.^[11] For most applications, single drum hoists are more efficient than double drum hoists. ^[12]

[edit] Double drum hoist

In a double drum hoist, a rope is wound around two drums. Double drum hoists are less efficient than single drum hoists for most applications, but are preferred for lift systems with multiple hoists.^[13]

[edit] Common Manufacturers:

• Acco Material Handling Solutions Chester Hoist
• Columbus McKinnon Corporation
• Demag Cranes & Components Corporation
• Eimco Elecon India Ltd.
• Electrolift Inc.
• Ingersoll Rand Company
• Harrington Hoists Inc.
• J.D. Neuhaus L.P.
• R&M Materials Handling, Inc.
• STAHL CraneSystems, Inc.
• Yale Lift-Tech

[edit] References

1. ↑ Chain Hoist. Material Handling Equipment [October 20, 2009].
2. ↑ How it Works: Chain Hoist. CrazyBuilders.com [October 20, 2009].
3. ↑ Chain Hoist. Material Handling Equipment [October 20, 2009].
4. ↑ SME Mining Engineering Handbook 2nd Edition Volume 2. Hartman, Howard L. Society for Mining, Metallurgy, and Exploration, Inc: 1992.
5. ↑ Chain Hoist. Material Handling Equipment [October 20, 2009].
6. ↑ Product Guide. Hoist Manufacturers Institute [October 20, 2009].
7. ↑ SME Mining Engineering Handbook 2nd Edition Volume 2. Hartman, Howard L. Society for Mining, Metallurgy, and Exploration, Inc: 1992.
8. ↑ Introducing HMI. Hoist Manufacturers Institute [October 20, 2009].
9. ↑ Vane compressors. About-Air-Compressors.com [October 20, 2009].
10. ↑ Major Types of Pneumatic Devices. Britannica.com [October 20, 2009].
11. ↑ Cranes and Derricks. Shapiro, Howard I., Shapiro, Jay P., Shapiro, Lawrence K. McGraw-Hill: 1999.
12. ↑ SME Mining Engineering Handbook 2nd Edition Volume 2. Hartman, Howard L. Society for Mining, Metallurgy, and Exploration, Inc: 1992.
13. ↑ SME Mining Engineering Handbook 2nd Edition Volume 2. Hartman, Howard L. Society for Mining, Metallurgy, and Exploration, Inc: 1992.