is a powered industrial truck
used to hoist and transport materials by means of steel forks
inserted under the load. The forklift was invented in 1917 by a transmission
manufacturing company in order to facilitate the movement of heavy automotive subassemblies. It has since become an indispensable piece of equipment in many manufacturing and warehousing operations.
A typical forklift may be generally described as follows:
- The truck proper, which is a motive machine with wheels powered through a transmission and drive train
- An internal-combustion (LPG, gasoline or diesel) engine, or a battery-powered motor
- The counterweight, which is a heavy iron mass attached to the rear of the machine, necessary to compensate for the load. In an electric forklift, the large lead-acid battery itself may serve as a counterweight
- The mast, which is the vertical assembly that does the work of raising, lowering, and tilting the load; the mast is hydraulically operated and consists of a cylinder and interlocking rails for lifting and lowering operations and for lateral stability
- The carriage, which comprises flat metal plate(s) and is moved along the mast by means of chains
- Forks, which are the L-shaped members that engage the load. The back vertical portion of the fork attaches to the carriage by means of a hook or latch; the front horizontal portion is inserted into or under the load. Alternatively, a variety of other equipment is available, including slipsheet clamps, carton clamps, carpet rams, pole handlers, and others.
- The load back rest, which is a rack-like extension attached to the carriage to prevent the load from shifting backward
- The driver's overhead guard, which is a metal roof, supported by posts, that helps protect the operator from any falling debris
- The cab, with a seat for the operator and pedals and switches for controlling the machine—the cab is typically open and bounded by the cage-like overhead guard assembly.
Forklifts are rated for loads at a specified maximum weight and a specified forward center of gravity. This information is located on a nameplate provided by the manufacturer, and loads must not exceed these specifications.
An important aspect of forklift operation is its rear-wheel steering. While this increases maneuverability in tight cornering situations, it differs from a driver’s traditional experience with other wheeled vehicles (from tricycles to tractors) and must be taken well into account.
Another critical characteristic of the forklift is its instability; the forklift and load must be considered a unit, with a continually varying center of gravity with every movement of the load. A forklift must never negotiate a turn at speed with a raised load, where centrifugal and gravitational forces may combine to cause a disastrous tipover accident. A forklift must not be used as a personnel elevator without the fitting of specific safety equipment. In the U.S., additional safety considerations are detailed in the applicable OSHA rules, and lift truck operators must be trained and certified.
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