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A forklift truck (often just called forklift) is a powered industrial truck used to lift and transport materials by means of steel forks inserted under the load. Forklifts are most commonly used to move loads stored on pallets. The forklift was developed in the 1920s by various companies including the transmission manufacturing company Clark (today known as Clark Material Handling Company) and the hoist company Yale & Towne Manufacturing (Today known as Yale Materials Handling Corporation)http://www.yale.com/ygl_history.asp?language=ENGLISH. It has since become an indispensable piece of equipment in many manufacturing and warehousing operations.

Characteristics

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 LPG, gasoline or diesel fueled internal combustion engine, or a battery-powered electric 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, usually on a pallet. 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 objects
  • The cab, with a seat for the operator and levers, pedals, switches and steering wheel for controlling the machine—the cab is typically open and bounded by the cage-like overhead guard assembly.

Design types

The Industrial Truck Association has organized a class system which all North American manufacturers adhere to. The most common design of forklift truck is the counterbalanced internal combustion engine forklift, or Class IV and V. Other types of design include the reach truck and sideloader, Class I and III, both of which are used in environments where space is at a premium. Another major differenciation between major types is the wheel type. Pneumatic tires are used on larger trucks that tend to operate over a wide variety of road surfaces--like gravel and asphalt. Cushion tires are used on trucks that primarily operate indoors--usually in a warehouse. Cushion tires can be smaller because they function less as a shock-absorbing element. This is also useful because cushion tire trucks must also be very compact.

Control and capability

Forklift trucks are available in many variations and load capacities. In a typical warehouse setting most forklifts used have load capacities of around one to five tons.

In addition to a control to raise and lower the forks (also known as blades or tines), the operator can tilt the mast to compensate for a load's tendency to angle the blades toward the ground and risk slipping off the forks. Tilt also provides a limited ability to operate on non-level ground. Some machines also allow the operator to move the tines and backrest laterally(side-shift), allowing easier placement of a load. To aid the handling of skids that may have become excessively tilted and other specialty material handling needs, some forklifts are fitted with a mechanism that allows the tines to be rotated. In addition, a few machines offer a hydraulic control to move the tines together or apart, removing the need for the operator to get out of the cab to manually adjust for a differently sized load.

Grab attachments for handling barrels or even kegs also have a control to operate the tongs that grab the load.

In some locations(such as carpet warehouses) a long metal pole is used instead of forks to lift large rolls.

Another variation, used in some manufacturing facilities, utilizes forklift trucks with a clamp attachment that the operator can open and close around a load, instead of forks. Products such as cartons, boxes, etc., can be moved with these trucks. The product to be moved is squeezed, lifted, and carried to its destination. These are generally referred to as "clamp trucks".

Forklift safety

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 as there is no caster action; indeed it is necessary to apply steering force to maintain a straight ahead course. These effects are observable when driving a car or other vehicle in reverse.

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. The Forklift will be designed with a load limit for the forks, which is decreased with fork elevation and undercutting of the load (ie load does not butt against the fork 'L'). A loading plate for loading reference is usually located on the forklift. A forklift must not be used as a personnel elevator without the fitting of specific safety equipment, such as a 'cherry picker' or 'cage'. In the U.S., additional safety considerations are detailed in the applicable OSHA rules, and lift truck operators must be trained and certified.

Today's Market

Five companies now dominate the counterbalanced forklift market in terms of worldwide sales. They are:

Notes

External links

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This article is licensed under the GNU Free Documentation License. It uses material from the "Forklift truck".

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