Forklifts

A forklift (also called a lift truck, a fork truck, or a forklift truck) is a powered industrial truck used to lift and move materials short distances. 
Operation
Forklifts are rated for loads at a specified maximum weight and a specified forward center of gravity. An important aspect of forklift operation is that it must have rear-wheel steering. While this increases maneuverability in tight cornering situations, it differs from a driver’s traditional experience with other wheeled vehicles. While steering, as there is no caster action, it is unnecessary to apply steering force to maintain a constant rate of turn. 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 tip-over accident. The forklift is designed with a load limit for the forks which is decreased with fork elevation and undercutting of the load (i.e., when a load does not butt against the fork "L"). A loading plate for loading reference is usually located on the forklift. A forklift should not be used as a personnel lift without the fitting of specific safety equipment, such as a "cherry picker" or "cage".
Forklifts are a critical element of warehouses and distribution centers. It’s imperative that these structures be designed to accommodate their efficient and safe movement. In the case of Drive-In/Drive-Thru Racking, a forklift needs to travel inside a storage bay that is multiple pallet positions deep to place or retrieve a pallet. Often, forklift drivers are guided into the bay through guide rails on the floor and the pallet is placed on cantilevered arms or rails. These maneuvers require well-trained operators. Since every pallet requires the truck to enter the storage structure, damage is more common than with other types of storage. In designing a drive-in system, dimensions of the fork truck, including overall width and mast width, must be carefully considered.
Construction of Fork Lift

• Truck frame - is the base of the machine to which the mast, axles, wheels, counterweight, overhead guard and power source are attached. The frame may have fuel and hydraulic fluid tanks constructed as part of the frame assembly.
• Counterweight - is a mass attached to the rear of the forklift truck frame. The purpose of the counterweight is to counterbalance the load being lifted. In an electric forklift the large lead-acid battery itself may serve as part of the counterweight.
• Cab - is the area that contains a seat for the operator along with the control pedals, steering wheel, levers, switches and a dashboard containing operator readouts. The cab area may be open air or enclosed but it is covered by the cage-like overhead guard assembly. When enclosed, the cab may also be equipped with a cab heater for cold climate countries along with a fan or air conditioning for hot weather.
• Overhead guard - is a metal roof supported by posts at each corner of the cab that helps protect the operator from any falling objects. On some forklifts, the overhead guard is an integrated part of the frame assembly.
• Power source - may consist of an internal combustion engine that can be powered by LP gas, CNG, gasoline or diesel fuel. Electric forklifts are powered by either a battery or fuel cells that provides power to the electric motors. The electric motors used on a forklift may be either DC or AC types.
• Tilt cylinders - are hydraulic cylinders that are mounted to the truck frame and the mast. The tilt cylinders pivot the mast backward or forward to assist in engaging a load.
• Mast - is the vertical assembly that does the work of raising and lowering the load. It is made up of interlocking rails that also provide lateral stability. The interlocking rails may either have rollers or bushings as guides. The mast is driven hydraulically, and operated by one or more hydraulic cylinders directly or using chains from the cylinder/s. It may be mounted to the front axle or the frame of the forklift. A 'container mast' variation allows the forks to raise a few meters without increasing the total height of the forklift. This is useful when double-loading pallets into a container or under a mezzanine floor.
• Carriage - is the component to which the forks or other attachments mount. It is mounted into and moves up and down the mast rails by means of chains or by being directly attached to the hydraulic cylinder. Like the mast, the carriage may have either rollers or bushings to guide it in the interlocking mast rails.
• Load back rest - is a rack-like extension that is either bolted or welded to the carriage in order to prevent the load from shifting backward when the carriage is lifted to full height.
• Attachments - may consists of a mechanism which is attached to the carriage, either permanently or temporarily, to help in proper engagement of the load. A variety of material handling attachments are available. Some attachments include sideshifters, slipsheet attachments, carton clamps, multipurpose clamps, rotators, fork positioners, carpet poles, pole handlers, container handlers and roll clamps.
• Tires - either solid for indoor use, or pneumatic for outside use.

Attachments

• Dimensioning devices-fork truck-mounted dimensioning systems provide dimensions for the cargo to facilitate truck trailer space utilization and to support warehouse automation systems. The systems normally communicate the dimensions via 802.11 radios. NTEP certified dimensioning devices are available to support commercial activities that bill based on volume.
• Sideshifter - is a hydraulic attachment that allows the operator to move the tines (forks) and backrest laterally. This allows easier placement of a load without having to reposition the truck.
• Rotator - To aid the handling of skids that may have become excessively tilted and other specialty material handling needs some forklifts are fitted with an attachment that allows the tines to be rotated. This type of attachment may also be used for dumping containers for quick unloading.
• Fork positioner - is a hydraulic attachment that moves the tines (forks) together or apart. This removes the need for the operator to manually adjust the tines for different sized loads.
• Roll and barrel clamp attachment - A mechanical or hydraulic attachment used to squeeze the item to be moved. It is used for handling barrels, kegs, or paper rolls. This type of attachment may also have a rotate function. The rotate function would help an operator to insert a vertically stored paper into the horizontal intake of a printing press for example.
• Pole attachments - In some locations, such as carpet warehouses, a long metal pole is used instead of forks to lift carpet rolls. Similar devices, though much larger, are used to pick up metal coils.
• Carton and multipurpose clamp attachments - are hydraulic attachments that allow the operator to open and close around a load, squeezing it to pick it up. Products like cartons, boxes and bales can be moved with this type of attachment. With these attachments in use, the forklift truck is sometimes referred to as a clamp truck.
• Slip sheet attachment (push - pull) - is a hydraulic attachment that reaches forward, clamps onto a slip sheet and draws the slip sheet onto wide and thin metal forks for transport. The attachment will push the slip sheet and load off the forks for placement.
• Drum handler attachment - is a mechanical attachment that slides onto the tines (forks). It usually has a spring-loaded jaw that grips the top lip edge of a drum for transport. Another type grabs around the drum in a manner similar to the roll or barrel attachments.
• Man basket - a lift platform that slides onto the tines (forks) and is meant for hoisting workers. The man basket has railings to keep the person from falling and brackets for attaching a safety harness. Also, a strap or chain is used to attach the man basket to the carriage of the forklift.
• Telescopic forks - are hydraulic attachments that allow the operator to operate in warehouse design for "double-deep stacking", which means that two pallet shelves are placed behind each other without any aisle between them.
• Scales -Fork truck-mounted scales enable operators to efficiently weigh the pallets they handle without interrupting their workflow by travelling to a platform scale. Scales are available that provide legal-for-trade weights for operations that involve billing by weight. They are easily retrofitted to the truck by hanging on the carriage in the same manner as forks hang on the truck.
• Single-double forks - are forks that in the closed position allow movement of a single pallet or platform but when separated, turn into a set of double forks that allow carrying two pallets side by side. The fork control may have to replace the side-shifter on some lift trucks.