The main components of a forklift include the power unit, transmission system, steering system, working mechanism, hydraulic system, and braking system.
① Power Unit
Forklifts are powered by either internal combustion engines or battery-electric motor systems. Battery-electric systems should be used in environments with strict noise and air pollution regulations; if internal combustion engines are used, they must be equipped with mufflers and exhaust purification devices.
② Transmission System
This system transmits power to the drive wheels and comes in three types: mechanical, hydrodynamic, and hydrostatic. A mechanical transmission consists of a clutch, a gearbox, and a drive axle. A hydrodynamic transmission comprises a torque converter, a powershift transmission, and a drive axle. A hydrostatic transmission consists of hydraulic pumps, valves, and hydraulic motors. A characteristic feature of forklift transmissions is that the number of gears and the speeds for forward and reverse travel are roughly the same.
③ Steering System
This system controls the forklift's direction of travel and generally consists of a steering gear, steering linkages, and steering wheels. Forklifts with a capacity of less than 1 ton typically use mechanical steering gears, while those with a capacity exceeding 1 ton mostly use power steering systems. A distinctive feature of forklift steering systems is that the steering wheels are located at the rear of the vehicle body.
④ Working Mechanism
This is the mechanism used to lift loads, also known as the mast assembly. It consists of an inner mast, an outer mast, a fork carriage, forks, sprockets, chains, a lifting cylinder, and a tilt cylinder. The lower end of the outer mast is hinged to the vehicle frame, while its middle section is hinged to the tilt cylinder. The extension and retraction of the tilt cylinder allow the mast to tilt forward and backward (typically within a range of 6° to 12°), ensuring load stability during picking and transport. The inner mast is equipped with rollers that fit into the outer mast, allowing it to extend partially beyond the outer mast when rising. The fork carriage also features rollers that fit into the inner mast, enabling vertical movement. The base of the lifting cylinder is fixed to the lower part of the outer mast, and its piston rod moves vertically along guide rails on the inner mast. A sprocket is mounted at the top of the piston rod; the lifting chain is anchored at one end to the outer mast, while the other end passes over the sprocket to connect to the fork carriage. As the piston rod rises, carrying the sprocket with it, the chain lifts the forks and the fork carriage. Initially, only the forks rise; the inner mast begins to ascend only after the piston rod makes contact with it, moving at half the speed of the forks. The maximum height the forks can reach while the inner mast remains stationary is known as the "free lift height"; this is typically around 300 mm. A mast design where the inner mast and fork carriage rise simultaneously only after the carriage has reached the top of the inner mast is called a "full free lift mast." In forklifts with a capacity of 10 tons or more, the sprocket is usually fixed directly to the top of the inner mast, meaning the lifting cylinder raises the mast immediately, precluding free lift. Forklifts with free lift capability can pass through doorways that are only slightly taller than the forklift itself. Full free lift forklifts are used in low-clearance environments; they avoid the issue where the inner mast strikes the ceiling before the forks reach the required height, making them suitable for operations inside ship holds and shipping containers. To improve operator visibility, the single lifting cylinder is replaced by two cylinders positioned on either side of the mast; this configuration is known as a "wide-view mast." Such masts are gradually replacing standard masts.
⑤ Hydraulic System
The system that provides power for lifting the forks and tilting the mast; it consists of components such as an oil pump, a multi-way directional control valve, and hydraulic lines.
⑥ Braking System
Similar to the braking system of an automobile, though forklift brakes are installed only on the drive wheels. A key performance parameter for a forklift is its rated lifting capacity at a standard lift height and standard load center distance. The load center distance is defined as the distance from the load's center of gravity to the front face of the vertical section of the forks.
