History of
Forklifts
A forklift truck,
a lift truck, a High/Low or a forklift and sideloader is a powered
industrial truck used to lift and transport materials, normally
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).
It has since become an indispensable piece of equipment in manufacturing
and warehousing operations.
Design types
There are many national
and/or continental associations related to the industrial trucks.
The three major ones are the Industrial Truck Association (North
America), the Fédération Européenne de la
Manutention (Europe), and the Japan Industrial Vehicles Association
(Japan). There are many significant contacts among them and they
have established joint statistical and engineering programs. One
program is the WITS (World Industrial Trucks Statistics) published
every month to the association memberships. The statistics are
separated by area (continent), country, and class of machine.
While the statistics are generic, and do not count production
from most of the smaller manufacturers, the information is significant
for its depth. These contacts have brought to a common definition
of the Class System, which all the major manufacturers adhere
to. Following is the list of the more common truck types, from
the smallest to the biggest:
• Hand Pallet Truck (a "pump truck" or a "Chep
truck", a simple mechanism whereby hand-pumped hydraulics
raise or lower a single pallet simply to provide clearance from
the floor for manual (hand) pulling; heavy loads are unwieldy
or risk injury to operators.)
• Walkie low
lift truck (powered pallet truck, usually electrically powered)
• Rider low lift truck
• Towing tractor
• Walkie stacker
• Rider stacker
• Reach truck (small forklift, designed for small aisles,
usually electrically powered)
• Electric counterbalanced truck
• IC counterbalanced truck
• Sideloader
• Telescopic handler
• Slip Sheet machine
• Walkie Order Picking truck
• Rider Order Picking truck (commonly called an "Order
Picker"; like a small forklift, except the operator rides
up to the load and transfers it article by article)
• Very narrow aisle truck (usually a reach truck designed
for aisles less than five feet wide)
For a common (North
American) reference, Home Depot, Lowes and Rona generally employ
reach trucks inside the store and "traditional" forklifts
when the store is closed. Most employees of such warehouse stores
will happily explain the differences between the machines.
Characteristics
A typical forklift
may be generally described as follows:
• The truck
proper, which is a motive machine with wheels and/or tracks powered
through a drive train.
• A liquefied petroleum gas (LPG)–, petrol- or diesel
fueled internal combustion engine, or an electric motor(s) either
direct current or alternating current powered by either a battery
or fuel cells.
• The mast, which is the vertical assembly that does the
work of raising, lowering, and tilting the load; the mast is either
hydraulically operated consisting of one or more cylinder(s) and
interlocking rails for lifting and lowering operations and for
lateral stability, or it may be chain operated with a hydraulic
motor providing motive power.
• The carriage, which comprises flat metal plate(s) and
is moved along the mast either by means of chains, or by being
directly attached to the hydraulic cylinder.
• One or more forks, which are the L-shaped members that
engage the load. The back vertical portion of the fork attaches
to the carriage most often by means of a hook or latch (Class
I to IV forks), while some forks use a shaft mount. The front
horizontal portion (which is usually tapered for ease of insertion)
is inserted into or under the load, usually on a pallet or skid.
Alternatively, a variety of other equipment is available, including
slipsheet clamps, carton clamps, carpet rams, pole handlers, container
handlers, roll clamps and others.
• A load back rest is fitted when the load is higher than
the top of the carriage, and is a rack-like extension either bolted
or welded to the carriage to prevent the load from shifting backward.
• Rider operated machines have a driver's overhead guard,
which is a metal roof, supported by posts, that helps protect
the operator from any falling objects.
• The cab, which may contain a seat for the operator, along
with the control pedals, steering wheel, levers, and switches
for controlling the machine and a dashboard containing operator
readouts. The cab may be open, or closed, but is bounded by the
cage-like overhead guard assembly.
• Counterbalance machines have a 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 part of the counterweight.
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, though machines of over 50 tonnes capacity
have been built and operated.
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.
Roll and barrel
clamp attachments for handling barrels, kegs, or paper rolls also
have a control to operate the clamp pads that grab the load, such
attachments also usually have a rotate function so that a vertically
stored paper roll can be inserted into the horizontal intake of
a printing press.
In some locations (such as carpet warehouses) a long metal pole
is used instead of forks to lift large rolls. Similar devices,
though much larger, are used to pick up 40 tonne metal coils.
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".
Skilled forklift
operators annually compete in obstacle and timed challenges at
regional forklift rodeos.
Over 300 brands of
forklift have existed. Many have disappeared through acquisitions,
others have gone bankrupt, and some shut down.
