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A washing machine is a machine designed to clean laundry, i.e.
clothing and other household textile
such as towels and sheets. It is generally restricted to machines that use water as the primary cleaning solution, as opposed to dry cleaning which uses alternative cleaning fluids and is generally performed by specialist businesses.
An early washing machine was constructed in 1767 by Jacob Christian
Schäffern.
Front-loading washing machine.
Mechanical washing machines date back to at least the 19th century, and
their basic principles of operation have remained largely unchanged. Their first purpose is to suspend the material to be cleaned
in water contaning detergent. The clothes
and water are then "agitated" - moved back and forth repeatedly. The water is then pumped out and the clothes partially dried by
spinning them rapidly in a low-speed centrifuge. Clean water is then added and
the clothes and water agitated to remove any remaining traces of the detergent. Finally, the clothes are (usually) spun again
(though some clothes are removed immediately and dried by alternative means without further spinning).
Virtually all contemporary washing machines are powered by electricity,
though hand-powered or even steam-powered machines were common in earlier times. They are almost universal in wealthier
countries, though some people living in smaller apartments do not have room for them and use communal launderettes.
Automatic washing machines became popular in the 1960s. These automate the washing
process by controlling the water and soap intake, draining and rotation of the drum in sequence. Different types of material can
be handled by using different programmed cycles. For example, a wool wash needs a low temperature and less agitation than a heavy
soil cotton wash. Most automatic washing machines control the sequence using an electromechanical cam timer, though recently fully electronic systems based on microprocessors have become more widely available. Another approach to programming the wash cycle that was
tried was the Hoover Keynetic system, in which plastic cartridges with different key-like profiles were inserted into a slot and read by a mechanical
reader. This system was short lived and not terribly successful - the cartridges were prone to getting lost and offered no real
advantage over the conventional rotary dial. In hindsight these can be seen as a marketing gimmick rather than a technological breakthrough.
Contemporary washing machines are available in two main configurations - "top loading" and "front loading". The "top loading"
design, the most popular in the United States, Australia and parts of Europe , places the clothes in a
vertically-mounted cylinder, with a propeller-like agitator in the center of the
bottom of the cylinder. Clothes are loaded at the top of the machine, which is covered with a hinged door. The "front loading"
design, most popular in the UK, instead mounts the cylinder horizontally, with loading through
a glass door at the front of the machine. The cylinder is also called the drum. Agitation is supplied by the
back-and-forth rotation of the cylinder, and by gravity. The items are lifted up by paddles in the drum then drop down to the
bottom of the drum. This motion forces water and detergent solution through the fabric. Although more infrequent, there is also a
variant of the horizontal axis design that is loaded from the top, through a flap in the circumference of the drum. These
machines usually have a shorter cylinder and are therefore smaller.
Tests comparing front-loading and top-loading machines have shown that, in general, front-loaders wash clothes more
thoroughly, cause less wear, and use less water and energy than top-loaders. As a result of using less water, they require less
detergent to be used. They also allow a dryer to be mounted directly above the washer,
impossible with a top-loader. Top-loaders do have the advantages that they complete washing much faster, tend to cost less for
the same capacity machine, and allow clothes to be removed at intermediate stages of the cycle (for instance, if some clothes
within a wash are not to be spun).
In the late 1990s, the British inventor
James Dyson launched a type of washing machine with two cylinders rotating in
opposite directions; which, it is claimed, reduces the wash time and produces cleaner results.
Washing /Drying machine
The single appliance can perform both washing and drying functions to cut out the process of loading and unloading clothes
from one machine to another.
The problem with such machines is that only half of the laundry can be dried after
the washing process is complete. Nowadays, some washing/driers are capable of performing both functions in a single machine
without interruption and with the full laundry load.
See also
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