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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.

History

An early washing machine was constructed in 1767 by Jacob Christian Schäffern (or Jacob Christian Schäffer).

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 containing 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 Keymatic 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.

Modern machines

Contemporary washing machines are available in two main configurations: "top loading" and "front loading". The "top loading" design, 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. "Top loading" machines in Asia use impellers instead of agitators. Impellers are similar to agitators except that they don't have the center post extending up in the middle of the wash tub basket. Clothes are loaded through the top of the machine, which is covered with a hinged door. The "front loading" design, most popular in Europe, instead mounts the cylinder horizontally. Loading is 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 clothes are lifted up by paddles in the drum and then dropped. This motion flexes the weave of the fabric and forces water and detergent solution through the clothes load. Although more infrequent, there is also a variant of the horizontal axis design that is loaded from the top, through a small door in the circumference of the drum. These machines usually have a shorter cylinder and are therefore smaller.

All washing machines work by using three different sources of energy. They use mechanical energy, thermal energy, and chemical action. Mechanical energy is imparted to the clothes load by the rotation of the agitator in "top loaders", or by the tumbling action of the drum in "front loaders". Thermal energy is supplied by the temperature of the wash bath. Many "front loading" machines have electrical heating elements to heat the wash bath to near boiling. Chemical action is supplied by the detergent and other laundry chemicals. "Front loaders" use special detergents that are designed to release different chemical ingredients at different tempertures. This is so that different type of stains and soils will be cleaned from the clothes as the wash water is heated up by the electrical heater. "Front loaders" also need to use low sudsing detergents because the tumbling action of the drum folds air into the clothes load that can cause over sudsing.

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, or conversely, they can use the same amount of detergent with less water, which increaes detergent concentration and increases the amount of chemical action. They also allow a dryer to be more easily mounted directly above the washer. Top-loaders do have the advantage in that they complete a washing cycle 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.

Agitator

An agitator is the mechanism in a top load washing machine that projects from the bottom of the wash basket that creates the wash action by rotating back and forth, rolling garments from the top of the load, down to the bottom, then back up again.

The following types are known: dual-rollover, dual-action, and triple-rollover action agitators.

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.

Connectivity

Some modern washing machines include USB or Wifi ports to connect to a domotic network or to the Internet.

See also

• Bleach
• Centrifugation.
• Clothes dryer
• Energetic efficiency
• Home appliance and major appliance
• Laundry symbols

Patents

• Fisher, A. J., U.S. patent 966,677, "Drive mechanism for washing machine", August 9, 1910

External links

• How Washing Machines Work Article by HowStuffWorks.com
• How Washing Machines Work Article by RepairClinic.com
• Free downloadable guide to everything about dryers from Quamut.com

• Domotics
• Home appliances
• Centrifuges
• Cleaning tools