thumb|right|200px|Πλυντήριο ρούχων

Το πλυντήριο ρούχων είναι μία ηλεκτρική συσκευή, που σκοπό έχει το πλύσιμο των ειδών ρουχισμού και λοιπών υφασμάτων. Ο όρος ''πλυντήριο'' χρησιμοποιείται μόνο στις συσκευές/μηχανές που αντλούν νερό σαν κύριο μέσο καθαρισμού (π.χ. πλυντήριο πιάτων, πλυντήριο αυτοκινήτων), σε αντίθεση με το στεγνό καθαρισμό (που χρησιμοποιεί εναλλακτικά υγρά καθαρισμού και εκτελείται κατά κύριο λόγο από ειδικές επιχειρήσεις). 

==Η εφεύρεση==
Το πρώτο βρετανικό δίπλωμα ευρεσιτεχνίας για την κατηγορία πλυσίματος και στυψίματος μηχανών εκδόθηκε το αγγλική δημοσίευση. Το βρετανικό δίπλωμα ευρεσιτεχνίας για ένα πλυντήριο περιστρεφόμενων τυμπάνων στο Henry Sidgier. 
Πρώτες οι Ηνωμένες Πολιτείες κατοχυρώνουν, με τον τίτλο "ενδύματα που πλένονται, με δίπλωμα ευρεσιτεχνίας" στον Nathaniel Briggs από το Νιου Χάμπσαϊρ. Σε μια πυρκαγιά το 1797, καταστράφηκε το γραφείο διπλωμάτων ευρεσιτεχνίας και δεν σώθηκε καμία περιγραφή της συσκευής, έτσι δεν είναι γνωστό τι είδους λειτουργία είχε η συσκευή που "εφηύρε" ο Briggs. 

Το ηλεκτρικό πλυντήριο ρούχων παρήχθη πρώτη φορά μαζικά το αμερικανικών διπλωμάτων ευρεσιτεχνίας παρουσιάζει τουλάχιστον ένα δίπλωμα ευρεσιτεχνίας που εκδίδεται στο όνομα κάποιου κ. Φίσερ.

==Σχεδιασμός==
Τα πλυντήρια ρούχων είναι διαθέσιμα σε δύο κύριες μορφές: "επάνω φόρτωσης" και "μπροστινής φόρτωσης". Το σχέδιο "επάνω φόρτωσης" είναι δημοφιλέστερο στις Καναδά, την Ευρώπης: τοποθετεί τα ενδύματα σε έναν κάθετα τοποθετημένο κύλινδρο με έναν αναδευτήρα στο κέντρο του κυλίνδρου. Τα πλυντήρια "επάνω φόρτωσης" στην Ασία χρησιμοποιούν στροφεία αντί αναδευτήρων. Τα στροφεία είναι παρόμοια με τους αναδευτήρες εκτός από το ότι δεν έχουν την κεντρική θέση που επεκτείνεται επάνω και στη μέση του καλαθιού της σκάφης πλυσίματος. Τα ρούχα εισάγονται στον κάδο του πλυντηρίου από πάνω και καλύπτονται με δεύτερη μεταλλική πόρτα εκτός της κυρίας πόρτας στην οροφή του πλυντηρίου. 

Το σχέδιο "μπροστινής φόρτωσης", το δημοφιλέστερο στην ηλεκτρικά στοιχεία θέρμανσης για να θερμαίνουν το νερό. 

Συγκριτικές δοκιμές πλυντηρίων με "μπροστινή φόρτωση" και "επάνω φόρτωση" έχουν δείξει ότι γενικά τα πρώτα πλένουν τα ρούχα καλύτερα, προκαλούν τη λιγότερη φθορά, καταναλώνουν λιγότερο νερό και απορρυπαντικό και συμβάλλουν στην εξοικονόμηση ενέργειας σε αντίθεση με τα πλυντήρια "επάνω φόρτωσης". 
Προς το τέλος της δεκαετίας του '90, ο Βρετανός εφευρέτης James Dyson προώθησε έναν νέο τύπο πλυντηρίου ρούχων με δύο κυλίνδρους που περιστρέφονται σε αντίθετες κατευθύνσεις, μειώνοντας το χρόνο πλυσίματος και δίνοντας καθαρότερα αποτελέσματα, αλλά δεν έχει έως και σήμερα διατεθεί στην παραγωγή.

==Αξιολόγηση==
Η ικανότητα πλυσίματος και το κόστος είναι οι κύριες εκτιμήσεις για την αγορά ενός πλυντηρίου ρούχων. Στα πλυντήρια ρούχων δίνονται οι βαθμοί Eurobell για την απόδοση πλύσης, την ενεργειακή αποδοτικότητα και την αποδοτικότητα περιστροφής. Οι βαθμοί ξεκινούν από το Α μέχρι το Ε (από το καλύτερο προς το χειρότερο), και παρέχουν μια απλή μέθοδο για την οικονομία και την απόδοση. Μια μηχανή ΑΑΑ δηλώνει κορυφαία απόδοση στις τρεις κατηγορίες.

thumb|Front-loading washing machine.
A '''washing machine''', or '''washer''', is a machine designed to clean sheets. The term is mostly applied only to machines that use water as the primary cleaning solution, as opposed to dry cleaning (which uses alternative cleaning fluids, and is performed by specialist businesses) or even ultrasonic cleaners.

All washing machines work by using 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.

== History ==
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Clothing had been hand-washed for thousands of years, by flushing water through the fabric to remove loose dirt, rubbing with soap to remove oils and stains, and applying fragrances to cover odours. For particularly dirty clothing caked with mud or dirt, it was necessary to constantly rub and flex the cloth to break apart solids and help the soap penetrate through thick, dry, or sticky layers of soil on the cloth. At first this was done by pounding or rubbing the clothing with rocks in a river, and later developed into the corrugated wash board. In Roman times a fuller would whiten clothing by stomping on it in a bucket full of fermented urine.

Washing machine technology was developed as a way to reduce the drudgery of this scrubbing and rubbing process, by providing an open basin or sealed container with paddles or fingers to automatically agitate the clothing. The earliest machines were often hand-operated but were built with the belief that the machine itself was faster and easier to operate than washing the clothing by hand directly. As electricity was not commonly available until at least 1930, these early machines were often operated by a low-speed single-cylinder hit and miss gasoline engine.

Because water usually had to be heated on a fire for washing, the warm soapy water was precious and would be reused over and over, first to wash the least soiled clothing, then to wash progressively dirtier clothing. The load of soaking wet clothing would be removed, and another load of dirty clothes added to the machine. While the earliest machines were constructed entirely from wood, later machines made of metal permitted a fire to burn below the washtub, to keep the water warm throughout the day's washing.

Removal of soap and water from the clothing after washing was originally a separate process. The soaking wet clothing would be formed into a roll and twisted by hand to extract water. To help reduce this labour, the wringer/mangle was developed, which uses two rollers under spring tension to squeeze water out of the clothing. Each piece of clothing would be fed through the wringer separately. The first wringers were hand-operated, but were eventually included as a powered attachment above the washer tub. The wringer would be swung over the wash tub so that extracted wash water would fall back into the tub to be reused for the next wash load.

The modern process of water removal by spinning did not come into use until electric motors were developed. Spinning requires a constant high-speed power source, and was originally done in a separate device known as an extractor. A load of washed clothing would be transferred from the wash tub to the extractor basket, and the water spun out. These early extractors were often dangerous to use since unevenly distributed loads would cause the machine to shake violently. Many efforts have been made to counteract the shaking of unstable loads, first by mounting the spinning basket on a free-floating shock-absorbing frame to absorb minor imbalances, and a bump switch to detect severe movement and stop the machine so that the load can be manually redistributed. Many modern machines are equipped with a sealed ring of liquid around the top of the basket that works to counteract any imbalances.

What is now referred to as an automatic washer was at one time referred to as a washer/extractor, which combines the features of these two devices into a single machine, plus also includes the ability to fill and drain water by itself. It is possible to take this a step further, to also merge the automatic washing machine and clothes dryer into a single device, but this is generally uncommon because the drying process tends to use much more energy than using two separate devices; a combined washer/dryer not only must dry the clothing, but also needs to dry out the wash chamber itself.

== Washing machine milestones ==
thumb|19th-century Metropolitan washing machinethumb|A vintage German model

The first English patent under the category of Washing and Wringing Machines was issued in 1691.  A drawing of an early washing machine appeared in the January 1752 issue of "The Gentlemen's Magazine," a British publication. In Germany, Jacob Christian Schäffer's washing machine design was published in 1767.[http://www.deutsches-museum.de/bibliothek/unsere-schaetze/technikgeschichte/schaeffer/]  In 1782 Henry Sidgier was issued a British patent for a rotating drum washer.

The first United States Patent titled "Clothes Washing" was granted to Nathaniel Briggs of New Hampshire in 1797. Fire destroyed the patent office and no description of the device exists so it is not known what kind of washing device Briggs invented. A device that combined a washing machine with a wringer mechanism did not appear until 1843 when John E. Turnbull of Saint John, New Brunswick patented a "Clothes Washer With Wringer Rolls."<ref>Mario Theriault, ''Great Maritme Inventions 1833-1950'', Goose Lane, 2001, p. 28</ref>

Electric Washing Machines were advertised and discussed in newspapers as early as 1904.<ref>"Electric Washing Machine the Latest. Housewives can do Washing in one-third the Time," Des Moines Daily Capitol, November 12, 1904, p. 13.</ref> Louis Goldenberg of New Brunswick NJ invented the electric washing machine around the late 1800s to early 1900s. He worked for the Ford Motor Company at that time, and all inventions that were created while working for Ford under contract, belonged to Ford. The patent would have been listed under Ford and or Louis Goldenberg.[This sentence needs an inline citation. Claim is highly unlikely.  Ford Motor Company did not exist prior to 1903 and there is substantial evidence of prior art making a claim of inventing electric power source for washing machines highly unpatentable.] Alva J. Fisher has been incorrectly credited with the invention of the electric washer. The US patent office shows at least one patent issued before Mr. Fisher's US patent number 966677 (e.g. Woodrow's US patent number 921195).

US electric washing machine sales reached 913,000 units in 1928. However, high unemployment rates in the Depression years hit sales; by 1932 the number of units shipped was down to about 600,000.

The first laundromat opened in Fort Worth, Texas in 1934.  It was run by Andrew Clein. Patrons used coin-in-the-slot facilities to rent washing machines. [This claim highly unlikely. The term laundromat can be found in newspapers as early as 1884 and they were widespread during the depression. It is almost impossible to determine who had the "first" laundromat. England established public "wash rooms" for laundry along with bath houses throughout the nineteenth century.<ref>New York Times, April 13, 1884; New London Journal, July 22, 1917</ref>]

Washer design improved during the 1930s; the mechanism was now enclosed within a cabinet; more attention was paid to electrical safety; spin dryers were introduced, to replace the dangerous power wringers of the day. [This claim is misleading.  Spin dryers competed, but not very successfully, with wringer washers.  Wringer washers dominated the conventional market until the last conventional washer was produced in the 1980s.  At no time did the double tub spin dry washers threaten, much less replace, the wringer washer market.]

Early automatic washing machines were usually connected to the water supply via temporary slip-on connectors to the sink taps. Later, permanent connections to both the hot and cold water supplies became the norm. Most modern front-loading European machines now only have a cold water connection (i.e. cold fill) and rely completely on electric heaters to raise the water temperature.

By 1940, 60% of the 25,000,000 wired homes in the United States had an electric washing machine. Many of these machines featured a power wringer, although built-in spin dryers were not uncommon.

Bendix introduced the first automatic washing machine in 1937,<ref>http://www.oldewash.com/cf/images/IMAGES/327.jpg</ref> having applied for a patent in the same year.<ref>http://www.google.com/patents?vid=USPAT2165884&id=VDdKAAAAEBAJ&pg=PA3-IA1&dq=2,165,884#PPA3-IA1,M1</ref> In appearance and mechanical detail, this first machine is not unlike the front loading automatic washers produced today. Although it included many of the today's basic features, the machine lacked any drum suspension and therefore had to be anchored to the floor to prevent "walking".

Many of these early automatic machines had coin-in-the-slot facilities and were installed in the basement laundry rooms of apartment houses. After the attack on Pearl Harbor, US domestic washer production had to be suspended for the duration of World War II. However, many US appliance manufacturers were given permission to undertake the research and development of washers during the war years. Many took the opportunity to develop automatic machines, realising that these represented the future for the industry.

An improved front loading automatic model, the Bendix Deluxe (which retailed at $249.50) was introduced in 1947.<ref>[http://68.89.57.239/VID/47BENDIX/Bendix_Wash.wmv video demonstration]</ref>

General Electric introduced the first top loading automatic also in 1947. This machine had many of the features that are incorporated into modern machines.

A large number of US manufacturers introduced competing automatic machines (mainly of the top loading type) in the late 1940s/early 1950s. Several manufacturers even produced semi-automatic machines, where the user had to intervene at one or two points in the wash cycle.  A common semi-automatic type (available from Hoover in the UK until at least the 70's) included 2 tubs:  one with an agitator or impeller for washing and/or rinsing; another, smaller, tub for water extraction or centrifugal rinsing.

Since their introduction in the late 1930s/mid 1940s, automatic washing machines have relied on mechanical timers to sequence the washing and extraction process. Mechanical timers consist of a series of cams on a common shaft. At the appropriate time in the wash cycle, each cam actuates a switch to engage/disengage a particular part of the machinery (e.g. drain pump motor). The timer shaft is driven by a small electric motor via a reduction gearbox.

On the early mechanical timers the motor ran at a constant speed throughout the wash cycle, although it was possible for the user to truncate parts of the program, by manually advancing the control dial. However, by the 1950s demand for greater flexibility in the wash cycle led to the introduction of electronic timers to supplement the mechanical timer. These electronic timers enable greater variation in such functions as the wash time. With this arrangement, the electric timer motor is periodically switched-off to permit the clothing to soak, and is only re-energised just prior to a micro-switch being engaged/disengaged.

Despite the high cost of automatic washers, manufacturers had difficulty in meeting the demand. Although there were material shortages during the Korean War, by 1953 automatic washing machine sales in the US exceeded those of wringer-type electric machines.

In the UK and in most of Europe, electric washing machines did not become popular until the 1950s. This was largely because of the economic impact of World War II on the consumer market which did not properly recover until the late 1950s. The early electric washers were single tub, wringer-type machines, automatic washing machines being extremely expensive. During the 1960s, twin tub machines briefly became very popular, helped by the low price of the Rolls Razor washers. Automatic washing machines did not become dominant in the UK until well into the 1970 and by then were almost exclusively of the front-loader design.

In early automatic washing machines, any changes in impeller/drum speed were achieved by mechanical means or by a rheostat on the motor power supply. However, since the 1970s electronic control of motor speed has become a common feature on the more expensive models.

Early front loading machines, especially those manufactured in Mediterranean countries (e.g. Italy), had low spin speeds (e.g. 800 rpm or less). Nowadays, a spin speed of 1200 rpm is common and a peak spin speed as high as 1600 rpm is available on some machines. Now models in Europe have speeds of 1800 rpm and one washing machine has a spin speed of 2000 rpm. However, because they were not susceptible to gravitational forces, some early top loading machines had spin speeds in excess of 1000 rpm, although some were as low as 360 rpm.

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; however, this machine is not now in production.

In the 1990s, upmarket machines incorporated microcontrollers for the timing process. These proved reliable, so many cheaper machines now incorporate microcontrollers, rather than mechanical timers. Washing machines are a classic application for fuzzy logic.

In 1994, Staber Industries released the System 2000 washing machine, which is the only top loading, horizontal-axis washer to be manufactured in the United States.  The hexagonal tub spins like a front loading machine, only using about third of the water as conventional top-loaders.  This factor has led to an Energy Star rating for its high efficiency. 

In 2001, nutated to bounce, shake, and toss the laundry around. As this happened, water containing detergent was sprayed on to the laundry. The machine proved to be good at cleaning but gained a bad reputation due to frequent breakdowns and destruction of laundry and the washer was recalled with a class-action lawsuit and pulled off the market.

In 2006, Sanyo introduced the first drum type washing machine with ‘Air Wash’ function.<ref>[http://www.sanyo.co.jp/koho/hypertext4-eng/0602/0202-1e.html SANYO Announces the World-First*1 Drum Type Washing Machine with ‘Air Wash’ Function<!-- Bot generated title -->]</ref> This washing machine uses only 50L of water in the recycle mode.

In 2008, the university of Leeds created a washing machine that uses only a cup of water to carry out a full wash. The machine leaves clothes virtually dry, and uses less than 2 per cent of the water and energy otherwise used by a conventional machine. As such, it could save billions of litres of water each year. <ref>[http://www.dailymail.co.uk/sciencetech/article-1025043/Spin-dry-The-washing-machine-needs-just-cup-water.html?ITO=1490Ûniversity University of Leeds creating a washing machine that needs but 2% of the water/electricity requirements of a conventional washing machine]</ref>

== Modern machines ==
Modern washing machines are available in two configurations: top loading and front loading.

The top loading design, most popular in agitator in the center of the bottom of the basket. Clothes are loaded through the top of the machine, which is covered with a hinged door. During the wash cycle, the outer tub is filled with water sufficient to suspend the clothing freely in the basket, and the movement of the agitator pulls the clothing downward in the center towards the agitator paddles. The clothing then moves outward and up the sides of the basket to repeat the process. Top-loaders are not well-suited to cleaning large objects such as pillows or sleeping bags due to the tendency for them to just float on the surface of the water without circulating, and the aggressive agitator action can damage delicate fabrics.

In most top loading washers, if the motor spins in one direction, the gearbox drives the agitator; if the motor spins the other way, the gearbox locks the agitator and spins the basket and agitator together. Similarly if the pump motor rotates one way it recirculates the sudsy water; in the other direction it pumps water from the machine during the spin cycle. Because they usually incorporate a gearbox, clutch, crank, etc, top loading washers are mechanically more complex than front loading machines but are generally lower maintenance since there is no need for a complex door seal (described below). 

The front loading design, most popular in Europe and the Middle East, mounts the inner basket and outer tub horizontally, and loading is through a door at the front of the machine.  The door often but not always contains a window. Agitation is supplied by the back-and-forth rotation of the cylinder and by gravity. The clothes are lifted up by paddles on the inside wall of the drum and then dropped. This motion flexes the weave of the fabric and forces water and detergent solution through the clothes load. Because the wash action does not require the clothing be freely suspended in water, only enough water is needed to moisten the fabric. Because less water is required, front-loaders typically use less soap, and the aggressive dropping and folding action of the tumbling can easily produce large amounts of foam. 

Front-loaders control water usage through the surface tension of water, and the capillary wicking action this creates in the fabric weave. A front-loader washer always fills to the same low water level, but a large pile of dry clothing standing in water will soak up the moisture, causing the water level to drop. The washer then refills to maintain the original water level. Because it takes time for this water absorption to occur with a motionless pile of fabric, nearly all front-loaders begin the washing process by slowly tumbling the clothing under the stream of water entering and filling the drum, to rapidly saturate the dry clothes with water.

Front loading washers are mechanically simple compared to top-loaders, with the main motor normally being connected to the drum via a grooved pulley belt and large pulley wheel, without the need for a gearbox, clutch or crank. But front-load washers suffer from their own technical problems, due to the drum lying sideways. For example, a top loading washer keeps water inside the tub merely through the force of gravity pulling down on the water, while a front-loader must tightly seal the door shut with a gasket to prevent dripping water onto the floor during the wash cycle. This access door is locked shut during the entire wash cycle, since opening the door with the machine in use could result in water gushing out onto the floor. For front-loaders without viewing windows on the door, it is possible to accidentally pinch fabric between the door and the drum, resulting in tearing and damage to the pinched clothing during tumbling and spinning.

Nearly all front-loader washers for the consumer market must also use a folded flexible bellows assembly around the door opening, to keep clothing contained inside the basket during the tumbling wash cycle. If this bellows assembly were not used, small articles of clothing such as socks could slip out of the wash basket near the door, and fall down the narrow slot between the outer tub and basket, plugging the drain and possibly jamming rotation of the inner basket. Retrieving lost items from between the outer tub and inner basket can require complete disassembly of the front of the washer and pulling out the entire inner wash basket. Commercial and industrial front-loaders used by businesses (described below) usually do not use the bellows, and instead require all small objects to be placed in a mesh bag to prevent loss near the basket opening. 

This bellows assembly around the door is the source of problems for the consumer front-loader. The bellows has a large number of flexible folds to permit the tub to move separately from the door during the high speed extraction cycle. These folds can collect lint, dirt, and moisture, resulting in mold and mildew growth and a foul odor. Some front-loading washer operating instructions say the bellows should be wiped down monthly with a strong bleach solution, while others offer a special ''freshening'' cycle where the machine is run empty with a strong dosing of bleach. 