Washing Machine

History

An early washing machine was constructed in 1767 by Jacob Christian Schaffer.

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, 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).