Editing Washing machine (section)

==Types==
===Top-loading===
{{anchor|Toploader}}
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[[File:GE 2 Speed Commercial Washers.JPG|thumb|General Electric Filter-Flo top-loading, vertical-axis machines installed in a laundromat. The pans on the inside of the lid are placed atop the agitator, and wash water is pumped through the perforated pans to collect lint. (California)]]
[[File:Toroidal coord.png|thumb|In a top-loading washer, water circulates primarily along [[Toroidal and poloidal coordinates|the poloidal axis]] during the wash cycle, as indicated by the red arrow in this illustration of a [[torus]].]]

The top-loading, vertical-axis washer has been the dominant design in the United States and Canada. This design places the clothes in a vertically mounted perforated basket that is contained within a water-retaining tub, with a finned water-pumping [[agitator (device)|agitator]] in the center of the bottom of the basket. Clothes are loaded through the top of the machine, which is usually but not always covered with a hinged door. The drum of a top loading washing machine can include a lint trap.<ref>{{Cite web|url=https://www.samsung.com/au/support/home-appliances/clean-top-load-lint-filter/|title=Cleaning the Lint Filter of a Samsung Top Load Washing Machine &#124; Samsung Australia}}</ref>

====Agitation====
During the wash cycle, the outer tub is filled with water sufficient to fully immerse and suspend the clothing freely in the basket. The movement of the agitator pushes water outward between the paddles towards the edge of the tub. The water then moves outward, up the sides of the basket, towards the center, and then down towards the agitator to repeat the process, in a circulation pattern similar to the shape of a [[torus]]. The agitator direction is periodically reversed because continuous motion in one direction would just lead to the water spinning around the basket with the agitator rather than the water being pumped in the torus-shaped motion. Some washers supplement the water-pumping action of the agitator with a large rotating screw on the shaft above the agitator, to help move water downwards in the center of the basket. A washing machine can have an impeller, also called a wash plate, instead of an agitator, which serves the same purpose but does not have a vertical cylinder extending from its base.

Since the agitator and the drum are separate and distinct in a top-loading washing machine, the mechanism of a top-loader is inherently more complicated than a front-loading machine. Manufacturers have devised several ways to control the motion of the agitator during the wash and rinse separately from the high-speed rotation of the drum required for the spin cycle. While a top-loading washing machine could use a [[universal motor]] or DC brushless motor, it is conventional for top-loading washing machines to use more expensive, heavy, and potentially more electrically efficient and reliable [[induction motor]]s.

An alternative to this oscillating agitator design is the impeller-type washtub pioneered by [[The Hoover Company|Hoover]] on its long-running ''Hoovermatic'' series of top-loading machines. Here, an [[impeller]] (trademarked by Hoover as a "Pulsator") mounted on the side of the tub spins in a constant direction and creates a fast-moving current of water in the tub which drags the clothes through the water along a toroidal path. This design was used in the Hoover 0307 washer. The impeller design has the advantage of mechanical simplicity – a single-speed motor with belt drive is all that is required to drive the Pulsator with no need for gearboxes or complex electrical controls, but has the disadvantage of lower load capacity in relation to tub size. Hoovermatic machines were made mostly in twin-tub format for the European market (where they competed with [[Hotpoint]]'s ''Supermatic'' line which used the oscillating agitator design) until the early 1990s. Some industrial garment testing machines still use the Hoover wash action. Another alternative involves 'pulsating' the agitator, in other words having an agitator with a reciprocating motion along its vertical axis.<ref>{{Cite web | url=http://www.uncleharrywizard.com/nephewclub/wizardwasher/electrolux-frigidaire/frigidaire---unimatic-.pdf | title=Repair Maste dor Frigidaire Automatic Washers | website=www.uncleharrywizard.com}}</ref> Some washing machines have agitators that move in an orbiting motion<ref>{{Cite web|url=https://patents.google.com/patent/US2973193A/en?q=(agitator)&assignee=American+Motors+Corp&oq=assignee:(American+Motors+Corp)+agitator+|title=Washing machine}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US2909051A/en?q=(agitator)&assignee=American+Motors+Corp&oq=assignee:(American+Motors+Corp)+agitator+|title=Washing machine}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US3043435A/en?q=(washing+machine+eccentric)&assignee=American+Motors+Corp&oq=assignee:(American+Motors+Corp)+washing+machine+eccentric|title=Centering and stabilizing apparatus for a combined washing machine and extractor}}</ref> or agitators that nutate at the bottom.<ref>{{Cite web|url=https://patents.google.com/patent/US2871689A/en?q=(wobbling+washing+machine)&assignee=Philco+Ford+Corp&oq=assignee:(Philco+Ford+Corp)+wobbling+washing+machine&sort=old|title=Clothes washing machine}}</ref><ref>{{cite book | url=https://books.google.com/books?id=ln_jolSJWLQC&q=%22Bendix%20Introduces%20New%20Washing%20Principle%20That%20Replaces%20Agitator%20With%20Water%20Action%22 | title=Electrical Dealer | date=1955 }}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US3102410/en|title=Laundry machine utilizing a wobble-type agitator}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US3102408A/en?q=(agitator)&assignee=Philco+Ford+Corp&oq=assignee:(Philco+Ford+Corp)+agitator&page=1|title=Laundry apparatus}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US2902851A/en?q=(agitator)&assignee=Philco+Ford+Corp&oq=assignee:(Philco+Ford+Corp)+agitator&page=1|title=Clothes washing machine having a wobble-type agitator}}</ref> Special top loading washing machines designed for washing sneakers can incorporate bristles in their agitators.<ref>{{Cite web | url=https://aqua-has.com/biz/wp-content/uploads/2022/04/%E5%8F%96%E6%89%B1%E8%AA%AC%E6%98%8E%E6%9B%B8_MCW-W7C_se.pdf | title=取扱説明書 | language=zh | trans-title=Operating instructions | website=aqua-has.com}}</ref> Alternatively the inner tub itself can nutate inside the outer tub.<ref>{{Cite web|url=https://patents.google.com/patent/US2672744/en|title=Wobbling basket type clotheswashing machine}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US2655804A/en?q=(wobble)&assignee=Murray+Corp&oq=assignee:(Murray+Corp)+wobble|title=Washing machine}}</ref>

The many different ways manufacturers have solved the same problem over the years is a good example of many different ways to solve the same [[engineering]] problem with different goals, different manufacturing capabilities and expertise, and different [[patent]] encumbrances.

====Reversible motor====
In many current top-loading washers, if the motor spins in one direction, the [[Transmission (mechanics)|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. Mechanically, this system is very simple.<ref name="uncleharrywizard.com"/>

====Mode-changing transmission====
In some top-loaders, the motor runs only in one direction. During agitation, the transmission converts the rotation into the alternating motion driving the agitator. During the spin cycle, the timer turns on a [[solenoid]] which engages a [[clutch]] locking the motor's rotation to the wash basket, providing a spin cycle. General Electric's very popular line of Filter-Flo (seen to the right) used a variant of this design where the motor reversed only to pump water out of the machine. The same clutch which allows the heavy tub full of wet clothes to "slip" as it comes up to the motor's speed, is also allowed to "slip" during agitation to engage a Gentle Cycle for delicate clothes.

Whirlpool (Kenmore) created a popular design demonstrating the complex mechanisms which could be used to produce different motions from a single motor with the so-called "wig wag" mechanism, which was used for decades until modern controls rendered it obsolete. In the Whirlpool mechanism, a protruding moving piece oscillates in time with the agitation motion. Two solenoids are mounted to this protruding moving piece, with wires attaching them to the timer. During the cycle, the motor operates continuously, and the solenoids on the "wig wag" engage in agitation or spin. Despite the wires controlling the solenoids being subject to abrasion and broken connections due to their constant motion and the solenoids operating in a damp environment where corrosion could damage them, these machines were surprisingly reliable.

====Reversible motor with mode-changing transmission====
Some top-loaders, especially compact apartment-sized washers, use a hybrid mechanism. The motor reverses direction every few seconds, often with a pause between direction changes, to perform the agitation. The spin cycle is accomplished by engaging a clutch in the transmission. A separate motorized pump is generally used to drain this style of machine. These machines could easily be implemented with [[universal motor]]s or more modern DC [[brushless motors]], but older ones tend to use a capacitor-start [[induction motor]] with a pause between reversals of agitation.<ref>W10329932 L-84 Whirlpool vertical modular washer job aid</ref>

===Front-loading===
{{anchor|Frontloader}}
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[[File:WashingMachine, manufactured by ArcticRomania.jpg|thumb|upright|[[Arctic S.A.|Arctic]] BE1200A+ is a front-loading budget model sold in 2008 with {{convert|6|kg|adj=on}} load, LCD indicator, operating up to 1200 RPM.]]
[[File:Drum of a washing machine (Bosch Maxx WFO 2440).jpg|thumb|Modern drum of front-loading washing machine (Bosch Maxx WFO 2440)]]
The front-loading or horizontal-axis clothes washer is the dominant design in Europe and in most parts of the world. In the United States and Canada, most "high-end" washing machines are of this type. In addition, most commercial and industrial clothes washers around the world are of the horizontal-axis design.

This layout mounts the inner drum and outer drum horizontally, and loading is through a door at the front of the machine. The door often but not always contains a transparent window. Agitation is supplied by the back-and-forth rotation of the cylinder and by gravity. The clothes are lifted 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 to 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 repeated dropping and folding action of the tumbling can easily produce large amounts of foam or suds.

Front-loaders control water usage through the [[surface tension]] of water, and the [[capillary action|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 clothes with water.

Compared to top-loading washers, clothing can be packed more tightly in a front loader, up to the full drum volume if using a cotton wash cycle. This is because wet cloth usually fits into a smaller space than dry cloth, and front-loaders can self-regulate the water needed to achieve correct washing and rinsing. However, extreme overloading of front-loading washers pushes fabrics towards the small gap between the loading door and the front of the inner drum, potentially resulting in fabrics lost between the inner drum and outer tub, and in severe cases, tearing of clothing and jamming the motion of the inner drum.

====Mechanical aspects====
Front-loading washers are mechanically simple compared to top-loaders, with the main motor (a [[universal motor]] or [[variable-frequency drive]] 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. The action of a front-loading washing machine is better suited to a motor capable of reversing direction with every reversal of the wash drum; a universal motor is noisier, less efficient, and does not last as long, but is better suited to the task of reversing direction every few seconds. Some models, such as those by [[LG Electronics|LG]], use a motor directly connected to the drum, eliminating the need for a belt and pulley.

However, front-load washers suffer from their own technical challenges due to the horizontal disposition of the drum. 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 with a [[gasket]] to prevent water dripping onto the floor during the wash cycle. This access door is locked shut with an [[interlock|interlocking device]] during the entire wash cycle, since opening the door with the machine in use could result in water gushing onto the floor. If this interlock is broken for any reason, such a machine stops operation, even if this failure happens mid-cycle. In most machines, the interlock is usually doubly redundant to prevent either opening with the drum full of water or being opened during the spin cycle. For front-loaders without viewing windows on the door, it is possible to accidentally pinch the 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 also use a folded flexible [[bellows]] assembly around the door opening to keep clothing contained inside the drum 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 drum near the door and fall down the narrow slot between the outer and inner drums, plugging the drain and possibly jamming rotation of the inner drum. Retrieving lost items from between the outer drum and inner drum can require complete disassembly of the front of the washer and pulling out the entire inner wash drum. Commercial and industrial front-loaders used by businesses (described below) usually do not use the bellows, but instead require all small objects to be placed in a mesh bag to prevent loss near the drum opening.

===Variant and hybrid designs===
[[File:European top washingmachine.jpg|thumb|European top-loader with horizontal-axis rotating drum (2008)]]
<!-- [[File:tvatt.jpg|thumb|European top loader with horizontal axis rotating drum (2001)]] -->

There are many variations of the two general designs. Top-loading machines in [[Asia]] use [[impeller]]s instead of agitators. Impellers are similar to agitators except that they do not have the center post extending up in the middle of the washtub basket.

====Horizontal-axis top-loader====
Some machines which load from the top are otherwise much more similar to front-loading horizontal-axis drum machines. They have a drum rotating around a horizontal axis, as a front-loader, but there is no front door; instead, there is a liftable lid that provides access to the drum, which has a hatch that can be latched shut. Clothes are loaded, the hatch and lid are closed, and the machine operates and spins just like a front loader. These machines are narrower but usually taller than front-loaders, usually have a lower capacity, and are intended for use where only a narrow space is available, as is sometimes the case in Europe. They have incidental advantages: they can be loaded while standing (but force the user to bend down instead of crouching down or sitting to unload); they do not require a perishable rubber bellows seal; and instead of the drum having a single bearing on one side, it has a pair of symmetrical bearings, one on each side, avoiding asymmetrical bearing loading and potentially increasing life.

====Combo washer dryer====
There are also [[combo washer dryer]] machines that combine washing cycles and a full drying cycle in the same drum, eliminating the need to transfer wet clothes from a washer to a dryer machine. In principle, these machines are convenient for overnight cleaning (the combined cycle is considerably longer), but the effective capacity for cleaning larger batches of laundry is drastically reduced. The drying process tends to use much more energy than using two separate devices, because a combo washer dryer not only must dry the clothing but also needs to dry out the wash chamber itself.

These machines are used more where space is at a premium, such as areas of Europe and Japan because they can be fit into small spaces, perform both washing and drying, and many can be operated without dedicated utility connections. In these machines, the washer and dryer functions often have different capacities, with the dryer usually having the lowest capacity.

These combo machines should not be confused with a dryer on top of a washer installation, or with a laundry center, which is a one-piece appliance offering a compromise between a washer-dryer combo and a full washer to the side of the dryer installation or a dryer on top of a washer installation. Laundry centers usually have the dryer on top of the washer, with the controls for both machines being on a single control panel. Often, the controls are simpler than the controls on a washer-dryer combo or a dedicated washer and dryer. Some implementations are patented under [https://patents.google.com/patent/US6343492B1/en?q=D06F37%2f04 US Patent US6343492B1] and [https://patents.google.com/patent/US6363756B1/en?q=D06F37%2f04 US Patent US 6363756B1].

===Comparison===
True front-loading machines, top-loading machines with horizontal-axis drums, and true top-loading vertical-axis machines can be compared on several aspects:

* Efficient cleaning: Front loaders usually use less energy, water, and detergent compared to the best top-loaders.<ref>{{cite web|url=http://www.lanfaxlabs.com.au/washing_machines.htm | title=Laundry Products Research | date=March 2008}}</ref> High-efficiency washers use 20% to 60% of the detergent, water, and energy of "standard" commonly-used top-loader washers. They usually take somewhat longer (20–110 minutes) to wash a load, but are often computer controlled with additional sensors, to adapt the wash cycle to the needs of each load.
* Water usage: Front-loaders usually use less water than top-loading residential clothes washers. Estimates are that front-loaders use from one-third <ref>{{cite web |url=http://housewares.about.com/lw/Home-Garden/Home-improvement-renovation/Top-Loading-vs-Front-Loading-Washers-Which-is-Better-.htm |title=About.com |access-date=2010-10-26 |archive-date=2010-06-14 |archive-url=https://web.archive.org/web/20100614071512/http://housewares.about.com/lw/Home-Garden/Home-improvement-renovation/Top-Loading-vs-Front-Loading-Washers-Which-is-Better-.htm |url-status=dead }}</ref> to one half<ref>{{cite web|url=http://www.consumerenergycenter.org/home/appliances/washers.html | title=Consumer Energy Center}}</ref> as much water as top-loaders.
* Spin-dry effectiveness: Front-loaders (and European horizontal-axis top-loaders and some front-loaders) offer much higher maximum spin speeds of up to 2000&nbsp;[[revolutions per minute|RPM]], although home machines tend to be in the 1000 to 1400&nbsp;RPM range, while top-loaders (with agitators) do not exceed 1140&nbsp;RPM. High-efficiency top-loaders with a wash plate (instead of an agitator) can spin up to 1100&nbsp;RPM, as their center of gravity is lower. Higher spin speeds, along with the diameter of the drum, determine the [[g-force]], and a higher g-force removes more residual water, making clothes dry faster. This also reduces energy consumption if clothes are dried in a [[clothes dryer]].<ref>{{cite web|title=Which Spin Cycle Should I Use?|url=https://www.domex-uk.co.uk/help-advice/which-spin-cycle-should-i-use/|website=Domex Ltd|language=en-GB|access-date=2020-05-01}}</ref>
* Cycle length: Top-loaders have tended to have shorter cycle times, in part because their design has traditionally emphasized simplicity and speed of operation more than resource conservation. It is observed that top-loaders wash the clothes in half the time as compared to a front-load washing machine.
* Wear and abrasion: Top-loaders require an agitator or impeller mechanism to force enough water through clothes to clean them effectively, which greatly increases mechanical wear and tear on fabrics. Front-loaders use paddles in the drum to repeatedly pick up and drop clothes into the water for cleaning; this gentler action causes less wear and tear. The rate of clothes wear can be roughly gauged by the amount of accumulation in a clothes dryer [[lint (material)|lint]] filter, since the lint largely consists of stray fibers detached from textiles during washing and drying.
* Difficult items: Top-loaders may have trouble cleaning large items, such as [[sleeping bag]]s or [[pillow]]s, which tend to float on top of the wash water rather than circulate within it. In addition, vigorous top-loader agitator motions may damage delicate fabrics. Whereas in a front-load washing machine, one can easily wash pillows, shoes, soft toys, and other difficult-to-wash items.
* Noise: Front-loaders tend to operate more quietly than top-loaders because the door seal helps contain noise, and because there is less of a tendency towards imbalance. Top loaders usually need a [[mechanical transmission]] (due to agitators, see above), which can generate more noise than the rubber belt or direct drive found in most front-loaders.
* Compactness: True front-loading machines may be installed underneath counter-height work surfaces. A front-loading washing machine, in a fully fitted kitchen, may even be disguised as a [[kitchen cabinet]]. These models can also be convenient in homes with limited floor area, since the clothes dryer may be installed directly above the washer ("stacked" configuration).
* Water leakage: Top-loading machines are less prone to leakage because simple [[gravity]] reliably keeps water from spilling out the loading door on top. True front-loading machines require a flexible seal or gasket on the front door, and the front door must be locked during operation to prevent opening, lest large amounts of water spill out. This seal may leak and require replacement. However, many current front-loaders use so little water that they can be stopped mid-cycle for the addition or removal of laundry, while keeping the water level in the horizontal tub below the door level. Best practice installations of either type of machine will include a [[floor drain]] or an overflow catch tray with a drain connection, since neither design is immune to leakage or a [[solenoid valve]] getting stuck in the open position.
* Maintenance and reliability: Top-loading washers are more tolerant of maintenance neglect, and may not need a regular "freshening" cycle to clean door seals and bellows. During the spin cycle, a top-loading tub is free to move about inside the cabinet of the machine, using only a lip around the top of the inner basket and outer tub to keep the spinning water and clothing from spraying out over the edge. Therefore, the potentially problematic door-sealing and door-locking mechanisms used by true front-loaders are not needed. On the other hand, top-loaders use mechanical gearboxes that are more vulnerable to wear than simpler front-load motor drives.
* Accessibility and ergonomics: Front-loaders are more convenient for shorter people and those with [[paraplegia]], as the controls are front-mounted and the horizontal drum eliminates the need for standing or climbing. Risers, also referred to as pedestals, often with storage drawers underneath, can be used to raise the door of a true front-loader closer to the user's level. However, if stacked, the dryer controls, if at the top of the dryer, may be too tall for shorter people to conveniently access.
* Initial cost: In countries where top-loaders are popular, front-loaders tend to be more expensive to buy than top-loaders, though their lower operating costs can lead to lower [[total cost of ownership]], especially if energy, detergent, or water are expensive. On the other hand, in countries with a large front-loader user base, top-loaders are usually seen as alternatives and more expensive than basic off-brand front-loaders, although without many differences in [[total cost of ownership]] apart from design-originated ones. In addition, manufacturers have tended to include more advanced features such as internal water heating, automatic dirt sensors, and high-speed emptying on front loaders, although some of these features could be implemented on top loaders.