Editing Washing machine (section)

====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.