The problem, according to Dyson, is that clothes in conventional, single-drum, tumble-action washers move in a simple “drop-and-flop” pattern that fails to flex the fabric and open the weave to the detergent solution. With insufficient mechanical energy being put into the clothes, the tumbling washers are overly dependent on the other two legs of the cleaning triad—thermal energy from the hot water and chemical energy from the detergent.
Not wanting to fall into the same trap with their new washer, Dyson engineers looked for ways to replicate the effects of hand washing, something that would better manipulate the fabric. Pursuing that objective led to the development of the Contrarotator, a front-loading, horizontal-axis washer with two drums rotating in opposite directions during the wash cycle. The twin tumbling action makes the clothes more active, moving them around in an infinitely variable pattern.
The dual-drum approach is implemented by use of a full-depth outer drum whose back half is flared. A half-depth inner drum fits within this flared section and turns in the opposite direction. Both drums are geared and powered from the back. A polymer circumferential bearing separates the drums and prevents fabric edges from getting caught between them.
The two drums counter-rotate at the same speed in relation to each other, but that speed varies by wash load. For example, the drums counter-rotate at 52 RPM on the cotton cycle but only at 10 RPM for the woolen cycle. For spin cycle, the drive gears shift behind the drums, enabling the two drums to spin together in the same direction at 1,400 RPM.
The 1,400 RPM is lower than the 1,600 RPM spin speeds used on conventional single-drum front-loading washers, however, Dyson says that the 50 percent larger circumference on its double-drums increases the centrifugal force which drives water out and allows it to achieve the same water extraction ratings as competitors. Using smaller, but more numerous perforations in the drums also helps. The Controrotator drums have 4,923 perforations, compared to only 945 perforations for a market-leading, single-drum competitor, according to Dyson.
Greater capacity is one benefit afforded by the new machine. The cubic volume within the double-drum arrangement is 78 liters, which Dyson says gives a 60 percent greater wash load capacity than competitive machines.
But the most important advantage coming from the dual-drum arrangement is improved cleaning performance. Dyson says the improved fabric flexing provided by the counter-rotating drums causes soil to be released more effectively and more quickly from clothes, placing the AAA- rated* Contrarotator ahead of its competitors in both cleanliness and throughput. (Competitors being those companies producing AAA-rated machines in the U.K. at the time of the tests.)
Dyson says the Controrotator provides a throughput of 13 lbs. of clothes per hour (at 40°C/104°F), vs. 5.5 lbs. an hour for the next best competitor. The higher throughput can, therefore, halve the time a consumer spends on laundry.
While washing performance was the No.1 target for Contrarotator project, Dyson engineers also designed a number of other innovative features into the new machine to further separate from others on the market.
- Specially designed, tapered paddles mounted in the drums that increase fabric movement and help move clothes from front to back.
- A double-door system where the inner door is fixed to the drum instead of the cabinet, thus eliminating the possibility of clothing getting trapped between the door and seal.
- Tub entry where clothes glide over a smooth plastic lip instead of a rubber bellows seal.
- A coin and button trap that can be accessed from the front of the machine.
- Retractable Rollerjack™ handle underneath the front of the machine pulls out to aid in maneuvering the machine into position.
The Contrarotator also uses microprocessor-based controls that permit user-customized wash programs, provide an imbalance detection and correction routine, and contain a fault analysis program.
The first version of the Contrarotator, the CR01, was launched in the UK in December 2000 with three color options: silver, blue and purple. The machine will be rolled out into a number of international markets around June of 2001. Eventually, Dyson plans to introduce the machine to the North American market as well.
* The AAA classification refers to an EEC requirement and is based on the manufacturer’s declaration of the IEC 60456 performance test. The first A refers to wash performance, the second A relates to energy efficiency, and the third A represents spin performance (water extraction).