<P> According to @ Issue: The Journal of Business and Design (vol. 8, no . 1): </P> <P> In his usual style of seeking solutions from unexpected sources, Dyson thought of how a nearby sawmill used a cyclone--a 30 - foot (9.1 m) - high cone that spun dust out of the air by centrifugal force--to expel waste . He reasoned that a vacuum cleaner that could separate dust by cyclonic action and spin it out of the airstream would eliminate the need for both bag and filter . </P> <P> Dyson developed 5,127 prototype designs between 1979 and 1984 . The first prototype vacuum cleaner, a red and blue machine, brought Dyson little success, as he struggled to find a licensee for his machine in the UK and America . Manufacturing companies like Hoover did not want to license the design, probably because the vacuum bag market was worth $500 m so Dyson was a threat to their profits . </P> <P> The only company that expressed interest in the new cyclonic vacuum technology was Dyson's former employer, Rotork . Built by Italian appliance maker Zanussi and sold by Kleeneze through mail order catalogue, the Kleeneze Rotork Cyclon was the first publicly sold vacuum cleaner of Dyson's design . Only about 500 units were sold in 1983 . </P>

When was the first dyson vacuum cleaner invented