The design classic born out of housework

In 1979 James Dyson was doing the chores at home. Task one: vacuum the living room. He set to work with a Hoover Junior machine, which used the technology that was standard in vacuum cleaners for decades: the air was sucked in through the nozzle and the dirt and dust trapped in a cloth bag between the intake and exhaust.

In 1979 James Dyson was doing the chores at home. Task one: vacuum the living room. He set to work with a Hoover Junior machine, which used the technology that was standard in vacuum cleaners for decades: the air was sucked in through the nozzle and the dirt and dust trapped in a cloth bag between the intake and exhaust.

Mr Dyson later commented how he was "struck by the inefficiency" of the system. The more he did the less it sucked. He tried a filter bag, with a finer mesh; that was no good either.

His inventor's juices were flowing. He had already been inventing things for 18 years, beginning with his "Sea Truck", launched while he was at the Royal College of Art. The Dyson household was going to be cleaned - but not Hoover's way.

"At the time we were installing a powder coating plant for our 'ballbarrows' [a wheelbarrow with a ball rather than a wheel]. To capture all the black dust which didn't get sprayed on we had an industrial cyclone, about 20ft tall and made of steel."

Cyclone towers are a well-known industrial filtering system: air is dragged into a tower and whirled round, at up to the speed of sound. Dust particles, being heavier, are forced to the edge where they can be collected, and the clean air extracted from near the centre. The principle is like a fairground motorcyclist whirling around a wall of death: the dust is forced against the outer wall of the cyclone, and though there are other forces (gravity in the wall of death; upward suction in the Dyson), they are less than that on the wall. So the dust, and the motorcyclist, stay put until the power goes off.

"I wondered why nobody used cyclones in vacuum cleaners," recalled Mr Dyson yesterday. He set to work building one and soon found out. It was a complex job to shrink an industrial design. In the first version, he replaced the bag in his Hoover Junior with a miniature cardboard cyclone, which he made airtight with tape.

He applied for a patent - entitled "Vacuum Cleaning Appliance" - in 1980. The final product took another four years and 5,127 prototypes, and illustrated the frustrations of the patent process: "I made a 1ft high cyclone that was far more effective than any other. But you can't patent an improvement on an existing technology."

If his design had simply had one cyclone, like those industrial ones, he could not have patented that. But household vacuuming is a different task from industry: he discovered that two cyclones were needed, one to separate out the larger items - "cigarette ends, dog hairs" - and the second to catch the smaller particles.

However, the vacuum cleaner industry was not interested. Wedded to bags - often a profitable replacement item - there was no incentive to change. "Dirt collection by another means [than bags] was regarded as heresy or folly - or both," noted the judge yesterday. That has changed, perhaps for ever.