* Dyson The Dual Cyclone dispenses with the inefficient dust bag used by conventional vacuum cleaners. Instead, dusty air is drawn into the outer cyclone which spins out large debris and 90% of fine dust. The air is then pulled through a shroud filter, which ensures that larger, lighter particles, such as pet hair, are retained in the outer cyclone. The air then passes into the inner cyclone, where `the flow is reversed, accelerated and subjected to forces 100,000 times those of gravity’. This removes particles, says Dyson, as small as 0.1 micron. Two more filtration stages follow before the suction air is returned to the atmosphere.
* Hoover Using fluid engineering specialist BHR to help it come up with its bagless design, the technology was originally designed for the oil and gas industry, Hoover claims, for applications like separating sand from gas. The process has three stages. Air laden with dust is drawn into the first chamber in which `scraps of litter and most of the dirt are spun out down the sides of the waste container’. The air passes through a screen and into the second stage, an involute vortex chamber, where `the air-speed increases dramatically to swirl out the dust’. This part of the flow is then pulled down into the third stage, `a high-efficiency vortex, which spins the air clean’.
Hoover claims the advantage of its design is that it eliminates filters. Dyson says its DC04 model has double the Hoover’s suction power and emits cleaner air. But does Hoover’s design infringe Dyson’s patent? No doubt a wealth of technical information and expertise will be fielded by both sides to persuade the High Court of the merits of their claims.
You decide! Visit www.dyson.com/technology www.hoover.co.uk/vortex