(MONEY Magazine) – It's not in an inventor's blood to feel successful. Churn out one idea and there's another demanding its turn. James Dyson, 57, whose vacuum cleaners are the best-selling models in the U.K. (and who's now hoping to clean up in the U.S.), says, "I've done a great deal, but I don't know if I've 'made it.' I'm already on to the next thing."

Dyson had several inventions on the market when he came up with a vacuum cleaner that doesn't get clogged with dust and lose suction. But none had brought financial success, so he wasn't surprised that he couldn't find a backer: "Maybe it's perverse, but every time someone turned me down, I became more determined." He finally snared a loan for $1.5 million in 1992, enough to produce a prototype. "I've always thought borrowing was a good use of money." --J.C.