Rarely does a day go by when Luc Deprez is not thinking of a way to perfect his brainchild, the ride-on suitcase.

First, he modified the motor to run on a battery instead of gasoline. Then he replaced the steering wheel with a microphone so it could be voice-operated.On Wednesday, Deprez knelt beside his masterpiece, waving his hands along the sides to show where he could one day install a solar panel.

The ride-on suitcase was among 2,000 gizmos on display at what is billed as the world's largest trade show for inventors. Products ranged from the ultra-high-tech - such as the "Intelligent Diaper," which beeps when a change is warranted - to low-tech creations like a rack for draining the last splats from a ketchup bottle.

Like a kid taking a go-cart out for a spin, Deprez zoomed through the aisles, grinning as other exhibitors scowled over the media attention he was getting. Some onlookers who tried to work the suitcase had trouble.

"You have to practice with it a little bit," said Deprez's brother-in-law, Jozef Denoyelle, who acted as an interpreter.

Deprez, who is Belgian, argued briefly with Denoyelle over how much room is available for clothes in the $500 suitcase, which appeared to be overwhelmed by the motor when it was opened.

Reluctantly, Denoyelle interpreted Deprez's estimate as 80 percent, then quickly pointed out that the motor could be made smaller.

The convention has been an annual event near Pittsburgh since 1982. In a warehouse-size center jammed with displays, exhibitors from around the country and abroad fairly outdid themselves in a quest to get media attention - and free advertising.

Matt Moolman of Johannesburg, South Africa, wrapped his hand in his patented fireproof cloth and gel, then amiably chatted with a reporter as he held it in a blowtorch flame.

"It can remove an enormous amount of heat and dissipate it," he said, keeping up the salesman's patter as the blue flame licked at his hand.